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PubMed1995

Zonisamide: electrophysiological and metabolic changes in kainic acid-induced limbic seizures in rats.

We studied the pharmacological mechanism of zonisamide (ZNS) using an electrophysiological and autoradiographical method in a limbic seizure model in rats. Limbic seizure status epilepticus was induced by a unilateral microinjection of kainic acid (KA) into the amygdala. Initially, observed seizures were limited to the side of the injected amygdala and then propagated to bilateral sensorimotor cortex. Eighty minutes after injection, secondarily generalized seizure status epilepticus was induced, with each seizure lasting approximately 30 s and recurring every 5 min. ZNS 100 mg/kg was administered intravenously (i.v.) during the generalized seizure. Forty minutes after ZNS administration, epileptic activity was observed only at the KA-injected amygdalar site and spikes were not observed in the bilateral sensorimotor cortex. We studied local cerebral glucose utilization (LCGU) after ZNS or saline administration using an autoradiographical method in the same limbic seizure preparation. In the ZNS group, LCGU decreased in the ipsilateral sensorimotor cortex and hippocampus, whereas in the controls LCGU increased in these structures. On the other hand, ZNS did not suppress the epileptic activity of the primary focus and no decrease in LCGU was observed in the KA-injected amygdala. ZNS inhibited seizure propagation from the epileptogenic focus but did not suppress the epileptic activity of the focus. Our results suggest that ZNS is effective for the treatment of secondarily generalized seizure.

Animals↗

PubMed2003

Dynamic synchronisation of central oscillators in essential tremor.

OBJECTIVE: Coherence analysis of electromyography (EMG) signals in essential tremor (ET) suggests that tremor in the right and left arm is induced by independent central oscillators. The sensorimotor cortex seems to be part of the tremor-generating neuronal network in ET. Here, we investigated using electroencephalography (EEG) whether the independence of central oscillators in ET is supported by the analysis of cortical activity. METHODS: In 8 patients with ET, bilateral hand tremor was activated by wrist extension. EMGs from the wrist flexors and extensors were recorded simultaneously with an EEG. EEG-EMG coherence was estimated for 74 epochs of 60 s duration. RESULTS: In 42.6% of the cases, EEG-EMG coherence at the tremor frequency existed only with the contralateral sensorimotor cortex. However, 21.6% of the tremor-EMGs were coherent with EEG activity over both the contralateral and ipsilateral sensorimotor cortex. Bilateral and exclusively contralateral EEG-EMG coherence could alternate within the same recording. Bilateral EEG-EMG coherence was associated with increased right-left EEG-EEG coherence, increased right-left EMG-EMG coherence as well as with increased tremor strength. CONCLUSIONS: In ET, central oscillators in the right and left brain are not entirely independent of each other. They may dynamically synchronise, presumably by interhemispheric coupling via the corpus callosum.

Adult↗

PubMed1996

Fetal neocortical tissue blocks implanted in brain infarcts of adult rats interconnect with the host brain.

The purpose of the present study was to study if the connectivity of fetal neocortical tissue blocks placed in ischemic brain infarcts of adult rats would be enhanced in rats housed in an enriched environment. We also investigated whether the enriched housing conditions could enhance the postischemic and postgrafting functional outcome, in terms of motor behavior. This part of the study has been published recently. The middle cerebral artery was ligated on the right side in 37 inbred, adult male spontaneously hypertensive rats. The rats were placed at random either in an enriched environment (groups A and B) or in standard laboratory cages (group C). Three weeks after the artery occlusion, blocks of fetal sensorimotor cortex (embryonic day 17) were transplanted into the infarct cavity of rats from groups B and C. After 9 weeks all transplanted rats received an injection, into the graft, of a mixture containing the two tracers Fluoro-Gold and biotinylated Dextran amine. The transplants revealed a structured morphology with whorls and bands of cells reminiscent of normal neocortex. Tracing of efferent transplant to host fibers with biotinylated Dextran amine showed pronounced intrinsic transplant projections, as well as fibers, although significantly fewer, to the host ipsilateral sensorimotor cortex, striatum, and thalamus. Host to transplant projections were revealed by Fluoro-Gold-labeled cells found in the ipsilateral host sensorimotor cortex, the basal nucleus of Meynert, the thalamic ventrobasal, ventrolateral and posterior nuclei, and in the dorsal raphe nuclei. We conclude that fetal frontal neocortical block grafts placed in brain infarcts of adult rats develop a morphology reminiscent of normal neocortex and that both afferent and efferent neural connections, although sparse, are established with the host brain, whether the rats are reared under enriched housing conditions or not.

