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H Sherk

Publications and source records attributed to H Sherk.

At least 37 records · Page 2Linked to original sources
PubMed1986

Location and connections of visual cortical areas in the cat's suprasylvian sulcus.

The initial aim of the experiments described here was to identify and quantify the cortical and thalamic connections of visual cortical areas located in the vicinity of the suprasylvian sulcus. Inputs to various sites in this region were studied by making small injections of wheat germ agglutinin (conjugated to horseradish peroxidase) at physiologically identified locations. Retrogradely labeled cells were counted in each identifiable area of cortex and in thalamic nuclei. Some injections yielded quantitatively similar distributions of labeled cells, and it is suggested that such evidence provides a useful way of dividing the cortex into areas. By this criterion, a single, relatively large, cortical area was identified that occupied most of the medial bank of the suprasylvian sulcus, all or most of its posterior bank, and a small segment of its lateral bank. It was referred to as the Clare-Bishop area. Because neighboring visual areas were found to lack input from area 17, while the Clare-Bishop area received a strong striate input, its boundaries were investigated by labeling afferents from area 17. Together with the results of retrograde tracer injections, these data suggested that the Clare-Bishop area cuts across several of the visual areas defined physiologically by Tusa et al. ('81). As a consequence, its retinotopic organization must be relatively complex, with duplications of some parts of the visual field. Three other visual areas were tentatively identified on the basis of their distinctive connections. One was situated on the lateral bank of the suprasylvian sulcus and appeared to border the Clare-Bishop area laterally. Another, referred to as area 21, lay adjacent to area 19, and, for part of its length, also appeared to bound the Clare-Bishop area. The third, corresponding approximately to Heath and Jones's ('71) posterior suprasylvian region, lay lateral and anterior to the Clare-Bishop area in the depths of the posterior suprasylvian sulcus.

Animals↗
PubMed1984

Scintigraphic detection of prosthetic joint and soft tissue sepsis secondary to tuberculosis.

In a 40-year-old Hispanic woman with pain and swelling in the left knee with a prosthesis, the combination of Ga-67 citrate and Tc-99m methylene diphosphonate (MDP) scans was used to indicate that there was a septic prosthetic joint. At surgery, the joint was infected and a foreign body was found. Cultures positive for tuberculosis were found also. The presence of an incongruent Ga-67 and Tc-99m (MDP) scan pattern suggests infection of the prosthetic joint, as in the following case.

Adult↗
PubMed1984

Receptive field properties in the cat's lateral geniculate nucleus in the absence of on-center retinal input.

In the cat, lateral geniculate neurons and retinal ganglion cells can almost all be categorized as on-center (excited by light stimuli) or off-center (excited by dark stimuli). We have investigated how these cells are affected when a drug is applied to the retina that, in the mudpuppy, inactivates on-bipolar cells (Slaughter, M. M., and R. F. Miller (1981) Science 211: 182-185). This drug, D,L-2-amino-4-phosphonobutyric acid (APB), is an analogue of glutamate. After injecting APB into the vitreous of the eye, we could record in the optic tract from fibers of off-center retinal ganglion cells that appeared normal in their responses, but we could find no fibers from on-center cells in the injected eye. In the lateral geniculate nucleus (LGN), the outcome was similar. Of a sample of 144 cells studied quantitatively, 13 had extremely poor responses and could not be characterized as on-or off-center. The remaining 131 cells had off-centers and appeared largely normal. Their receptive field organization was unaltered: the field center was excited by dark (off) stimuli and inhibited by light, whereas the surround was inhibited by off stimulation. Of particular interest was the fact that the surrounds of many off-center cells could still be excited by light stimuli; thus, despite the probable inactivation of on-bipolar cells, not all on-responses in the LGN were abolished. As a group, off-center cells were somewhat less responsive then in control experiments. Except for this change, APB appeared to affect only on-center cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Receptive field properties in the cat's area 17 in the absence of on-center geniculate input.

