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At least 19 recordsLinked to original sources

PubMedDate not supplied

The topographic organization of hypothalamic and brain stem projections to the hippocampus.

Direct projections primarily ipsilateral to hippocampus from medial septal, diagonal band, supramammillary, submammillothalamic, locus coeruleus, and dorsal and medianus raphe nuclei were demonstrated. The locus coeruleus projects primarily through the cingulum and fornix superior to the dorsal posterior hippocampus, with its terminal fields in the stratum lacunosum moleculare of the subiculum and areas CA 1-CA 2 of the dorsal posterior hippocampus. LC projections to the granular layer of the dentate hilus were not found. Raphe nuclei project through the cingulum, fornix superior, and primarily the fimbria, to the dorsal and ventral posterior hippocampus, with their terminal fields in the stratum lacunosum moleculare of the dorsal posterior subicular region, stratum radiatum of CA 1-CA 3 in the dorsal hippocampus, and the stratum polymorph of the dentate gyrus, primarily in its superficial part. Raphe projections to the anterior hippocampal rudiment were found. However, no projection was found to the subiculum of the ventral posterior hippocampus, nor to stratum oriens. Hypothalamic nuclei project through the fornix superior and the fimbria, mainly to the dorsal posterior hippocampus with abundant terminal fibers in the depth of the dentate hilus. Smaller cells in these hypothalamic nuclei appear projecting to the ventral hippocampus. The number of neurons in the entorhinal area, the diagonal band, and the hypothalamic nuclei projecting to the hippocampus suggests these groups as the main sources of the extrinsic hippocampal afferents. In addition, they may also serve as relay stations for inputs from more caudal nuclei, and the topographic organization of their terminal fields as described herein may have important functional implications.

Animals↗

PubMed1979

The development of the hippocampus and dentate gyrus in normal and reeler mice.

The histogenesis, the time of origin and the pattern of migration of the cells in the hippocampus and dentate gyrus, have been studied in normal and reeler mice. The earliest indication of a defect in the reeler hippocampus is seen on the fifteenth embryonic day (E15) which is at least 24 hours after the first indication of a defect in the neocortex. It is not until E18, that the dentate gyrus shows signs of its incipient abnormality. It appears then, that in both the hippocampus and the dentate gyrus the gene defect first manifests itself at the stage at which the definitive cellular layers are assembled. Experiments involving the injection of 3H-thymidine (3H-TdR) at different developmental stages have confirmed that the site and rate of cellular proliferation in the reeler hippocampus and dentate gyrus are normal, as is the initial pattern of cell migration. However, in the reeler dentate gyrus, most postnatal cell proliferation occurs ectopically and in the hippocampus the normal "inside-out" sequence of neurogenesis is reversed, the earliest pyramidal cells generated coming to lie superficially within the stratum pyramidale and the later formed cells being added at progressively deeper levels. There is no discernible gradient in the time of origin of the granule cells in the radial dimension of the reeler dentate gyrus, whereas there is an obvious "outside-in" gradient in the normal animal. The characteristic gradients in cell proliferation seen in the transverse and longitudinal dimensions of the normal dentate gyrus are, however, also evident in the reeler mouse. Taken together, these observations suggest that the reeler gene exerts its effect on neuronal position only in the radial dimension, and does so at a stage of development subsequent to the proliferation and initial migration of the relevant neurons. Timm's sulfide silver preparations indicate that the characteristic staining patterns seen in the dentate gyrus and hippocampus appear at the same time, and mature at the same rate in normal and reeler mice.

Animals↗

PubMed1977

Modulation of the proestrous surge of luteinizing hormone by electrochemical stimulation of the amygdala and hippocampus in the unanesthetized rat.

The roles played by the amygdala and hippocampus in controlling the release of pituitary luteinizing hormone (LH) were studied in the freely moving rat. Monopolar stainless steel electrodes were implanted into the corticomedial (CM) amygdala, basolateral (BL) amygdala and dorsal hippocampus of female rats. When the animal had recovered from surgery and shown two consecutive 4-day estrous cycles, a chronic atrial cannula was introduced during the afternoon of diestrus II. On the following day (proestrus) electrochemical stimulation (ECS) was applied (20--50 micronA anodal DC 120 sec) bilaterally to the amygdala or hippocampus and blood samples were taken every 90 min from 12.00 to 21.00 h for radioimmunoassay (RIA) of LH. Next day, uterine tubes were examined for ova as evidence of ovulation. ECS of the amygdala exerted two divergent influences on LH release. Stimulation of the BL amygdala at 13.45 h, just before the critical period (14.00--16.00 h), was effective in delaying and reducing the LH surge, whereas ECS of the CM amygdala at 12.00 h resulted in an early synchronization in the timing of the LH curves. All of the rats in both groups ovulated, in contrast to the results of applying ECS to the dorsal hippocampus; there the LH surge and ovulation were completely blocked in 7 out of 9 rats. Thus, in the freely moving rat, the hippocampus can exert a potent inhibitory influence on LH release whereas the amygdala plays a modulatory role in the process.