Animals↗

PubMed1987

Somatosensorimotor function of the superior colliculus, somatosensory cortex, and lateral hypothalamus in the rat.

The role of the superior colliculus in multimodal sensory function is unsettled, in large part because a clear distinction between the somatosensory effects and the postural/motor effects of damage to the deep layers of the superior colliculus has not been obtained. Unilateral lesions of the entire superior colliculus impair orienting of the head and eyes to tactile, visual, and auditory stimuli presented on the side of the body contralateral to the lesion; however, even in the absence of sensory stimulation animals with such a lesion tend to circle ipsiversively and fail to make contralateral head movements. To determine whether or not unilateral damage to the superior colliculus produces a somatosensory asymmetry independently of head movement/circling biases, a neurological test was used in which lateral head or trunk movements were not required. Small pieces of adhesive-backed paper were attached to each forelimb and the latencies to contact and remove the stimuli were recorded. A battery of standard neurological tests was administered as well. The entire superior colliculus was removed unilaterally, and for comparison, the sensorimotor cortex or lateral hypothalamus were damaged in additional groups. Lesions of the superior colliculus produced the expected deficit in contralateral orienting and ipsilateral circling/postural biases, but failed to produce a somatosensory asymmetry in the head movement-independent sensorimotor test. In contrast, both sensorimotor cortex and lateral hypothalamus lesions produced a severe asymmetry in the head-movement-independent sensorimotor test. We conclude that the superior colliculus is involved in the control of lateral head movements and that its role in somatosensory function is fundamentally different from that of the sensorimotor cortex or lateral hypothalamus regions.

Animals↗

PubMed1980

Effect of stimulation on the incorporation of 14C from glial and neuronal specific substrates into brain proteins in vivo and in vitro.

The incorporation of amino acids into brain proteins following brachial plexus stimulation (BPS) was studied in anaesthetised Sprague-Dawley rats following injection of radioactive precursors of both neuronal and glial compartments. Following intraperitoneal injection of [14C]glucose, which is the major neuronal pool precursor, BPS resulted in a significant increase of 37% (P < 0.001) in the incorporation of carbon from [14C]glucose into TCA-insoluble proteins in the contralateral sensorimotor cortex as compared with the ipsilateral area of the same animal. This increase was abolished totally when tetrodotoxin (10 micrograms ml-1) was applied topically to the surface of the stimulated area. Following intraperitoneal injection of [14C]acetate, which is considered to by mainly a glial cell precursor, the same afferent electrical stimuli caused a significant decrease of 21% in the incorporation of amino acids into proteins in the stimulated versus unstimulated sensorimotor cortex. With [4-(3)H]phenylalanine or [1-(14)C]leucine as precursors a significant decrease (12%) or no change was recorded, respectively. A similar decrease in protein synthesis in the stimulated sensorimotor cortex was achieved using different routes of injection. No significant changes were observed in the ratio of the specific radioactivities of the total amino acids of the two hemispheres using either precursor. In vitro, synaptosomes showed a large increase in incorporation into proteins after treatment with electrical pulses, both with [14C]glucose and with [U-14C]acetate as precursors.

Acetates↗

PubMed2001

Regional accumulation of 14C-zonisamide in rat brain during kainic acid-induced limbic seizures.

