![]() In view of verb generation, particular relevance has been ascribed to frontal opercular brain regions as a target of basal ganglia input. Alternatively it has been suggested that word production involves distinct neuroanatomical networks, depending on the lexical class processed. Under the premise of higher semantic association of verbs than other word classes with motor action, various researchers discussed this observation as an indication of MC. It has been shown that persons with versus without PD differ from each other in view of verb processing across a variety of experimental conditions, implying naming, lexical decisions, comprehension and generation 18, 23, 24, 25, 26. The ambiguity of interpreting subtle cognitive changes in PD can be illustrated using the example of particular biolinguistic findings 23. From the perspective of MC, this seems to support model claims, but, of course, other explanations are possible. Although widespread cortical involvement in advanced disease stages may easily explain this association 21, less overt cognitive symptoms already prevail in early PD with leading bradykinetic symptoms and nigrostriatal brain affection 22. Clinically, MC positions are of particular interest in the context of Parkinson’s disease (PD), a prevalent condition with both motor and cognitive symptoms 20. In a reverse conclusion from the mentioned premises, motor system impairment was posited to hamper the processing of information with movement-related connotations 15, 16, 17, 18, and this was presumed to impact on various cognitive capacities up to abstract reasoning, depending on the particular formulation of the theory 19. In view of pathological conditions, MC was predominantly discussed in the context of neurological movement disorders. Criticized points are, amongst others, biased interpretation of weak effects of questionable significance, the assumption of motor-to-cognitive relatedness based on the co-occurrence of phenomena which are not necessarily interdependent, failed attempts to reproduce results central for the overall theory, and doubts about the appropriateness of MC and EC approaches to explain high-order cognition in complex real word scenarios 11, 13, 14. In an ongoing debate, this principle concept has been impugned 2, 11, 12. Typical findings discussed in this general framework are, for instance, motor cortex activation upon perceiving action-related words 8, resemblance of electroencephalographic activity during motor performance and observation 9, or language processing facilitated by the simultaneous execution of ‘congruent’ movements 10. As in other theories of embodied cognition (EC), in MC motor simulation is thought to be instrumental for the understanding of, e.g., gestures or semantic concepts related to movement 5, 6, 7. #ANOTHER WORD FOR CONNECTION CODE#It contrasts with the idea that cognitive operations are combinatorial computations in an abstract sign code without any connection to sensorimotor processing 3, 4. Motor Cognition (MC) is a controversially discussed theoretical paradigm, conceptualizing various mental functions as grounded in movement-related processing 1, 2. The results are compatible with the idea of some impact of motor system states on lexical processing. In persons with PD, DBS induced-changes of the motor condition appear to go along with formal and semantic shifts in word production. Lowered verb production went in parallel with a semantic shift: in persons with PD in the DBS-off, but not the DBS-on condition, the relatedness of produced words to own body-movement was lower than in controls. In the DBS-off, but not in the DBS-on condition, the proportion of verbs within this reduced output was lower than in controls. Persons with PD produced fewer words than controls. The analysis referred to the number of words produced, verb use, and the occurrence of different dimensions of movement-related semantics in the lexical output. 17 persons with PD and bilateral deep brain stimulation (DBS) of the subhtalamic nucleus (STN) and 17 healthy control persons engaged in a semantically unconstrained, phonemic verbal fluency task, the former in both DBS-off and DBS-on states. ![]() If this were the consequence of reduced motor simulation of prevalent action semantics in this word class, reduced PD pathophysiology should result in increased verb production and a general shift of lexical contents towards particular movement-related meanings. ![]() ![]() Various clinical observations have been interpreted in this controversial framework, amongst others, low verb generation in word production tasks performed by persons with Parkinson’s disease (PD). Embodied cognition theories posit direct interactions between sensorimotor and mental processing. ![]()
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