Autonomic and central nervous responses to faces with different emotional expression: a multiple recording approach.

Stimuli as those represented by facial expressions of different emotional content elicit psychological and physiological responses. Several studies have pointed out modifications in heart rate, respiratory frequency, skin response and pupillary diameter. Other investigations have focused on evoked potentials, blink frequency, reaction times and ocular scanning. In all cases it was found that the face presentation is followed by a variable degree of alteration of the parameter examined. However, analysis of a single parameter and in only one domain (related to the autonomic or central nervous system) does not allow the overall complexity of the responses to be assessed and might overlook the strict dependence of autonomic effects on brain functioning. As a consequence, even if variation of a given parameter was considered a suitable index for measuring emotional state, it would not be exhaustive.Our aim attempts to overcome such inherent deficiencies. We acquired multiple recordings of four autonomic functions (heart rate, arterial pressure, skin response and pupillary area) with the simultaneous measurement of brain activity assessed by ocular scanning of the stimulus and mapping of event related potentials (ERP).A face, chosen among the six canonical emotional expressions, is randomly displayed on a monitor placed 1 m in front of the subject for 200 ms or 10 s. ECG, pletysmography, skin conductance response, ERP, ocular movements and pupil area are recorded simultaneously. Eye movements are obtained through IROG technique and pupil area from an AVI movie, taken at 12 frames/s. The ERP maps are related to 10-20 EEG standard recording positions.Preliminary results suggest that it seems possible to obtain for each subject and for every presented face a set of data which corresponds to a specific picture of the subjective emotional state.