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PubMed1999

Corticostriatal plasticity is restricted by myelin-associated neurite growth inhibitors in the adult rat.

After unilateral cortical lesions in neonatal rats, the spared unablated hemisphere is known to demonstrate remarkable neuroanatomical plasticity in corticofugal connectivity. This same type of structural plasticity is not seen after similar lesions in adult rats. One possibility for the lack of such a plastic response in the adult central nervous system may be the presence of myelin-associated neurite growth inhibitory proteins NI-35/NI-250. These proteins have previously been found to play a crucial role in preventing axotomized fibers from regenerating after adult rat spinal cord lesions. The aim of this study was to determine if blocking these inhibitory proteins by the application of the specific monoclonal antibody IN-1 would enhance corticostriatal plasticity from the spared hemisphere after unilateral cortical lesions in adult rats. Six- to 8-week-old Lewis rats underwent unilateral aspiration lesion of the sensorimotor cortex. Animals were immediately treated with either monoclonal antibody IN-1 or a control antibody released from hybridoma cells in Millipore filter capsules. After a survival period of 12 weeks, the opposite sensorimotor cortex was stereotaxically injected with the anterograde tracer biotinylated dextran amine, and biotinylated dextran amine-positive corticostriatal fibers were analyzed. The monoclonal antibody IN-1-treated animals showed an increase in corticostriatal fibers in the dorsolateral striatum contralateral to the injection site compared with control antibody-treated animals or normal controls, indicating a specific sprouting response in the deafferented zone. These results support the idea that through blockade of myelin-associated neurite inhibitory proteins, lesion-induced corticofugal plasticity is possible even in the adult central nervous system.

Animals↗
PubMed2003

The importance of the dominant hemisphere in the organization of bimanual movements.

The successful control of upper limb movements is an essential skill of the human motor system. Yet, the neural organization of bimanual actions remains an issue of debate. Their control can be directed from both hemispheres, or, coordinated motion might be organized from the dominant (left) hemisphere. In order to unravel the neural mechanisms of bimanual behavior, we analyzed the standard task-related and directed coherence between EEG signals picked up over the primary sensorimotor cortices in right-handed subjects during unimanual as well as bimanual in-phase (symmetrical) and anti-phase (asymmetrical) movements. The interhemispheric coherence in the beta frequency band (>13-30 Hz) was increased in both unimanual and bimanual patterns, compared to rest. During unimanual actions, the drive in the beta band from one primary sensorimotor cortex to the other was greater during movement of the contralateral as opposed to ipsilateral hand. In contrast, during bimanual actions, the drive from the dominant to the non-dominant primary sensorimotor cortex prevailed, unless task constraints induced by an external perturbation resulted in a substantial uncoupling of the hand movements, when interhemispheric coherence would also drop. Together, these results suggest that the contralateral hemisphere predominantly organizes unimanual movements, whereas coupled bimanual movements are mainly controlled from the dominant hemisphere. The close association between changes in interhemispheric coupling and behavioral performance indicates that synchronization of neural activity in the beta band is exploited for the control of goal-directed movement.

Adult↗
PubMed1987

Regional differences in the cat caudate nucleus as to the effectiveness in inducing contraversive head-turning by electrical stimulation.

An attempt was made to re-examine regional differences in the cat caudate nucleus as to the effectiveness in inducing contraversive head-turning by electrical stimulation and to analyze the time course of head-turning quantitatively. In 5 of the total 9 cats, the right sensorimotor cortex and its surrounding areas had been ablated chronically. While the awake, unrestrained cat maintained a stable standing posture facing forward, stimulation was applied systematically to various points in and around the caudate nucleus with a movable stimulating electrode. Trains of stimulating current pulses of less than 300 microA were given, mostly at a rate of 100 Hz for 5 s. In most experiments in which stimulation was given to the side of the intact cerebral cortex, stimulation of caudal portions of the head of the caudate nucleus was effective in inducing contraversive head-turning, but that of its rostral portions was ineffective. In experiments on the side of chronic cortical ablation, similar results were obtained. These results suggested that head-turning induced by stimulation of the caudate nucleus was brought about not by the activation of the corticofugal fibers from these cortical areas by a current spreading to the internal capsule, but by the activation of caudate neurons. Hence, it was demonstrated that there were regional differences in the cat caudate nucleus as to the effectiveness in inducing head-turning. The mean of the shortest latencies of the onset of head-turning for individual stimulation points was 396 ms (S.D., 210 ms) for the side of the intact cerebral cortex, and 454 ms (S.D., 289 ms) for the side of the cortical ablation. Statistically, there was no significant difference between them. Therefore, it was further revealed that the elimination of the sensorimotor cortex did not affect the caudate-induced head-turning in terms of the latency of its onset.

