Behavioral patterns and lesion sites associated with impaired processing of lexical and conceptual knowledge of actions

Rational adaptation in word production: Strong conceptual ability reduces the effect of lexical impairments on verb retrieval in aphasia

Language users rely on both linguistic and conceptual processing abilities to efficiently comprehend or produce language. According to the principle of rational adaptation, the degree to which a cognitive system relies on one process vs. another can change under different conditions or disease states with the goal of optimizing behavior. In this study, we investigated rational adaptation in reliance on linguistic versus conceptual processing in aphasia, an acquired disorder of language. In individuals living with aphasia, verb-retrieval impairments are a pervasive deficit that negatively impacts communicative function. As such, we examined evidence of adaptation in verb production, using parallel measures to index impairment in two of verb naming's critical subcomponents: conceptual and linguistic processing. These component processes were evaluated using a standardized assessment battery designed to contrast non-linguistic (picture input) and linguistic (word input) tasks of conceptual action knowledge. The results indicate that non-linguistic conceptual action processing can be impaired in people with aphasia and contributes to verb-retrieval impairments. Furthermore, relatively unimpaired conceptual action processing can ameliorate the influence of linguistic processing deficits on verb-retrieval impairments. These findings are consistent with rational adaptation accounts, indicating that conceptual processing plays a key role in language function and can be leveraged in rehabilitation to improve verb retrieval in adults with chronic aphasia.

No support for a causal role of primary motor cortex in construing meaning from language: An rTMS study

Embodied cognition theories predict a functional involvement of sensorimotor processes in language understanding. In a preregistered experiment, we tested this idea by investigating whether interfering with primary motor cortex (M1) activation can change how people construe meaning from action language. Participants were presented with sentences describing actions (e.g., "turning off the light") and asked to choose between two interpretations of their meaning, one more concrete (e.g., "flipping a switch") and another more abstract (e.g., "going to sleep"). Prior to this task, participants' M1 was disrupted using repetitive transcranial magnetic stimulation (rTMS). The results yielded strong evidence against the idea that M1-rTMS affects meaning construction (BF01 > 30). Additional analyses and control experiments suggest that the absence of effect cannot be accounted for by failure to inhibit M1, lack of construct validity of the task, or lack of power to detect a small effect. In sum, these results do not support a causal role for primary motor cortex in building meaning from action language.

Anomia: Deciphering Functional Neuroanatomy in Primary Progressive Aphasia Variants

Naming decline is one of the most common symptoms of primary progressive aphasia (PPA). Most studies on anomia in PPA are performed without taking into account PPA variants, especially for action naming. Only limited data are available for the neuroanatomical basis of anomia considering differences in the pathogenesis of PPAs. The aim of our study is to investigate the associations between anomia severity for both noun and verb naming and gray matter (GM) atrophy, as well as accompanying functional connectivity (FC) changes in three PPA variants. A total of 17 patients with non-fluent (nfvPPA), 11 with semantic (svPPA), and 9 with logopenic (lvPPA) PPA variants were included in the study and underwent cognitive/naming assessments and brain MRIs. Voxel-based morphometry was performed to evaluate GM volume. A resting-state functional MRI was applied to investigate FC changes in the identified GM areas. The study shows that different brain regions are involved in naming decline in each PPA variant with a predominantly temporal lobe involvement in svPPA, parietal lobe involvement in lvPPA, and frontal lobe involvement in nfvPPA. Separate data for object and action naming in PPA variants are provided. The obtained results mainly correspond to the current understanding of language processing and indicate that the evaluation of language impairments is preferable for each PPA variant separately. A further analysis of larger cohorts of patients is necessary to confirm these preliminary results.

Grounded Cognition Entails Linguistic Relativity: A Neglected Implication of a Major Semantic Theory

According to the popular Grounded Cognition Model (GCM), the sensory and motor features of concepts, including word meanings, are stored directly within neural systems for perception and action. More precisely, the core claim is that these concrete conceptual features reuse some of the same modality-specific representations that serve to categorize experiences involving the relevant kinds of objects and events. Research in semantic typology, however, has shown that word meanings vary significantly across the roughly 6500 languages in the world. I argue that this crosslinguistic semantic diversity has significant yet previously unrecognized theoretical consequences for the GCM. In particular, to accommodate the typological data, the GCM must assume that the concrete features of word meanings are not merely stored within sensory/motor brain systems, but are represented there in ways that are, to a nontrivial degree, language-specific. Moreover, it must assume that these conceptual representations are also activated during the nonlinguistic processing of the relevant kinds of objects and events (e.g., during visual perception and action planning); otherwise, they would not really be grounded, which is to say, embedded inside sensory/motor systems. Crucially, however, such activations would constitute what is traditionally called linguistic relativity-that is, the influence of language-specific semantic structures on other forms of cognition. The overarching aim of this paper is to elaborate this argument more fully and explore its repercussions. To that end, I discuss in greater detail the key aspects of the GCM, the evidence for crosslinguistic semantic diversity, pertinent work on linguistic relativity, the central claim that the GCM entails linguistic relativity, some initial supporting results, and some important limitations and future directions.

Concepts require flexible grounding

Research on semantic memory has a problem. On the one hand, a robust body of evidence implicates sensorimotor regions in conceptual processing. On the other hand, a different body of evidence implicates a modality independent semantic system. The standard solution to this tension is to posit a hub-and-spoke system with modality independent hubs and modality specific spokes. In this paper, I argue in support of an alternative view of grounding which remains committed to neural reenactment but emphasizes the multimodal and multilevel nature of the semantic system. This view is built upon the recognition that abstraction is a design feature of concepts. Semantic memory employs hierarchically structured representations to capture different degrees of abstraction. Grounding does not work the way that many embodied approaches have assumed.

Shared and distinct routes in speech and gesture imitation: Evidence from stroke

Dual-route models of high-level (praxis) actions distinguish between an "indirect" semantic route mediating meaningful gesture imitation, and a "direct" sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct route mediating non-word repetition. Although aphasia and limb apraxia frequently co-occur following left-hemisphere cerebrovascular accident (LCVA), it is unclear which aspects of these functional-neuroanatomic dual-route architectures are shared across praxis and language domains. This study focused on gesture imitation to test the hypothesis that semantic information (and portions of the indirect route) are shared across domains, whereas two distinct dorsal routes mediate sensory-motor mapping. Forty chronic LCVA and 17 neurotypical controls completed semantic memory and language tasks and imitated 3 types of gesture stimuli: (1) labeled/"named" meaningful, (2) unnamed meaningful, and (3) meaningless gestures. The comparison of accuracy between meaningless versus unnamed meaningful gestures examined the benefits of semantic information, while the comparison of unnamed meaningful versus named meaningful imitation examined additional benefits of linguistic cueing. Mixed-effects models examined group by task interaction effects on gesture ability. We found that for patients with LCVA, unnamed meaningful gestures were imitated more accurately than meaningless gestures, suggesting that semantic information was beneficial, but there was no benefit of labeling. Reduced benefit of semantic information on gesture accuracy was associated with lesions to inferior frontal and posterior temporal regions as well as semantic memory performance on a pictorial (non-gesture) task. In contrast, there was no relationship between meaningless gesture imitation and nonword repetition, indicating that measures of direct route performance are not associated across language and action. These results provide preliminary evidence that portions of the indirect semantic route are shared across the language and action domains, while two direct sensory-motor mapping routes mediate word repetition and gesture imitation.

