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H M Petry

Publications and source records attributed to H M Petry.

15 recordsLinked to original sources
PubMed1992

Immunohistochemical organization of the ventral lateral geniculate nucleus in the ground squirrel.

The ventral lateral geniculate nucleus (vLGN) of the thirteen-lined ground squirrel (Citellus tridecemlineatus) is a highly differentiated nucleus that is divisible into five major subdivisions on the basis of retinal projections and cytoarchitecture. To pursue the likelihood that these subdivisions (the dorsal cap, intergeniculate leaflet, external magnocellular lamina, internal magnocellular lamina, and parvicellular segment) correlate with the functional diversity of this complex, the present study examined the neurochemical composition of the vLGN with regard to substances that have previously proved useful in distinguishing functionally distinct subregions within nuclei (i.e., neuropeptide Y (NPY), substance P (SP), leucine and methionine enkephalins, gamma-aminobutyric acid (GABA), cytochrome oxidase (CO), acetylcholinesterase (AChE), and NADPH-diaphorase). The results showed a clear differential neurochemical distribution within the nucleus. Neuropeptide Y immunoreactive perikarya were found predominantly in the intergeniculate leaflet and external magnocellular lamina, with only a few present in the internal magnocellular lamina and dorsal cap, and none observed in the parvicellular segment. NPY+ fibers, however, were present in all divisions except the parvicellular segment. The highest concentration of SP immunoreactive cells was observed in the internal magnocellular lamina, and substantial numbers also were scattered in the external magnocellular lamina and parvicellular segment. SP+ fibers were seen predominantly in the intergeniculate leaflet and the magnocellular laminae. The heaviest concentration of enkephalinergic fibers occurred in the internal magnocellular lamina and dorsal cap, but fibers were also observed in the external magnocellular lamina and intergeniculate leaflet. GABA reactivity was widespread throughout the vLGN, with the dorsal cap and external magnocellular lamina most heavily labeled, followed by the intergeniculate leaflet and the internal magnocellular lamina. Cytochrome oxidase, AChE, and NADPH-diaphorase histochemistry revealed rich reactivity within the dorsal cap, and external and internal magnocellular laminae and paler reactivity in the intergeniculate leaflet and parvicellular segment. The external magnocellular lamina was more reactive for CO and NADPH-diaphorase than AChE, while the internal magnocellular lamina showed the opposite pattern of reactivity. In addition, NADPH-diaphorase reactive cells were present in caudal intergeniculate leaflet and lateral external magnocellular lamina. These local differences in the neurochemical character of the vLGN support its parcellation into multiple subdivisions. Taken in conjunction with the differences in cytoarchitecture and retinal projections, these results suggest substantial functional diversity within the ventral lateral geniculate complex.

Acetylcholinesterase↗
PubMed1992

Immunohistochemical organization of the ventral lateral geniculate nucleus in the tree shrew.

The ventral lateral geniculate nucleus (vLGN) of the tree shrew (Tupaia belangeri) was differentiated into multiple subdivisions (dorsal cap, intergeniculate leaflet, parvicellular segment, and internal and external magnocellular laminae, the latter being further divisible into a lateral and medial division) on the basis of retinal projections, immunochemistry, and histochemistry. Retinal projections traced with intravitreal injections of wheat germ agglutinin conjugated horseradish peroxidase revealed direct bilateral input to all subregions of the vLGN, except for the internal magnocellular lamina (which received only contralateral input) and the parvicellular segment (which was not retinorecipient). Furthermore, retinal inputs clearly distinguished the relatively heavily retinorecipient intergeniculate leaflet from the less prominently labeled dorsal cap. Immunohistochemical localization of Neuropeptide Y (NPY) perikarya revealed their prominence in the intergeniculate leaflet and the external magnocellular laminae with a concentration along the optic tract. NPY immunoreactive fibers were seen in all but the parvicellular subregion. Gamma amino butyric acid immunoreactivity was seen throughout the vLGN, but was most concentrated in the dorsal cap and the magnocellular laminae, followed by the intergeniculate leaflet. Histochemical studies of cytochrome oxidase and nicotinamide adenosine dinucleotide phosphate (NADPH)-diaphorase localization revealed similar patterns of dense reactivity within the external magnocellular lamina, intergeniculate leaflet and dorsal cap, and somewhat less dense, but substantial reactivity in the internal magnocellular lamina. Within the external magnocellular lamina, cells reactive for cytochrome oxidase were noted in the lateral portion bordering the optic tract, whereas those specific for NADPH-diaphorase were dispersed throughout the lamina. Poor reactivity for both histochemical markers was evident in the parvicellular segment. Overall, the markedly different patterns of retinal input and neurochemical organization between the subdivisions of the tree shrew vLGN suggest their involvement in diverse functions. Furthermore, the basic similarity of the organization of the tree shrew vLGN to that of the taxonomically unrelated ground squirrel may indicate a common mammalian scheme.

