scholarly journals Mapping lesion, structural disconnection, and functional disconnection to symptoms in semantic aphasia

2021 ◽  
Author(s):  
Nicholas E. Souter ◽  
Xiuyi Wang ◽  
Hannah Thompson ◽  
Katya Krieger-Redwood ◽  
Ajay D. Halai ◽  
...  
Keyword(s):  
Cognitive Control ◽  
Left Hemisphere ◽  
Executive Control ◽  
Inferior Frontal Gyrus ◽  
Temporal Cortex ◽  
Executive Dysfunction ◽  
Semantic Retrieval ◽  
Semantic Cognition ◽  
Left Hemisphere Stroke ◽  
Executive Impairment

AbstractPatients with semantic aphasia have impaired control of semantic retrieval, often accompanied by executive dysfunction following left hemisphere stroke. Many but not all of these patients have damage to the left inferior frontal gyrus, important for semantic and cognitive control. Yet semantic and cognitive control networks are highly distributed, including posterior as well as anterior components. Accordingly, semantic aphasia might not only reflect local damage but also white matter structural and functional disconnection. Here we characterise the lesions and predicted patterns of structural and functional disconnection in individuals with semantic aphasia and relate these effects to semantic and executive impairment. Impaired semantic cognition was associated with infarction in distributed left- hemisphere regions, including in the left anterior inferior frontal and posterior temporal cortex. Lesions were associated with executive dysfunction within a set of adjacent but distinct left frontoparietal clusters. Performance on executive tasks was also associated with interhemispheric structural disconnection across the corpus callosum. Poor semantic cognition was associated with small left-lateralized structurally disconnected clusters, including in the left posterior temporal cortex. These results demonstrate that while left- lateralized semantic and executive control regions are often damaged together in stroke aphasia, these deficits are associated with distinct patterns of structural disconnection, consistent with the bilateral nature of executive control and the left-lateralized yet distributed semantic control network.

scholarly journals Motivated semantic control: Exploring the effects of extrinsic reward and self-reference on semantic retrieval in semantic aphasia

2021 ◽  
Author(s):  
Nicholas Edward Souter ◽  
Sara Stampacchia ◽  
Glyn Hallam ◽  
Hannah Thompson ◽  
Jonathan Smallwood ◽  
...  
Keyword(s):  
Executive Control ◽  
Intrinsic Value ◽  
Semantic Retrieval ◽  
Extrinsic Reward ◽  
Proactive Control ◽  
Semantic Cognition ◽  
Semantic Associations ◽  
Low Levels ◽  
Task Representations ◽  
Self Reference

Recent insights show increased motivation can benefit executive control, but this effect has not been explored in relation to semantic cognition. Patients with deficits of controlled semantic retrieval in the context of semantic aphasia (SA) after stroke may benefit from this approach since their deficits tend to be accompanied by deficits of cognitive control. We assessed the effect of both extrinsic and intrinsic motivation in healthy controls and semantic aphasia patients. Experiment 1 manipulated extrinsic reward using high or low levels of points for correct responses during a semantic association task. Experiment 2 manipulated the intrinsic value of items using self-reference; allocating pictures of items to the participant ('self') or researcher ('other') in a shopping game before people retrieved their semantic associations. These experiments revealed that patients, but not controls, showed better performance when given an extrinsic reward, consistent with the view that increased external motivation may help to ameliorate patients' semantic control deficits. However, while self-reference was associated with better episodic memory, there was no effect on semantic retrieval. We conclude that semantic control deficits can be reduced when extrinsic rewards are anticipated; this enhanced motivational state is expected to support proactive control, for example, through the maintenance of task representations. It may be possible to harness this modulatory impact of reward to combat the control demands of semantic tasks in SA patients.

