Neural correlates of motor impairment during motor imagery and motor execution in sub-cortical stroke.

OBJECTIVE: This study aims at identifying the neural substrates for motor execution (ME) and motor imagery (MI) in patients after stroke and their correlations with functional outcomes. METHODS: 10 chronic stroke patients with left sub-cortical lesions and 10 unimpaired subjects were recruited. Their cortical processes were studied when they were asked to perform ME and MI unimanually using their unaffected and affected wrists during fMRI. RESULTS: From correlation results, the supplementary motor area (SMA), its activation volume and congruence in functional neuroanatomy associated with ME and MI using affected wrist positively correlated with motor performance. During ME of the affected wrist, the precuneus, its activation volume and congruence in functional neuroanatomy between patient and unimpaired groups showed a negative correlation, while, in non-primary motor areas, the hemispheric balance of premotor cortex and the congruence in functional neuroanatomy of contralesional inferior parietal lobule between patient and unimpaired groups showed a positive correlation with motor performance. CONCLUSIONS: The non-primary motor-related areas were revealed to play a critical role in determining motor outcomes after left sub-cortical stroke, which was demonstrated in the stroke patients. In particular, SMA might be the key neural substrate associated with motor recovery.

Hierarchical coding of characters in the ventral and dorsal visual streams of Chinese language processing.

Functional and spatial hierarchical organization of increasingly language-like word forms has been proposed for alphabetic languages at the occipitotemporal cortex for visual word recognition. In the logographic Chinese language system, similar functional and spatial hierarchical presentations of brain responses to sublexical orthographic structure are beginning to be explored. In this study, we used whole-brain fMRI to show that a hierarchical coding of increasingly language-like character type is present in multiple Chinese language processing areas. Fluent Chinese readers were presented with Chinese synonyms/non-synonym pairs, identical/non-identical non-pronounceable pseudo-character pairs constructed with Chinese radicals, and identical/non-identical Korean character pairs. We observed the presence of a spatial gradient for increasing language-like character types in the ventral and dorsal visual streams of the cortex. At the left occipitotemporal cortex of the ventral visual stream, we observed a posterior-to-anterior gradient of character type selectivity with the anterior fusiform region being more selective for real Chinese characters and the posterior fusiform region being more selective for Korean characters. At the left and right intraparietal sulci of the dorsal visual stream, a medial-to-lateral gradient of character type selectivity was observed, with the lateral edge being more selective for real Chinese characters, the medial edge being more selective for pseudo-characters, and with less activation attributable to Korean characters. Spatial gradients of selecting character type were also identified in prefrontal cortex, dorsal striatum and lateral temporal cortex. The results suggest that the left occipitotemporal cortex and both left and right intraparietal sulci are tuned with a functional and spatial hierarchical sensitivity to the presence of semantic elements as well as different orthographic structures.

Can Cantonese rhymes be used in the assessment of hemispheric dominance for language?

English vowels had been proposed in previous studies to be used as a simple tool for the brain mapping of language. A proper fMRI study of Cantonese rhymes, each of which being a required and fundamental unit of a Cantonese syllable, remains to be carried out. Using an auditory task with Cantonese rhymes which carry no semantic meaning, we observed a minimal amount of positive BOLD signal at the caudate nucleus when Cantonese rhymes were contrasted with their corresponding filtered sounds. Typical language activating regions of the prefrontal cortex, the medial prefrontal cortex and the lateral temporal cortex on both left and right sides were not activated by Cantonese rhymes. Based on the absence of brain activation at the typical language areas in the contrast of Cantonese rhymes relative to filtered sounds, the auditory task with Cantonese rhymes may not be a robust tool for the individual clinical assessment of hemispheric dominance for language.

Two modes of weight training programs and patellar stabilization.

