psychophysiology Archives

Under the Skin: Digging Deeper into the Physiology of Fear

From the thrill of cinematic jump scares to debilitating phobias that can turn daily life for some into a waking nightmare, our sense of fear can feel like both a blessing and a curse. Fear is one of the most fundamental human emotions, serving as a necessary safeguard for recognizing and responding to danger. Despite its primal origins, the mechanisms of fear remain complex. For decades, psychophysiologists have studied fear using measures such as the startle reflex and skin conductance, building a deep understanding of how the body reacts to threats. Today, however, researchers are beginning to look beyond these traditional markers. Technologies such as virtual reality (VR) expand how researchers can stimulate the fear response. At the same time, a broad range of signals and techniques can measure not only the body’s autonomic responses, but also how people allocate attention to threats and how the brain processes fear-related information.

One reason fear remains such a compelling topic is that it sits at the intersection of cognition, emotion, memory, and physiology. Fear responses can be observed through changes in sweating, heart activity, breathing patterns, pupil size, neural activity, and even social behavior. As researchers seek to gain a better understanding of anxiety disorders, phobias, post-traumatic stress disorder (PTSD), and related conditions, they increasingly rely on multiple synchronized signals to capture a more complete picture of how fear is learned, remembered, and generalized.

Among the most widely used measures is electrodermal activity (EDA), often recorded as skin conductance response (SCR), which reflects changes in sympathetic nervous system arousal. More recently, eye tracking and pupillometry have emerged as valuable tools for measuring vigilance and attention, while functional near-infrared spectroscopy (fNIRS) has enabled monitoring of changes in cortical activity during fear-related tasks in more naturalistic settings. Together, these approaches help researchers move beyond viewing fear as a single physiological reaction and toward understanding it as a coordinated brain-body process.

A team of researchers at South China Normal University in China explored how the duration of memory retrieval influences the reconsolidation and extinction of fear memories. Using a four-day fear-conditioning paradigm, participants were conditioned to associate visual cues with mild electric shocks. Simultaneously, skin conductance responses were recorded using an MP36 running Biopac Student Lab System. The experiment was designed and implemented with E-Prime stimulus presentation software. The team found that briefly reactivating a fear memory before training participants to view the stimulus as safe was most effective at preventing the fear from returning. Longer periods of memory reactivation produced weaker effects. The study highlights how electrodermal activity can reveal subtle changes in fear-memory processing and may ultimately contribute to improved behavioral interventions for anxiety-related disorders.

A study conducted at the University of Würzburg in Germany examined how anxiety sensitivity influences attention and memory during threat and safety learning. Participants learned associations between neutral faces and aversive outcomes while researchers recorded both electroencephalography (EEG) and pupil diameter. Pupillometry data were acquired using a Tobii eye tracker, allowing researchers to measure moment-to-moment changes in attention. Individuals with higher anxiety sensitivity showed larger pupil responses and enhanced neural markers of attention when viewing both threatening and safe cues, reflecting a generalized pattern of hypervigilance. Interestingly, this heightened attentional engagement did not translate into better memory performance. The findings suggest that pupillometry provides a valuable window into how anxious individuals process potential threats and may help researchers better understand mechanisms underlying pathological anxiety.

Another perspective on fear comes from research at Sichuan Normal University in China, where investigators look at how trait anxiety influences observational fear learning. Unlike traditional conditioning studies, participants learned about danger by watching another person experience threat-related events. Researchers measured skin conductance using a BioNomadix wireless EDA plus data acquisition and analysis system and monitored prefrontal brain activity using fNIRS. The study found that individuals with high trait anxiety exhibited stronger physiological fear responses and increased medial prefrontal cortex activation, even when observing threats indirectly. The work demonstrates that fear can be acquired socially and that neural measures such as fNIRS can reveal aspects of fear processing that are not readily captured by autonomic measures alone. These findings may have important implications for understanding how fear and anxiety spread through social environments and how vulnerability to anxiety disorders develops.

These studies illustrate how fear research leverages multimodal approaches to incorporate multiple physiological perspectives. Skin conductance continues to provide valuable information about autonomic arousal, while pupillometry reveals how attention is divided between threat and safety cues, and fNIRS offers insight into the neural processes involved in fear learning and regulation. As multimodal research platforms become increasingly accessible, researchers are gaining unprecedented insight into how fear is acquired, maintained, and modified. By combining signals from the body, the eyes, and the brain, modern psychophysiology is shining a light on the shadowy labyrinth that is one of humanity’s most powerful and important emotions. To learn more about how to construct a fear stimulation lab for your next fear-conditioning research project, check out our webinar on the subject.

If you are planning a multimodal fear conditioning study, our staff can help identify the right equipment and software for stimulus presentation and data recording and analysis.

Muscles in Motion: Electromyography in Physiological Research

When we think about the human muscular system, movement often comes to mind. Activities such as running, lifting, and maintaining posture all rely on coordinated skeletal muscle activity, while cardiac muscle drives circulation and smooth muscle supports essential functions like digestion. Yet muscles do more than move us from point A to B; they also reflect what is happening inside the body. Patterns of muscle activation can reveal information about physical effort, fatigue, coordination, and recovery, as well as emotional expression, stress, and cognitive engagement. Electromyography (EMG) is a widely used technique for measuring the electrical signals generated by muscles during contraction, providing researchers with a direct and objective means to study both physiological function and the links among the nervous system, behavior, and mental state. By capturing muscle activity that may be too subtle to observe visually, EMG enables precise investigation of processes ranging from motor control and performance to emotional and stress-related responses.

There are several types of EMG, each suited to different research needs. Surface EMG (sEMG) uses small sensors placed on the skin to detect activity from nearby muscles and is the most common approach in behavioral and human performance studies. Intramuscular EMG involves inserting a fine-needle electrode directly into a muscle to record activity from specific muscle fibers, often used in clinical or specialized research settings. Facial EMG (fEMG), a form of surface EMG, focuses on facial muscles. By measuring muscle activity associated with smiling or frowning, fEMG allows researchers to study emotional responses, even when those responses are subtle or not consciously expressed.

