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PubMed1992

Sex differences in the gross size of the rat neocortex.

The pervasiveness of sex differences in the size of the rat cerebral cortex was investigated in ten littermate pairs of socially housed Long-Evans hooded rats at 90 days of age. Overall, the cortex was longer and wider in male than in female rats. Sex differences were detected in most cortical regions with this sample size; the exception was the temporal cortex. While some asymmetries were found, they did not vary with the sex of the animal nor were they consistently in one direction. The contribution of the cortical layers to sex differences in cortical thickness was examined in four locations: the primary motor cortex, the forelimb area of the sensorimotor cortex and the monocular and the binocular areas of the visual cortex. The layers that showed sex differences varied among the areas but were confined to layers II-III, V and VI. Sex differences in cortical size were widespread in the adult rat but showed some regional and laminar specificity.

Animals↗
PubMed2001

Arm training induced brain plasticity in stroke studied with serial positron emission tomography.

We used serial positron emission tomography (PET) to study training-induced brain plasticity after severe hemiparetic stroke. Ten patients were randomized to either task-oriented arm training or to a control group and scanned before and after 22.6 +/- 1.6 days of treatment using passive movements as an activation paradigm. Increases of regional cerebral blood flow (rCBF) were assessed using statistical parametric mapping (SPM99). Before treatment, all stroke patients revealed bilateral activation of the inferior parietal cortex (IPC). After task-oriented arm training, activation was found bilaterally in IPC and premotor cortex, but also in the contralateral sensorimotor cortex (SMC). The control group only showed weak activation of the ipsilateral IPC. After treatment, the training group revealed relatively more activation bilaterally in IPC, premotor areas, and in the contralateral SMC. Five normal subjects showed no statistical significant differences between two separate PET studies. In this group of patients, task-oriented arm training induced functional brain reorganization in bilateral sensory and motor systems.

Aged↗
PubMed1996

Cerebral structures participating in motor preparation in humans: a positron emission tomography study.

1. Using positron emission tomography and measurement of regional cerebral blood flow (rCBF) as an index of cerebral activity we investigated the central processing of motor preparation in 13 healthy volunteers. 2. We used a motor reaction time paradigm with visual cues as preparatory and response signals. A preparatory stimulus (PS) provided either full, partial, or no information regarding two variables of a forthcoming right finger movement: finger type (index or little finger) and movement direction (abduction or elevation). After a variable delay period, a response stimulus (RS) prompted the movement. A condition was also tested in which the subject could freely select any of the four possible movements during the preparation period ("free" condition). The timing of events was designed to emphasize the motor preparation phase over the motor execution component during the scanning time of 1 min. 3. Distinct preparatory processes, which depended on the information contained in the PS, were demonstrated by significant differences in reaction time between conditions. The reaction time was shorter in the "full" and free conditions, intermediate in the two partial information conditions ("finger" and "direction"), and longer when no preparatory information was available ("none" condition). Conversely, movement time and movement amplitude were similar between conditions, establishing the constancy of the motor executive output. 4. In comparison with a "rest" condition, which had matched visual inputs, the different conditions of motor preparation were associated with increased rCBF in a common set of cerebral regions: the contralateral frontal cortex (sensorimotor, premotor, cingulate, and supplementary motor cortex), the contralateral parietal association cortex (anterior and posterior regions), the ipsilateral cerebellum, the contralateral basal ganglia, and the thalamus. This observation substantiates the participation of those cerebral structures in the preparation for movement. Furthermore, the similarity of the activated areas among the different conditions compared with the rest condition suggests a single anatomic substrate for motor preparation, independent of the movement information context. 5. Differing amounts of movement information contained in the PS affected rCBF changes in some cerebral regions. In particular, the rCBF in the anterior parietal cortex (Brodmann's area 40) was significantly larger in each of the full, finger, and direction conditions, individually, compared with the none condition. This observation supports the hypothesis that the anterior parietal association cortex plays a major role in the use of visual instructions contained in the PS for partial or complete preparation to perform a motor act. On the other hand, the posterior parietal association cortex (Brodmann's area 7) was more activated in the finger, direction, and none conditions than in the full condition. This increased activity with restricted advance information suggests that the posterior region of the parietal cortex is concerned with correct movement selection on the basis of enhanced spatial attention to the RS. 6. In contrast with the parietal cortex, the secondary motor areas (i.e, premotor cortex, cingulate cortex, and supplementary motor area) showed similar activity regardless of the degree of preparation allowed by the advance visual information. Thus the parietal cortex may play a more crucial role than the secondary motor areas in integrating visual information in preparation for movement. 7. The effect on brain activity of the internal (self-generated) versus the external (cued) mode of movement selection was assessed by comparing the free and full conditions, the preparatory component being matched in the two conditions. The anterior part of the supplementary motor area was the main area preferentially involved in the internal selection of movement, independently of motor preparation processes.

