Biomedical subjects

E Irle

Publications and source records attributed to E Irle.

At least 37 records · Page 2Linked to original sources

PubMed1986

Cortical projections originating from the cat's insular area and remarks on claustrocortical connections.

The cortical projections originating in the cat's insular cortex and claustrum were investigated with the aid of the horseradish peroxidase retrograde tracing technique. Twenty small injections of horseradish peroxidase were distributed along lateral and medial regions of the hemisphere. Labeling in the insular cortex occurred following all injections except those six situated along the lateral gyrus--that is, within the visual cortex. In the claustrum labeled neurons were found following all injections, except following the injection situated in the posterior temporal area. Claustral labeling was frequently more intense than insular labeling. The injections into the occipital cortex that revealed no insular innervation nevertheless received a considerable number of claustral projections. As the insular cortex itself receives at most a minor projection from the claustrum the differing cortical projection patterns of insula and claustrum have to be considered unrelated. Our findings confirm the view that the claustrum projects to most regions of the cerebral cortex; these projections are at least in part topographically organized. A topographical pattern can also be constructed for the insular cortex, though it is less stringent than for the claustrocortical connections. Both the afferent and efferent connections of the insula show similarities to those of the prefrontal cortex. Nevertheless, the insula differs in that it receives strong input from the sensory associative nuclei of the thalamus. Consequently, and in line with behavioral observations following its ablation, we consider the insula as involved in the temporal structuring of perceived patterns.

Animals↗

PubMed1986

Korsakoff and alcoholic subjects are severely impaired in animal tasks of associative memory.

Korsakoff subjects, members of the Alcoholics Anonymous, and alcoholics with 1 week or 5-6 months of abstinence were tested in a concurrent object discrimination task with 10 and 20 pairs of objects and compared to control subjects matched for age and education. The anonymous alcoholics were moderately Korsakoff subjects strongly impaired, whereas alcoholics with 1 week or 5-6 months abstinence performed similar to control subjects. The results are discussed with respect to current research on human amnesia and comparative neuropsychological topics.

Adult↗

PubMed1986

Afferent connections of the substantia innominata/basal nucleus of Meynert in carnivores and primates.

Afferent connections to the substantia innominata/nucleus basalis complex of monkeys and cats were traced by using the method of retrograde transport of horseradish peroxidase (HRP). Altogether ten injections of HRP were performed in four monkeys (Saimiri sciureus, Callithrix jacchus, Galago senegalensis) and in four cats, with either vertical or oblique needle approaches. The entire brains excluding the olfactory bulbs and the cerebellum were then screened for labeled neurons. In both monkey and cat brains, many retrogradely labeled neurons could be detected in the amygdala, hypothalamus, midline thalamus, zona incerta, and the fields of Forel. Further but weaker labeling occurred in the medial septal nucleus, diagonal band of Broca, olfactory tubercle, paraventricular, anterior, mediodorsal, and central lateral thalamic nuclei, lateral habenula, ventral tegmental area of Tsai, interpeduncular nucleus, parabrachial, raphe, dorsal tegmental nucleus and the locus caeruleus. Cortically, prefrontal, insular, entorhinal, prepiriform, and periamygdaloid areas of both species showed considerable labeling as well as the whole temporal lobe of the monkeys used. The perirhinal and basal temporal cortex of all cats showed moderate labeling. In both monkeys and cats, extremely scarce labeling occurred within the cingulate, retrosplenial, and subicular cortex. From an anatomical point of view, the manifold connections of the substantia innominata/basal nucleus of Meynert found in this study underscore the participation of these nuclear groups in motivational, emotional, and cognitive (e.g. mnemonic) functions. Considering the widespread cortical efferents of this complex, it is suggested that the substantia innominata/nucleus basalis of Meynert serves the transmission of information arising within the limbic system to the whole neocortex.

Afferent Pathways↗

PubMed1985

Cortical and subcortical afferent connections of the primate's temporal pole: a study of rhesus monkeys, squirrel monkeys, and marmosets.

