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At least 1,153 records · Page 64Linked to original sources
PubMed2006

The surround inhibition determines therapy-induced cortical reorganization.

Rehabilitation can induce cortical reorganization in chronic stroke patients. In this study we investigated the mechanisms underlying treatment-associated plasticity. Eight patients with a stroke >6 months earlier participated in a 4-week period of physiotherapy based on a forced use concept. Before and after treatment, focal transcranial magnetic stimulation over the affected hemisphere was used to assess the motor output map of the paretic first dorsal interosseous muscle. Using a paired pulse paradigm, intracortical inhibition was investigated at the center of the cortical output map (CoG) and one cm anterior, posterior, lateral and medial of that position. Motor function was evaluated with the Motor Activity Log and the Wolf Motor Function Test. After therapy, the cortical representation size of the affected hand muscle was increased. In each patient, the CoG moved in the direction where intracortical inhibition had been lowest prior to therapy. Significant correlations were found between motor function tests and changes of output map size and CoG shifts, respectively. We conclude that treatment-associated cortical reorganization is influenced by the distribution of inhibitory properties within the representation area prior to therapy, since the CoG moved in the direction of lowest inhibition. The correlations between motor functions and electrophysiological results indicate a functional relevance of the observed reorganization pattern.

Adult↗
PubMed2002

Lateralisation of projections from the rostral ventrolateral medulla to sympathetic preganglionic neurons in the rat.

Spinally projecting sympathoexcitatory neurons in the rostral ventrolateral medulla (RVLM), synapse with sympathetic preganglionic neurons (SPN) and regulate the activity of sympathetic nerves that control the heart, blood pressure and the adrenal medulla (AM). However, the degree of lateralization of the bulbospinal projections to SPN innervating specific targets is poorly understood. Three approaches were used in this study. Anterograde tracer was iontophoresed into a pressor site in the RVLM (left or right) and retrograde tracer injected into the superior cervical ganglion (SCG, right) and the AM (left). Close appositions between anterogradely labelled axons and retrogradely labelled SCG- or AM-SPN were counted. Projections to the SCG were bilateral. Projections to the AM were markedly ipsilateral. In the second part, retrograde tracers were injected unilaterally into the region of the intermediolateral cell column at spinal segment T2 or T8 on one side and the number of labelled neurons in the RVLM counted. The results from each level of injection were similar showing that approximately 63-64% of the neurons were ipsilateral. Responses to glutamate microinjection into the RVLM on adrenal nerve (left) and superior cervical nerve (left) activity were measured. The ratio of the nerve responses was the same even when different sides of the RVLM were injected. The anterograde data strongly suggest that the RVLM projections to AM-SPN are predominantly ipsilateral. Although other experimental approaches also attempted to investigate lateralization, the retrograde data target different and functionally heterogeneous pools of SPN that may mask the ipsilateral projection to the AM. Similarly, chemical stimulation of the RVLM will excite not only monosynaptic projections but also polysynaptic projections that may also mask the predominant ipsilateral monosynaptic projection to AM.

Adrenal Glands↗
PubMed2002

The precedence effect for lateralization for the mild sensory neural hearing impaired.

Using dichotic signals presented by headphone, stimulus onset dominance (the precedence effect for lateralization) was investigated for six sensorineural hearing-impaired subjects. Stimuli were based on 2400-Hz lowpass-filtered 5-ms noise bursts. We used the paradigm, as described by Goverts et al. (2000, Hear. Res. 148, 88-94), in which a single noise burst is divided into leading and lagging parts, with opposite lateralization cues (viz. an interaural time delay of 0.2 ms). The occurrence of onset dominance was investigated by measuring the lateral perception of the stimulus ('left' or 'right') with fixed, equal durations of leading and lagging parts, while decreasing the absolute signal level or adding a filtered white noise. The dominance of the leading part was quantified by measuring the lateral perception of the stimulus as a function of the relative duration of the leading (and thus the lagging) part. This was done at about 40 dB sensation level (SL) in quiet and in filtered white noise, at a signal-to-noise ratio resulting in a SL of about 6 dB. Results are compared to normal hearing reference data at various SLs. Hearing-impaired data show a large variance and overall a decreased precedence effect in terms of both occurrence and quantification, which cannot be explained on basis of reduced audibility. Mean performance of the hearing-impaired subjects at 40 dB in quiet was similar to normal hearing performance in masking noise at a signal-to-noise ratio of 0 dB.

Acoustic Stimulation↗
PubMed1999

Manual laterality and hitting performance in major league baseball.

