The road less traveled: Alternative pathways for action-verb processing in Parkinson?s disease

ABREVAYA S; LUCAS SEDEÑO; SOL FITIPALDI; DAVID PINEDA; FRANCISCO LOPERA; OMAR BURITICA; ANDRÉS VILLEGAS; CATALINA BUSTAMANTE; DIANA GOMEZ; NATALIA TRUJILLO; PAUTASSI R.M; AGUSTÍN IBÁÑEZ; ADOLFO M. GARCÍA

Journal of Alzheimer?s Disease

IOS Press

Año: 2017 vol. 55 p. 1429 - 1435

Action verbs are critically embodied in motor brain networks. In Parkinson?s disease (PD),damage to the latter compromises access to such words. However, patients are not fullyincapable of processing them, as their performance is far from floor level. Here we tested thehypothesis that action-verb processing in PD may rely on alternative disembodied semanticcircuits. Seventeen PD patients and 15 healthy controls listened to action verbs and nounsduring fMRI scanning. Using cluster-mass analysis with a permutation test, we assessed taskrelatedfunctional connectivity considering seeds differentially engaged by action and nonactionwords (namely, putamen and M1 vs. posterior superior temporal lobe, respectively).The putamen seed showed reduced connectivity within the basal ganglia in patients for bothlexical categories. However, only action verbs recruited different cortical networks in eachgroup. Specifically, the M1 seed exhibited more anterior connectivity for controls and moreposterior connectivity for patients, with no differences in the temporal seed. Moreover, thepatients? level of basal ganglia atrophy positively correlated with their reliance on M1-posterior connectivity during action-verb processing. PD patients seem to have processedaction verbs via non-motor cortical networks subserving amodal semantics. Such circuits mayafford alternative pathways to process words when default embodied mechanisms aredisturbed. Moreover, the greater the level of basal ganglia atrophy, the greater the patients?reliance on this alternative route. These results offer new insights into differentialneurofunctional mechanisms recruited to process action semantics in PD.