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N Berman

Publications and source records attributed to N Berman.

At least 91 records · Page 5Linked to original sources
PubMed1982

Iodine-125-labeled triiodothyronine in rat brain: evidence for localization in discrete neural systems.

Autoradiograms prepared from adult rat brains demonstrate that nerve cells and neuropil in different brain regions selectively concentrate and retain intravenously administered triiodothyronine, by mechanisms susceptible to saturation with excess triiodothyronine. A neuroregulatory role for thyroid hormones, strongly supported by the observations, may account for their marked effects on behavior and the activity of the autonomic nervous system.

Animals↗
PubMed1982

Effects of visual cortical lesions on receptive-field properties of single units in superior colliculus of the rabbit.

1. One hundred seventy-nine single units were studied in the superior colliculus of seven Dutch-belted rabbits following ablation of the ipsilateral visual cortex. The response characteristics of these units were compared with those of 284 single units recorded from the superior colliculus of 20 intact animals. 2. In both the upper and lower parts of the stratum griseum superficiale and in the stratum griseum intermediate, there were smaller proportions of direction-selective visual units in the decorticated animals than in normal ones. 3. In the upper stratum griseum superficiale, a larger proportion of units responded to stroboscopic illumination in the decorticated animals than in normal ones. Also, in the decorticated animals, there was a larger proportion of units whose responses to a small moving stimulus were inhibited by the simultaneous presentation of stroboscopic illumination. 4. In both the upper and lower parts of the stratum griseum superficiale, a larger proportion of visual units responded well to stationary stimuli and a smaller proportion of visual units showed habituation in decorticated animals compared to normal ones. 5. In the lower stratum griseum superficiale, the receptive fields of units were larger and were more elongated in the anterior-posterior dimension in the decorticated animals than in normal ones. 6. In the two preparations, units did not differ in responsiveness or spontaneous activity; and visual units did not differ in the sustained or transient nature of their responses, the selectivity for light or dark stimuli, the selectivity for onset or offset of the stimuli, or the selectivity for stimulus velocity. 7. This study provides evidence for the importance of the visual corticotectal projection in the elaboration of the visual receptive-field properties of units in the superior colliculus of the rabbit. In addition, this study shows that the subdivisions of the superior colliculus are differentially affected by the loss of the visual corticotectal projection.

Animals↗
PubMed1982

Functional organization of neurons in cat striate cortex: variations in ocular dominance and receptive-field type with cortical laminae and location in visual field.

1. Binocularity and receptive-field type of cortical neurons were assessed relative to the cortical layer in which the neurons were recorded and to receptive-field position in the visual field. 2. Receptive fields were observed up to 2 degrees into the ipsilateral half of the visual field. In the region up to 2 degrees on either side of the vertical meridian, the relative contribution of the ipsilateral eye was reduced. This progression in ocular dominance from ipsilateral to contralateral visual field agrees well with the distribution of X-cells about the nasotemporal division. 3. The region of maximum binocularity in each hemifield was found to be a 12 degree wide vertical strip extending from the vertical meridian to 12 degrees contralateral. In the representation of the central 12 degree strip, most units in all cortical layers were binocular. 4. Low levels of binocularity were observed at a considerable distance before the monocular portion of the visual field was reached. 5. The decrease in binocularity for simple cells occurred closer to the vertical meridian than for complex cells. 6. The proportions of cells classified as simple or complex did not change with position in the visual field. 7. At all locations in the visual field, complex cells showed a higher percentage of binocularity than simple cells. 8. The proportions of two types of simple cells, I and II, and complex cells were variable between cortical layers. Layer IV contained predominantly simple II cells, whereas layer V contained predominantly complex cells. 9. The results are discussed in terms of visual perception and the dynamic pattern of visual stimulation around a moving animal, the optic flow field.

Animals↗
PubMed1981

Origins of the pretectal and tectal projections to the central lateral nucleus in the cat.

The pretectal and tectal projections to the thalamic intralaminar nuclei in the cat were studied following horseradish peroxidase injections centered in the central lateral nucleus. Retrogradely labeled neurons were found in both the pretectum and the superior colliculus, ipsilateral and, to a lesser extent, controlateral to the injection site. Labeled pretectal neurons were found throughout all pretectal nuclei; the densest concentrations were in the medial pretectal nucleus, the anterior pretectal nucleus and the nucleus of the posterior commissure. The major source of tectal projections were the small neurons in the stratum griseum intermediate.

Animals↗
PubMed1981

Origins of the projections of the superior colliculus to the dorsal lateral geniculate nucleus and the pulvinar in the rabbit.

