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PubMed1986

Autoradiographic visualization of dopamine D-2 receptors in the monkey brain using the selective benzamide drug [3H]raclopride.

Using the novel substituted benzamide drug [3H]raclopride in combination with in vitro receptor autoradiography, the distribution of dopamine D-2 receptors was studied in the monkey brain. Highest densities of D-2 receptors are present in dopamine-rich areas and the distribution shows the following rank order: caudatus and putamen greater than nucleus accumbens greater than olfactory tubercle greater than substantia nigra (pars compacta) greater than insular cortex greater than piriform and entorhinal cortex greater than substantia nigra (pars reticulata). In all of these areas [3H]raclopride binding was blocked by dopamine (1 microM) and by D-2 receptor antagonists such as (+)-butaclamol, eticlopride and raclopride, while the D-1 receptor antagonist SCH 23390 (1 microM) reduced [3H]raclopride binding by 15-20% in some restricted parts of the caudatus and putamen exclusively.

Animals↗

PubMed1986

Electrical activity generated in subicular and entorhinal cortices after electrical stimulation of the lateral and basolateral amygdala of the rat.

Evoked field potentials and extracellular unitary activity were recorded from entorhinal lateral and subicular ventral cortices under conditions of amygdala stimulation in equithesin-anesthetized rats. The stimulation of the lateral and basolateral nuclei of the amygdaloid complex evoked field potentials consisting of negative-positive waves in layers III-VI and positive-negative deflections in the superficial layers of the ventral subdivision of the entorhinal cortex. The stimulation of the lateral nucleus evoked similar potentials in the dorsal subdivision of this cortex. And the stimulation of the lateral and basolateral nuclei of the amygdala evoked negative-positive field potentials in layer III of the subicular cortex. Cellular activity of the entorhinal and subicular cells evoked by stimulation of the lateral and basolateral nuclei consisted of an excitatory response followed by a prolonged suppression period. This activation coincided with the negative potential recorded in the deeper layers of these cortices. Such observations provide support for amygdaloid projection to the entorhinal and subicular cortices as recent anatomical findings suggested. The functional significance of these observations indicate an amygdaloid influence on entorhinal-hippocampal neurotransmission as well as on the ventral subiculum which provides the major output from the hippocampus.

Amygdala↗

PubMedDate not supplied

Age-dependent cerebral atrophy and cognitive dysfunction in SAMP10 mice.

Findings obtained from a series of studies to characterize age-dependent changes in brain morphology and behavior of inbred SAMP10 mice are reviewed. Following apparently normal development, SAMP10 mice developed brain atrophy with advancing age. The neocortex was diffusely atrophic in aged SAMP10 mice, with the frontal cortex being most affected. The entorhinal cortex, amygdala, and nucleus accumbens were also atrophic. Other subcortical structures were mildly atrophic, but the hippocampus was not atrophic. Mild to moderate hypertrophic astrocytosis was seen in the atrophied regions. Alzheimer's type pathology was not seen. The cortical atrophy was due to both loss and shrinkage of neurons. Brain atrophy was not remarkable in normal aging control SAMR10 mice. In accordance with above morphological changes, SAMP10 mice developed cognitive impairments with advancing age that were demonstrated by poor performance in passive avoidance and conditional avoidance tasks. All of these features of SAMP10 mice were inherited. SAMP10, therefore, is a unique model of age-dependent, inherited cerebral atrophy with cognitive dysfunction.

Aging↗

PubMed1999

Architecture and connections of retrosplenial area 30 in the rhesus monkey (Macaca mulatta).

Because of the sharp curvature of the retrosplenial region around the splenium of the corpus callosum, standard coronal sections are not appropriate for architectonic analysis of its posteroventral part. In the present study, examination of the posteroventral retrosplenial region of the rhesus monkey in sections that were orthogonal to its axis of curvature (and therefore appropriate for architectonic analysis) has permitted definition of its architecture and precise extent. This analysis demonstrated that areas 29 and 30 of the retrosplenial cortex, as well as adjacent area 23 of the posterior cingulate cortex, extend together as an arch around the splenium of the corpus callosum and maintain their topographical relationship with one another throughout their entire course. Injections of anterograde and retrograde tracers confined to retrosplenial area 30 revealed that this area has reciprocal connections with adjacent areas 23, 19 and PGm, with the mid-dorsolateral part of the prefrontal cortex (areas 9, 9/46 and 46), with multimodal area TPO in the superior temporal sulcus, as well as the posterior parahippocampal cortex, the presubiculum and the entorhinal cortex. There are also bidirectional connections with the lateroposterior thalamic nucleus, as well as the laterodorsal and the anteroventral limbic thalamic nuclei. The connectivity of area 30 suggests that it may play a role in working memory processes subserved by the mid-dorsolateral frontal cortex in interaction with the hippocampal system.

