The theory of mind is the ability to attribute mental states to oneself and others and to understand that others have beliefs, desires and intentions different from one's own. The aim of the study was to explore the neuropsychological correlates of theory of mind in patients affected by early Parkinson's disease (PD). Thirty-three PD patients and 33 age-, sex-, and education-matched control subjects underwent the Frontal Assessment Battery, as well as tasks assessing "cognitive" and "affective" theory of mind, and memory abilities; questionnaires evaluating behavioral disorders and quality of life were also administrated. Although the 2 groups did not differ on neuropsychological tasks, PD patients' performance on tasks assessing cognitive and affective theory of mind was significantly worse than controls. Moreover, PD patients had more behavioral disorders and worse quality of life than controls. After covarying for behavioral and quality of life scores, the differences between patients and controls on theory of mind tasks remained significant. "Cognitive" theory of mind was associated with Frontal Assessment Battery score and 2 domains of quality of life scale, whereas "affective" theory of mind scores correlated only with behavioral scales such as the Frontal Behavioral Inventory and Apathy Evaluation Scale. The results demonstrate that both affective and cognitive aspects of theory of mind are simultaneously impaired in early PD and suggest that deficits in the 2 subcomponents of theory of mind may be linked to dysfunction of different frontosubcortical circuitries in early PD.

Apathy has been defined as lack of motivation. It has been traditionally considered as a symptom of psychiatric disorders, such as major depression and schizophrenia, but more recently it has been recognized as a specific neuropsychiatric syndrome associated with neurodegenerative such as Parkinson’s disease (PD). As a consequence the reported prevalence of apathy in PD ranges from 13.9% to 70%; the mean prevalence is 35%. Prevalence of “pure apathy” (i.e., of apathy without comorbid depression and dementia) seems to be substantially lower, from 3 to 47.9%. High levels of apathy in PD are associated with decreased daily function, specific cognitive deficits and increased stress for families. Although neuroimaging studies do not provide a unique anatomic pattern, several data suggest that the ventromedial prefrontal cortex and the basal ganglia connected through frontal-subcortical circuits, are particularly involved in the genesis of apathy. At present, there are no approved medications for the treatment of apathy in and no proof of efficacy exists for any drug in current use. Further studies and innovative pharmacologic approaches are thus needed to ameliorate our understanding and treatment of apathy in PD.

Recent neurofunctional studies suggested that lateral prefrontal cortex is a domain-general cognitive control area modulating computation of social information. Neuropsychological evidence reported dissociations between cognitive and affective components of social cognition. Here, we tested whether performance on social cognitive and affective tasks can be modulated by transcranial direct current stimulation (tDCS) over dorsolateral prefrontal cortex (DLPFC). To this aim, we compared the effects of tDCS on explicit recognition of emotional facial expressions (affective task), and on one cognitive task assessing the ability to adopt another person’s visual perspective. In a randomized, cross-over design, male and female healthy participants performed the two experimental tasks after bi-hemispheric tDCS (sham, left anodal/right cathodal, and right anodal/left cathodal) applied over DLPFC. Results showed that only in male participants explicit recognition of fearful facial expressions was significantly faster after anodal right/cathodal left stimulation with respect to anodal left/cathodal right and sham stimulations. In the visual perspective taking task, instead, anodal right/cathodal left stimulation negatively affected both male and female participants’ tendency to adopt another’s point of view. These findings demonstrated that concurrent facilitation of right and inhibition of left lateral prefrontal cortex can speed-up males’ responses to threatening faces whereas it interferes with the ability to adopt another’s viewpoint independently from gender. Thus, stimulation of cognitive control areas can lead to different effects on social cognitive skills depending on the affective vs. cognitive nature of the task, and on the gender-related differences in neural organization of emotion processing.

Developmental data suggested that mental simulation skills become progressively dissociated from overt motor activity across development. Thus, efficient simulation is rather independent from current sensorimotor information. Here, we tested the impact of bodily (sensorimotor) information on simulation skills of adolescents with Autism Spectrum Disorders (ASD). Typically-developing (TD) and ASD participants judged laterality of hand images while keeping one arm flexed on chest or while holding both arms extended. Both groups were able to mentally simulate actions, but this ability was constrained by body posture more in ASD than in TD adolescents. The strong impact of actual body information on motor simulation implies that simulative skills are not fully effective in ASD individuals.

The extrastriate body area (EBA) is involved in perception of human bodies and nonfacial body parts, but its role in representing body identity is not clear. Here, we used on-line high-frequency repetitive transcranial magnetic stimulation (rTMS) to test the role of EBA in self-other distinction. In Experiments 1 and 2 we compared rTMS of right EBA with stimulation of left ventral premotor cortex (vPM), whereas in Experiment 3 we compared stimulation of right and left EBA. RTMS was applied during a hand laterality task in which self or others' hand images were presented in first- versus third-person view (Experiments 1 and 3), or while participants had to explicitly recognize their own hands (Experiment 2) presented in first- versus third-person view. Experiment 1 showed that right EBA stimulation selectively speeded judgments on others' hands, whereas no effect of left vPM stimulation was found. Experiment 2 did not reveal any effect of rTMS. Experiment 3 confirmed faster responses on others' hands while stimulating right EBA and also showed an advantage when judging self with respect to others' hands during stimulation of left EBA. These results would demonstrate that EBA responds to morphological features of human body contributing to identity processing.