Parkinson’s Disease: cognitive and behavioural aspects

Basal ganglia are traditionally related to motor disorders; the most typical confirm of this thought has been the sentence reported in the Essay on the Shaking Palsy, by James Parkinson. His patients have been described completely from a motor perspective, but Dr. Parkinson concluded that “senses and intellect are uninjuried”. More than 50 years after that book, Jean Charcot examined different patients suffering from Parkinson’ Disease, and his conclusions are far from those of Parkinson; he wrote: “In general, psychic faculties are definitely impaired; at a given point, the mind becomes cloud”. Till Parkinson and Charcot, many Autohors have tried to describe what they find during their long-time observational periods at the bed of different patients, with acute cerebral stroke in the basal ganglia regions, or affected by cerebral tumours. The traditional view of simple motor coordinator-centre has been challenged, mainly for the anatomical liaison with cerebral cortex and cerebellum nuclei and cortex. These connections, organized into discrete anatomical loops, control different cerebral regions, involved in motor sequence, in behaviour or even in higher-functions, such as cognition. The properties of neurons within the basal ganglia resemble the properties of neurons within the cortical areas subserved by the specific loop; in so far, neuronal activity within basal ganglia and cerebellar loops with areas of the motor cortex is highly correlated with motor parameters, and damage to these neurons leads to motor symptoms; neuronal activity within basal ganglia with areas of the prefrontal cortex is more related to voluntary deliberation, motivation and complex perception of the self, and the disruption of these circuits lead to higher –order deficits (Middleton and Strick, 2000). The myriad of symptoms described in basal ganglia pathologies seem to be determined by the maintenance of many of the physiological and behavioural properties of the cortical areas that they subserve, but also by the possible influence of reward on neurons within prefrontal-basal ganglia circuits. Moreover, it must be considered the effective role of white matter alterations, often seen in basal ganglia alteration (mainly in tumour, traumatic lesions and cerebrovascular accident), which might exert an extension or a modification of the possible confined effect due to a limited and selected lesion of one of the nuclei of the basal ganglia domain.