Central auditory processing in adults with chronic stroke without hearing loss: A magnetoencephalography study.

OBJECTIVE: Stroke lesions in non-auditory areas may affect higher-order central auditory processing. We sought to characterize auditory functions in chronic stroke survivors with unilateral arm/hand impairment using auditory evoked responses (AERs) with lesion and perception metrics. METHODS: The AERs in 29 stroke survivors and 14 controls were recorded with single tones, active and passive frequency-oddballs, and a dual-oddball with pitch-contour and time-interval deviants. Performance in speech-in-noise, mistuning detection, and moving-sound detection was assessed. Relationships between AERs, behaviour, and lesion overlap with functional networks, were examined. RESULTS: Despite their normal hearing, eight patients showed unilateral AER in the hemisphere ipsilateral to the affected hand with reduced amplitude compared to those with bilateral AERs. Both groups showed increasing attenuation of later components. Hemispheric asymmetry of AER sources was reduced in bilateral-AER patients. The N1 wave (100 ms latency) and P2 (200 ms) were delayed in individuals with lesions in the basal-ganglia and white-matter, while lesions in the attention network reduced the frequency-MMN (mismatch negativity) responses and increased the pitch-contour P3a response. Patients' impaired speech-in-noise perception was explained by AER measures and frequency-deviant detection performance with multiple regression. CONCLUSION: AERs reflect disruption of auditory functions due to damage outside of temporal lobe, and further explain complexity of neural mechanisms underlying higher-order auditory perception. SIGNIFICANCE: Stroke survivors without obvious hearing problems may benefit from rehabilitation for central auditory processing.

The effects of music-supported therapy on motor, cognitive, and psychosocial functions in chronic stroke.

Neuroplasticity accompanying learning is a key mediator of stroke rehabilitation. Training in playing music in healthy populations and patients with movement disorders requires resources within motor, sensory, cognitive, and affective systems, and coordination among these systems. We investigated effects of music-supported therapy (MST) in chronic stroke on motor, cognitive, and psychosocial functions compared to conventional physical training (GRASP). Twenty-eight adults with unilateral arm and hand impairment were randomly assigned to MST (n = 14) and GRASP (n = 14) and received 30 h of training over a 10-week period. The assessment was conducted at four time points: before intervention, after 5 weeks, after 10 weeks, and 3 months after training completion. As for two of our three primary outcome measures concerning motor function, all patients slightly improved in Chedoke-McMaster Stroke Assessment hand score, while the time to complete Action Research Arm Test became shorter in the MST group. The third primary outcome measure for well-being, Stroke Impact Scale, was improved for emotion and social communication earlier in MST and coincided with the improved executive function for task switching and music rhythm perception. The results confirmed previous findings and expanded the potential usage of MST for enhancing quality of life in community-dwelling chronic-stage survivors.

VL: a further case of erroneous recollection.

We report a single-case study of a female patient (VL) who exhibited frequent episodes of erroneous recollections triggered by everyday events. Based on neuropsychological testing, VL was classified as suffering from mild to moderate dementia (MMSE=18) and was given a diagnosis of probable Alzheimer׳s disease. Her memory functions were uniformly impaired but her verbal abilities were generally well preserved. A structural MRI scan showed extensive areas of gray matter atrophy particularly in frontal and medial-temporal (MTL) areas. Results of experimental recognition tests showed that VL had very high false alarm rates on tests using pictures, faces and auditory stimuli, but lower false alarm rates on verbal tests. We provide a speculative account of her erroneous recollections in terms of her MTL and frontal pathology. In outline, we suggest that owing to binding failures in MTL regions, VL׳s recognition processes were forced to rely on earlier than normal stages of analysis. Environmental features on a given recognition trial may have combined with fragments persisting from previous trials resulting in erroneous feelings of familiarity and of recollection that were not discounted or edited out, due to her impaired frontal processes.

Changes in neuromagnetic beta-band oscillation after music-supported stroke rehabilitation.

Precise timing of sound is crucial in music for both performing and listening. Indeed, listening to rhythmic sound sequences activates not only the auditory system but also the sensorimotor system. Previously, we showed the significance of neural beta-band oscillations (15-30 Hz) for the timing processing that involves such auditory-motor coordination. Thus, we hypothesized that motor rehabilitation training incorporating music playing will stimulate and enhance auditory-motor interaction in stroke patients. We examined three chronic patients who received Music-Supported Therapy following the protocols practiced by Schneider. Neuromagnetic beta-band activity was remarkably alike during passive listening to a metronome and during finger tapping, with or without the metronome, for either the paretic or nonparetic hand, suggesting a shared mechanism of the beta modulation. In the listening task, the magnitude of the beta decrease after the tone onset was more pronounced at the posttraining time point and was accompanied by improved arm and hand skills. The present case data give insight into the neural underpinnings of rehabilitation with music making and rhythmic auditory stimulation.

The future of cognitive neurorehabilitation.

Cognitive neurorehabilitation is rooted both in the cognitive function being treated and the neural substrates underlying that ability. Recent progress in understanding both brain (in particular brain plasticity) and the complexities of behaviour imply a promising future for cognitive neurorehabilitation. The manuscripts in this issue focuse on advances in the use of non-invasive brain stimulation (NIBS) as a tool for cognitive neurorehabilitation. This paper presents a broader context in which to understand the importance and potential of this specific approach. Achieving the promise requires theoretical and experimental rigour including selection of relevant outcome measures, and understanding of the complexities of individual patients. Success will depend on our ability to integrate knowledge and approaches.

Magnetic resonance imaging in frontotemporal dementia shows subcortical atrophy.

