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P Grobstein

Publications and source records attributed to P Grobstein.

31 records · Page 2Linked to original sources
PubMed1982

Orienting behavior of juvenile frogs with both a pre-metamorphically rotated and a normal eye.

We have studied the orienting behavior of juvenile Rana pipiens in which one eye was rotated at late larval stages and the other eye left intact. Such frogs orient accurately to stimuli falling solely in the visual field of the intact eye and systematically misorient to stimuli falling solely in the field of the rotated eye. Stimuli within the area of visual field overlap elicited two distinct sets of responses, one attributable to the normal and the other to the rotated eye.

Animals↗
PubMed1981

Effects of progressively longer durations of monocular deprivation on development of visuocortical receptive fields in the rabbit.

Three groups of rabbits were reared with monocular eyelid suture. Percentages of cells with various receptive field types were determined by recording in the deprived visual cortex of animals 30-35 days, 46-55 days, and 20-36 months old. These results, together with previously published data from two other groups of monocularly deprived rabbits, are described relative to normative data for 9-10-day-old and adult rabbits. During the first postnatal year cells in the deprived visual cortex acquire normal adult proportions of receptive field types, but do so over a longer course than that which is characteristic of cells in non-deprived visual cortex. With continued deprivation for 2-3 years there is a subsequent loss of oriented type cells and a corresponding increase in non-responsive cells.

Animals↗
PubMed1980

The potential binocular field and its tectal representation in Rana pipiens.

We have studied binocularity in Rana pipiens using optical, behavioral, and electrophysiological assays. The first two assays yielded a consistent picture of the size and shape of the area of uniocular visual field overlap, the potential binocular field. Potential binocular field has an extent of about 90 degrees on the horizontal in front of the frog, narrows to about 60 degrees above the frog's head, and continues to a point well behind the frog. This differs somewhat from a previous report (Fite, '73). Uniocular visual field extent on the horizontal is in excess of 225 degrees, permitting both a large binocular field and panoramic vision. The electrophysiological assay confirms the large uniocular visual field extent. It further shows that physiological binocularity closely reflects uniocular visual field overlap, in the sense that tectal loci representing positions in the potential binocular field, including those behind the frog's head, display convergent inputs from the two eyes.

Animals↗
PubMed1977

Receptive field characteristics of neurons in a visual area of the rabbit temporal cortex.

In 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 area was mapped to be roughly oval-shaped, 3 mm x 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 opposite 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 were discussed.

Animals↗
PubMed1975

Development of receptive fields in rabbit visual cortex: changes in time course due to delayed eye-opening.

Rabbit pups had one eye sutured closed before the time at which the eyes normally open. At 20-27 days of age, single-unit recordings were made both from the striate cortex contralateral to the sutured eye (deprived cortex) and from that contralateral to the eye which had opened normally (control cortex). The percentages of units encountered which fell into various receptive field categories differed on the two sides. The deprived cortices had a lower percentage of visually responsive cells, a higher percentage of indefinite cells, and totally lacked cells sensitive to orientation of a stimulus bar. In these respects they closely resembled previous observations on rabbit pups just before normal eye-opening. By contrast, the control cortices of the same animals were comparable to normally reared rabbits of the same age. We conclude, therefore, that developmental events which normally follow eye-opening can be affected in their time course by delaying eye-opening.

Aging↗
PubMed1973

Development of rabbit visual cortex: late appearance of a class of receptive fields.

In young rabbits before the age at which the eyes open, only three of the seven receptive field types described in the adult visual cortex are detectable. The remaining four receptive field types-which share the property of having radially asymmetric fields-appear later, coincident with a decline in the percentage of cells that are visually responsive but not classifiable as to receptive field type.

Action Potentials↗
PubMedDate not supplied

Induction of the ipsilateral retinothalamic projection in Xenopus laevis by thyroxine.

Hormones are important in the development of behaviour and there is now abundant evidence that they also affect the morphological development of the nervous system. In principle, hormones could act by inducing new patterns of connectivity between widely separated structures in the nervous system or by influencing local connectivity. Most available work documents effects of the latter sort. We present here evidence for the former. Our results indicate that thyroxine, the hormone which causes metamorphosis in the frog Xenopus laevis, can induce precociously in a pre-metamorphic tadpole the ipsilateral retinothalamic projection, a retinofugal pathway which normally develops during metamorphosis. Our evidence suggests that the hormone's presence in one eye alone is sufficient to cause axons of some ganglion cells in that eye to grow to targets in the ipsilateral thalamus and to form terminal fields of appropriate morphology. Since the axons of the induced pathway project ipsilaterally, unlike axons in the normal premetamorphic tadpole, virtually all of which project contralaterally, our results are also relevant to questions concerning the control of axonal trajectory in the optic chiasm.

Animals↗