The Impact of Long-term Isolation in Antarctica on Social Touch and Its Underlying Biological Mechanisms in Winter-over Crew Members, Assessed During Their Stay Using Standardized Touch Stimulation, Computer-based Touch Sensitivity Tests, Questionnaires and Biological Markers. (TACTICE)

Change in experiential C-tactile (CT) sensitivity assessed by pleasantness and intensity ratings on a Visual Analog Scale ranging from -10 to +10 using the Manual Tactile Stimulator.

Experiential CT sensitivity will be assessed using standardized stroking touch, delivered with a mechanic Manual Tactile Stimulator tool to the forearm and palm at three velocities (0.3, 3, and 30 cm/s), using smooth and ribbed probe surfaces. Participants rate perceived pleasantness and intensity on a Visual Analog Scale ranging from -10 to +10. Changes in VAS scores across repeated assessments will be used to characterize experiential CT sensitivity over time.

Change in vicarious C-tactile (CT) sensitivity assessed by pleasantness and intensity ratings on a Visual Analog Scale ranging from -10 to +10 using the Vicarious Touch Task

Vicarious CT sensitivity will be assessed using standardized 6-second videos depicting interpersonal touch at different body locations and velocities. Participants rate the perceived pleasantness and intensity of the observed touch on a Visual Analog Scale ranging from -10 to +10. Changes in ratings across repeated assessments will be used to characterize vicarious CT sensitivity over time.

Change in behavioral C-tactile (CT) sensitivity assessed by interpersonal space boundary using the Footstep Task with response time in milliseconds (ms).

Interpersonal space boundary will be assessed using an auditory stop-distance paradigm. Participants listen to approaching footsteps and press a key when the approaching person makes them feel uncomfortable. The outcome measure is the response time in milliseconds (ms) from stimulus onset to the stop response. Changes in response time across repeated assessments will be used as an indirect behavioral measure associated with CT sensitivity.

Change in neurobiophysiological C-tactile (CT) sensitivity assessed by salivary cortisol concentration (µg/L) measured by saliva sampling and analyses

Salivary cortisol concentration concentration will be measured as a neuroendocrine marker of HPA-axis stress regulation associated with C-tactile (CT)-mediated touch. Saliva samples are collected on one combined sampling evening and morning per month. One sample is collected before bedtime and three samples are collected in the following morning: immediately after awakening, 30 minutes after awakening, and 60 minutes after awakening. Cortisol concentrations (µg/L) and the cortisol awakening response (CAR) will be evaluated across repeated assessments over time.

Change in neurobiophysiological C-tactile (CT) sensitivity assessed by plasma oxytocin concentration (pg/ml) measured by blood sampling and analyses

Plasma oxytocin concentration will be measured from blood samples as a neuroendocrine marker associated with affiliative social touch and the rewarding neurobiology of C-tactile (CT)-mediated touch. Changes in plasma oxytocin concentration (pg/ml) will be evaluated across repeated assessments over time.

Change in psychosocial and behavioral characteristics associated with C-tactile (CT) sensitivity assessed using standardized questionnaires with total and/or subscale questionnaire scores.

Psychosocial and behavioral characteristics will be assessed using the Touch Experiences and Attitudes Questionnaire - short version (TEAQ-s), Brief COPE, UCLA Loneliness Scale, Experiences in Close Relationships - Short Form (ECR-S), and State-Trait Anxiety Inventory (STAI). These questionnaires assess social touch experiences and attitudes, coping strategies, loneliness and social isolation, attachment anxiety and avoidance, and state/trait anxiety, respectively. The outcome measures are the total and/or subscale questionnaire scores, calculated according to the scoring procedures of each instrument. Changes in these scores will be assessed across repeated measurements over time.

Change in behavioral and psychosocial adaptation associated with C-tactile (CT) sensitivity assessed using the 15-item ICE-Psychosocial Monitoring Scale with scores on a Visual Analog Scale (VAS-score 0-10).

Psychosocial adaptation during isolation and confinement will be assessed using the 15-item VAS-based ICE-Psychosocial Monitoring Scale. The scale assesses physical touch deprivation/contact need, social contact and interpersonal connection, situational/temporal loneliness, attachment and separation distress, and somatic self-soothing/physical regulation. Changes in VAS-based scores will be assessed across repeated measurements over time.

Change in tactile sensory performance associated with C-tactile (CT) sensitivity measured with the Brain Gauge Tactile Reaction Time Test (TRTT) using reaction-time and discrimination outcomes.

Tactile sensory performance will be assessed using the Brain Gauge TRTT, a mouse-like device that delivers gentle tactile vibrations to the fingertips. The test battery includes simple reaction time, amplitude discrimination, temporal order judgment, and duration discrimination. Time-related outcomes will be expressed in milliseconds (ms). Changes in reaction-time and discrimination measures will be assessed across repeated measurements over time.