Animals↗
PubMed1991

Psychophysical measurement of spectral sensitivity and color vision in red-light-reared tree shrews (Tupaia belangeri).

The role of the spectral lighting environment on the post-natal development of spectral sensitivity and color vision was studied in tree shrews (Tupaia belangeri) that were born and reared to adulthood in cyclic red light. Normal tree shrews are dichromats, possessing short-wavelength-sensitive (SWS) and long-wavelength-sensitive (LWS) cone receptors and a small population of rods. Red-light-rearing (RLR) produced differential stimulation of the cone types by effectively eliminating photic stimulation of the SWS cones, without depriving the LWS cones. Spectral sensitivity and color vision were measured behaviorally for RLR shrews and normal shrews under different ambient light levels. Spectral sensitivity functions were deutan-like, exhibiting maxima at ca 450 and 550 nm and a minimum at 510 nm. No significant differences in spectral sensitivity were observed between RLR and control animals. Furthermore, all animals demonstrated deutan-type dichromatic color vision evidenced by their ability to discriminate monochromatic lights from equally-bright achromatic lights except for a "neutral point" near 505 nm. These results demonstrate that a population of functional SWS cones survived the lack of post-natal photic stimulation. However, RLR shrews differed from controls in that they were poorer at making chromatic/achromatic discriminations. While no severe disorganization of color vision was evident, the poorer discrimination displayed by the RLR animals is likely the result of changes in post-receptoral visual mechanisms.

Animals↗
PubMed1991

Green-sensitive cone photoreceptors are selectively labeled by Procion yellow dye in goldfish retina.

Selective labeling of intravitreal Procion yellow dye by presumed blue-sensitive cone photoreceptors has been demonstrated in primate retina. To determine whether Procion yellow is selective for this cone type in an unrelated vertebrate species, labeling by this dye was studied in goldfish retina, where cone pigment type can be directly inferred from photoreceptor morphology. At low vitreal concentrations of the dye (less than 0.4%), only cone outer segments were labeled. At vitreal concentrations of 0.4-0.5%, the inner segments of short-double cones and a subset of long single cones (presumed green-sensitive cones) were selectively stained. At still higher vitreal concentrations (0.6-0.7%), the inner segments of short-single cones and miniature short-single cones (presumed blue-sensitive cones) showed evidence of Procion label, but were not as heavily labeled. The inner segments of long-double cones and a subset of long-single cones (presumed red-sensitive cones) did not label at any of these concentrations. These results show that Procion yellow is not a selective marker for blue-sensitive cones in the goldfish retina. In addition, stained rod and cone nuclei were observed at each dye concentration, including those concentrations at which no inner segments were labeled.

Animals↗
PubMed1990

Visual pigments of the tree shrew (Tupaia belangeri) and greater galago (Galago crassicaudatus): a microspectrophotometric investigation.

Optical density, linear dichroism and bleaching difference spectra were measured in photoreceptors from the cone-dominated retina of the tree shrew (Tupaia belangeri) and from the rod-dominated retina of the greater galago (Galago crassicaudatus) using a single-beam, wavelength-scanning, dichroic microspectrophotometer. In Tupaia, we obtained spectral records from 272 cone receptors (from 10 eyes), of which 264 were long-wave sensitive (lambda max = 555 +/- 6 nm) and 8 were short-wave sensitive (lambda max = 428 +/- 15 nm). Also, one anatomically-recognizable rod receptor was encountered and showed a peak absorption at approx. 496 nm. No mid-wave sensitive cone pigment was found, as would be expected in deutan-type dichromats like the tree shrew. Pre-retinal absorption by the cornea and lens was maximal at 370 nm and negligible beyond 430 nm. In Galago, all outer segments measured were rod-like in appearance (lambda max near 501 nm). Measurements of pre-retinal absorption yielded a single-peaked function with a maximum at 363 nm.

