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PubMed1989

Motor cortex projections to the thalamus. An autoradiographic study in the cat.

Adult cats received tritiated proline-leucine injections into the pericruciate cortex (areas 4 gamma and 3a) unilaterally and the projections to the thalamus were analyzed. Ipsilateral projections were found in the following nuclei, from rostral to caudal: ventral anterior, reticular, ventral lateral, central medial, paracentral, central lateral, ventral medial, mediodorsal, ventral posterolateral, ventral posteroinferior, centre median, parafascicular and posterior complex. In the contralateral hemithalamus sparse projections were found within the paracentral, central lateral and ventral medial nuclei.

Animals↗
PubMed1989

[Role of neurons of the thalamus and striopallidar complex of the human brain in ensuring the constancy of visual perception].

The neuronal impulse activity during visual testing for orientation sensitivity in different head tilts was recorded in parkinsonian++ patients diagnosed and treated with long-term intracerebral electrodes implanted into different nuclei of the thalamus and striopallidar complex. It was revealed that some neuronal populations responded only to the definite orientation of the stimuli. The "preferable" orientations were not changed for the most orientation-selective neurons during left and right head positions differing by 90 degrees.

Electrodes, Implanted↗
PubMed1989

[Ventrolateral nucleus of the cat thalamus and its connection with field 4 of the cerebral cortex].

By means of silver nitrate impregnation after Fink-Heimer and Golgi-Kopsch structural peculiarities have been revealed in the neurons of the ventral lateral nucleus (VL) of the cat thalamus and its connections with the motor cortex. The results of the observations demonstrate a complex morphological organization of the VL. It makes reciprocal connections with the field 4 of the motor cortex. Terminal fibers from the VL end in the layers I, III, V and VI of the field 4 gamma and in the whole thickness of the fundal field anatomically having no layers. No degenerating fibers are found after destruction in the fields 4 delta and 4 sfu. Basing on measurements of neuronal nuclei in the VL two cell populations are revealed, that demonstrates presence of two types of the neurons in the VL--large relay and small short axonal, each of them having several varieties. Complex synaptic contacts in the VL in the form of serial synapses and triads are also demonstrated.

Afferent Pathways↗
PubMedDate not supplied

GABA-immunoreactive neurons in the mediodorsal nucleus of the monkey thalamus.

The mediodorsal nucleus of the thalamus is an important component of the brain's circuitry for memory 9,20 and yet surprisingly little is known of its intrinsic organization. In the present study we have examined the distribution, spatial relationships and morphology of gamma-aminobutyric acid (GABA)-containing cells within the magnocellular and parvocellular subdivisions of the mediodorsal nucleus. These subdivisions have anatomically and functionally distinct connections with the orbital (limbic) and dorsolateral (association) areas of the prefrontal cortex, and accordingly, we investigated whether there were corresponding differences in their local circuit organization. Our findings show that round or ovoid GABA-immunoreactive neurons were abundant in both subdivisions. However, these neurons were larger in diameter in the magnocellular aspect (mean diameter = 10.4 +/- 0.1 micron) than in the parvocellular moiety (mean diameter = 9.9 +/- 0.1 micron) and the intensity of reactivity was also greater for the magnocellular neurons. Comparison of the densities of GABA-immunoreactive neurons revealed not only a greater density of neurons in the parvocellular division but also that the proportion of all neurons which were GABA-containing was greater in this region. These differences in the morphology and density of inhibitory local circuit neurons may contribute to the functional duality of prefrontal cortex innervated by these thalamo-cortical pathways. Certain qualitative features were common to both subdivisions; thus GABA-immunoreactive neurons were found in small clusters throughout the magnocellular and parvocellular divisions of the mediodorsal nucleus and, in addition, regions with few or no GABA-immunoreactive cells were often surrounded by strings of GABA-containing neurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Study of the connections of the thalamus in Rana temporaria frogs by the peroxidase method].

In frogs, on the base of the axonal transport of horseradish peroxidase, the connections ascending to the primordial hippocamp were shown from the ipsi- and contralateral pyriform pallium, contralateral primordial hippocamp, ispilateral amygdala and nucleus accumbens, as well as from rostral parts of the postero-central thalamic nucleus (bilaterally). The ascending connections from the dorsal column nuclei were followed with reliability till the rostral parts of the contralateral mesencephalic tegmentum, but very likely they reach also the dorsal thalamus.

Animals↗
PubMed1986

[Place of the thalamus in the network of interconnections between the association and limbic cortices in the monkey].

