Introduction: Neuropsychiatric symptoms are one of the most common non-motor symptoms in Parkinson's Disease (PD). These symptoms have a negative impact on daily living activities and

Background: Apathy is one of the most common neuropsychiatric symptoms in Parkinson's disease (PD). Few studies have investigated the cognitive and neuroanatomical correlates of apathy in PD, and those which have done so have not controlled for the presence of other neuropsychiatric comorbidities. Objective: To explore the cognitive and neuroanatomical correlates of apathy in PD at a mild disease stage. Methods: Sixty-five PD patients and 24 healthy controls participated in this study. Patients underwent extensive neuropsychological screening, neuropsychiatric assessment using the Neuropsychiatric Inventory, structural MRI scanning, and neurological examination. Voxel-based independent t-test analyses were used to assess the differences in grey and white matter volumes between the sample groups with/without apathy/neuropsychiatric symptoms. Results: Patients with apathy had lower grey matter volume in several brain areas including the left insula, left inferior/middle/medial frontal gyrus, right anterior cingulate, and the left superior temporal gyrus. Significant impairments were found in tests assessing executive functions, and a trend-level significant difference was observed in long term memory tests in patients with apathy, when compared with patients without apathy. Conclusions: Apathy was associated with greater levels of atrophy in the frontal and temporal cortex, and anterior cingulate, as well as overall lower level of cognitive performance, particularly in executive function and memory skills. Apathy appears to be associated with cognitive impairments in PD, therefore, treatment of this symptom might mitigate its effects on cognitive performance in this clinical population.

This review reports the outcomes of studies that examined the effectiveness of cognitive rehabilitation in PD. It also points out the limitations of the studies indicating the limited availability of follow up data on the long-term effects of cognitive interventions. The review also highlights the fact that some of the studies did not include a PD group who did not undergo training. There remains, therefore, a need for longitudinal studies to investigate the potential long term benefits of cognitive training. In addition, future investigations should examine whether any disease characteristics such as disease stage, degree of cognitive impairment and/or the dominant side (right/left) or specific motor symptoms (rigidity/tremor) influence treatment efficacy.

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