One of the key strengths of EMG is its ease of integration with other physiological measurements. In many studies, EMG is recorded alongside electrocardiography (ECG), which measures heart activity; electroencephalography (EEG), which records electrical activity in the brain; functional near-infrared spectroscopy (fNIRS), which tracks changes in brain oxygenation; and eye tracking, which monitors visual attention and gaze patterns. By synchronizing these signals in time, researchers can better understand how different systems in the body work together. For example, combining EMG with EEG can reveal how brain activity leads to muscle movement, while pairing EMG with ECG can show how physical effort relates to heart responses during stress or exercise. This multimodal approach is central to advancing research in areas such as emotion, cognition, and human performance.

EMG also has important real-world applications. In rehabilitation, it helps clinicians monitor muscle recovery after injury. In ergonomics, it provides objective data about muscle strain in the workplace. In sports science, EMG helps optimize training and performance by identifying how and when muscles are activated. Increasingly, EMG is also used in human–machine interfaces, such as systems that allow people to control prosthetic limbs using their muscle signals. Its ability to detect fine-grained changes in muscle activity makes EMG a valuable tool across both research and applied settings.

Best practices for EMG data quality begin with careful electrode placement and attention to potential sources of noise. For sEMG and fEMG, electrodes should be placed over the “belly” of the target muscle, aligned with the muscle fibers, and spaced consistently to capture clean, interpretable signals. Gently cleaning the skin and, when appropriate, lightly abrading the surface helps reduce impedance and improve signal quality. In fEMG studies, precise and repeatable placement over well-defined facial muscles is critical, as these muscles are small and closely spaced. To minimize noise and artifacts, researchers should secure electrodes and cables to prevent movement, ask participants to limit unnecessary body motion, and ensure proper grounding of the recording system. Electrical interference from nearby equipment, power lines, or poor cable management can also contaminate EMG signals, so shielded cables and a controlled recording environment are recommended. Finally, synchronizing EMG with other physiological signals using a common acquisition system helps prevent timing errors and reduces the need for later corrections, resulting in cleaner data and more reliable conclusions.

Recent studies demonstrate how EMG continues to expand into new and innovative areas. In a study published in Results in Engineering, a team of researchers from China developed a low-computational method for recognizing hand gestures from EMG signals to improve prosthetic device control. The researchers extracted key features from EMG recordings and used a lightweight machine-learning model, a multilayer perceptron (MLP), to classify gestures in real time. EMG data were collected using a four-channel BIOPAC data acquisition system running Biopac Student Lab (BSL) software. Surface Ag/AgCl electrodes were placed on four forearm muscles to capture relevant muscular activity. The study showed that accurate gesture recognition can be achieved without heavy computational requirements, making the system more practical for everyday use. This work highlights how EMG can support the development of more responsive, accessible assistive technologies.

Another study, conducted by a team of researchers from Mahidol University in Thailand and presented in the Institute of Electrical and Electronics Engineers (IEEE) proceedings, explored how combining EMG with motion sensors can improve ergonomic assessments. Focusing on occupational health, the study integrated surface EMG with data from an inertial measurement unit (IMU), a sensor that tracks movement and orientation. The researchers used the IMU to calculate Rapid Upper Limb Assessment (RULA) scores—a common method for evaluating postural risk—while EMG data collected via a BIOPAC four-channel research system provided insight into muscle activity. By combining these measures, the team found that posture alone did not always reflect actual muscle strain. The inclusion of EMG revealed additional muscle stress that might otherwise go unnoticed, suggesting that multimodal approaches can lead to more accurate workplace assessments and better injury-prevention strategies.

Researchers from Louisiana State University and the Pennington Biomedical Research Center in Baton Rouge, Louisiana, examined how training experience influences muscle activation and fatigue during resistance exercise performed with and without blood flow restriction (BFR) in young men. The study, published in Physiological Reports, compared trained and untrained participants while they completed knee extension exercises under low-, medium-, and high-load conditions. The team used sEMG to measure muscle excitation and total muscle activation in the vastus lateralis, with participants fitted with a portable BIOPAC BioNomadix Wireless EMG system. EMG signals were sampled at 2000 Hz and analyzed using a data acquisition system with AcqKnowledge software, allowing the researchers to quantify both peak muscle excitation and overall activation across repetitions. The results showed that low-load exercise with blood flow restriction produced lower peak muscle excitation but substantially greater total muscle activation compared to traditional high-load exercise, regardless of training status. These findings suggest that low-load BFR training may provide an effective alternative for stimulating muscle adaptations while reducing mechanical stress, with potential applications in rehabilitation and strength training programs.

Taken together, these examples illustrate the versatility and effectiveness of EMG in neuroscience, psychophysiological research, and beyond. Whether used to study emotion, improve physical training and workplace safety, or develop assistive technologies, EMG provides a direct link between muscle activity and human behavior. When combined with other physiological measures, it offers a more comprehensive understanding of how the brain and body interact. As research tools and techniques continue to advance, EMG will remain an essential method for exploring brain-body connections. For additional information on how to design studies around EMG, best practices for gathering EMG data, and how to integrate EMG with other signals, check out our webinar on EMG acquisition and analysis.

If EMG will be part of your next physiological or psychophysiological research project, reach out to our knowledgeable staff, who are standing by to help you with each stage of the planning and design process.

Virtual Phobia: How VR is Transforming Anxiety and Fear Research

“Do the thing you fear and the death of fear is certain.”

These words by American poet and philosopher Ralph Waldo Emerson assert a head-on approach to overcoming life’s anxieties and phobias. It’s a strategy backed by the latest research methodology, which, thanks to technology, can leverage the relative safety of virtual environments to study how participants react to and manage anxiety.

