Natalia Trujillo

Action-verb processing in Parkinson’s disease: new pathways for motor–language coupling

Recent studies suggest that action-verb processing is particularly affected in early stage Parkinson’s disease (PD), highlighting the potential role of subcortical areas in language processing and in the semantic integration of actions. However, this disorder-related language impairment is frequently unrecognized by clinicians and often remains untreated. Early detection of action-language processing deficits could be critical for diagnosing and developing treatment strategies for PD. In this article, we review how action-verb processing is affected in PD and propose a model in which multiple and parallel frontotemporal circuits between the cortex and the basal ganglia provide the anatomic substrate for supporting action-language processing. We hypothesize that contextual coupling of action-language networks are partially dependent on cortical–subcortical integration, and not only on somatotopic motor cortical organization or in a mirror neuron system. This hypothesis is supported by both experimental and clinical evidence. Then, we identify further research steps that would help to determine the reliability of action-language impairments as an early marker of PD. Finally, theoretical implications for clinical assessment and for models of action-language interaction (action–perception cycle theories, mirror system models of language, and embodied cognition approaches to language) are discussed.

Subliminal presentation of other faces (but not own face) primes behavioral and evoked cortical processing of empathy for pain

Current research on empathy for pain emphasizes the overlap in the neural response between the first-hand experience of pain and its perception in others. However, recent studies suggest that the perception of the pain of others may reflect the processing of a threat or negative arousal rather than an automatic pro-social response. It can thus be suggested that pain processing of other-related, but not self-related, information could imply danger rather than empathy, due to the possible threat represented in the expressions of others (especially if associated with pain stimuli). To test this hypothesis, two experiments considering subliminal stimuli were designed. In Experiment 1, neutral and semantic pain expressions previously primed with own or other faces were presented to participants. When other-face priming was used, only the detection of semantic pain expressions was facilitated. In Experiment 2, pictures with pain and neutral scenarios previously used in ERP and fMRI research were used in a categorization task. Those pictures were primed with own or other faces following the same procedure as in Experiment 1 while ERPs were recorded. Early (N1) and late (P3) cortical responses between pain and no-pain were modulated only in the other-face priming condition. These results support the threat value of pain hypothesis and suggest the necessity for the inclusion of own- versus other-related information in future empathy for pain research.

Syntax, action verbs, action semantics, and object semantics in Parkinson's disease: Dissociability, progression, and executive influences

Several studies have recently shown that basal ganglia (BG) deterioration leads to distinctive impairments in the domains of syntax, action verbs, and action semantics. In particular, such disruptions have been repeatedly observed in Parkinsons disease (PD) patients. However, it remains unclear whether these deficits are language-specific and whether they are equally dissociable from other reported disturbances -viz., processing of object semantics. To address these issues, we administered linguistic, semantic, and executive function (EFs) tasks to two groups of non-demented PD patients, with and without mild cognitive impairment (PD-MCI and PD-nMCI, respectively). We compared these two groups with each other and with matched samples of healthy controls. Our results showed that PD patients exhibited linguistic and semantic deficits even in the absence of MCI. However, not all domains were equally related to EFs and MCI across samples. Whereas EFs predicted disturbances of syntax and object semantics in both PD-nMCI and PD-MCI, they had no impact on action-verb and action-semantic impairments in either group. Critically, patients showed disruptions of action-verb production and action semantics in the absence of MCI and without any executive influence, suggesting a sui generis deficit present since early stages of the disease. These findings indicate that varied language domains are differentially related to the BG, contradicting popular approaches to neurolinguistics.