Anatomophysiological criteria underlying the definition of associative cortex as well as limbic cortex include some imprecise data. The original notion of "cortical association spheres" (Flechsig) with no connections with the thalamus has rightly been abandoned, and that of the macroscopic "large limbic lobe" (Broca) fails to stand up to histologic or hodologic findings. However, the concept of cortical areas implicated specifically in multiple sensorial integration, sensory-motor coupling and control of behavior lasts due to necessity. In the monkey, the posterior parietal cortex of area 7 (PG area), the cortex of the upper slope of the superior temporal sulcus (STS) and the prefrontal cortex anterior to the sulcus arcuatus exchange direct corticocortical connections, receive afferents from sensory cortex and are not connected to specific thalamic relays. The term "associative" in its widest sense applies more particularly therefore to these cortical areas organized in networks. On the internal surface of the hemisphere, the cingular gyrus, retrosplenial cortex and parahippocampic gyrus (TF and TH areas) which occupy the major part of the limbic lobe, participate in the formation of this network and exchange direct cortico-cortical connections with the associative cortex defined above. The use of anterograde (labelled aminoacids) and retrograde (peroxidases) markers and of fluorescent dyes, allowing double retrograde labelling, demonstrates that the median pulvinar nucleus is connected with the knots of the associative cortical network. This thalamic nucleus, of a relatively increased size from phylogenetic evolution, is therefore excluded from the classification opposing specific and diffuse projection nuclei. In contrast to the thalamic reticular nucleus, which lacks cortical projections, and to the nuclei of the internal medullary band, which have the striatum as main target, the median pulvinar is a thalamic structure connected directly and specifically with each of the cortical areas, lesions of which result in negligence behavior.

Animals↗
PubMed1986

[Memory disorders in lesions of the thalamus in man].

Isolated memory disorders occur after bilateral involvement of thalamus. Anterograde amnesia is not complete; retrograde amnesia is always severe. Four groups of thalamic nuclei may be affected: anterior nuclei; midline nuclei, medialis dorsalis nuclei; intralaminar nuclei. A pathophysiologic interpretation is proposed. Three kinds of memory processes may be involved: consolidating process that leads to the formation of memory traces (anterior nuclei, midline nuclei); retrieving process that leads to the activation of memory traces (intralaminar nuclei); temporal organizing process that regards ancient et recent memory traces (medialis dorsalis nuclei).

Amnesia↗
PubMed1987

[Unit activity of neurons of the posterior ventral nucleus of the thalamus for various waking stages in the normal cat].

Using the electrocortical activity in the sensorimotor cortex as an index, three distinct levels of motionless waking can be identified in the cat, all three different from active waking and from slow sleep (attentive waking, quiet waking and drowsiness). It has now been shown that spontaneous and evoked single unit activities in n. ventralis posterior of the thalamus undergo significant changes when passing from one level of waking into another one.

Animals↗
PubMed1986

[Role of the ventrobasal complex of the thalamus in nociception and pain: data obtained in the normal rat and in a model of clinical pain].

Recent anatomical, electrophysiological, neuropharmacological and behavioural studies have provided new elements for the understanding of the role of the thalamus in nociceptive and pain mechanism. Data presented here demonstrate that the thalamic ventrobasal complex (VB), which receives direct afferents from the spinothalamic tract in the rat and monkey, plays a role in the sensory-discriminatory component of pain in these two species. Apart from the electrophysiological aspect, we discuss the effects of analgesic compounds on neuronal responses observed at this level and modifications in a nociceptive reaction threshold after lesions of this structure in the non-anesthetized freely moving animal. Data obtained in the normal rat are compared with those obtained under the same experimental conditions in a clinical pain model: the arthritic rat. In these animals the capacity of the VB neurons to respond to somatic stimuli is profoundly modified, many of them being activated by moderate stimuli from inflamed joints (lateral pressure, movements). Spinal tracts transmitting messages from these joints appear to differ (at least in part) from those transmitting nociceptive messages in the normal rat. Finally, at similar doses, morphine is much more effective in these animals than in the normal rat. Results of these studies show that nociception and clinical pain are not always exactly dependent on the same systems.

Animals↗
PubMedDate not supplied

[Comparative characteristics of the neuronal activity of the anterodorsal and anteroventral nuclei in thalamus slices from guinea pigs].

Extracellular investigation of neurons of the anterodorsal (AD) and anteroventral (AV) nuclei in the incubated slices of the thalamus of guinea pigs and rabbits revealed unusual properties of the AD units. They responded only to electrical stimuli of considerable duration (1-5 ms) by multispike initial bursts or by prolonged (1-15 s) high frequency phasic discharges. Summation of effects of successive stimuli following with intervals of 2-30 s was necessary for development of phasic discharges. Prolonged refractory state (up to 2-15 s) followed the discharges. They were blocked in low Ca2+, high Mg2+ medium and facilitated in a medium with high concentration of K+. The nature of unusual properties of AD neurons, not present in the neighbouring AV nucleus, are discussed.

