bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adaptation in single units in visual cortex: The tuning of aftereffects in the spatial domain
Authors: Saul A. B. , Cynader M. S. 
Published: June 2009

AbstractCat striate cortical neurons were investigated using a new method of studying adaptation aftereffects. Stimuli were sinusoidal gratings of variable contrast, spatial frequency, and drift direction and rate. A series of alternating adapting and test trials was presented while recording from single units. Control trials were completely integrated with the adapted trials in these experiments.Every cortical cell tested showed selective adaptation aftereffects. Adapting at suprathreshold contrasts invariably reduced contrast sensitivity. Significant aftereffects could be observed even when adapting at low contrasts.The spatial-frequency tuning of aftereffects varied from cell to cell. Adapting at a given spatial frequency generally resulted in a broad response reduction at test frequencies above and below the adapting frequency. Many cells lost responses predominantly at frequencies lower than the adapting frequency.The tuning of aftereffects varied with the adapting frequency. In particular, the strongest aftereffects occurred near the adapting frequency. Adapting at frequencies just above the optimum for a cell often altered the spatial-frequency tuning by shifting the peak toward lower frequencies. The fact that the tuning of aftereffects did not simply match the tuning of the cell, but depended on the adapting stimulus, implies that extrinsic mechanisms are involved in adaptation effects.
Adaptation in single units in visual cortex: The tuning of aftereffects in the temporal domain
Authors: Saul A. B. , Cynader M. S. 
Published: June 2009

AbstractAdaptation-induced changes in the temporal-frequency tuning and direction selectivity of cat visual cortical cells were studied. Aftereffects were induced largely independent of direction. Adapting in either direction reduced responses in both directions. Aftereffects in the direction opposite that adapted were only slightly weaker than were aftereffects in the adapted direction. No cell showed any enhancement of responses to drifting test stimuli after adapting with moving gratings. Adapting in a cell's null direction usually had no effect. Dramatic differences between the adaptation characteristics of moving and stationary stimuli were observed, however.Furthermore, aftereffects were temporal frequency specific. Temporal frequency-specific aftereffects were found in both directions: adapting in one direction induced frequency-specific effects in both directions. This bidirectionality of frequency-specific aftereffects applied to the spatial domain as well. Often, aftereffects in the direction opposite that adapted were more narrowly tuned.In general, adaptation could shift a cell's preferred temporal frequency. Aftereffects were most prominent at high temporal frequencies when testing in the adapted direction. Aftereffects seemed to be more closely linked to temporal frequency than to velocity matching.These results constrain models of cortical connectivity. In particular, we argue against schemes by which direction selectivity is generated by inhibiting a cell specifically when stimulated in the nonpreferred direction. Instead, we argue that cells receive bidirectional spatially and temporally tuned inputs, which could combine in spatiotemporal quadrature to produce direction selectivity.
Mature, growing ganglion cells acquire new synapses in the retina of the goldfish
Authors: Hitchcock Peter F. 
Published: June 2009

AbstractThe goldfish retina grows throughout the animal’s life, primarily by a balloon-like expansion. With this expansion, dendritic arbors of ganglion cells show scaled growth; arbors increase in size from small to large with no change in their architecture (Hitchcock & Easter, 1986; Bloomfield & Hitchcock, 1991). The study reported here showed that ganglion cell arbors acquire new synapses with this growth. Arbors from a single type of ganglion cell in retinas of small, young and large, old fish were intracellularly filled with horseradish peroxidase, examined electron microscopically, and the synapses contacting them counted and compared (small arborsvs. large arbors). The small and large arbors had similar numbers and orders of dendritic branches (i.e. similar architectures), but the large arbors were significantly larger than the small ones. The increase in arbor size was correlated with a 2.7x and 1.9x increase in the number of ribbon and conventional synaptic contacts, respectively. The addition of new synapses is proposed as a mechanism by which the signaling properties of the enlarging ganglion cells can remain constant.
Gap-junctional properties of electrically coupled skate horizontal cells in culture
Authors: Qian Haohua , Malchow Robert Paul , Ripps Harris 
Published: June 2009