The afferent connections of the primate's temporopolar cortex were investigated with the retrograde horseradish peroxidase technique. Old World and New World monkeys received small unilateral injections of horseradish peroxidase. These labeled cells in a number of cortical, thalamic, and brainstem regions and in a few further telencephalic and diencephalic regions. Cortically, the neighboring areas of the inferior and superior temporal gyrus and the insula contained a considerable number of labeled cells. Furthermore, a substantial projection arose from the orbitofrontal and the frontopolar cortex. The cingulate gyrus contained only very few labeled cells. Interhemispherically, corticocortical connections arose mainly from temporal lobe areas. Labeled cells were seen in various regions of the basal forebrain and cells labeled only faintly in the lateral and basal accessory nuclei of the amygdala. The claustrum contained labeled neurons only in one rhesus monkey. On the diencephalic level, the caudal medial portion of the medial pulvinar was the principal thalamic source of afferents to the temporopolar cortex. Furthermore, labeled cells were found in the neighboring, caudal part of the mediodorsal nucleus, within and along the nucleus limitans, in the medial geniculate nucleus, and in several nuclei of the nonspecific system. The fields of Forel, the zona incerta, and lateral and dorsomedial hypothalamic areas contained a few labeled cells. Within the brainstem of the rhesus monkeys those regions projecting diffusely to the cortex contained a few labeled neurons. Furthermore, these brains had some labeled cells in the regions of the nuclei medialis annuli aqueductus, tractus mesencephalicus nervi trigemini, and trochlearis. Although among the three species differences in the cortical and thalamic projection patterns were observed, the regions projecting most densely to the temporal pole were similar in principle. This statement holds in particular for cortical and thalamic sites. However, the greatest number of labeled cells was found in the rhesus monkey, a fact that cannot be attributed solely to the size of the horseradish peroxidase injections and the size of the brain, but that appears rather to represent a true species difference. From our results we conclude that the temporopolar cortex constitutes a cortical area necessary for effective affectional-sensory integration.

Afferent Pathways↗

PubMed1985

Combined lesions of septum, amygdala, hippocampus, anterior thalamus, mamillary bodies and cingulate and subicular cortex fail to impair the acquisition of complex learning tasks.

Previous investigations (Irle and Markowitsch 1982a, 1983, 1984) demonstrated that triple or fourfold lesions within the cat's limbic system fail to produce learning impairments, as opposed to lesions of single or double loci, when tasks of visual reversal, delayed alternation, and active two-way avoidance were used. On the basis of these results, limbic regions of the cat's brain might be considered unessential for intact learning and mnemonic functions. Therefore, in order to obtain indisputable information on the importance of the limbic system for learning and memory, lesions of nearly all limbic core regions of the cat were performed. Ten cats received lesions of seven limbic core regions: the septum, amygdala, anterior thalamus, mamillary bodies, cingulate cortex, subicular cortex, and the hippocampus proper. Nine of these animals were tested postoperatively in the acquisition of a visual reversal task, a spatial alternation and delayed alternation task, and an active two-way avoidance task, and were then compared to the performance levels of ten control animals. The experimental animals turned out to be unimpaired in all tasks tested; the performance scores in the visual reversal and delayed alternation task and - for some experimental animals - in the active two-way avoidance task even indicate a slight, though statistically insignificant, facilitation in the learning behavior of these animals. It is assumed that the learning functions underlying the tasks used were taken over by other brain regions, which, prior to massive limbic lesions, may be suppressed or otherwise inhibited. Alternatively, utilization of spared tissue in the damaged limbic regions must be considered as the possible explanation.

Amygdala↗

PubMed1984

Afferents to the ventral tegmental nucleus of Gudden in the mouse, rat, and cat.

Afferents to the ventral tegmental nucleus of Gudden (VT) were investigated in mice, rats, and cats. Unilateral and bilateral injections or iontophoretical applications of horseradish peroxidase (HRP) were made into the region of the VT. The entire cerebrum was then screened for labeled neurons. Following injections situated principally within the VT, in all three species many retrogradely labeled neurons were observed in the mamillary bodies and the lateral habenular nuclei. Fewer labeled cells were observed in the prefrontal cortex, the basal forebrain, various hypothalamic nuclei, the interpeduncular nucleus, nucleus of the posterior commissure, nucleus of Darkschewitsch and interstitial nucleus of Cajal, vestibular nucleus, and nucleus praepositus hypoglossi. Scant but consistent labeling occurred in the cingular, retrosplenial, and insular cortices, within the medial forebrain bundle, fields of Forel, zona incerta, ventral tegmental area of Tsai, substantia nigra, pretectal area, periaqueductal gray, dorsal tegmental nucleus, locus ceruleus, and raphe complex. Our results show a high similarity in the distribution of afferent connections converging on the VT of mice, rats, and cats. They indicate furthermore that the VT is reached by a variety of cortical and subcortical afferents, which belong either to the limbic system or to brain stem regions related to motor, sensory, and autonomic functions. It is suggested that the VT subserves as a midbrain core structure of the limbic system, which is responsible for the transfer of motor, sensory, and autonomic informations arising within the brain stem to limbic forebrain structures.

