Anteromedial Nucleus Research Articles

Effects of regional ablation of midline cortex on alternation learning by rats

Abstract Effects of anterior limbic and posterior cingulate lesions on learning of a nonspatial alternation problem by rats were compared. Food-deprived rats were trained to traverse a runway in which food reward was present on every other trial. Under these conditions normal rats learn to run fast on rewarded trials and slowly on non-rewarded trials. Lesions were placed in anterior limbic or posterior cingulate regions prior to training. Controls underwent sham operations. After 15 days of training, anterior limbic lesioned animals had failed to learn the alternation. Alternation learning by the rats with posterior cingulate lesions did not differ significantly from that of controls. Additional training improved the performance of some anterior limbic lesioned animals but not to the extent that they performed as well as controls. In anterior limbic lesioned brains, degree of retrograde degeneration in anteromedial thalamic nuclei was correlated with degree of improvement after additional training. The results are interpreted to indicate functional differentiation of anterior limbic and posterior cingulate cortical regions in the rat.

BEHAVIORAL EFFECTS OF MAMMILLOTHALAMIC TRACTOTOMY IN CATS.

THE MAMMILLOTHALAMIC TRACTS are distinctive features of the mammalian diencephalon. In the phylogenetic scale of mammals these structures maintain, or even increase, their relative anatomical prominence. It is well established that the tracts consist of efferent fibers from the mammillary bodies projecting to shown conclu the anterior .sively for the thalamic nuclei cat that each la of the thalamus. Recent work has teral mammillary nucleus projects bilaterally to the anterodorsal nuclei, and fibers nuclei project ipsilaterally to the anteromedial nuclei. Collaterals or primary fibers also appear to to terminate in the ventromedial thalamic nuclei ( from and the medial mammillary anteroventral thalamic

An experimental study of the relation between the medial mamillary nucleus and the cingulate cortex.

The cellular changes in the mamillary nuclei following lesions of the cingulate cortex, the anterior thalamic radiation and the anterior thalamic nuclei have been studied in rabbits varying in age from 10 days to young adults. Distinct cellular degeneration ranging in severity from slight cell shrinkage to complete cell loss occurs in the medial and supra-mamillary nuclei subsequent to the retrograde changes in the anterior thalamic nuclei. The severity of this ‘retrograde transneuronal degeneration’ is a function of the age of the animal at the time of operation and of the post-operative survival period. With the aid of this technique, it has been shown that the caudal part of the pars anterior and the ventro-lateral two-thirds of the pars medialis of the medial mamillary nucleus project to the antero-medial nucleus of the thalamus, the pars basalis to the antero-dorsal nucleus and the pars posterior to the antero-ventral nucleus. No changes were observed in the lateral mamillary nucleus in any of the experiments.

Microscopic study of oculomotor nucleus in human adult. II.

The oculomotor nucleus comprise the chief nucleus, the median nucleus, the parasympathetic nucleus, the anteromedial nucleus, the dorsocentral nucleus and the accessory nucleus of the parasympathetic nucleus, the last of my own discovery. The nerve cells in the chief nucleus are represented in their majority by large motor cells provided with many processes and showing virile appearance. The long processes being sometimes double and some-times bifurcated per cell, the total number of the oculomotor root fibres is larger than that of the cells. The short processes apparently end sharply, either unbranched or branched, but their terminal formation is not enough clarified. The cell nucleus is comparatively small and located near the centre of the cells. The cells of the chief nucleus are partially represented by smaller cells, 1/2 to 1/3 in size of the large cells, pear-shaped in form, unipolar or bipolar, with a large cell nucleus, presumably being of vegetative nature. Cells of a third type are extremely few in number. Their size is not much different from the large motor cells, but in form, they are globular and unipolar. They are very similar to the sensory nerve cells found in the nucleus mesencphali n. trigemini, and are without doubt of sensory nature. In the inner and the ventral parts of the fasciculus longitudinalis medialis are found some cells of the same form as the motor cells in the chief nucleus, with which a small number of small vegetative cells are commingled. It seems impossible to divide the chief nucleus distinctly into the various motor centres having each fixed boundary for the outer ocular muscles, because they may be thought diffused over comparatively wide parts, overlapping each other to an extent. The nucleus medianus is inseparable from the chief nucleus at the caudal pats but the boundary between them become more definite as the higher levels are reached. The nerve cells in the basal parts are similar to those in the chief nucleus, but in the upper reaches, more and more bipolar club- or spindle-like cells come into evidence. Also, some smaller cells resembling vegetative nerve cells in the chief nucleus are observable. The cells in the parasympathetic nucleus are small, about 1/3 of the size of the motor cells in the chief nucleus, are unipolar or bipolar, oblong in shape and arranged rather densely in the direction conforming with the arcuate form of this nucleus. Their protoplasm is only weakly stained, their cell nucleus is oversized, and their long processes are represented by minute fibres. Since such minute fibres are also observable in the oculomotor nerve root, I am inclined to give adherence to the proposal that this nucleus is the centre for the pupillar contraction. I have discovered a small group of nerve cells strongly resembling those in the parasympathetic nucleus on the rostrodorsal side between the fasciculus longitudinalis medialis and the chief nucleus. I propose to call this new nucleus the accessory nucleus of the parasympathetic nucleus. The anteromedial nucleus is of the same nature as the nucleus parasym-pathicus, considering the form and the arrangement of the cells. This fact is further evidenced by the union of this nucleus with the parasympathetic nucleus through a cell-bridge containing such cells. The nerve cells in the nucleus dorsocentralis are somewhat smaller than, but similar to, the motor cells in the chief nucleus. In this nucleus, some smaller vegetative cells, as have been found in the chief and the median nucleus, are observable in a small number. Thus, this nucleus also may be assumed to represent one of the oculomotor centres.