Absorption↗
PubMed1989

Striped pattern of labeling in ground squirrel superior colliculus following intraocular HRP injections.

In the 13-lined ground squirrel (Citellus tridecemlineatus), intravitreal injections of horseradish peroxidase (HRP) or wheat germ-agglutinated HRP (WGA-HRP) tracers produced a striped pattern of labeling in the contralateral superficial gray (SGS) of the superior colliculus in most, but not all, cases. The stripes extended dorsoventrally throughout the SGS in a rostral-medial to caudal-lateral orientation. In general, the striped labeling was more distinct and was observed more frequently with the HRP, rather than the WGA-HRP, tracer.

Animals↗
PubMed1989

Retinal projections in the ground squirrel (Citellus tridecemlineatus).

The retinal projections of the thirteen-lined ground squirrel were determined by tracing anterograde transport of intravitreally injected horseradish peroxidase (HRP) or wheat-germ conjugated horseradish peroxidase (WGA-HRP). Label was seen in the suprachiasmatic nucleus and adjacent anterior hypothalamic area, the accessory optic system (the medial, dorsal, and lateral terminal nuclei), the dorsal and ventral lateral geniculate nuclei, the intergeniculate leaflet, the pretectal nuclei (the anterior, posterior, and olivary pretectal nuclei and the nucleus of optic tract), and the superior colliculus. Most of these structures were labeled bilaterally, with dense contralateral label and sparse ipsilateral label, a pattern typical for animals with laterally placed eyes. However, the suprachiasmatic nucleus and the nucleus of the optic tract received input only from the contralateral eye. In contrast to previous degeneration studies, the sensitive HRP tracers (in conjunction with cytochrome-oxidase reactivity) revealed an elaborate organization within the lateral geniculate nucleus (dorsal LGN, ventral LGN, and intergeniculate leaflet) that is consistent with existing organizational schemes for other mammalian species.

Animals↗
PubMed1988

Contrast-sensitivity functions of W-, X-, and Y-like relay cells in the lateral geniculate nucleus of bush baby, Galago crassicaudatus.

1. This paper represents a continuation of our effort to examine the relationship between the physiology of distinct classes of primate lateral geniculate nucleus (LGN) cells and spatial vision. The present study focuses on modeling the contrast-sensitivity functions (CSFs) of separate LGN cell classes, examining differences in the CSFs of different classes of LGN cells and comparing the results with behaviorally defined CSFs. 2. CSFs to drifting sinusoidal gratings were obtained from single LGN relay cells in the nocturnal primate, Galago crassicaudatus. The CSFs of 14 X-like, 27 Y-like, and 6 W-like cells with standard center-surround organization were well fit by a difference of Gaussians (DOG) model with small residual errors (mean error per data point +/- SEM = 0.008 +/- 0.002). The larger residual errors shown by a few of the Y-like cells were not due to nonlinearity of spatial summation. 3. The CSFs of eight cells that appeared to have nonstandard center-surround organization (primarily, a silent, suppressive surround) were also well fit by the DOG model. 4. The DOG curves that best fitted the data differed considerably between the three groups. As a group, X-like cells had a small center mechanism (Rc = 0.19 degrees) with high sensitivity (Kc = 76.53) and a small, sensitive surround (Rs = 0.71 degrees; Ks = 5.50). These parameters produced CSFs with high cutoff frequencies (Vcutoff = 2.5 c/deg) and low peak sensitivities (CSpk = 6.1) that occurred at 0.8 c/deg. 5. Y-like cells had a large center mechanism (Rc = 0.46 degrees) with low sensitivity (Kc = 21.16) and a large, insensitive surround (Rs = 2.38 degrees; Ks = 0.81). These parameters produced CSFs with lower cutoff frequencies (Vcutoff = 1.2 c/deg) and higher peak sensitivities (CSpk = 12.5) that occurred at 0.2 c/deg. 6. The few W-like cells that responded to gratings well enough to determine a CSF were quite variable. As a group they had a large center mechanism (Rc = 0.38 degrees) with intermediate sensitivity (Kc = 34.55) and a surround with intermediate size and sensitivity (Rs = 1.59 degrees; Ks = 1.59). These produced CSFs with intermediate cutoffs (Vcutoff = 1.6 c/deg) and low peak sensitivities (CSpk = 5.0) occurring at 0.4 c/deg.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