Imaging Fatigue of Interference Control Reveals the Neural Basis of Executive Resource Depletion

2013 ◽  
Vol 25 (3) ◽  
pp. 338-351 ◽  
Author(s):  
Jonas Persson ◽  
Anne Larsson ◽  
Patricia A. Reuter-Lorenz
Keyword(s):  
Executive Control ◽  
Right Hemisphere ◽  
Inferior Frontal Gyrus ◽  
Temporal Cortex ◽  
Active Regions ◽  
Resource Depletion ◽  
Control Group ◽  
Interference Control ◽  
Neural Basis ◽  
Executive Process

Executive control coordinates, prioritizes, and selects task-relevant representations under conditions of conflict. Behavioral evidence has documented that executive resources are separable, finite, and can be temporarily depleted; however, the neural basis for such resource limits are largely unknown. Here, we investigate the neural correlates underlying the fatigue or depletion of interference control, an executive process hypothesized to mediate competition among candidate memory representations. Using a pre/post continuous acquisition fMRI design, we demonstrate that, compared with a nondepletion control group, the depletion group showed a fatigue-induced performance deficit that was specific to interference control and accompanied by a left-to-right shift in the network of active regions. Specifically, we observed decreased BOLD signal in the left inferior frontal gyrus (IFG), striatum, and the cerebellum, along with a corresponding increase in right hemisphere regions including the IFG, insular, and temporal cortex. Depletion-related changes in activation magnitude correlated with behavioral changes, suggesting that decreased recruitment of task-relevant regions, including left IFG, contributes to impaired interference control. These results provide new evidence about the brain dynamics of “process-specific” fatigue and suggest that depletion may pose a significant limitation on the cognitive and neural resources available for executive control.

scholarly journals The Neural Correlates of Semantic Control Revisited

2020 ◽  
Author(s):  
Rebecca L. Jackson
Keyword(s):  
Semantic Network ◽  
Meta Analysis ◽  
Inferior Frontal Gyrus ◽  
Temporal Cortex ◽  
Neural Correlates ◽  
Middle Temporal Gyrus ◽  
Control Network ◽  
Temporal Region ◽  
List Type ◽  
Semantic Cognition

AbstractSemantic control, the ability to selectively access and manipulate meaningful information on the basis of context demands, is a critical component of semantic cognition. The precise neural correlates of semantic control are disputed, with particular debate surrounding parietal involvement, the spatial extent of the posterior temporal contribution and network lateralisation. Here semantic control is revisited, utilising improved analysis techniques and a decade of additional data to refine our understanding of the network. A meta-analysis of 876 peaks over 121 contrasts illuminated a left-focused network consisting of inferior frontal gyrus, posterior middle temporal gyrus, posterior inferior temporal gyrus and dorsomedial prefrontal cortex. This extended the temporal region implicated, and found no parietal involvement. Although left-lateralised overall, relative lateralisation varied across the implicated regions. Supporting analyses confirmed the multimodal nature of the semantic control network and situated it within the wider set of regions implicated in semantic cognition.Highlights➢A multimodal semantic control network was delineated with formal meta-analyses➢Semantic control recruits inferior and medial frontal and posterior temporal cortex➢A large extent of posterior temporal cortex was implicated and no parietal regions➢Semantic control is left-lateralised but regions show differential lateralisation➢The semantic control regions were situated in the context of the wider semantic network

scholarly journals Shared and Distinct Neuroanatomic Regions Critical for Tool-related Action Production and Recognition: Evidence from 131 Left-hemisphere Stroke Patients

2015 ◽  
Vol 27 (12) ◽  
pp. 2491-2511 ◽  
Author(s):  
Leyla Y. Tarhan ◽  
Christine E. Watson ◽  
Laurel J. Buxbaum
Keyword(s):  
Left Hemisphere ◽  
Mirror Neuron System ◽  
Inferior Frontal Gyrus ◽  
Occipital Cortex ◽  
Neural Substrates ◽  
Middle Temporal Gyrus ◽  
Stroke Patients ◽  
Middle Temporal ◽  
Impaired Performance ◽  
Left Hemisphere Stroke