Asymmetrical hand function was examined in the context of expert sports performance: hitting in professional baseball. An archival study was conducted to examine the batting performance of all Major League Baseball players from 1871 to 1992, focusing on those who batted left (n = 1,059) to neutralize the game asymmetry. Among them, left-handers (n = 421) were more likely to hit with power and to strike out than right-handers (n = 638). One possible account, based on the idea of hand dominance and an analogy to tennis, is that batting left involves a double-handed forehand for left-handers and a weaker and more reliable double-handed backhand for right-handers. The results are also interpretable in the light of Y. Guiard's (1987) kinematic chain model of a between-hands asymmetrical division of labor, which provides a detailed account of why left batting is optimal for left-handers.

Baseball↗
PubMed2006

The yolk syncytial layer regulates myocardial migration by influencing extracellular matrix assembly in zebrafish.

The roles of extra-embryonic tissues in early vertebrate body patterning have been extensively studied, yet we know little about their function during later developmental events. Here, we analyze the function of the zebrafish extra-embryonic yolk syncytial layer (YSL) specific transcription factor, Mtx1, and find that it plays an essential role in myocardial migration. Downregulating the function of Mtx1 in the YSL leads to cardia bifida, a phenotype in which the myocardial cells fail to migrate to the midline. Mtx1 in the extra-embryonic YSL appears to regulate the embryonic expression of fibronectin, a gene previously implicated in myocardial migration. We further show dosage-sensitive genetic interactions between mtx1 and fibronectin. Based on these data, we propose that the extra-embryonic YSL regulates myocardial migration, at least in part by influencing fibronectin expression and subsequent assembly of the extracellular matrix in embryonic tissues.

Animals↗
PubMed1996

A gain-of-function of an amyotrophic lateral sclerosis-associated Cu,Zn-superoxide dismutase mutant: An enhancement of free radical formation due to a decrease in Km for hydrogen peroxide.

Cu,Zn-superoxide dismutase (SOD) is known to be a locus of mutation in familial amyotrophic lateral sclerosis (FALS). Transgenic mice that express a mutant Cu,Zn-SOD, Gly-93--> Ala (G93A), have been shown to develop amyotrophic lateral sclerosis (ALS) symptoms. We cloned the FALS mutant, G93A, and wild-type cDNA of human Cu,Zn-SOD, overexpressed them in Sf9 insect cells, purified the proteins, and studied their enzymic activities for catalyzing the dismutation of superoxide anions and the generation of free radicals with H2O2 as substrate. Our results showed that both enzymes contain one copper ion per subunit and have identical dismutation activity. However, the free radical-generating function of the G93A mutant, as measured by the spin trapping method, is enhanced relative to that of the wild-type enzyme, particularly at lower H2O2 concentrations. This is due to a small, but reproducible, decrease in the value of Km for H2O2 for the G93A mutant, while the kcat is identical for both enzymes. Thus, the ALS symptoms observed in G93A transgenic mice are not caused by the reduction of Cu,Zn-SOD activity with the mutant enzyme; rather, it is induced by a gain-of-function, an enhancement of the free radical-generating function. This is consistent with the x-ray crystallographic studies showing the active channel of the FALS mutant is slightly larger than that of the wild-type enzyme; thus, it is more accessible to H2O2. This gain-of-function, in part, may provide an explanation for the association between ALS and Cu,Zn-SOD mutants.

Amyotrophic Lateral Sclerosis↗
PubMed2000

Salivary testosterone concentrations in left-handers: an association with cerebral language lateralization?

The level of testosterone exposure in early brain development may influence the direction or degree of cerebral language lateralization. Possible links between individual differences in testosterone levels and patterns of speech representation were investigated in 180 healthy young adults (97 left handed, 83 right handed) using the Fused Dichotic Words Test (T. Halwes, 1991). Among left-handed participants, significantly higher testosterone concentrations were observed in individuals with a left-ear advantage on dichotic listening than in individuals with a right-ear advantage. Among right-handed participants, the pattern of group differences in testosterone tended to be reversed, resulting in a statistically significant interaction. Results extend prior findings by S. D. Moffat and E. Hampson (1996a) and raise the possibility that higher testosterone is associated with patterns of brain organization in which speech and praxic functions are lateralized to the same hemisphere.

Adult↗
PubMed2000

[Treatment of sixth nerve palsy of traumatic or tumor etiology using botulinum toxin].

PURPOSE: To study the treatment of sixth nerve palsies of traumatic or tumoral etiologies using botulinum toxin. The factors and possible influences are analysed. METHODS: 35 patients with unilateral sixth nerve palsy are studied, 21 presenting traumatic (group I) and 14 with tumoral etiology (group II). They have been treated with botulinum toxin into the medial rectus muscle, using topical anesthesia. In group I the mean preoperative deviation was 59 diopters, in group II it was 37 diopters. The follow-up time, the initial deviation, the dose, the number of injections, the colateral effects and the final results are analyzed. RESULTS: In group I, the mean number of injections was 1.7, and the dose 10.23 international units, success was achieved in 38% of the patients, better results are obtained when treatment is injected within six months after traumatism, when less initial deviation and better initial lateral muscle function are present. In group II, the mean number of injections was 1.5 and the dose 8.21 international units, success was achieved in 57%, no influence among these factors was found. CONCLUSIONS: We consider useful to treat the traumatic palsy with botulinum toxin within six months after traumatism. The results depend on the initial deviation and the previous lateral muscle function. It is also useful as a chronic treatment and as a diagnosis procedure.

