Neurophysiological and Autonomic Responses to Acute Physical and Emotional Stress: An EEG Study

The study will employ a within-subject repeated-measures design to investigate neurophysiological, autonomic, subjective, and cognitive responses to different acute physical and emotional stress-inducing conditions.

Each participant will complete four experimental conditions within a single experimental session: (1) a resting-state baseline, (2) a Cold Pressor Test, (3) a negative autobiographical memory recall task, and (4) an affective picture-viewing task using stimuli selected from the Nencki Affective Picture System (NAPS). The order of the experimental stress conditions will be randomized or counterbalanced across participants to reduce systematic order, habituation, fatigue, and carry-over effects. Appropriate recovery periods will be introduced between conditions.

During the resting-state baseline, participants will remain seated and relaxed with their eyes closed for four minutes. This condition will provide a reference measure of spontaneous cortical and autonomic activity.

During the Cold Pressor Test, participants will immerse one hand in an ice-water bath and will be instructed to maintain the immersion for as long as tolerable, up to a maximum of three minutes. Participants will be allowed to withdraw their hand at any time if the stimulation becomes intolerable. Actual immersion duration will be recorded as an index of pain tolerance.

During the negative autobiographical memory recall condition, participants will be instructed to select a personally painful or distressing autobiographical memory and focus on its emotional and experiential aspects for three minutes while seated with their eyes closed. No specific autobiographical event will be suggested by the researcher.

During the affective picture-viewing condition, participants will view negative and neutral images selected from the NAPS. Each trial will consist of a fixation period followed by presentation of an affective or neutral image. The presentation order will be randomized.

Electroencephalographic (EEG) and autonomic activity will be recorded throughout the experimental session. Autonomic measures will include heart rate (HR), heart rate variability (HRV), electrodermal activity (EDA), and skin conductance responses (SCR). Particular attention will be given to EEG alpha-band activity over frontal, parietal, and frontoparietal regions.

Subjective ratings of stress, anxiety, and pain will be obtained using visual analogue scales (VAS) following the relevant experimental conditions. Participants will also complete validated psychological questionnaires assessing resilience, perceived stress using the 10-item Perceived Stress Scale (PSS-10), and state and trait anxiety using the State-Trait Anxiety Inventory (STAI-Y).

Executive functioning will be assessed using the 12-problem version of the Tower of London task. The task will be administered after the resting-state assessment and will provide a behavioral measure of executive planning and related higher-order cognitive processes.

The primary objective of the study is to characterize the modulation of EEG alpha-band activity associated with acute physical stress, with the main comparison focusing on the Cold Pressor Test relative to the resting-state baseline.

Secondary objectives include characterizing autonomic responses, including HRV, EDA, and SCR, and subjective stress, anxiety, and pain responses across the experimental conditions. Additional analyses will examine EEG activity across the different experimental conditions.

Exploratory analyses will investigate whether individual psychological characteristics, executive functioning, and pain tolerance are associated with differences in cortical, autonomic, and subjective responses to acute stress. Multivariate exploratory analyses may also be conducted to integrate EEG, autonomic, cognitive, and psychological measures and characterize individual patterns of psychophysiological stress response.

Inclusion criteria

• Age between 18 and 65 years.
• Ability to understand the study procedures and provide written informed consent.
• Sufficient knowledge of the Italian language to understand study instructions and complete the psychological assessments.

Exclusion criteria

• History of major neurological disorders or other medical conditions that could significantly affect EEG or autonomic measurements.
• Current severe psychiatric disorder that could interfere with participation in the experimental procedures.
• Cardiovascular conditions for which exposure to the Cold Pressor Test may be contraindicated.
• Medical conditions affecting peripheral circulation or sensitivity of the upper limbs that could interfere with or increase the risk associated with the Cold Pressor Test.
• Current use of medications that may substantially affect autonomic or central nervous system activity, when considered clinically relevant to the study procedures.
• Presence of wounds, injuries, or other conditions affecting the hand that would prevent safe completion of the Cold Pressor Test.
• Inability to complete the experimental procedures or provide valid informed consent.