BACKGROUND: Zonisamide (ZNS) is an antiepileptic drug developed in Japan. Various experimental studies have investigated the effects of ZNS. However, the mechanism of action of ZNS against limbic seizures and secondary generalization is not well-known. We studied ictal regional accumulation of ZNS in the rat brain during kainic acid (KA)-induced limbic status epilepticus. METHODS: Fourteen male Wistar rats underwent a stereotactic operation. For recording the electroencephalogram (EEG), electrodes were placed in the left amygdala (LA), left dorsal hippocampus, and over the left sensorimotor cortex. For microinjection, a stainless steel cannula was also inserted into the LA. Seven days after surgery, rats were anesthetized and a catheter was inserted into the femoral vein. The animals were immobilized and allowed to recover from anesthesia for at least two hours. In eight rats, 1.0 microL (1.0 microg) of KA was injected into the LA, and 1.0 microL of phosphate buffer solution was injected into the LA in six control rats. Sixty minutes after injection, 14C-ZNS was administered intravenously, and an autoradiographic study was done. RESULTS: During limbic status epilepticus, only seizures in the sensorimotor cortex were markedly attenuated a few minutes after 14C-ZNS administration. Additionally, high uptake of 14C-ZNS was noted ipsilaterally in the sensorimotor cortex, parietal cortex and thalamus (lateral portion). In control rats, no EEG change was seen, and distribution of 14C-ZNS was rather homogeneous. CONCLUSIONS: These results suggested that ZNS suppresses secondary generalization of limbic seizures by a direct effect on the cerebral cortex.

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PubMed1987

[Role of cortical inhibition in heterosensory interaction of neurons of the sensomotor cortex of the cat].

Background and evoked neuronal activity of the sensorimotor cortex was studied in cats under chloralose anaesthesia. Click, flashes and shocks applied to the contralateral forepaw were used as stimuli. Paired heteromodal stimuli were presented with interstimulus intervals of 0, 100, 200, 300 and 400 ms. Stimuli of different modality completely or partly blocked the response to the testing stimulus when the interstimulus interval was 100-200 ms. The maximum response to the second stimulus followed 200-300 ms after the first stimulus. To study the intercortical mechanisms of heterosensory interaction picrotoxin (antagonist of inhibitory neurotransmitter) was locally applied to the studied neuron. Picrotoxin application produced reduction of the blocking period after the conditioning stimulus and appearance of a response to the testing stimulus at shorter interstimulus intervals compared with those observed before application. In some cells an increase in the number of spikes in a burst at one interstimulus interval or an even rise in the response at several interstimulus intervals were observed. The question about the role of intracortical inhibitory influences on the mechanisms of heterosensory interaction on neurons of the sensorimotor cortex is discussed on the basis of the obtained data.

Animals↗

PubMed2006

Three-dimensional locations and boundaries of motor and premotor cortices as defined by functional brain imaging: a meta-analysis.

The mesial premotor cortex (pre-supplementary motor area and supplementary motor area proper), lateral premotor cortex (dorsal premotor cortex and ventral premotor cortex), and primary sensorimotor cortex (primary motor cortex and primary somatosensory cortex) have been identified as key cortical areas for sensorimotor function. However, the three-dimensional (3-D) anatomic boundaries between these regions remain unclear. In order to clarify the locations and boundaries for these six sensorimotor regions, we surveyed 126 articles describing pre-supplementary motor area, supplementary motor area proper, dorsal premotor cortex, ventral premotor cortex, primary motor cortex, and primary somatosensory cortex. Using strict inclusion criteria, we recorded the reported normalized stereotaxic coordinates (Talairach and Tournoux or MNI) from each experiment. We then computed the probability distributions describing the likelihood of activation, and characterized the shape, extent, and area of each sensorimotor region in 3-D. Additionally, we evaluated the nature of the overlap between the six sensorimotor regions. Using the findings from this meta-analysis, along with suggestions and guidelines of previous researchers, we developed the Human Motor Area Template (HMAT) that can be used for ROI analysis. HMAT is available through e-mail from the corresponding author.