Animals↗

PubMed2005

Environmental reduplicative paramnesia in a case of atypical Alzheimer's disease.

A 79-year-old patient with neuropathologically confirmed Alzheimer's disease (AD) presented with a selective environmental reduplicative paramnesia (RP), the belief that one or more environments exist simultaneously in two or more physical locations. Clinical presentation and neuropathological examination revealed an atypical form of AD. High neurofibrillary tangle densities were observed in the frontal and temporal association cortex, whereas the parietal and entorhinal cortex, as well as the hippocampus, were nearly spared. These findings are compared to those reported in frontal and frontotemporal variants of AD and discussed in the light of current anatomoclinical models for environmental RP.

Activities of Daily Living↗

PubMed1990

Ontogenetic development of habit and memory formation in primates.

Lesion studies in adult monkeys have suggested that an experience can enter into memory in two ways: as cognitive information stored in a cortico-limbo-thalamocortical system (involving the higher order sensory areas of cortex, the amygdala, hippocampus, and entorhinal cortex, the medial thalamic nuclei, or ventromedial prefrontal cortex, and the basal forebrain) and as a habit stored perhaps in a cortico-striatal system (involving the sensory cortical areas and the caudate and putamen). Our studies of behavioral development in infant monkeys as well as those in human infants provide complementary evidence by suggesting that these two systems are developmentally dissociable, in that the cognitive memory system, assessed by the delayed non-matching to sample task, appears to mature considerably more slowly than the habit system, assessed by the concurrent visual discrimination task, a notion that has also been discussed recently by others (Nadel & Zola-Morgan, 1984; Rose, 1980). Furthermore, despite the late development of the cortico-limbo-diencephalic memory system, this chapter has presented evidence that some limbic-dependent memory processes, such as those required for success on the visual paired comparison task, develop extremely early. The notion that at least one type of recognition process mediated by the limbic system is present neonatally provides new insight into the normal development of memory processes and indicates the need to identify further the memory processes and substrates that become available to an infant at different time points during maturation. Such studies will help one day to determine the immaturity of structure or function that is responsible for the intriguing phenomenon of infantile amnesia, that is, the inability to recall the stimuli or events experienced in the first few years of life.

Animals↗

PubMed1994

[Cortical projections from the reuniens nucleus of the thalamus in the rat].

Direct projections from the reuniens nucleus to the cerebral cortex were examined using the anterograde tracing method of Phaseolus vulgaris leucoagglutinin (PHA-L) in the rat. The reuniens nucleus was found to project to widespread cortical regions. The labeled fibers from the reuniens nucleus terminated in layers I, III and IV of the frontal cortex including the medial and ventrolateral orbital cortices, the cingulate cortex, and the infralimbic cortex. A few fibers from the nucleus reuniens also terminated in layer I of the agranular insular cortex, the temporal cortex and the parietal cortex. The labeled terminals were also present in the retrosplenial granular and agranular cortical regions of the layer I. The heavy PHA-L labeled fibers terminated in the stratum lacunosum and molecular of field CA1 of Ammon's horn of the hippocampus, and moderately in the subiculum, the presubiculum and the parasubiculum, mainly in the molecular layer. There were also may labeled fibers and terminals in the perirhinal cortex of layer I, the entorhinal cortex of layers I, III-IV and V, and the occipital cortex of layer I. These results indicate that the reuniens nucleus projects to much more widespread regions than previously known.

Animals↗

PubMed1999

Spontaneous activity of the perirhinal cortex in behaving cats.