Most neurons of area 17 in the cat respond to both light and dark stimuli, and it is often assumed that these responses originate from the on-center and off-center cells, respectively, of the lateral geniculate nucleus. This has not been demonstrated experimentally, however. Whether the on and off pathways make unique contributions to some of the response properties characteristic of visual cortex, such as orientation selectivity, is also unknown. The aim of these experiments was to investigate these questions by inactivating the retinogeniculate on pathway. In cats in which D,L-2-amino-4-phosphonobutyric acid (APB) had been injected into one eye, we found that, in the geniculate layers driven by that eye, there were no cells with on-center responses (Horton, J. C., and H. Sherk (1984) J. Neurosci. 4: 374-380). The on pathway appeared to have been inactivated. To see how cortical receptive fields were affected, we examined 184 binocular cells in area 17 contralateral to the injected eye. Each cell still had a normal receptive field in the ipsilateral eye, and we compared the cell's response properties in that eye with those in the eye injected with APB to assess the drug's effects. Overall responsiveness in the injected eye was severely reduced, and responses to the onset of stationary light stimuli were almost entirely abolished. Responses to moving light edges were weak or absent in most cells but still strong in a few; simple cells tended to have more vigorous light edge responses than complex cells. The general reduction in responsiveness, and the specific reduction in light edge responses, indicated that the on and off pathways both contribute (directly or indirectly) to the responses of most cells in area 17. The remaining responses to light edges we think originated mainly from the on-surrounds of off-center geniculate cells. Responses to moving dark edges were somewhat depressed compared to those in the normal eye. There was, however, no systematic change in direction selectivity and no reduction in specificity for orientation or length. In general, receptive field properties remained surprisingly normal despite the conspicuous reduction in responsiveness.

Animals↗
PubMed1983

Retrograde transport of [3H]proline: a widespread phenomenon in the central nervous system.

[3H]Proline was injected into spinal cord, pons, inferior colliculus, superior colliculus, lateral geniculate nucleus, pulvinar-LP complex and visual cortex of cats or rats. After 1-3 days' survival the animals were perfused with formalin or mixed aldehydes. Autoradiography showed labeling of cell bodies in most regions known to project to the injection sites. The ability to take up and retrogradely transport [3H]proline appears to be a common property of central neurons. We infer that the transport of this compound is unrelated to its possible status as a neurotransmitter.

Animals↗
PubMed1983

Contribution of the cortico-claustral loop to receptive field properties in area 17 of the cat.

The contribution of the cat's claustrum to the response properties of cells in area 17 was studied by destroying the left claustrum and examining receptive field properties of cells in both the left and right area 17. For each cell we assessed sharpness of orientation tuning, degree of direction selectivity, length summation, end-stopping, ocular dominance, responsiveness, and several other properties. On the lesioned side, 462 cells were studied, and on the control side, 636 cells. All cats showed a reduction in the number of end-stopped cells in area 17 on the side of the lesion. This was particularly marked in layers 2 + 3 and 4, where end-stopped cells are normally most abundant. In the control hemisphere, 43% of the sample from these layers showed at least moderate end-stopping whereas, in contrast, only 21% exhibited this degree of end-stopping on the side of the lesion. There was no obvious change in other response properties. We conclude that one function of the cat's claustrum is to help regulate the length selectivity of cells in area 17.

Animals↗
PubMed1981

Visual claustrum: topography and receptive field properties in the cat.

A region containing visually responsive cells was found in the dorsocaudal claustrum. This area contains a single orderly map of the contralateral visual field. Like cortical cells, most claustral cells are selective for stimulus orientation. They are binocular, and they respond to either direction of movement and to a broad range of velocities. Their most striking property is a marked preference for very long stimuli.

Animals↗
PubMed1981

The visual claustrum of the cat. I. Structure and connections.