Algorithms↗

PubMed2000

Articulatory/phonetic sequencing at the level of the anterior perisylvian cortex: a functional magnetic resonance imaging (fMRI) study.

Damage to the anterior peri-intrasylvian cortex of the dominant hemisphere may give rise to a fairly consistent syndrome of articulatory deficits in the absence of relevant paresis of orofacial or laryngeal muscles (apraxia of speech, aphemia, or phonetic disintegration). The available clinical data are ambiguous with respect to the relevant lesion site, indicating either dysfunction of the premotor aspect of the lower precentral gyrus or the anterior insula in the depth of the Sylvian fissure. In order to further specify the functional anatomic substratum of this syndrome, functional magnetic resonance imaging (fMRI) was performed during reiteration of syllables differing in their demands on articulatory/phonetic sequencing (CV versus CCCV versus CVCVCV). Horizontal tongue movements and a polysyllabic lexical item served as control conditions. Repetition of the CV and CCCV monosyllables elicited a rather bilateral symmetric hemodynamic response at the level of the anterior and posterior bank of the central sulcus (primary sensorimotor cortex), whereas a more limited area of neural activity arose within this domain during production of lexical and nonlexical polysyllables, significantly or exclusively lateralized toward the left hemisphere. There is neurophysiological evidence that primary sensorimotor cortex mediates the "fractionation" of movements. Assuming that the polysyllables considered are organized as coarticulated higher-order units, the observed restricted and lateralized cortical activation pattern, most presumably, reflects a mode of "nonindividualized" motor control posing fewer demands on "movement fractionation." These findings may explain the clinical observation of disproportionately worse repetition of trisyllabic items as compared to monosyllables in apraxia of speech. The various test materials failed to elicit significant activation of the anterior insula. If at all, only horizontal tongue movements yielded a hemodynamic reaction extending beyond the sensorimotor cortex to premotor areas. Since limbic projections target the inferior dorsolateral frontal lobe, the enlarged region of activation during horizontal tongue movements might reflect increased attentional requirements of this task.

Adult↗

PubMed1991

Lesion-induced establishment of the crossed corticorubral projections in kittens is associated with axonal proliferation and topographic refinement.

The aberrant crossed corticorubral projection of the cat, which is very weak compared to the uncrossed one at about 1 month postnatal, becomes pronounced following unilateral lesions of the sensorimotor cortex. In order to determine whether or not terminal proliferation of pre-existing axons underlie this enlargement, the morphological changes of the crossed axons were examined, using the anterograde tracer Phaseolus vulgar- is leukoagglutinin (PHA-L). The crossed corticorubral axons in normal kittens were mostly simple in morphology with infrequent branching and did not often exhibit growth-cone-like axonal endings at 1 month postnatal. Two to 5 days after unilateral lesions of the sensorimotor cortex placed at this age, the axons were as simple as those in normal animals but ended in growth cones more frequently. Seven to 10 days post-lesion, the axons often bore side-branches which ended in growth cones. Two to 3 weeks post-lesion axons with sprays of finger-like fine sprouts occurred throughout the projection zone. There was no clear topography for the crossed projection in normal animals, but at 1-2 weeks post-lesion the axons started to show a certain amount of localization in the regions of the red nucleus which corresponded to the densely innervated region on the ipsilateral side. The topography of the crossed projections roughly mirrors that of the ipsilateral projection at about 1 month post-lesion. Thus, the lesions of the sensorimotor cortex induce substantial growth and proliferation of the crossed corticorubral axons. The post-lesion changes in axonal morphology and topographic refinement are reminiscent of developmental events. It is likely that the lesions permit the crossed axons, which normally fail to develop, to develop like the uncrossed ones.

Aging↗

PubMed1998

Functional MR imaging of cortical activation of the cerebral hemispheres during motor tasks.