Animals↗

PubMed1984

Claustral efferents to the cat's limbic cortex studied with retrograde and anterograde tracing techniques.

The claustral projections to the cat's limbic cortex were investigated with horseradish peroxidase retrograde tracing technique and with autoradiography. Autoradiographic injections covered small portions of either the dorsal anterior claustrum or intermediate to posterior regions of the claustrum. Injections of horseradish peroxidase were made into the subicular, insular, entorhinal, prepiriform, cingulate, retrosplenial and prefrontal cortex. Both methods revealed fully consistent data for substantial claustral efferents to the cingulate, retrosplenial, entorhinal and subicular cortex. For the prepiriform cortex claustral efferents could be established unequivocally only with the horseradish peroxidase technique. Only a rather minor projection could be traced for the claustro-insular projection. Unilateral injections of horseradish peroxidase revealed the existence of a minor number of labeled claustral cells in the contralateral hemisphere for all loci except insular and prepiriform ones. Our data show that claustral cells reach the majority of the allocortical areas of the brain. They thereby confirm the view that the claustrum projects to most regions of the cortex and furthermore that a certain kind of topography exists in the claustro-cortical afferents with a minor number of claustral cells sending afferents to the contralateral cortical hemisphere. In addition, our data reveal that the distribution of claustro-cortical afferents is uneven and that the ventral claustrum (or nucleus endopiriformis) sends fibers to more cortical regions than previously assumed. It is suggested that the claustrum participates in the integration of sensory, motivational, emotional and mnemonic information via its reciprocal claustro-neocortical and its claustro-limbic connections.

Animals↗

PubMed1984

The prefrontal cortex of a prosimian (Galago senegalensis) is reached by efferent neurons originating in the nucleus basalis of Meynert.

Efferent projections from the basal forebrain to the prefrontal cortex of the lesser bush baby (Galago senegalensis) were traced with the retrograde horseradish peroxidase technique. Different areas of the prefrontal cortex of six bush babies were injected with small amounts of horseradish peroxidase. The entire basal forebrain was then screened for labeled neurons. Following all six injections, many retrogradely labeled neurons could be detected in the nucleus basalis of Meynert. These results indicate a strong innervation of the bush baby's prefrontal cortex by the nucleus basalis of Meynert. The observed projections seem comparable in strength and topography to those found in another primate species, the rhesus monkey. Anatomical and functional implications of these projections in the bush baby are discussed and related to findings in other primates and species of other orders.

Animals↗

PubMed1984

Basal forebrain efferents reach the whole cerebral cortex of the cat.

Efferent projections from the basal forebrain to the cat's cerebral cortex were traced with the retrograde horseradish peroxidase technique. Different areas of the cerebral cortex of 51 cats were injected with small amounts of horseradish peroxidase. The entire basal forebrain was screened for labeled neurons. Following all injections, retrogradely labeled neurons could be detected in either the medial septum, or the vertical and horizontal limb of the diagonal band of Broca, or the substantia innominata, or in several of these structures. All three basal forebrain structures project heavily to allocortical regions, but only weakly to neocortical regions. An exception is the medial prefrontal cortex which is densily innervated by the substantia innominata (i.e., comparably dense as allocortical regions are innervated by the substantia innominata). Large injections into he basal temporal cortex (including the perirhinal cortex) and into the insular cortex also led to a considerable number of labeled cells in the substantia innominata. The results indicate a widespread innervation of the cat's cerebral cortex by the basal forebrain. This diffuse projection to the cortex has recently been found also in monkeys and rats. Anatomical and functional implications of these projections in the cat are discussed and related to findings in other species.