Action Potentials↗
PubMed1986

[Role of the thalamus in auditory lateralization: anatomic studies].

Study of human thalamus cells architecture failed to demonstrate any significant asymmetry between the two thalami in the pulvinar region. In contrast, asymmetry, more pronounced on the left side, exists in the posterior lateral nucleus. Relations linking this nucleus to the inferior parietal region were confirmed by histologic findings in dyslexic patients. On the other hand, the functional asymmetry for specific vocalizations demonstrated in the macaque does not correspond to asymmetry of the cerebral cortex or inferior corpora quadrigemina but to asymmetry of the median geniculate bodies, a finding correlated with auditory functional dominance.

Animals↗
PubMed1986

[Effect of lesions of the ventromedial nucleus of the thalamus on cerebral metabolism: experimental study in the rat using the 14C-deoxyglucose method].

Local cerebral glucose utilization (LCGU) was studied quantitatively in awake rats one week and one month following unilateral electrolytic lesion of the ventromedial thalamic nucleus (VM). Significant decrease in LCGU were observed in the ipsilateral cortex as well as in some contralateral cortical areas and bilateral subcortical structures. The modifications by the VM lesion, of the metabolic activations induced by electrical stimulation of substantia nigra pars reticulata (SNR, main afference of the VM) were investigated also. Results suggest that VM is an important relay nucleus on the pathways directed from one SNR towards ipsilateral corticostriatal system and contralateral thalamus and basal ganglia. Finally, one month following the VM lesion a recovery of metabolic activations induced by SNR stimulation was observed whereas basal glucose consumption remained decreased.

Animals↗
PubMed1979

[Effects of electric stimulation and destruction of the centrum medianum of the optic thalamus in patients with akinetic forms of parkinsonism].

Results of electrostimulation and destruction of the median centre of the thalamus in 15 patients with parkinsonism and in 7 patients with uncontrollable pain are presented. Reactions of activation and inhibition in the psychoemotional, somatic and vegetosensory spheres in response to the stimulation are described. Data on bioelectrical activity changes in the cortex of the large hemispheres are presented. Special studies of the effect of the median centre destruction on the muscular tone and tremor were carried out. In the akinetic forms of parkinsonism the effect of reactivation after the median centre destruction was found to be of little clinical importance.

Cerebral Cortex↗
PubMed1985

[Origin of component N16 in short latency somatosensory evoked potentials (SSEP) to median nerve stimulation--correlation between component N16 and thalamus].

Short latency somatosensory evoked potentials (SSEP) to median nerve stimulation consists of four main subcortical components, namely P 9, P 11, P 13 and N 16 which appears before cortial N 18. However, the origin of component N 16 is a subject of controversy. In an attempt to learn about the generator source(s) of component N 16, SSEP was recorded from 25 patients with various focal lesions of the brain stem and/or thalamus, and abnormalities of the each potential was correlated to the clinically and radiologically defined site of the lesions. Furthermore, the effects of the different frequency in stimulation were also investigated in 6 normal subjects, because latency changes of each component might contribute to the understanding of the generation. Recordings were obtained from 13 patients with brain stem lesion which included 3 cases with pontine hemorrhage, 3 cases with pontine tumor, 3 cases with cerebello-pontine angle tumor, one case of pontine angioma, one case of chordoma, one case of tentorial tumor and one case of MLF syndrome. SSEP changes in these cases were classified into four types as follows: type 1: no response over the base line was recorded, type 2; some responses over the base line were recorded but N 16 was uncertain, type 3; component N 16 was clearly identified but its latency was significantly prolonged, type 4; component N 16 was divided into two peaks. Bilateral abnormality on SSEP with splitted combination of these four types in various degree was observed. Furthermore, these SSEP abnormalities were seen even in the some cases without sensory disturbance. On the other hand, component N 16 was clearly identified in all 12 patients with thalamic lesion which included 11 cases with thalamic hemorrhage and one case with thalamic tumor on the effected side. Comparison of latency and amplitude between normal side and affected side statistically showed no laterality of components P 9, P 11 and P 13, but a tendency of delay in latency of component N 16 on the affected side. Different stimulus repetition rate revealed some other characteristics of each component. Electrical stimuli to median nerve at the wrist were delivered at rates of 3, 6, 9, 12, 15, 18, 21, 24 and 27 Hz. Latencies of components P 9, P 11, P 13, N 16 in Fro.-Cv 7 lead and component N 18 in Par.-Erb lead were measured and all latency changes were calculated relative to the 3 Hz stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

[Bilateral, symmetrical hemorrhagic infarction of the basal ganglia and thalamus following neonatal asphyxia].