PURPOSE: We used functional MR imaging to evaluate cortical activation in the precentral, central, and postcentral regions of the contralateral and ipsilateral cerebral hemispheres during left- and right-handed motor tasks. METHODS: Ten healthy right-handed volunteers were studied with echo-planner MR imaging (1.5 T) while performing alternating finger apposition tasks with both hands. During the hand tasks, the areas of activated pixels were compared between subregions (precentral, central, and postcentral) of the contralateral and ipsilateral sensorimotor cortex. RESULTS: The activated area of the contralateral sensorimotor cortex was significantly larger than that of the ipsilateral cortex during tasks with either hand, whereas the ipsilateral activated area was significantly larger during the left-handed task than during the right-handed task. Ipsilateral activation was greatest in the precentral region, less in the central region, and least prominent in the postcentral region. CONCLUSIONS: Our results confirmed those of previous investigators that ipsilateral activation is more pronounced during left-sided movements than during right-sided movements. The variation in activation of the precentral, central, and postcentral subregions suggests different roles of the ipsilateral and contralateral hemispheres during motor tasks.

Adult↗

PubMed2003

Nonlesional central lobule seizures: use of awake cortical mapping and subdural grid monitoring for resection of seizure focus.

OBJECT: Surgical treatment options for intractable seizures caused by a nonlesional epileptogenic focus located in the central sulcus region are limited. The authors describe an alternative surgical approach for treating medically refractory nonlesional perirolandic epilepsy. METHODS: Five consecutive patients who were treated between 1996 and 2000 for nonlesional partial epilepsy that had originated in the central lobule were studied. The patients' ages ranged from 16 to 56 years (mean 28.6 years; there were four men and one woman). The duration of their epilepsy ranged from 8 to 39 years (mean 20.2 years), with a mean seizure frequency of 19 partial seizures per week. Preoperative assessment included video electroencephalography (EEG) and subtracted ictal-interictal single-photon emission computerized tomography coregistered with magnetic resonance imaging (SISCOM). Patients underwent an awake craniotomy stereotactically guided by the ictal EEG and SISCOM studies. Cortical stimulation was used to identify the sensorimotor cortex and to reproduce the patient's aura. A subdural grid was then implanted based on these results. Subsequent postoperative ictal electrocorticographic recordings and cortical stimulation further delineated the site of seizure onset and functional anatomy. During a second awake craniotomy, a limited resection of the epileptogenic central lobule region was performed while function was continuously monitored intraoperatively. One resection was limited to the precentral gyrus, two to the postcentral gyrus, and in two the excisions involved regions of both the pre- and postcentral gyri. In three patients a hemiparesis occurred postsurgery but later resolved. In the four patients whose resection involved the postcentral gyms, transient cortical sensory loss and apraxia occurred, which completely resolved in three. Two patients are completely seizure free, two have experienced occasional nondisabling seizures, and one patient has benefited from a more than 75% reduction in seizure frequency. The follow-up period ranged from 2 to 5.5 years (mean 3.5 years). CONCLUSIONS: A limited resection of the sensorimotor cortex may be performed with acceptable neurological morbidity in patients with medically refractory perirolandic epilepsy. This procedure is an alternative to multiple subpial transections in the surgical management of intractable nonlesional epilepsy originating from the sensorimotor cortex.

Adolescent↗

PubMed2005

Functional magnetic resonance imaging in anesthetized patients: a relevant step toward real-time intraoperative functional neuroimaging.