AbstractWhole-cell voltage-clamp recordings were used to examine the unusual pharmacological properties of the electrical coupling between rod-driven horizontal cells in skate retina as revealed previously by receptive-field measurements (Qian & Ripps, 1992). The junctional resistance was measured in electrically coupled cell pairs that had been enzymatically isolated and maintained in culture; the typical value was about 19.92 MΩ(n = 45), more than an order of magnitude lower than the nonjunctional membrane resistance. These data and the intercellular spread of the fluorescent dye Lucifer Yellow provide a good indication that skate horizontal cells are well coupled. The junctional conductance between cells was not modulated by the neurotransmitters dopamine (200 μM) or GABA (1 mM), nor was it affected by the membrane-permeable analogues of cAMP or cGMP, or the adenylate cyclase activator, forskolin. Although resistant to agents that have been reported to alter horizontal-cell coupling in cone-driven horizontal cells, the junctional conductance between paired horizontal cells of skate was greatly reduced by the application of 20 mM acetate, which is known to effectively reduce intracellular pH. Together with the results obtained in situ on the receptive-field properties of skate horizontal cells, these findings indicate that the gap-junctional properties of rod-driven horizontal cells of the skate are fundamentally different from those of cone-driven horizontal cells in other species. This raises the possibility that there is more than one class of electrical synapse on vertebrate horizontal cells.
The cone photoreceptor mosaic of the green sunfish,Lepomis cyanellus
Authors: Cameron David A. , Easter Stephen S. 
Published: June 2009

AbstractRecent empirical and theoretical evidence has implicated the geometrical birefringence of the double cones of the green sunfish (Lepomis cyanellus) as the biophysical basis of this vertebrate’s sensitivity to polarized light. Because of the intimate link between the organization of the cone-photoreceptor mosaic and the psychophysical details of polarization sensitivity, we have examined the structural features of the green sunfish cone-photoreceptor mosaic, in particular the orientation of the elliptical cross sections of the double cones. Our primary observations are that (1) the arrangement of the cone-photoreceptor mosaic is constant across the retina (with two regional exceptions), with double cones arranged in a rhombic mosaic and aligned roughly ±45 deg to the nearest retinal margin; (2) the double-cone/single-cone ratio is everywhere the same; (3) cone density is inhomogeneous across the retina, with the highest densities in the temporal hemiretina. These results are discussed as they relate to the animal’s retinal growth and visual mechanisms, particularly the sensitivity to polarized light.
Development of dendritic trees of rabbit retinal alpha ganglion cells: Relation to differential retinal growth
Authors: Deich C. , Seifert B. , Peichl L. , Reichenbach A. 
Published: June 2009

AbstractTo provide a quantitative description of the postnatal development of dendritic trees in alpha ganglion cells of the rabbit retina, these cells were stained either by intracellular injection of Lucifer yellow or by application of the lipophilic dye Oil. This was done at three developmental stages: postnatal day (P) 8/9, P 16/17, and in adults. For different retinal locations we quantified the alpha cell dendritic field area, the number of dendritic branch points, and the average dendritic length between branch points. According to the alpha cell location, the data were collected in three groups representing the retinal center, midperiphery, and far periphery, respectively. The data were then correlated with the postnatal retinal expansion which is known to differ among the above topographic regions of the retinae (Reichenbach et al., 1993). Our results show that the growth of alpha ganglion cell dendrites is not proportional to, but significantly exceeds, that of the local retinal tissue. Between P 8/9 and adulthood, the area of central alpha cells increases almost six-fold from 26,000 to 144,000 μm2(retinal expansion: 2.2-fold), and that of peripheral cells more than 15-fold from 35,000 to 556,000 μm2(retinal expansion: four-fold). During this period, the coverage factor of alpha cell dendritic fields increases about three-fold, and reaches adult levels of about 3 (retinal center) and 2.2 (periphery), respectively. The number of dendritic branch points remains nearly constant, and the distance between them increases by a factor close to the square root of the factor by which the dendritic field area grows. Thus, it appears that, from the second postnatal week on, dendritic trees of rabbit alpha ganglion cells increase by intense “interstitial growth,” rather than by outgrowth of (new) dendritic branches. This growth pattern is different from that of some other rabbit retinal ganglion cell types, and of alpha ganglion cells of the cat retina, whose dendritic trees expand at a rate equal to or less than that of the surrounding retinal tissue. The consequences for synaptic contacts with bipolar and amacrine cells are discussed; they suggest a high degree of synaptic plasticity during normal postnatal retinal growth.
Mechanism of anomalous retinal correspondence: Maintenance of binocularity with alteration of receptive-field position in the lateral suprasylvian (LS) visual area of strabismic cats
Authors: Grant Simon , Berman Nancy E. J. 
Published: June 2009