Animals↗
PubMed2003

Evaluation of extracranial-intracranial arterial bypass function by using near-infrared spectroscopy.

OBJECT: It has been reported that extracranial-intracranial (EC-IC) arterial bypass surgery can be useful in preventing stroke in patients with hemodynamic compromise. Little is yet known, however, regarding the extent to which the bypass contributes to maintaining adequate cerebral blood oxygenation (CBO) and its temporal changes following surgery. The authors evaluated bypass function repeatedly by using near-infrared spectroscopy (NIRS) after surgery. METHODS: The authors investigated 30 patients who had undergone EC-IC bypass surgery. Single-photon emission computerized tomography revealed a decrease in regional cerebral blood flow (rCBF) and a lowered rCBF response to acetazolamide. Changes in CBO were evaluated in the sensorimotor cortex during compression of the anastomosed superficial temporal artery (STA). When decreases in oxyhemoglobin (HbO2) and total hemoglobin (Hb) concentrations were observed, the bypass was considered to have maintained CBO in the sensorimotor cortex given that decreases in HbO2 and total Hb indicate cerebral ischemic changes. The bypass maintained CBO immediately after surgery in 36.7% of patients (Group I, 11 patients) and at some time after surgery, mostly within 1 year, in 43.3% of patients (Group II, 13 patients); however, it did not maintain it throughout the follow-up period in 20% of patients (Group III, six patients). Note that the preoperative rCBF in patients in Groups I and II was lower than that in patients in Group III (p < 0.004). In fact, the preoperative rCBF predicted whether a bypass would maintain CBO at a cutoff value of 24.5 to 25 ml/100 g/min. Among Groups I and II, 18 patients demonstrated an increase in deoxyhemoglobin during STA compression. The preoperative rCBF in these cases was lower than that in the six remaining patients (p < 0.006). Note that the preoperative rCBF predicted the postoperative deoxyhemoglobin response at a cutoff value of 22.2 to 24 ml/100 g/min. CONCLUSIONS: The EC-IC bypass surgery can maintain CBO immediately after surgery or gradually within 1 year when the preoperative rCBF is below 24.5 to 25 ml/100 g/min. Furthermore, bypass flow plays a critical role in maintaining an adequate CBO when preoperative rCBF is below 22.2 to 24 ml/100 g/min.

Acetazolamide↗
PubMed1994

Topographic specificity of corticospinal connections formed in explant coculture.