OBJECTIVE: The introduction of intraoperative 1.5-T magnetic resonance imaging may provide up-to-date functional information in the surgical environment. However, feasible passive paradigms that allow the examination of anesthetized patients will be a precondition for intraoperative functional magnetic resonance imaging (fMRI). The aim of this study is to evaluate the feasibility of a recently developed passive fMRI paradigm for functional neuroimaging in anesthetized patients. METHODS: We investigated four anesthetized patients with intracranial pathological conditions not related to the sensorimotor cortex. All patients had been anesthetized with standard total intravenous anesthesia for more than 24 hours before the fMRI scan. Anesthesia and monitoring were sustained during the scanning procedure. A simultaneous electrical stimulation of the median and tibial nerves was applied to elicit a cortical activation using a custom-designed magnetoelectrically shielded conductor. Statistical evaluation using Statistical Parametric Mapping software (Wellcome Department of Imaging Neuroscience, University College, London, England) and the Talairach Daemon Client (Version 1.1; Research Imaging Center, University of Texas Health Science Center, San Antonio, TX) followed. RESULTS: Three of four patients showed a good activation of the sensorimotor cortex under anesthesia. In one patient, no significant activation was observed, presumably as a result of increased body impedance because of severe edema. Standard dosages of the narcotics did not influence the cortical response; however, stimulation intensity had to be increased compared with awake patients. We did not detect relevant interferences with magnetic resonance imaging arising from the technical setup. CONCLUSION: The method presented proved to be a feasible paradigm for fMRI evaluation of the sensorimotor cortex in anesthetized patients and thus forms a relevant step toward real intraoperative functional neuroimaging.

Aged↗

PubMed2001

Tremor-correlated cortical activity in essential tremor.

BACKGROUND: In patients with parkinsonian resting tremor, tremor-correlated activity in the contralateral sensorimotor cortex has been studied by both magnetoencephalography (MEG) and electroencephalography (EEG). In essential tremor, MEG failed to detect cortical involvement. The objective of this study was to investigate whether EEG recording can reveal tremor-correlated cortical activity in patients with essential tremor or enhanced physiological tremor. METHODS: Seven patients with essential tremor and three patients with enhanced physiological tremor participated in the study. Unilateral postural tremor was activated by wrist extension on the right or on the left side. Electromyography (EMG) signals arising from the wrist extensor and flexor muscles, and a high-resolution EEG were recorded simultaneously. Coherences between the time series of the rectified tremor EMG and the EEG were estimated. FINDINGS: In five of nine arms with essential tremor, we found highly significant coherences at the tremor frequency between the tremor EMG and the EEG. Isocoherence maps illustrating the topography of significant coherences over the scalp showed that the maximum coherences were located over the contralateral sensorimotor cortex. In the patients with enhanced physiological tremor, we were unable to detect consistent significant corticomuscular coherences at the tremor frequency. INTERPRETATION: Using simultaneous EEG-EMG recordings, we showed that significant corticomuscular coherences at the tremor frequency can be found in essential tremor. This finding contrasts with a recent study based on MEG recordings. The results suggest that the sensorimotor cortex is involved in the generation of essential tremor, in a similar way to that previously shown in parkinsonian resting tremor.

Adult↗

PubMed2004

A functional MRI study of movement-associated cortical changes in patients with Devic's neuromyelitis optica.

Movement-associated cortical changes have been shown in several neurological conditions and were found to be associated to the extent of brain and cord damage. Devic's neuromyelitis optica (DNO) is characterized by a severe involvement of the cord and optic nerve, with sparing of the brain. To assess the actual role of cord pathology on the pattern of movement-associated cortical recruitment, we obtained functional magnetic resonance imaging (fMRI) from patients with DNO and investigated whether the extent of brain activation is correlated with the extent of cervical cord damage. We studied 10 right-handed DNO patients and 15 sex- and age-matched healthy controls. The MRI assessment consisted of the following: (a) fMRI during repetitive flexion extension of the last four fingers of the right and left hand, (b) brain and cervical cord conventional MRI, and (c) cervical cord magnetization transfer (MT) MRI. Compared to controls and for both tasks, DNO patients had an increased recruitment of several regions of the sensorimotor network (primary sensorimotor cortex, postcentral gyrus, middle frontal gyrus, rolandic operculum, secondary sensorimotor cortex, precuneus, and cerebellum) and of several other regions mainly in the temporal and occipital lobes, such as MT/V5, the fusiform gyrus, the cuneus, and the parahippocampal gyrus. For both tasks, strong correlations (r values ranging from -0.76 to -0.85) were found between relative activations of cortical sensorimotor areas and the severity of cervical cord damage. This study shows an abnormal pattern of movement-associated cortical activations in patients with DNO, which extends beyond the 'classical' sensorimotor network and also involves visual areas devoted to motion processing. The correlation found between fMRI changes and the extent of cord damage suggests that such functional cortical changes might have an adaptive role in limiting the clinical outcome of DNO structural pathology.

