Spatial cognition of emotional faces : how fast is our brain?

Abstract

There are two different routes in the brain that deal with the processing of sensory information and initiate a response. One fast route, the dorsal magnocellular pathway, involves structures like the amygdala and starts a rapid and automatic fear reaction, necessary in so-called fight-or-flight situations. The other route comprises the neocortex, initiating a slower response via the parvocellular ventral pathway. Previous studies have shown that different features of pictures, such as spatial frequency, orientation or amplitude, influence different pathways. In general, neurons in the brain get more activated to higher amplitude. Based on that, this study - consisting of two experiments - investigated the influence of amplitude in low spatial frequency (LSF) pictures on emotional reactions in the brain. In experiment 1, eighty-four volunteers participated in a startle eyeblink response study. Responses were enhanced to LSF facial pictures of high amplitude in comparison to low amplitude. In addition, a stronger eyeblink response was observed when measured at longer latencies (after 3,000 ms) in comparison to short latencies (250 ms), which could be explained by prepulse inhibition at shorter latencies. Moreover, a subjective test revealed a significant difference between the different emotional valences on a positivity scale. Experiment 2 further investigated whether reaction times were enhanced when watching high amplitude LSF facial pictures. Contrary to predictions, higher amplitude LSF pictures led to significantly longer reaction times, while low amplitude pictures initiated a faster response.