Spatiotemporal Dynamics of Activation in Motor and Language Areas Suggest a Compensatory Role of the Motor Cortex in Second Language Processing

The involvement of the motor cortex in language understanding has been intensively discussed in the framework of embodied cognition. Although some studies have provided evidence for the involvement of the motor cortex in different receptive language tasks, the role that it plays in language perception and understanding is still unclear. In the present study, we explored the degree of involvement of language and motor areas in a visually presented sentence comprehension task, modulated by language proficiency (L1: native language, L2: second language) and linguistic abstractness (literal, metaphorical, and abstract). Magnetoencephalography data were recorded from 26 late Chinese learners of English. A cluster-based permutation F test was performed on the amplitude of the source waveform for each motor and language region of interest (ROI). Results showed a significant effect of language proficiency in both language and motor ROIs, manifested as overall greater involvement of language ROIs (short insular gyri and planum polare of the superior temporal gyrus) in the L1 than the L2 during 300-500 ms, and overall greater involvement of motor ROI (central sulcus) in the L2 than the L1 during 600-800 ms. We interpreted the over-recruitment of the motor area in the L2 as a higher demand for cognitive resources to compensate for the inadequate engagement of the language network. In general, our results indicate a compensatory role of the motor cortex in L2 understanding.

Linguistic signs in action: The neuropragmatics of speech acts

What makes human communication exceptional is the ability to grasp speaker's intentions beyond what is said verbally. How the brain processes communicative functions is one of the central concerns of the neurobiology of language and pragmatics. Linguistic-pragmatic theories define these functions as speech acts, and various pragmatic traits characterise them at the levels of propositional content, action sequence structure, related commitments and social aspects. Here I discuss recent neurocognitive studies, which have shown that the use of identical linguistic signs in conveying different communicative functions elicits distinct and ultra-rapid neural responses. Interestingly, cortical areas show differential involvement underlying various pragmatic features related to theory-of-mind, emotion and action for specific speech acts expressed with the same utterances. Drawing on a neurocognitive model, I posit that understanding speech acts involves the expectation of typical partner follow-up actions and that this predictive knowledge is immediately reflected in mind and brain.

Representation of motion concepts in occipitotemporal cortex: fMRI activation, decoding and connectivity analyses

Embodied theories of semantic cognition predict that brain regions involved in motion perception are engaged when people comprehend motion concepts expressed in language. Left lateral occipitotemporal cortex (LOTC) is implicated in both motion perception and motion concept processing but prior studies have produced mixed findings on which parts of this region are engaged by motion language. We scanned participants performing semantic judgements about sentences describing motion events and static events. We performed univariate analyses, multivariate pattern analyses (MVPA) and psychophysiological interaction (PPI) analyses to investigate the effect of motion on activity and connectivity in different parts of LOTC. In multivariate analyses that decoded whether a sentence described motion or not, the middle and posterior parts of LOTC showed above-chance level performance, with performance exceeding that of other brain regions. Univariate ROI analyses found the middle part of LOTC was more active for motion events than static ones. Finally, PPI analyses found that when processing motion events, the middle and posterior parts of LOTC (overlapping with motion perception regions), increased their connectivity with cognitive control regions. Taken together, these results indicate that the more posterior parts of LOTC, including motion perception cortex, respond differently to motion vs. static events. These findings are consistent with embodiment accounts of semantic processing, and suggest that understanding verbal descriptions of motion engages areas of the occipitotemporal cortex involved in perceiving motion.

Brain correlates of action word memory revealed by fMRI

Understanding language semantically related to actions activates the motor cortex. This activation is sensitive to semantic information such as the body part used to perform the action (e.g. arm-/leg-related action words). Additionally, motor movements of the hands/feet can have a causal effect on memory maintenance of action words, suggesting that the involvement of motor systems extends to working memory. This study examined brain correlates of verbal memory load for action-related words using event-related fMRI. Seventeen participants saw either four identical or four different words from the same category (arm-/leg-related action words) then performed a nonmatching-to-sample task. Results show that verbal memory maintenance in the high-load condition produced greater activation in left premotor and supplementary motor cortex, along with posterior-parietal areas, indicating that verbal memory circuits for action-related words include the cortical action system. Somatotopic memory load effects of arm- and leg-related words were observed, but only at more anterior cortical regions than was found in earlier studies employing passive reading tasks. These findings support a neurocomputational model of distributed action-perception circuits (APCs), according to which language understanding is manifest as full ignition of APCs, whereas working memory is realized as reverberant activity receding to multimodal prefrontal and lateral temporal areas.

The dorsal premotor cortex encodes the step-by-step planning processes for goal-directed motor behavior in humans

The dorsal premotor cortex (PMd) plays an essential role in visually guided goal-directed motor behavior. Although there are several planning processes for achieving goal-directed behavior, the separate neural processes are largely unknown. Here, we created a new visuo-goal task to investigate the step-by-step planning processes for visuomotor and visuo-goal behavior in humans. Using functional magnetic resonance imaging, we found activation in different portions of the bilateral PMd during each processing step. In particular, the activated area for rule-based visuomotor and visuo-goal mapping was located at the ventrorostral portion of the bilateral PMd, that for action plan specification was at the dorsocaudal portion of the left PMd, that for transformation was at the rostral portion of the left PMd, and that for action preparation was at the caudal portion of the bilateral PMd. Thus, the left PMd was involved throughout all of the processes, but the right PMd was involved only in rule-based visuomotor and visuo-goal mapping and action preparation. The locations related to each process were generally spatially separated from each other, but they overlapped partially. These findings revealed that there are functional subregions in the bilateral PMd in humans and these subregions form a functional gradient to achieve goal-directed behavior.

What matters is the underlying experience: Similar motor responses during processing observed hand actions and hand-related verbs

It is well-accepted that processing observed actions involves at some extent the same neural mechanisms responsible for action execution. More recently, it has been forwarded that also the processing of verbs expressing a specific motor content is subserved by the neural mechanisms allowing individuals to perform the content expressed by that linguistic material. This view is also known as embodiment and contrasts with a more classical approach to language processing that considers it as amodal. In the present study, we used a go/no-go paradigm, in which participants were requested to respond to real words and pictures and refrain from responding when presented stimuli were pseudowords and scrambled images. Real stimuli included pictures depicting hand- and foot-related actions and verbs expressing hand- and foot-related actions. We, therefore, directly compared the modulation of hand motor responses during the observation of actions and the presentation of verbs, expressing actions in the same category. The results have shown that participants gave slower hand motor responses during the observation of hand actions and the processing of hand-related verbs as than observed foot actions and related verbs. These findings support embodiment showing that whatever the modality of presentation (observed action or verb), the modulation of hand motor responses was similar, thus suggesting that processing seen actions and related verbs shares common mechanisms most likely involving the motor system and the underlying motor experience.

