Brain activation during sentence processing in Parkinson's disease: an event related fMRI-study.

Linguistic research has revealed that some Parkinson*s disease (PD) patients
demonstrate difficulties with the comprehension of syntactically complex or
rather long sentences. However, it remains unclear whether cognitive
limitations such as working memory (WM), attention, and information processing
speed (IPS) account for the comprehension difficulties of PD (e.g. Grossman et
al., 1992; Grossman et al., 2000; Grossman et al., 2002; Lee et al., 2003); or
whether the impaired sentence comprehension is due to a specific grammatical
processing deficit (Lieberman et al., 1992; Natsopoulos et al., 1993;
Natsopoulos et al., 1991). Up until today, relatively little is known about the
involvement of the BG and/or fronto-striatal system in sentence comprehension.
PD is one of the disorders of the basal ganglia. In order to evidence the
involvement and the function of the BG in linguistic processes, we can study
this group of patients while performing language tasks. We hypothesise that
whenever the structure of a sentence deviates from the predicted syntactic
structure (because of for example and error), the BG are involved in order to
inhibit the irrelevant structure and to switch to a revision process.
(see for references in the protocol!)

The primary goal of this study is to understand the sentence comprehension
difficulties in Dutch speaking PD patients. Secondly, we developed the two
experiments to test the hypothesis that the BG are involved and play a
particular role in syntactic processing.

To test our hypothesis we developed six conditions by crossing two within
subject factors in a 2x2x3 factorial design. The first factor is word order
with two levels: active and passive. The second factor is grammaticality with
three levels: no violation, an inflectional morphology violation, and a
transitivity violation condition. On the basis of these six conditions we
created a set of materials that will be used in two different experiments. We
will first conduct an event related fMRI-experiment and analyze the brain
activations during a semantic relatedness task. After this scanning procedure
we will also conduct an off-line behavioral experiment to collect accuracy and
latency data on the grammaticality judgments.

Participating in the fMRI-study and subsequent behavioral experiment will ask a
mental burden of the participants. We do not expect a worsening of the mental
state by participating in the study. Up until today no risks are reported
testing people using a 3 Tesla MRI-scan. Before inclusion, the participants
will be screened for MRI incompatibility and during the scanning the standard
MRI safety regulations will be followed.