The Road Less Traveled: Alternative Pathways for Action-Verb Processing in Parkinson’s Disease

Abstract

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 fully incapable of processing them, as their performance is far from floor level. Here we tested the hypothesis that action-verb processing in PD may rely on alternative disembodied semantic circuits. Seventeen PD patients and 15 healthy controls listened to action verbs and nouns during functional MRI scanning. Using cluster-mass analysis with a permutation test, we assessed task-related functional connectivity considering seeds differentially engaged by action and non-action words (namely, putamen and M1 versus posterior superior temporal lobe, respectively). The putamen seed showed reduced connectivity within the basal ganglia in patients for both lexical categories. However, only action verbs recruited different cortical networks in each group. Specifically, the M1 seed exhibited more anterior connectivity for controls and more posterior connectivity for patients, with no differences in the temporal seed. Moreover, the patients' level of basal ganglia atrophy positively correlated with their reliance on M1-posterior connectivity during action-verb processing. PD patients seem to have processed action verbs via non-motor cortical networks subserving amodal semantics. Such circuits may afford alternative pathways to process words when default embodied mechanisms are disturbed. Moreover, the greater the level of basal ganglia atrophy, the greater the patients' reliance on this alternative route. Our findings offer new insights into differential neurofunctional mechanisms recruited to process action semantics in PD.

Action‐semantic and syntactic deficits in subjects at risk for Huntington's disease

“…Unfortunately, HDRels lacked genetic testing, which prevented us from assessing correlations between behavioural results and the expression of possible mutations. Although asymptomatic relatives constitute a well-established vulnerability group at risk for HD, even in the absence of confirmed genetic alterations (Baez et al, 2015(Baez et al, , 2016Dorsey, 2012;Giordani et al, 1995;Kargieman et al, 2014;Markianos et al, 2008;Panegyres & Goh, 2011), it would be most informative to replicate our study in combination with exome sequencing or other forms of genetic assessmentfor an example, see Garc ıa, Abrevaya, et al (2017). Also, we were unable to collect neuroimaging data to corroborate the hypothesized roles of specific frontostriatal hubs to different subdomains.…”

“…However, syntactic and actionsemantic tasks may be even more sensitive to such an end. Evidence from other motor disorders, such as PD (Bocanegra et al, 2015) and genetic ataxia (Garc ıa, Abrevaya, et al, 2017) shows that both domains can become compromised even when MoCA scores are normal. Moreover, HDRels may feature high-order difficulties even in the absence of MoCA deficits (e.g., Baez et al, 2016), whereas mutation carriers at risk for other frontostriatal motor conditions have been observed to feature syntactic deficits even when performance in domain-general batteries is spared .…”

“…As the latter are less concrete and imaginable than the former (e.g., Dalla Volta, Fabbri-Destro, Gentilucci, & Avanzini, 2014; Garc ıa & Ib añez, 2016a), they are harder to process even when matched for other relevant variables. Despite such differences, patients with motor disorders evince selective action-verb deficits even when processing of the even more demanding abstract-verb category is spared, as observed in PD (Fernandino et al, 2013) and genetic ataxia with preserved MoCA performance (Garc ıa, Abrevaya, et al, 2017). In line with this evidence, the selective action-semantic impairment in HDRels is probably reflects the specific relation between motor networks and action semantics, rather than non-specific, demand-related effects.…”

A Lesion-Proof Brain? Multidimensional Sensorimotor, Cognitive, and Socio-Affective Preservation Despite Extensive Damage in a Stroke Patient

“…These steps are critical and perhaps unavoidable to characterize the organ's functional organization with some degree of external validity. Indeed, thanks to this approach, replicable associations have been established between damage to circumscribed regions and impairments of specific functions, including motor (Zgaljardic et al, 2003), somatosensory (Meyer et al, 2016), socio-cognitive (Gold and Shadlen, 2007; Ibáñez et al, 2010, 2016b; Couto et al, 2013; Baez et al, 2014, 2016b,c; Melloni et al, 2016), interoceptive (Couto et al, 2015; García-Cordero et al, 2016), executive (Rabinovici et al, 2015; Sedeño et al, 2016), linguistic (Ullman, 2008; Cardona et al, 2014; García and Ibáñez, 2014, 2016; Bocanegra et al, 2015; García, 2015; Melloni et al, 2015; García et al, 2016a,b,c; Abrevaya et al, 2017), and pragmatic (Kaplan et al, 1990; Stemmer, 2008) skills.…”

The relationship between executive functions and fluid intelligence in multiple sclerosis

“…A grey-matter analysis was performed to establish the participants' grey matter volume. Data were preprocessed on the DARTEL Toolbox following validated procedures [53][54][55][56][57] and using Statistical Parametric Mapping software (SPM12) (http://www.fil.ion.ucl.ac.uk/spm/software/ spm12/). Images were segmented into grey matter, white matter, and cerebrospinal fluid volumes.…”