The noun-verb distinction

The comparison between nouns and verbs has been a topic of interest for many researchers over the last 50 years. This comparison, and subsequent behavioral and (partly) anatomic dissociation, has allowed researchers to delve into many topics including the behavioral architecture of the language system and its neural correlates, the underlying nature of the linguistic impairment in individuals with different neurologic disorders, the assessment of language treatment protocols, and the proposal of new protocols aimed to protect the language system of individuals undergoing surgery for brain tumors and epilepsy. Specific to the left temporal lobe, classic accounts have shown its relevance for the processing of nouns and less for the processing of verbs. Nonetheless, more recent accounts indicate that different areas in the left temporal lobe can subserve different functions for the processing of both nouns and verbs. In this chapter, we outlined an overview of key findings of the study of nouns and verbs, with a particular focus on the left temporal lobe. This chapter contextualizes the literature on category-specific impairments and neural correlates of nouns and verbs with linguistic and psycholinguistic theories, and provides new ways to investigate and understand the intricacies of this comparison.

Motor Cortex Causally Contributes to Vocabulary Translation following Sensorimotor-Enriched Training

The role of the motor cortex in perceptual and cognitive functions is highly controversial. Here, we investigated the hypothesis that the motor cortex can be instrumental for translating foreign language vocabulary. Human participants of both sexes were trained on foreign language (L2) words and their native language translations over 4 consecutive days. L2 words were accompanied by complementary gestures (sensorimotor enrichment) or pictures (sensory enrichment). Following training, participants translated the auditorily presented L2 words that they had learned. During translation, repetitive transcranial magnetic stimulation was applied bilaterally to a site within the primary motor cortex (Brodmann area 4) located in the vicinity of the arm functional compartment. Responses within the stimulated motor region have previously been found to correlate with behavioral benefits of sensorimotor-enriched L2 vocabulary learning. Compared to sham stimulation, effective perturbation by repetitive transcranial magnetic stimulation slowed down the translation of sensorimotor-enriched L2 words, but not sensory-enriched L2 words. This finding suggests that sensorimotor-enriched training induced changes in L2 representations within the motor cortex, which in turn facilitated the translation of L2 words. The motor cortex may play a causal role in precipitating sensorimotor-based learning benefits, and may directly aid in remembering the native language translations of foreign language words following sensorimotor-enriched training. These findings support multisensory theories of learning while challenging reactivation-based theories.SIGNIFICANCE STATEMENT Despite the potential for sensorimotor enrichment to serve as a powerful tool for learning in many domains, its underlying brain mechanisms remain largely unexplored. Using transcranial magnetic stimulation and a foreign language (L2) learning paradigm, we found that sensorimotor-enriched training can induce changes in L2 representations within the motor cortex, which in turn causally facilitate the translation of L2 words. The translation of recently acquired L2 words may therefore rely not only on auditory information stored in memory or on modality-independent L2 representations, but also on the sensorimotor context in which the words have been experienced.

Neural underpinnings of morality judgment and moral aesthetic judgment

Morality judgment usually refers to the evaluation of moral behavior`s ability to affect others` interests and welfare, while moral aesthetic judgment often implies the appraisal of moral behavior's capability to provide aesthetic pleasure. Both are based on the behavioral understanding. To our knowledge, no study has directly compared the brain activity of these two types of judgments. The present study recorded and analyzed brain activity involved in the morality and moral aesthetic judgments to reveal whether these two types of judgments differ in their neural underpinnings. Results reveled that morality judgment activated the frontal, parietal and occipital cortex previously reported for motor representations of behavior. Evaluation of goodness and badness showed similar patterns of activation in these brain regions. In contrast, moral aesthetic judgment elicited specific activations in the frontal, parietal and temporal cortex proved to be involved in the behavioral intentions and emotions. Evaluation of beauty and ugliness showed similar patterns of activation in these brain regions. Our findings indicate that morality judgment and moral aesthetic judgment recruit different cortical networks that might decode others' behaviors at different levels. These results contribute to further understanding of the essence of the relationship between morality judgment and aesthetic judgment.

Inflection across Categories: Tracking Abstract Morphological Processing in Language Production with MEG

Coherent language production requires that speakers adapt words to their grammatical contexts. A fundamental challenge in establishing a functional delineation of this process in the brain is that each linguistic process tends to correlate with numerous others. Our work investigated the neural basis of morphological inflection by measuring magnetoencephalography during the planning of inflected and uninflected utterances that varied across several linguistic dimensions. Results reveal increased activity in the left lateral frontotemporal cortex when inflection is planned, irrespective of phonological specification, syntactic context, or semantic type. Additional findings from univariate and connectivity analyses suggest that the brain distinguishes between different types of inflection. Specifically, planning noun and verb utterances requiring the addition of the suffix -s elicited increased activity in the ventral prefrontal cortex. A broadly distributed effect of syntactic context (verb vs. noun) was also identified. Results from representational similarity analysis indicate that this effect cannot be explained in terms of word meaning. Together, these results 1) offer evidence for a neural representation of abstract inflection that separates from other stimulus properties and 2) challenge theories that emphasize semantic content as a source of verb/noun processing differences.

Dissociating nouns and verbs in temporal and perisylvian networks: Evidence from neurodegenerative diseases

Naming of nouns and verbs can be selectively impaired in neurological disorders, but the specificity of the neural and cognitive correlates of such dissociation remains unclear. Functional imaging and stroke research sought to identify cortical regions selectively recruited for nouns versus verbs, yet findings are inconsistent. The present study investigated this issue in neurodegenerative diseases known to selectively affect different brain networks, thus providing new critical evidence of network specificity. We examined naming performances on nouns and verbs in 146 patients with different neurodegenerative syndromes (Primary Progressive Aphasia - PPA, Alzheimer's disease - AD, and behavioral variant Frontotemporal Dementia - FTD) and 30 healthy adults. We then correlated naming scores with MRI-derived cortical thickness values as well as with performances in semantic and syntactic tasks, across all subjects. Results indicated that patients with the semantic variant PPA named significantly fewer nouns than verbs. Instead, nonfluent/agrammatic PPA patients named fewer verbs than nouns. Across all subjects, performance on nouns (adjusted for verbs) specifically correlated with cortical atrophy in left anterior temporal regions, and performance on verbs (adjusted for nouns) with atrophy in left inferior and middle frontal, inferior parietal and posterior temporal regions. Furthermore, lower lexical-semantic abilities correlated with deficits in naming both nouns and verbs, while lower syntactic abilities only correlated with naming verbs. Our results show that different neural and cognitive mechanisms underlie naming of specific grammatical categories in neurodegenerative diseases. Importantly, our findings showed that verb processing depends on a widespread perisylvian networks, suggesting that some regions might be involved in processing different types of action knowledge. These findings have important implications for early differential diagnosis of neurodegenerative disorders.

