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Dive into the research topics where Alan C. Rosenquist is active.

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Featured researches published by Alan C. Rosenquist.


Brain Research | 1974

Visual receptive fields of single striate cortical units projecting to the superior colliculus in the cat

Larry A. Palmer; Alan C. Rosenquist

Summary Single units in the striate cortex of anesthetized, paralyzed cats were activated antidromically by electrical stimulation of the superior colliculus and their receptive fields were plotted and studied. These corticotectal neurons were found to lie in layer V and, based on standard criteria 21,22,30 , the majority were complex cells. Most of the corticotectal neurons were driven about equally by the two eyes and none were strictly monocular. All of the corticotectal neurons were orientation selective, a large proportion were direction selective and they tended to have large receptive fields. The corticotectal units differed from most other cortical cells in that they lacked any clear summation with stimulus length and, in general, responded very well to small moving spots. The data reinforces the idea, based on ablation studies 4,32,42 that direction selectivity and the effectiveness of the ipsilateral eye in driving collicular units are dependent on binocular, direction selective inputs from the striate cortex. The data were also discussed from the point of view of information sorting within the visual cortex and its efferent projections.


Brain Research | 1974

An autoradiographic study of the projections of the dorsal lateral geniculate nucleus and the posterior nucleus in the cat

Alan C. Rosenquist; Stephen B. Edwards; Larry A. Palmer

Injections of small quantities of tritiated amino acid were made in the dorsal lateral geniculate nucleus (LGNd) and the adjacent posterior nucleus (PN), and the cortical projections of these nuclei were studied using the autoradiographic tracing method. It was concluded that the laminar division of LGNd projects only to areas 17 and 18 of the ipsilateral hemisphere. That portion of LGNd designated the medial interlaminar nucleus (MIN) projects to areas 18, 19 and the Clare—Bishop are (CB). PN was found to project to areas 19, CB, and a region within the splenial sulcus. No subcortical projections of LGNd or PN were observed. The distribution of transported label within cortical laminae showed that terminations occur largely in layer IV of all cortical areas studied, and that a relatively small number of terminations take place in layers I–III and in layer V. The cortical labeling pattern in areas 17 and 18 indicated that a substantial number of terminations may also exist in layer VI. The initial trajectory of PN and MIN axons was studied. PN fibers coursed laterally and remained closely applied to the dorsal border of LGNd before turning dorsally into the visual radiations. Most MIN fibers, on the other hand, passed laterally through the laminae of LGNd before ascending to the cortex.


Vision Research | 1976

Paralysis of the awake human: Visual perceptions

John K. Stevens; Robert C. Emerson; George L. Gerstein; Tamas Kallos; Gordon R. Neufeld; Charles W. Nichols; Alan C. Rosenquist

Abstract Subparalytic doses ofcurarewere given to three observers. Four major perceptions were reported: (1)displacement or repositioning of the perceived visual world in the direction of a successfully executedeye movement; (2)jumping during a saccade; (3)movement associated with drift of the eye; (4) increasedeffort associated with each eye movement. Paralytic doses ofsuccinylcholinewere administered to a single observer. Three major perceptions were reported: (1)displacement in the direction of the intended eye movement without jumping: (2) a sensation that greateffort was required to move the eye; (3)fading of the visual image due to effective retinal stabilization. Similar visual perceptions were observed when the eye was paralyzed with a local anesthetic; however, nofading or sense ofeffort was reported. No deficits in pattern vision (except for intermittent fading) were reported in any of the studies.


Brain Research | 1985

Afferent connections of the thalamic intralaminar nuclei in the cat

Elin F.S. Kaufman; Alan C. Rosenquist

Afferents to the central lateral (CL), paracentral (PC) and central medial (CE) intralaminar nuclei (ILN) from cortical and subcortical sites were studied in the cat. We utilized stereotaxically guided injections of HRP into the CL and PC nuclei and tritiated leucine injections into various visual, parietal and limbic areas of cortex to demonstrate these connections. In studying the relatively weak visual cortical projections to the ILN, we demonstrated projections from areas 19, 20a, 21a, 21b, AMLS, PMLS and PLLS. However, our HRP injections into the ILN often revealed only a few labeled cells in any of the above areas; therefore conclusions regarding the absence of projections to ILN from remaining visual cortical areas should be made cautiously. The ILN receive heavier projections from the frontal eye fields, cingulate cortex, splenial cortex, insular cortex, somatosensory areas SI and SII, auditory areas SF, AII, and Ep, and parietal areas 5 and 7. The most robust projections appear to be from from frontal eye fields, cingulate and parietal areas. No topography was apparent in the projections to the ILN. All cortical projections originate ipsilaterally from layers V and VI. Heavy subcortical projections to the ILN originate in the pretectum, superior colliculus, reticular formation, and periaqueductal grey. Fewer afferents arise from several other brainstem and thalamic nuclei.


Experimental Neurology | 1971

Visual receptive field properties of cells of the superior colliculus after cortical lesions in the cat

Alan C. Rosenquist; Larry A. Palmer

Abstract Single units were studied in the superficial gray and optic laminae of the superior colliculus of cats during light barbiturate anesthesia. Cells in normal animals reponded maximally to moving stimuli, with 75% showing direction selectivity and 80% being strongly driven by either eye (binocular convergence). Large chronic cortical lesions that included area 17, or lesions limited to area 17 alone, resulted in a much reduced proportion of cells in the ipsilateral colliculus showing direction selectivity (12%) and binocular convergence (17%). In contrast, after lesions no change was seen in the spatial properties of collicular receptive fields. Large cortical lesions sparing area 17 did not produce the above effects on collicular cells. Cortical lesions placed 1 hr to 3 days before recording produced the same loss in direction selectivity and binocular convergence as lesions of 16 months duration. We conclude that in the cat these properties of collicular cells are dependent upon the integrity of cortical area 17.