The inferior frontal gyrus and inferior parietal lobe have been characterized as human homologues of the monkey “mirror neuron” system, critical for both action production (AP) and action recognition (AR). However, data from brain lesion patients with selective impairment on only one of these tasks provide evidence of neural and cognitive dissociations. We sought to clarify the relationship between AP and AR, and their critical neural substrates, by directly comparing performance of 131 chronic left-hemisphere stroke patients on both tasks—to our knowledge, the largest lesion-based experimental investigation of action cognition to date. Using voxel-based lesion-symptom mapping, we found that lesions to primary motor and somatosensory cortices and inferior parietal lobule were associated with disproportionately impaired performance on AP, whereas lesions to lateral temporo-occipital cortex were associated with a relatively rare pattern of disproportionately impaired performance on AR. In contrast, damage to posterior middle temporal gyrus was associated with impairment on both AP and AR. The distinction between lateral temporo-occipital cortex, critical for recognition, and posterior middle temporal gyrus, important for both tasks, suggests a rough gradient from modality-specific to abstract representations in posterior temporal cortex, the first lesion-based evidence for this phenomenon. Overall, the results of this large patient study help to bring closure to a long-standing debate by showing that tool-related AP and AR critically depend on both common and distinct left hemisphere neural substrates, most of which are external to putative human mirror regions.

scholarly journals Right-hemisphere compensation during word production: A single case of left-hemisphere young stroke

2021 ◽  
Author(s):  
Irina Chupina ◽  
Joanna Sierpowska ◽  
Xiaochen Zheng ◽  
Anna Dewenter ◽  
Maria Carla Piastra ◽  
...  
Keyword(s):  
Left Hemisphere ◽  
Structural Damage ◽  
Right Hemisphere ◽  
Single Case ◽  
Inferior Frontal Gyrus ◽  
Age Groups ◽  
Word Finding ◽  
Deterministic Tractography ◽  
Left Hemisphere Stroke ◽  
Phonological Retrieval

Our understanding of post-stroke language recovery and underlying neuroplasticity is largely based on older age groups, who have increasing brain pathology and potentially more bilateral language functioning. We present the case of A., a 23 y.o. woman with chronic aphasia from a left-hemisphere stroke. Deterministic tractography indicated that A.’s language-relevant white matter structures were severely damaged. Using magnetoencephalography (MEG), we explored A.’s conceptual preparation and subsequent word planning abilities. Context-driven and Bare picture-naming tasks revealed substantial naming deficits, manifesting as word-finding difficulties and semantic paraphasias about half of the time. Naming was however facilitated by semantically constraining lead-in sentences. Altogether, this pattern indicates intact conceptual preparation but disrupted lexical and phonological retrieval abilities. MEG revealed that A.’s naming-related neural responses differed from that of a matched control. Source localisation showed active but differential recruitment of right-hemisphere structures (300-400 ms post-picture onset) during both correct naming (right temporo-parietal regions) and anomic (right inferior frontal gyrus) attempts. We consider that, despite A.’s young age, the presumed strong degree of language lateralisation and extensive structural damage limited her recovery. Although A.’s right hemisphere responded in a timely manner during word planning, its lexical and phonological retrieval abilities remained modest.

scholarly journals Reduced competition between tool action neighbors in left hemisphere stroke

2019 ◽  
Author(s):  
Frank E. Garcea ◽  
Harrison Stoll ◽  
Laurel J. Buxbaum
Keyword(s):  
Left Hemisphere ◽  
Tool Use ◽  
Neighborhood Effects ◽  
Inferior Frontal Gyrus ◽  
Support Vector ◽  
Single Action ◽  
Limb Apraxia ◽  
Left Hemisphere Stroke ◽  
Hand Action ◽  
Action Errors

AbstractWhen pantomiming the use of tools, patients with limb apraxia after left hemisphere stroke (LCVA) produce more spatiotemporal hand action errors with tools associated with conflicting actions for use versus grasp-to-pick-up (e.g., corkscrew) than tools having a single action for both use and grasp (e.g., hammer). There are two possible accounts for this pattern of results. Reduced performance with ‘conflict’ tools may simply reflect weakened automaticity of use action activation, which is evident only when the use and grasp actions are not redundant. Alternatively, poor use performance may reflect reduced ability of appropriate tool use actions to compete with task-inappropriate action representations. To address this issue, we developed a Stroop-like experiment in which 21 LCVA and 8 neurotypical participants performed pantomime actions in blocks containing two tools that were similar (“neighbors”) in terms of hand action or function, or unrelated on either dimension. In a congruent condition, they pantomimed the use action associated with the visually presented tool, whereas in an incongruent condition, they pantomimed the use action for the other tool in the block. Relative to controls and other task conditions, LCVA participants showed reductions in hand action errors in incongruent relative to congruent action trials; furthermore, the degree of reduction in this incongruence effect was related to the participants’ susceptibility to grasp-on-use conflict in a separate test of pantomime to the sight of tools. Support vector regression lesion-symptom mapping analyses identified the left inferior frontal gyrus, supramarginal gyrus, and superior longitudinal fasciculus as core neuroanatomical sites associated with abnormal performance on both tasks. Collectively, the results indicate that weakened activation of tool use actions in limb apraxia gives rise to reduced ability of these actions to compete for task-appropriate selection when competition arises within single tools (grasp-on-use conflict) as well as between two tools (reduced neighborhood effects).

