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The role of the basal ganglia in cognition is still uncertain. This case study investigates the partial neuropsychological profile of a 20-year-old patient with a perinatal left putaminal lesion. This pathology is relatively rare and little is known of its cognitive effects. The focuses of our neuropsychological assessment were working memory, executive functions, analysis of spontaneous speech and implicit skill learning. The patient's executive functions did not attain the normal range, and working memory was also partially impaired. In addition, the temporal features of her speech revealed an increased pause/signal time ratio. Finally, in an implicit skill learning task, the patient showed general motor skill learning, but no sequence specific learning. Together these findings suggest that the frontal/subcortical circuit between the putamen and frontal motor areas plays a role in higher cognitive processing such as executive functions, working memory, as well as in first-order sequence learning.

A limited number of studies have investigated language in Huntington's disease (HD). These have generally reported abnormalities in rule-governed (grammatical) aspects of language, in both syntax and morphology. Several studies of verbal inflectional morphology in English and French have reported evidence of over-active rule processing, such as over-suffixation errors (e.g., walkeded) and over-regularizations (e.g., digged). Here we extend the investigation to noun inflection in Hungarian, a Finno-Ugric agglutinative language with complex morphology, and to genetically proven pre-symptomatic Huntington's disease (pre-HD). Although individuals with pre-HD have no clinical, motor or cognitive symptoms, the underlying pathology may already have begun, and thus sensitive behavioral measures might reveal already-present impairments. Indeed, in a Hungarian morphology production task, pre-HD patients made both over-suffixation and over-regularization errors. The findings suggest the generality of over-active rule processing in both HD and pre-HD, across languages from different families with different morphological systems, and for both verbal and noun inflection. Because the neuropathology in pre-HD appears to be largely restricted to the caudate nucleus and related structures, the findings further implicate these structures in language, and in rule-processing in particular. Finally, the need for effective treatments in HD, which will likely depend in part on the ability to sensitively measure early changes in the disease, suggests the possibility that inflectional morphology, and perhaps other language measures, may provide useful diagnostic, tracking, and therapeutic tools for assessing and treating early degeneration in pre-HD and HD.

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Background: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by cerebellar atrophy, peripheral neuropathy, oculomotor apraxia, and elevated serum alpha-fetoprotein (AFP) levels. The disease is caused by a recessive mutation in the senataxin gene. Since it is a very rare cerebellar disorder, no detailed examination of cognitive functions in AOA2 has been published to date. The aim of the present study was to investigate the neuropsychological profile of a 54-year-old patient with AOA2. Methods: A broad range of neuropsychological examination protocol was administered including the following domains: short-term, working- and episodic-memories, executive functions, implicit sequence learning, and the temporal parameters of speech. Results: The performance on the Listening Span, Letter Fluency, Serial Reaction Time Task, and pause ratio in speech was 2 or more standard deviations (SD) lower compared to controls, and 1 SD lower on Backward Digit Span, Semantic Fluency, articulation rate, and speech tempo. Conclusion: These findings indicate that the pathogenesis of the cerebrocerebellar circuit in AOA2 is responsible for the weaker coordination of complex cognitive functions such as working memory, executive functions, speech, and sequence learning.