Modulation of the Somatosensory Blink Reflex under fear

Abstract

ObjectiveThis study evaluated the isolated and combined effects of fear and PPS paradigms on SBR. MethodThe prospective study was conducted with healthy participants. After stimulation of the right median nerve at the wrist, bilateral recordings were randomized under the following conditions: First experiment (with the right hand on the chair armrest): i. baseline recordings, ii. while watching fearful facial expressions from the Karolinska Emotional Faces battery (fear), iii. post-watching (post-fear), iv. while watching neutral facial expressions from the same battery (neutral), v. Immediately after viewing (post-neutral). Second experiment (right hand 2 cm away from the right eye, PPS): i. reference condition (PPS), ii. while watching fearful facial expressions (PPS-fear), iii. while watching neutral facial expressions (PPS-neutral). In each condition, SBR latency, area, duration, and amplitudes were measured and compared between conditions. ResultsWe included 16 participants. SBR could be recorded in 11 (mean age:30.7±5.2, F/M:5/6). First experiment: SBR amplitude was significantly reduced in fear condition (p=0.008), and SBR area was reduced considerably in fear and post-fear conditions (p=0.004) compared to the baseline. Second experiment: The SBR area was higher in the PPS (p=0.009) compared to the baseline and even higher in the fearPPS compared to the PPS (p=0.038). In neutral or PPS-neutral conditions, the area of the SBR did not change significantly. ConclusionFear suppressed SBR, but fear increased SBR when a threat stimulus was present. The findings were unrelated to habituation or attention, indicating cortical-amygdala-bulbar connections.