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F Cicirata

Publications and source records attributed to F Cicirata.

At least 37 records · Page 2Linked to original sources
PubMed1992

Homotopic transplant of fetal cortex to lesioned motor cortex of adult rats. A comportamental and anatomical study.

Previous investigations have shown that the transplant of fetal nervous tissue in adult, formerly injured, brain induces an improvement of the neurological deficits. The process underlying this finding is not yet known. It has been proposed that this process is favourably supported by the reconstruction of the damaged circuitry, replacing the injured neurons with the transplanted fetal cells. In the present study we have investigated the relation between the improvement of the neurological deficits and the anatomical integration of the transplanted neurons within the host brain. The plan of the investigation included two steps: the first step consisted of inducing neurological deficits by kainic acid lesion of the motor cortex and then studying the changes in the motor learning following a homotopic transplant of fetal cortex in the side of the lesion. The second step consisted of studying the anatomical integration of the transplanted cortex with the thalamus of the host. The results showed that the rats with injury of the motor cortex followed by solid transplant of fetal cortex (E 17) had a significantly greater recovery of the motor learning with respect to non-transplanted rats with a lesioned motor cortex. In the same rats, the connections between the transplanted cerebral cortex and the thalamus of the host has been investigated. WGA-HRP solution was injected in the thalamus and both labeled fiber terminals and labeled cells were searched for in the transplants. The results showed that: 1) the host thalamus projects to the transplanted cortex with a lower density than to the host cortex surrounding the transplant; 2) the thalamic projection to the host cortex is topographically organized, whereas the projection to the transplant is arranged in patches without any topographical organization; 3) the transplant does not send a significant projection to the thalamus of the host. In conclusion, the experimental findings demonstrate that the reconstruction of an injured thalamo-cortical circuitry of adult rats transplanting fetal neurons is not possible. The improvement of the functional deficits by the transplant of fetal tissue may be referred to aspecific factors enhancing the functional activity of the host cortex undamaged by the initial injury. The identification of the nature of the hypothesized factors requires further investigation.

Animals↗
PubMed1991

Neurotransmitter amino acid levels in rat thalamus and cerebral cortex after cerebellectomy.

Glutamate, aspartate, GABA, glycine and taurine levels have been measured in rat thalamus and in cerebral cortex at different time intervals (3rd, 7th, 15th, 30th day) after cerebellectomy. A decrease in glutamate, aspartate and GABA was detected at the 7th day after cerebellectomy in the thalamus and at the 15th day in the cerebral cortex; at the 30th day after cerebellectomy the levels of these amino acids in the thalamus and in the cerebral cortex were observed to have recovered to control values. No statistically significant difference in glycine and taurine levels in the thalamus and in the cerebral cortex after cerebellectomy could be seen. These results show that the functional recovery process after cerebellar injury is associated with a complex modification of amino acid levels in thalamus and in cerebral cortex.

Amino Acids↗
PubMed1991

[Anatomic connections between homotopic transplant of fetal cortical tissue and optic thalamus in adult rats].

The present research was planned to study the possibility to reconstruct a damaged neural circuitry by replacing the injured neurons with homotopic fetal cells. In adult rats the motor cortex was injured with intracortical injection of kainic acid solution. After a delay of 10-14 days, a block of cerebral cortex of fetal rats (E17) was transplanted in the cavity produced by the kainic acid in the motor cortex. After 2-3 months, WGA-HRP solution was injected in the thalamus of the host and both anterogradely labeled fiber terminals and retrogradely labeled somata cells were researched in the transplanted cortex. The results showed that: 1) the host thalamus projects to the transplanted cortex with less density compared to the host cortex surrounding the transplant; 2) the thalamic projection to the transplant is not topographically organized whereas the projection to the host cortex is; 3) the transplant was virtually void of a significant projection to the thalamus of the host. In conclusion, the results offer direct evidence that the reconstruction of an injured thalamocortical circuitry of adult rat is not possible by transplanting homotopic fetal neurons.

Animals↗
PubMed1991

[Motor organization of the lateral cerebellar nucleus of the rat].