The corticospinal pathway connects layer V pyramidal neurons in discrete regions of the sensorimotor cortex to topographically matching targets in the spinal cord. In rodents initial pathway errors occur transiently during early postnatal development, such that visual cortical axons project inappropriately into the corticospinal tract. Nevertheless, only sensorimotor axons form corticospinal connections, which are topographically ordered in hamsters from the earliest stages of innervation. Previous work in vivo suggests that pathfinding is carried out by primary cortical axons whereas target innervation occurs by extension of axon collaterals at appropriate locations. In vitro studies have provided evidence that chemotropic factors may selectively attract extension of neurites into specific targets. To investigate the basis for corticospinal target selection during development, we have used an in vitro explant coculture system. Sensorimotor and visual cortical explants from newborn hamsters were presented with inappropriate targets from olfactory bulb and cerebellum and targets from the cervical (forelimb) and lumbar (hindlimb) enlargements of the early postnatal spinal cord. Under in vitro conditions, corticospinal target selection was highly specific and remarkably similar to corticospinal connectivity in vivo. Visual and sensorimotor cortical neurites extended nonselectively into the white matter of the spinal cord. However, only neurites from the sensorimotor cortex were able to extend into and arborize within the spinal gray. In the majority of cases, these connections were topographically appropriate, matching forelimb cortex to cervical cord and hindlimb cortex to lumbar cord. However, we found no evidence that chemotropic attraction was responsible for selection of appropriate targets by cortical neurites or that spinal target tissue promoted extension of cortical axon collaterals within the collagen matrix. These results suggest that the ability of cortical neurites to recognize correct spinal targets and form terminal arbors may require direct axon target interaction.

Animals↗
PubMed2002

Alterations of the neocortical GABAergic system in the pilocarpine model of temporal lobe epilepsy: neuronal damage and immunocytochemical changes in chronic epileptic rats.

A wealth of previous studies reported pathological alterations in extrahippocampal regions in mesial temporal lobe epilepsy. Previous experimental findings have also demonstrated that the entorhinal cortex and the neocortex are damaged in different animal models of acute limbic seizures. The present study was aimed at verifying possible alterations in neocortical areas, and, in particular, structural changes of GABAergic interneurons in the sensorimotor cortex, in pilocarpine-induced chronic epilepsy in the rat. Series of sections were Nissl stained and processed for immunocytochemistry using antibodies that recognize nonphosphorylated neurofilament (SMI311), glial fibrillary acidic protein (GFAP), the calcium-binding protein parvalbumin (PV) which is expressed by a subset of cortical GABAergic neurons, the GABA transporter (GAT1), and isoform 65 of glutamic acid decarboxylase (GAD65), the GABA synthetic enzyme. Epileptic rats showed decreased cortical thickness, and diffuse gliosis was observed with GFAP antibody. Neurofilament alterations were also detected in sections processed using SMI311 antiserum. In addition, a diffuse decrease of PV, GAD65, and GAT1 immunoreactivity was observed in the sensorimotor cortex. Altered expression of PV, GAD65, and GAT1 pointed out specific neocortical disturbances in GABAergic inhibition, which could play a crucial role in seizure generation and expression. Thus, the present findings indicate that damage of GABAergic interneurons could be strictly associated with neocortical hyperexcitability in temporal lobe epilepsy.

Animals↗
PubMedDate not supplied

[Evoked potentials of the dog sensomotor cortex following systematic application of series of electrocutaneous stimuli].

Standard 5-member series of weak electro-cutaneous stimulations of the fore-paw were applied in chronic experiments to two dogs with implanted cortical electrodes. The stimuli caused no apparent motor reactions and were not reinforced by any other type of stimulation. Evoked potentials (EP) in the sensorimotor cortex were gradually forming in the course of experiments in such a way that the amplitude of averaged EPs to the extreme stimuli of the series became larger than those to the middle ones. The elaborated U-shaped dependence of the averaged EP amplitudes in the sensorimotor cortex on the ordinal number of the electrical stimuli correlates with the same EP dependence observed in the auditory cortex of dogs in response to series of clicks. The described form of EP organization in response to the stimuli of one modality facilitates the elaboration of the same type of organization in response to the stimuli of an other modality.

Animals↗
PubMed2003

Three-dimensional MRI of cerebral projections in rat brain in vivo after intracortical injection of MnCl2.