How embodied is action language? Neurological evidence from motor diseases

Although motor-language coupling is now being extensively studied, its underlying mechanisms are not fully understood. In this sense, a crucial opposition has emerged between the non-representational and the representational views of embodiment. The former posits that action language is grounded on the non-brain motor system directly engaged by musculoskeletal activity - i.e., peripheral involvement of ongoing actions. Conversely, the latter proposes that such grounding is afforded by the brains motor system - i.e., activation of neural areas representing motor action. We addressed this controversy through the action-sentence compatibility effect (ACE) paradigm, which induces a contextual coupling of motor actions and verbal processing. ACEs were measured in three patient groups - early Parkinsons disease (EPD), neuromyelitis optica (NMO), and acute transverse myelitis (ATM) patients - as well as their respective healthy controls. NMO and ATM constitute models of injury to non-brain motor areas and the peripheral motor system, whereas EPD provides a model of brain motor system impairment. In our study, EPD patients exhibited impaired ACE and verbal processing relative to healthy participants, NMO, and ATM patients. These results indicate that the processing of action-related words is mainly subserved by a cortico-subcortical motor network system, thus supporting a brain-based embodied view on action language. More generally, our findings are consistent with contemporary perspectives for which action/verb processing depends on distributed brain networks supporting context-sensitive motor-language coupling.

Gesture influences the processing of figurative language in non-native speakers: ERP evidence.

Gestures should play a role in second language comprehension, given their importance in conveying contextual information. In this study, the N400 and the LPC were evaluated in a task involving the observation of videos showing utterances accompanied by gestures. Students studying advanced (G-High participants) and basic German (G-Low participants) as a second language were investigated. The utterance-gesture congruence and metaphoric meaning of content were manipulated during the task. As in previous ERP reports with native speakers, metaphorical expressions were sensitive to gestures. In G-Low participants, no modulation in the 300-500 ms window was observed, and only a modest effect was observed for the 500-700 ms window. More subtle differences of verbal expression were not processed in this group. Consistent with previous reports of the same paradigm with native speakers, the N400 from G-High group discriminated both congruent and incongruent gestures as well as literal and metaphorical sentences. Our results suggest that semantic processing is robust in the learning of a second language, although the amplitude modulation and latency of ERPs might depend on the speakers proficiency level.

Cortical dynamics and subcortical signatures of motor-language coupling in Parkinson’s disease

Impairments of action language have been documented in early stage Parkinson’s disease (EPD). The action-sentence compatibility effect (ACE) paradigm has revealed that EPD involves deficits to integrate action-verb processing and ongoing motor actions. Recent studies suggest that an abolished ACE in EPD reflects a cortico-subcortical disruption, and recent neurocognitive models highlight the role of the basal ganglia (BG) in motor-language coupling. Building on such breakthroughs, we report the first exploration of convergent cortical and subcortical signatures of ACE in EPD patients and matched controls. Specifically, we combined cortical recordings of the motor potential, functional connectivity measures, and structural analysis of the BG through voxel-based morphometry. Relative to controls, EPD patients exhibited an impaired ACE, a reduced motor potential, and aberrant frontotemporal connectivity. Furthermore, motor potential abnormalities during the ACE task were predicted by overall BG volume and atrophy. These results corroborate that motor-language coupling is mainly subserved by a cortico-subcortical network including the BG as a key hub. They also evince that action-verb processing may constitute a neurocognitive marker of EPD. Our findings suggest that research on the relationship between language and motor domains is crucial to develop models of motor cognition as well as diagnostic and intervention strategies.

Behavioral and Electrophysiological Correlates of Memory Binding Deficits in Patients at Different Risk Levels for Alzheimer's Disease

Deficits in visual short-term memory (VSTM) binding have been proposed as an early and specific marker for Alzheimers disease (AD). However, no studies have explored the neural correlates of this domain in clinical categories involving prodromal stages with different risk levels of conversion to AD. We assessed underlying electrophysiological modulations in patients with mild cognitive impairment (MCI), patients in the MCI stages of familial AD carrying the mutation E280A of the presenilin-1 gene (MCI-FAD), and healthy controls. Moreover, we compared the behavioral performance and neural correlates of both patient groups. Participants completed a change-detection VSTM task assessing recognition of changes between shapes or shape-color bindings, presented in two consecutive arrays (i.e., study and test) while event related potentials (ERPs) were recorded. Changes always occurred in the test array and consisted of new features replacing studied features (shape-only) or features swapping across items (shape-color binding). Both MCI and MCI-FAD patients performed worse than controls in the shape-color binding condition. Early electrophysiological activity (100-250 ms) was significantly reduced in both clinical groups, particularly over fronto-central and parieto-occipital regions. However, shape-color binding performance and their reduced neural correlates were similar between MCI and MCI-FAD. Our results support the validity of the VSTM binding test and their neural correlates in the early detection of AD and highlight the importance of studies comparing samples at different risk for AD conversion. The combined analysis of behavioral and ERP data gleaned with the VSTM binding task can offer a valuable memory biomarker for AD.