CONTEXT: Underconditioned patellar stabilizing muscles could be a predisposing factor for patellar instability. OBJECTIVE: To examine the effect of 2 modes of weight training on the size of the vastus medialis obliquus (VMO), the resting position and passive mobility of the patella, and the strength of the knee extensor muscles. DESIGN: Prospective intervention, repeated measures in 3 groups. SETTING: Orthopaedic and sports sciences research laboratory. PATIENTS OR OTHER PARTICIPANTS: 48 healthy adults free from back and lower extremity injuries. INTERVENTION(S): Participants were randomly assigned to muscle hypertrophy training, muscle strength training, or the control group. Those in the training groups pursued training 3 times per week for 8 weeks. MAIN OUTCOME MEASURE(S): Magnetic resonance imaging and ultrasound cross-sectional area of the VMO, patellar tilt angle on magnetic resonance imaging, instrumented passive patellar mobility, and isometric knee extension torque of the dominant leg. RESULTS: Participants in both training groups had comparable gains in VMO size, passive patellar stability, and knee extension force, all of which were greater than for the control group (P < .05). CONCLUSIONS: Both short-term muscle hypertrophy and strength training programs can reinforce the patellar stabilizers in previously untrained volunteers.

Cerebral plasticity after subcortical stroke as revealed by cortico-muscular coherence.

The latency estimation of cortico-muscular coherence (CMCoh) could provide valuable information, especially for the pathological study. However, the conduction time from the central cortical rhythm to peripheral oscillations has not been explored for stroke patients. In this study one recently proposed method, maximizing coherence, was applied into the coherence analysis to estimate the latency by which the extensor carpi radialis electromyographic signals lagged behind the electroencephalographic time series with seven subcortical stroke subjects. Significantly prolonged conduction time was found in affected sides compared with the unaffected sides. The interhemispheric spatial displacement was also calculated using electrodes projection optimization and spherical surface laplacian. The results showed that the CMCoh could help investigate the cerebral reorganization after stroke.

Study on connectivity between coherent central rhythm and electromyographic activities.

Whether afferent feedback contributes to the generation of cortico-muscular coherence (CMCoh) remains an open question. In the present study, a multivariate autoregressive (MVAR) model and partial directed coherence (PDC) were applied to investigate the causal influences between the central rhythm and electromyographic (EMG) signals in the process of CMCoh. The system modeling included activities from the contralateral and ipsilateral primary sensorimotor cortex (M1/S1), supplementary motor area (SMA) and the time series from extensor carpi radialis (ECR) muscles. The results showed that afferent sensory feedback could also play an important role for the generation of CMCoh. Meanwhile, significant coherence between the EMG signals and the activities in the SMA was found in two subjects out of five. Connectivity analysis revealed a significant descending information flow which possibly reflected direct recruitment on the motoneurons from the SMA to facilitate motor control.

Ciprofloxacin-induced palatal tremor.

We describe an 84-year-old man with an unusual clinical presentation of palatal tremor in association with ciprofloxacin treatment. The patient had rhythmical movements not only of the soft palate but also of the face and trunk. Complete resolution of the symptoms occurred 2 days after discontinuation of ciprofloxacin and administration of sodium valproate. This is the first reported case of palatal tremor secondary to the use of ciprofloxacin.

Neuroanatomy of adult strabismus: a voxel-based morphometric analysis of magnetic resonance structural scans.

Cerebral deficit has been implicated in the genesis of strabismus and in the mechanisms adopted to compensate for the visual disorder. Voxel-based morphometry (VBM) was applied to magnetic resonance images of strabismic adults to detect any abnormal brain anatomy, which could not be easily identified by simple inspection. The gray matter volume in strabismic adults was smaller than that in normal subjects at the areas consistent with the occipital eye field (OEF) and parietal eye field (PEF). However, greater gray matter volume was found in strabismic adults relative to normal controls at the areas consistent with the frontal eye field (FEF), the supplementary eye field (SEF), the prefrontal cortex (PFC), and subcortical regions such as the thalamus and the basal ganglia. These opposite gray matter changes in the visual and the oculomotor processing areas are compatible with a hypothesis of plasticity in the oculomotor regions to compensate for the cortical deficits in the visual processing areas.