G. Kovács
Previous encounters with other people – or the temporal context of a given face – modifies its perception, such that a given picture of a person might look different at different times. Our previous research on priming and adaptation is shaping theories about the neural mechanisms and representations involved in face perception. As we are beginning to understand the relationship between these two phenomena, an account of the interaction between top-down processes, such as predictions, attentional cueing and sensory competition among stimuli becomes increasingly important. Project 1 will therefore study further the effect of prior experiences on face perception, using psychophysical, electrophysiological and neuroimaging methods and the theoretical frame of predictive coding models. In two lines of our planned experiments we will use repeated stimuli, leading to specific, high level aftereffects, priming or predictive cueing.
In the first line we will capitalize upon the previously found interactions among multiple simultaneously presented faces (Nagy, Greenlee, & Kovács, 2011). Using ERP recordings we will test the temporal dynamics of sensory competition among faces. Using fMRI, we will compare the competition effect (manifest in the reduction of the blood oxygen level dependent (BOLD) signal) for different categories versus faces, and test if a prior stimulus, serving as an attentional cue, is able to bias these competitions similarly or not. In our preceding experiments we were able to prove that previous experiences can change face perception, and that this effect is largely due to the altered activity of early face selective neurons. Here we will further test the effect of prior information on face perception, using the theoretical framework of predictive coding models. Predictive coding (PC) hypotheses assume that higher level neurons “predict” the forthcoming information by comparing the current stimulus against an internal template, and that this feedback suppresses predicted information. Currently, this model has been reconciled with another influential theory of visual perception, the biased competition (BC) model of attention which proposes that the feedback (rather than suppressing) enhances the neural responses evoked by the predicted stimulus.While both the PC and BC models have been studied extensively in the past, an analysis of their interaction has just started.