Anxiety disorders are among the most prevalent mental health conditions and are often maintained through avoidance of fear‑provoking situations. A cornerstone of evidence‑based treatment is exposure therapy, in which individuals gradually and safely confront feared experiences to reduce anxiety over time. In recent decades, virtual reality (VR) has emerged as an effective way to deliver exposure therapy and to study anxiety under controlled conditions. Virtual reality exposure therapy (VRET) uses immersive, computer‑generated environments to recreate anxiety‑triggering situations, such as public speaking, social interaction, or medical procedures, while allowing researchers and clinicians to control intensity, pacing, and repetition.

Research shows that VRET can be as effective as traditional, real‑world exposure for many anxiety‑related conditions, including specific phobias, social anxiety, panic disorder, and symptoms of post‑traumatic stress disorder (PTSD). One of VR’s key advantages is its balance between realism and experimental control. Environments can be standardized across participants, exposure levels can be adjusted in small steps, and scenarios can be repeated across sessions without the logistical challenges of invivo exposure. At the same time, well‑designed VR experiences reliably evoke emotional and stress responses, making them valuable for both treatment and research.

The scientific impact of VR is amplified when immersive environments are combined with multimodal psychophysiological measurements—such as electrocardiography (ECG), electroencephalography (EEG), functional near‑infrared spectroscopy (fNIRS), respiration, electrodermal activity (EDA), and eye tracking. In multimodal studies, researchers gain a deeper, objective understanding of how the brain and body respond to emotional challenges. By synchronizing VR events with physiological data, researchers can observe how the body responds moment by moment as fear is triggered, maintained, and eventually reduced.

Researchers at the University of Cyprus investigated whether a single session of VR exposure could meaningfully reduce public speaking anxiety in university students. Participants were placed in a virtual auditorium and asked to give a speech in front of realistic virtual audiences. The researchers could adjust audience size and behavior, allowing them to gradually increase the social challenge while maintaining full experimental control. To capture objective stress responses, heart activity was recorded using a Lead I electrocardiogram configuration, with two disposable silver/silver‑chloride electrodes placed on the forearms. Signals were amplified with a BIOPAC ECG100C bio‑amplifier, acquired using a MP data acquisition system with AcqKnowledge software for recording and analysis. This setup enabled precise measurement of heart rate and heart rate variability (HRV) throughout the task. The virtual environment was created using the Vizard Virtual Reality Toolkit, which was integrated with the BIOPAC system so that physiological data could be synchronized with key moments in the VR experience, such as the start of the speech. Results showed significant reductions in both self‑reported anxiety and physiological arousal following a single VR exposure session, demonstrating how VR and physiological monitoring can be combined to assess rapid emotional change.

Researchers at the University of Macau examined how social rewards and emotional cues influence anxiety during interpersonal interaction. Participants engaged in a virtual reality social interaction game designed to mimic real social exchanges while allowing researchers to control feedback and outcomes. During the task, heart activity was recorded using ECG with an MP data acquisition system. By synchronizing physiological data with events in the virtual environment, the research team could examine how anxiety‑related responses evolved as social interactions unfolded. The findings suggested that anxiety responses were more strongly related to sensitivity to others’ emotional cues than to reward outcomes themselves. This study highlights how immersive VR combined with synchronized physiological recording can provide insight into the subtle emotional dynamics of social anxiety, processes that are difficult to capture using self‑report measures alone.

In a multi‑institutional effort led by researchers at the University of Toledo, researchers developed a study protocol to better understand how dental fear develops and how early exposure might help prevent it. The study uses a virtual reality dental clinic to expose participants to dental‑related sights and sounds across multiple sessions and contexts. The virtual environment was programmed using Vizard software, and participants interacted with it using an HTC Vive Pro headset and handheld controllers, allowing natural movement and exploration. Skin conductance responses (SCR) were recorded using a BIOPAC MP system paired with a wireless BioNomadix EDA transmitter, enabling participants to move freely while skin conductance and other signals are collected. This wireless, immersive setup is especially well suited for fear‑learning research, where comfort and natural movement are critical. Although the publication focuses on study design rather than completed outcomes, it demonstrates how VR combined with physiological monitoring can support translational research aimed at understanding and preventing the development of fears and anxiety.

These studies show how VR and synchronized physiological measurement are expanding the study of anxiety, stress, and fear. VR provides immersive, repeatable experiences that reflect real‑world challenges, while physiological signals reveal how the body responds beneath conscious awareness. For additional information on how to integrate VR into multimodal research, visit our Webinar page for instructive trainings on this topic and others.

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Healing Hands: EDA and Affective Touch

“Nothing eases suffering like human touch.” — Bobby Fischer

The gentle caress of a mother to her child. A reassuring pat on the shoulder from a friend. The touch of another human is one of the first forms of communication we experience in life, preceding the development of spoken language. Touch can have a remarkable effect on our emotional, psychological, and physiological states. It shapes our relationships with others and helps us build social connections.

The positive effects of touch are primarily associated with affective touch, characterized by comforting, caress-like stroking that activates C-tactile afferent (CT-afferent) neurons in the skin of mammals (including humans). Affective touch has attracted the interest of researchers seeking to decode how the sympathetic nervous system confronts and manages a variety of challenges, including pain regulation, stress management, and social interactions. The subject has drawn attention in the study of neurodevelopmental disorders, such as Autism Spectrum Disorders (ASD), where it is playing an essential role in understanding the sensory and social challenges facing individuals with atypical neurocognitive function.