The cat's dorsocaudal claustrum was studied in Golgi preparations, by electron microscopy, and by anterograde and retrograde tracer techniques. It receives a convergent retinotopic projection from several visual cortical ares, including areas 17, 18, 19, 21a and PMLS (posteromedial lateral suprasylvian area). The projection arises from spiny dendrite cells (pyramidal and fusiform) in the middle of cortical layer VI. As shown by a double label experiment, they form a separate population from those projecting to the lateral geniculate nucleus. There are also inputs from the lateral hypothalamus, from the nucleus centralis thalami, and probably from the locus coeruleus, but not from the sensory nuclei of the thalamus. Non-visual cortical areas do not project to the visual claustrum, but many of them are connected to other parts of the nucleus. For example, the splenial (cingulate) gyrus projects to a claustral zone just ventral to the visual area, and regions anterior to the visual area are connected with somatosensory and auditory cortex. The commonest cell type in the claustrum is a large spiny dendrite neuron whose axon leaves the nucleus after giving off local collaterals. Small spine-free cells, with beaded dendrites and a locally arborizing axon, are found also. Electron microscopy of the claustrum after ablation of the visual cortex showed degenerating type 1 axon terminals synapsing on spines and beaded dendrites, suggesting a direct cortical input to both cell types. The visual claustrum projects back to the visual cortex, to the same areas from which it receives an input. The return projection is predominantly ipsilateral, but there is, in addition, a small crossed projection. The claustrocortical axons terminate in all cortical layers but most heavily in layers IV and VI. The majority of the cells in the visual claustrum project to the cortex, and retinotopy is maintained throughout the entire corticoclaustral loop. No subcortical projections from the claustrum could be identified.

Afferent Pathways↗
PubMed1981

The visual claustrum of the cat. II. The visual field map.

Physiological and anatomical methods were used to study the representation of the visual field in the cat's dorsocaudal claustrum. In one set of experiments, the visual receptive fields of claustral neurons were plotted in multiple electrode penetrations. In another set of experiments, the termination of the corticoclaustral pathway was examined autoradiographically after the injection of [3H]proline at retinotopically defined sites in the visual cortex. Results obtained by the two methods were in close agreement. The claustrum was found to contain a single, orderly map of the contralateral hemifield and a small part of the ipsilateral field. High elevations are represented caudally and ventrally, low elevations rostrally and dorsally. The surface of the claustrum represents the periphery of the visual field, while the vertical meridian lies more ventrally, where the visual claustrum abuts the non-visual part of the nucleus. Visual field lines (isoazimuths or isoelevations) are represented as planes in the claustrum. The map is unusual in that isoazimuth planes are strongly curved and nested within each other, with peripheral ones enclosing those closer to the vertical meridian. This arrangement permits an expanded representation of the periphery compared with what is seen in visual cortex. The inputs from areas 17, 18, 19, 21a, and PMLS (posteromedial lateral suprasylvian area) are convergent, each projection retinotopically to the entirety of the claustral map.

Animals↗
PubMed1981

The visual claustrum of the cat. III. Receptive field properties.

The visual response properties of cells in the cat's dorsocaudal claustrum were studied physiologically. Quantitative observations were made of 55 cells, and qualitative observations were made on 228 others. The claustral cells formed a physiologically homogeneous population. The overwhelming majority were orientation selective, and most also showed a striking preference for long stimuli, their responses summating up to lengths of 40 degrees or more. Moving stimuli were always much more effective than stationary ones. In other respects, claustral cells were tolerant of wide variation in stimulus features. Their responses were about equally brisk to either direction of movement of a properly oriented stimulus, and the velocity of movement was likewise not critical. They appeared not to summate across the dimension of their receptive fields orthogonal to the preferred orientation so that narrow or broad slits, or edges, evoked similar responses. Dark slits on light backgrounds were as effective as light slits on dark backgrounds. Finally, a large majority of cells were driven equally well by either eye. These properties of claustral cells differ in several respects from those of their principal targets, cells in layer IV of visual cortex.

Animals↗
PubMed1979

A comparison of visual-response properties in cat's parabigeminal nucleus and superior colliculus.