The motor organization of the nucleus lateralis (NL) of the cerebellum of the rat was investigated by studying the motor effects following the electrical microstimulation. The movements evoked by the NL stimulation concerned prevalently the forelimb and the head segments. The movements of the hindlimb segments were evoked in only few cases. The NL is organized as a mosaic of zones without, or at least very little overlap. The various body segments are differently represented in the NL. Some of them are once represented (single representations). In other cases, the same movements were evoked by different NL regions (multiple representations). Finally, in a last lot of cases, various representations concerned the same body regions but from each representation a different type of movement was evoked (specific representations, i.e. displacement of an individual digit and flexion of all digits together). The topographical distribution of the representations in the NL cytological regions (magnicellularis, NLm; dorsolateral hump, DLH; subnucleus lateralis parvocellularis, slp) suggests the idea that each of them may be concerned in a specific motor activity: the NLm would control the position of the body, or of part of it, in the space; the DLH would be concerned in the oral (prevalently) and in the forelimb motor activity; the slp would be concerned in the exploration of the environment as well as in skilled movements of the distalmost forelimb segments.

Animals↗
PubMed1990

Functional organization of the direct and indirect projection via the reticularis thalami nuclear complex from the motor cortex to the thalamic nucleus ventralis lateralis.

The projection systems which arise from the motor cortex to reach the nucleus ventralis lateralis (VL) were investigated in the rat. They included a direct as well as an indirect projection via the reticularis thalami nuclear complex (RT). The investigation was performed in two steps: i) the former concerned the projection to the VL as well as to the RT from individual cortical foci electrophysiologically identified by the motor effects evoked by electrical stimulation; the second step concerned the projection from the RT to functionally defined regions of the VL. The direct projection from the motor cortex to the VL is somatotopically arranged. The projection reciprocates the fiber system directed from the VL to the motor cortex. Thus cortical zones controlling the motor activity of the proximal segments of the limbs project onto the regions of the VL that project back to these same cortical areas. With regard to cortical zones controlling the motor activity of the distal segments of the limbs, they not only project to the region of the VL specifically related to them, but also to the region of the VL associated with the cortical areas responsible for movements of the proximal parts of the same limb. In that case fiber terminals were more dense in the VL region controlling the proximal segment than in the region controlling the distal segment of the same limb. This organization suggests that proximal adjustments may be automatically provided by the motor activity of the distal segments of the same limb. The motor cortex projects to the rostral region of the RT with a precise topographical organization. In particular, the projection shows a dorsoventral organization in the RT in relation to the caudorostral body representation in the motor cortex. The projection which arises from the rostral region of the RT also reaches the VL with a topographical arrangement. It discloses a rostrocaudal organization in the VL in relation to a dorsoventral displacement in the RT. Comparing the projection from the motor cortex to the RT and that from this nuclear complex to the VL it was shown that the regions of the VL and their receptive cortical areas were associated with the same regions of the RT. It was therefore concluded that the motor cortical projection to the VL relayed by the RT is somatotopically organized. In both direct and relayed pathways the projections from "hind-" and "forelimb" motor area are segregated, whereas the "head" projection overlaps, at least partially, the "forelimb" terminal field.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Dentate control pathways of cortical motor activity. Anatomical and physiological studies in rat: comparative considerations.

