Performance of visually triggered wrist movements task in monkey: an application of information theory to evaluate deficits following unilateral substantia nigra pars reticulata lesion.

On the basis of an information theory approach, visual-motor efficiency (VME) was analyzed during pointing movement tasks in rhesus monkeys. This application was used to evaluate deficits in the ability to perform pointing movements as well as to chart the progress of the monkey during the chronic stage recovery period following unilateral lesion of the medial part of the substantia nigra pars reticulata. This unilateral lesion produced slight but significant chronic contralateral head roll tilt associated with body turning and induced profound modification of the VME at the beginning of the chronic stage of the symptomatology. Recovery developed in the following weeks, leading to a 3-fold increase in VME. However, at the end of the test (4 weeks postoperative), performance remained sub-normal: a decrease of 20-30% when compared to the control.