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Biomedical subjects

H J Markowitsch

Publications and source records attributed to H J Markowitsch.

At least 109 records · Page 6Linked to original sources
PubMed1984

Can amnesia be caused by damage of a single brain structure?

The relation of amnesia and damage to some particular brain regions is discussed by reviewing the main findings of selected human case reports. It is argued that frequently a too straightforward and unidimensional interpretation of the relations between brain damage and a behavioral deficit is formulated in such reports. Evidence obtained by modern anatomical techniques as well as the widespread and time-dependent effects of lesions make it necessary to consider a lesion of a particular structure of the brain and correlated mnemonic disturbances as possibly due to an altered equilibrium in an extensive network of the brain. The primary lesion of one or the other specific structure may lead to severe and lasting amnesia or may fail to do so depending on its influence on other brain regions.

Adult↗
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

Different emotional tones significantly affect recognition performance in patients with Korsakoff psychosis.

The performance in reidentifying photographs was measured in alcoholic Korsakoff patients, in non-amnesic alcoholics and in a control group. The photographs showed well-known and unknown faces and buildings and alcoholic and nonalcoholic beverages. A minimum of 15 min elapsed between the end of the original presentation of the series and the beginning of its second presentation within a large number of additional photographs. Korsakoff patients were significantly inferior in number of correctly reidentified items compared to alcoholics who were in turn significantly inferior to the control group. Korsakoff patients manifested the poorest performance in the reidentification of unknown pictures and of nonalcoholic beverages; they showed, however, comparatively good performance in the reidentification of alcoholic beverages and of known faces. Independent of the category of the stimulus material, the Korsakoff patients had low confidence in their responses. It is concluded from these data that the emotional tone of material to be remembered constitutes a major variable for delayed effective retrieval.

Adult↗
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

Different neuropathological effects of intrahippocampal injections of kainic acid and tetanus toxin.

Behavioral and neuroanatomical effects of hippocampal injections of kainic acid (KA) and tetanus toxin (TT) were investigated in rats. Injections of KA resulted in both local and distant neuroanatomical damage, but not in clear signs of epilepsy; injections of TT on the other hand were followed (in some of the rats) by prolonged seizure attacks, but not by neuronal damage. Based on these results it is suggested that the widespread neuronal damage following KA lesions cannot be primarily attributed to orthodromic activation of epileptic discharges. Instead, specific properties of KA and their interactions with certain transmitters may provoke widespread neuroanatomical damage.

Animals↗
PubMed1983

Cortical and thalamic afferent connections of the insular and adjacent cortex of the rat.

Thalamic and cortical afferents to the insular and perirhinal cortex of the rat were investigated. Unilateral injections of horseradish peroxidase (HRP) were made iontophoretically along the rhinal sulcus. HRP injections covered or invaded areas along the rhinal fissure from about the level of the middle cerebral artery to the posterior end of the fissure. The most anterior injection labeled a few cells in the mediodorsal nucleus. More posterior injections labeled neurons in the basal portion of the nucleus ventralis medialis, thus suggesting that this cortical region constitutes the rat's gustatory (insular) cortex. We consider the cortex situated posterior to the gustatory cortex in and above the rhinal sulcus as the core region of the rat's (associative) insular cortex, as this cortex receives afferents from the regions of and between the nuclei suprageniculatus and geniculatus medialis, pars magnocellularis. It includes parts of the cortex termed perirhinal in other studies. The cortex dorsal and posterior to the insular cortex we consider auditory cortex, as it receives afferents from the principal part of the medial geniculate nucleus, and the cortex ventral to the insular cortex (below the fundus of the rhinal sulcus) we consider to constitute the prepiriform cortex, which is athalamic. The posterior part of the perirhinal cortex (area 35) receives afferents from nonspecific thalamic nuclei (midline nuclei). Cortical afferents to the injection loci arise from a number of regions, above all from regions of the medial and sulcal prefrontal cortex. Those injections confined to the projection cortex of the suprageniculate-magnocellular medial geniculate nuclear complex also led to labeling in contralateral prefrontal regions, particularly in area 25 (infralimbic region). A comparison of our results with those on the insular cortex of cats and monkeys suggests that on the basis of thalamocortical connections, topographical relations, and involvements of neurons in information processing and overt behavior, the insular cortex has to be regarded as a heterogeneous region which may be separated into prefrontal insular, gustatory (somatosensory) insular, and associative insular portions.

Afferent Pathways↗
PubMed1983

Transient global amnesia.

The syndrome of transient global amnesia (TGA) is defined and described. Characteristic features, epidemical data, variables possibly provoking TGA, its possible etiology and anatomical basis are reviewed. A transient disturbance in the formation of lasting new memories (usually of less than one day) and a retrograde amnesia (which includes the period of the attack and possibly a short time before) are considered as the main features of TGA. A further trait of TGA is the high age of most of the patients subjected to it (58 years on the average). TGA most likely is based on a transient change in the blood supply of certain regions of the brain. The mechanism by which this change happens is still hypothetical. Regions of the limbic system, in particular the area of the temporal lobe and the hippocampal formation, appear to be affected most likely. Uncertain are: the existence of factors provoking the outbreak of an amnesic attack, the likeliness of multiple episodes of TGA and the neuropsychological alterations in patients who suffered a transient global amnesic attack. The outcome of this review suggests, however, that the incidence of recurrent attacks of TGA is higher than previously assumed and that a transient global amnesic attack may be followed by lasting behavioral deteriorations.