While studies on touch, and affective touch specifically, utilize a range of physiological signals to gather data, electrodermal activity (EDA) has proven particularly useful in this area. Also referred to as Galvanic Skin Response (GSR), EDA provides a direct window into the sympathetic nervous system, which is responsible for emotional or affect-related arousal. When someone experiences pleasant or meaningful touch (e.g., a gentle stroke or supportive hand), the brain triggers subtle changes in sweat gland activity manifested as shifts in skin conductance. These changes occur when people aren’t fully aware of their emotional response. This makes EDA a sensitive, objective marker of how the body reacts to social and tactile experiences. In studies of affective touch, researchers track EDA to see whether a touch feels calming, engaging, or stressful, and how these responses differ across individuals or clinical groups such as autistic youth. Because EDA reflects genuine physiological arousal tied to emotional processing, it helps scientists understand the underlying autonomic mechanisms that shape how we experience social touch.

Researchers at the University of Tours in France examined how children with ASD respond to gentle, affective touch to determine whether they exhibit physiological patterns that differ from those of their neurotypical peers under the same conditions. The team measured multiple aspects of the autonomic nervous system, including EDA and electrocardiogram (ECG). These signals were collected using a BIOPAC MP36 data acquisition and analysis system to capture subtle changes in sympathetic arousal. Researchers collected EDA data using two 8 mm Ag/AgCl cup electrodes placed on the second phalanges of the index and middle fingers of the right hand. ECG was collected via two disposable vinyl electrodes placed on the sternum and on the right shoulder. The study found that autistic children exhibited atypical EDA responses, showing either blunted or inconsistent autonomic reactions relative to controls, even when their outward behavior appeared typical. These results suggest that affective touch may not regulate internal arousal in autistic children the same way it does in others, providing an essential insight for therapies and sensory-based interventions that rely on touch.

In a similar study, a team from the University of Turin in Italy explored how autistic adults process affective touch by comparing their subjective ratings of pleasantness with their physiological responses. The researchers used a BIOPAC data acquisition research system with an EDA amplifier module to record EDA. At the same time, participants received gentle, slow stroking intended to activate the brain’s affective touch pathways. The goal was to determine whether autistic adults show a mismatch between what they say they feel and how their bodies respond. The findings revealed an apparent dissociation. While autistic participants often rated the touch similarly to neurotypical participants, their EDA responses differed significantly, indicating altered sympathetic arousal. This physiological-subjective mismatch provides compelling evidence that affective touch is processed differently in ASD, which may help explain challenges with social touch and sensory integration in everyday interactions.

Researchers from the University of Liverpool and Manchester Metropolitan University examined how brief, naturalistic social touch alters brain activity, autonomic physiology, and emotion recognition performance. Although this multimodal study did not focus on an autism-only sample, it is relevant to social-touch research more broadly and provides methodological examples that apply to ASD studies. To capture changes in prefrontal cortex function, the team employed a BIOPAC fNIRS imager system, with signals sent to a data acquisition unit. Further analysis of fNIRS signals was handled via fNIRS visualization software. Both EDA and photoplethysmography (PPG) were recorded at 2 kHz, using shielded Ag/AgCl electrodes on the index and fourth fingers and a PPG sensor on the middle finger, and were acquired and analyzed in AcqKnowledge. The results showed that social touch increased prefrontal activation, modulated cardiac and vascular dynamics captured via PPG, and produced measurable changes in sympathetic arousal, as indexed by EDA. Participants also demonstrated improved emotion-recognition accuracy following touch. Together, these findings suggest that social touch engages coordinated central and peripheral systems in ways that may support social cognition and emotional understanding.

These are just a few examples of how EDA is being used in research into affective touch. For additional information on integrating EDA in your study, see our multiple webinars on the subject.

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Brain and Body: SPA-fNIRS Solves Physiological Signal Noise

Functional near-infrared spectroscopy (fNIRS) offers researchers a powerful noninvasive tool for studying brain activity by measuring changes in blood oxygen levels. These changes reflect how various brain regions respond to stimuli such as tasks that involve thinking, emotion, movement, and social interaction. These are often in natural, real-world settings that are not possible with other brain imaging methods. However, fNIRS is not without its own limitations. Systemic fluctuations in the body, such as breathing patterns, cardiovascular changes, and autonomic responses, can result in signal noise that is misinterpreted as brain activity by traditional fNIRS. The solution: a visit to the SPA.

Systemic Physiology Augmented fNIRS (SPA-fNIRS) is an advanced approach to fNIRS that goes beyond measuring local changes in cerebral oxygenation. While standard fNIRS measures cortical hemodynamics by tracking oxygenated (HbO) and deoxygenated (HbR) hemoglobin, noise originating from systemic physiological changes can corrupt those signals. Combining data from both neural and systemic physiological signals, SPA-fNIRS provides researchers with a more diverse and accurate view of how the brain and body interact in real time.

The method is being applied across various fields, including psychophysiology, cognitive neuroscience, exercise physiology, mental health, and human performance research. Studies have utilized SPA-fNIRS to investigate a range of topics, including meditation and emotional regulation, movement control, and social interaction. The broader goal is to move beyond studying the brain in isolation and to understand it as part of an integrated mind-body system. This holistic view is transforming how scientists interpret brain-function data, opening new paths for applied research in education, rehabilitation, and human-machine interface design.

Researchers in India investigated the impact of a traditional sound-based meditation technique, known as the Mind-Sound Resonance Technique (MSRT), on both brain and heart activity. Using fNIRS to track changes in oxygen levels in the prefrontal cortex, and a BIOPAC data acquisition and analysis system with AcqKnowledge software to record and analyze heart rate variability (HRV), the study employed a SPA-fNIRS design, integrating neural and physiological data in a single, synchronized dataset. HRV analysis allowed the researchers to quantify shifts in autonomic balance during and after meditation. The results showed increased oxygenation in the right prefrontal cortex and enhanced low-frequency HRV components, reflecting greater parasympathetic regulation. Together, these findings suggest that sound-based meditation not only improves brain oxygenation but also promotes calmer, more balanced heart-brain dynamics, illustrating how SPA-fNIRS methods can reveal the comprehensive physiological impact of mindfulness practices.

