In search of the “I”: Neuropsychology of lateralized thinking meets Dynamic Causal Modeling
Background. Ideas about relationships between “I”, egocentric spatial orientation and the sense of bodily “Self ” date back to work by classics of philosophy and psychology. Cognitive neuroscience has provided knowledge about brain areas involved in self-referential processing, such as the rostral prefrontal, temporal and parietal cortices, often active as part of the default mode network (DMN).
Objective and Method. Little is known about the contribution of inferior parietal areas to self-referential processing. Therefore, we collected observations of everyday behavior, social communication and problem solving in patients with brain lesions localized either in the left inferior parietal cortex (LIPC group, n = 45) or the right inferior parietal cortex (RIPC group, n = 58).
Results. A key characteristic of the LIPC group was an overestimation of task complexity. This led to a prolonged phase of redundant and disruptive contemplations preceding task solution. In the RIPC group, we observed disorders in reflective control and voluntary regulation of behavior. Abilities for experiencing emotions, understanding mental states, and social communication were to a great extent lost. Results are interpreted within a multilevel framework of cognitive-affective organization (velichkovsky, 2002). In particular, we highlight the role of right-hemisphere mechanisms in self-referential cognition, emotional and corporeal awareness. This is consistent with recent data on a profound asymmetry in connectivity of left and right hippocampi within the DMN (Ushakov et al., 2016)
Conclusion. It seems that the center of egocentric spatial representation plays a special role in accessing self-related data. Normally, the right hippocampus provides a holistic representation of surrounding and, thus, an easy-to-find gateway into much of what we used to call “subjective experience”. This heuristics becomes misleading in the case of right-sided brain lesions.
Keywords: thinking, emotions, lateralization, hippocampal formation, neuropsychology, dynamic causal modeling (DCM), egocentric spatial orientation, Self-referential cognition, levels of cognitive organization