Abducens Nerve Diseases↗
PubMed2006

Cognitive functioning in sporadic amyotrophic lateral sclerosis: a six month longitudinal study.

OBJECTIVE: To observe changes in cognition over six months in subjects with recently diagnosed sporadic amyotrophic lateral sclerosis (ALS). METHODS: The study used a between-group and within-group longitudinal design. Nineteen ALS subjects and eight matched caregivers were recruited to participate in baseline neuropsychological assessments that were repeated six months later. Between group comparisons for these variables were undertaken at baseline and six months later. Within group/across time comparisons for these variables were carried out for both groups. Individual analyses for the neuropsychological variables using z scores were done for the ALS subjects using their baseline performance as the basis for comparison with their six month performance. RESULTS: The between-group and within-group comparisons did not show significant differences in cognitive function over time. In individual analyses, however, seven of 19 ALS subjects (36.84%) developed abnormal neuropsychological performance over six months. CONCLUSIONS: Early in the disease course, over one third of the ALS subjects developed cognitive deficits over six months. These findings support the hypothesis that cognitive deficits in ALS become more prominent over time.

Aged↗
PubMed2004

Prefrontal cortex asymmetry for memory encoding of words and abstract shapes.

Previous work suggested a differential contribution of prefrontal cortex (PFC) to successful encoding depending on the stimulus material. Here, we tested the hypothesis that encoding of words preferentially involves the left PFC, while encoding of nonverbal items (abstract shapes) relies on the right PFC. We used an experimental design that evaluated encoding of both words and abstract shapes in the same healthy volunteers. A transient virtual lesion of the left or the right PFC was elicited with transcranial magnetic stimulation (TMS) while subjects memorized verbal and nonverbal items. We found that encoding of verbal material was disrupted by left PFC stimulation, whereas encoding of nonverbal material was disrupted by right PFC stimulation. These results demonstrate a functionally relevant lateralization of prefrontal contribution for verbal and nonverbal memory encoding.

Adult↗
PubMed2003

On the lateralization of emotional prosody: an event-related functional MR investigation.

In order to investigate the lateralization of emotional speech we recorded the brain responses to three emotional intonations in two conditions, i.e., "normal" speech and "prosodic" speech (i.e., speech with no linguistic meaning, but retaining the 'slow prosodic modulations' of speech). Participants listened to semantically neutral sentences spoken with a positive, neutral, or negative intonation in both conditions and judged how positive, negative, or neutral the intonation was on a five-point scale. Core peri-sylvian language areas, as well as some frontal and subcortical areas were activated bilaterally in the normal speech condition. In contrast, a bilateral fronto-opercular region was active when participants listened to prosodic speech. Positive and negative intonations elicited a bilateral fronto-temporal and subcortical pattern in the normal speech condition, and more frontal activation in the prosodic speech condition. The current results call into question an exclusive right hemisphere lateralization of emotional prosody and expand patient data on the functional role of the basal ganglia during the perception of emotional prosody.

Adult↗
PubMed1999

Possible evolutionary origins of cognitive brain lateralization.

Despite the substantial literature on the functional architecture of the asymmetries of the human brain, which has been accumulating for more than 130 years since Dax and Broca's early reports, the biological foundations of cerebral asymmetries are still poorly understood. Recent advances in comparative cognitive neurosciences have made available new animal models that have started to provide unexpected insights into the evolutionary origins and neuronal mechanisms of cerebral asymmetries. Animal model-systems, particularly those provided by the avian brain, highlight the interrelations of genetic, hormonal and environmental events to produce neural and behavioural asymmetries. Novel evidences showing that functional and structural lateralization of the brain is widespread among vertebrates (including fish, reptiles and amphibians) have accumulated rapidly. Perceptual asymmetries, in particular, seem to be ubiquitous in everyday behaviour of most species of animals with laterally placed eyes; in organisms with wider binocular overlap (e.g., amphibians), they appear to be retained for initial detection of stimuli in the extreme lateral fields. We speculate that adjustment of head position and eye movements may play a similar role in mammals with frontal vision as does the choice for right or left lateral visual fields in animals with laterally placed eyes. A first attempt to trace back the origins of brain asymmetry to early vertebrates is presented, based on the hypothesis that functional incompatibility between the logical demands associated with very basic cognitive functions is central to the phenomenon of cerebral lateralization.

