摘要:

AbstractIn a program of surveying the characteristics of visual receptive fields of neurons in rabbit brain, we have explored cortical sectors beyond the striate and occipital cortices and found cells in a part of the temporal lobe that were responsive to visual stimulation. Using evoked potential and unit‐cluster methods, this temporal visual areas was mapped to be roughly oval‐shaped, 3 mm × 2mm in size, and at about the level posterior to the apex region of auditory area 1. It is located ventral to and continuous with visual area 11, at about the caudal half of M. Rose's temporal cortices 1 and 2 (T1 and T2).Only about two‐thirds of 96 units studied responded to some sort of moving light stimulation. These motion‐sensitive cells were divided into four groups. Cells in the first group (22) responded best to a large light spot or shadow sweeping quickly across the field. Cells in the second group (29) responded to slow moving, jerking spot. Nine cells responded to a narrow, dark bar thrusting into a lighted field. Four cells are “direction‐selective,” responding to light stimulus moving in one direction and showing either no response or decreased background discharges in the oppsite direction. In addition, three cells required unusual stimulus features. Of the 38 cells tested, nine of them were found to be binocularly driven. These receptive field characteristics are quite different from those described for other visual centers of the rabbit. The significance of these results together with data on the anatomical connections of this cortical area as reported in the following paper

ISSN:0092-7317    

DOI:10.1002/cne.901710202

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractUsing Fink‐Heimer, autoradiographic and horseradish peroxidase techniques, the connections of a temporal visual cortical region of the rabbit were explored. The temporal visual area covers portions of areas T1and T2, and is reciprocally connected with the posterior nucleus and suprageniculate nuclei of the thalamus. It was also shown that the temporal visual area projects to a similar region in the opposite hemisphere, and to intermediate laminae of the superior colliculus.The temporal visual area is discussed in comparison to other similar regions in the cortex of primate species. It is pointed out that recent evidence indicates visual areas in the occipital cortex of non‐primate species may be no less numerous and complex than those in primate spec

ISSN:0092-7317    

DOI:10.1002/cne.901710203

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe mediodorsal nucleus of the rat thalamus has been divided into medial, central and lateral segments on the basis of its structure and axonal connections, and these segments have been shown by experiments using the autoradiographic method of demonstrating axonal connections to project to seven distinct cortical areas covering most of the frontal pole of the hemisphere. The position and cytoarchitectonic characteristics of these areas are described. The medial segment of the nucleus projects to the prelimbic area (32) on the medial surface of the hemisphere, and to the dorsal agranular insular area, dorsal to the rhinal sulcus on the lateral surface. The lateral segment projects to the anterior cingulate area (area 24) and the medial precentral area on the dorsomedial shoulder of the hemisphere, while the central segment projects to the ventral agranular insular area in the dorsal bank of the rhinal sulcus, and to a lateral part of the orbital cortex further rostrally. (The term “orbital” is used to refer to the cortex on the ventral surface of the frontal pole of the hemisphere.) A ventral part of this orbital cortex also receives fibers from the mediodorsal nucleus, possibly its lateral segment, but the medial part of the orbital cortex, and the ventrolateral orbital area in the fundus of the rhinal sulcus receive projections from the paratenial nucleus and the submedial nucleus, respectively. All of these thalamocortical projections end in layer III, and in the outer part of layer I. The basal nucleus of the ventromedial complex (the thalamic taste relay) has been shown to have a similar laminar projection (layer I and layers III/IV) to the granular insular area immediately dorsal to, but not overlapping, the mediodorsal projection field. However, the principal nucleus of the ventromedial complex appears to project to layer I, and possibly layer VI, of the entire frontal pole of the hemisphere. The anteromedial nucleus does not appear to project to layer III of the projection field of the mediodorsal nucleus, although it may project to layers I and VI, especially in the anterior cingulate and medial precentral areas.A thalamoamygdaloid projection from the medial segment of the mediodorsal nucleus to the basolateral nucleus of the amygdala has also been demonstrated, which reciprocates an amygdalothalamic projection from the basolateral nucleus to the medial segment. The habenular nuclei also appear to project to the central nucleus of the amygdala.These results are discussed in relation to the delineation and subdivision of the prefrontal cortex in the rat, and to amygdalothalamic and amygdalocortical projections which are described in a subsequent paper (Krettek and Price, '

ISSN:0092-7317    

DOI:10.1002/cne.901710204

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractA specialization of the Mongolian gerbil inner ear allows easy access for electrophysiological recording from the auditory nerve and other structures of the internal auditory meatus. The round‐window membrane is recessed, creating a cavity connecting the bulla and the external wall of the modiolus. This cavity has been named the round‐window antrum. A small opening made in the dorsomedial wall of the round‐window antrum gives access directly to the modiolus and internal auditory meatus, with no other openings in the cranium required. This surgery is less drastic than that needed for similar access in most other mammals. The anatomy of the specialized region is presented from studied with the light microscope. Emphasis is placed on the relationship between external features of the wall of the round‐window antrum and the internal anatomy of the modiolus and internal auditory meatus. In addition, these studies reveal that cell bodies of the acoustic‐nerve nucleus are located in the auditory nerve, central to the glial dome. About 22 ± 8 cells are found in an auditory nerve. Their appearance with a Nissl stain is similar to cells found in rat, mouse, and man. The cell dendrites are preferentially oriented perpendicular to the longitudinal course of the auditorynerve fibers. The anatomy of the gerbil auditory system should allow direct electrophysiological recording from t