In her doctoral research at the Université de Lille in France, neuroscientist Aurore Guérin examined how the brain controls movement speed using a multimodal combination of fNIRS and physiological data recording systems. Participants performed repetitive arm movements at fast, natural, and slow tempos. At the same time, the study captured oxygenation in the prefrontal and motor cortices using fNIRS, alongside heart rate and respiration signals collected with a BIOPAC data acquisition system. A respiratory effort transducer measured breathing patterns, while a BioNomadix ECG module recorded cardiac activity for HRV analysis. All physiological signals were synchronized and analyzed in AcqKnowledge software, allowing the team to identify and remove systemic influences (e.g., heartbeat and breathing rhythms) from the fNIRS signals, following a SPA-fNIRS approach. The results revealed that faster movements primarily engaged motor regions, while slower, more deliberate pacing resulted in higher prefrontal activation, reflecting greater cognitive control. By integrating physiological monitoring with fNIRS, the study provided a clearer picture of how the brain and body coordinate timing and control during movement.

These studies illustrate how SPA-fNIRS is reshaping the way scientists investigate the interaction between brain and body. By combining neural and physiological data in a single synchronized system, researchers can separate brain activity from systemic noise and uncover the interplay between cognition, emotion, and autonomic regulation. For more information on this topic, watch our webinar on Multimodal SPA-fNIRS and check our our latest multimoldal fNIRS research products.

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Boom! Pow! Clang! Exploring Stress Resilience with Startle Response and PPI

We have all felt that electrical jolt that comes with hearing a sudden, unexpected loud noise—the clang of a dropped cooking pan, the blast of a car horn, or the pop of a balloon. The reaction is instantaneous and nearly uncontrollable as muscles tense, eyes blink, pupils dilate, and one’s heart seems to leap from the chest. The startle response—a rapid, automatic reaction to sudden stimuli like loud noises—has a practical purpose, helping protect us from outside threats. It can also pose a danger if the response occurs while engaging in precision activities, such as driving a vehicle or operating machinery.

Within the psychophysiological field, the startle response can reveal how our brains and bodies process stress, attention, and emotional regulation. In pursuit of ways to mitigate its detrimental effects, researchers often study this reflex alongside prepulse inhibition (PPI). In this latter process, a weaker sound presented just before the startling noise reduces the strength of the response. To capture data when studying these phenomena, scientists use physiological signals such as electromyography (EMG) to measure the tiny muscle contractions around the eye during a blink, electrocardiography (ECG) for heart rate changes, electrodermal activity (EDA) for skin conductance, and respiration to track stress responses. In addition, researchers often pair these physiological measures with brain imaging techniques, like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG), as well as cognitive tasks to build a complete picture of how startle responses connect with brain function and behavior.

Studies of startle response and PPI intersect with a wide range of fields, from neuroscience and psychiatry to aviation, defense, and occupational health. Clinical investigations of altered startle and PPI patterns are helping scientists uncover biomarkers of vulnerability or resilience. These studies are providing new insight into potential treatments for conditions like schizophrenia, PTSD, anxiety, and neurodegenerative disorders.

In applied contexts, like pilot training or high-stress professions, startle measures are used to understand how sudden stress impacts performance and decision-making. A study conducted by researchers at the University of Zagreb in Croatia with U.S. partners aimed to determine whether stress resilience markers, including startle response and PPI, could predict pilot performance under sudden startle events. Seventeen military pilot cadets completed baseline testing of physiological and cognitive features—including startle reflex habituation, PPI, heart rate variability (HRV), and multitasking ability—followed by flight simulator sessions with induced startle events. Physiological signals such as ECG, EMG (eye-blink startle reflex), respiration, and EDA were recorded via their respective BIOPAC amplifiers connected to a data acquisition and analysis system. Regression modeling showed that startle habituation, autonomic recovery, and cognitive task performance provided an accurate prediction of flight performance. The findings suggest that psychophysiological measures can help identify pilots who are more resistant to startle-induced performance degradation. Such insights could offer practical applications in pilot screening, training design, and aviation safety.

A team of Spanish researchers wanted to see how short-term (acute) stress affects both PPI and higher-level thinking (working memory) in healthy young adults. They used the Maastricht Acute Stress Test (MAST) to induce stress in one group, while another group did a non-stressful control task. After this, all participants heard loud noises that triggered the eye-blink startle response. In some trials, a prepulse immediately preceded the loud noise, which typically reduces the blink reflex. The startle (eye-blink) was measured from the orbicularis oculi muscle using BIOPAC Ag/AgCl electrodes connected to an Electromyography amplifier that fed data to a data acquisition system running AcqKnowledge software. This allowed the researchers to precisely record the intensity of a blink and the degree to which prepulse inhibited it. The team also tested working memory using tasks like digit span backwards and letter-number sequencing, in addition to other cognitive tests. They found that stress made startle responses stronger and reduced PPI, thereby degrading the participants’ ability to filter out the loud noise when it was preceded by a quieter one. Stress also impaired performance on working memory tasks compared to the non-stressed group. In practical terms, these results suggest that acute stress doesn’t just make one more reactive; it can interfere with basic sensory gating and cognitive control. This has implications for stressful jobs or situations (e.g., emergency responders or pilots) and possibly for understanding disorders where PPI or working memory is impaired.

These are just a few examples of how research into startle response and PPI can improve our understanding of the brain’s basic filtering and stress-response systems. The knowledge these studies provide may eventually translate into practical tools for diagnosis, prevention, and performance optimization. For additional information on research applications, check out our webinar on Startle and PPI.