From letters to composed concepts: A magnetoencephalography study of reading

Language comprehension requires the recognition of individual words and the combination of their meanings to yield complex concepts or interpretations. This combinatory process often requires the insertion of unstated semantic material between words, based on thematic or feature knowledge. For example, the phrase horse barn is not interpreted as a blend of a horse and a barn, but specifically a barn where horses are kept. Previous neuroscientific evidence suggests that left posterior and anterior temporal cortex underpin thematic and feature‐based concept knowledge, respectively, but much remains unclear about how these areas contribute to combinatory language processing. Using magnetoencephalography, we contrasted source‐localized responses to modifier‐noun phrases involving thematic relations versus feature modifications, while also examining how lower‐level orthographic processing fed composition. Participants completed three procedures examining responses to letter‐strings, adjective‐noun phrases, and noun–noun combinations that varied the semantic relations between words. We found that sections of the left anterior temporal lobe, posterior temporal lobe, and cortex surrounding the angular gyrus were all engaged in the minimal composition of adjective‐noun phrases, a more distributed network than in most prior studies of minimal composition. Of these regions, only the left posterior temporal lobe was additionally sensitive to implicit thematic relations between composing words, suggesting that it houses a specialized relational processing component in a wider composition network. We additionally identified a left occipitotemporal progression from orthographic to lexical processing, feeding ventral anterior areas engaged in the combination of word meanings. Finally, by examining source signal leakage, we characterized the degree to which these responses could be distinguished from one another using source estimation.

What modulates the Mirror Neuron System during action observation?: Multiple factors involving the action, the actor, the observer, the relationship between actor and observer, and the context

Seeing an agent perform an action typically triggers a motor simulation of that action in the observer's Mirror Neuron System (MNS). Over the past few years, it has become increasingly clear that during action observation the patterns and strengths of responses in the MNS are modulated by multiple factors. The first aim of this paper is therefore to provide the most comprehensive survey to date of these factors. To that end, 22 distinct factors are described, broken down into the following sets: six involving the action; two involving the actor; nine involving the observer; four involving the relationship between actor and observer; and one involving the context. The second aim is to consider the implications of these findings for four prominent theoretical models of the MNS: the Direct Matching Model; the Predictive Coding Model; the Value-Driven Model; and the Associative Model. These assessments suggest that although each model is supported by a wide range of findings, each one is also challenged by other findings and relatively unaffected by still others. Hence, there is now a pressing need for a richer, more inclusive model that is better able to account for all of the modulatory factors that have been identified so far.

HD-tDCS over motor cortex facilitates figurative and literal action sentence processing

The extent to which action and perception systems of the brain are involved in semantic comprehension remains controversial. Whether figurative language, such as metaphors and idioms, is grounded in sensory-motor systems is especially contentious. Here, we used high-definition transcranial direct current stimulation (HD-tDCS) in healthy adults to examine the role of the left-hemisphere motor cortex during the comprehension of action sentences, relative to comprehension of sentences with visual verbs. Action sentences were divided into three types: literal, metaphoric, or idiomatic. This allowed us to ask whether processing of action verbs used in figurative contexts relies on motor cortex. The results revealed that action sentence comprehension response times were facilitated relative to the visual sentence control. Significant interaction relative to visual sentences was observed for literal, metaphoric, and idiomatic action sentences with HD-tDCS of the motor cortex. These results suggest that the left motor cortex is functionally involved in action sentence comprehension. Furthermore, this involvement exists when the action content of the sentences is figurative, for both idiomatic and metaphoric cases. The results provide evidence for functional links between conceptual and action systems of the brain.

Neural regions underlying object and action naming: Complementary evidence from acute stroke and primary progressive aphasia

BACKGROUND

Naming impairment is commonly noted in individuals with aphasia. However, object naming receives more attention than action naming. Furthermore, most studies include participants with aphasia due to only one aetiology, commonly stroke. We developed a new assessment, the Hopkins Action Naming Assessment (HANA), to evaluate action naming impairments.

AIMS

Our aims were to show that the HANA is a useful tool that can (1) identify action naming impairments and (2) be used to investigate the neural substrates underlying naming. We paired the HANA with the Boston Naming Test (BNT) to compare action and object naming. We considered participants with aphasia due to primary progressive aphasia (PPA) or acute left hemisphere stroke to provide a more comprehensive picture of brain-behaviour relationships critical for naming. Behaviourally, we hypothesised that there would be a double dissociation between object and action naming performance. Neuroanatomically, we hypothesised that different neural substrates would be implicated in object vs. action naming and that different lesion-deficit associations would be identified in participants with PPA vs. acute stroke.

METHODS & PROCEDURES

Participants (N=138 with PPA, N=37 with acute stroke) completed the BNT and HANA. Behavioural performance was compared. A subset of participants (N=31 with PPA, N=37 with acute stroke) provided neuroimaging data. The whole brain was automatically segmented into regions of interest (ROIs). For participants with PPA, the image variables were the ROI volumes, normalised by the brain volume. For participants with acute stroke, the image variables were the percentage of each ROI affected by the lesion. The relationship between ROIs likely to be involved in naming performance was modelled with LASSO regression.

OUTCOMES & RESULTS

Behavioural results showed a double dissociation in performance: in each group, some participants displayed intact performance relative to healthy controls on actions but not objects and/or significantly better performance on actions than objects, while others showed the opposite pattern. These results support the need to assess both objects and actions when evaluating naming deficits. Neuroimaging results identified different regions associated with object vs. action naming, implicating overlapping but distinct networks of regions. Furthermore, results differed for participants with PPA vs. acute stroke, indicating that critical information may be missed when only one aetiology is considered.

CONCLUSIONS

Overall, the study provides a more comprehensive picture of the neural bases of naming, underscoring the importance of assessing both objects and actions and considering different aetiologies of damage. It demonstrates the utility of the HANA.

White-Matter Neuroanatomical Predictors of Aphasic Verb Retrieval

Background: Current neurocognitive models of language function have been primarily built from evidence regarding object naming, and their hypothesized white-matter circuit mechanisms tend to be coarse grained. Methods: In this cross-sectional, observational study, we used novel correlational tractography to assess the white-matter circuit mechanism behind verb retrieval, measured through action picture-naming performance in adults with chronic aphasia. Results: The analysis identified tracts implicated in current neurocognitive dual-stream models of language function, including the left inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, and arcuate fasciculus. However, the majority of tracts associated with verb retrieval were not ones included in dual-stream models of language function. Instead, they were projection pathways that connect frontal and parietal cortices to subcortical regions associated with motor functions, including the left corticothalamic pathway, frontopontine tract, parietopontine tract, corticostriatal pathway, and corticospinal tract. Conclusions: These results highlight that corticosubcortical projection pathways implicated in motor functions may be importantly related to language function. This finding is consistent with grounded accounts of cognition and may furthermore inform neurocognitive models. Impact statement This study suggests that in addition to traditional dual-stream language fiber tracts, the integrity of projection pathways that connect frontal and parietal cortices to subcortical motor regions may be critically associated with verb-retrieval impairments in adults with aphasia. This finding challenges neurological models of language function.