BACKGROUND/AIMS: The clinical syndrome of the frontotemporal dementias (FTD) overlaps with frontal-subcortical circuit syndromes. We explored the extent to which subcortical atrophy on structural magnetic resonance imaging may indicate a subcortical contribution to the progression of FTD. METHODS: This cross-sectional case-control study compared striatal and thalamic gray matter volumes and functional levels from 30 FTD cases and 30 age- and gender-matched controls. RESULTS: The FTD group had significantly more atrophy in all gray matter subcortical regions, correlating with ipsilateral frontocortical atrophy. Subcortical atrophy was also associated with functional disability. Subcortical asymmetry was most marked in subjects with primary progressive aphasia. CONCLUSION: Subcortical gray matter atrophy may contribute as significantly to symptoms of FTD as cortical atrophy.

Independent cognitive effects of atrophy and diffuse subcortical and thalamico-cortical cerebrovascular disease in dementia.

BACKGROUND AND PURPOSE: Brain atrophy, cortical infarction, and subcortical ischemic vasculopathy have all been associated with cognitive dysfunction. The interrelationships between these pathologies and their independent contributions to cognitive function remain unclear. Despite the high frequency of Alzheimer disease (AD) in those with clinically diagnosed vascular dementia, and the frequent findings of vascular disease in those with clinically diagnosed AD, many studies of brain-behavior relationships in dementia consider these populations separately. The present study sought to identify the correlates of independent domains of cognitive impairment in an unselected sample across a large range of severity and overlap of AD and VaD. METHODS: Two hundred five individuals from the Sunnybrook Dementia Study recruited from a university Memory clinic had detailed neuropsychological testing and MRI quantification using a multi-step postprocessing algorithm. A factor analysis of the cognitive protocol yielded a 3-factor solution, provisionally labeled: (1) short-term memory and language, (2) attention and working memory, and (3) mental flexibility. RESULTS: A factor analysis of brain measures identified 3 independent factors with measures of (1) brain atrophy, (2) subcortical vascular disease, and (3) strategic infarcts (anterior-medial thalamus and cortical infarcts). After accounting for the effects of age and education, measures of brain atrophy were the strongest correlates of all cognitive domains. Small vessel disease was independently associated with general severity, impaired short-term memory/language, and reduced mental flexibility, but not with poor working memory, presumably through disruption of frontal-subcortical connections. In contrast, strategic infarcts to anterior-medial thalamus and cortical gray matter were associated with poor short-term and working memory, but not with impairments in mental flexibility or global severity measures. CONCLUSIONS: These data support the hypothesis that the thalamico-cortical network subserves both short-term and working memory. The findings also suggest that each type of pathology (atrophy, small vessel disease, and strategic infarcts) contribute independently to the pattern of cognitive disabilities associated with dementia. Particular attention to cerebrovascular disease in deep white or gray matter structures of the thalamico-cortical system is certainly warranted.

Clustered functional MRI of overt speech production.

To investigate the neural network of overt speech production, event-related fMRI was performed in 9 young healthy adult volunteers. A clustered image acquisition technique was chosen to minimize speech-related movement artifacts. Functional images were acquired during the production of oral movements and of speech of increasing complexity (isolated vowel as well as monosyllabic and trisyllabic utterances). This imaging technique and behavioral task enabled depiction of the articulo-phonologic network of speech production from the supplementary motor area at the cranial end to the red nucleus at the caudal end. Speaking a single vowel and performing simple oral movements involved very similar activation of the cortical and subcortical motor systems. More complex, polysyllabic utterances were associated with additional activation in the bilateral cerebellum, reflecting increased demand on speech motor control, and additional activation in the bilateral temporal cortex, reflecting the stronger involvement of phonologic processing.

Keeping time: effects of focal frontal lesions.

This study examined the performance of 32 normal subjects and 39 patients with focal lesions of the frontal lobes on two simple timing tasks-responding in time with a tone that regularly repeated at a rate of once every 1.5s, and then maintaining the same regular response rhythm without any external stimulus. The hypothesis was that lesions to the right prefrontal cortex would disrupt timing performance. The two main findings were (1) an abnormally high variability in the timing performance (both self-timed and tone-timed) of patients with lesions to the right lateral frontal lobe, particularly involving Brodmann area 45 and subjacent regions of the basal ganglia; (2) an increase in the variability of timing performance as the task continued in patients with lesions to the superior medial regions of the frontal lobe. These findings indicate that the right lateral frontal lobe is crucially involved in the ongoing control of timed behavior, either because of its role in generating time intervals or in monitoring the passage of these intervals. In contrast, the superior medial regions of the frontal lobe are necessary to maintain consistent timing performance over prolonged periods of time.

MEG study of long-term cortical reorganization of sensorimotor areas with respect to using chopsticks.

The movements required to use chopsticks are overlearned and routine in Asians. Most non-Asians, on the other hand, typically have difficulty performing this unfamiliar manual activity, and have to focus their attention on the movements required to use chopsticks adequately. Using magnetoencephalography (MEG) we compared the cortical activation of highly trained Asian chopstick users to the activation of Europeans who only occasionally used chopsticks, while they performed the same tasks with chopsticks or a control task of simple tapping of the same fingers. The data were analyzed using the new method of synthetic aperture magnetometry (SAM). In Europeans there was a significantly higher ratio of spectral power in the higher gamma frequency band (60-80 Hz) over the sensorimotor area compared to the Asian subjects. From these results we conclude that the high gamma band activity in the sensorimotor area may reflect focused attention and functional reorganization of the cortical network with respect to sensorimotor experience.