Microscopical study of oculomotor nucleus in human adult. I.

The oculomotor nucleus comprise the chief nucleus, the median nucleus, the parasympathetic nucleus, the anteromedial nucleus, the dorsocentral nucleus and the accessory nucleus of the parasympathetic nucleus, the last of my own discovery. The nerve cells in the chief nucleus are represented in their majority by large motor cells provided with many processes and showing virile appearance. The long processes being sometimes double and some-times bifurcated per cell, the total number of the oculomotor root fibres is larger than that of the cells. The short processes apparently end sharply, either unbranched or branched, but their terminal formation is not enough clarified. The cell nucleus is comparatively small and located near the centre of the cells. The cells of the chief nucleus are partially represented by smaller cells, 1/2 to 1/3 in size of the large cells, pear-shaped in form, unipolar or bipolar, with a large cell nucleus, presumably being of vegetative nature. Cells of a third type are extremely few in number. Their size is not much different from the large motor cells, but in form, they are globular and unipolar. They are very similar to the sensory nerve cells found in the nucleus mesencphali n. trigemini, and are without doubt of sensory nature. In the inner and the ventral parts of the fasciculus longitudinalis medialis are found some cells of the same form as the motor cells in the chief nucleus, with which a small number of small vegetative cells are commingled. It seems impossible to divide the chief nucleus distinctly into the various motor centres having each fixed boundary for the outer ocular muscles, because they may be thought diffused over comparatively wide parts, overlapping each other to an extent. The nucleus medianus is inseparable from the chief nucleus at the caudal pats but the boundary between them become more definite as the higher levels are reached. The nerve cells in the basal parts are similar to those in the chief nucleus, but in the upper reaches, more and more bipolar club- or spindle-like cells come into evidence. Also, some smaller cells resembling vegetative nerve cells in the chief nucleus are observable. The cells in the parasympathetic nucleus are small, about 1/3 of the size of the motor cells in the chief nucleus, are unipolar or bipolar, oblong in shape and arranged rather densely in the direction conforming with the arcuate form of this nucleus. Their protoplasm is only weakly stained, their cell nucleus is oversized, and their long processes are represented by minute fibres. Since such minute fibres are also observable in the oculomotor nerve root, I am inclined to give adherence to the proposal that this nucleus is the centre for the pupillar contraction. I have discovered a small group of nerve cells strongly resembling those in the parasympathetic nucleus on the rostrodorsal side between the fasciculus longitudinalis medialis and the chief nucleus. I propose to call this new nucleus the accessory nucleus of the parasympathetic nucleus. The anteromedial nucleus is of the same nature as the nucleus parasym-pathicus, considering the form and the arrangement of the cells. This fact is further evidenced by the union of this nucleus with the parasympathetic nucleus through a cell-bridge containing such cells. The nerve cells in the nucleus dorsocentralis are somewhat smaller than, but similar to, the motor cells in the chief nucleus. In this nucleus, some smaller vegetative cells, as have been found in the chief and the median nucleus, are observable in a small number. Thus, this nucleus also may be assumed to represent one of the oculomotor centres.