A retinal smear technique for varying grating contrast.

We present here a technique for modulating contrast in gratings seen in Maxwellian-view or on a projection screen. The method can be used with achromatic or chromatic grating stimuli. It is based on a high frequency oscillatory displacement of the grating image, which in turn produces a smearing of the image on the observer's retina. The waveform of the displacement and its amplitude determine the appearance and contrast of the image produced on the retina.

Form Perception↗
PubMed1985

A method for determining threshold from single-unit neural activity.

A computationally straightforward method is described for determining the latency, duration and magnitude of stimulus-evoked single-unit neural activity. A unique feature of the method is its ability to define the neural response without reference to stimulus parameters. First, the temporal component of the spike train that represents the response is located and then that component is analyzed to determine the magnitude of the response. Intensity-response functions can then be constructed, using the number of extra spikes above baseline activity as a measure of response magnitude. Threshold can be defined as any point on the intensity-response function.

Action Potentials↗
PubMed1984

Spatial contrast sensitivity of the tree shrew.

Spatial contrast sensitivity functions (CSFs) were measured for 3 tree shrews. Our two-alternative forced-choice discrimination paradigm required the animals to discriminate a vertical sine-wave luminance grating from a homogeneous field of the same size (16 degrees) and mean luminance (35 cd/m2). Spatial frequencies tested ranged from 0.1 to 2.0 c/deg and grating contrast was varied trial-by-trial using a modified staircase technique. Small between-subject variations in the shape of the CSFs appeared to be correlated with our estimates of refractive error for each animal. In general, the CSFs were of the typical band-pass type with peak sensitivity occurring at approximately 0.7 c/deg. Estimates of grating acuity derived from the CSFs ranged from 1.2 to 2.4 c/deg and are within the limitations set by the eye size and retinal anatomy of the tree shrew.

Animals↗
PubMed1982

Changes in the human visually evoked cortical potential in response to chromatic modulation of a sinusoidal grating.

Human visually evoked cortical potentials (VECPs) were recorded from 4 subjects in response to the counterphase alternation of an equal brightness chromatic grating pattern. The pattern was constructed from 2 monochromatic sinusoidal gratings registered 180 deg out of phase. Eleven wavelengths from 450 to 650 nm (at 20 nm intervals) were used. Each wavelength was paired in the grating stimulus with every other to produce a total of 55 different chromatic gratings. The chromatic modulation depth (contrast) of each grating was varied and resulting VECPs were recorded. VECP amplitude was found to vary linearly with log chromatic modulation depth. VECP threshold values were inferred by extrapolation of linear regression lines to zero VECP amplitude. Chromatic modulation sensitivity functions were derived and a multidimensional scaling analysis of the data for each subject was performed. The data were adequately described by a two-dimensional geometric configuration of the 11 wavelengths used. The configurations were similar in shape to those obtained psychophysically by Butler and Riggs (1978) Vision Res. 18, 1407-1416, who used a similar stimulus pattern. Their shapes are consistent with an opponent-color model of color vision.

Adult↗
PubMed1977

Organizational determinants of subjective contour: the subjective Necker cube.

With specially arranged inducing elements on a white surface of uniform luminosity, a phenomenally complete Necker cube can be seen in any array where only the 'corners' of the cube are physically represented. The subjectively seen bars of the cube disappear when the inducing 'discs' are seen as 'holes' in an interposing surface, through which the corners of a partially occluded cube are viewed. Illusory brightness effects are also observed in connection with the different organizations of this ambiguous figure.

Cues↗