Animals↗
PubMed2001

Functional reconstruction of the lateral face after ablative tumor resection: use of free muscle and musculocutaneous flaps.

BACKGROUND: Wide resection of tumors of the middle third of the face often results in complex three-dimensional defects and facial paralysis either due to removal of the facial nerve within the tumoral tissue or to extensive resection of the facial muscles. METHODS: We report the cases of three patients who underwent wide excision of tumors of the cheek region, operations that resulted in tissue defects and facial palsy. Defect reconstruction and facial reanimation was accomplished in one stage through functional muscle transplantation. RESULTS: Follow-up of more than 1 year showed good symmetry at rest and reanimation of the corner of the mouth in all cases, but one patient, in which the ipsilateral facial main trunk was used as motor nerve supply to the transplanted muscle, developed significant muscle contracture and binding of the cheek skin. CONCLUSIONS: Every effort should be made to optimize the functional and cosmetic outcomes of neurovascular muscle transfers through precise planning and careful execution of the intricate details of the surgical technique for muscle transplantation.

Adolescent↗
PubMed1998

Reproducibility of functional transcranial Doppler sonography in determining hemispheric language lateralization.

BACKGROUND AND PURPOSE: Since functional transcranial Doppler ultrasonography (fTCD) allows convenient and fully automated quantification of language lateralization, it seems ideal for longitudinal studies of perfusion changes during deterioration as well as recovery of language functions. However, during serial examinations, the technical, stochastic, and physiological variabilities of cerebral blood flow velocities (CBFV) have to be considered. Therefore, before fTCD is accepted as a tool for evaluation of changes in lateralization in the diseased state, its reliability in healthy subjects needs to be determined. METHODS: We performed fTCD during a word generation task based on a previously validated technique with automated calculation of the averaged CBFV differences in the middle cerebral arteries providing an index of lateralization (LI). RESULTS: (1) The accuracy of the LI as assessed by the confidence interval was better than 1% of the mean hemispheric difference. (2) On repeated examination, LIs obtained from 10 subjects showed a high test-retest reproducibility (Pearson product moment correlation coefficient r = 0.95, P < 0.0001). (3) On 10 repeated assessments of LI in the same subject, no practice effects were detected. CONCLUSIONS: Functional TCD is a suitable and very robust tool for the longitudinal quantitative measurement of cerebral language lateralization.

Adult↗
PubMedDate not supplied

Methods to evaluate the sample volume of pulsed Doppler systems.

The spatial resolution of a pulsed Doppler system heavily depends on both the characteristics of the ultrasound transducer and the processing circuitry. The local characteristics of the ultrasound beam give the lateral sample function while the way the signals are processed affects the axial shape of the sample volume. A simple way to explore the size of the sample volume is the employment of a running string target. However, the detected Doppler signals will be the sum of all the Doppler signals returned by the string along its course through the sample volume. Therefore, it will be complicated to separate the axial and lateral contribution to the actual size of the sample volume. A scanning system capable of visualizing the cross-sectional distribution of the ultrasound intensity allows the assessment of the sample sensitivity in lateral direction. A single vibrating point target enables the exploration of both the axial and lateral sampling function. The latter approach is especially suited to evaluate routinely the spatial performance of pulsed Doppler systems in clinical practice.

Humans↗
PubMed2005

Spatial properties of central vestibular neurons of monkeys after bilateral lateral canal nerve section.

Thirty-seven neurons were recorded in the superior vestibular nucleus (SVN) of two cynomolgus monkeys 1-2 yr after bilateral lateral canal nerve section to test whether the central neurons had spatially adapted for the loss of lateral canal input. The absence of lateral canal function was verified with eye movement recordings. The relation of unit activity to the vertical canals was determined by oscillating the animals about a horizontal axis with the head in various orientations relative to the axis of rotation. Animals were also oscillated about a vertical axis while upright or tilted in pitch. In the second test, the vertical canals are maximally activated when the animals are tilted back about -50 degrees from the spatial upright and the lateral canals when the animals are tilted forward about 30 degrees . We reasoned that if central compensation occurred, the head orientation at which the response of the vertical canal-related neurons was maximal should be shifted toward the plane of the lateral canals. No lateral canal-related units were found after nerve section, and vertical canal-related units were found only in SVN not in the rostral medial vestibular nucleus. SVN canal-related units were maximally activated when the head was tilted back at -47 +/- 17 and -50 +/- 12 degrees (means +/- SD) in the two animals, close to the predicted orientation of the vertical canals. This indicated that spatial adaptation of vertical canal-related vestibular neurons had not occurred. There were substantial neck and/or otolith-related inputs activating the vertical canal-related neurons in the nerve-sectioned animals, which could have contributed to oculomotor compensation after nerve section.

Action Potentials↗