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Back to the Wild: Measuring the Effects of Human Interaction with Nature

“I think that I cannot preserve my health and spirits, unless I spend four hours a day at least—and it is commonly more than that—sauntering through the woods and over the hills and fields, absolutely free from all worldly engagements.” —Henry David Thoreau

In his 1861 essay “Walking,” transcendentalist writer and philosopher Henry David Thoreau extolled the virtues, both physical and mental, of communing with nature. While the psychological and physiological benefits of human connection with the natural environment are well established, modern science has taken a closer look at these interactions. Today’s researchers often rely on interdisciplinary approaches that blend psychology, physiology, neuroscience, and environmental science to investigate the mechanisms behind nature’s restorative effects on mind and body. With continued urban growth and shrinking access to wild rural spaces, as well as the digitization of our daily lives, this field has become more relevant than ever.

Researchers study human interactions with nature to better understand the tangible health and psychological benefits associated with exposure to natural environments, such as reduced stress, improved mood, and enhanced cognitive function. Theories such as the Biophilia Hypothesis and Attention Restoration Theory (ART) suggest that humans have a built-in affinity for nature, which can support mental and emotional well-being. Psychophysiological research seeks to uncover the processes underlying these effects and to compare how different environments—whether urban, natural, or virtual—impact our bodies and minds.

The study of human-nature interaction encompasses a wide range of practical applications, including healthcare and mental wellness. Beyond health applications, this field informs decisions and policies regarding urban planning and architecture, such as the design of biophilic buildings and green spaces in cities. Research also aims to help individuals focus their attention, enhance creativity, and promote emotional well-being in both work and educational settings.

A study published in the Journal of Environmental Psychology examined how immersion in nature and exposure to nature-related images affect attention and could be used in attention restoration therapy and related applications. Researchers measured participants’ neural activity before, during, and after a four-day group camping trip in Utah using electroencephalography (EEG) to capture reward positivity (RewP), a brain signal associated with reward processing. During these periods, researchers measured how participants responded to extrinsic rewards, including monetary incentives. To ensure data integrity and minimize motion artifacts in the outdoor setting, the team utilized BIOPAC’s wireless BioNomadix EEG system and verified electrode contact using the EL-CHECK impedance checker. The study’s findings showed a significant decrease in neural responsiveness to extrinsic (monetary) rewards following immersion in nature. This suggests that increased time spent immersed in natural environments may recalibrate the brain’s reward sensitivity and promote intrinsic motivation. These findings have implications for a variety of behaviors related to extrinsic stimuli, such as the treatment of addiction.

Not all research into human-nature interactions focuses on immersion in real-world environments. With the evolution of virtual reality (VR) technology, new research leverages artificial environments to elicit biophilic responses. A study by researchers at the Southwest Jiaotong University School of Architecture in China, published in Frontiers in Public Health, investigated how exposure to biophilic design elements affects stress recovery in older adults. A group of 25 participants over the age of 60 were exposed to stressors and then underwent sessions with randomized VR environments that included green walls and outdoor views. The researchers measured two key physiological signals: heart rate variability (HRV), which assesses parasympathetic activity, and skin conductance level (SCL), a marker of sympathetic arousal. Electrocardiogram (ECG) data were collected using a BIOPAC ECG amplifier, while electrodermal activity was gathered via an EDA amplifier. Both signals were recorded using a BIOPAC data acquisition and analysis system. Results found that participants exposed to environments with green features demonstrated significantly higher HRV and lower SCL, indicating enhanced autonomic recovery and reduced stress. These findings suggest that the biophilic benefits of nature exposure can be made available to individuals virtually when real-world immersion is not possible or available.

As these studies demonstrate, there exists a wide and varied frontier to explore how human interaction with nature shapes our physiological, neurological, and psychological well-being. For more information on the tools to assist with such research, visit our Webinars library for detailed video trainings on how to use these technologies in your nature-related study.

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Game On: Applying Physiological Data in Video Game Design and Research

Ever since players first started feeding quarters into arcade games and began plugging in home systems in the late twentieth century, researchers have looked for practical tools for both shaping video game design and measuring their effects on players. Physiological signals filled this niche area of research. Researchers began investigating the connection between physiological science and gaming in the 1980s and 1990s, when early studies explored the effects of video games on heart rate and arousal. These first studies focused on issues such as aggression and overstimulation, but research has since expanded to encompass the cognitive and emotional aspects of gameplay. An early research project by NASA, for example, examined how biofeedback could be applied to game design to enhance traditional game control methods while also improving players’ cognitive abilities.

Today, physiological monitoring is not only a method for psychological inquiry but also a vital asset in improving user experience (UX) research, game accessibility, and even driving therapeutic game development. As wearable sensors and game engines grow more sophisticated, the integration of physiological signals into game design is opening new frontiers for immersive, responsive, and health-conscious gaming. By analyzing real-time bodily signals, such as heart rate (HR), electroencephalography (EEG), electromyography (EMG), electrodermal activity (EDA), respiration, photoplethysmography (PPG), and electrooculography (EOG), researchers and developers can gain a deeper understanding of how players emotionally and physically respond to game elements.

A study published in the International Journal of Human-Computer Studies investigated whether players’ self-reported preferences for first-person shooter (FPS) game dynamics match their emotional reactions during both gameplay and viewing. Researchers recruited 24 active gamers and divided them into two groups: those who enjoyed the fast-paced action of FPS games and those who didn’t. While participants played an FPS game and later watched a recording of it, the team measured electrodermal activity (EDA), heart rate, and facial muscle responses, specifically expressions associated with frowning (corrugator supercilii) and smiling (zygomaticus major), to capture emotional arousal and valence. Physiological signal data were recorded using BIOPAC EDA, PPG, and EMG amplifiers, which were connected to a data acquisition and analysis system running AcqKnowledge software. Although both groups reported more positive feelings and higher excitement after actively playing rather than watching, the data revealed a deeper story: players who disliked the game showed more substantial rises in arousal during play. Those who favored the dynamics, however, showed steadier emotional responses across both conditions. Muscle activity patterns also differed. Those who enjoyed FPS dynamics exhibited sharper increases in frowning-related muscle activity during play than watchers, indicating nuanced emotional engagement. Overall, the study found that what people say they prefer does reflect in their bodies’ emotional reactions. Still, those preferences also shape whether playing or spectating feels more intense, highlighting how combining self-reports with physiological signals can deepen an understanding of game design and player experience.

