A Role for the Action Observation Network in Apraxia After Stroke.

Limb apraxia is a syndrome often observed after stroke that affects the ability to perform skilled actions despite intact elementary motor and sensory systems. In a large cohort of unselected stroke patients with lesions to the left, right, and bilateral hemispheres, we used voxel-based lesion-symptom mapping (VLSM) on clinical CT head images to identify the neuroanatomical correlates of the impairment of performance in three tasks investigating praxis skills in patient populations. These included a meaningless gesture imitation task, a gesture production task involving pantomiming transitive and intransitive gestures, and a gesture recognition task involving recognition of these same categories of gestures. Neocortical lesions associated with poor performance in these tasks were all in the left hemisphere. They involved the pre-striate and medial temporal cortices, the superior temporal sulcus, inferior parietal area PGi, the superior longitudinal fasciculus underlying the primary motor cortex, and the uncinate fasciculus, subserving connections between temporal and frontal regions. No significant lesions were identified when language deficits, as indicated via a picture naming task, were controlled for. The implication of the superior temporal sulcus and the anatomically connected prestriate and inferior parietal regions challenges traditional models of the disorder. The network identified has been implicated in studies of action observation, which might share cognitive functions sub-serving praxis and language skills.

The Hong Kong version of the Oxford Cognitive Screen (HK-OCS): validation study for Cantonese-speaking chronic stroke survivors.

This study reports the validation of the Hong Kong version of Oxford Cognitive Screen (HK-OCS). Seventy Cantonese-speaking healthy individuals participated to establish normative data and 46 chronic stroke survivors were assessed using the HK-OCS, Albert's Test of Visual Neglect, short test of gestural production, and Hong Kong version of the following assessments: Western Aphasia Battery, MMSE, MoCA, Modified Barthel Index, and Lawton Instrumental Activities of Daily Living scale. The validity of the HK-OCS was appraised by the difference between the two participant groups. Neurologically unimpaired individuals performed significantly better than stroke survivors on the HK-OCS. Positive and significant correlations found between cognitive subtests in the HK-OCS and related assessments indicated good concurrent validity. Excellent intra-rater and inter-rater reliabilities, fair test-retest reliability, and acceptable internal consistency suggested that the HK-OCS had good reliability. Specific HK-OCS subtests including semantics, episodic memory, number writing, and orientation were the best predictors of functional outcomes.

Stored color-form knowledge modulates perceptual sensitivity in search.

We used signal detection analysis to examine the effects of stored color-form knowledge on visual search. Across four experiments, we showed robust effects of stored color-form knowledge on perceptual sensitivity, whereas the effects on response criteria varied. The effects on perceptual sensitivity were stronger when multiple items were present and when the color fell on the surface of the object. The benefit was found even when the correctly colored target had a low probability of occurrence in the experiment. In addition, the benefit was present across different display sizes, and the effects of increasing the exposure duration on detecting correctly colored targets were equal across different sizes of the display. The data suggest that color-form conjunctions are detected efficiently to activate stored color-form knowledge, and that this knowledge then influences early perceptual processing in a bottom-up manner. We discuss the implications for understanding the coding of conjunctive relations.

Reading without the left ventral occipito-temporal cortex.

The left ventral occipito-temporal cortex (LvOT) is thought to be essential for the rapid parallel letter processing that is required for skilled reading. Here we investigate whether rapid written word identification in skilled readers can be supported by neural pathways that do not involve LvOT. Hypotheses were derived from a stroke patient who acquired dyslexia following extensive LvOT damage. The patient followed a reading trajectory typical of that associated with pure alexia, re-gaining the ability to read aloud many words with declining performance as the length of words increased. Using functional MRI and dynamic causal modelling (DCM), we found that, when short (three to five letter) familiar words were read successfully, visual inputs to the patient's occipital cortex were connected to left motor and premotor regions via activity in a central part of the left superior temporal sulcus (STS). The patient analysis therefore implied a left hemisphere "reading-without-LvOT" pathway that involved STS. We then investigated whether the same reading-without-LvOT pathway could be identified in 29 skilled readers and whether there was inter-subject variability in the degree to which skilled reading engaged LvOT. We found that functional connectivity in the reading-without-LvOT pathway was strongest in individuals who had the weakest functional connectivity in the LvOT pathway. This observation validates the findings of our patient's case study. Our findings highlight the contribution of a left hemisphere reading pathway that is activated during the rapid identification of short familiar written words, particularly when LvOT is not involved. Preservation and use of this pathway may explain how patients are still able to read short words accurately when LvOT has been damaged.

The neural underpinings of simultanagnosia: disconnecting the visuospatial attention network.