1. The visual-response properties of single cells in the cat's superior colliculus and parabigeminal nucleus were compared. In the colliculus, 151 cells (restricted to the upper layer) were studied, and in the parabigeminal nucleus, 134 cells. 2. Response characteristics in the two structures were similar in many respects: among these were receptive-field size, ocular dominance, and lack of specificity for stimulus shape and contrast (light versus dark). 3. Quantitatively, there were some significant differences between the two populations of cells. Parabigeminal neurons tended to respond more brisky and reliably, while being less selective for those stimulus parameters tested (size, velocity, and direction of movement). Spontaneous activity was much higher in the parabigeminal nucleus than in the colliculus. Finally, parabigeminal cell responses to stationary stimuli were somewhat brisker than those of tectal cells. 4. These data suggest that a physiologically distinct population of tectal cells sends input to the parabigeminal nucleus, probably with some convergence on individual cells.

Animals↗
PubMed1979

Connections and visual-field mapping in cat's tectoparabigeminal circuit.

1. The aim of these experiments was to analyze the organization of the reciprocal connections between the cat's superior colliculus and parabigeminal nucleus. Both physiological and anatomical techniques were employed. 2. A population of cells in the superficial gray and upper optic layers of the colliculus was labeled retrogradely by horseradish peroxidase injections into the parabigeminal nucleus. No other sources of input to the nucleus were found in the brain stem or diencephalon. 3. A map of the visual field within the parabigeminal nucleus was reconstructed by plotting visual receptive fields at 350 parabigeminal sites with microelectrodes. The map resembled that found in the colliculus, although it was considerably less orderly. The entire contralateral visual field was represented and, in addition, roughly the central 40 degrees of the ipsilateral hemifield was included; futhermore, the expansion of the central visual field was similar to that of the tectal map. 4. The return parabigeminal projections to the caudal parts of the two colliculi, representing the contralateral hemifields, were in register with the tectal visual-field maps. In contrast, the parabigeminal pathways to the anterior segments of the two colliculi, representing part of the ipsilateral visual fields, were not clearly topographic. The projection to this part of the contralateral colliculus showed little order, while that to the ipsilateral colliculus was extremely sparse. 5. A single site in the colliculus can be the target of axons from nonhomologous locations in the two parabigeminal nuclei; so that both parabigeminal inputs are in register with the tectal map.

Animals↗
PubMed1978

Area 18 cell responses in cat during reversible inactivation of area 17.

1. A region of area 17 in the cat was temporarily inactivated by cooling, and cells in a topographically corresponding part of area 18 were studied during the blockage of area 17 input. 2. The responses of most area 18 cells were markedly reduced by cooling area 17 and recovered on rewarming primary visual cortex. 3. The selectivity of area 18 cells for oriented stimuli was not affected by inactivating area 17. These cells also, in general, retained their selectivities for the direction of stimulus movement and for the sign of contrast (light or dark) of a moving edge in the absence of input from area 17. 4. There was a greater decrease, on the average, of area 18 cell responses to slowly moving stimuli than to rapidly moving stimuli when area 17 was cooled; however, the exact pattern of change varied considerably from cell to cell. 5. These results suggest that cells in area 18 are to some degree dependent on input from area 17 for their responses, but to a large extent are independent in their selectivity for those stimulus parameters (orientation, direction of movement, sign of contrast) studied.

Animals↗
PubMed1978

Physiological consequences for the cat's visual cortex of effectively restricting early visual experience with oriented contours.