Amygdala↗

PubMed1979

Effect of thyroid deficiency on the growth of the hippocampus in the rat. A combined biochemical and morphological study.

The growth of the hippocampus was studied in normal and hypothyroid rats using both biochemical and morphological techniques, and the results were compared with observations on the whole forebrain or on the cerebral cortex. The longitudinal growth, area and the volume of the hippocampus was severely reduced in thyroid deficiency. In the cerebral cortex the longitudinal growth and some of the parameters of transverse development were significantly decreased at the rostral but not at the caudal level. On rehabilitation from day 35 to 160 the longitudinal growth remained decreased in both the brain parts while the transverse growth was restored to normal in the cerebral cortex but not in the hippocampus. In the normal hippocampus about 60% of the cells were formed during the first 3 postnatal weeks. This developmental increase was significantly depressed in hypothyroid rats; the final deficit in cell number was about 13%. The rate of cell acquisition was calculated from the slopes of the logistic curves fitted to the data of DNA content. At the age of maximal cell acquisition (at day 2-3) the daily deposition was 0.44x106 cells in controls and 0.34x106 cells in the hypothyroid rats. In controls the concentration of DNA decreased in the hippocampus during maturation. Thyroid deficiency did not influence this developmental trend. In contrast, a severe reduction was observed in the cellular composition of RNA and protein.

Animals↗

PubMed1975

Histochemistry of trauma after electrode implantation and stimulation in the hippocampus.

Electrodes were implanted into the rat hippocampus in both hemispheres for increasing periods of up to 60 days, and the effects of trauma and electrical stimulation of enzymes controlling cell metabolism in the region of implantation were examined and assessed in relation to studies on humans. In the unstimulated hippocampus as a control, enzyme changes were mainly confined to a narrow area of tissue damage surrounding the electrode. The enzyme changes in response to trauma varied widely; some enzymes controlling tissue respiration showed early and rapid changes, increasing in hyperactive, swollen glial cells and vascular endothelium and decreasing in nerve cells and neuropile. Acid phosphatase activity also increased rapidly in glial cells; other phosphate-releasing enzymes increased more gradually with time. A turning point in these chages was apparent between 25 and 40 days, followed by a reversion to more normal levels at 60 days. Electrical stimulation of the hippocampus in the contralateral hemisphere produced no detectable enzyme changes from those of the unstimulated hippocampus.

Acetylcholinesterase↗

PubMed1979

The morphology of the hippocampus and dentate gyrus in normal and reeler mice.

The morphology of the hippocampus and dentate gyrus in normal and reeler mice has been studied in Nissl, myelin, Golgi, Timm's sulfide silver and gold chloride-sublimate preparations. It is evident from both cell-and fiber-stained sections that despite the obvious defect in the positioning of the hippocampal pyramidal and dentate granule cells in the reeler mouse within the radial dimension, the hippocampal formation as a whole shows a normal and consistent progression of cytoarchitectonic fields along its transverse axis, and a normal and consistent progression of changes in the structure of the hippocampus and dentate gyrus along their longitudinal axes. Thus, at least in these structures, the reeler gene seems to exert its effect only in the radial dimension. Cell counts in the area dentata indicate that the number of dentate granule cells in the reeler mouse is reduced compared to that found in normal or heterozygous animals. Although it has been known for some time that the number of granule cells in the reeler cerebellar cortex is markedly reduced, this appears to be the first evidence for a reduction in cell number in a forebrain structure. All the major cell types normally found in the hippocampus and the dentate gyrus are recognizable in Golgi-stained preparations from the brains of reeler mutants. However, in both regions there are a number of abnormalities in the appearance of the cells which seem to be related to the cellular ectopia. Thus, whereas most of the pyramidal and granule cells which attain a normal position in the mutant usually have normal, or near-normal dendritic arbors, the dendrites of nearly all ectopic cells are severely distorted, both in their orientation and general configuration. In preparations stained by the Timm's sulfide silver technique it is evident that the general lamination pattern seen in normal mice is retained in the reeler hippocampus and dentate gyrus despite the gross malpositioning of many of the relevant neurons. However, although the overall laminar arrangement is preserved, there are some fairly consistent abnormalities; for example, the normal trilaminar staining pattern seen in the stratum moleculare of the dentate gyrus is replaced in the reeler by a bilaminar pattern. In gold chloride-sublimate impregnated preparations there is no obvious alignment of the astrocytes in the stratum moleculare of the dentate gyrus in either normal or reeler mice. Moreover, the distribution of the astrocytes within this zone is fairly normal in the reeler mouse, although, in general, these cells appear to be more consistently stellate in form than in normal animals.

