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.

Organization of cortical afferents to the prefrontal cortex in the bush baby (Galago senegalensis).

Cortical afferents to the prefrontal cortex were studied in 10 bush babies (Galago senegalensis) by means of somatopetal transport of horseradish peroxidase. The lateral injections invariably labeled neurons in the temporal cortex and in most cases also in the insular and parietal regions. In some of these brains the cingulate and retrosplenial areas contained labeled perikarya.

Epidural kainate, but not ibotenate, produces lesions in local and distant regions of the brain. A comparison of the intracerebral actions of kainic acid and ibotenic acid.

Epidural placement of ibotenic acid (Ibo) is described as a new technique for easy and successful lesioning of cortical neurons. The method works reliably without apparent damage to passing or underlying fibers and without causing distant lesion effects. In rats, the favorable effects of epidural placement of Ibo on behavior and on neuronal tissue were compared with and found to contrast with those of kainic acid (KA).

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.

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.

Thalamic mediodorsal nucleus and memory: a critical evaluation of studies in animals and man.

Following a general description of the anatomical organization of the thalamic mediodorsal nucleus (MD) of animals and man, the involvement of this nucleus in the processing of memory related information has been evaluated by reviewing stimulation, electrophysiological, and lesion studies in animals, and by reviewing research on induced lesions, degenerative changes and vascular damage of MD in humans. Neither the results from animal experiments nor those from studies on humans provide clear-cut evidence for a specific, memory related role of MD. However, the findings here presented do support the theory that MD is one of several, possible memory related relay stations.

No detectable remote lesions following massive intrastriatal injections of ibotenic acid.

Behavioral and anatomical consequences of particularly large intrastriatal injections of ibotenic acid are described. Only in the rat with the largest injection, which encompassed almost the entire frontal lobe, were enduring aphagia and adipsia observed; epileptic attacks were, however, not detectable in this or in any other of the rats. In spite of the massiveness of the lesion, neither remote lesions nor damage to passing fibers was observed.

Cortico-prefrontal afferents in the guinea pig.

The prefrontal cortex of the guinea pig was investigated in a search for afferents from cortical areas outside the frontal lobe using the horseradish peroxidase retrograde tracing technique. Based on afferents from the medial, the lateral, and from both parts of the thalamic mediodorsal nucleus, three prefrontal subregions were defined, namely the sulcal (within and above the rhinal sulcus), the medial (anterior and superior to the genu of the corpus callosum), and the fronto-polar subfield. Only the fronto-polar region was found to receive afferents from insular, cingulate, retrosplenial, parietal, and temporal cortical fields.

Delayed-alternation performance after kainic acid lesions of the thalamic mediodorsal nucleus and the ventral tegmental area in the rat.

The relative importance of two subcortical structures, projecting to the rat's prefrontal cortex, in mediation of delayed-alternation performance, was tested. These structures, the thalamic mediodorsal nucleus and the ventral tegmental area, were lesioned with kainic acid after the rats had learned a spatial delayed-alternation task. It was found that both structures are apparently involved to a similar degree in the performance of this task and that the behavior of both experimental groups differed from that of a sham-operated control group of rats.

Prefrontal cortex of the mouse defined as cortical projection area of the thalamic mediodorsal nucleus.

In the mouse small amounts of horseradish peroxidase were injected iontophoretically into different portions of the frontal lobe. Out of a large number of mice, 18 with typical injections which together covered most of the anterior half of the cortex were selected, and their retrogradely labeled thalamic cells were described and illustrated in detail. Special emphasis was laid on the cortical projections of the mediodorsal nucleus which were considered to define locus and extent of the prefrontal cortex.

Delayed-alternation performance after selective lesions of the medial and sulcal prefrontal cortex of the guinea pig.

The sulcal or medial subdivision of the prefrontal cortex of the guinea pig was ablated after the animals had learned a spatial delayed-alternation task. Retention of this task was significantly impaired only after ablation of the medial prefrontal cortex. As the most critical cortical region for delayed-alternation performance in the rat is also situated in the medial prefrontal cortex, our findings suggest a close functional correspondence of the prefrontal cortices of these rodent species.

Prefrontal cortex of the guinea pig (Cavia porcellus) defined as cortical projection area of the thalamic mediodorsal nucleus.

