Towards a better understanding of the role of subcortical nuclei participation in language: The study of a case following bilateral pallidotomy

Pallidotomy is a neurosurgical procedure that involves the creation of discrete lesions within the globus pallidus, in an attempt to relieve the akinetic and hyperkinetic symptoms associated with Parkinson's disease (PD). Populations undergoing such procedures provide an unprecedented opportunity to test operative theoretical models of subcortical participation in language. This paper reports the effect of circumscribed lesions of the globus pallidus on linguistic functioning, in a 73-year-old female with PD who underwent a bilateral pallidotomy to control dyskinesias, dystonia and unpredictable ‘on’ and ‘off’ states. In order to monitor the effects of pallidotomy on language, a linguisticprofile was compiled utilizing a battery of gross and high-level indices of language functioning in addition to an on-line measure of semantic processing, both before and after surgery. Baseline data were obtained one week prior to surgery and follow-up data were collected three months post-operatively. The results confirmed the presence of port-operative changes in language function subsequent to pallidotomy. Comparisons of pre- and post-operative language profiles revealed: (a) general language skills remained largely intact following pallidotomy; (b) post-operative fluctuations in performance on a number of measures of high-level linguistic functioning requiring complex divergent expressive language skills; (c) discrete lesions of the globus pallidus may impair performance on lexical decision tasks utilizing on-line measures of semantic processing, particularly for legal non-words (LNW) and words with few meanings (FM). These findings lend support to a hypothesized role for the globus pallidus in language, possibly via participation in a cortico-striato-pallido-thalamo-corticalloop.