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Abstract:
The use of grammatical rules such as regular past tense
-ed-suffixation has been linked to frontal/basal-ganglia circuits
previously implicated in the expression of motor skills, such as
using tools (Ullman et al., 1997). Frontal motor regions have also
been linked to naming pictures of tools. Therefore we hypothesized
that tool naming and grammatical rule use may share a common
frontal/basal-ganglia neural substrate. In contrast, naming objects
that do not require motor-skill knowledge, such as living things,
has been tied to temporal-lobe regions. Therefore we further
hypothesized that naming living things may pattern with the use of
irregular past tense forms, which have previously been linked to
temporal-lobe circuits believed to subserve conceptual knowledge
(Ullman et al., 1997). We gave patients with Parkinson's disease
(PD) or Alzheimer's disease (AD) an object naming task containing
tools and living things, and a task requiring the production of
regular and irregular past tenses. PD patients with severe
motor-skill deficits caused by basal-ganglia degeneration were
worse at naming tools than living things and at producing regular
than irregular past tenses. AD patients with severe conceptual
memory deficits linked to temporal-lobe degeneration showed the
opposite pattern. The results link tool naming and grammatical rule
use to motor skill expression and the basal ganglia, and the naming
of living things and irregular morphological transformations to
conceptual memory and temporal-lobe structures. McDonnell-Pew
grant; Army DAM-17-93-V-3018; NIH HD-18381
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