The dentato-thalamocortical projections have been studied in albino rats using anatomical and physiological approaches. The anatomical analysis reveals that the dentatothalamic input to the ventral thalamus and the thalamocortical projection from this region onto the motor cortical area have a complex topographical arrangement. The corticothalamic reverberating pathways, both direct and through a relay in the nucleus reticularis thalami, are also roughly arranged in register with the same topographical pattern. This arrangement has been reconciled with that of the motor cortex, as determined by the motor effects of intracortical microstimulations. From this is inferred a somatotopical arrangement of the cerebellar nucleus lateralis, or dentate. These observations are confirmed by the results of our physiological analysis. The movements obtained with direct microstimulations of the nucleus lateralis affect either one joint (simple movements) or, more seldom, several joints (complex movements) of the same limb. A rough rostrocaudal arrangement is found in the nucleus lateralis: the caudocentral regions of the nucleus contain the representation of the musculature of forelimb and head, whereas the hindlimb is represented in the rostralmost part of the nucleus. A more complex organization is found to be related to the three cytoarchitectonic subdivisions of the nucleus lateralis. The main, large-celled part of the nucleus is engaged in the control of the large skeletal musculature. The dorsolateral hump is involved in mouth and peri-oral activities. The ventral, parvocellular, subnucleus is involved in fine exploratory movements of vibrissae, eyes, and forelimb wrist and fingers. The implication of the dentato-thalamocortical pathways in the cortical motor activities in the rat is discussed with attention to the dentate control of the "voluntary" motricity in primates.

Animals↗
PubMed1987

Spindle and EEG sleep alterations in subjects affected by cortical cerebellar atrophy.

All-night polygraphic records (EEG, EOG and ECG) were performed on 9 subjects. Four of them were affected by Familiar Cerebellar Atrophy (FCA) whereas the others were their blood relatives without clinical signs of cerebellar deficit. In the former FCA was diagnosed clinically and the cerebellar atrophy was confirmed by computer tomography (CT). In all the latter except one who showed slight cerebellar atrophy, the CTs were negative. The EEG sleep records of the FCA patients were characterized by slowly changing phases between synchronized and desynchronized sleep, instability of the synchronized sleep with frequent modifications of EEG activity, subnormal measurement of both REM and slow-wave sleep and presence of spindles in REM sleep (only in 2 patients). The spindle activity was reduced in two FCA subjects. The electroencephalographic sleep records of two BRs, one of which with small cerebellar atrophy, showed qualitative and quantitative alterations similar to those of FCA patients, even if marked to a lesser degree. Increased spindle densities were present in the same BRs who showed sleep abnormalities. The EEG alterations observed in the two BR subjects could show small cerebellar injuries which would be insufficient to induce clinical signs.

Adult↗
PubMed1987

The dentatorubral projection. An autoradiographic study in rats.

Although the dentatorubral projection is known to end specifically in the parvocellular part of the red nucleus, its topographical arrangement has never been elucidated. We therefore selectively injected the lateral cerebellar nucleus (homologous to the dentate nucleus of primates) of adult Wistar rats with tritiated leucine or proline in order to trace the dentatorubral boundaries. In all cases, the projection was found to extend rostrocaudally throughout the parvocellular red nucleus; dorsoventrally as well as mediolaterally, the fibers were distributed according to the location of the injection within the lateral cerebellar nucleus. Hence, caudal regions of the lateral nucleus send fibers dorsally at the rubral level, rostral regions project ventrally. This dorsoventral arrangement matches the segregation of the parvocellular red nucleus into a dorsal 'forelimb' region and a ventral 'hindlimb' region corresponding to its spinal efferents. In addition, only the ventral part of the lateral cerebellar nucleus, particularly the parvocellular region (subnucleus lateralis parvocellularis), projects to the lateral aspect of the parvocellular red nucleus. These results suggest a common pattern of organization of the dentatorubral and the dentatothalamic projections.

Animals↗
PubMed1986

Electrophysiologic properties and nature of ventrolateral thalamic nucleus neurons reactive to converging inputs of paleo- and neocerebellar origin.