In this study we investigated the potential of in vivo MRI detection of axonal Mn2+ transport for tracing neuronal projections originating in the sensorimotor cortex in healthy and lesioned rat brains. Special attention was given to the potential of visualizing neuronal sprouting of central nervous system across the midline. After injecting unchelated MnCl2 into the forelimb area of sensorimotor cortex of 18 healthy and 10 lesioned rats corticofugal projections could be traced through the internal capsule to the cerebral peduncle and the pyramidal decussation. Although the neuronal tract was visible as early as 6 h after MnCl2 injection, best contrast was achieved after 24-48 h. Beside the cortico-spinal tract, the cortico-thalamic fibres were also visualized by anterograde Mn2+ transport. Cortico-striatal fibres were partially masked by the very high signal near the MnCl2 injection site but could be discerned as well. Slight, diffuse signal enhancement of cortical tissue contralateral to the MnCl2 injection site in healthy rat brains suggests interhemispheric connections or passive diffusion of Mn2+. However, enhanced fibre tract contrast connecting both hemispheres was visible 16 weeks after onset of focal photothrombotic cortical injury. In conclusion our study has shown that we were able to visualize reproducibly the main descending corticofugal projections and interhemispheric connections by non-invasive MRI after localized injection of MnCl2. The appearance of interhemispheric Mn2+-enhanced fibres after photothrombotic focal injury indicates that the method may bear potential to follow non-invasively gross plastic changes of connectivity in the brain after injury.

Animals↗
PubMed2004

The cerebral oscillatory network associated with auditorily paced finger movements.

Motor tasks involve neural activity in a spatially distributed network. It is assumed that coherent activity between these brain structures reflects functional connectivity. The aim of the present study was to investigate brain areas associated with a unimanual auditorily paced finger-tapping task and to characterize their dynamic interplay. We examined cerebromuscular and cerebrocerebral coupling in 10 right-handed subjects using recordings of continuous brain activity with a 122-channel whole-head neuromagnetometer while subjects performed the task with both hands consecutively. Additionally, surface EMG of the first dorsal interosseus was measured. Our data demonstrate that an oscillatory network composed of primary sensorimotor cortex, lateral as well as mesial premotor areas, the posterior parietal cortex and thalamus contralateral, and cerebellum and primary auditory cortex ipsilateral to the tapping hand subserves task execution. Connectivity between these areas and direction of coupling agree well with anatomical findings. During the right-hand condition, additional oscillatory activity in the primary sensorimotor cortex ipsilateral to the tapping hand was evident. This result suggests an asymmetric motor control in right-handers. Cerebrocerebral coupling predominantly occurs at 8-12 Hz. Therefore, our data support the hypothesis that coupling at 8-12 Hz in a cerebello-thalamic-cortical network represents a fundamental characteristic of the motor system and provides evidence for the significance of 8-12 Hz oscillations in a large scale network during the execution of simple motor tasks.

Acoustic Stimulation↗
PubMed1980

Microelectrode analysis of the cellular mechanisms of conditioned reflex in rabbits.

Spikes and postsynaptic potentials (PSPs) were recorded in the sensorimotor cortex of awake rabbits. (1) A cellular analog of cortico-cortical conditioned reflex (CR) was studied. Direct cortical stimulation of a remote point (conditional stimulus - CS) was paired with the stimulation near the microelectrode insertion (unconditional stimulus - UCS). The most neurons showed response facilitation when short intertrial intervals and strong UCS were used. These changes were short-lasting (up to 30 s) and were explained by posttetanic potentiation. Of 21 units tested with long (7 to 120 s) intertrial intervals, 9 showed significant response modification of longer duration. (2) The analog of cortico-cortical CR was modified using stimulation of homolateral cortex as the CS. The UCS was complimented by lateral hypothalamic reinforcement (LHR) in instrumental or classical paradigm. Of 37 units tested, 5 showed an increase in the probability of short-latency ( less than 25 ms) spike. (3) Extracellular activity of 17 neurons was followed through the entire cycle of elaboration and extinction of a "local conditioned startle response" established by pairing click CS with cortical UCS and LHR. Responses of 7 neurons showed significant modifications. The latency distributions of averaged PSPs were compared for naive (N), conditioned (C) and extinguished (E) states. Latencies in N and E groups were similar but were different from those in C group. Of 41 C group neurons, 26 responded at a latency of less than 17 ms; and 9 responded after less than or equal to 7 ms. A pathway for this simple CR may pass through the cortex. Thus PSP changes were observed in all models. Augmentation of short-latency EPSPs support the idea that an increase in efficacy of excitatory synapses underlies the conditioning. Interneuronal excitatory connections within the sensorimotor cortex are, presumably changed during elaboration of simplest motor CRs. These connections can be analyzed with intracellular recordings triggered by spikes of a neighbouring neuron.