The perirhinal cortex lies at the interface between the neocortex and allocortex. Whether the perirhinal cortex expresses spontaneous electroencephalographic rhythms that are characteristic of the allocortex and/or of the neocortex is unknown. Thus, the present investigation was undertaken to characterize the activity of the perirhinal cortex with respect to various electroencephalographic rhythms that are displayed by neocortical areas or the entorhino-hippocampal system during different behavioral states of vigilance in chronically-implanted cats. Although perirhinal and neocortical electroencephalograms underwent similar state-dependent changes in amplitude, the ubiquitous neocortical sleep spindles were absent from the perirhinal cortex. In addition, while the slow sleep oscillation (0.5-1 Hz), which is pervasive in the neocortex, was present in the perirhinal cortex, its temporal relation to the neocortical oscillation was highly variable. In contrast, a high degree of correlation was found between perirhinal and entorhinal electroencephalographic activities in all behavioral states. In particular, during waking and paradoxical sleep, multiple simultaneously recorded entorhinal and perirhinal sites displayed an oscillation in the theta range which was highly correlated. To rule out the possibility that the perirhinal theta oscillation reflected volume conduction from neighboring structures, single-unit recordings were performed. Spike-triggered averages and peri-event histograms revealed that perirhinal cells displayed a statistically significant theta-related modulation of their spontaneous activity, albeit weaker than that observed in the entorhinal cortex. Thus, from the standpoint of spontaneous electroencephalographic rhythms, the perirhinal cortex is more closely related to the entorhino-hippocampal system than to the neocortex.

Animals↗

PubMed1999

Disruption of temporo-entorhinal connections abolishes the facilitatory effect of angiotensins on memory in rats.

It has been found in our laboratory that the positive influence of angiotensin II (AII) and its 3-7 fragment [AII(3-7)] on learning and memory processes is mediated by the excitatory amino acids, since it was abolished by NMDA receptor antagonists. The purpose of the present study was to investigate whether bilateral disruption of glutamatergic temporo- entorhinal connections may have an influence on the facilitatory effect of both angiotensin peptides on memory motivated affectively. The bilateral transections of temporo-entorhinal connections were made in 27 male rats 10 days before testing the influence of intracerebroventricular AII and AII(3-7) injection on retrieval of a passive avoidance response. Twenty-seven additional rats served as sham-operated controls. Twenty-five lesioned and 25 sham-operated animals were accepted to the final analysis. AII and its 3-7 fragment significantly improved the retrieval process in sham-operated groups of rats. Bilateral disruption of temporo-entorhinal connections totally abolished the facilitatory effect of both angiotensins on recall of information in a passive avoidance situation. Moreover, bilateral disruption of temporo-entorhinal connections markedly but not significantly attenuated crossings of squares, evaluated in an open field test, without an influence on rearings and bar approaches. These results may suggest that in the facilitatory effect of AII and AII(3-7) on memory motivated affectively involves reciprocal glutamatergic connection between lateral entorhinal cortex and temporal cortex.

Angiotensin II↗

PubMed2000

5-HT transporter sites and 5-HT1A and 5-HT3 receptors in Fawn-Hooded rats: a quantitative autoradiography study.

BACKGROUND: The neuroanatomical profiles of 5-HT1A receptors, 5-HT3 receptors, and 5-HT transporters (5-HTT) in the brain of the Fawn-Hooded (FH) rat, particularly mesocorticolimbic regions, are not fully elucidated. METHODS: By means of in vitro quantitative autoradiography, we used [3H]citalopram, [3H]8-OH-DPAT, and [3H]GR65630 to label 5-HTT, 5-HT1A receptors, and 5-HT3 receptors in the brain of alcohol-naïve FH rats, Wistar-Kyoto (WKY) rats, and FH rats given free access to 5% ethanol and/or after 24 to 48 hr withdrawal. RESULTS AND CONCLUSIONS: In alcohol-naïve rats, FH rats displayed significantly higher (p < 0.05) densities of [3H]citalopram binding in the nucleus accumbens (+30%), lateral septum (+37%), ventral pallidum (+21%), and ventral tegmental area (+24%), as well as an increased binding of [3H]8-OH-DPAT to 5-HT1A receptors in the frontal and parietal cortex (+33%), occipital and temporal cortex (+25%), and hippocampal CA3 region (+31%), compared with WKY rats, whereas both strains exhibited comparable [3H]GR65630 binding to 5-HT3 receptors. Compared with control FH (naive) rats, chronic ethanol consumption significantly decreased (p < 0.(15)[3H]8-OH-DPAT binding in the frontal and parietal cortex (-15%) but significantly increased binding (p < 0.05) in the entorhinal cortex (+25%), retrosplenial granular cortex (+20%), and hippocampal CA1 (+14%) and CA3 regions (+18%). Moreover, ethanol withdrawal induced the same extent of increased [3H]8-OH-DPAT binding in the entorhinal and retrosplenial cortex as seen in FH (chronic) rats. In contrast, [3H]8-OH-DPAT binding in the hippocampal CA1 and CA3 regions was decreased by -9% and -20% from the level of chronic ethanol-treated FH rat (p < 0.05) and returned to the control level seen in FH (naïve) rats. SIGNIFICANCE: The elevated 5-HT transporters and 5-HT1A receptors in the mesocorticolimbic areas in FH rats may reflect a potential innate altered transmission at serotonergic synapses, which possibly may affect the high intake of alcohol in FH rats. The region-specific alterations of 5-HT1A receptors in FH rat brain after ethanol challenges suggest that 5-HT1A receptors are sensitive to ethanol challenges, whereas 5-HTT are apparently insensitive.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2003