Avoiding Conflict: When Speaker Coordination Does Not Require Conceptual Agreement

In this paper we discuss the socialization hypothesis-the idea that speakers of the same (linguistic) community should share similar concepts given that they are exposed to similar environments and operate in highly-coordinated social contexts-and challenge the fact that it is assumed to constitute a prerequisite to successful communication. We do so using distributional semantic models of meaning (DSMs) which create lexical representations via latent aggregation of co-occurrence information between words and contexts. We argue that DSMs constitute particularly adequate tools for exploring the socialization hypothesis given that 1) they provide full control over the notion of background environment, formally characterized as the training corpus from which distributional information is aggregated; and 2) their geometric structure allows for exploiting alignment-based similarity metrics to measure inter-subject alignment over an entire semantic space, rather than a set of limited entries. We propose to model coordination between two different DSMs trained on two distinct corpora as dimensionality selection over a dense matrix obtained via Singular Value Decomposition This approximates an ad-hoc coordination scenario between two speakers as the attempt to align their similarity ratings on a set of word pairs. Our results underline the specific way in which linguistic information is spread across singular vectors, and highlight the need to distinguish agreement from mere compatibility in alignment-based notions of conceptual similarity. Indeed, we show that compatibility emerges from idiosyncrasy so that the unique and distinctive aspects of speakers' background experiences can actually facilitate-rather than impede-coordination and communication between them. We conclude that the socialization hypothesis may constitute an unnecessary prerequisite to successful communication and that, all things considered, communication is probably best formalized as the cooperative act of avoiding conflict, rather than maximizing agreement.

Some evidence on Gerstmann's syndrome: A case study on a variant of the clinical disorder

We describe the case of a bilingual patient with persistent symptoms largely, although not fully, consistent with those that are usually reported in Gerstmann's syndrome. Twenty months after a spontaneous primary intracranial hemorrhage, the patient was evaluated with a series of neuropsychological tasks and underwent an MRI investigation based on Diffusion Tensor Imaging probabilistic tractography. The patient suffered from dysgraphia (difficulty in the access to the graphemic representation of letter forms), autotopoagnosia (difficulties in locating body parts on verbal command), right-left confusion (difficulties in localizing right and left side of symmetrical body parts), and number processing/calculation impairments (predominant difficulties on transcoding tasks). Probabilistic tractography revealed a relatively spared superior longitudinal fasciculus and severe damage to the subcortical white matter connecting the angular gyrus with other parietal regions, such as the intraparietal sulcus and the supramarginal gyrus. Within the framework of the contemporary cognitive accounts of Gerstmann's syndrome, the case supports the assumption of an anatomical intraparietal disconnection more than a functional Grundstörung (core impairment).

Towards Strong Inference in Research on Embodiment - Possibilities and Limitations of Causal Paradigms

A central question in the cognitive sciences is which role embodiment plays for high-level cognitive functions, such as conceptual processing. Here, we propose that one reason why progress regarding this question has been slow is a lacking focus on what Platt (1964) called “strong inference”. Strong inference is possible when results from an experimental paradigm are not merely consistent with a hypothesis, but they provide decisive evidence for one particular hypothesis compared to competing hypotheses. We discuss how causal paradigms, which test the functional relevance of sensory-motor processes for high-level cognitive functions, can move the field forward. In particular, we explore how congenital sensory-motor disorders, acquired sensory-motor deficits, and interference paradigms with healthy participants can be utilized as an opportunity to better understand the role of sensory experience in conceptual processing. Whereas all three approaches can bring about valuable insights, we highlight that the study of congenitally and acquired sensorimotor disorders is particularly effective in the case of conceptual domains with strong unimodal basis (e.g., colors), whereas interference paradigms with healthy participants have a broader application, avoid many of the practical and interpretational limitations of patient studies, and allow a systematic and step-wise progressive inference approach to causal mechanisms.

Common and distinct neural substrates of sentence production and comprehension

Functional neuroimaging and lesion-symptom mapping investigations implicate a left frontal-temporal-parietal network for sentence processing. The majority of studies have focused on sentence comprehension, with fewer in the domain of sentence production, which have not fully elucidated overlapping and/or unique brain structures associated with the two domains, particularly for sentences with noncanonical word order. Using voxel-based lesion symptom mapping (VLSM) we examined the relationship between lesions within the left hemisphere language network and both sentence comprehension and production of simple and complex syntactic structures in 76 participants with chronic stroke-induced aphasia. Results revealed shared regions across domains in the anterior and posterior superior temporal gyri (aSTG, pSTG), and the temporal pole (adjusted for verb production/comprehension). Additionally, comprehension was associated with lesions in the anterior and posterior middle temporal gyri (aMTG, pMTG), the MTG temporooccipital regions, SMG/AG, central and parietal operculum, and the insula. Subsequent VLSM analyses (production versus comprehension) revealed critical regions associated with each domain: anterior temporal lesions were associated with production; posterior temporo-parietal lesions were associated with comprehension, implicating important roles for regions within the ventral and dorsal stream processing routes, respectively. Processing of syntactically complex, noncanonical (adjusted for canonical), sentences was associated with damage to the pSTG across domains, with additional damage to the pMTG and IPL associated with impaired sentence comprehension, suggesting that the pSTG is crucial for computing noncanonical sentences across domains and that the pMTG, and IPL are necessary for re-analysis of thematic roles as required for resolution of long-distance dependencies. These findings converge with previous studies and extend our knowledge of the neural mechanisms of sentence comprehension to production, highlighting critical regions associated with both domains, and further address the mechanism engaged for syntactic computation, controlled for the contribution of verb processing.

Oscillatory and structural signatures of language plasticity in brain tumor patients: A longitudinal study

Recent evidence suggests that damage to the language network triggers its functional reorganization. Yet, the spectro‐temporal fingerprints of this plastic rearrangement and its relation to anatomical changes is less well understood. Here, we combined magnetoencephalographic recordings with a proxy measure of white matter to investigate oscillatory activity supporting language plasticity and its relation to structural reshaping. First, cortical dynamics were acquired in a group of healthy controls during object and action naming. Results showed segregated beta (13–28 Hz) power decreases in left ventral and dorsal pathways, in a time‐window associated to lexico‐semantic processing (~250–500 ms). Six patients with left tumors invading either ventral or dorsal regions performed the same naming task before and 3 months after surgery for tumor resection. When longitudinally comparing patients' responses we found beta compensation mimicking the category‐based segregation showed by controls, with ventral and dorsal damage leading to selective compensation for object and action naming, respectively. At the structural level, all patients showed preoperative changes in white matter tracts possibly linked to plasticity triggered by tumor growth. Furthermore, in some patients, structural changes were also evident after surgery and showed associations with longitudinal changes in beta power lateralization toward the contralesional hemisphere. Overall, our findings support the existence of anatomo‐functional dependencies in language reorganization and highlight the potential role of oscillatory markers in tracking longitudinal plasticity in brain tumor patients. By doing so, they provide valuable information for mapping preoperative and postoperative neural reshaping and plan surgical strategies to preserve language function and patient's quality of life.