Animals↗

PubMed1979

The organization of certain afferents to the hippocampus and dentate gyrus in normal and reeler mice.

The organization of certain of the major afferents to the hippocampus and dentate gyrus has been studied in normal and reeler mutant mice using the autoradiographic and the anterograde degeneration methods. The distribution of the hippocampal and dentate afferents which arise in the medial and lateral parts of the entorhinal cortex and the hippocampus of both sides, has been found to be generally similar to that previously described in the rat, but there are a few minor differences that are discussed in the text. Despite the marked ectopia of many of the neurons in the hippocampal formation in the reeler mouse, the principal afferents to the hippocampus and the dentate gyrus maintain many of the features seen in normal mice. In particular, they maintain a normal radial sequence and a characteristic laminated and complementary arrangement. However, there are a number of significant differences in their distribution; for example, in the reeler mouse, the entorhinal afferents occupy the entire radial extent of the stratum moleculare of the dentate gyrus, whereas in normal mice they are restricted to the outer four-fifths of this layer. Furthermore, in the mutant the commissural and associational afferents to the dentate gyrus do not occupy the inner one-fifth of the molecular layer (as they do in normal animals) but rather are spread throughout the zone containing granule cells, which includes both the poorly-defined stratum granulosum and most of the hilar region of the dentate gyrus. Some of the developmental and functional implications of these and other abnormalities in the organization of the afferents to the hippocampus and dentate gyrus are discussed.

Animals↗

PubMedDate not supplied

The hippocampus and stress induced 17-OHCS elevations.

The physiologic contribution of the limbic brain to emotionally induced stress is still poorly understood. The present study is designed to more specifically evaluate the role of the hippocampus in stress induced plasma 17-OHCS elevations. The conditional reflex to a sequential presentation of tone and shock was used as the stress agent in adult mongrel dogs. Plasma 17-OHCS levels were determined by the Porter-Silber method. Control and stress levels of 17-OHCS were determined before and after unilateral (left) hippocampectomy, and subsequent contralateral (right) hippocampectomy. A unilateral posterior hippocampal lesion partially attenuated (20%) the normal 17-OHCS stress response. In contrast to unilateral lesions, equivalent bilateral posterior hippocampal lesions abolished the normal 17-OHCS stress response. These observations support the thesis that the elevated 17-OHCS levels in response to the conditioning paradigm is dependent on the hippocampus. Furthermore, it is dependent upon the continuity of the hippocampal circuit and not upon the volumetric steroid binding capacity of the hippocampus. These studies also suggest that a unilaterally functioning hippocampus may be adequate to meet the physiologic needs of stress, as reflected by the 17-OHCS response.

11-Hydroxycorticosteroids↗

PubMed1979

The resolution of dopamine and beta 1- and beta 2-adrenergic-sensitive adenylate cyclase activities in homogenates of cat cerebellum, hippocampus and cerebral cortex.