The cortical projection area of the thalamic mediodorsal nucleus (MD) was investigated using the horseradish peroxidase technique. Distinct relationships between subdivisions of MD and of the prefrontal cortex were established: the medial sector of MD projects to sulcal cortex dorsal to the rhinal fissure and to the lateral frontopolar region; the lateral sector of MD reaches mainly cortex within the medial part of the hemisphere from the frontopolar region up to a mid corpus callosal level. The projection area of the lateral sector of MD overlaps with the projection fields of the paratenial and anteromedial nuclei.

Widespread cortical projections of the ventral tegmental area and of other brain stem structures in the cat.

Thirty-three cat brains with injections of horseradish peroxidase in various regions of the cerebral cortex were screened for afferent projections from the ventral tegmental area, the locus ceruleus, and the parabrachial nuclei. All three structures were found to project to rather divergent parts of the cortex, including regions in the posterior half of the hemisphere. These results, especially for the ventral tegmental area and, to a lesser degree, for the parabrachial neurons, disagree with most of the target loci of established cortical afferents in the rat.

Delayed-alternation performance after selective lesions within the prefrontal cortex of the cat.

On the basis of new neuroanatomical findings on relationships between subregions of the mediodorsal thalamic nucleus and the prefrontal cortex of the cat, it was attempted to investigate the relative importance of prefrontal subfields with the aim of obtaining evidence in favor of a functional inequality of different prefrontal subfields. Four areas, named presylvian (PRS), proreal (PR), dorsomedial (DM), and orbito-insular (OI) sectors, were ablated successfully in 30 adult animals. Performance of a 10-sec delayed-alternation task was compared pre- and postoperatively.

Kainic acid lesions in the cat's thalamus: morphological and behavioral changes.

Anatomical and behavioral effects of large and of circumscribed kainic acid lesions in the thalamus of the cat are described. Evidence is provided that even "athalamic" preparations seem possible and that cats with destruction of more than two thirds of their thalamus show only transitory disturbance of basic functions (eating, drinking, walking). It is concluded that fiber systems, traversing the thalamus, may be of particular importance for maintaining basic functions.

Prefrontal cortex of the cat: evidence for an additional area.

Direct projections from the mediodorsal nucleus of the thalamus to ventral parts of the insular region of the cat's cortex were demonstrated by using the horseradish peroxidase technique.

Cortical afferents to the prefrontal cortex of the cat: a study with the horseradish peroxidase technique.

Following horseradish peroxidase (HRP) injections into different areas within the prefrontal cortex (PFC) of the cat, labeled neurons were found in the cingulate and insular cortex. These results demonstrate that the cat's prefrontal cortex is reached directly from these cortical regions, and that the observed cortical projections are similar to those detected in the monkey's prefrontal cortex.

Behavioral and anatomical consequences of small intrastriatal injections of kainic acid in the rat.

The effects of bilateral injections of kainic acid into the anteromedial neostriatal region were examined behaviorally and anatomically in two groups of rats. Behaviorally, kainic acid injections resulted in a severe impairment of delayed alternation retention, while the ability for visual discrimination remained unaffected. Anatomically it was found that axons traversing the injected area remain able to transport horseradish peroxidase.

The prefrontal cortex of the cat: anatomical subdivisions based on retrograde labeling of cells in the mediodorsal thalamic nucleus.

Different areas of the frontal cortex of the cat were injected with small amounts of horseradish peroxidase. The region of labeled cells in the mediodorsal nucleus of the thalamus (MD) were related to the injected areas. Distinct relations between subdivisions of MD and of the prefrontal cortex were established: a rather large central sector of MD projects to the gyrus proreus and the anterior parts of the gyri sigmoideus, rectus, and frontalis.

Single unit activity in cat prefrontal and posterior association cortex during performance of spatial reversal tasks .

Relationships between the performance of complex learning tasks and the firing patterns of single unites in prefrontal and posterior association areas of the neocortex were studied in 9 cats. Recording data from 2 additional cats served as controls for sensory and motor aspects of the tasks employed. During recordings, animals sat in a box, their heads fixed to a stereotaxic instrument, and performed a non-sensory spatial reversal or delayed-alternation task by pressing 1 of 2 lateralized retractable levers.