Multimodal comprehension in left hemisphere stroke patients

Hand gestures, imagistically related to the content of speech, are ubiquitous in face-to-face communication. Here we investigated people with aphasia's (PWA) processing of speech accompanied by gestures using lesion-symptom mapping. Twenty-nine PWA and 15 matched controls were shown a picture of an object/action and then a video-clip of a speaker producing speech and/or gestures in one of the following combinations: speech-only, gesture-only, congruent speech-gesture, and incongruent speech-gesture. Participants' task was to indicate, in different blocks, whether the picture and the word matched (speech task), or whether the picture and the gesture matched (gesture task). Multivariate lesion analysis with Support Vector Regression Lesion-Symptom Mapping (SVR-LSM) showed that benefit for congruent speech-gesture was associated with 1) lesioned voxels in anterior fronto-temporal regions including inferior frontal gyrus (IFG), and sparing of posterior temporal cortex and lateral temporal-occipital regions (pTC/LTO) for the speech task, and 2) conversely, lesions to pTC/LTO and sparing of anterior regions for the gesture task. The two tasks did not share overlapping voxels. Costs from incongruent speech-gesture pairings were associated with lesioned voxels in these same anterior (for the speech task) and posterior (for the gesture task) regions, but crucially, also shared voxels in superior temporal gyrus (STG) and middle temporal gyrus (MTG), including the anterior temporal lobe. These results suggest that IFG and pTC/LTO contribute to extracting semantic information from speech and gesture, respectively; however, they are not causally involved in integrating information from the two modalities. In contrast, regions in anterior STG/MTG are associated with performance in both tasks and may thus be critical to speech-gesture integration. These conclusions are further supported by associations between performance in the experimental tasks and performance in tests assessing lexical-semantic processing and gesture recognition.

Enhancing Motor Brain Activity Improves Memory for Action Language: A tDCS Study

The embodied cognition approach to linguistic meaning posits that action language understanding is grounded in sensory-motor systems. However, evidence that the human motor cortex is necessary for action language memory is meager. To address this issue, in two groups of healthy individuals, we perturbed the left primary motor cortex (M1) by means of either anodal or cathodal transcranial direct current stimulation (tDCS), before participants had to memorize lists of manual action and attentional sentences. In each group, participants received sham and active tDCS in two separate sessions. Following anodal tDCS (a-tDCS), participants improved the recall of action sentences compared with sham tDCS. No similar effects were detected following cathodal tDCS (c-tDCS). Both a-tDCS and c-tDCS induced variable changes in motor excitability, as measured by motor-evoked potentials induced by transcranial magnetic stimulation. Remarkably, across groups, action-specific memory improvements were positively predicted by changes in motor excitability. We provide evidence that excitatory modulation of the motor cortex selectively improves performance in a task requiring comprehension and memory of action sentences. These findings indicate that M1 is necessary for accurate processing of linguistic meanings and thus provide causal evidence that high-order cognitive functions are grounded in the human motor system.

Distinct fronto-temporal substrates of distributional and taxonomic similarity among words: evidence from RSA of BOLD signals

A class of semantic theories defines concepts in terms of statistical distributions of lexical items, basing meaning on vectors of word co-occurrence frequencies. A different approach emphasizes abstract hierarchical taxonomic relationships among concepts. However, the functional relevance of these different accounts and how they capture information-encoding of lexical meaning in the brain still remains elusive. We investigated to what extent distributional and taxonomic models explained word-elicited neural responses using cross-validated representational similarity analysis (RSA) of functional magnetic resonance imaging (fMRI) and model comparisons. Our findings show that the brain encodes both types of semantic information, but in distinct cortical regions. Posterior middle temporal regions reflected lexical-semantic similarity based on hierarchical taxonomies, in coherence with the action-relatedness of specific semantic word categories. In contrast, distributional semantics best predicted the representational patterns in left inferior frontal gyrus (LIFG, BA 47). Both representations coexisted in the angular gyrus supporting semantic binding and integration. These results reveal that neuronal networks with distinct cortical distributions across higher-order association cortex encode different representational properties of word meanings. Taxonomy may shape long-term lexical-semantic representations in memory consistently with the sensorimotor details of semantic categories, whilst distributional knowledge in the LIFG (BA 47) may enable semantic combinatorics in the context of language use. Our approach helps to elucidate the nature of semantic representations essential for understanding human language.

A shared neural substrate for action verbs and observed actions in human posterior parietal cortex

High-level sensory and motor cortical areas are activated when processing the meaning of language, but it is unknown whether, and how, words share a neural substrate with corresponding sensorimotor representations. We recorded from single neurons in human posterior parietal cortex (PPC) while participants viewed action verbs and corresponding action videos from multiple views. We find that PPC neurons exhibit a common neural substrate for action verbs and observed actions. Further, videos were encoded with mixtures of invariant and idiosyncratic responses across views. Action verbs elicited selective responses from a fraction of these invariant and idiosyncratic neurons, without preference, thus associating with a statistical sampling of the diverse sensory representations related to the corresponding action concept. Controls indicated that the results are not the product of visual imagery or arbitrary learned associations. Our results suggest that language may activate the consolidated visual experience of the reader.

Challenges and Opportunities for Grounding Cognition

According to the grounded perspective, cognition emerges from the interaction of classic cognitive processes with the modalities, the body, and the environment. Rather than being an autonomous impenetrable module, cognition incorporates these other domains intrinsically into its operation. The Situated Action Cycle offers one way of understanding how the modalities, the body, and the environment become integrated to ground cognition. Seven challenges and opportunities are raised for this perspective: (1) How does cognition emerge from the Situated Action Cycle and in turn support it? (2) How can we move beyond simply equating embodiment with action, additionally establishing how embodiment arises in the autonomic, neuroendocrine, immune, cardiovascular, respiratory, digestive, and integumentary systems? (3) How can we better understand the mechanisms underlying multimodal simulation, its functions across the Situated Action Cycle, and its integration with other representational systems? (4) How can we develop and assess theoretical accounts of symbolic processing from the grounded perspective (perhaps using the construct of simulators)? (5) How can we move beyond the simplistic distinction between concrete and abstract concepts, instead addressing how concepts about the external and internal worlds pattern to support the Situated Action Cycle? (6) How do individual differences emerge from different populations of situational memories as the Situated Action Cycle manifests itself differently across individuals? (7) How can constructs from grounded cognition provide insight into the replication and generalization crises, perhaps from a quantum perspective on mechanisms (as exemplified by simulators).