The stimulation of adenylate cyclase by dopamine and various beta-adrenergic agonists has been investigated in homogenates from 3 areas of cat brain: the cerebral cortex, cerebellum and hippocampus. The purpose of the study was to determine whether the beta-arenergic receptors coupled to adenylate cyclase could be classified as either beta 1 and beta 2 subtypes in the different regions studied. The stimulation of adenylate cyclase by the beta-adrenergic agonist, (-)isoproterenol (5 X 10(-6) M), was completely blocked by the specific beta-adrenergic antagonist, (p)alprenolol (1-(-5) M), but not by the dopaminergic antagonist, fluphenazine (10(-5) M), whereas the stimulation of adenylate cyclase by (-)epinephrine (10(-4) M) was blocked to varying extents by these two drugs in each of the 3 regions studied. The (-)epinephrine effect was always blocked in the combined presence of (p)alprenolol and fluphenazine. The adenylate cyclase stimulation by (p)epinephrine which is not blocked by (p)alprenolol was due to interaction of (p)epinephrine with a dopaminergic-sensitive adenylate cyclase which has been characterized in cerebral cortex, hippocampus and cerebellum. Regional differences in the affinity of beta-adrenergic-sensitive adenylate cyclase for various agonists were investigated in the presence of fluphenazine (10(-5) M). In the cerebellum the potency order was (+/-)protokylol greater than (+/-)hydroxybenzylisoproterenol greater than (+/-)isoproterenol greater than (-)epinephrine greater than (+/-)salbutamol greater than (-)norepinephrine, indicating the presence of a beta 2-adrenergic receptor. In the cerebral cortex the potency order was (-)isoproterenol greater than +/-)protokylol greater than (+/-)hydroxybenzylisoproterenol greater than (-)epinephrine = (-)norepinephrine ((+/-)salbutamol being inactive). A similar pattern was found in the hippocampus indicating the presence of a beta 1-adrenergic receptor in these two regions. (+/-)Salbutamol was a partial agonist in the cerebellum and a competitive antagonist in the cerebral cortex. The ratio of the antagonist potencies of (+/-)practolol and (+/-)butoxamine preferential beta 1- and beta 2-adrenergic antagonists respectively, to block the stimulation of adenylate cyclase was 25 in the cerebellum, compared to 0.5 in the cerebral cortex and 1.6 in the hippocampus. These results confirm the presence of a beta 2 subtype of receptor coupled to adenylate cyclase in the former and beta 1 subtypes in the latter two regions. The comparison between the affinities of a series of beta-adrenergic agonists and antagonists for the beta-adrenergic receptors coupled with an adenylate cyclase in cerebral cortex and cerebellum with their affinities for well characterized beta 2-adrenergic receptors in lung and beta 1-adrenergic receptor in heart substantiated this conclusion.

Adenylyl Cyclases↗

PubMed1979

Functional reinnervation of rat hippocampus by locus coeruleus implants.

Transplants of the embryonic locus coeruleus (LC) region were implanted into the circuity of the hippocampal formation in adult rats in which the normal adrenergic afferents to the hippocampus had been removed. The growth of new adrenergic axons from the implant in the denervated hippocampus was followed for 1-14 months after surgery by means of fluorescence histochemistry, and the function of the implant-hippocampal connections was tested electrophysiologically after 2-3 months survival. In the successful cases the entire hippocampal formation was reinnervated from the LC implant within 3-6 months after operation, and the newly formed innervation still persisted unchanged by 14 months. The reinnervation was equally effective irrespective of the route by which the axons entered the hippocampus, i.e. along the lesioned fornix-fimbria or along a retrosplenial route. The pattern formed by the ingrowing LC axons mimicked to a large extent that of the normal LC afferents. Little growth was seen into denervated terminal fields of the commissural, septal or entorhinal afferents, pointing to a preference of the ingrowing LC fibers for the areas normally innervated by adrenergic afferents. In the electrophysiological experiments, stimulation of the LC implants caused (in 20 out of 29 cells monitored) an inhibition of the spontaneous activity of neurons in the host hippocampus. This inhibition had a relatively long latency and a long duration, similar to that observed after stimulation of the innate LC in the intact rat. As in the normal rat, the inhibitory responses were blocked by systemic or local application of the beta-adrenergic receptor blockers propranolol or sotalol. It is concluded that the adult rat brain is capable of carrying out all steps involved in correct functional reinnervation of a denervated region. Moreover, the implant-hippocampal preparation should be a highly suitable model system for functional studies of a central noradrenergic connection.

Adrenergic Fibers↗

PubMed1977

Age-dependent changes in the oxygen consumption of the cerebral cortex, hypothalamus, hippocampus, and amygdaloid in rats.