Adult↗
PubMed2002

[Statistic rCBF study of extrapyramidal disorders].

We studied regional cerebral blood flow (rCBF) in 16 patients with Parkinson's disease (PD), 2 patients with dementia with Lewy bodies (DLB), 2 patients with progressive supranuclear palsy (PSP), 2 patients with striatonigral degeneration, and 16 normal volunteers, using Three-dimensional stereotactic surface projections (3 D-SSP). Decreased rCBF in PD patients was shown in the posterior parietal and occipital cortex. Decreased rCBF in DLB was shown in the frontal, parietal and occipital cortex with relative sparing of the sensorimotor cortex. Decreased rCBF in PSP was shown in the frontal cortex. Decreased rCBF in SND was shown in the frontal cortex and cerebellum. Statistic rCBF analysis using 3 D-SSP was a useful measure for the early differential diagnosis of extrapyramidal disorders.

Aged↗
PubMed2003

Reappraisal of the motor role of basal ganglia: a functional magnetic resonance image study.

The importance of the basal ganglia in controlling motor function is well known. However, neuroimaging studies have failed to show either movement-rate dependence or different activation patterns caused by self-initiated (SI) and externally triggered (ET) movements in the basal ganglia-thalamo-motor loop. We herein report the functional magnetic resonance image (fMRI) mapping of sequential left-hand finger movements at five different rates under SI and ET conditions. Significant movement-rate dependence was found in the whole right basal ganglia-thalamo-motor loop only during the SI task. Network analysis also showed strong interactions within this loop during SI movement, whereas interactions were present only from the premotor cortex to the putamen via the sensorimotor cortex during the ET task. Furthermore, psychophysiological interaction analysis confirmed the different modulation between the two tasks in the putamen. fMRI provides evidence that the basal ganglia-thalamo-motor loop plays a key role in controlling the rate of sequential finger movements in SI movement but not in ET movement.

Adult↗
PubMed2005

Intermittent hypobaric hypoxia during development--morphological and functional changes in the neocortex.

Infant rats, together with their mother, were exposed to the simulated altitude of 7,000 m for 8 hours per day since birth to the age of 17 days. Animals were studied the 25th day, 8 days after the last exposure to hypoxia. The experimental and control animals were sacrificed the 25th day by the transaortic perfusion with 4% buffered neutral formaldehyde under ether anaesthesia. Brains were processed for classical neurohistological analysis (Nissl staining), Fluoro-Jade B and Hoechst. Cortical area in the AP plane 3 mm posterior to bregma was subjected to quantification and "laminar analysis" of the neurones count. The findings were as follows: a) The cytoarchitectonics of the brain in animals exposed to hypoxia was not severely damaged. b) The thickness of neocortex is in the experimental animals lower than that in the controls. c) The "laminar analysis" of neocortex showed a relative increase of neuronal density in layers I., II., V. and VI. of the cortex. d) The electrical stimulation of sensorimotor cortex 8 days after the end of hypoxia brought about prolongation of evoked cortical after discharges. These results demonstrate that the intermittent hypobaric hypoxia has a profound effect on morphological maturation of the central nervous system in infant rats. Hypoxia influenced the excitation-- inhibition mechanisms of cortical neurones.