AbstractWe have examined the effects of rearing kittens with a unilateral convergent strabismus, induced surgically at 3 weeks of age, on the binocularity (ocular dominance) and receptive-field position of neurons in the motion-sensitive lateral suprasylvian (LS) area of cat extrastriate cortex. Data were compared to those obtained from area 17 in the same animals, and from the two areas of cortex in normal adult cats. Interocular alignment of the operated cats was assessed in alert adults using corneal reflex photography and during recording from the positions of retinal landmarks under paralysis. The strabismus magnitude in each operated cat was calculated by comparison with equivalent data from the normal animals.Strabismus always caused a major loss of binocularity in area 17. The remaining binocular neurons had receptive-field (RF) pairs arising from positions of normal correspondence in the two retinae and would thus have been responsive to different regions of visual space through the misaligned eyes in the alert animal. In area LS, the effects were dependent on the strabismus magnitude. In the group of four cats with pronounced strabismus (18–30 deg crossed), a loss of binocularity occurred in area LS equivalent in severity to that in area 17. The majority of the remaining binocular LS neurons possessed RF pairs in normal retinal correspondence and would thus, in the alert animal, have received spatially disparate visual input through the two eyes. This also occurred in three other cats with more moderate strabismus (11–15 deg crossed), although only a small breakdown in the binocularity of area LS was apparent. The group of cats with mild strabismus (≤10 deg crossed) had normal proportions of binocular neurons in area LS. In three of these cats, the maintenance of binocularity was accompanied by shifts in RF position, with visual inputs arising from anomalous retinal locations. These shifts compensated, in part, for the strabismus angle present in each cat, so that most of the binocular LS neurons would have received inputs from regions of visual correspondence through the misaligned eyes when the animal was alert.Similar mechanisms could afford a basis for the binocular visual compensations that occur in humans with small-angle strabismus of early onset. If so, anomalous retinal correspondence in such individuals would have as a locus areas of extrastriate cortex with a role in motion perception, and would involve alterations to the neural substrate underlying normal binocular vision.
Suppression of cone-driven responses by rods in the isolated frog retina
Authors: Dong Cun-Jian , Qian Hao-Hua , McReynolds John S. , Yang Xiong-Li , Liu Yu-Min 
Published: June 2009

AbstractThe sensitivity of rod- and cone-driven responses was studied in the isolated frog retina during the period of rapid dark adaptation following a conditioning flash which bleached a negligible amount of visual pigment. Following a conditioning flash, cone-driven b-wave responses were first enhanced and then depressed. The time courses of the enhancement and subsequent depression of cone-drive responses varies greatly with the intensity and wavelength of the conditioning flash, but were identical when the conditioning' flashes were matched for equal excitation of 502 nm rods. These changes in cone-driven response sensitivity were correlated with the desensitization and recovery of rods following the conditioning flash. When signal transmission from rods to second-order cells was interrupted by the addition of L-glutamate, the conditioning flash did not produce the above-described enhancement and subsequent depression of long-wavelength receptor potential responses. The suppression of cone-driven response therefore appears to be due to a synaptically mediated influence from 502 nm rods which is maximal when the rods are in the dark-adapted state, with little or no contribution from 433 nm rods, and no involvement of the pigment epithelium.
Intensity, color, and pattern discrimination deficits after lesions of the core and belt regions of the ectostriatum
Authors: Bessette Brenda B. , Hodos William 
Published: June 2009