The oxygen consumption of the cerebral cortex, hypothalamus, hippocampus, and amygdala, of both sexes, ranging in age from 21-805 days for male rats and from 21-780 days for the estrus and diestrus female rats, was measured. The oxidative activity of the hypothalamus, hippocampus, and amygdala decreased rapidly from Day 21 until the 4th mo. and stabilized till the 27th mo. in the hippocampus and amygdala and gradually decreased from the 12th mo. to the 27th mo. in the hypothalamus. The cerebral cortex showed a different pattern which kept a constant level from day 21 to 12 mo. of age. There was no statistically significant change in any of the regions at the time of vaginal opening. Low oxidative activity of the hypothalamus and amygdala in old age was still observed in castrated/hypophysectomized male rats compared with young ones. Therefore, the decreased oxygen consumption in old age seems to be due primarily to changes in the brain tissue itself and not due secondarily to changes in the gonadotropin and sex hormone levels. Female rats had higher oxygen consumption values than males in the cerebral cortex, the hypothalamus, and the hippocampus. In the amygdala the males had a higher consumption. Estrus female rats showed significantly higher oxygen consumption than diestrus females only in the hypothalamus.

Aging↗

PubMed1979

Functional relationships between the hippocampus and the cerebellum: an electrophysiological study of the cat.

1. Functional interrelationships between the hippocampus and the cerebellum have been investigated in the anaesthetized cat. Plots of the stimulating and recording sites as well as the latency range of the responses indicated the extent of ascending and descending lines of operation between these two structures. 2. Stimulation of the fastigial nucleus evoked the discharge of single hippocampal units on both sides of the brain. Early responses had a mean latency of 12 msec and late responses had a mean latency of 21 msec. Increasing the intensity of the stimulus had little effect on the patterns of discharge. 3. There was no topographical organization within the hippocampus. On the other hand, the activity evoked by a cutaneous stimulus was shown to be greatly depressed by a preceding cerebellar stimulus, particularly at intervals 30--40 msec between the two stimuli. 4. Cerebellar responses evoked by stimulating the hippocampus were found mainly in lobule VI of the posterior lobe. Early and late responses were frequently recorded in the same trace, ipsilateral stimulation yielding the shortest latencies. Increasing the intensity of the stimulus increased the likelihood of there being a response and increased the number of spikes in each discharge. Hippocampal stimulation also had a profound influence on resting cerebellar discharges. 5. Symmetrical points in the two hippocampi were chosen for conditioning and testing sequences. The conditioning stimulus had a long-lasting inhibitory effect on the test response followed by a slow recovery. 6. The location and extent of hippocampal influences on the cerebellum were determined by plotting the presence or absence of a response at each stimulated site. The results indicated the existence of bilateral descending projections containing fast and slow components in conformity with the known conduction properties of mossy fibre and climbing fibre inputs. 7. The physiological significance of interrelationship between the hippocampus and the cerebellum is discussed. It seems that there are many similarities as well as fundamental differences in the cerebellar control of movement under normal circumstances and in conditions of stress.

Animals↗

PubMed1977

Stimulation of the hippocampus and its effect on electrographic manifestations of the brain in unrestrained rats.

The dorsal hippocampus was electrically stimulated in unanaesthetized, unrestrained rats with a cobalt-gelatin rod in their cortex. The significance of the hippocampus in the elicitation of both physiological spontaneous rhythmic activity (episodic activity of 8--9/sec frequency bound, in rats, to a state of quiet wakefulness, and "sleep spindles") and pathological rhythmic activity of the self-sustained after-discharge (SSAD) type was determined from the aspect of the EEG and behavioural characteristics. 1. Single electrical pulses (0.1 msec, 1--10 V, 0.3/sec) elicited an evoked potential bilaterally in the somatosensory cortex. Elicitation of rhythmic after-activity (of the type of episodes or sleep spindles) was observed only in some cases in which an adequately strong stimulus was used. 2. Repeated series of rhythmic electrical stimuli following each other at short intervals (2--3 min) led to the formation of SSAD in about one third of the cases and at all stimulation frequencies (3-15/sec), although low frequencies (3--4/sec) were the least effective. The character of the SSAD and simultaneous behavioural phenomena differed fundamentally from those evoked by electrical stimulation of the thalamus (Chocholová et al. 1977). The development of paroxysmal after-activity was signalled by responses of a more or less distinct "recruiting" character during stimulation. On the basis of a comparison of electrographic and behavioural manifestations after electrical stimulation of the thalamus and hippocampus, the possibility of both thalamic and extrathalamic projection from the hippocampus to the cortical region is considered.

Animals↗

PubMedDate not supplied

[Effect of pheprazet and its alkylated analogs on the neuronal populations of the dorsal and ventral portions of the hippocampus].

