Anomalous Anticipatory Brain Activation Preceding Exposure of Emotional and Neutral Pictures

The present study examined the neural substrates of anticipation in conjunction with functional magnetic resonance imaging (fMRI). Ten subjects were scanned while 48 pictures were presented. Each stimulus sequence started with the 4.2 seconds presentation of a fixation point before and during which the anticipation was measured. After the exposure of the stimulus picture which lasted also 4.2 second there was a period of 8.4 seconds during which the subject was supposed to recover from the stimulus presentation. It is found that large parts of the visual cortex do show larger activity after emotional stimuli than after calm. All brain regions that show a difference have also a response on calms except for regions that are at or near the amygdala. Here violent and erotic stimuli do generate a response but the response on calm stimuli is flat. Anticipatory effects tend to influence baseline values and hence influence the response values. This might be a problem if the subject is guessing the upcoming stimulus condition correctly but with proper randomization this is theoretically impossible. Great care was taken to randomize stimulus conditions with replacement while using different pictures for each stimulus presentation . Results suggest that, in spite of proper randomization, anticipatory activation preceding emotional stimuli is larger than the anticipatory activation preceding neutral stimuli. For the male subjects this appeared before the erotic stimuli while for the female both erotic and violent stimuli produced this anomalous effect. Possible normal explanations of this apparent anomaly, also called ‘presentiment’, are discussed. Most notably the possibility that this effect is just a result of ‘fishing’ for the right analysis out of many possible analyses. Exploratory results are presented dealing with differential effects in the responses to emotional stimuli and calm visual stimuli.