Animals↗
PubMed2002

Neurophysiological correlates of age-related changes in human motor function.

BACKGROUND: There are well-defined and characteristic age-related deficits in motor abilities that may reflect structural and chemical changes in the aging brain. OBJECTIVE: To delineate age-related changes in the physiology of brain systems subserving simple motor behavior. METHODS: Ten strongly right-handed young (<35 years of age) and 12 strongly right-handed elderly (>50 years of age) subjects with no evidence of cognitive or motor deficits participated in the study. Whole-brain functional imaging was performed on a 1.5-T MRI scanner using a spiral pulse sequence while the subjects performed a visually paced "button-press" motor task with their dominant right hand alternating with a rest state. RESULTS: Although the groups did not differ in accuracy, there was an increase in reaction time in the elderly subjects (mean score plus minus SD, young subjects = 547 +/- 97 ms, elderly subjects = 794 +/- 280 ms, p < 0.03). There was a greater extent of activation in the contralateral sensorimotor cortex, lateral premotor area, supplementary motor area, and ipsilateral cerebellum in the elderly subjects relative to the young subjects (p < 0.001). Additional areas of activation, absent in the young subjects, were seen in the ipsilateral sensorimotor cortex, putamen (left > right), and contralateral cerebellum of the elderly subjects. CONCLUSIONS: The results of this study show that elderly subjects recruit additional cortical and subcortical areas even for the performance of a simple motor task. These changes may represent compensatory mechanisms invoked by the aging brain, such as reorganization and redistribution of functional networks to compensate for age-related structural and neurochemical changes.

Adult↗
PubMed1999

Electroencephalographic analysis of cortico-muscular coherence: reference effect, volume conduction and generator mechanism.

OBJECTIVE: To measure the synchrony between cortical and muscle oscillatory activities, the coherence estimate between EEG and EMG was computed. METHODS: The multichannel electroencephalogram (EEG) and electromyogram (EMG) of the right abductor pollicis brevis muscle were recorded in 5 normal volunteers. Various types of EEG derivation methods were systematically compared to establish a standard method to study cortico-muscular coupling. RESULTS: The use of a reference-free EEG derivation (current source density) greatly improved cortico-muscular coherence. In all subjects, EEGs over the left sensorimotor cortex were coherent with EMG (mean peak frequency: 18.7 Hz, mean highest coherence: 0.124). The time lag from cortex to muscle in 14-50 Hz was 14.3 ms. EEG source derivation revealed that both radial and tangential generators in the precentral cortex might contribute to this phenomenon. In the EEG signals using common average reference, an artifactual coherence peak over the medial frontal area was observed, which might largely be explained by volume conduction from the primary sensorimotor cortex. CONCLUSIONS: We conclude that the current source density or its approximation is preferable to estimate the cortico-muscular coherence and that the interpretation of such coherence using referenced EEGs should be taken with care.

Algorithms↗
PubMed1995

The silent period induced by transcranial magnetic stimulation in muscles supplied by cranial nerves: normal data and changes in patients.