Effects of thalamic stimulation in unanaesthetised animals The arrest reaction and petit Mal-like seizures, activation patterns and generalized convulsions

A cinematographic analysis of the responses of cats to local stimulation of various portions of the thalamus and hypothalamus has been carried out with histological control and with electroencephalography correlation both during operation and post-operatively in an attempt to further investigate the hypothesis of a diencephalic origin for petit mal epilepsy. The results of this investigation may be summarized as follows: 1. (1) Electrical stimulation within the intralaminar nuclei of the thalamus, especially rostrally and bordering upon the dorso-medial and antero-medial nuclei, produced a sudden arrest of responsiveness which we have called the “arrest reaction”. During this arrest the animal would remain immobile, with no loss of tone, and failed to respond to usually effective stimuli. 2. (2) The “arrest reaction” would persist beyond the period of thalamic stimulation in the form of an after-discharge resembling very closely a petit mal type of seizure in man, including the slight twitching movements about the eyes and face so commonly seen in these attacks, and would cease abruptly. 3. (3) More intense and more rapid stimulation of the same regions producing the “arrest reaction” would produce first a petit mal-like attack followed by a major generalized convulsion or “grand mal” seizure. 4. (4) Electrocorticograms showed that stimulation of the intralaminar regions of the thalamus which produced a generalized recruiting type of control of the rhythmic activity of the cortex also produced the generalized changes in behaviour which we have termed the “arrest reaction”. During the petit mal-like seizures a bilaterally synchronous 3 per second wave and spike discharge was recorded from the cortex and was associated with a similar type of wave form in the thalamus. During the grand mal-like attacks the electrocorticogram and electrothalamogram showed rapid high voltage activity simulating closely the form of the EEG at the onset of such attacks in man. 5. (5) Autonomic system responses including a complex defensive pattern of behaviour with sham rage or a fear pattern associated with flight were reproduced particularly from the hypothalamus and occasionally from the overlying midline nuclei of the thalamus. These results corresponded closely with the detailed analysis of such responses as reported by Hess. 6. (6) Extrapyramidal types of movement such as tonic postural states, turning of the head and body, circling movements, alternating movements of a limb, and so forth were reproduced from what was presumed to be the thalamic or sub-thalamic extrapyramidal system. These results also correspond closely to those described by Hess. 7. (7) Control studies in which stimulation of sensory relay nuclei was carried out produced no such reactions but only responses which gave one the impression of a paraesthesia or of a reaction to a sensory stimulus. On no occasion was any loss in general responsiveness or change in emotional behaviour observed when stimulating sensory relay nuclei. 8. (8) It is concluded from observations in the cat that the diffuse thalamo-cortical projection system which we have called the thalamic reticular system has a very widespread and profound effect on behaviour as a whole and may be involved in the mechanism of petit mal and generalized convulsive seizures as seen in man.

Effects of thalamic stimulation in unanaesthetised animals

Abstract A cinematographic analysis of the responses of cats to local stimulation of various portions of the thalamus and hypothalamus has been carried out with histological control and with electroencephalography correlation both during operation and post-operatively in an attempt to further investigate the hypothesis of a diencephalic origin for petit epilepsy. The results of this investigation may be summarized as follows: 1.(1) Electrical stimulation within the intralaminar nuclei of the thalamus, especially rostrally and bordering upon the dorso-medial and antero-medial nuclei, produced a sudden of responsiveness which we have called the arrest reaction. During this the animal would remain immobile, with no loss of tone, and failed to respond to usually effective stimuli. 2.(2) The arrest would persist beyond the period of thalamic stimulation in the form of an after-discharge resembling very closely a petit type of seizure in man, including the slight twitching movements about the eyes and face so commonly seen in these attacks, and would cease abruptly. 3.(3) More intense and more rapid stimulation of the same regions producing the arrest would produce first a petit mal-like attack followed by a major generalized convulsion or mal seizure. 4.(4) Electrocorticograms showed that stimulation of the intralaminar regions of the thalamus which produced a generalized recruiting type of control of the rhythmic activity of the cortex also produced the generalized changes in behaviour which we have termed the arrest reaction. During the petit mal-like seizures a bilaterally synchronous 3 per second wave and spike discharge was recorded from the cortex and was associated with a similar type of wave form in the thalamus. During the grand mal-like attacks the electrocorticogram and electrothalamogram showed rapid high voltage activity simulating closely the form of the EEG at the onset of such attacks in man. 5.(5) Autonomic system responses including a complex defensive pattern of behaviour with sham rage or a fear pattern associated with flight were reproduced particularly from the hypothalamus and occasionally from the overlying midline nuclei of the thalamus. These results corresponded closely with the detailed analysis of such responses as reported by Hess. 6.(6) Extrapyramidal types of movement such as tonic postural states, turning of the head and body, circling movements, alternating movements of a limb, and so forth were reproduced from what was presumed to be the thalamic or sub-thalamic extrapyramidal system. These results also correspond closely to those described by Hess. 7.(7) Control studies in which stimulation of sensory relay nuclei was carried out produced no such reactions but only responses which gave one the impression of a paraesthesia or of a reaction to a sensory stimulus. On no occasion was any loss in general responsiveness or change in emotional behaviour observed when stimulating sensory relay nuclei. 8.(8) It is concluded from observations in the cat that the diffuse thalamo-cortical projection system which we have called the thalamic reticular system has a very widespread and profound effect on behaviour as a whole and may be involved in the mechanism of petit and generalized convulsive seizures as seen in man.