Poster D122, Monday, March 27, 8:00 – 10:00 am, Pacific Concourse
Threat adaptation in human visual cortex: neuronal orientation tuning in a two-phase conditioning paradigm
L. Forest Gruss1, Nathan M. Petro1, Andreas Keil1; 1University of Florida
The mammalian brain displays a perceptual bias towards learned threat signals. Classical aversive conditioning in the laboratory enables researchers to probe the mechanisms of this perceptual bias at the level of mass neuronal population activation through EEG. Rapid changes in visuocortical discrimination of threat versus safety cues are thought to have multiple mechanistic contributors: local inhibitory interactions of orientation-sensitive neurons and top-down modulation from anterior cortical structures. The aim of the current research was to investigate the temporal, adaptive changes of instructed threat and safety cues during a two-phase conditioning paradigm. In the first conditioning phase, a Gabor grating of a 45° orientation (CS+) was paired with a noxious acoustic stimulus (US; 96dB white noise) while 6 other orientations (15°-75°) functioned as safety cues (CS-). In the second conditioning phase a new CS+ was paired with the US, most proximal in orientation to the old CS+ (i.e. 55° and 35°, two experiments respectively). Results from both studies (N=29) indicate sustained visuocortical enhancement to the first CS+ via the steady state visually evoked potential (ssVEP) throughout all experimental blocks. Furthermore, enhanced activation to the new CS+ was accompanied by suppression of gratings most proximal to the direction of the new pairing (65° and 75° suppressed for a 55° CS+). Gratings in the direction of the old CS+, however, displayed increased activation into extinction. This asymmetrical activation pattern implicates a perceptual bias specifically to the first-acquired threat signal, including safety signals most similar to the first, but not second, threat cue.
Topic Area: PERCEPTION & ACTION: Vision