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Action semantics and the motor system: A neuromodulatory study on Parkinson’s disease patients

Mariano Nicolás Díaz Rivera

  • CABA,
  • Argentina
  • Mariano N. Díaz-Rivera ¹
  • , Diana M.A. Suárez-García ²
  • , Agustina Birba ³
  • , Máximo Zimerman ¹
  • , Jesús A. Diazgranados ⁴
  • , Agustín Ibáñez ¹
  • , Johan S. Grisales ³
  • , Juan F. Cardona ³
  • , Adolfo M. García ¹
  • 1 Universidad de San Andrés, Buenos Aires, Argentina
  • 2 Instituto de Psicología, Universidad del Valle, Cali, Colombia
  • 3 National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina
  • 4 Centro Médico Neurólogos de Occidente, Cali, Colombia

Impairments of action conceptualization (a cognitive domain grounded in motor brain networks) are pervasive in early Parkinson’s disease (PD). Yet, treatment options for these deficits are virtually unexamined and no study has tackled them via non-invasive brain stimulation. Here, we recruited 22 PD patients and performed a five-day randomized, blinded, sham-controlled study to assess whether anodal transcranial direct current stimulation (atDCS) over the primary motor cortex, combined with cognitive training, can boost action-concept processing in this population. On day 1, participants completed a picture-word association (PWA) task (involving action-verbs and object-nouns) and a resting-state EEG protocol. They were then randomly assigned to either an atDCS (n = 11, 2 mA for 20 m) or a sham tDCS (n = 11, 2mA for 30 s) group and performed an online PWA practice over three days. On day 5, they repeated the initial protocol. Relative to sham tDCS, the atDCS group exhibited faster reaction times for action (as opposed to object) concepts in the post-stimulation test, along with enhanced EEG connectivity across motor-related electrodes. These results suggest that action-concept deficits in PD are distinctively grounded in motor networks and might be countered by direct neuromodulation of such circuits. Also, they provide new evidence for mechanistic semantic models and inform a thriving agenda in the embodied cognition framework.