Threat-related stimuli tend to attract attention, thus eliciting an involuntary orienting of spatial attention towards their location. Target detection is quicker and evokes larger P1 event-related potential (ERP) peak for probes replacing the location of threatening (valid condition) rather than neutral faces (invalid).
investigate the effect and time course of spatial attentional orienting towards fearful faces in High Functioning Autism (HFA) using RTs and ERPs.
RTs and ERPs (a 59-channel EEG) were collected from eleven HFA (age= 26.6y, IQ= 103.6) and twelve contol subjects (age= 23.6y, IQ= 109.4) in a go/no-go task, during which a pair of faces (an emotional, fearful or happy, and a neutral face) was briefly presented followed by a bar-probe presented unilaterally on either the left or right visual field. The bar appeared either at the emotional face’s location (valid condition) or at the neutral face’s location (invalid). Participants were asked to press a response-key only when the bar’s orientation matched that of the thicker segment of the fixation cross.
Controls showed longer RTs on invalid than valid trials following fearful but not happy faces whereas HFAs made slower responses on valid than on invalid trials following both happy and fearful faces. Consistent with these behavioral results, P1 ERP peak elicited by the bar-probe was both larger and shorter for the valid than invalid condition following fearful but not happy faces in controls. No such spatial validity effects on P1 were found in HFA subjects, following both happy and fearful faces.
Our present study shows that emotional faces divert HFA’s attention from their location, leading to longer RTs for valid than invalid trials. However, no spatial validity effects were found on P1 ERPs suggesting that processing of emotional faces does not influence through top-down attentional mechanisms early visual processing in HFA.