Animals↗

PubMed1984

Differential effects of prefrontal lesions and combined prefrontal and limbic lesions on subsequent learning performance in the cat.

On the basis of a previous experiment (Irle & Markowitsch, 1983) in which triple limbic lesions as opposed to double limbic lesions in the cat failed to impair the learning behavior of these animals, the effects of a lesion in a fourth brain structure, in addition to the original ones, were examined. Two groups of cats were given lesions in either the prefrontal cortex alone or in the prefrontal cortex, the anterior thalamus, the mamillary bodies, and the subiculum and subsequently tested in the acquisition of a visual reversal, a delayed alternation, and an active two-way avoidance task. Compared with control cats, cats with prefrontal lesions were strongly impaired in the acquisition of the visual reversal task and the delayed alternation task but only slightly impaired in the acquisition of the active two-way avoidance task. In contrast, animals with combined prefrontal cortical, anterior thalamic, mamillary, and subicular lesions were unimpaired in the acquisition of the visual reversal task, slightly facilitated in the acquisition of the active two-way avoidance task, but impaired in the acquisition of the delayed alternation task similarly to the animals with prefrontal lesions. The superior performance rates of the animals with fourfold lesions are considered to be due to a lesion-induced functional shift acting on intact brain structures which, prior to massive limbic lesions, remain inhibited or otherwise suppressed. The failure of the animals with fourfold lesions in the delayed alternation task indicates that the functions underlying this type of behavior cannot be compensated for or, alternatively, that a prefrontal lesion is not sufficient to disinhibit other structures involved in the same behavior.

Animals↗

PubMed1984

Cortical and subcortical, including sensory-related, afferents to the thalamic mediodorsal nucleus of the cat.

Cortical and subcortical afferents to the cat's thalamic mediodorsal nucleus (MD) were investigated using the method of retrograde transport of horseradish peroxidase (HRP). HRP was applied using vertical or oblique approaches and either a microsyringe or implanted pipettes filled with HRP-powder. A wide variety of cortical afferents to MD was detected: Aside from afferents from the cat's classical prefrontal cortex (gyri proreus, rectus, frontalis), from adjacent areas of the premotor and cingulate cortex and from portions of the insular cortex, afferents were found from cortical areas related to the processing of somatosensory, gustatory, auditory and visual information and from portions of the parietal and temporal association cortex. A considerable number of afferents arose from the diagonal band of Broca and a small number from the precommissural septum, periamygdaloid , prepiriform , entorhinal, subicular and amygdalar regions. The preoptic region and hypothalamic areas contained some labeled cells. All brains, with the exception of one with a very small dorsomedial injection, contained labeled cells in the mamillary bodies. The reticular nuclear complex and the ventral lateral geniculate nucleus were the main sources of afferents on the thalamic level. In the brain stem the substantia nigra, the ventral tegmental area, the deep layers of the superior colliculus, pretectal and tegmental regions contained labeled cells. These results show that MD receives afferents from a large variety of structures. Among them are several cortical as well as subcortical regions related to the processing of sensory and motor information. Taken together, these connections and the numerous afferents to MD from regions related to emotional and motivational behavior confirm the view that MD has to be termed association nucleus.

Afferent Pathways↗

PubMed1983

Widespread neuroanatomical damage and learning deficits following chronic alcohol consumption or vitamin-B1 (thiamine) deficiency in rats.

Consequences of long-term consumption of alcohol (20 months) and of pyrithiamine-induced blockade of vitamin-B1-uptake on the shape of individual brain structures and on the acquisition of two learning tasks have been investigated in 3 groups of rats (alcohol group, AL; thiamine-deficient group, TH; control group, CG). Groups AL and TH wee allowed an 8, or 3 week recovery period, respectively, with normal food and water available ad libitum before behavioral testing started. This consisted of training an active two-way avoidance task and a spatial reversal task. Rats of both experimental groups were, compared to rats of the control group, significantly impaired in acquiring the avoidance task and in acquiring the original discrimination of the spatial reversal task. No differences were found among the two experimental groups. Histological and microscopical examinations of the brains of the rats with a history of thiamine-deficiency or of chronic alcohol consumption revealed a variety of severely affected brain areas. In both groups hippocampal and cerebellar damage was prominent. Furthermore, the mamillary nuclei, certain brainstem regions situated around the ventricles and a few cortical areas contained loss or damage of neurons. It is concluded that the anatomical changes, especially, can be related to those seen in chronic alcoholics and that consequently animal models can be established to investigate in detail the multiple interactions of alcohol consumption, thiamine deficiency, brain damage and behavioral deterioration.