The silent period induced by transcranial magnetic stimulation of the sensorimotor cortex (Magstim 200, figure of eight coil, loop diameter 7 cm) in active muscles supplied by cranial nerves (mentalis, sternocleidomastoid, and genioglossus) was studied in 14 control subjects and nine patients with localised lesions of the sensorimotor cortex. In the patients, measurements of the silent period were also made in the first dorsal interosseus and tibialis anterior muscles. In the controls, there was a silent period in contralateral as well as ipsilateral cranial muscle and the duration of the silent period increased with increasing stimulus intensities. The mean duration of the silent period was around 140 ms in contralateral mentalis muscle and around 90 ms in contralateral sternocleidomastoid muscle at 1.2 x threshold stimulation strengths. Whereas the duration of the silent period in ipsilateral mentalis muscle was shorter than on the contralateral side it was similar on both sides in sternocleidomastoid muscle. In patients with focal lesions of the face associated primary motor cortex and corresponding central facial paresis, the silent period in mentalis muscle was shortened whereas it was unchanged or prolonged in limb muscles (first dorsal interosseus, tibialis anterior) with stimulation over the affected hemisphere. By contrast, in a patient with a lesion within the parietal cortex, the silent period in mentalis muscle was prolonged with stimulation of the affected side.

Adult↗
PubMed1992

[Pitfalls in cortical localization by intraoperative recording of cortical somatosensory evoked potentials].

Cortical somatosensory evoked potential (SEP) recordings were made in 11 patients who had lesions located in or near the somatosensory or motor gyri to localize the central sulcus and sensorimotor cortex during neurosurgical operations. Cortical localization was successful in 7 of the 11 patients by recording phase reversal waveforms of N20 and P20 at electrode sites in the hand area on opposite sides of the central sulcus. There were 4 cases in which the cortical localization failed. Locations of craniotomy were far distant from the central sulcus retrospectively in 2 of the 4 patients. Cortical SEPs couldn't be recorded despite probable exposure of the hand area and apparently adequate stimulation and recording conditions in 2 patients who had showed no or low amplitude scalp SEP preoperatively. In one of these 2 patients only low amplitude negative waves were recorded at the cortex which was thought far field potentials originated from subcortical structures. In 2 patients cortical SEP was monitored during the removal of the tumors and was useful to estimate the effects of the operative procedures on the sensorimotor cortex. It is concluded that the localization of cortical functions using cortical SEP is useful for reducing risk associated with intracranial surgery. However, we must be aware that there are some pitfalls in this method.

Adolescent↗
PubMed1989

The organization of the projection from the cerebral cortex to the striatum in the rat.

The detailed organization of the corticostriate projection has been investigated in the brain of the rat using the technique of retrograde transport of horseradish peroxidase following the placement of small, iontophoretic injections of horseradish peroxidase conjugated to lectin throughout all major regions of the striatum (caudate-putamen, nucleus accumbens and olfactory tubercle). The results demonstrate that all major regions of the cerebral cortex project to the striatum on both sides of the brain with an ipsilateral predominance. The cells of origin of both the ipsilateral and contralateral corticostriate projections lie mainly in lamina V (especially lamina Va) with very small numbers in lamina III of the neocortex and mesocortex, and in the deep laminae of the allocortex. The results show that each striatal locus receives inputs from several cortical regions, i.e. there is extensive overlap in the corticostriate projection, and that, in general terms, each cortical region projects onto a longitudinally oriented region of the striatum. In particular, the major subdivisions of the cerebral cortex--the neocortex, mesocortex and allocortex--project onto defined but partially overlapping regions of the striatum: the neocortex projects to the caudate-putamen; the mesocortex projects mainly to the medial and ventral regions of the caudate-putamen but also to the ventral striatum (nucleus accumens and olfactory tubercle); and the allocortex projects mainly to the ventral striatum but also to the medial and ventral parts of the caudate-putamen. Within each of these major projection systems there is a further organization, with the constituent parts of each major cortical region projecting to smaller longitudinal components of the major projection fields. Each neocortical area projects to a longitudinal region of the dorsal striatum (caudate-putamen): the sensory and motor areas project topographically onto the dorsolateral striatum such that the rostral sensorimotor cortex (head areas) projects to central and ventral regions and the more caudal sensorimotor cortex (limb areas) projects to dorsal regions of the dorsolateral striatum; the visual area projects to the dorsomedial striatum; and the auditory area projects to the medial striatum. Each mesocortical area projects to a longitudinal area of the striatum: the most posteromedial mesocortex (the retrosplenial area) projects to the dorsomedial striatum; more anterior and lateral parts of the mesocortex project to more ventral parts of the striatum: and the most lateral mesocortex (the agranular insular and perirhinal areas) project to the ventrolateral striatum.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Effect of stimulation of the medial geniculate body on the motor polarization dominant in rabbits.