1. The early visual experience of nine cats was restricted to viewing horizontal or vertical lines inside opaque goggles. 2. When the kittens were 3-4 mo old, extracellular recordings were made in the primary visual cortex. To obtain a representative sample of cortical cells, units were studied at regularly spaced intervals along the course of electrode penetrations traveling oblique to the cortical surface. An automated assessment of preferred orientation using a computer-driven optical display was employed, and during the recording session the experimenters did not know which orientation(s) each animal had viewed in early life. 3. In the cats that viewed horizontal lines with one eye and vertical lines with the other during rearing, two major findings of previous workers (14) were confirmed. First, a majority of units were not selective for orientation. Second, units with preferred orientations near vertical tended to be activated exclusively by the eye that had viewed vertical, and likewise for horizontal. 4. In cats that viewed lines of the same orientation with both eyes during rearing, a substantially smaller proportion of units were selective for orientation; the preferred orientations of these units also tended to match the orientation to which the cats had been exposed. 5. Portions of some electrode penetrations showed an orderly arrangement of cells according to preferred orientation similar to that seen in normal cats, but with regions over which only nonselective cells were found. Many penetrations appeared less orderly. 6. The results are consistent with a role for early visual experience in maintaining the responsiveness and innate selectivity of cortical neurons, although they cannot entirely rule out the possibility that experience may alter or determine the preferred orientation of some cells.

Animals↗
PubMed1976

Quantitative study of cortical orientation selectivity in visually inexperienced kitten.

1. Extracellular recordings were made from single units in the visual cortices of six kittens deprived of experience with pattern vision by binocular lid suture. 2. Selectivity for stimulus orientation was quantitatively assessed in 98 units; 90 responded selectively to the orientation of a moving bar stimulus, the remainder responding nonselectively or too poorly to classify. Cells in these visually inexperienced kittens were similar in their degree of selectivity for orientation to cells tested in adult cats. However, responses tended to be weaker and somewhat more erratic. 3. About half the cells in this simple responded to both directions of stimulus motion at the optimal orientation. Most of those responding to only one direction of motion were considered orientation rather than direction selective because they responded more strongly or more selectively to a moving bar than to a moving spot. 4. Cells appeared to be organized within the cortex in a pattern similar to that found in adult cats, with cells in one column selective for the same orientation, and adjacent column having similar preferred orientations. 5. It is concluded that selectivity for stimulus orientation in the cat's visual cortex is innately determined.

Animals↗
PubMed1975

Modification of cortical orientation selectivity in the cat by restricted visual experience: a reexamination.

Recent reports have stated that the orientation selectivity of cells in the cat's visual cortex can be biased by limiting the early visual environment to stripes of one orientation. Data obtained from seven kittens using systematic and quantitative sampling of preferred orientation, together with a blind procedure, do not show a bias toward the orientation presented in one type of restricted rearing environment.

Animals↗
PubMedDate not supplied

A reassessment of the lower visual field map in striate-recipient lateral suprasylvian cortex.

Lateral suprasylvian visual cortex in the cat has been studied extensively, but its retinotopic organization remains controversial. Although some investigators have divided this region into many distinct areas, others have argued for a simpler organization. A clear understanding of the region's retinotopic organization is important in order to define distinct areas that are likely to subserve unique visual functions. We therefore reexamined the map of the lower visual field in the striate-recipient region of lateral suprasylvian cortex, a region we refer to as the lateral suprasylvian area, LS. A dual mapping approach was used. First, receptive fields were plotted at numerous locations along closely spaced electrode penetrations; second, different anterograde tracers were injected at retinotopically identified sites in area 17, yielding patches of label in LS. To visualize the resulting data, suprasylvian cortex was flattened with the aid of a computer. Global features of the map reported in many earlier studies were confirmed. Central visual field was represented posteriorly, and elevations generally shifted downward as one moved anteriorly. Often (though not always) there was a progression from peripheral locations towards the vertical meridian as the electrode moved down the medial suprasylvian bank. The map had some remarkable characteristics not previously reported in any map in the cat. The vertical meridian's representation was split into two pieces, separated by a gap, and both pieces were partially internalized within the map. Horizontal meridian occupied the gap. The area centralis usually had a dual representation along the posterior boundary of the lower field representation, and other fragments of visual field were duplicated as well. Finally, magnification appeared to change abruptly and unexpectedly, so that compressed regions of representation adjoined expanded regions. Despite its complexity, we found the map to be more orderly than previously thought. There was no clearcut retinotopic basis on which to subdivide LS's lower field representation into distinct areas.

Animals↗