Macro- and micro-structural cerebellar and cortical characteristics of cognitive empathy towards fictional characters in healthy individuals

Abstract

Few investigations have analyzed the neuroanatomical substrate of empathic capacities in healthy subjects, and most of them have neglected the potential involvement of cerebellar structures. The main aim of the present study was to investigate the associations between bilateral cerebellar macro- and micro-structural measures and levels of cognitive and affective trait empathy (measured by Interpersonal Reactivity Index, IRI) in a sample of 70 healthy subjects of both sexes. We also estimated morphometric variations of cerebral Gray Matter structures, to ascertain whether the potential empathy-related peculiarities in cerebellar areas were accompanied by structural differences in other cerebral regions. At macro-structural level, the volumetric differences were analyzed by Voxel-Based Morphometry (VBM)- and Region of Interest (ROI)-based approaches, and at a micro-structural level, we analyzed Diffusion Tensor Imaging (DTI) data, focusing in particular on Mean Diffusivity and Fractional Anisotropy. Fantasy IRI-subscale was found to be positively associated with volumes in right cerebellar Crus 2 and pars triangularis of inferior frontal gyrus. The here described morphological variations of cerebellar Crus 2 and pars triangularis allow to extend the traditional cortico-centric view of cognitive empathy to the cerebellar regions and indicate that in empathizing with fictional characters the cerebellar and frontal areas are co-recruited.

The Cerebellum as an Embodying Machine

“…In contrast to the numerous functional findings assessing cerebellar involvement in state empathy, only recently was the involvement of cerebellar structures in trait empathy (affective and cognitive) in nonpathologic subjects addressed ( Picerni and others 2021 ). Following the hypothesis that “larger is more powerful” ( Box 3 ), it is reasonable to maintain the position that an increase in the volume of a cerebellar region may result in enhanced function.…”

Involvement of the intrinsic functional network of the red nucleus in complex behavioral processing

“…The relation of another brain region of the RN network, the cerebellum, to IRI is also supported by functional characters of the cerebellum involved in high-level cognitive functions, such as affection, emotion, and language, as well as motor functions ( Leiner et al. 1993 ; Allen and Courchesne 1998 ; Schmahmann and Sherman 1998 ) in addition to an anatomical study in which IRI was associated with changes in volume of brain morphometry and mean diffusivity in the cerebellum ( Picerni et al. 2021 ).…”

Cerebellar engagement in the attachment behavioral system

“…Cerebellar areas then might be rightfully inserted in the attachment behavioral system described by Bowlby 2 . The cerebellar contribution to the attachment system may be interpreted as concomitant to a “feeling of being drawn toward” the affective stimulus, and reflects the more general cerebellar engagement in regulation of emotional and social behaviors 29 , 55 – 57 . Given the neuronal circuits putatively responsible for social processes are closely associated with, and virtually inextricable from, those devoted to emotional regulation 58 , it is not surprising that the same regions of the posterior cerebellum and prefrontal cortex are involved in both emotional regulation and social interaction.…”