Animals↗
PubMed2004

Electromagnetic function of polymicrogyric cortex in congenital bilateral perisylvian syndrome.

BACKGROUND: Congenital bilateral perisylvian syndrome (CBPS) is characterised by bilateral perisylvian polymicrogyria and suprabulbar paresis. Mild tetraparesis, cognitive impairment, and epilepsy are frequently associated. Sensory deficits are surprisingly rare, even though polymicrogyria often extends to auditory and sensorimotor cortex. OBJECTIVES: To study the sensorimotor and auditory cortex function and location in CBPS patients. METHODS: We mapped the sensory and motor cortex function onto brain magnetic resonance images in six CBPS patients and seven control subjects using sources of somatosensory and auditory evoked magnetic fields, and of rhythmic magnetoencephalographic (MEG) activity phase-locked to surface electromyogram (EMG) during voluntary hand muscle contraction. RESULTS: MEG-EMG coherence in CBPS patients varied from normal (if normal central sulcus anatomy) to absent, and could occur at abnormally low frequency. Coherent MEG activity was generated at the central sulcus or in the polymicrogyric frontoparietal cortex. Somatosensory and auditory evoked responses were preserved and also originated within the polymicrogyric cortex, but the locations of some source components could be grossly shifted. CONCLUSION: Plastic changes of sensory and motor cortex location suggest disturbed cortex organisation in CBPS patients. Because the polymicrogyric cortex of CBPS patients may embed normal functions in unexpected locations, functional mapping should be considered before brain surgery.

Adolescent↗
PubMed2003

Should the injured and intact hemispheres be treated differently during the early phases of physical restorative therapy in experimental stroke or parkinsonism?

Over a century ago the intact cortex was proposed to contribute to recovery from unilateral brain injury, but its possible role in functional outcome has become more appreciated in recent years as a result of anatomic, metabolic and behavioral studies. Although use of the contralesional limb is naturally impaired after sensorimotor cortex injury, neural and astrocytic events in the intact hemisphere may give rise to, and may be influenced by, an enhanced ability to compensate for lost motor function. The debate is still open as to whether the neural changes are generally compensatory in nature, with activity in the homotopic cortex leading to greater capability in the nonimpaired limb, or whether they are actually a matter of reorganization in the homotopic cortex leading to connections to denervated targets in the opposite hemisphere, thus allowing the homotopic cortex to control motor programs there. Although both phenomena may occur to some degree, there is mounting evidence in support of the former view. Careful behavioral techniques have been developed that can expose compensatory tricks, and the time course of these behaviors correlates well with anatomic data. Moreover, if the intact cortex sustains a second lesion after recovery from the first, forelimb sensorimotor function specific to the first-impaired side of the body is not worsened. Partial denervation of callosal fibers coming from the injured hemisphere, plus preferential use of the good forelimb caused by a cortical injury, may increase trophic factors in the intact hemisphere. These and related events seem to provide a growth-favorable environment there that permits motor learning in the intact forelimb at a level of skill exceeding that which a normal animal can attain in the same period of time. There are anecdotal cases in human neurologic patients that are consistent with these findings. For example, a colleague of the authors who sustained a unilateral infarction that rendered his dominant right hand severely impaired noticed that soon after the stroke he was able to use his left hand for writing and computers as well as he had ever used his right hand. Cross-midline placing tests also indicate that the structural events observed in the intact cortex may potentiate projections to the damaged hemisphere. These changes may help restore the capacity of tactile information projecting to the intact hemisphere to control limb placing in the impaired forelimb. Neural events in the injured hemisphere can be affected by behavior differently than the neural events in the intact hemisphere. Different therapeutic strategies might well be used on opposing limbs at different times after unilateral sensorimotor cortex injury to optimize recovery (and, indeed, to avoid exaggerating the insult). Finally, the details of reorganization in both hemispheres differ greatly depending on the type of brain injury sustained (eg, in stroke versus Parkinson's disease), suggesting that an approach that considers the role of both hemispheres is likely to be beneficial in research on a broad variety of brain pathologies.