Alcohol Drinking↗

PubMed1983

Differential effects of double and triple lesions of the cat's limbic system on subsequent learning behavior.

On the basis of recent anatomical experiments in which it was found that the anterior thalamus, the subicular cortex, and the mamillary bodies are directly and strongly interconnected, lesions were made in different combinations of two or all three of these regions in four groups of cats. These found groups and a control group were then subjected to two learning tasks: a visual reversal and an active two-way avoidance task. Compared with cats of the control group, cats with lesions of the anterior thalamus and the mamillary bodies (Group AT/MM), of the anterior thalamus and the subiculum (Group AT/SUB), or of the mamillary bodies and the subiculum (Group MM/SUB) were strongly impaired in acquiring the reversal task, whereas cats with lesions of all three structures together (Group AT/MM/SUB) were unimpaired. Similarly, in the active avoidance task, two of the three groups with double lesions (MM/SUB; AT/SUB) were imparied, but cats of Groups AT/MM and AT/MM/SUB were not, compared with the control group. Consideration is made that lesion-induced shifts possibly act upon intact cortical and/or thalamic structures that, prior to massive limbic lesions, remained inhibited or otherwise suppressed. It is assumed the influence of one of the three core regions of the modified Papez-circuit to be sufficient for inhibiting the action of such structures which following a complete lesion of the system may control essential parts of the behaviors tested.

Animals↗

PubMed1982

The thalamic mediodorsal nucleus receives input from thalamic and cortical regions related to vision.

The mediodorsal nucleus of the thalamus (MD) so far has been regarded as being not closely connected to visual regions. Based on the method of retrograde transport of horseradish peroxidase, direct efferents to the cat's mediodorsal nucleus were demonstrated from two visual regions: from the ventral lateral geniculate nucleus and from parts of the visually responsive cortex. These projections were obtained following injections which covered most of MD, but also following injections which were restricted to medial or lateral parts and to the anterior two-thirds or merely to the center of MD. Projections from the ventral lateral geniculate nucleus arose mainly from its caudal portion; projections from the visually responsive cortex originated predominantly in area 20a, but labeled cells were also occasionally detected in areas 18 and 19.

Animals↗

PubMed1982

Connections of the hippocampal formation, mamillary bodies, anterior thalamus and cingulate cortex. A retrograde study using horseradish peroxidase in the cat.

The afferent projections to, and the interconnections between, four structures of the so-called limbic system were investigated in the cat. The retrograde horseradish peroxidase (HRP) technique was used to trace the origins of fibers projecting to each of these four loci. Particular emphasis was laid on tracing cortical afferents of these regions. Four injections were performed in the dorsal and two in the ventral subicular regions; six were centered within the mamillary nuclei, four within the anterior thalamic nuclei, and three within the cingulate gyrus. For each region, a number of projections were found which had apparently not been described before, at least not for the cat: For injections into the subicular regions, a hitherto unknown number of cortical afferents was detected, including labeled cells in the prefrontal and premotor fields and from large areas within the posterior parietal, temporal and occipital cortex (i.e., sensory and sensory integration cortex); numerous neurons were labeled in the anterior nuclear group of the thalamus. Injections of HRP into the mamillary nuclei revealed, aside from a strong projection from the subicular regions, frontocortical and cingulate projections to the mamillary nuclei; the mamillary nuclei also received subcortical projections from the septum, the diagonal band of Broca and from the periaqueductal gray. Following injections into the anterior thalamic nuclei, labeled cells were found in the prefrontal cortex, and to a lesser extent in lateral parts of the cortical hemisphere; subcortically, the mamillary nuclei received connections from hypothalamic areas, the periaqueductal gray, the diagonal band of Broca and the claustrum. Cingulate injections labeled cells in temporal and parietal cortical areas, in the subicular region, and also in the periaqueductal gray. Our findings reveal that each of the four injected areas receives a large number of afferents from divergent regions of the brain; of these, a considerable number is shared by each of the four injection loci. Furthermore, the present results reveal that the subiculum, the mamillary bodies, and the anterior thalamus are more strongly interconnected than previously assumed.

