title: Spreading activation of lexical-semantic networks in Parkinson's disease.
abstract: Although dopamine may act as a neuromodulator of spreading activation within semantic networks, this role of dopamine in lexical networks has not been investigated. Hence, we sought to investigate the effects of Parkinson's disease (PD), which is associated with dopamine depletion, on spreading activation in the lexical networks. Ten Parkinson's disease patients and 11 normal controls performed the controlled oral word association test and the average word frequency for their responses was calculated and used as an index of spreading activation. The PD patients exhibited a lower average word frequency, suggesting increased spreading activation, and a significant relationship between the strength of the initial activation and subsequent extent of spreading activation. Most patients were taking dopaminergic medication and future studies may benefit from examining the changes in spreading activation in lexical networks in PD patients on versus off medication or in healthy controls taking either a placebo or a dopaminergic medication. Although these alterations in lexical access might be related to the reduction of dopamine, one of the hallmarks of PD, these patients also have alterations of other neurotransmitter systems and further studies are needed to more clearly identify the role played by these neurotransmitter on lexical access.
authors.affiliation: Psychology Department, Middle Tennessee State University, Murfreesboro, TN 37132, USA. paul.foster@neurology.ufl.edu
authors.forename: Paul S
authors.initials: PS
authors.lastname: Foster
authors.forename: Valeria
authors.initials: V
authors.lastname: Drago
authors.forename: David B
authors.initials: DB
authors.lastname: FitzGerald
authors.forename: Barry M
authors.initials: BM
authors.lastname: Skoblar
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Crucian
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Heilman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003210:Concept Formation / Q000502:physiology*; D035061:Control Groups; D004298:Dopamine / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D018377:Neurotransmitter Agents / Q000502:physiology; D010153:Paired-Associate Learning / Q000502:physiology; D010300:Parkinson Disease / Q000175:diagnosis / Q000503:physiopathology*; D011578:Psycholinguistics; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012660:Semantics; D014705:Verbal Behavior / Q000502:physiology*; D014936:Word Association Tests / Q000706:statistics & numerical data*
chemical_list: D018377:Neurotransmitter Agents; D004298:Dopamine