Different representations of pleasant and unpleasant odours in the human brain.

Odours are important in emotional processing; yet relatively little is known about the representations of the affective qualities of odours in the human brain. We found that three pleasant and three unpleasant odours activated dissociable parts of the human brain. Pleasant but not unpleasant odours were found to activate a medial region of the rostral orbitofrontal cortex. Further, there was a correlation between the subjective pleasantness ratings of the six odours given during the investigation with activation of a medial region of the rostral orbitofrontal cortex. In contrast, a correlation between the subjective unpleasantness ratings of the six odours was found in regions of the left and more lateral orbitofrontal cortex. Moreover, a double dissociation was found with the intensity ratings of the odours, which were not correlated with the BOLD signal in the orbitofrontal cortex, but were correlated with the signal in medial olfactory cortical areas including the pyriform and anterior entorhinal cortex. Activation was also found in the anterior cingulate cortex, with a middle part of the anterior cingulate activated by both pleasant and unpleasant odours, and a more anterior part of the anterior cingulate cortex showing a correlation with the subjective pleasantness ratings of the odours. Thus the results suggest that there is a hedonic map of the sense of smell in brain regions such as the orbitofrontal cortex, and these results have implications for understanding the psychiatric and related problems that follow damage to these brain areas.

Brain↗

PubMed1999

Bilateral transections of temporo-entorhinal connections attenuate vasopressin improvement of memory in rats.

It has been found in our laboratory that the positive influence of vasopressin (AVP) on memory processes is mediated by excitatory amino acids, since it was abolished by NMDA receptor antagonists. The purpose of the present study was to investigate whether bilateral transections of glutamatergic temporo-entorhinal connections may have an influence on the facilitatory effect of AVP on retrieval process of a passive avoidance behaviour. The bilateral transections of temporo-entorhinal connections were made in male Wistar rats 10 days before testing of the influence of intracerebroventricular AVP (1 microgram per rat) injection on memory, evaluated in a passive avoidance task. Although AVP significantly facilitated the retrieval process both in sham-operated and in lesioned groups of rats, bilateral disruption of temporo-entorhinal connections significantly attenuated the facilitatory effect of AVP on the retrieval process. Moreover, bilateral transections of temporo-entorhinal connections failed to affect motor activity, such as crossings of squares, without an influence on rearings and bar approaches evaluated in an open field test. These results may suggest that in the facilitatory effect of AVP on the retrieval process is involved a reciprocal glutamatergic connection between the lateral entorhinal cortex and the temporal cortex.

Animals↗

PubMed1999

Disruption of temporo-entorhinal connections abolishes recognition memory-enhancing effect of angiotensins in rats.

In our laboratory, the positive influence of angiotensin II and its 3-7 fragment on learning and memory processes was found to be mediated by excitatory amino acids, because it was abolished by N-methyl-D-aspartate (NMDA) receptor antagonists. The purpose of the present study was to investigate whether bilateral disruption of glutamatergic temporo-entorhinal connections may have an influence on the facilitatory effect of both angiotensin peptides on recognition memory. The bilateral transections of temporo-entorhinal connections were made in 32 male rats 10 days before testing the effect of intracerebroventricular AII or AII(3-7) injection on the recognition of objects evaluated in an object-recognition test. Thirty additional rats served as sham-operated controls. The final analysis was based on 29 lesioned and 26 sham-operated animals. AII and its 3-7 fragment significantly improved object recognition in the sham-operated groups of rats. Bilateral disruption of temporo-entorhinal connections totally abolished the facilitatory effect of both angiotensins on object recognition. Moreover, bilateral disruption of temporo-entorhinal connections significantly attenuated crossings of squares and rearings, without affecting bar approaches and defecation evaluated in an open-field test. These results may suggest that the facilitatory recognition memory effect of AII and AII(3-7) requires a reciprocal glutamatergic connection between the lateral entorhinal cortex and the temporal cortex.

