P 133. Effects of transcranial direct-current stimulation (tDCS) on the recognition of emotional facial expressions in schizophrenic patients and healthy controls

Abstract

Introduction Emotion recognition is a basic condition of successful social cognition and interaction. It is a prerequisite for correct attribution of mental states (‘Theory of Mind’). Schizophrenic psychoses are associated with reduction of this ability and thereby characterised with deficits in social interactions. Less activation of the left inferior prefrontal cortex (iFC), an area which includes the motoric speech area (Broca Area) as well as mirror neuron activity (BA 44), was identified as a neurophysiological signature of this deficit in patients with schizophrenia. BA 44 is considered as a basic element of emotional recognition. Transcranial direct current stimulation (tDCS) is a non-invasive technology for temporary and polarity specific modulation of cortical activity and cognitive function. Objectives This research was performed to assess the effects of tDCS on emotional recognition and possibly provide new treatment options for patients with reduction of this ability. Materials and methods In a double-blind, randomised, placebo controlled cross-over design, healthy subjects underwent either activity enhancing anodal (n = 26) or activity reducing cathodal (n = 24) tDCS (20 min, 1 mA), while performing the ’reading the mind in the eyes’ (RME) test where subjects have to infer mental states from pictures that depicted others’ eyes. The stimulating electrode was placed over the left iFC (EEG 10/20 system: F3) and the reference electrode supraorbital on the right. Results There was neither an effect on accuracy of emotion recognition under anodal (F = 0.173;p = 0.681) and cathodal (F = 0.453; p = 0.508) stimulation nor an effect on recognition speed (anodal: F = 0.029;p = 0.866; cathodal: F = 0.453;p = 0.508). We found a trend for an interaction between ’stimulation order’ and ’stimulation condition’ on reaction time (the participants were faster in the second measurement-anodal: F = 3.952; p = 0.058/ cathodal: F = 3.946; p = 0.06). This trend was not found for the number of errors (anodal: F = 0.285; p = 0.598; cathodal: F = 1.468; p = 0.239). Conclusion TDCS of the left iFC has no effect on accuracy of speed of emotional recognition in healthy subjects. However, interindividual differences in the underlying mechanisms of test performance and tDCS action may have interacted with the effect. First evidence for a reverse effect on emotional recognition in schizophrenic patients are analysed in current experiments.