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

SEDEÑO, LUCAS; GARCÍA, ADOLFO M.; ABREVAYA, SOFÍA; IBÁÑEZ, AGUSTÍN; FITIPALDI, SOL

Havana

Congreso; 18th World Congress of Psychophysiology; 2019

International Organization of Psychophysiology

Introduction: Relative to other lexical units, action verbs distinctively involve activations along motor brain networks. In movementdisorders, damage to the latter is associated with difficulties toaccess such words. However, patients are not fully capable ofprocessing them, as their performance is far from floor level.Action-verb processing may then rely on less efficient, non-motorsemantic circuits. To test this hypothesis, we separately measuredbehavioral performance and neurofunctional correlates during114 IOP 2016lexical processing tasks in Parkinson?s disease (PD) patients andhealthy controls.Methods: The sample comprised 17 pre-demented PD patientsand 15 socio-demographically matched controls presenting nohistory of psychiatric or neurological disease. Participants listenedto action verbs and nouns as they underwent fMRI scanning. Weselected seeds known to be differentially engaged by processing ofaction- (putamen, primary motor area) and non-action (posteriorsuperior temporal lobe) stimuli. For each participant, we extractedthe BOLD signal time-course from the voxels within each seedregion. Functional connectivity maps were obtained by correlatingthese data to every voxel in the brain using Pearson?s correlationcoefficient. The ensuing maps were then recalculated by reference totheir z scores. We performed a randomize analysis (5000 permutation) with a mass cluster based correction (p b .05 FWE corrected)with a 2.5 threshold, and made non-parametric permutationinferences on neuroimaging data.Results: FMRI data revealed that they recruited different networks only for action-related words. During noun processing,activity in all seeds was similar between groups. However, foraction-verb processing, analysis of the motor seed revealed greateractivations in posterior and anterior regions for patients (p = .03)and controls (p = .05), respectively. Analysis of the putamen seedshowed greater reduced functional connectivity in patients for bothlexical categories (p = .005 for verbs, and p = .03 for nouns).Discussion: Our results suggest that PD patients, unlike controls,process action-verbs via temporal networks implicated in amodalsemantics and post-lexical imagery. Such regions would affordalternative (though, arguably, less efficient) pathways to processword meaning when putative embodied mechanisms are disturbed(in this case, motor networks). Moreover, differences in putamenconnectivity for both action verbs and nouns points to a distinctassociation between the patients? distinctive physiopathology andlexical-level processing at large. These results offer new insights intonon-embodied routes for high-order processing, while revealingneurofunctional aspects of relevant compensatory mechanisms inneuropathology. [Work partially supported by CONICET, CONICYT/FONDECYT Regular (1130920), COLCIENCIAS (1115-545- 31374 and1115-569- 33858), FONCyT-PICT 2012-0412, FONCyT-PICT 2012-1309, FONDAP 15150012, and INECO Foundation].doi:10.1016/j.ijpsycho.2016.07.343