Afferent Pathways↗

PubMed1982

Thiamine deficiency in the cat leads to severe learning deficits and to widespread neuroanatomical damage.

Behavioral and neuroanatomical consequences of a thiamine-deficient diet, combined with the application of a thiamine-antagonist (pyrithiamine) were investigated in the cat. Eight cats (the experimental group) were subjected to a vitamin-B1-poor diet until they developed neurological symptoms (epileptic attacks, ataxia, gait disturbances), while 24 cats were fed normally and served as control group. Immediately following the appearance of neurological signs, a high dose of thiamine was given to the cats of the experimental group; they were then allowed to recover for ten days. Thereafter the performance in learning an alternation task in a T-maze was tested and compared with that of the control group. Behaviorally, the cats of the experimental group manifested drastically retarded acquisition rates in the learning task compared to the cats of the control group. Neuroanatomically, damage was found in the brains of each of the cats in the experimental group; this damage consisted mainly of enlarged ventricles, hemorrhages, neuronal loss and gliosis. Those regions most consistently affected were the periaqueductal gray, the inferior colliculi and the mamillary nuclei. The thalamic mediodorsal nucleus was affected to a minor degree in three cats only. Four cats manifested damage in the hippocampal formation. No damage was found in the cerebellum. Most of the damaged neuroanatomical loci resemble those found in patients with a Wernicke-Korsakoff syndrome.

Animals↗

PubMed1982

Single and combined lesions of the cats thalamic mediodorsal nucleus and the mamillary bodies lead to severe deficits in the acquisition of an alternation task.

The acquisition of a spatial alternation task was tested in five groups of adult cats. Two groups were used for control; one of them consisted of nonlesioned cats, the other of cats with chemical lesions (ibotenic acid) of the ventral tegmental area. The other three groups of cats received chemical lesions of the mediodorsal nucleus of the thalamus, the mamillary bodies, or of both structures together. Cats with lesions of the ventral tegmental area were non-significantly impaired in comparison to non-lesioned cats in the acquisition of the task. Cats with lesions of the mediodorsal nucleus, the mamillary bodies, or with combined lesions of both structures were significantly impaired, compared to the two control groups; among each other, however, their performance rates were similar. As none of the cats with single or combined lesions of the mamillary and the mediodorsal nuclei manifested observable abnormalities with respect to motor, motivational, or emotional behavior during their testing period, it is concluded that their--compared to the other two groups--inferior performance was due to a memory defect. As all three kinds of lesions resulted in a similar defect, it is suggested that the mamillary and the mediodorsal nuclei transmit information to one or more common target area(s), which is (are) dependent on information from either nucleus to operate effectively.

Animals↗

PubMed1982

Widespread cortical projections of the hippocampal formation in the cat.

Efferent projections from the hippocampal formation to the cat's cortex were traced with the retrograde horseradish peroxidase technique. Different areas of the cortex of 31 cats were injected with small amounts of horseradish peroxidase. All subregions of the hippocampal formation were screened for labeled cells. It was found that, with the exception of the entorhinal injections, only subicular areas of the hippocampal formation contain labeled neurons. When HRP was injected into the entorhinal cortex, labeled cells are also found in the hippocampus proper. The most dense projection from the subicular cortex is directed to the medial part of the cortical hemisphere. Here, cingulate, retrosplenial and medial prefrontal fields receive a substantial number of subicular efferents. Furthermore, the entorhinal cortex is reached by a number of axons originating in the subicular area. Scarce projections from the subicular cortex terminate in the dorsal prefrontal, temporal, parietal and prepiriform cortex. It is suggested that the projection from the subicular cortex to the neocortical areas of the frontal pole (medial prefrontal cortex) is of special importance as it may constitute a link between the association areas of the neocortex and those regions of the limbic system thought to play a role in memory (subicular cortex, mamillary bodies, anterior thalamus, cingulate gyrus).

Animals↗