AbstractPigeons were trained to discriminate visual stimuli that differed in intensity, color, or pattern, after which lesions were made in the ectostriatum, either the core region (EC), the belt region (EB), or both (EC + EB). Control lesions were made in the lateral neostriatum. After surgery, the birds were again trained to discriminate the stimuli. On the basis of a quantitative analysis of the lesion reconstructions, each pigeon was assigned to one of five groups: EC, EB, moderate (EC + EB), slight (EC + EB), or control. Postoperative savings scores, based on the number of preoperative and postoperative sessions required to discriminate the stimuli, were calculated. An analysis of variance indicated a significant effect of lesion location on the extent of postoperative savings or loss. Only the moderate (EC + EB) group was significantly different from the neostriatum controls. A multiple regression analysis of performance on the individual discrimination tasks indicated that the extent of damage to EC predicted the initial performance deficit on the intensity and one of the two pattern discrimination tasks (vertical versus horizontal bar). The color discrimination deficit, which was modest in extent and of short duration, was predicted only by the damage to (EC + EB) that was at least moderate in extent (20–40% of the volume of (EC + EB)).
Neuropeptide Y-Containing Neurons are Situated Predominantly Outside Cytochrome Oxidase Puffs in Macaque Visual Cortex
Authors: Kuljis Rodrigo O. , Rakic Pasko 
Published: June 2009

AbstractLayers II/III of the primary visual cortex contain a regular pattern of histochemically detectable cytochrome oxidase (CO)-rich “puffs,” which differ from the interpuff regions in their thalamo-cortical and cortico-cortical connectivity, receptive-field properties, and the density of inhibitory GABA-containing synaptic terminals. We used an immunocytochemical method, in combination with cytochrome oxidase histochemistry, to analyze the spatial relationship between neurons that contain neuropeptide Y (NPY) and the CO puffs. Of a total of 606 neurons, only 2.6% of the NPY-containing cells are located in the puffs, whereas the rest are situated in the interpuffs, or at the interface between puffs and interpuffs. The number of NPY-containing neurons in the puffs is substantially less than that expected in an equal volume of the interpuffs (X2 = 13.86; df = 1; P < 0.001).These observations indicate that columns containing the puffs may differ also from those in the interpuff regions in that they contain a unique array of chemically and morphologically distinct local circuit neurons.
Selective Labeling of Visual Corpus Callosum Connections with Aspartate in Cat and Rat?
Authors: Elberger Andrea J. 
Published: June 2009

AbstractTritiated neurotransmitter candidates were unilaterally injected in visual cortical regions with abundant corpus callosum connections. D-aspartate (Asp) or gamma-aminobutyric acid (GABA) was injected along the area 17/18 border in cat, and the area 17/18a and 17/18b borders in rat. Retrograde Asp label was found contralaterally in supragranular and infragranular laminae in areas 17, 18, 19, PMLS, and PLLS in cat, and in areas 29, 18b, 17, and 18a in rat. No contralateral GABA label was found in cat or rat. Thus, the cat and rat corpus callosum may use Asp or a related substance as a neurotransmitter.
Light-regulated proteins inLimulusventral photoreceptor cells
Authors: Edwards Samuel C. , Wishart Anne C. , Wiebe Eric M. , Battelle Barbara-Anne 
Published: June 2009