The action of pheprazet, a derivative of amphethamine, and of the pheprazet alkylated analogues on the excitability of the neuron populations in the dorsal and ventral parts of the hippocampus was studied in non-anesthetized rabbits with electrodes and chemotrodes indwelt in the hippocampus and other brain structures. Most active drugs are shown to be pheprazet and (formula: see text). The former affects the beta- and the latter the alpha-adrenoreceptors of the hippocampus. Pheprazet pre-eminently increases while the drug (see formula: see text) reduces the excitability of the neuron populations in the dorsal and ventral parts of the hippocampus. The opposite effects of these drugs are considered by authors from the standpoint of interaction between different mediator systems.

Amphetamines↗

PubMedDate not supplied

[Role of the hippocampus in conditioned reflex activity].

The role of the hippocampus in animals' conditioned activity was studied in experiments on rats and cats with ablated hippocampus. It was shown that in rats the ablation leads to a statistically significant slowing down in learning of the avoidance reaction. The effect becomes stronger in stress situation. The process of learning and optimization of choice reaction in the maze with alimentary reinforcement if sharply impaired in rats with bilateral ablation of hippocampus. The bilateral ablation of the hippocampus in cats in experiments with choice of the side of the alimentary reinforcement prolonged the latencies and sharply increased the number of erroneous reactions. The obtained data are analyzed in terms of fronto-pallido-hippocampal system, which selects, compares and integrates sensory information at the stage of the afferent synthesis.

Animals↗

PubMedDate not supplied

Interaction of morphine and 5-hydroxytryptamine in the raphe-hippocampus system.

In order to describe the interaction of morphine and 5-hydroxytryptamine (5-HT) in the raphe-hippocampus system we tested the influence on the antinocifensive effect of topic administrations of morphine and serotonergic substances into the dorsal hippocampus and the median raphe nucleus in rats. 5-HT administered into the dorsal hippocampus increased the morphine analgesia. Lysergic acid diethylamide injected into the raphe nucleus antagonized the morphine effect. Morphine given into the raphe nucleus was highly effective, while its injection into the striatum was ineffective. The effect of the intrahippocampal morphine was antagonized by methysergide. The results indicate the important role of the serotonergic raphe-hippocampus system in the mechanism of the morphine analgesia.

Animals↗

PubMed1979

Two types of epileptic cortical after-discharges evoked by the stimulation of the hippocampus and thalamic nuclei in rats.

Rhythmic cortical phenomena were evoked by stimulation of hippocampus and/or thalamus in rats. Electrical stimulation of thalamic nuclei (nc. ventralis dorsomedialis VDM and nc. lateralis anterior--LA) by single pulses elicited rhythmic after-discharge ("spindle") as a late component of the cortical response, whereas identical stimulation of hippocampus did not trigger such an activity. Rhythmic stimulation of thalamic nuclei elicited cortical incremental responses more often than stimulation of hippocampus. Epileptic self-sustained after-discharges (AD) occurred after the endo of rhythmic stimulation in 66% of hippocampal stimulations, in 35% of VDM stimulations and in 30% of LA stimulations. AD evoked by stimulation of the hippocampus (long duration discharges of slow serrated waves) differed characteristically from AD following stimulation of the VMD (short duration spike and wave complexes). Stimulation of the LA in half of the cases led to the "hippocampal" pattern of serrated wave after-discharges, in the remaining cases spike-and-wave complexes or a combined AD pattern was recorded.

Animals↗

PubMed1979

Ischemic lesions of the hippocampus and their relation to Ammon's horn sclerosis. A neuropathological study of two cases and a comparison to the vascular anatomy.

Two adult brains with small ischemic lesions in the hippocampus, due to impairment of the supply from the posterior cerebral artery, are presented. The first case corresponds to what is described in the literature as "incisural sclerosis" and shows no difference in vulnerability between the Sommer and the Spielmeyer sector. In the second case the hippocampal lesion is due to an embolic occlusion of the posterior cerebral artery and consists of selective necrosis of the subiculum, the Sommer sector and part of the endfolium of the pyramidal layer, the Spielmeyer sector remaining noninfarcted. The postmortem angiograms of 12l hippocampi of adults, as well as full term born and premature infants, show that the h1 and h2 sectors and part of the h3 sector of the hippocampus are supplied by the same "sulcus" arteries. Although there is a selective vulnerability to ischemia in some sectors of the hippocampus, which is typical for Ammon's horn sclerosis, this cannot be explained by a difference of arterial supply or by compression of arteries during the process of birth.

Blood Vessels↗