2017年第二届曲阜视觉科学会议知识库

PURPOSE: To investigate the effects of fear conditioning on V1 neuronal responses.
METHODS: Adult macaque monkeys were used as subjects. Air puff to the face was used as the unconditioned stimulus (US), which was paired with gratings tilted clockwise (or counterclockwise) relative to the vertical (the conditioned stimulus, CS). Gratings tilted to the opposite direction served as the neutral stimuli (NS). The frequencies and durations of eye blinks were used as a behavioral assessment of fear responses. Neuronal activities in V1 were recorded with implanted microelectrode arrays. After establishment of the conditioned behavioral responses, we switched the CS and NS. Neuronal and behavior responses were recorded over the course of fear conditioning and reverse conditioning.
RESULTS: Fear conditioning markedly enhanced V1 neuronal responses at the conditioned grating orientations, whereas the response enhancement at the neutral orientations was much smaller. The learning effect was seen only in the early component of V1 responses, and was independent of neurons’ orientation preferences. We also observed a general increase of neurons’ spontaneously activity. When the CS and NS were switched, the learning effect in V1 reversed accordingly, showing a significant and transient enhancement at the new CS orientations. This reversal effect in V1 reached a plateau after only several hundred trials. However, the behavioral learning effect, that is, the establishment of specific blinking behavior to the newly conditioned orientations, remarkably lagged behind V1 changes, reaching a plateau after several days.
CONCLUSIONS:Fear conditioning results in formation of fear memory in the earliest stage of visual processing by altering the basic response properties of neurons. This might be a consequence of interactions between the amygdala and visual cortex over the course of conditioning.