Language Deficits as a Preclinical Window into Parkinson’s Disease: Evidence from Asymptomatic Parkin and Dardarin Mutation Carriers

OBJECTIVES The worldwide spread of Parkinsons disease (PD) calls for sensitive and specific measures enabling its early (or, ideally, preclinical) detection. Here, we use language measures revealing deficits in PD to explore whether similar disturbances are present in asymptomatic individuals at risk for the disease. METHODS We administered executive, semantic, verb-production, and syntactic tasks to sporadic PD patients, genetic PD patients with PARK2 (parkin) or LRRK2 (dardarin) mutation, asymptomatic first-degree relatives of the latter with similar mutations, and socio-demographically matched controls. Moreover, to detect sui generis language disturbances, we ran analysis of covariance tests using executive functions as covariate. RESULTS The two clinical groups showed impairments in all measures, most of which survived covariation with executive functions. However, the key finding concerned asymptomatic mutation carriers. While these subjects showed intact executive, semantic, and action-verb production skills, they evinced deficits in a syntactic test with minimal working memory load. CONCLUSIONS We propose that this sui generis disturbance may constitute a prodromal sign anticipating eventual development of PD. Moreover, our results suggest that mutations on specific genes (PARK2 and LRRK2) compromising basal ganglia functioning may be subtly related to language-processing mechanisms. (JINS, 2017, 23, 150-158).

Emotional processing in Colombian ex-combatants and its relationship with empathy and executive functions

In this work, the neural correlates of emotional processing in Colombian ex-combatants with different empathy profiles were compared to normal controls matched for age, gender and educational level. Forty ex-combatants and 20 non ex-combatants were recruited for this study. Empathy levels as well as executive functions were measured. Empathy level was used to create three groups. Group 1 (G1) included ex-combatants with normal empathy scores, and Group 2 included ex-combatants with low scores on at least one empathy sub-scales. In control group (Ctrl), participants with no antecedents of being combatants and with normal scores in empathy were included. Age, gender, educational and intelligence quotients level were controlled among groups. event-related potentials (ERPs) were recorded while individuals performed an affective picture processing task that included positive, neutral and negative emotional stimuli, which elicit an early modulation of emotion categorization (Early Posterior Negativity (EPN)) and late evaluative process (LPP). EPN differences were found among affective categories, but no group effects were observed at this component. LPP showed a main effect of category and group (higher amplitudes in ex-combatants). There was an inverse correlation between empathy and executive functions scores and ERPs. Results are discussed according to the impact of emotional processing on empathy profile.

Social Cognitive Training Improves Emotional Processing and Reduces Aggressive Attitudes in Ex-combatants

Emotional processing (EP) is a complex cognitive function necessary to successfully adjust to social environments where we need to interpret and respond to cues that convey threat or reward signals. Ex-combatants have consistently shown atypical EP as well as poor social interactions. Available reintegration programs aim to facilitate the re-adaptation of ex-combatants to their communities. However, they do not incorporate actions to improve EP and to enhance cognitive-emotional regulation. The present study was aimed at evaluating the usefulness of an intervention focused on Social Cognitive Training (SCT), which was designed to equip ex-combatants enrolled in the Social Reintegration Route with EP and social cognition skills. A group of 31 ex-combatants (mean age of 37.2, 29 men) from Colombian illegal armed groups were recruited into this study. Of these, 16 were invited to take part in a SCT and the other continued with the conventional reintegration intervention. Both groups underwent 12 training sessions in a period 12–14 weeks. They were assessed with a comprehensive protocol which included Psychosocial, Behavioral, and Emotion Processing instruments. The scores on these instruments prior to and after the intervention were compared within and between groups. Both groups were matched at baseline. Ex-combatants receiving the SCT experienced significant improvements in EP and a reduction in aggressive attitudes, effects not observed in those continuing the conventional reintegration intervention. This is the first study that achieves such outcomes in such a population using SCT intervention. We discuss the implications of such results toward better social reintegration strategies.