Functional linguistic specificity of the left frontal aslant tract for spontaneous speech fluency: Evidence from intraoperative language mapping

The left frontal aslant tract (FAT) has been proposed to be relevant for language, and specifically for spontaneous speech fluency. However, there is missing causal evidence that stimulation of the FAT affects spontaneous speech, and not language production in general. We present a series of 12 neurosurgical cases with awake language mapping of the cortex near the left FAT. Tasks for language mapping included the commonly used action picture naming, and sentence completion, tapping more specifically into spontaneous speech. A task dissociation was found in 10 participants: while being stimulated on specific sites, they were able to name a picture but could not complete a sentence. Overlaying of these sites on preoperative white-matter tract reconstructions revealed that in each individual case they were located on cortical terminations of the FAT. This corroborates the language functional specificity of the left FAT as a tract underlying fluent spontaneous speech.

Structural Disconnection of the Tool Use Network after Left Hemisphere Stroke Predicts Limb Apraxia Severity

Producing a tool use gesture is a complex process drawing upon the integration of stored knowledge of tools and their associated actions with sensory-motor mechanisms supporting the planning and control of hand and arm actions. Understanding how sensory-motor systems in parietal cortex interface with semantic representations of actions and objects in the temporal lobe remains a critical issue and is hypothesized to be a key determinant of the severity of limb apraxia, a deficit in producing skilled action after left hemisphere stroke. We used voxel-based and connectome-based lesion-symptom mapping with data from 57 left hemisphere stroke participants to assess the lesion sites and structural disconnection patterns associated with poor tool use gesturing. We found that structural disconnection among the left inferior parietal lobule, lateral and ventral temporal cortices, and middle and superior frontal gyri predicted the severity of tool use gesturing performance. Control analyses demonstrated that reductions in right-hand grip strength were associated with motor system disconnection, largely bypassing regions supporting tool use gesturing. Our findings provide evidence that limb apraxia may arise, in part, from a disconnection between conceptual representations in the temporal lobe and mechanisms enabling skilled action production in the inferior parietal lobule.

Above and beyond "Above and beyond the concrete"

The commentaries address our view of abstraction, our ontology of abstract entities, and our account of predictive cognition as relying on relatively concrete simulation or relatively abstract theory-based inference. These responses revisit classic questions concerning mental representation and abstraction in the context of current models of predictive cognition. The counter arguments to our article echo: constructivist theories of knowledge, "neat" approaches in artificial intelligence and decision theory, neo-empiricist models of concepts, and externalist views of cognition. We offer several empirical predictions that address points of contention and that highlight the generative potential of our model.

Brain Activation During Conceptual Processing of Action and Sound Verbs

Grounded cognition approaches to conceptual representations postulate a close link between conceptual knowledge and the sensorimotor brain systems. The present fMRI study tested, whether a feature-specific representation of concepts, as previously demonstrated for nouns, can also be found for action- and sound-related verbs. Participants were presented with action- and soundrelated verbs along with pseudoverbs while performing a lexical decision task. Sound-related verbs activated auditory areas in the temporal cortex, whereas action-related verbs activated brain regions in the superior frontal gyrus and the cerebellum, albeit only at a more liberal threshold. This differential brain activation during conceptual verb processing partially overlapped with or was adjacent to brain regions activated during the functional localizers probing sound perception or action execution. Activity in brain areas involved in the processing of action information was parametrically modulated by ratings of action relevance. Comparisons of action- and sound-related verbs with pseudoverbs revealed activation for both verb categories in auditory and motor areas. In contrast to proposals of strong grounded cognition approaches, our study did not demonstrate a considerable overlap of activations for action- and sound-related verbs and for the corresponding functional localizer tasks. However, in line with weaker variants of grounded cognition theories, the differential activation pattern for action- and sound-related verbs was near corresponding sensorimotor brain regions depending on conceptual feature relevance. Possibly, action-sound coupling resulted in a mutual activation of the motor and the auditory system for both action- and sound-related verbs, thereby reducing the effect sizes for the differential contrasts.

Task-Dependent Recruitment of Modality-Specific and Multimodal Regions during Conceptual Processing

Conceptual knowledge is central to cognitive abilities such as word comprehension. Previous neuroimaging evidence indicates that concepts are at least partly composed of perceptual and motor features that are represented in the same modality-specific brain regions involved in actual perception and action. However, it is unclear to what extent the retrieval of perceptual-motor features and the resulting engagement of modality-specific regions depend on the concurrent task. To address this issue, we measured brain activity in 40 young and healthy participants using functional magnetic resonance imaging, while they performed three different tasks-lexical decision, sound judgment, and action judgment-on words that independently varied in their association with sounds and actions. We found neural activation for sound and action features of concepts selectively when they were task-relevant in brain regions also activated during auditory and motor tasks, respectively, as well as in higher-level, multimodal regions which were recruited during both sound and action feature retrieval. For the first time, we show that not only modality-specific perceptual-motor areas but also multimodal regions are engaged in conceptual processing in a flexible, task-dependent fashion, responding selectively to task-relevant conceptual features.

A unified neurocognitive model of semantics language social behaviour and face recognition in semantic dementia

The anterior temporal lobes (ATL) have become a key brain region of interest in cognitive neuroscience founded upon neuropsychological investigations of semantic dementia (SD). The purposes of this investigation are to generate a single unified model that captures the known cognitive-behavioural variations in SD and map these to the patients' distribution of frontotemporal atrophy. Here we show that the degree of generalised semantic impairment is related to the patients' total, bilateral ATL atrophy. Verbal production ability is related to total ATL atrophy as well as to the balance of left > right ATL atrophy. Apathy is found to relate positively to the degree of orbitofrontal atrophy. Disinhibition is related to right ATL and orbitofrontal atrophy, and face recognition to right ATL volumes. Rather than positing mutually-exclusive sub-categories, the data-driven model repositions semantics, language, social behaviour and face recognition into a continuous frontotemporal neurocognitive space.

A neurocognitive model of perceptual decision-making on emotional signals

Humans make various kinds of decisions about which emotions they perceive from others. Although it might seem like a split-second phenomenon, deliberating over which emotions we perceive unfolds across several stages of decisional processing. Neurocognitive models of general perception postulate that our brain first extracts sensory information about the world then integrates these data into a percept and lastly interprets it. The aim of the present study was to build an evidence-based neurocognitive model of perceptual decision-making on others' emotions. We conducted a series of meta-analyses of neuroimaging data spanning 30 years on the explicit evaluations of others' emotional expressions. We find that emotion perception is rather an umbrella term for various perception paradigms, each with distinct neural structures that underline task-related cognitive demands. Furthermore, the left amygdala was responsive across all classes of decisional paradigms, regardless of task-related demands. Based on these observations, we propose a neurocognitive model that outlines the information flow in the brain needed for a successful evaluation of and decisions on other individuals' emotions. HIGHLIGHTS: Emotion classification involves heterogeneous perception and decision-making tasks Decision-making processes on emotions rarely covered by existing emotions theories We propose an evidence-based neuro-cognitive model of decision-making on emotions Bilateral brain processes for nonverbal decisions, left brain processes for verbal decisions Left amygdala involved in any kind of decision on emotions.