Angiotensin II↗

PubMed1992

Cytoarchitecture and neural afferents of orbitofrontal cortex in the brain of the monkey.

The orbitofrontal cortex of the monkey can be subdivided into a caudal agranular sector, a transitional dysgranular sector, and an anterior granular sector. The neural input into these sectors was investigated with the help of large horseradish peroxidase injections that covered the different sectors of orbitofrontal cortex. The distribution of retrograde labeling showed that the majority of the cortical projections to orbitofrontal cortex arises from a restricted set of telencephalic sources, which include prefrontal cortex, lateral, and inferomedial temporal cortex, the temporal pole, cingulate gyrus, insula, entorhinal cortex, hippocampus, amygdala, and claustrum. The posterior portion of the orbitofrontal cortex receives additional input from the piriform cortex and the anterolateral portion from gustatory, somatosensory, and premotor areas. Thalamic projections to the orbitofrontal cortex arise from midline and intralaminar nuclei, from the anteromedial nucleus, the medial dorsal nucleus, and the pulvinar nucleus. Orbitofrontal cortex also receives projections from the hypothalamus, nucleus basalis, ventral tegmental area, the raphe nuclei, the nucleus locus coeruleus, and scattered neurons of the pontomesencephalic tegmentum. The non-isocortical (agranular-dysgranular) sectors of orbitofrontal cortex receive more intense projections from the non-isocortical sectors of paralimbic areas, the hippocampus, amygdala, and midline thalamic nuclei, whereas the isocortical (granular) sector receives more intense projections from the dorsolateral prefrontal area, the granular insula, granular temporopolar cortex, posterolateral temporal cortex, and from the medial dorsal and pulvinar thalamic nuclei. Retrograde labeling within cingulate, entorhinal, and hippocampal cortices was most pronounced when the injection site extended medially into the dysgranular paraolfactory cortex of the gyrus rectus, an area that can be conceptualized as an orbitofrontal extension of the cingulate complex. These observations demonstrate that the orbitofrontal cortex has cytoarchitectonically organized projections and that it provides a convergence zone for afferents from heteromodal association and limbic areas. The diverse connections of orbitofrontal cortex are in keeping with the participation of this region in visceral, gustatory, and olfactory functions and with its importance in memory, motivation, and epileptogenesis.

Afferent Pathways↗

PubMed2005

Increasing Ca2+ transients by broadening postsynaptic action potentials enhances timing-dependent synaptic depression.

Repeated induction of pre- and postsynaptic action potentials (APs) at a fixed time difference leads to long-term potentiation (LTP) or long-term depression (LTD) of the synapse, depending on the temporal order of pre- and postsynaptic activity. This phenomenon of spike-timing-dependent plasticity (STDP) is believed to arise by nonlinear processes that lead to larger calcium transients (and thus LTP) when presynaptic APs precede postsynaptic APs and smaller calcium transients (and thus LTD) when postsynaptic APs precede presynaptic APs. In contrast to predictions from such calcium-peak-detector models, we show that constitutively or artificially broadened APs in layer II/III pyramidal cells of entorhinal cortex (EC) lead to an increase in the dendritic calcium transient and shift the balance of STDP toward LTD. STDP in entorhinal pyramidal cells is NMDA-receptor-dependent and modulated by the Ca(V)1Ca(2+) channel-blocker nifedipine. Results are consistent with an elaboration of the calcium-peak-detector model in which downstream signals from voltage-dependent Ca(2+) channels suppress LTP relative to LTD. Our results suggest that modulation of AP width is a potent way to adjust the rules of synaptic plasticity in the EC.

Action Potentials↗

PubMedDate not supplied

Long-lasting effects of prenatal MAM treatment on water maze performance in rats: associations with altered brain development and neurotrophin levels.

