Neuropsychologia
-
In neurodegenerative disorders, neural damage can trigger compensatory mechanisms that minimize behavioural impairments. Here, we aimed at characterizing cerebral compensation during motor imagery in Parkinson's disease (PD), while controlling for altered motor execution and sensory feedback. We used a within-patient design to compare the most and least affected hand in 19 right-handed PD patients with markedly right-lateralized symptoms. ⋯ Furthermore, these regions increased their connectivity towards the left PMd for right (affected) hands in a lateral orientation. We infer that, in strongly lateralized PD patients, motor imagery of the most-affected hand exploits additional resources in extrastriate visual areas. These findings characterize the cerebral bases of the increased dependence on visual information processing during the generation of motor plans in PD, pointing to its compensatory role.
-
Mental rotation of body parts is performed through inner simulation of actual movements, and is likely to rely upon cortical and subcortical systems (e.g. motor and premotor areas and basal ganglia) involved in motor planning and execution. Studies indicate that sensory and motor deficits, such as for example pain, limb amputation or focal hand dystonia, bring about a specific impairment in mental rotation of the affected body parts. Here we explored the ability of patients affected by idiopathic cervical dystonia (CD) to mentally rotate affected (neck) and unaffected (hands and feet) body districts. ⋯ Results showed that CD patients are slow in mental rotation of stimuli representing body parts, namely hand, foot and head. This abnormality was not due to a general impairment in mental rotation per se, since patients' ability to rotate a non-corporeal object (a car) was not significantly different from that of healthy participants. We posit that the deficit in mental rotation of body parts in CD patients may derive from a defective integration of body- and world-related knowledge, a process that is likely to allow a general representation of "me in the external world".