A team of researchers from Bournemouth University’s Centre for Digital Entertainment investigated how players’ bodies react during intense engagement, or flow, in virtual reality (VR) games. The goal was to capture objective physiological signals, such as heart rate and eye-blink patterns, alongside subjective self-reports to see how well a game’s design induced flow versus boredom or anxiety. The researchers had participants play a custom VR “tower defense” game while monitored with BIOPAC equipment, including a two-channel Biopac Student Lab (BSL) data acquisition system and physiological modules to record HRV via ECG, as well as EOG and EEG signals. The team then utilized clustering and machine-learning classifiers to decode flow states with high accuracy. The research team also successfully identified that high flow correlated with fewer blinks and longer blink intervals, indicating a state of deep concentration. The study not only demonstrates the value of combining physiological and self-report data but also shows how wearable sensors can inform design decisions in VR games by providing real-time feedback on player experience.

Beyond game design, a primary area of research focus has been on the long-term psychological, neurological, and physiological impact that games have on players. A study published in the Journal of Media Psychology explored how experiences with violent video games might reduce prosocial behavior, such as the motivation to help others, through physiological changes. Researchers recruited 155 Chinese college students who reported their exposure to violent games (in terms of violence, bloodiness, and duration) and completed simple self-reports measuring their willingness to help and the time they took to help others in controlled scenarios. Researchers used a BIOPAC data acquisition unit running AcqKnowledge software to record relevant physiological data. A three-lead ECG amplifier, respiration module, and respiration belt were used to record ECG and breathing signals across baseline, violent-film task, and during recovery periods. Researchers calculated the reduction in respiratory sinus arrhythmia (RSA), a marker of parasympathetic nervous system engagement. They found that higher levels of violent-game experience predicted less RSA reduction during stress, which in turn was linked to reduced prosocial behavior. The study’s findings suggest that playing violent video games may impair physiological readiness to respond in an empathetic manner to others, showing RSA reduction to be a key influence. The study’s findings demonstrate how physiological and psychophysiological signals provide a deeper understanding of the impacts of video games, while also guiding design decisions.

Physiological signals help researchers identify moments of excitement, stress, immersion, or frustration. Such insights are increasingly being used to refine gameplay mechanics, balance difficulty, and enhance player engagement through adaptive or personalized game experiences. They also reveal the short- and long-term effects gameplay has on both individuals and society. For more ideas on how to apply these signals in your research, visit our Webinars page for information on wearable devices, mobile data acquisition, and other helpful topics.

Are you planning a research project related to video games? Reach out to our customer service specialists to get all the help you need in mapping out and equipping your study team.

Mind-Body Connection: Biofeedback in Research

The connection between the mind and body has long intrigued scientists, driving research into how our thoughts, emotions, and mental states can influence physical health and well-being. Biofeedback has become a recognized approach for helping people manage stress, reduce pain, and even enhance cognitive and physical performance. Biofeedback involves using sensors and real-time data to monitor physiological functions that are typically automatic, such as heart rate, breathing, muscle tension, and skin conductance. With this information, individuals can learn to gain greater awareness and, in some cases, voluntarily control these bodily processes.

Common physiological signals used in biofeedback include electrodermal activity (EDA), which reflects sweat gland activity and emotional arousal; electroencephalogram (EEG), which measures electrical activity in the brain; electrocardiogram (ECG), which measures heart electrical activity; heart rate variability (HRV), an index of autonomic nervous system flexibility; and respiration rate, among others. These signals offer researchers a window into the body’s stress responses, regulatory mechanisms, and even aspects of cognition and emotional control.

To complement physiological monitoring, researchers are increasingly integrating tools like stimulus presentation systems, virtual reality (VR) environments, and eye tracking technology into biofeedback studies. These tools allow scientists to study how people react to controlled stimuli, immerse participants in realistic scenarios, and track where and how long someone focuses visually, all while collecting detailed data on their physiological responses. This combination of immersive experiences and real-time monitoring helps researchers investigate how the body responds to stress or cognitive challenges and whether individuals can be trained to influence those responses.

Swiss researchers at ETH Zurich investigated whether individuals could voluntarily control their arousal states using real-time feedback on their pupil size. Pupil size is a physiological marker closely linked to the brain’s arousal systems, particularly the locus coeruleus. Study participants employed mental strategies to adjust their pupil diameter, receiving visual feedback through a dynamically changing circle that reflected their pupil size. The participants’ cardiovascular data, including ECG and respiration, were recorded to provide insights into the physiological effects of pupil self-regulation. The research team employed a BIOPAC data acquisition and analysis system running AcqKnowledge software to record ECG data continuously at a sampling rate of 1,000 Hz. Additionally, a BIOPAC respiratory effort transducer was used to measure respiration, although these respiratory data were not reported in the publication. The study’s findings demonstrated that pupil-based biofeedback enabled participants to modulate not only their pupil size but also associated neural activity and cardiovascular responses, such as heart rate. The results suggest a non-invasive method for individuals to control their autonomic functions, with potential applications in managing stress and anxiety disorders.

Vagally mediated heart rate variability (vmHRV) refers to the natural changes in the time between heartbeats that are controlled by the vagus nerve, which is closely tied to how well a person can adapt to stress and regulate their body. Researchers from Université Paris Cité explored whether a brief session of vmHRV biofeedback could help people better control their memory, specifically whether it could help them tell the difference between real and false memories. In the study, 71 healthy young adults completed a VR memory task after receiving either vmHRV biofeedback or a simple breathing exercise. To track their physiological responses, the team used a BIOPAC data acquisition and analysis system and recorded heart activity via a three-lead ECG configured according to Einthoven’s triangle using Lead II. The results showed that this short biofeedback session had no immediate effect on memory accuracy or on vmHRV levels during the task. This suggests that a single session of HRV biofeedback may not be enough to influence memory-related brain functions, underlining the complex relationship between the body’s stress responses and cognitive control.