Neuroscience | 1981

Projections of the pulvinar-lateral posterior complex to visual cortical areas in the cat

L.L. Symonds; Alan C. Rosenquist; Stephen B. Edwards; Larry A. Palmer

Abstract The projections of the pulvinar-lateral posterior complex of the cat were studied using the autoradiographic tracing method and related to 15 previously defined cortical areas. The results indicate that each of three separate zones within the pulvinar-lateral posterior complex has a different pattern of projection. The most lateral zone, the pulvinar, sends fibers to at least seven cortical areas, most of which are known to have input from other visual areas within the brain: the splenial visual area, the cingulate gyrus, and areas 5, 7, 19, 20a and 21a. A zone located just medial to the pulvinar, the lateral division of the lateral posterior complex, projects to at least eight visual areas in the cortex: areas 17, 18, 19, 20a, 21a, 21b, the posteromedial lateral suprasylvian area and the ventral lateral suprasylvian area. The most medial zone, the intermediate division of the lateral posterior complex, projects to at least four cortical areas: 20a, the posterior suprasylvian area, the posterolateral lateral suprasylvian area and the dorsal lateral suprasylvian area. Of the 15 cortical areas that receive fibers from the pulvinar-lateral posterior complex, only three (areas 19, 20a and 21a) receive projections from more than one of these thalamic zones, and only one of the cortical areas (20a) receives fibers from all three zones. Thus, the data support the division of the pulvinar lateral posterior complex into three zones on the basis of their unique and largely non-overlapping projections to the visual cortex.


Brain Research | 1981

Retinotopic organization in the cat lateral posterior-pulvinar complex

Denis Raczkowski; Alan C. Rosenquist

Abstract Multiple unit mapping experiments revealed three orderly representations of the visual field in the extrageniculate visual thalamus. These three maps correspond to subdivisions of the lateral posterior-pulvinar complex based on connectional and histological criteria.


Neurology | 1988

Cerebral metabolism and patterned visual Stimulation: A positron emission tomographic study of the human visual cortex

Michael Kushner; Alan C. Rosenquist; Abass Alavi; M. Rosen; Robert Dann; F. Fazekas; Thomas M. Bosley; Joel H. Greenberg; Martin Reivich

We studied the impact of visual stimulation upon cerebral metabolism in normal young men using FDG-PET. Results obtained from subjects receiving patterned visual stimulation while performing an ocular fixation task were compared with results from ocular fixation alone. Visual stimulation in the macular region of either hemifield produced significant increases in metabolism of the contralateral posterior striate cortex. Visual stimulation induced highly significant asymmetries in metabolism of the prefrontal and inferior parietal cortices. Metabolic activation in extrastriate areas tended to be right-sided. These findings support the classic notion of retinotopic organization within the primary visual sensory cortex. They also indicate that the patterns of cerebral metabolism are not equivalent between the two cerebral hemispheres. This latter finding suggests that in humans the right cerebral hemisphere may be specialized for visual processing.


Neurology | 1985

Ischemic lesions of the occipital cortex and optic radiations Positron emission tomography

Thomas M. Bosley; Alan C. Rosenquist; Michael Kushner; Allan M. Burke; Alan Stein; Robert Dann; Walter Cobbs; Peter J. Savino; Norman J. Schatz; Abass Alavi; Martin Reivich

We used 18-F-fluoro-2-deoxyglucose positron emission tomography (PET) and computed tomography (CT) to study eight patients with homonymous hemianopias or quadrantanopias due to ischemic lesions of the visual pathways. Four patients with ischemic damage to all or part of the occipital lobe had decreased glucose metabolism in the affected region. Three patients with ischemic damage limited to the optic radiations had decreased glucose metabolism in the portion of striate cortex appropriate for the visual field defect. Changes in glucose metabolism frequently occurred in the undamaged ipsilateral thalamus and visual association areas.


Behavioural Brain Research | 1994

The spatial relationship between the cerebral cortex and fiber trajectory through the corpus callosum of the cat

Stephen G. Lomber; Bertram R. Payne; Alan C. Rosenquist

We related fiber trajectory through the feline corpus callosum to the site of fiber origin in the cortical mantle and to functional modality. The cortical fields which contribute axons to the different portions of the corpus callosum were revealed by applying horseradish peroxidase (HRP) to the cut ends of selected groups of callosal axons in twelve adult cats. Overall, the application of HRP at progressively more caudal positions in the corpus callosum labels fields of neurons at successively more caudal positions in the cerebral cortex. Comparison of these data to functionally distinct cortical zones shows that the callosal body conveys a mixture of fibers arising from functionally diverse regions of the cerebrum, whereas portions of the rostral and caudal ends appear to be essentially unimodal, conveying motor and visual signals, respectively.

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Larry A. Palmer

University of Pennsylvania

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Denis Raczkowski

University of Pennsylvania

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Steven F. Wallace

University of Pennsylvania

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Vivian M. Ciaramitaro

University of Massachusetts Boston

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Abass Alavi

Hospital of the University of Pennsylvania

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James M. Sprague

University of Pennsylvania

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L. A. Palmer

University of Pennsylvania

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Laura L. Symonds

University of Pennsylvania

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Martin Reivich

University of Pennsylvania

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R. J. Tusa

University of Pennsylvania

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