Studies were carried out on the effects of stimulation of the medial geniculate body on the course and recovery of a cortical motor polarization dominant created in the sensorimotor cortex of the right hemisphere in rabbits. Stimulation of the medial geniculate body, on a background of an optimum dominant, elicited a movement response of the "dominant" limb. Spectral-coherent analysis of the electrical activity of the sensorimotor cortex and medial geniculate body showed that stimulation produced changes characteristic of the dominant state in the power spectra of the total activity of these structures of the right "dominant" half of the brain, as well as in the coherence spectra.

Animals↗
PubMed1990

Cerebral capillary bed structure of normotensive and chronically hypertensive rats.

In this study cerebral capillary bed structure and the effects of chronic hypertension on these systems have been assessed in 6- to 7-month-old spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Capillary diameter (D), profile frequency (Na), volume fraction (Vv), and surface area (Sv) were quantitated by light microscopic morphometry of eight brain areas including the sensorimotor cortex and subfornical organ. Previously presented data from normotensive Sprague-Dawley rats (SpD) of similar age were also compared. Within each of the three rat strains, D, Na, Vv, and Sv varied among brain areas. For the sensorimotor cortex and subfornical organ, capillary profile frequency differed significantly among the three rat strains. In SHR and WKY, there was an inverse correlation between profile frequency and diameter, i.e., as Na increased among brain areas, D decreased. In six brain areas capillary volume fraction and surface area were identical in SHR and WKY, but were lower in SpD. Consistent differences between SHR and WKY were found only for the subfornical organ, which suggests some involvement of this structure in hypertension. Since there were few statistically significant differences between SHR and WKY and many statistically significant differences between the two normotensive strains, cerebral capillary bed structure seems to be independent of arterial blood pressure in most brain areas of these rats.

Animals↗
PubMed2005

Cortical adaptation in patients with MS: a cross-sectional functional MRI study of disease phenotypes.

BACKGROUND: Movement-associated cortical reorganisation is known to occur in multiple sclerosis (MS). We aimed to define the development of such cortical reorganisation by comparing data from patients with different disease phenotypes. METHODS: We studied patients with different phenotypes of MS: 16 patients with a clinically isolated syndrome (CIS), 14 patients with relapsing-remitting MS (RRMS) and no disability, 15 patients with RRMS and mild clinical disability, and 12 patients with secondary progressive MS (SPMS). Patients did a simple motor task with their unimpaired dominant hand during MRI, which was compared across the phenotype groups. FINDINGS: Patients with a CIS activated more of the contralateral primary sensorimotor cortex than those with RRMS and no disability, whereas patients with RRMS and no disability activated more of the supplementary motor area than those with a CIS. Patients with RRMS and no disability activated more of the primary sensorimotor cortex, bilaterally, and more of the ipsilateral supplementary motor area than patients with RRMS and mild clinical disability. Conversely, patients with RRMS and mild clinical disability activated more of the contralateral secondary somatosensory cortex and inferior frontal gyrus, and the ipsilateral precuneus. Patients with RRMS and mild clinical disability activated more of the contralateral thalamus and of the ipsilateral secondary somatosensory cortex than those with SPMS. However, patients with SPMS activated more of the inferior frontal gyrus, bilaterally, the middle frontal gyrus, bilaterally, the contralateral precuneus, and the ipsilateral cingulate motor area and inferior parietal lobule. INTERPRETATION: Movement-associated cortical reorganisation in patients with MS seems to vary across individuals at different stages of disease. Our study suggests that early in the disease course more areas typically devoted to motor tasks are recruited. Then bilateral activation of these regions is seen, and late in the disease course, areas that healthy people recruit to do novel or complex tasks are activated.

Adaptation, Physiological↗