With the advancement of perinatal intensive care, the occurrence of subependymal germinal matrix hemorrhage (= GMH) in low-birth-weight (premature) infants has became a major concern in perinatal medicine. The pathophysiology of the GMH has long been controversial. The introduction of computed tomographic (= CT) scanning to perinatal medicine has revealed various pathological events heretofore unknown in newborn infants having respiratory and circulatory distress. At our serving the entire Osaka Prefecture, infants suffering from birth asphyxia with severe perinatal brain damage were found to have CT findings distinguishable from those of GMH. We report three asphyxiated newborn infant who had hemorrhagic infarction in bilateral caudate nucleus, striatum and thalamus on the CT scan. Reports of similar findings are rare, and ours is the first serial observation of such CT scan image in newborn infants. The mechanism of development and pathology of this pathological condition have been variously argued as pathophysiology of GMH. The present study lacks postmortem examination, however, the findings in serial CT scans in three infants and review of the literatures related to the pathology of neonatal asphyxia indicate the following course. The thrombosis in the internal cerebral veins led to severe swelling of the brain, and hemorrhage occurred with the reduction in the swelling, eventually resulting in diffuse leukomalacia. Etat marbré (status marmoratus), mentioned earlier, is considered to represent a milder stage of this pathologic course.(ABSTRACT TRUNCATED AT 250 WORDS)

Asphyxia Neonatorum↗
PubMedDate not supplied

[Features of corticofugal effects of the motor area of the cortex on processing of heterogeneous afferentation in the parafascicular complex of the thalamus in the cat].

Evoked potentials to somatic and visual stimuli were recorded in the parafascicular complex (parafascicular nuclei--centrum medianum--Pf--CM) of the thalamus of cats anaesthetized by nembutal. Cooling of the motor cortex was also used. The influence of the motor cortex on processing of the visual and somatic afferent signals at the thalamic level was found to be direct but different by its character. The motor cortex exerted unidirectional facilitatory modulatory action of a tonic type on the processing of visual afferentation and general facilitatory influence against the background of which particular excitatory and inhibitory effects were seen which it exerted on the processing of somatic signals. Episodically the motor cortex completely controlled the afferent inputs activated by somatic impulses. The motor cortical area non-equally influenced afferentation of the same modality forming the different components of the evoked potentials in Pf--CM. On the base of our present and earlier obtained data an idea has been formed of existence of a general principle of differentiated influences of polysensory areas on heterogeneous afferentation on nonspecific and association thalamic nuclei, and of realization of these influences through separation of functionally isolated subsystems in descending pathways. Each of the subsystems by closing separate thalamo-cortical circuits might transmit signals of a single modality.

Animals↗
PubMed1985

[Analysis of the background activity of neurons of the anterior (limbic) nuclei of the thalamus in the rabbit].

Background activity recorded extracellularly from three anterior (limbic) nuclei of the thalamus was analyzed in chronic unanesthetized rabbits. The neurons of anteroventral nucleus possessed high mean frequency of discharges and highly differentiated dynamic patterns of activity with "inactivation bursts", modulation in delta- or theta-frequencies and episodic rhythmic discharges 12-14 Hz correlated with EEG-spindles in the posterior cingulate cortex. The activity of anteromedial nucleus neurons was lower and much more uniform; it consisted of alternating randomized spikes and "inactivation bursts". The activity of anterodorsal nucleus neurons was represented mainly by high-frequency grouped discharges with long intergroup intervals.

Action Potentials↗
PubMed1981

On the nucleus endymalis of the human thalamus.

In the present article the shape and extent of the nucleus endymalis in the human thalamus is described. By means of a newly developed method of selective staining of intracellular lipofuscin granules with aldehydefuchsin it is possible to examine the three-dimensional shape of the griseum in complete series of 800 micrometer thick slices. The nucleus endymalis can be divided into an invariably occurring strongly pigmented caudal pars pigmentosa with clear-cut boundaries and an oral pars commissuralis. The weakly pigmented oral part is only found in brains with developed massa intermedia and varies considerably from individual to individual. The pars pigmentosa is characterized by its periventricular position medial to the nucleus parafascicularis. Differences in nomenclature and outlines of topographically corresponding thalamic nuclei of other authors are discussed. It is assumed that the pars pigmentosa a least partly corresponds to the catecholaminergic cell group A11 in the rat brain (Dahlström and Fuxe 1964). Finally, its possible functional connections to the dorsal periventricular bundle and its significance for stimulation-produced analgesia (SPA) in man are discussed.

Aged↗