Acute experiments were carried out in chloralose-anesthetized, curarized, and artificially ventilated cats to investigate the consistency and functional characteristics of converging cerebellar nuclear (fastigial, interpositus, dentate nuclei) inputs to single neurons of the ventrolateral thalamic nucleus, and the nature (thalamocortical relay or interneuronal) of its convergent neuronal population responsive to stimulation of the cerebellar nuclei. From unitary analysis of both extra- and juxtacellular recordings, we conclude that convergence of paleo- and neocerebellar impulses on thalamic ventrolateral neurons occurs widely, and that both excitatory (mono- and polysynaptic) and inhibitory (di- and polysynaptic) effects are induced on the same neurons by cerebellar nuclei stimulation; these effects concern about 40% of the thalamic ventrolateral neuronal population tested using the extracellular recording technique and about 75% of the ventrolateral nucleus neurons tested using the juxtacellular recording; activation of neocerebellar nuclear outputs generates mainly excitatory and excitatory-inhibitory response patterns, whereas activation of the paleocerebellar nuclear outputs evokes predominantly inhibitory and excitatory-inhibitory response patterns; the convergent paleo- neocerebellar neurons are found commonly in the more anterior ventrolateral nucleus stereotaxic planes; and from the results obtained by stimulation of the somatomotor cortical areas, a large proportion of the ventrolateral nucleus convergent units consists of thalamocortical relay cells. The results have implications for a possible integration between posture and voluntary movements at the level of the thalamic relay nucleus of the cerebellar-cortical pathway, and an interaction between central feedback and peripheral feedback in the programming, execution, and correction of voluntary movements.

Animals↗
PubMed1986

Functional organization of thalamic projections to the motor cortex. An anatomical and electrophysiological study in the rat.

In rats, horseradish peroxidase crystals were injected in motor cortical foci functionally identified by means of the motor effects evoked by electrical stimulations. The location in the thalamus of the neurons linked to different motor cortical foci was studied. Thalamic neurons were retrogradely labeled in both "motor" (ventralis lateralis and ventralis medialis) and "non-motor" nuclei: centralis lateralis, lateralis posterior, mediodorsalis and posterior thalamic nuclear group, as well as the ventrobasal complex. The ventrobasal complex was labeled after horseradish peroxidase injections in hindlimb and trunk motor areas. The ascending projections toward the motor cortex from both "motor" and "non-motor" thalamic nuclei are organized more precisely and more elaborately than previously reported. The motor cortical afferents from the nucleus ventralis lateralis are organized in three planes, rostrocaudally, dorsoventrally and mediolaterally. An inverted relation exists in the rostrocaudal plane between the nucleus ventralis lateralis and the motor cortex: the caudal motor cortex region (hindlimb) receives fiber inputs from the rostral region of the nucleus ventralis lateralis, whereas the caudal zone of the nucleus ventralis lateralis projects to the rostral motor cortex region (forelimb and vibrissae). A dorsoventral organization has also been observed in the rostral region of the nucleus ventralis lateralis: the ventral aspect is the source of fibers directed to the distal hindlimb region, whereas fibers originating from the dorsal aspect are directed to the proximal hindlimb area. A mediolateral relationship exists between medial and lateral sides of the nucleus ventralis lateralis and, respectively, proximal and distal forelimb cortical areas. There is some overlap between the various nuclear regions thus delineated. Four functional zones were found in the lateral half of the nucleus ventralis medialis and were classified according to their projection to the motor cortex; these are involved in motor control of the proximal and distal forelimb, vibrissae and ocular movements. The projection is topographically organized according to both an inverted rostrocaudal and a direct dorsoventral-mediolateral arrangement. Caudally, dorsal and ventral nuclear parts project to rostromedial (vibrissae) and rostrolateral (distal forelimb) regions of the motor cortex, respectively. More rostral nuclear zones project to more caudal (proximal forelimb, eye) cortical regions. There is little overlap between these four nuclear subdivisions. The nucleus centralis lateralis projects to vibrissae and proximal, as well as distal, forelimb areas.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Topographic organization of the cerebellothalamic projections in the rat. An autoradiographic study.

