Effect of levodopa on both verbal and motor representations of action in Parkinson’s disease: A fMRI study

The motor-semantic meanings of verbs generated by Parkinson's disease patients on/off dopamine medication in a verbal fluency task

“…In line with this, on the basis of the classical distinction of nouns and verbs in the brain (Damasio & Tranel, 1993), the deficit of PD patients in the action fluency task was explained by the disruption of the frontal cortex as a consequence of dopamine depletion in the fronto-striatal network, and has been considered a preclinical marker to conversion to dementia Piatt, Fields, Paolo & Koller et al, 1999). However, given the new data regarding the relationship between brain motor areas and action language processing in healthy volunteers (for a review see Pulvermüller, 2013) and patients with motor disturbance (Cardona et al, 2014;Herrera, Cuetos et al, 2012;P eran et al, 2013), we thought it would be interesting to analyze the words generated by PD patients in terms of their motor-semantic meaning. Other previous experiments failed to find differences in PD on/off medication using action and non-action verbs.…”

“…The action fluency task yields several measures that are well known to be affected in PD patients, such as a decrease in the number of words generated Piatt, Fields, Paolo & Koller et al, 1999;P eran et al, 2013) and an increase in the average lexical frequency of the generated verbs (Herrera, Cuetos et al, 2012). However, to the best of our knowledge, there is no evidence regarding the semantic meaning of those words generated by PD patients in terms of their motor content or the effect of dopamine on the semantics of verbs produced by PD patients.…”

Evidence of semantic processing impairments in behavioural variant frontotemporal dementia and Parkinson's disease

“…Compared with relatively preserved noun knowledge, studies have consistently shown that patients with Parkinson’s disease are impaired for action verbs during lexical decision [48], comprehension [49], generation [50,51] and naming tasks [52 ▪ ,53,54]. The role of the motor system during action verb processing is further supported by an experiment demonstrating that levodopa treatment – which is commonly administered as therapy for basal ganglia dysfunction – is associated with increased activation of motor and premotor cortex during the generation of action verbs [55]. Although action verb impairment in Parkinson’s disease is a consistent finding, few studies have specifically examined the effect of motor content.…”

“…Although Parkinson’s disease is classically thought of as a movement disorder, cognitive impairments have recently been recognized as commonly occurring [63]. Although many studies have linked the verb deficit in Parkinson’s disease to degraded motor representations [53–55], there is also evidence that poor executive functioning due to fronto-striatal disease contributes to the verb deficit in Parkinson’s disease [64,65]. Although the basal ganglia are not thought play a language-specific role in verb processing, their function in supervisory operations – inhibition of irrelevant information and enhancement of relevant information – may be important for efficient semantic selection processes [66,67].…”

Neural Foundations of Action-related Language: Studies in Parkinson’s Disease

“…Peran et al (49) performed fMRI on patients with PD during ON and OFF dopaminergic treatment states to investigate the effect of levodopa on action-related language. Participants were given three tasks; naming objects that they saw on the screen, producing a verb that could be used with the object they saw, and imagining the action in their minds.…”