Linguistic testing during ON/OFF states of electrical stimulation in the associative portion of the subthalamic...

Long-term studies of subthalamic nucleus (STN) deep brain stimulation (DBS) in patients with Parkinson's disease have shown potential cognitive and linguistic side-effects. In this pilot study, we examined whether direct monopolar stimulation in the ventral, associative STN would result in language effects.

Three subjects participated in two linguistic tasks targeting language generation (language samples) and language composition (syntactic/grammatical structures). All subjects were tested in ON-/OFF-associative stimulation settings. The subjects' Unified Parkinson's Disease Rating Scale scores in ON/OFF medication were taken; all subjects' scores indicated that DBS would be beneficial. Testing was conducted in the associative STN at varying stimulation settings of amplitude (80% of previously determined side-effect threshold), pulse width, and frequency.

Linguistic functioning was affected by electrical stimulation to the associative STN. The data reflected a general decline in linguistic functioning in the ON stimulation setting.

Our data support previous findings implicating STN stimulation in cognitive-linguistic effects. A larger patient group with a blinded methodology is warranted.