The brain mapping of emotion in human faces: clinical aplication in epilepsy

Introduction: The ability to process multiple domains of the human face it is a well-developed capability in humans, contributing significantly to social interaction. The extraction of emotional content out of facial features is one such domain, which involves well-known brain structures, whose detailed contribution is nevertheless poorly characterized. Objectives: Our emphasis is on detection and functional characterization of the brain areas involved in emotional processing of faces, with particular focus on the contribution of frontal lobes to processing of basic facial emotion expressions, such as fear and happiness. Methods: Participants were ten healthy volunteers and five patients with occipital lobe epilepsies. Mapping neurovascular (BOLD) responses to fear, happy and neutral facial expressions were obtained through functional Magnetic Resonance Imaging (fMRI). Results: The results from the group of volunteers were used as a base for the construction of a quantitative database that included the following brain structures: fusiform gyrus, insula, amygdala, cingulate gyrus, and frontal-orbital cortex. The maximum Z-score obtained from each ROI as responses to the contrast fear-neutral faces produced higher statistically significant activations in the areas selected. Responses in clinical patients revealed focal impairments only in right hemisphere epilepsies, consistent with a hemispheric asymmetry for emotional processing. Conclusions: The frequent association of some brain structures involved in facial emotion processing in epilepsy suggests that the proposed mapping protocol can be clinically useful to gain deeper insights into the anatomical-functional correlations of this disease.