A new test of action verb naming: normative data from 290 Italian adults

INTRODUCTION

Verbs and nouns can be selectively impaired, suggesting that they are processed, at least in part, by distinct neural structures. While several tests of object naming are available, tasks involving action verb naming with normative data are lacking. We report the construction and standardization of a new test for the assessment of picture naming of actions.

MATERIAL AND METHODS

The test includes 50 stimuli, strictly controlled for several confounding variables. Normative data on 290 Italian subjects pooled across homogenous subgroups for age, sex, and education are reported.

RESULTS

Multiple regression analyses revealed that age and education significantly correlated with the subject's score. In particular, increasing age negatively affected performance, while the performance increased with a higher education.

CONCLUSIONS

In the clinical practice, the availability of equivalent scores will help the comparison with performance in the picture naming of objects. This test allows investigating action naming deficits in aphasic patients, in Parkinson's disease patients and in further neurodegenerative disorders, in which a specific impairment of action verbs is expected, filling a gap in the clinical neuropsychological assessment.

Degradation of Praxis Brain Networks and Impaired Comprehension of Manipulable Nouns in Stroke

Distributed brain systems contribute to representation of semantic knowledge. Whether sensory and motor systems of the brain are causally involved in representing conceptual knowledge is an especially controversial question. Here, we tested 57 chronic left-hemisphere stroke patients using a semantic similarity judgment task consisting of manipulable and nonmanipulable nouns. Three complementary methods were used to assess the neuroanatomical correlates of semantic processing: voxel-based lesion-symptom mapping, resting-state functional connectivity, and gray matter fractional anisotropy. The three measures provided converging evidence that injury to the brain networks required for action observation, execution, planning, and visuomotor coordination are associated with specific deficits in manipulable noun comprehension relative to nonmanipulable items. Damage or disrupted connectivity of areas such as the middle posterior temporal gyrus, anterior inferior parietal lobe, and premotor cortex was related specifically to the impairment of manipulable noun comprehension. These results suggest that praxis brain networks contribute especially to the comprehension of manipulable object nouns.

Dissociating action and abstract verb comprehension post-stroke

The neural bases of action and abstract concept representations remain a topic of debate. While several lines of research provide evidence for grounding of action-related conceptual content into sensory-motor systems, results of traditional lesion-deficit studies have been somewhat inconsistent. Further, few studies have directly compared the neural substrates of action and relatively abstract verb comprehension post-stroke. Here, we investigated the impact of the disruption of two neural networks on comprehension of action and relatively abstract verbs in 48 unilateral left-hemisphere stroke patients using two methodologies: 1) lesion-deficit association and 2) resting-state functional connectivity (RSFC) analyses. Disruption of RSFC between the left inferior frontal gyrus and right hemisphere primary and secondary sensory-motor areas predicted greater relative impairment of action semantics. Voxel-based lesion-symptom mapping revealed that damage to frontal white matter, extending towards the inferior frontal gyrus, also predicted greater relative impairment of action semantics. On the other hand, damage to the left anterior middle temporal gyrus significantly impaired the more abstract category relative to action. These findings support the view that action and non-action/abstract semantic processing rely on partially dissociable brain networks, with action concepts relying more heavily on sensory-motor areas. The results also have wider implications for lesion-deficit association studies and show how the contralateral hemisphere can play a compensatory role following unilateral stroke.

Processing of Action and Sound Verbs in Context: An FMRI Study

Recent theories propose a flexible recruitment of sensory and motor brain regions during conceptual processing depending on context and task. The present functional magnetic resonance imaging study investigated the influence of context and task on conceptual processing of action and sound verbs. Participants first performed an explicit semantic context decision task, in which action and sound verbs were presented together with a context noun. The same verbs were repeatedly presented in a subsequent implicit lexical decision task together with new action and sound verbs. Thereafter, motor and acoustic localizer tasks were administered to identify brain regions involved in perception and action. During the explicit task, we found differential activations to action and sound verbs near corresponding sensorimotor brain regions. During the implicit lexical decision task, differences between action and sound verbs were absent. However, feature-specific repetition effects were observed near corresponding sensorimotor brain regions. The present results suggest flexible conceptual representations depending on context and task. Feature-specific effects were observed only near, but not within corresponding sensorimotor brain regions, as defined by the localizer tasks. Our results therefore only provide limited evidence in favor of grounded cognition theories assuming a close link between the conceptual and the sensorimotor systems.

Distinct neural mechanisms underlying conceptual knowledge of manner and instrument verbs

Studies on the organization of conceptual knowledge have examined categories of concrete nouns extensively. Less is known about the neural basis of verb categories suggested by linguistic theories. We used functional MRI to examine the differences between manner verbs, which encode information about the manner of an action, versus instrument verbs, which encode information about an object as part of their meaning. Using both visual and verbal stimuli and a combination of univariate and multivariate pattern analyses, our results show that accessing conceptual representations of instrument class involves brain regions typically associated with complex action and object perception, including the anterior inferior parietal cortex and occipito-temporal cortex. On the other hand, accessing conceptual representations of the manner class involves regions that are commonly associated with the processing of visual and biological motion, in the posterior superior temporal sulcus. These findings support the idea that the semantics of manner and instrument verbs are supported by distinct neural mechanisms.

Action Semantic Deficits and Impaired Motor Skills in Autistic Adults Without Intellectual Impairment

Several studies indicate the functional importance of the motor cortex for higher cognition, language and semantic processing, and place the neural substrate of these processes in sensorimotor action-perception circuits linking motor, sensory and perisylvian language regions. Interestingly, in individuals with autism spectrum disorder (ASD), semantic processing of action and emotion words seems to be impaired and is associated with hypoactivity of the motor cortex during semantic processing. In this study, the relationship between semantic processing, fine motor skills and clinical symptoms was investigated in 19 individuals with ASD and 22 typically-developing matched controls. Participants completed two semantic decision tasks involving words from different semantic categories, a test of alexithymia (the Toronto Alexithymia Scale), and a test of fine motor skills (the Purdue Pegboard Test). A significant Group × Word Category interaction in accuracy (p < 0.05) demonstrated impaired semantic processing for action words, but not object words in the autistic group. There was no significant group difference when processing abstract emotional words or abstract neutral words. Moreover, our study revealed deficits in fine motor skills as well as evidence for alexithymia in the ASD group, but not in neurotypical controls. However, these motor deficits did not correlate significantly with impairments in action-semantic processing. We interpret the data in terms of an underlying dysfunction of the action-perception system in ASD and its specific impact on semantic language processing.