ISSN:0092-7317    

DOI:10.1002/cne.901710205

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractA genetic mutation in Siamese cats causes retinogeniculate fibers representing roughly the first 20 degrees of ipsilateral visual field in each eye to cross aberrantly in the optic chiasm and terminate in the wrong lateral geniculate nucleus (LGN). Previous investigations have shown that in the visual cortex this extra representation of ipsilateral visual field can be organized into one pattern in Boston Siamese cats, another in Midwestern. This finding was confirmed here.The possibility that the organization of the LGN might account for these two patterns was studied using combined anatomical and physiological methods. On the basis of microelectrode recordings from the visual cortex, 11 out of the 12 Siamese cats included here were Boston cats; one was Midwestern. The distribution of retinogeniculate terminals was examined in each cat using autoradiographic techniques following an eye‐injection of3H‐proline. Overall, the LGN organization in Boston cats was similar to that of Midwestern: both lateral and medial normal segments of lamina A1 (mnA1) were present. In Boston cats, however, the mnA1 was remarkably small and shifted ventromedially in the nucleus to allow for the fusion between the medial borders of lamina A and the abnormal segment of A1. In the Midwestern cat this fusion was not apparent and the medial normal segment of A1 was significantly larger.These differences in organization of the LGN are consistent with those seen at the level of the visual cortex in Midwestern and Boston Siamese cats. It was not possible, however, to relate them clearly to the characteristic strabismus of these anim

ISSN:0092-7317    

DOI:10.1002/cne.901710206

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractIn the normal cat most visual fibers in the splenium of the corpus callosum are concerned with a representation of the vertical meridian of the visual field. These fibers for the most part originate from cortical regions forming the border between adjacent architectonic areas, such as the anatomical 17‐18 border. Due to a genetic mutation in Boston Siamese cats, the anatomical 17‐18 border now represents a region in the ipsilateral visual field roughly 20 degrees away from the vertical meridian, and the representation of the vertical midline is displaced from the border to regions within areas 17 and 18 proper. Do visual fibers in the Boston Siamese cat corpus callosum originate, as in normal cats, from the 17‐18 border even though the vertical meridian is no longer represented there? The present paper deals with this question from a physiological standpoint.Single visual fibers in the corpus callosum of 11 Boston Siamese and two normal cats were recorded using extracellular microelectrodes. Receptive fields were mapped and their positions used to infer the likely cortical site of origin for each fiber. In confirmation of earlier findings, most callosal receptive fields in the normal cat were closely apposed to the vertical meridian, as would be expected if only those visual cortical regions which represent the vertical meridian, such as the border between areas 17 and 18, contribute to the corpus callosum. In Boston Siamese cats, however, an abnormally large amount of visual field was represented in the corpus callosum, with some receptive fields located as far as 25 degrees away from the vertical meridian. The representation of the vertical meridian was nevertheless substantial.The present findings suggest, therefore, that in Boston Siamese cats callosal fibers do not originate solely from the boundary regions between adjacent cortical areas, such as the anatomical 17‐18 border, but originate also from other cortical regions, especially the vertical meridian representation, regardless of their location with respect to such bou

ISSN:0092-7317    

DOI:10.1002/cne.901710207

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe structure of the plasma membrane of Purkinje cell dendrites was examined in weaver and staggerer mutant mice. Purkinje spines in weaver mice have clusters of intramembrane particles which resemble those at normal synapses with parallel fibers, even though no parallel fibers are formed in this mutant. There are very few spines in the staggerer, and these manifest normal intramembrane structure at contacts with climbing fibers. The spines which would normally be involved in synapses with parallel fibers are never formed in the staggerer, and the intramembrane structures which would have been associated with these spine synapses are also lacking. Thus, during postnatal cerebellar development in the mutants, acquisition of intramembrane specializations requires Purkinje spine formation but can occur independently of the development of parallel fibers.

ISSN:0092-7317    

DOI:10.1002/cne.901710208

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe basal ganglia are presently implicated in learning, and thyroid deficiency induced neonatally is known to affect mentation. The effects of such a deficiency on the developing caudate nucleus might be used to provide insight into structure and function of the normal subcortical brain, as well as possible influences of these extrapyramidal structures on mental retardation. Propylthiouracil was added to the diet of lactating rat dams and observations of the developing caudate nuclei of normal and hypothyroid rats were made at 8, 14, 20, 30 and 42 days by using various tissue stains and Golgi‐Cox preparations.Seven different types of neurons were distinguished in the caudate nucleus. Differences in the size of cell somata and the varying morphology of axons and dendrites were criteria used to make distinctions. Normally, the nucleus acquires cytoarchitectural complexity during the first three postnatal weeks. Within this period, neuron incidence increases in the caudate neuropil with age while the germinal matrix density decreases. Neuron accumulation reaches a plateau after the third week and cell migration is essentially complete at the end of the first postnatal month as shown by computer analysis of Nissl stained cell counts. Branching of cellular processes, attainment of receptor spines and complexity of the fiber network also appeared during this period.Retardation of structural development with thyroid hormone deficiency was shown by decreased numbers of neurons, inhibition of dendritic arborization, decreased numbers of dendritic spines and a reduced complexity of axonal plexuses. Thyroid deficiency delays cell migration during the first three weeks when compared to age‐matched normal controls. The lack of thyroid hormone does not appear to influence the size of neuron somata, and the extent of related dendritic fields, nor does hypothyroidism affect a specific cell type population. Generalized disturbances of caudate nuclear morphological maturation are caused by the deficiency. An apparent compensatory process, including a spurt of neural growth and differentiation, takes place in the period between days 14 and 30 in the deficient animals and a seemingly “normal” caudate cytoarchitecture is seen after the third postnatal week. Quantitative data, however, show that this rapid “catch up” process is inadequate.The developmental imperfection of the caudate nucleus which persists might be a part of the underlying substrate for the mental retardation, disturbed motor performance and perceptual handicaps which are found in the hu

ISSN:0092-7317    

DOI:10.1002/cne.901710209

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901710201

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY