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B Dreher

Publications and source records attributed to B Dreher.

At least 19 recordsLinked to original sources
PubMed2000

Plasticity in adult cat visual cortex (area 17) following circumscribed monocular lesions of all retinal layers.

1. In eight adult cats intense, sharply circumscribed, monocular laser lesions were used to remove all cellular layers of the retina. The extents of the retinal lesions were subsequently confirmed with counts of alpha-ganglion cells in retinal whole mounts; in some cases these revealed radial segmental degeneration of ganglion cells distal to the lesion. 2. Two to 24 weeks later, area 17 (striate cortex; V1) was studied electrophysiologically in a standard anaesthetized, paralysed (artificially respired) preparation. Recording single- or multineurone activity revealed extensive topographical reorganization within the lesion projection zone (LPZ). 3. Thus, with stimulation of the lesioned eye, about 75 % of single neurones in the LPZ had 'ectopic' visual discharge fields which were displaced to normal retina in the immediate vicinity of the lesion. 4. The sizes of the ectopic discharge fields were not significantly different from the sizes of the normal discharge fields. Furthermore, binocular cells recorded from the LPZ, when stimulated via their ectopic receptive fields, exhibited orientation tuning and preferred stimulus velocities which were indistinguishable from those found when the cells were stimulated via the normal eye. 5. However, the responses to stimuli presented via ectopic discharge fields were generally weaker (lower peak discharge rates) than those to presentations via normal discharge fields, and were characterized by a lower-than-normal upper velocity limit. 6. Overall, the properties of the ectopic receptive fields indicate that cortical mechanisms rather than a retinal 'periphery' effect underlie the topographic reorganization of area 17 following monocular retinal lesions.

Animals↗
PubMed1999

Projections from striate and extrastriate visual cortices of the cat to the reticular thalamic nucleus.

We have studied the pattern of connectivity of the visual cortical areas 17, 18, 19, 20a, 21a, posteromedial lateral (PMLS), and the posterolateral lateral (PLLS) suprasylvian areas with the reticular thalamic nucleus (RTN) of the cat ventral thalamus. Three cortical areas per hemisphere were injected iontophoretically with either 4% wheat germ agglutinin-horseradish peroxidase, 4% dextran-fluororuby, or 4% dextran-biotin. The visual field representations of the injection sites were determined by reference to previously published visuotopic maps of the cortex. The locations of labelled fibres, presumed terminals and cell bodies were determined with the aid of a camera lucida attachment and computer aided stereometry. In the ventral thalamus, the primary visual cortices (areas 17 and 18) project in a topographic manner to both the perigeniculate nucleus (PGN) and the RTN. By contrast, the "higher" visual cortical areas (areas 19, 21a, 20a, PMLS, and PLLS) project only to the RTN. Our experiments demonstrate the existence of a single, albeit coarse, visuotopic map within the RTN but do not support the notion of separate subregions within the RTN that can be related specifically to a particular visual cortical area. The putative single visuotopic map in the RTN appears to be organised in such a way that the vertical meridians are represented along the rostrocaudal axis of the RTN, whereas the horizontal meridians are mapped within the dorsoventral axis of the nucleus. The upper visual field is represented within regions of the RTN adjacent to the caudal part of the dorsal lateral geniculate nucleus (LGNd), whereas the lower visual field is represented in the parts of the RTN rostral to the LGNd. The map also shows a ventrodorsal shift along the rostrocaudal axis of the RTN such that in the rostral RTN the representation of vertical meridian is placed more ventrally than that in the caudal part of the nucleus.

Animals↗
PubMed1999

Velocity response profiles of collicular neurons: parallel and convergent visual information channels.

We have recorded from single neurons in the retinorecipient layers of the superior colliculus of the cat. We distinguished several functionally distinct groups of collicular neurons on the basis of their velocity response profiles to photic stimuli. The first group was constituted by cells responding only to photic stimuli moving at slow-to-moderate velocities across their receptive fields (presumably receiving strong excitatory W-type input but not, or only subthreshold, Y-type input). These cells were recorded throughout the stratum griseum superficiale and stratum opticum and constituted 50% of our sample. The second group of cells exhibited excitatory responses only at moderate and fast velocities (presumably receiving excitatory Y-type but not W-type input). These cells constituted only about 7% of the sample and were located principally in the lower stratum griseum superficiale. The third group of cells was constituted by cells excited over the entire range of velocities tested (1-2000 /s) and presumably received substantial excitatory input from both W- and Y-channels. These cells constituted almost 26% of our sample and were located in the lower stratum griseum superficiale, stratum opticum and the upper part of the stratum griseum intermediale. Overall, cells receiving excitatory Y-type input, i.e. the sum of group two and group three cells, constituted about a third of the sample and their excitatory discharge fields were significantly larger than those of cells receiving only W-type input. A fourth distinct group of collicular neurons was also constituted by cells responding over a wide range of stimulus velocities. These cells were excited by slowly moving stimuli, while fast-moving photic stimuli evoked purely suppressive responses. The excitatory discharge fields of these cells (presumably, indicating the spatial extent of the W-input) were located within much larger inhibitory fields, the extent of which presumably indicates the spatial extent of the Y-input. These low-velocity-excitatory/high-velocity-suppressive cells were recorded from the stratum griseum superficiale, stratum opticum and stratum griseum intermediale and constituted about 17% of the sample. The existence of low-velocity-excitatory/high-velocity-suppressive cells in the mammalian colliculus has not been previously reported. Low-velocity-excitatory/high-velocity-suppressive cells might play an important role in activating "fixation/orientation" and "saccade" premotor neurons recorded by others in the intermediate and deep collicular layers. Overall, in the majority (57%) of collicular neurons in our sample there was no indication of a convergence of W- and Y-information channels. However, in a substantial minority of collicular cells (about 43% of the sample) there was clear evidence of such convergence and about 40% of these (low-velocity-excitatory/high-velocity-suppressive cells) appear to receive excitatory input from the W-channel and inhibitory input from the Y-channel.

Animals↗
PubMed1999

Intravitreal injection of TGFbeta induces cataract in rats.

PURPOSE: In a previous study, it was determined that TGFbeta induces cataractous changes in the rat lens in vitro. The purpose of the present study was to determine whether the introduction of biologically active TGFbeta into the vitreous stimulates cataractous changes in the rat lens in situ. METHODS: TGFbeta was injected into the vitreous of the left eye of anesthetized adult male Wistar rats. The right eye received sterile vehicle as a control. Three to four months after injection, animals were killed, and lenses were enucleated and examined for cataractous changes. RESULTS: All lenses from control eyes remained transparent and maintained normal cellular architecture throughout. In contrast, lenses from TGFbeta-injected eyes displayed cloudiness in the cortex. In some lenses, distinct opacities were also apparent at the equator and extending some distance toward the anterior and posterior poles. Histologically, the opacities corresponded to subcapsular plaques containing aberrant cells and accumulations of extracellular matrix. In addition, cortical fibers in the anterior and posterior of all lenses displayed variable degrees of swelling, and many retained their nuclei. In some regions, the fiber cells appeared to have degenerated to form large homogeneous areas. The cellular architecture of the equator of these lenses was also disrupted and, in the most severe case, no bow zone was apparent with nucleated cells extending to the posterior pole. CONCLUSION: The introduction of active TGFbeta into the vitreous induced lenses to undergo cataractous changes. In addition to the TGFbeta-induced changes in the epithelium that were reported previously, cataractous changes observed in this study also involved the lens fiber cells and resembled changes observed in human posterior subcapsular and cortical cataracts.

Animals↗
PubMed1998

Spatiotemporal patterns of ontogenetic expression of parvalbumin in the superior colliculi of rats and rabbits.

