Sub-regional functional specificity of sub-cortical structures underlying emotional valence and arousal: MEG evidence

C. Styliadis, A.A. Ioannides, P.D. Bamidis and C. Papadelis

Abstract: Emotions are usually represented by arousal and valence which span the affective space as orthogonal entities. Arousal and valence are sub-served by unified mechanisms of distinct neural circuits of cortical (e.g. prefrontal cortex) and sub-cortical (e.g. amygdala, cerebellum) regions. The amygdala and the cerebellum have been found to play pivotal roles in the encoding of both arousal and valence. These sub-cortical structures, though anatomically homogenous, are formed up by distinct sub-regions that can be identified with the use of probabilistic cytoarchitectonic maps (PCMs). The amygdala and the cerebellum sub-regional contributions to emotional processing are still elusive. Magnetoencephalography (MEG) recordings were performed on 10 healthy human subjects passively viewing stimuli from the International Affective Picture System (IAPS) collection using a 2 (Valence levels) x 2 (Arousal levels) design. A beamformer was employed for source reconstruction within 1-30 Hz and 30-100 Hz. The identified sub-regional foci of amygdala and cerebellar activations were related to their equivalent PCMs. Within 1-30 Hz, unpleasant stimuli were encoded by the right laterobasal (LB) amygdala activity, while high arousal and pleasant stimuli were encoded by the left centromedial (CM) amygdala activity. Within 30-100 Hz, high arousal was found to be encoded by both vermal (VIIIa) and hemispheric (VIIa Crus II) cerebellar activity while high arousal and pleasant stimuli were encoded by left hemispheric (V) cerebellar activity. Our findings highlight the sub-regional functional specificity of these sub- cortical structures for arousal and valence and their interaction in the healthy population and may potentially contribute to emotionally declining population.