We previously reported that prenatal methylazoxymethanol (MAM) administered on days 11 and 12 of rat pregnancy induces structural changes in the cytoarchitecture of the hippocampal-entorhinal axis. We also showed that young and middle-aged prenatally treated MAM animals displayed changes in brain neurotrophin levels [Neurosci. Lett. 309 (2001) 113; Physiol. Behav. 71 (2000) 57.]. To continue this line of investigation, the working hypothesis adopted was that prenatal MAM administration, by interfering with limbic neurogenesis, could impair learning and memory ability of aged animals in the water maze. It was found that injection of MAM during early rat brain development induced deficits in both the acquisition and retention phases of the Morris maze. These behavioral changes were associated with significant changes in brain nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), reduced choline acetyltransferase (ChAT) immunoreactivity in forebrain cholinergic neurons and loss of neuropeptide Y (NPY) immunodistribution in cells of the entorhinal cortex. This finding, as well as confirming previous studies showing that injection of prenatal MAM administration induces significant changes in hippocampal-entorhinal axis neurogenesis and marked behavioral deficits in adult life, provides additional experimental evidence supporting the hypothesis that loss of NGF and/or BDNF-receptive or producing cells can co-occur at the onset of neurodevelopmental disorders.

Animals↗

PubMed1996

Fibroblast growth factor-2 protects entorhinal layer II glutamatergic neurons from axotomy-induced death.

The entorhinal cortex is a major relay between the hippocampus and other cortical and subcortical regions. Glutamatergic axons from layer II neurons form the entorhinal cortical projection to the hippocampus via the perforant pathway. We have demonstrated previously that lesion of the perforant pathway causes the death of approximately 30% of entorhinal layer II (ECL2) neurons. To elucidate mechanisms contributing to neuronal death and to investigate strategies preventing it, we identified the phenotype of the vulnerable neuronal population. Sections were immunolabeled with antibodies to the neuronal markers NeuN, glutamate, and calbindin-D28k, and to receptors for fibroblast growth factor-2 (FGFR1) and NMDA (NMDAR1) and were examined using confocal microscopy. Calbindin immunoreactivity was strikingly lamina-specific to ECL2, where one-third of all ECL2 neurons were calbindin-positive. Localization of glutamate revealed that half of the glutamatergic ECL2 neurons coexpressed calbindin. Quantification using unbiased stereology at 9 weeks after lesion of the perforant pathway revealed that the only ECL2 neuronal population that experienced a significant (70%) loss (20% of the total) was the population of glutamatergic ECL2 neurons that did not coexpress calbindin. All ECL2 neurons expressed FGFR1; therefore, we tested the role of FGF-2 in the survival of glutamatergic ECL2 neurons. We grafted fibroblasts genetically engineered to express nerve growth factor or FGF-2 and found that only FGF-2 grafts prevented loss of the vulnerable glutamatergic/calbindin-negative neurons. We present a hypothesis for the selective vulnerability of these glutamatergic/calbindin-negative ECL2 neurons and address the role of FGF-2 in neuronal rescue.

Afferent Pathways↗

PubMed1975

A normally laminated afferent projection to an abnormally laminated cortex: some olfactory connections in the reeler mouse.

The relative positions of pyramidal and polymorphic cell classes are inverted in the central olfactory cortical structures of the reeler mutant mouse. Each cell class is generated at the normal embryonic time. The polymorphic cells of the mutant, like those of the normal, are generated between E11-E13. The pyramidal cells are formed between E11-E16 in both. Despite the anomalous positions of their somata deep in the cortex the apical dendrites of many pyramidal cells reach and ramify at a superficial cortical level subjacent to the lateral olfactory tract. The main and accessory olfactory bulbs are cytoarchitectonically normal in the mutant and project normally upon the anterior olfactory nucleus, the olfactory tubercle, the hippocampal rudiment, the piriform cortex, the amygdaloid region and the entorhinal cortex. As in the normal animal the axons transverse layer Ialpha, and their terminals are concentrated in the immediately subjacent laminar zone. The rostrally directed cortic-cortical association system of the piriform cortex projects upon the anterior olfactory nucleus in the mutant just as in the normal with a relative concentration of terminals in a lamina subjacent and complementary to the zone of termination afferent systems in the abnormally laminated olfactory cortex of the mutant syggests that, in this system at least, the developmental mechanisms which determine relative position of neuron somata and those which govern axon trajectories and the distribution of axon terminals are largely independent.

Animals↗