We have examined the development of parvalbumin immunoreactivity in the superior colliculi (SC) of the perinatal and mature rats and rabbits. In mature animals, parvalbumin-expressing cells (PECs) and neuropil in the retinorecipient layers were distributed in a continuous single band extending throughout the entire extent of the colliculus, whereas those in the intermediate layers formed distinct, radially oriented patches. Parvalbumin was expressed for the first time on postconceptional day 34 (PCD 34, postnatal day 12) and PCD 42 (postnatal day 11) in the SC of rat and rabbit, respectively. During ensuing development, both the thickness of the parvalbumin-expressing band in the retinorecipient layers and the numbers of PECs in this band gradually increased, reaching adultlike values by PCD 44 and PCD 50 in the rat and rabbit, respectively. In the rat, monocular eye enucleations on PCD 23 resulted in approximately 55% reduction in the number of PECs in the retinorecipient layers of the contralateral colliculi examined on PCD 44 or PCD 50. Unilateral ablations of the entire visual cortex on PCD 23 (before the first corticotectal fibers from visual cortices reach the SC) or on PCD 28 (when about half of the corticotectal fibers have reached colliculus) resulted in, respectively, approximately 55% and approximately 25% relative reduction in the number of PECs in the retinorecipient layers of the ipsilateral colliculi examined on PCD 44 or PCD 50. We conclude that the ontogenetic expression of parvalbumin in most of PECs in the retinorecipient collicular layers is induced by the activity of the contralateral retinotectal and/or the activity of the ipsilateral corticotectal afferents.

Age Factors↗
PubMed1998

Ontogeny of the primate fovea: a central issue in retinal development.

The formation of the primate fovea has fascinated a substantial number of histologists, pathologists, ophthalmologists and physiologists for more than a century. In this article, using data from the literature as well as our own observations, we identify events which we believe are crucial in this process and present a developmental neurobiologist's view of the formation of the primate fovea. The fovea is a region of the retina specialized for diurnal, high acuity functions which require a high spatial density of cone photoreceptors as well as a large number of inner retinal cells in order to establish the distinct retinofugal pathways (ganglion cell axons) receiving from individual cones in the foveal cone mosaic. A unique feature of the fovea is the displacement of cells connected to the foveal cones onto the rim of the fovea. It is generally believed that this displacement counteracts the problems caused by the scattering of the incoming light by cells and blood vessels of the inner retina. We believe that one of the crucial events in the formation of the primate fovea is the early centripetal migration of photoreceptors towards the central area (centripetal displacement). This process, initiated early in development, continues throughout intrauterine life until some months or years postnatal. We propose that the displacement of cells from the inner layers is related to the earlier developmental accumulation of photoreceptors and inner retinal cells centrally. This, we propose, leads to metabolic "starvation" of the inner retina, resulting from the complete absence of retinal vessels from the vicinity of the incipient fovea. It is suggested that these factors in turn trigger centrifugal displacement of inner retinal cells towards the encroaching perifoveal capillary network and lead to the formation of the foveal depression.

Animals↗
PubMed1998

Excitatory convergence of Y and non-Y channels onto single neurons in the anterior ectosylvian visual area of the cat.

Numerous functional and hodological studies of the anterior ectosylvian visual area (AEV) of the cerebral cortex of the cat suggest that this area plays an important role in processing information about visual motion. In the present study, in cats with selective conduction block of Y fibres in one optic nerve, we have examined the extent of the excitatory convergence of Y (presumed 'motion channel') and non-Y information channels on single neurons in AEV, as well as the contribution of the Y channel to the receptive field properties of AEV neurons. While in normal cats all neurons recorded from AEV were binocular, i.e. could be photically activated via either eye, in cats with selective conduction block of Y fibres in one optic nerve, a significant proportion (about 15%) of AEV cells could be photically activated only via the normal eye. In comparison to those in normal cats, the peak discharge rates of AEV neurons in the Y-blocked cats were drastically reduced not only when photic stimuli were presented via the Y-blocked eye, but also when they were presented via the normal eye. Selective block of Y input also resulted in a significant shift in velocity preferences towards the lower velocities. However, the direction selectivity indices of AEV neurons were not affected by selective Y block. Thus: (i) the responses of AEV neurons to a high velocity of motion are dependent on the integrity of the Y input; (ii) the 'spontaneous' (i.e. not photically evoked) discharges of Y retinal ganglion cells exert a facilitatory influence on the responses of AEV cells to photic stimuli; (iii) although the responses of AEV neurons are dominated by the Y inputs, AEV neurons also receive significant non-Y excitatory inputs; and (iv) the strong direction selectivity revealed in most AEV neurons does not dependent on the integrity of Y input.

Animals↗
PubMed1997

Excitatory convergence of Y and non-Y information channels on single neurons in the PMLS area, a motion area of the cat visual cortex.

We analysed the receptive field properties of neurons in the posteromedial lateral suprasylvian (PMLS) visual cortical area of anaesthetized cats in which there was selective conduction block of the largest (Y-type) fibres in one optic nerve. As in normal cats, in cats with selective block of one optic nerve the great majority of PMLS cells could be activated by photic stimulation through either eye. However, the responses evoked by stimulation via the eye with the selectively pressure-blocked optic nerve ('Y-blocked eye') were significantly weaker than those of the same cells evoked by the stimulation via the normal eye. Accordingly, eye dominance histograms were shifted markedly in favour of the normal eye. Furthermore, there was a significant shift towards lower preferred velocities when PMLS cells were photically stimulated via the Y-blocked eye. Finally, when stimulated via the Y-blocked eye, PMLS cells responded poorly or not at all to high stimulus velocities (> or = 100 degrees/s). On the other hand, a number of receptive field properties, such as the spatial organization of receptive fields, the size of the discharge fields, orientation tuning and direction selectivity indices, were not significantly affected by the removal of the Y input. We conclude that virtually all neurons in the PMLS area of the cat receive excitatory input from both Y and non-Y information channels, although the Y channel provides the dominant input and makes the principal contribution to the detection of high-velocity motion.

Animals↗
PubMed1996

Spatiotemporal pattern of ontogenetic expression of calbindin-28/kD in the retinorecipient layers of rat superior colliculus.

Using an antibody against calbindin-28kD, we have studied the spatial pattern of expression of this protein in the superior colliculi (SC) of four strains of mature laboratory rats. In all four strains, calbindin-expressing cells (CECs) formed horizontally oriented tiers in the retinorecipient and intermediate gray layers but were diffusely distributed throughout the deep layers. Ontogenetically, calbindin-28kD was expressed for the first time in the retinorecipient layers at postconceptional day 20 (PCD 20), by cells located in the rostrolateral region where the first born retinal ganglion cells (RGCs) are represented. Although on the day of birth (PCD 22/23), the CECs were distributed more widely, they were still absent in the most medial part of the SC, that is, the region where the latest born RGCs are represented. The spatial distribution of CECs became adultlike only by PCD 29, that is, at the end of the period of the naturally occurring death of the RGCs. Monocular eye enucleations on PCD 23 prevented the expression of calbindin in the medial fifth of the retinorecipient layers of the contralateral SC, while the unilateral removal of the visual cortices had no discernable effect on the numbers and distribution of the CECs in either SC. Thus, the spatiotemporal pattern of ontogenetic expression of calbindin-28kD in the retinorecipient layers of SC reflects the spatiotemporal pattern of generation of the RGCs, and the retinal input appears to induce neuronal expression of calbindin-28kD in these layers.

Animals↗
PubMed1996

Binocular interactions and disparity coding in area 21a of cat extrastriate visual cortex.

We have examined, using both qualitative and quantitative techniques, binocular interactions of extracellularly recorded single neurons in the extrastriate cortical area 21a of anaesthetized and paralysed cats. Consistent with previous reports we have found that: (a) all area 21a neurons were orientation-selective, with about 65% of them preferring orientations within 30 degrees of the vertical; and (b) over 75% of area 21a cells could be activated through either eye. Furthermore, a significant minority (4 cells; about 10%) of a subpopulation of 39 neurons in which binocular interactions were examined quantitatively, were "obligatory binocular neurons", that is, they responded very weakly, if at all, to the monocular stimuli presented through either eye but responded vigorously to simultaneous stimulation through both eyes. Almost 70% (27/39) of neurons tested quantitatively for binocular interaction have shown significant modulation (over 50%) of their peak responses in relation to binocular positional retinal disparities. The majority of neurons sensitive to binocular positional disparities resembled either "tuned excitatory" (22 cells; 56.5% of the sample) or "tuned inhibitory" (2 cells; 5% of our sample) cells. In particular, they gave, respectively, maximal or minimal responses to optimally oriented, moving photic stimuli when the receptive fields plotted through each eye completely or partially overlapped. Although neurons recorded in area 21a have relatively large receptive fields (mean width 3.3 +/- 1.1 degrees; range 2.0-5.6 degrees), the mean width of the disparity tuning curve (2.8 +/- 1.0 degrees; range 1.3-4.8 degrees) for our sample of area 21a neurons was similar to those of neurons with significantly smaller receptive fields, recorded in areas 17 and 18 of cat's primary visual cortex. We conclude that area 21a of the cat, like areas 17 and 18 of primary visual cortex, is likely to play an important role in binocular depth discrimination and might constitute a "higher order" area for stereoscopic binocular vision.

Animals↗
PubMed1996

Areas PMLS and 21a of cat visual cortex are not only functionally but also hodologically distinct.

In several cats, paired visuotopically matched injections of retrogradely transported fluorescent dyes, diamidino yellow (DY) and fast blue (FB), were made into two visuotopically organized, functionally distinct extrastriate cortical areas, the posteromedial lateral suprasylvian area (PMLS area) and area 21a respectively. After an appropriate survival time, the numbers of thalamic, claustral and cortical cells which were single-labelled with each dye as well as the numbers of cells in these structures labelled with both dyes (double-labelled cells) were assessed. The clear majorities of thalamic cells projecting to PMLS area (DY labelled cells) and to area 21a (FB labelled cells) were located in the ipsilateral lateral posterior-pulvinar complex with smaller proportions located in the laminae C and the medial intralaminar nucleus of the ipsilateral dorsal lateral geniculate nucleus and several nuclei of the rostral intralaminar thalamic group. Despite the fact that DY labelled (PMLS-projecting) and FB labelled (area 21 a-projecting) cells in all thalamic nuclei were well intermingled, only 1-5% of retrogradely labelled thalamic cells projected to both areas (cells double-labelled with both dyes). Small proportions of retrogradely labelled cells were located in the ipsilateral and to a lesser extent the contralateral dorsocaudal claustra. The proportions of claustral neurons retrogradely labelled with both dyes varied from 4 to 9%. Over half of the cortical neurons labelled retrogradely from area 21a or PMLS area were located in the supragranular layers of the ipsilateral area 17, with smaller proportions located in the supragranular layers of the ipsilateral areas 18 and 19 and even smaller proportions located in mainly but not exclusively, the infragranular layers of the ipsilateral areas 21b and 20a. Again despite strong spatial intermingling of neurons labelled with DY and these labelled with FB, the proportions of associational cortical neurons double-labelled with both dyes were small (2 to 5.5%). Finally, small proportions of neurons retrogradely labelled with DY or FB were located, mainly but not exclusively, in the supragranular layers of the contralateral areas 17, 18, 19 and 21a. Again, the proportions of the double-labelled neurons in the contralateral cortices were small (1-4.5%). Thus, the present study indicates that despite the fact that the diencephalic and telencephalic inputs to the visuotopically corresponding parts of area 21a and PMLS area originate from the same nuclei, areas and layers, the two areas receive their afferents from the largely separate populations of neurons.

Animals↗
PubMed1995

Effect of collicular proteoglycan on the survival of adult rat retinal ganglion cells following axotomy.

Consistent with numerous previous studies, we have found that in adult rats 29% of cells retrogradely prelabelled by injections into retino-recipient nuclei are lost 1 week after intraorbital section of the optic nerve. This figure increases to 76% 2 weeks after axotomy. Intraocular injections of 150 ng of 480 kDa chondroitin sulphate proteoglycan purified from the superior colliculi of neonatal rats were performed every third day after axotomy. This procedure resulted in the loss of only 3 and 28% of the axotomized retinal ganglion cells 7 and 14 days respectively after optic nerve section. Intraocular injections of chondroitin sulphate type C, one of the sugar types present on the collicular proteoglycan, also resulted in a significant saving of axotomized ganglion cells (with the loss of only 48% 14 days after optic nerve lesion). These findings suggest that the collicular proteoglycan, and to a lesser extent its sugar moieties, substantially slows down the degeneration of adult retinal ganglion cells following axotomy.

Animals↗
PubMed1995

Glial reactivity in the retina of adult rats.

The present study aimed to characterize the reaction of mammalian (rat) retinal macroglia (Müller cells and astrocytes) to disturbances of their environment in the form of intraorbital section of the optic nerve, intraocular insertion of a thin glass capillary (without damage to the retina) or a combination of both. Glial reactivity was assessed through the use of a battery of antibodies which recognise four different proteins--glial fibrillary protein (GFAP) and three other proteins designated respectively MA1, 4D6 and 4H11. Retinal astrocytes did not exhibit any changes in normally expressed GFAP or MA1. By contrast, the expression of GFAP and MA1 in Müller cells increased 14 days following section of the optic nerve and/or intravitreal insertions of a glass capillary. Three days postoperatively, the expression of GFAP, but not MA1, had already increased significantly in Müller cells. 4D6 and 4H11 proteins were not expressed in astrocytes. In Müller cells, the levels of these proteins increased significantly following combined optic nerve section and intraocular insertion of a glass capillary. Thus, a mechanical disturbance of the intraocular environment constitutes a more effective stimulus in increasing the expression of some Müllerian proteins than damage to the axons of retinal ganglion cells. Such changes have important implications for various ocular treatments that involve intraocular administration of drugs, as well as for the survival/regeneration potential of retinal ganglion cells undergoing Wallerian degeneration.

Animals↗
PubMed1994

Vitread proliferation of filamentous processes in avian Müller cells and its putative functional correlates.

In order to examine to what extent the neuronal and metabolic activities of avascular vertebrate retinae are reflected in the morphology of their Müller cells we have studied (by using several monoclonal antibodies) the morphology of Müller cells in two species of diurnal birds (chicken, Gallus domesticus, and pigeon, Columba livia) and one species of nocturnal saltwater crocodiles (Crocodylus porosi). In all three species, the outer nuclear layer is relatively thin and the Müller cell trunks divide into rootlets that wrap around the photoreceptors. In both diurnal birds studied, the trunks of Müller cells in the inner plexiform layers invariably divide into numerous fine filamentous processes that terminate in small expansions covering most of the vitreal surface of the retina. Furthermore, the networks of filamentous processes of birds' Müller cells exhibit conspicuous horizontal lamination in the inner plexiform layer. In contrast, the filamentous processes arising from the individual Müller cell trunks of the crocodile, if present, are much less numerous and less widely spread than those of diurnal birds. It is proposed that the splitting of the Müller cell trunks into numerous filamentous processes terminating in small vitreal expansions represents a morphological adaptation for: 1) effective spatial buffering of K+ ions in thick and presumably metabolically highly active, yet avascular, avian retinae, and 2) effective absorption and distribution of nutrients leaking from the vitreally located supplemental nutritive organ, the pecten.

Alligators and Crocodiles↗
PubMed1994

The pattern of expression of a 13-kDa protein (CS-32 antigen) in the retina and its target nuclei in developing and mature rats.

A polyclonal antibody (designated CS-32) immunopurifies a 13-kDa protein from the superior colliculus (SC) of neonatal rat. There is a strikingly inverse temporal relationship in expression of the 13-kDa protein in the developing retina and its principal target nuclei, SC and the dorsal lateral geniculate nucleus. The 13-kDa is a cell-surface protein expressed exclusively by neurones and is clearly associated with synapses.

Animals↗
PubMed1994

Non-dominant suppression in the dorsal lateral geniculate nucleus of the cat: laminar differences and class specificity.

Binocular non-dominant suppression (NDS) in the dorsal lateral geniculate nucleus (LGNd) of the cat was studied by recording from single neurons in the LGNd of anaesthetized, paralysed cats while stimulating the non-dominant eye with a moving light bar. The maintained discharge rate of LGNd neurons was varied by stimulating the dominant eye in various ways: by varying the size or contrast of a flashed spot, by varying the inner diameter of a flashed annulus of large outer diameter, by varying the velocity of a moving light bar, and by covering the eye. Non-dominant suppression was quantified either as the decrease in the maintained discharge rate (the "dip"), expressed as spikes per second, or as the ratio of the dip to the maintained discharge rate (the "dip ratio"). At low maintained discharge rates the dip, although low in value, frequently approached the maintained rate, i.e. the dip ratio approached unity. As the maintained discharge rate increased the dip value also increased, but more slowly than the maintained discharge rate, i.e. the dip ratio decreased. At maintained discharge rates above about 30 spikes/s, in many neurons the dip appeared to be approaching a constant value. This strong dependence of NDS on the maintained discharge rate of the LGNd neuron suggests that the inhibitory input to the cell arises from a region of the brain that receives an input both from the non-dominant eye and from the LGNd cell. Reasons are given for thinking that this region is the perigeniculate nucleus. Because of the strong dependence of dip and dip ratio on the maintained discharge rate, it was necessary to adopt stringent criteria when comparing NDS in two different sets of neurons or of the same set of neurons in different conditions. We recognized a significant difference in NDS between two classes of neurons or between two states only if: (1) there was no significant difference between the maintained discharge rates, and (2) there was a significant difference for both dip and dip ratio between the two classes or states. Using these criteria we found: (1) no difference between non-lagged X (XNL) and non-lagged Y (YNL) cells, (2) no difference between on-centre and off-centre cells for either XNL or YNL cells, (3) no difference between XNL cells and lagged X (XL) cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia↗
PubMed1994

Extent of bilateral collateralization among pontomesencephalic tegmental afferents to dorsal lateral geniculate nuclei of pigmented and albino rats.

In adult pigmented and albino rats, small amounts of different fluorescent dyes (Fast Blue and Fluoro-Gold) were pressure-injected into the dorsal lateral geniculate nuclei, each nucleus (right or left) being injected with one dye only. After postinjection survival of three days, the distribution of neurons retrogradely labelled by each dye was analysed. Consistent with previous studies, in each strain each dye labelled a large number of neurons in the several ipsilateral visuotopically or retinotopically organized structures--visual cortices, retino-recipient layers of the superior colliculi and the pretectal nuclei. A substantial number of retrogradely labelled neurons was also found in the contralateral parabigeminal nucleus. A few retrogradely labelled neurons were found in the ipsilateral and (to a lesser extent) contralateral dorsolateral divisions of the periaqueductal gray matter, as well as in the ipsilateral parabigeminal nucleus and the caudal part of the lateral hypothalamus. However, in all the above structures there was a paucity of cells retrogradely labelled with both dyes (double-labelled cells). By contrast, in each strain, several "modulatory" nuclei (containing cholinergic and aminergic cells) of the pontomesencephalic tegmentum--dorsal raphe, pedunculopontine tegmental nucleus, parabrachial nucleus, laterodorsal tegmental nucleus and locus coeruleus--contained significant numbers of cells projecting to both ipsilateral and contralateral dorsal lateral geniculate nuclei. In each nucleus, ipsilaterally and contralaterally projecting cells constituted, respectively, about 65-70% and about 30-35% of retrogradely labelled cells. About 25% of the contralaterally projecting cells (i.e. about 5-10% of all retrogradely labelled tegmental neurons) were double-labelled with both dyes. Double-labelled cells were intermingled with single-labelled cells projecting ipsilaterally or contralaterally. The proportions of the ipsilaterally, contralaterally and bilaterally projecting neurons in the modulatory components of the pontomesencephalic tegmentum were virtually identical in pigmented and albino strains. It appears that in both strains the visuotopically organized structures convey to the dorsal lateral geniculate nuclei information related mainly to the contralateral visual field. The projections from these structures might play an important role in regulating transmission of visual information in the retinotopically distinct parts of each dorsal lateral geniculate nucleus. By contrast, the projections from the modulatory nuclei of the pontomesencephalic tegmentum are likely to contribute to the functional synchronization of both dorsal lateral geniculate nuclei during the sleep-wakefulness cycle and saccadic eye movements.

Afferent Pathways↗