scholarly journals Right Hemisphere Remapping of Naming Functions Depends on Lesion Size and Location in Poststroke Aphasia

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Laura M. Skipper-Kallal ◽  
Elizabeth H. Lacey ◽  
Shihui Xing ◽  
Peter E. Turkeltaub
Keyword(s):  
Motor Cortex ◽  
Left Hemisphere ◽  
Neural Plasticity ◽  
Right Hemisphere ◽  
Inferior Frontal Gyrus ◽  
Lesion Size ◽  
Language Function ◽  
The Right ◽  
Left Hemisphere Stroke ◽  
Aphasia Recovery

The study of language network plasticity following left hemisphere stroke is foundational to the understanding of aphasia recovery and neural plasticity in general. Damage in different language nodes may influence whether local plasticity is possible and whether right hemisphere recruitment is beneficial. However, the relationships of both lesion size and location to patterns of remapping are poorly understood. In the context of a picture naming fMRI task, we tested whether lesion size and location relate to activity in surviving left hemisphere language nodes, as well as homotopic activity in the right hemisphere during covert name retrieval and overt name production. We found that lesion size was positively associated with greater right hemisphere activity during both phases of naming, a pattern that has frequently been suggested but has not previously been clearly demonstrated. During overt naming, lesions in the inferior frontal gyrus led to deactivation of contralateral frontal areas, while lesions in motor cortex led to increased right motor cortex activity. Furthermore, increased right motor activity related to better naming performance only when left motor cortex was lesioned, suggesting compensatory takeover of speech or language function by the homotopic node. These findings demonstrate that reorganization of language function, and the degree to which reorganization facilitates aphasia recovery, is dependent on the size and site of the lesion.

scholarly journals Characterising factors underlying praxis deficits in chronic left hemisphere stroke patients

2020 ◽  
Author(s):  
Elisabeth Rounis ◽  
Ajay Halai ◽  
Gloria Pizzamiglio ◽  
Matthew A. Lambon Ralph
Keyword(s):  
Left Hemisphere ◽  
Cognitive Disorders ◽  
Principal Component ◽  
Lesion Volume ◽  
Semantic Retrieval ◽  
Stroke Patients ◽  
Limb Apraxia ◽  
Lesion Symptom Mapping ◽  
Neuropsychological Tasks ◽  
Left Hemisphere Stroke

AbstractLimb apraxia, a disorder of skilled action not consequent on primary motor or sensory deficits, has traditionally been defined according to errors patients make on neuropsychological tasks. Previous models of the disorder have failed to provide a unified account of patients’ deficits, due to heterogeneity in the patients and tasks used. In this study we implemented principal component analysis (PCA) to elucidate core factors of the disorder in a cohort of 41 unselected left hemisphere chronic stroke patients who were tested on a comprehensive and validated apraxia screen. Three principal components were identified: posture selection, semantic control and multi-demand sequencing. These were submitted to a lesion symptom mapping (VBCM) analysis in a subset of 24 patients, controlled for lesion volume, age and time post-stroke. Although the first component revealed no significant structural correlates, the second and third components were related to regions in the ‘ventro-dorsal’ and ‘ventral’ and ‘dorsal’ pathways, respectively. These results challenge the previously reported distinction between ideomotor and ideational deficits and highlight a significant role of common cognitive functions in the disorder, which include action selection, semantic retrieval, sequencing and response inhibition. Further research using this technique would help elucidate the cognitive processes underlying limb apraxia and their relationship with other cognitive disorders.

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