AbstractThe protein intermediates of the photoresponse and the modulation of this response in invertebrate photoreceptors are largely unknown. As a first step toward identifying these proteins, we have examined light-stimulated changes in protein phosphorylation in preparations ofLimulusphotoreceptors. Here we show that light modulates the level of phosphorylation of three proteins associated withLimulusventral photoreceptors: the upper band of a 46-kD protein doublet (46A) and a 122-kD protein, which become more heavily phosphorylated in response to light, and the lower component of the 46-kD doublet (46B), which is phosphorylated in dark-adapted cells, but not in cells maintained in the light. In dark-adapted preparations, 46A is phosphorylated within 30 s after a flash of light and dephosphorylates over a period of many minutes. It is also a major substrate for calcium/calmodulin-dependent protein kinase (Wiebe et al., 1989); therefore, we speculate that 46A is involved in some aspect of dark adaptation. Interestingly, the level of phosphorylation of 46A is the same when measured from preparations maintained in complete darkness or ambient light for at least 1.5 h. The 122-kD phosphoprotein is the same protein which becomes phosphorylated in response to efferent innervation toLimuluseyes (Edwards et al., 1988) and the efferent neurotransmitter, octopamine (Edwards and Battelle, 1987). It may be involved in the increase in retinal sensitivity and the enhanced response of photoreceptors to light that is initiated by efferent innervation. Its role in light-stimulated processes is not clear. The level of phosphorylation of 46B may be most relevant to the long-term state of adaptation of the photoreceptor cell to light and dark.
Nucleus isthmi in goldfish:In vitrorecordings and fiber connections revealed by HRP injections
Authors: King W. Michael , Schmidt John T. 
Published: June 2009

AbstractRecordings of field potentials in nucleus isthmi (NI) were obtained in anin vitropreparation of goldfish brain using a lateral approach. Horseradish peroxidase (HRP) was injected from recording electrodes to verify recordings within the nucleus and to label axonal pathways and cell bodies. Activity in NI was repetitive and could be elicited by stimulation of the optic nerve, tectum, pretectum, or tectobulbar tract. Spontaneous activity was present in some preparations and consisted of bursts with intervening silent periods. Anatomical and electrophysiological evidence indicated that the primary isthmotectal pathway is composed of fine fibers that exit NI rostrally and pass through pretectum to enter tectum rostrally. An afferent pathway consisting of both fine- and large-diameter fibers entered NI ventromedially; the large diameter axons have been previously reported in percomorph fishes, but were not thought to be present in cyprinids such as goldfish. The large diameter axons arise from labeled cell bodies in the region of the lateral thalamic nucleus. No labeled cell bodies were seen in ipsilateral nucleus pretectalis superficialis, pars magnocellularis, where they are seen in percomorphs. The fine axons, which have not been reported in percomorph fishes, were shown to arise from tectal bipolar (type VI) neurons. As in percomorphs, tectal type XIV neurons were also labeled. This and corroborating recordings from nucleus isthmi constitute the first demonstration of a tectoisthmic projection in a cyprinid fish.
Neuromodulation of pigment movement in the RPE of normal and 6-OHDA-lesioned goldfish retinas
Authors: Ball Alexander K. , Baldridge William H. , Fernback Timothy C. 
Published: June 2009

AbstractThe role of dopamine as the endogenous signal-initiating light-dependent changes in the distribution of pigment granules in goldfish retinal pigment epithelium was investigated. In normal retinas, light adaptation resulted in the dispersion of pigment granules. This effect of light was mimicked by the intraocular injection of dopamine or serotonin, which is thought to increase endogenous dopamine release, into dark-adapted eyes. The effect of light, dopamine, or serotonin on dark-adapted retinas was blocked by the dopamine receptor antagonists haloperidol and sulpiride. However, lesioning the endogenous source of retinal dopamine, by prior intraocular injection of 6-hydroxydopamine (6-OHDA), did not block the dispersion of pigment granules in light-adapted retinas. No significant differences in pigment dispersion were noted between unlesioned and lesioned light- or dark-adapted retinas. However, the effect of light on pigment dispersion was no longer blocked by haloperidol or sulpiride in 6-OHDA lesioned animals. Dopamine and serotonin mimicked the effect of light when injected into lesioned dark-adapted eyes, but their effects were also not blocked by haloperidol or sulpiride. These results suggest that dopamine, acting on D2receptors, is sufficient to induce pigment migration in unlesioned animals. In 6-OHDA-lesioned animals, however, pigment migration is mediated by a receptor mechanism other than D2.