The origins of the projections of the superior colliculus to the dorsal lateral geniculate nucleus and to the pulvinar in Dutch-belted rabbits were investigated using horseradish peroxidase (HRP) methods. Following injections of HRP in the dorsal lateral geniculate nucleus, retrogradely labeled neurons were found in the upper two-thirds of the stratum griseum superficiale of the ipsilateral superior colliculus. Most of the labeled somata were spindle-shaped, and their major axes tended to be perpendicular to the surface of the superior colliculus. In contrast, following injections of the pulvinar, labeled neurons were found in the lower third of the ipsilateral stratum griseum superficiale. In these cases, the labeled somata were larger than those labeled following dorsal lateral geniculate injections and were multipolar in shape.

Animals↗
PubMed1981

Organization of direction preferences in cat visual cortex.

Single unit recordings were made from the visual cortex of 5 adult cats. Visual stimuli were used to determine the stimulus orientation and direction of movement preferred by cortical cells. Analysis of the sequence of neurons recorded along each electrode penetration and their direction preferences indicates that neurons preferring similar directions of movement are clustered together in the cortex.

Animals↗
PubMed1981

A quantitative assessment of eye alignment in cats after corpus callosum transection.

Eye alignment was measured in cats using a technique involving projection of retinal landmarks, determination of receptive field separation in binocular units and measurement of ganglion cell density. This technique has an accuracy of 20' of arc. Using this technique, we determined that alterations in eye alignment occur following surgical transection of the corpus callosum in cats. These changes are first observed two weeks after surgery and are still present ten months later.

Animals↗
PubMed1981

Stroboscopic rearing reduces direction selectivity in rabbit visual cortex.

Rabbits reared from birth in stroboscopic illumination have no experience of visual motion. In primary visual cortex of these animals there is a large reduction in the number of cells which are direction selective. This result, contrary to previous reports, shows that the rabbit visual system can be modified by early visual experience.

Animals↗
PubMed1979

The rabbit and the cat: a comparison of some features of response properties of single cells in the primary visual cortex.

Receptive field characteristics of single cells in primary visual cortex of rabbit were studied. Seventy-two percent of cells were found to be orientation selective, and the remainder had concentric, uniform, movement selective or pure direction selective receptive fields. Single cells were also recorded from primary visual cortex of cat to permit a comparison of visual cortical organization in cats and rabbits. Laminar organization of receptive field types was observed in rabbits which was similar in most respects to that described in the cat. Although the major categories of orientation selective cells (simple, complex, hypercomplex) were similar for both cat and rabbit, many differences emerged: (I) tuning of orientation selectivity was narrower in cats than in rabbits; (II) units which preferred oblique orientations were less frequently represented in rabbits than in cats; (III) orientation preferences appeared to be arranged in clusters in rabbit cortex; in rabbits we found no evidence of the columnar organization of orientation selectivity which characterizes cat visual cortex. A comparison of our data with those previously reported for mouse, rat, hamster and opossum visual cortex suggest that mammals in which a significant proportion of visual cortical cells are not orientation selective have in common certain patterns of cortical organization involving a less precise and less specilized representation of stimulus orientation.

Animals↗
PubMed1978

Direction and specificity of the axonal and transcellular transport of nucleosides.

The axoplasmic transport of nucleosides or their derivatives has been examined autoradiographically in avian and mammalian brains. Following injections of [3H]-adenosine or [3H]uridine intravitreally in chicks and rats or into the thalamus or neocortex of rats, three findings emerge: (1) axoplasmic transport of these materials occurs both in the anterograde and retrograde direction in birds and mammals; (2) anterograde transport in the axons of injected cells results in considerable cellular labeling in the region in which the axons terminate. This labeling is not exclusively transsynaptic, but probably results from some less specific, trancellular transport, since glial cells at the terminal site and along the path of the axons also become labeled; (3) injection of [3H]uridine in the chick optic and rat thalamocortical systems results in a pattern of labeling which differs considerably from that seen after injection of [3H]adenosine. After [3H]adenosine injections in the chick eye or rat thalamus, retrograde cell labeling is far more obvious than anterograde, transcellular labeling; after injections of [3H]uridine, anterograde, transcellular labeling is more intense than retrograde cell labeling.

Adenosine↗
PubMed1977

A retino-pulvinar projection in the cat.

Injections of tritiated amino acids were made in one eye of Siamese and common cats including young kittens. After survival periods of 1--7 days axoplasmically transported label accumulated in a portion of the pulvinar nucleus as well as in the other known sites of termination of the retinofugal pathway. The retino-pulvinar projection is present at birth; it is bilateral and approximately symmetrical in common cats but the ipsilateral component is markedly reduced in Siamese animals. Labeled terminal ramifications of the retinal fibers in the pulvinar take the form of a thin, interrupted sheet oriented dorsoventrally and lying at the extreme lateral edge of the pulvinar nucleus. It appears to be continuous caudally with the medial interlaminar nucleus of the lateral geniculate complex, but the cells about which the grains cluster are clearly different from those of the medial interlaminar nucleus.

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