Animals↗
PubMed1984

[Effect of tropane on the cholinoreceptors of the cerebral cortex].

Spontaneous electric activity of single neurons of the sensorimotor cortex was recorded extracellularly in experiments on unanesthetized rabbits. During microiontophoretic application of tropane and acetylcholine to the neurons, the response to both the agents was the same. The cells excitable by acetylcholine are also excitable by tropane, while those inhibited by acetylcholine are also inhibited by tropane. The cells that do not respond to acetylcholine are also irresponsive to tropane. The excitatory response pattern to tropane is similar to that of acetylcholine. Under the same conditions of microiontophoretic application, tropane causes less excitation as compared with acetylcholine. Tropane preliminarily applied to the neuron reduces the excitatory effect of acetylcholine. The possible role of agonist-antagonist relations between tropane and acetylcholine in the mechanism of the pharmacological effects of tropane and its derivatives is discussed.

Acetylcholine↗
PubMedDate not supplied

[Effect of amygdalectomy on evoked potentials of the cat sensomotor cortex].

It has been shown that EPs in the sensorimotor cortex of amygdalectomized cats appear in response to almost all burst of tone frequencies ranging from 0.2 to 10.0 khz. No EPs with maximal amplitudes and maximal response probability (observed in intact animals), have been recorded in response to frequencies of 0.8, 1.6 and 2.0 to 3.0 khz. The curves of dependency of EPs amplitude and appearance probability on the tone frequency had not a single statistically significant maximum. Partial ablation of the amygdala complex impairs frequency selectivity of sensosimotor cortical EPs revealed in intact animals. The obtained data suggest that the amygdala complex is an essential element of the system detecting biologically meaningful parameters of the acoustic signal.

Amygdala↗
PubMedDate not supplied

Structure of the human sensorimotor system. I: Morphology and cytoarchitecture of the central sulcus.

We have studied the morphology of the central sulcus and the cytoarchitecture of the primary sensorimotor cortex in 20 human brains obtained at autopsy. Although the surface appearance of the central sulcus varies greatly from brain to brain (and between hemispheres of individual brains), its deep structure is remarkably consistent. The fundus of the central sulcus is divided into medial and lateral limbs by a complex junction midway between the sagittal and Sylvian fissures. Based on functional imaging studies, this junction appears to be a structural hallmark of the sensorimotor representation of the distal upper extremity. We also identified and measured area 4 (primary motor cortex) and area 3 (primary somatic sensory cortex) in Nissl-stained sections cut orthogonal to the course of the central sulcus. Although the positions of the cytoarchitectonic boundaries in the paracentral lobule showed considerable interindividual variation, the locations of the borders of areas 4 and 3 along the course of the sulcus were similar among the 40 hemispheres examined. In addition to describing more thoroughly this portion of the human cerebral cortex, these observations provide a basis for evaluating lateral symmetry of the human primary sensorimotor cortex.

Cerebral Cortex↗
PubMed2003

Correlation of functional MR imaging activation data with simple reaction times.

PURPOSE: To determine the relationship between subject reaction times (RTs) and activation volume in the brain during visuomotor functional magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-four subjects performed a simple RT task during single-event functional MR imaging, and RTs were recorded. The six subjects with the fastest RTs were designated the fast RT group, and the six subjects with the slowest RTs were designated the slow RT group. The data were processed with noncorrected height threshold (P <.001) for individual comparisons and corrected height threshold (P <.05) for group comparisons (t tests). The activation volumes in both occipital lobes, the left sensorimotor cortex, and the supplemental motor cortices were compared for the two groups. RESULTS: The mean RT +/- SD was 342 msec +/- 20.15 for the fast RT group and 475 msec +/- 36.17 for the slow RT group (P <.0001). More voxels of activation were seen in the fast RT group than in the slow RT group in the occipital lobes, left sensorimotor cortices, and supplemental motor cortices on individual and group maps. This difference was statistically significant in the left sensorimotor (P =.03) and left visual (P =.05) cortices. In the right visual cortex, a trend toward more activation in the fast RT group was noted (P =.15). There was a negative correlation between RTs and activation volume in the left sensorimotor cortex (P =.048). CONCLUSION: There was a greater activation volume in motor and visual cortices in the fast RT group than in the slow RT group.

Adult↗
PubMed1990

Electroencephalographic and magnetoencephalographic studies of motor function.

Although a great deal has been learned from the study of scalp-recorded movement-related potentials, the exact origin of the various components described above remains unclear, mainly because of the limited spatial resolution of the EEG and the consequent difficulty in predicting sources from the surface distribution of these components. The introduction of the MEG and source localization methods based on neuromagnetic recordings has provided a new means by which to study the cortical activation during movement in humans. The study of movement-related magnetic fields of the brain is still at an early stage of development. However, the data reviewed to date indicate that the MEG offers a promising means by which to study (noninvasively) cortical motor function. With regard to the data reviewed here, the following conclusions can be made: 1. Slow "readiness" magnetic fields can be recorded prior to a variety of voluntary movements and display a topography which indicates the activation of bilateral sources, even if the instructed movement is unilateral. Sources in the contralateral hemisphere appear as early as 0.5 sec before the movement and appear to be localized in the sensorimotor cortex. Consequently, the assumption of a contralateral source being the only or primary generator of the readiness potential, based on EEG data, must be tempered. 2. A large-amplitude "movement-evoked field" (occurring at a post-EMG-onset latency of about 110 msec for finger movements) is probably the counterpart of the MP and appears to be the result of a dipolar source localized to the contralateral sensorimotor area. This source is probably the first sign of movement reafferent input to cortex. 3. Variability in the movement-evoked field across individuals, which are much more evident in MEG than in EEG, may reflect the summation of multiple sources active in the region of the sensorimotor cortex during movement onset (i.e., both pre- and postcentral generators). In some instances, it may be possible to extract simpler elements of these complex sources based on assumptions of temporal overlapping of pre-movement and movement-evoked activity.

Brain Mapping↗
PubMed1998

Somatic and limbic cortex activation in esophageal distention: a functional magnetic resonance imaging study.

Little is known about the cerebral representations of visceral sensations in humans. Using functional magnetic resonance imaging (fMRI), we mapped the cortical areas of the human brain that were activated by mechanical stimulation of the esophagus in 5 healthy volunteers. Stimulation probes were placed into the distal part of the esophagus and inflated to produce a local distention. The cerebral activation pattern was related to the strength and quality of the stimulus. The weakest stimulus accompanied by a well-localized albeit weak retrosternal sensation activated only the parietal opercular cortices, probably including the secondary somatosensory cortex (SII). Additional activation of the primary sensorimotor cortex (SI) at the level of the face and mouth representation as well as of the right premotor cortex was found during repetitive distention of the esophagus at 0.5 Hz. Repetitive stimulation at 1 Hz additionally activated the insula bilaterally. The strongest distention stimulus, which caused a painful retrosternal sensation, resulted in an activation of the anterior cingulate cortex. Our findings demonstrate that SII is the primary cortical target of visceral afferents originating in the esophagus. Limbic structures become engaged when the visceral sensation is unpleasant or painful.

Adult↗
PubMed2004

Timing functions of the supplementary motor area: an event-related fMRI study.

Two previous studies in which we recorded slow brain potential shifts over the scalp revealed performance-dependent effects that sustained one prominent model of timing mechanisms. These effects seemed to be derived from the supplementary motor area (SMA). Event-related functional magnetic resonance imagery (fMRI) was used to check this hypothesis. Brain activations were contrasted in Time production and (control) Force production tasks involving left-hand responding. These tasks, presented in mixed order, were designed to be of equivalent difficulty and involve comparable levels of attention. Several brain areas were activated in both tasks relative to baseline: the SMA, the putamen, and the lateral cerebellum. Contrasts between tasks gave clear-cut differences. Activations specific to the Time task were found in the SMA proper and the left primary motor cortex. The Force task activated the right sensorimotor cortex and the left cerebellum, and, bilaterally, the infero-parietal cortex and the insula. The main result, i.e. prominent activation of the SMA proper in relation to temporal production, corroborates our previous studies based on slow cortical potentials. The data are referred to current evidence suggesting that timing processes are subtended by a striato-thalamo-cortical pathway including the SMA.