The topographical organization of the subnuclear projections towards the thalamus was studied with autographic methods in adult Wistar rats. The four cerebellar deep nuclei give rise to projections to the ventral region of the rostral thalamus. Most of the fibers end contralaterally, according to a topographical pattern; however, some fibers from each of the cerebellar nuclei recross the midline at the thalamic level and terminate ipsilaterally, within regions symmetric to those receiving the densest contralateral projection. These ipsilateral cerebellothalamic components arise in decreasing order from the caudal nucleus lateralis, the ventrocaudal nucleus medialis and the nucleus interpositus, respectively. The projections of the nucleus lateralis directed to the contralateral thalamus are topographically organized. (1) Within the nucleus ventralis lateralis, the rostral and caudal parts of the cerebellar nucleus lateralis project respectively to rostral and caudal regions; lateral and medial zones of the nucleus lateralis project, respectively, to medial and central aspects of the nucleus ventralis lateralis. (2) The nucleus ventralis medialis and particularly its caudal portion appears to receive the bulk of its afferents from the ventromedial portion of the nucleus lateralis including the "subnucleus lateralis parvocellularis". (3) The nucleus centralis lateralis receives fibers from most parts of the nucleus lateralis including the "dorsolateral hump". (4) The nucleus interpositus anterior projects to the dorsomedial aspect of the rostral nucleus ventralis lateralis. In the latter nucleus, the ventrolateral aspect of the central region receives projections in cases in which the nucleus interpositus posterior is largely involved. A particular emphasis is put on the different projections from the various subnuclear regions of the lateral nucleus. A comparison is attempted with the situation in the primates, particularly with regard to the question of the parvocellular subdivision of the lateral nucleus.

Animals↗
PubMed1985

An autoradiographic study of the cerebellopontine projections from the interposed and lateral cerebellar nuclei in the rat.

The projections from the cerebellar lateral and interposed nuclei onto the basilar pontine gray and nucleus reticularis tegmenti pontis (NRTP) have been studied in the rat by the use of the autoradiographic technique. Projections from both nuclei are mainly contralateral. Fibers from the lateral nucleus cover most of the NRTP, except its medial, parvocellular portion. In the pontine gray proper, fibers from the lateral nucleus are distributed to three rostrocaudally oriented columns: (i) in the medial nucleus, (ii) in the ventral nucleus, and (iii) in the dorsolateral and lateral nuclei. The projection is topographically arranged, so that caudal parts of the lateral cerebellar nucleus tend to project to more rostral regions than rostral parts of the lateral nucleus. The interposed nucleus gives rise to a sparser projection, apparently limited to the ventral NRTP and immediate peripeduncular zones. The functional implications of these results are discussed, with particular emphasis on the convergence of corticopontine afferents to the pontine regions involved, and on the reciprocal pontocerebellar pathways from these same regions.

Animals↗
PubMed1983

[Electroencephalographic characteristics of sleep in subjects with paleo and neocerebellar lesions].

The research was performed in order to study: 1) paleo and neocerebellar contributions in the sleep organization and 2) the electrical sleep activities at different time intervals during the functional compensation which follows the cerebellar lesion. Polygraphic sleep records (EEG, EMG, EOG) were performed on four subjects with surgical lesions more than 6 months old in cerebellar cortex (two subjects in paleo and two in neocerebellum). Another subject was studied before a surgical paleocerebellar lesion and at different time intervals after that (8th, 30th, 60th, and 90th day). Paleo and neocerebellar lesions showed different sleep abnormalities. The former induced both quantitative and qualitative alterations in the cyclic sleep organization, the latter did not show significant alterations in this organization but rather in transition between sleeping and waking and in sleep maintenance. The acute paleocerebellar lesion showed at the 8th and 30th day a strong reduction of the synchronized sleep (SS) and an increase of the desynchronized one (DS). In the successive records, 30th and 90th day, the SS/DS ratio increased to the values observed in the chronic paleocerebellar lesioned subjects.

Brain Injuries↗
PubMed1983

[Spindle activity during sleep in subjects with a deficit in pallesthetic sensibility].

Sleep spindle activity was studied on four subjects affected by pallesthesic deficit due to injury the posterior funiculi of the cord. The spindle activity was studied as density (number of spindles min.), duration and percent of sleep time utilized in spindle activity. The polygraph sleep records included EOG, EMG and 6 monopolar EEG recordings, 3 for each side, on the frontal, parietal and occipital regions. The records showed a spindle activity which was similar in different subjects and that was significantly higher than the physiological values. In fact, the spindle density was about 250%, the duration was about 130% and the spindle percent was about 280%, with respect to the physiological values assumed to be 100%.

Aged↗