Aged↗
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

Reduced resistance to progressive extinction in senescent rats: a neuroanatomical and behavioral study.

The behavior of senescent rats and mature-young rats was compared in a learning task which consisted of the acquisition of a visual discrimination task, its reversal, the induction of a progressively increasing extinction, relearning and, finally, a complete extinction training. It was found that young and old rats were statistically indistinguishable during all parts of the task, except the progressively increasing extinction. Here, the senescent animals made a significantly higher number of errors than the mature-young ones. Neuroanatomically, ventricular dilation, commissural changes and neuronal loss were observed in senescent rats. The significantly reduced number of neurons in the medial nucleus of the amygdala in old rats compared to young was not directly related to the changed behavior in the progressively increasing extinction part of the visual discrimination task. Based on the anatomical connections of the amygdala and its possible functions in learning and memory, the hypothesis is made that the medial amygdaloid nucleus is involved in the learning of changing response-reinforcement contingencies.

Age Factors↗
PubMed1983

Convergence of basolateral amygdaloid and mediodorsal thalamic projections in different areas of the frontal cortex in the rat.

The extent of convergence of mediodorsal thalamic and amygdalar afferents on the rat's frontal cortex was studied by tracing retrogradely labeled cells following injections of horseradish peroxidase (HRP). HRP was applied iontophoretically in extremely small injections throughout all areas of the frontal cortex. The following organization was revealed: Converging inputs from the mediodorsal nucleus and the amygdala are observed in the posterior parts of the pre- and infralimbic areas, in the posterior half of the dorsal and ventral agranular insular areas and in the lateral and dorsal precentral areas. Both mediodorsal and amygdaloid afferents reach the dorsal tip of the frontal cortex. Only the mediodorsal afferents were found to terminate in the anterior parts of the pre- and infralimbic areas and in the anterior part of the dorsal division of the anterior cingulate area and in the medial precentral area. On the lateral side of the hemisphere the anterior halves of the dorsal and ventral agranular insular areas receive mediodorsal afferents. Amygdaloid, but not mediodorsal afferents, were found following injections into the more posterior parts of the lateral precentral area. These results are discussed with respect to the extent of the prefrontal cortex in the rat and its definability as a target area of subcortical nuclei. Functional aspects of the anatomical convergence of connections within the so-called basolateral limbic circuit are outlined.

Afferent Pathways↗
PubMed1983

Heterotopic interhemispheric cortical connections in the rat.

In the rat, contrary to other species, interhemispheric cortical connections have been considered to travel largely between homotopical regions only. Based on iontophoretic injections of horseradish peroxidase, the present study reports extensive heterotopic interhemispheric connections between posterior insular (perirhinal) regions of the lateral part of the hemisphere and anterior prefrontal regions of the medial hemisphere and vice versa. Generally, the areas connected interhemispherically are also connected intrahemispherically. The ratio of contralateral projections appears to be less than one third of the ipsilateral ones.

Animals↗
PubMed1983

Perseverative effects of parabrachial lesions: a mechanism of reduced activation?

The acquisition of a spatial reversal task and two reversals of it and the acquisition of an active two-way avoidance task were tested in three groups of male Sprague-Dawley rats: two experimental and one control group. The experimental group received chemical lesions of the parabrachial nuclei (group NPB) or of the dorsal hippocampus (group HC), using ibotenic acid. (Ibotenic acid is a compound which, contrary to kainic acid, fails to produce distant lesions, but, in conformity with kainic acid, spares the majority if not all fibers of passage.) The control group (group CG) received injections of the vehicle solution only. Animals of group NPB, in comparison to those of the other two groups, acquired the reversal task more quickly, but in the acquisition of its two reversals they needed considerably more time and made more perseverative errors. Likewise, only group NPB was significantly impaired in the acquisition of the avoidance task. From these results and from available evidence on connections of the parabrachial neurons with regions specifically involved in variables of the tested tasks (such as the prefrontal cortex), it is concluded that the parabrachial region exerts an activating influence on forebrain areas.

Animals↗
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↗
PubMed1983

Afferents from limbic system-related regions to the frontal cortex in the bush baby (Galago senegalensis).

Afferents from limbic system-related structures (aside from the cingulate and retrosplenial cortex) to medial and lateral regions of the bush baby's frontal cortex were investigated by means of the somatopetal transport of horseradish peroxidase. The frontopolar region received afferents from the subicular cortex, the lateral nucleus of the amygdala, from hypothalamic nuclei, the ventral tegmental area and other brain stem nuclei. Injections of horseradish peroxidase into other frontal regions usually resulted in labeled cells in brain stem nuclei and in the hypothalamus, but not in telencephalic regions; only the large injection into the posterior part of the frontal cortex was followed by labeled amygdaloid neurons. From these results it is concluded that a small number of limbic system-related telecephalic areas projects to the frontal cortex and that a somewhat larger number of diencephalic and brain stem nuclei reaches this part of the cortex.

Afferent Pathways↗
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↗