Yanxiong Huang

In vivo evidence of structural brain asymmetry in musicians.

Certain human talents, such as musical ability, have been associated with left-right differences in brain structure and function. In vivo magnetic resonance morphometry of the brain in musicians was used to measure the anatomical asymmetry of the planum temporale, a brain area containing auditory association cortex and previously shown to be a marker of structural and functional asymmetry. Musicians with perfect pitch revealed stronger leftward planum temporale asymmetry than nonmusicians or musicians without perfect pitch. The results indicate that outstanding musical ability is associated with increased leftward asymmetry of cortex subserving music-related functions.

Increased corpus callosum size in musicians.

Using in-vivo magnetic resonance morphometry it was investigated whether the midsagittal area of the corpus callosum (CC) would differ between 30 professional musicians and 30 age-, sex- and handedness-matched controls. Our analyses revealed that the anterior half of the CC was significantly larger in musicians. This difference was due to the larger anterior CC in the subgroup of musicians who had begun musical training before the age of 7. Since anatomic studies have provided evidence for a positive correlation between midsagittal callosal size and the number of fibers crossing through the CC, these data indicate a difference in interhemispheric communication and possibly in hemispheric (a)symmetry of sensorimotor areas. Our results are also compatible with plastic changes of components of the CC during a maturation period within the first decade of human life, similar to those observed in animal studies.

Large-scale plasticity of the human motor cortex

The adult primate brain is capable of modifying rapidly the size of cortical receptive fields or motor output modules in response to altered synaptic input. We used positron emission tomography (PET) to map the regional cerebral blood flow changes related to voluntary finger movements in patients with tumours occupying the hand area of motor cortex. All patients showed activations solely outside the tumour. Compared with the unaffected side, the activations were shifted by 9-43 mm either along the mediolateral body representation of motor cortex or into premotor or parietal somatosensory cortex. These results provide evidence that slowly developing lesions can induce large-scale reorganization that is not confined to changes within the somatotopic body representation in motor cortex.

Asymmetry of the planum parietale.

Using in vivo magnetic resonance morphometry we measured the posterior wall of the left and right posterior ascending portion of the Sylvian fissure, an inferior parietal area of the brain that we have termed the planum parietale. Among 106 right-handers (53 women and 53 men) and 35 left-handers (18 women and 17 men), handedness and gender exerted an interactive influence on planum parietale asymmetry; right-handed men and left-handed women showed particularly strong rightward asymmetry. There was no correlation between asymmetry of the planum parietale and that of the anatomically adjacent planum temporale, suggesting an independency of these two structural markers of brain laterality.

Sex but no hand difference in the isthmus of the corpus callosum

We performed high-resolution magnetic resonance morphometry of the total midsagittal area and seven midsagittal subareas of the corpus callosum in healthy young adult dextrals and sinistrals (N = 52). There was no influence of handedness on these anatomic measurements. However, an effect of sex emerged, with women (N = 26) having a larger proportional isthmus segment of the callosum. This may reflect a sex-specific difference in the inter-hemispheric connectivity and functional organization of the temporoparietal association cortex.

Representations of graphomotor trajectories in the human parietal cortex: Evidence for controlled processing and automatic performance

The aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right‐hand writing in eight right‐handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole‐field visuospatial processing during automatic performance.

Successive roles of the cerebellum and premotor cortices in trajectorial learning

The structures of the human brain engaged during learning of unilateral trajectorial hand movements were mapped by measurements of regional cerebral blood flow. Trajectorial movement velocity accelerated moderately after short-term training p < 0.025 and increased further after long-term training p < 0.01. During the early phase of learning there was a significant activation p < 0.001 of the ipsilateral dentate nucleus. By contrast, after overlearning the premotor cortical areas in both cerebral hemispheres were maximally activated p < 0.001, while the dentate nucleus was no longer activated. It is suggested that learning of new movement trajectories involves the cerebellum, while overlearned trajectorial movements engage the premotor cortex.

corpus callosum and brain volume in women and men

&NA; Using high‐resolution in vivo magnetic resonance morphometry we measured the midsagittal area of the corpus callosum and total forebrain volume in 120 healthy young adults (mean age (± s.d.) 25.7 ± 4.7 years). The forebrain volume‐adjusted size of the corpus callosum was larger in women than in men (32 mm2 mean difference; p = 0.011). Handedness had no effect in this measurement. The morphometric data confirm a gender difference in cerebral structural organization.

Bilateral reductions of hippocampal volume, glucose metabolism, and Wada hemispheric memory performance are related to the duration of mesial temporal lobe epilepsy

Abstract In refractory temporal lobe epilepsy (TLE) temporal lobe structures and functions are continuously or intermittently affected by abnormal brain electrical events, noxious neurochemical agents, and metabolic disturbances. There is conflicting evidence regarding the relationship between the duration of refractory mesial TLE and quantitative measures of temporal lobe functions and volumes of the hippocampi. Twenty patients (aged 28 ± 7 years, 14 males) with an initial precipitating injury before the age of 5 years were subjected to high-resolution magnetic resonance imaging, fluoro-2-deoxy-d-glucose positron-emission tomography (PET), and the Wada test. We investigated whether the duration of unilateral refractory TLE (12 left, 8 right) affects hippocampal volume, glucose metabolism, or Wada hemispheric memory performance. Ipsilateral to the epileptogenic zone the hippocampal volume, metabolism, and Wada hemispheric memory performance were reduced compared to the corresponding contralateral measures. The duration of epilepsy controlled for age at investigation, side of seizure origin, underlying cause, and sex were negatively correlated with ipsi- and contralateral hippocampal volume, hippocampal metabolism, and Wada hemispheric memory performance. Moreover, ipsilateral Wada hemispheric memory performance and contralateral hippocampal glucose metabolism were correlated with the frequency of habitual seizures. Refractory TLE seems to be associated with a slow but ongoing bilateral temporal lobe damage. These cross-sectional results require verification by longitudinal studies carried out over a period of more than two decades.

In vivo morphometry of planum temporale asymmetry in first-episode schizophrenia

Magnetic resonance imaging is a promising tool for in vivo analysis of the neuropathology underlying schizophrenia. One of the most consistent features emerging from the majority of published studies is the lateralization of pathological findings, and this has led to hypotheses of impaired hemispheric specialization in schizophrenia. In previous work, we have validated morphometry of supratemporal language-related cortex using high-resolution magnetic resonance imaging and analyzed the relation of the so defined planum temporale to functional parameters of hemispheric specialization. In the present study, we examined planum temporale structural asymmetry in first-episode schizophrenics. Asymmetry coefficients obtained in these patients did not differ significantly from those in equally right-handed controls and were not correlated to standard psychopathological measures. These data are contrasted with other studies reporting lateralized brain pathology in schizophrenia with special emphasis on methodological considerations in neuroimaging procedures.