Adult↗

PubMed1984

[Modular organization of callosal neurons in the sensomotor area of the cerebral cortex in the rabbit].

The density of distribution of callosal neurons in rabbit sensorimotor cortex was studied by means of horseradish peroxidase injection into the homotopic cortical area. The irregularity of density was evaluated visually and/or computed. Labelled callosal units were mostly small and medium-size pyramidal cells located primarily in layer III-IV and more rarely in layers V and VI. Layer III-IV revealed different patterns of labelled units grouping: in pairs, in 5-8 vertically situated cells, in clusters 120-200 micron wide, separated by areas with decreased density. The obtained results confirm previously made conclusion based on electrophysiological studies about the modular organization of callosal connections in sensorimotor cortex of rabbits.

Animals↗

PubMed1991

Both regenerating and late-developing pathways contribute to transplant-induced anatomical plasticity after spinal cord lesions at birth.

Fetal spinal cord transplants prevent the retrograde cell death of immature axotomized central nervous system (CNS) neurons and provide a terrain which supports axonal elongation in the injured immature spinal cord. The current experiments were designed to determine whether the axons which grow across the site of the neonatal lesion and transplant are derived from axotomized neurons and are therefore regenerating or whether the axons which grow across the transplant are late-growing axons that have not been axotomized directly. We have used an experimental paradigm of midthoracic spinal cord lesion plus transplant at birth and temporally spaced retrograde tracing with the fluorescent tracers fast blue (FB) and diamidino yellow (DY) to address this issue. Fast blue was placed into the site of a spinal cord hemisection in rat pups less than 48 h old. After 3-6 h to allow uptake and transport of the tracer, the source of fast blue was removed by aspiration and the lesion was enlarged to an "over-hemisection." A transplant of Embryonic Day 14 fetal spinal cord tissue was placed into the lesion site. The animals survived 3-6 weeks prior to the injection of the second tracer (DY) bilaterally into the host spinal cord caudal to the lesion plus transplant. Neurons with late-developing axons would not be exposed to the first dye (FB), but could only be exposed to the second tracer, diamidino yellow. Thus, neurons with a diamidino yellow-labeled nucleus are interpreted as "late-developing" neurons. Neurons axotomized by midthoracic spinal cord lesion at birth could be exposed to the first tracer, fast blue. If after axotomy they regrew caudal to the transplant, they could be labeled by the second tracer as well. We interpret these double-labeled neurons as regenerating neurons. If neurons labeled with fast blue and axotomized by the spinal cord hemisection either failed to regenerate or grew into the transplant but not caudal to it, they would be labeled only by the first dye. We have examined the pattern and distribution of single (FB or DY)- and double (FB + DY)-labeled neurons in the sensorimotor cortex, red nucleus, locus coeruleus, and raphe nuclei. The sensorimotor cortex contains only DY-labeled neurons. The red nucleus contains both FB- and FB + DY-labeled neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

[Ultrastructural changes in rabbit sensomotor cortex synapses following stimulation of the reticular formation].

Ultrastructural changes in the synapses of sensorimotor cortex caused by short and protracted stimulations of mid-brain reticular formation with single electric pulses were studied in rabbits. The observed submicroscopic shift in synaptic apparatus is regarded as a process of enhancing the activity of the sensorimotor synaptic apparatus with involvement of new interneuronal connections. Structural-functional changes in the synaptic apparatus occured at all levels of the sensorimotor cortex, with the predominance of this process at the upper level (layers I-IV); this is probably due to the greater representation of non-specific afferent endings in the upper cortical layers.

Animals↗