Because of our limited processing capacity, different elements of the visual scene compete for the allocation of processing resources. One of the most striking deficits in visual selection is simultanagnosia, a rare neuropsychological condition characterized by impaired spatial awareness of more than one object at time. To decompose the neuroanatomical substrates of the syndrome and to gain insights into the structural and functional organization of visuospatial attention, we performed a systematic evaluation of lesion patterns in a group of simultanagnosic patients compared with patients with either (i) unilateral visuospatial deficits (neglect and/or extinction) or (ii) bilateral posterior lesions without visuospatial deficits, using overlap/subtraction analyses, estimation of lesion volume, and a lesion laterality index. We next used voxel-based morphometry to assess the link between different visuospatial deficits and gray matter and white matter (WM) damage. Lesion overlap/subtraction analyses, lesion laterality index, and voxel-based morphometry measures converged to indicate that bilateral parieto-occipital WM disconnections are both distinctive and necessary to create symptoms associated with simultanagnosia. We also found that bilateral gray matter damage within the middle frontal area (BA 46), cuneus, calacarine, and parieto-occipital fissure as well as right hemisphere parietal lesions within intraparietal and postcentral gyri were associated with simultanagnosia. Further analysis of the WM based on tractography revealed associations with bilateral damage to major pathways within the visuospatial attention network, including the superior longitudinal fasciculus, the inferior fronto-occipital fasciculus, and the inferior longitudinal fasciculus. We conclude that damage to the parieto-occipital regions and the intraparietal sulcus, together, with bilateral WM disconnections within the visuosptial attention network, contribute to poor visual processing of multiple objects and the loss of processing speed characteristic of simultanagnosia.

Seated bilateral leg exercise effects on hemiparetic lower extremity function in chronic stroke.

BACKGROUND: Bilateral arm training with rhythmic auditory cueing (BATRAC) improves hemiparetic upper extremity (UE) function in stroke. It is unknown whether a similar exercise for the hemiparetic lower extremity (LE) is effective. OBJECTIVE: The authors sought to test whether the BATRAC strategy would transfer to the legs by improving LE motor function following ten 30-minute sessions of bilateral leg training with rhythmic auditory cueing (BLETRAC). METHODS: Twenty-four chronic stroke participants, recruited from the community, were randomized to either the BLETRAC or the BATRAC intervention. Assessments were performed before (week 0) and after (week 6) training as well as 3 months later (week 18). Change in the Fugl-Meyer LE and UE subscales served as primary outcomes. Timed 10-m walk, movement parameters during treadmill walking, and a repetitive aiming task for both feet and hands were the secondary outcomes. RESULTS: Following an intention-to-treat approach, data from 21 subjects were analyzed. After training, improvements in the Fugl-Meyer LE and UE subscales tended to be better for the corresponding intervention group. The BLETRAC group also showed increases in step length during treadmill walking and performance in the repetitive foot and hand aiming tasks. No differences between the intervention groups were found at follow-up. CONCLUSIONS: This exploratory trial demonstrates that transfer of the BATRAC approach to the legs is feasible. Transient improvements of limb motor function in chronic stroke participants were induced by targeted exercise (BATRAC for the UE and BLETRAC for the LE). It may be that further periods of training would increase and maintain effects.

Short-term effects on mobility, activities of daily living and health-related quality of life of a Conductive Education programme for adults with multiple sclerosis, Parkinson's disease and stroke.

OBJECTIVE: To evaluate the impact of 10 sessions of Conductive Education on mobility, functional independence and health-related quality of life in adults with multiple sclerosis, Parkinson's disease and stroke. DESIGN: Observational, pretest-posttest design. SETTING: The National Institute of Conductive Education, Birmingham, UK. PARTICIPANTS: One hundred and twenty-nine self-referred community-living individuals with moderate disability. INTERVENTION: Following an individual consultation, participants attended 10 diagnostic-specific group sessions of Conductive Education, scheduled daily or less commonly weekly. OUTCOME MEASURES: All participants were assessed using the Barthel Index and the Nottingham Extended Activities of Daily living Index. Stroke, multiple sclerosis and Parkinson's disease patients also completed the Short Form 36 (SF-36) Health Survey, the Multiple Sclerosis Quality of Life 54 questionnaire (MSQoL-54) and the Parkinson's Disease Questionnaire (PDQ-39) respectively. RESULTS: One hundred and five individuals completed the programme as well as all pre and post-assessments. Of these, 34 had suffered a stroke, 55 had Parkinson's disease and 16 had multiple sclerosis. Stroke patients demonstrated statistically significant improvements in the Nottingham Extended Activities of Daily living Index (mean change 3.4, P<0.001) and the SF-36 mental health subsection (mean change 7.8, P<0.001). Non-significant trends towards improved physical and mental function were demonstrated by other outcome measures across all three diagnoses. CONCLUSIONS: The results emphasize potential benefits of Conductive Education for individuals with stroke. The results will inform further randomized comparisons of the effects of Conductive Education in neurologically disabled people.

The use of memorised verbal scripts in the rehabilitation of action disorganisation syndrome.

We report data on the rehabilitation of action disorganisation syndrome (ADS). Although prior attempts to rehabilitate everyday actions in our patient, FK, had proved unsuccessful, we report positive results from using a verbalisation strategy. FK was taught a poem based on the steps involved in making a cup of tea. Following training, the everyday action was performed more successfully than prior to training, with the order of the actions in particular being improved when the poem was applied. In addition, there was evidence of error monitoring being carried out contingent on the verbalisation strategy. Across training sessions FK also became more likely to apply the poem and to perform the actions without prompting. However, there was relatively weak training effects across sessions, and the beneficial effects did not transfer to new tasks or to the same task with a different key object. The utility of the approach for severe cases of ADS is discussed.