Efeitos da estimulação transcraniana por corrente contínua no reconhecimento de identidade e emoções faciais após acidente vascular cerebral

Abstract

After a stroke, individuals may experience impairments in face recognition. The relationship between the abilities to recognize facial identity and facial emotion has been debated for a long time, as there may be dissociation or interdependence between these processes. In the context of non-pharmacological interventions applied to neurological disorders, Transcranial Direct Current Stimulation (tDCS) has shown to be a promising tool for modulating cognitive abilities. In the present study, the effects of tDCS on the processing of facial identity and emotions in post-stroke patients were evaluated, with anodal stimulation performed over the fusiform gyrus in the right and left hemispheres. The thesis was divided into three parts. The first constituted a systematic review on the assessment tools for face recognition. The second involved a systematic review on the effects of tDCS on facial identity recognition. The third part comprised an empirical study on the effects of tDCS on facial identity and emotion recognition after stroke, through a randomized, double-blind, placebo-controlled study protocol. The sample consisted of 30 post-stroke participants divided into three groups: right hemisphere lesion with active tDCS, left hemisphere lesion with active tDCS, and right hemisphere lesion with placebo tDCS. Stimulation was directed to the fusiform gyrus, with an intensity of 1.5 mA for 20 minutes. Participants performed identity recognition (perception and memory) and emotion tasks before and during the intervention. The results obtained from the first study highlight the challenges in selecting the most appropriate instruments for the assessment of face recognition in the general population and in patients with prosopagnosia. The results obtained from the second study highlight that, depending on the protocol used, tDCS can influence face processing, particularly in terms of attention, holistic processing and working memory. In the third study, it was possible to observe that tDCS significantly improved facial identity recognition at the perception stage in groups with active stimulation, especially in the group with left hemisphere lesion. However, regarding facial emotion recognition, no significant differences were observed between groups. These results reinforce the specific role of the fusiform gyrus in facial identity recognition, while emotional processing seems to depend on broader neural networks. In summary, this thesis contributed to the knowledge about the effects of tDCS on facial identity and emotion recognition in an integrated manner, using a novel approach that seeks to stimulate a single brain area, the fusiform gyrus, to simultaneously evaluate two distinct domains of face recognition. Furthermore, by applying this protocol to a clinical sample of post-stroke patients, the study offers an important contribution, expanding the understanding of the interactions between these domains in rehabilitation contexts, and exploring the possibilities of more specific and targeted interventions.