Adult↗
PubMed2004

The role of the electrophysiological properties of neurons in the mechanisms grouping their discharges in the cerebral cortex.

Studies using intracellular recording in living slices of rat sensorimotor cortex addressed the interaction between the properties of neuron spike activity (n = 80) and the membrane potentials of the neurons. Spike sequences containing discharges with regularly increasing and decreasing interspike intervals were analyzed. Parameters were identified which were closely associated with the mean neuron discharge frequency: the number of spikes in sequences (5-30% of the total number of spikes recorded), the amplitude of oscillations in the afterhyperpolarization potential (0-1.5 mV), etc. There was a biphasic relationship in changes in the number of spikes in sequences with a critical mean discharge frequency over the range 5-7 Hz. Groups of cells without and with a depolarization component in conditions of afterhyperpolarization had different morphological and electrophysiological properties, though the relationships between their parameter and mean discharge frequency were similar. The possible roles of spike sequences and these regular features in the formation of rhythmic processes in the neocortex are discussed.

Action Potentials↗
PubMed1989

Transvenous perfusion of the brain with verapamil during focal cerebral ischemia in rats.

We report on the effect of calcium channel blocker verapamil administered into the inferior cerebral vein in rats 1 hour after occlusion of the middle cerebral artery. Twenty-four rats were divided into four groups of six rats each. Group A rats received no medication. The other three groups received 0.1 mg verapamil/kg/2 hr. Group B rats received verapamil intravenously. Group C and D rats received verapamil and autologous arterial blood by transvenous perfusion of the brain, Group C rats at 100 mm Hg perfusion pressure and Group D rats at 150 mm Hg perfusion pressure. The administration of verapamil started 1 hour after middle cerebral artery occlusion and lasted for 2 hours. Three hours after occlusion, we used double- or single-tracer autoradiography with 4-[18F]fluoroantipyrine or [14C]iodoantipyrine and [14C]alpha-aminoisobutyric acid as tracers to study the brains for local cerebral blood flow and blood-brain barrier permeability changes. Group C showed a significant increase of local cerebral blood flow in the parietal cortex (89%, p less than 0.01) and sensorimotor cortex (64%, p less than 0.05) compared with Group A. Group D showed an extensive and striking increase in local cerebral blood flow of the ischemic cortical and subcortical areas (57-100%, p less than 0.05). Group B showed no significant changes but exhibited further reduction of local cerebral blood flow in the ischemic cerebral hemisphere associated with slightly increased local cerebral blood flow in the nonischemic cerebral hemisphere compared with Group A. There was no change of blood-brain barrier permeability in any group.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMedDate not supplied

[Effect of stimulation of rostral portions of the midbrain reticular formation on the cat motor cortex].

Evoked potentials and responses of 139 neurones in the sensorimotor cortex (the lateral third of the posterior sigmoid gyrus) to electrical stimulation of the dorsolateral (DL) and the ventromedial (VM) areas of the mesencephalic reticular formation (MRF) were investigated in cats in acute and chronic experiments. Latencies of the cortical unit responses (in the form of single and multiple discharges) to MRF stimulation varied from 4 to 36 msec for VM (maxima of distribution: 4--10 and 18--24 msec); those for DL were from 4 to 26 msec (maxima of distribution: 4--6 and 14--16 msec). Responses to both DL and VM stimulation were observed in 29 neurones. As for MRF, its effects (mono-and polyvalent) were found in cortical neurones responding to limb electrocutaneous stimulation as well. At 7--10 days after coagulation of the ipsilateral connection between MRF and the pons, persistence of the cortical response main components was recorded, the long-latency part being slightly reduced.

Animals↗