A study published in the Journal of Human Kinetics looked at whether just one 10-minute session of HRV biofeedback, using a special breathing technique called resonance frequency breathing, could affect the level of activity of certain nerve cells. Researchers measured this by looking at a reflex in the lower leg muscle (the soleus) called the Hoffman reflex (H-reflex). Twelve healthy men took part in both the HRV biofeedback session and a regular breathing session in a random order. To measure muscle activity, researchers used a BIOPAC surface electrode on the leg and a reference electrode on the hand. The signals were recorded with a BIOPAC data acquisition system and analyzed with AcqKnowledge software, which helped line up the timing of muscle activity with electrical stimulation. The results showed that HRV biofeedback lowered the strength of the reflex and a related ratio (Hmax/Mmax), suggesting the spinal nerve cells were less excitable. These findings point to the potential of short HRV biofeedback sessions to affect the nervous system in ways that could be useful for physical therapy or improving movement control.

To learn more about how to integrate biofeedback techniques into your next research project, check out BIOPAC’s webinar, Biofeedback: Theory, Techniques, and Tools for Research.

Are you planning a research project that will utilize biofeedback data? Our expert customer service representatives can help you find the right tools for all your biofeedback needs.

Aesthetically Pleasing: Exploring How the Brain Perceives the Arts

Beauty is in the eye of the beholder—a mostly subjective experience, so the saying implies. While we may share many common ideals about beauty and aesthetics, our reactions to art, music, and literature can diverge, converge, and overlap to a myriad of degrees. Neuroaesthetics explores how the brain perceives and responds to art, music, and other aesthetically evocative experiences. Combining neuroscience with psychology and the arts, researchers seek to understand why humans find certain images, sounds, or designs appealing and how these perceptions influence our emotions, cognition, and behavior. This interdisciplinary science has practical applications across a wide range of fields, including design, marketing, education, and mental health therapy, where understanding aesthetic experience can inform and enhance user engagement, learning, and emotional well-being.

Biometric signals provide insight into emotional and cognitive processing, allowing researchers to gain valuable data on how the brain creates and responds to aesthetically engaging stimuli. Commonly used techniques include electrodermal activity (EDA), which measures changes in skin conductance linked to emotional arousal; electroencephalography (EEG), which tracks brainwave patterns associated with attention and engagement; functional near-infrared spectroscopy (fNIRS), which monitors blood flow changes in the brain; and functional magnetic resonance imaging (fMRI), which provides high-resolution images of neural activity.

Additionally, the use of virtual reality (VR) and augmented reality (AR) is expanding in neuroaesthetics research, allowing scientists to create controlled, immersive environments that mimic real-world experiences. These technologies offer new ways to investigate how individuals engage with art and design in dynamic, interactive settings, pushing the boundaries of how we understand and harness aesthetic experiences.

Researchers in Shanghai, China, for example, investigated how different visual modes—2D and 3D VR—affect emotional arousal, demonstrating how immersive environments influence emotional experiences. The research team utilized EEG to monitor brain activity and EDA to measure skin conductance responses, both indicators of emotional arousal. EDA and EEG data were recorded while study participants wore VR headsets to view 2D and 3D environments. Data was collected and analyzed using a BIOPAC MP system with AcqKnowledge software. The findings revealed that 3D VR environments elicited more intense emotional stimulation than 2D settings, as evidenced by higher beta (21–30 Hz) EEG power and increased EDA responses. According to the published findings, results suggest that enhanced perception in 3D environments leads to greater emotional engagement, highlighting the potential of 3D VR in applications such as immersive therapy, virtual training, and interactive entertainment.

A team of German researchers recently examined the intersection of neurology, psychology, music, and literature. Their findings, published in the journal NeuroImage, explored how melodic features influence the neural processing of spoken poems and songs, examining the interplay between language and music. Researchers employed fMRI to investigate the neural mechanisms underlying the processing of musical and nonmusical verse. The fMRI data revealed that both spoken poems and songs activated bilateral temporal auditory areas of the brain. One aspect of the study was the measurement of participants’ emotional responses to the stimulus, i.e., whether they liked the song or poem to which they were listening while the fMRI scan was conducted. To gather this data, participants interacted with a BIOPAC differential pressure transducer connected to the participants’ right and left index fingers to record the degree to which they enjoyed the music. The researchers stated the findings suggest that melodic properties are central to the aesthetic experience of both speech and music.

A study published by Britain’s Royal Society looked at the connection between aesthetic appreciation and emotional states, specifically how exposure to art or music can shift feelings of anxiety to curiosity. To understand how the brain perceives beauty, the researchers used EDA to assess participants’ physiological arousal during exposure to aesthetically pleasing stimuli, such as music. EDA data was gathered using a BIOPAC EDA amplifier connected to a data acquisition and analysis system while participants were administered anxiety-inducing electrical tactile stimulation during music listening sessions. The study demonstrated that aesthetic appreciation can reduce anxiety and promote curiosity by analyzing the EDA data alongside self-reported measures. The research team concluded that their results “might have potential applications across different human activities such as learning and therapy. The idea that aesthetic appreciation might affect anxious states and that expecting aesthetic rewards can transform anxiety into arousal and curiosity plays a central role in some psychotherapeutic models of human change.”

These examples provide a rough outline of a bigger picture, illustrating the many ways researchers use physiological signals to better understand the human mind’s response to art, music, and literature. For more information on the tools BIOPAC provides to assist in neurological and physiological research, see our online training and webinars.

Are you planning a research project to investigate the intersection of aesthetics and neuroscience? Contact a BIOPAC representative in your area to identify the right resources and equipment for a successful study.