Types of receptive fields in the lateral geniculate body and their functional model

In the Type I receptive fields (RFs) changes of the luminance leads to a shift of the curve relating the response and the stimulus area along the abscissa, in the Type II RFs the maximum of a response does not shift with changes of the luminance (Types I and II on classification by Glezer et al., 1971, 1972). The transient responses were observed in the Type I RFs and sustained responses in the Type II RFs. In the Type I RFs variation of the stimulus area and intensity brings about the change in the temporal and spatial frequency characteristics. This is produced by functional reorganization of the RF. In the Type II RFs there is no functional reorganization. The data obtained indicate that the Type I RFs are non-linear. By contrast, the Type II RFs are linear systems. The analysis of the model has shown that the distinctions in the dynamic characteristics of the responses of RFs belonging to different types is mainly due to different time constants for excitation and inhibition as well as inhibition coefficients. Distinctions in the mode of dependence of the RF response on stimulus parameters have been found to result from different relationship between delay time and stimulus parameters as well as different forms of the spatial weighting functions. It is shown that the Type I RFs transmit higher frequency components of the image spectrum, i.e. they emphasise the temporal and spatial contrasts. The Type II RFs transmit low frequency components of the spectrum including information about the intensity of an input stimulus.     

Types of receptive fields of the lateral geniculate body and their functional model

Functional differences between the type I and II receptive fields of the lateral geniculate body were studied in the cat. Some properties of these fields were shown to coincide with properties of "phasic" (Y type) and "tonic" (X type) of receptive fields. The type I fields have a limited range for transmission of information about the intensity of illumination; the type II fields, on the other hand, have a normal dynamic range of 2 log units. Using the number of spikes in groups as a measure of nervous activity, a neurophysiological scale of brightness corresponding to the psychological scale can be constructed on the basis of responses of the type II receptive field. It is postulated that type I receptive fields serve to transmit information on the shape of the image (spatial and temporal contrasts) and the type II fields transmit information on intensity of illumination. Investigation of the dynamic functional model showed that the type of receptive field is determined by the depth of inhibition through the interneuron. The depth of inhibition is much greater for type I than for type II.     

Spatial distribution and interaction of responses in receptive fields of cat lateral geniculate neurons

Responses of lateral geniculate neurons to local photic stimulation and to adaptation of the central, antagonistic, and disinhibiting zones of their receptive fields were compared in unanesthetized cats immobilized with D-tubocurarine. Under most conditions of local adaptation, activation of on- and off-responses of neurons occurred after stimulation of the peripheral zones and inhibition of responses after stimulation of the central zone of the receptive field. As a result most neurons acquired the ability to generate a considerable on- and off-signal in response to stimulation. Comparison of this fact with the properties of on-off neurons [7] supports the view that under light-adaptation conditions the processing of large volumes of visual information and the more sophisticated performance of visual functions are connected with activation of responses from peripheral zones of circular receptive fields. It is concluded that local adaptation to light can extend the functional capacity of circular receptive fields.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 15, No. 5, pp. 451–456, September–October, 1983.     

Effect of removal of corticofugal influences on receptive fields of lateral geniculate neurons in the cat

Unilateral division of corticogeniculate connections increases the number of spikes in unit responses of the ipsilateral lateral geniculate body to receptive field stimulation and potentiates the effects of lateral inhibition. The area of the zone of complete summation of all lateral geniculate neurons recorded on the side of operation depends on contrast of the local photic stimulus. It is concluded that cortical fibers descending to the lateral geniculate body are inhibitory in nature and that the existence of receptive fields with a variable zone of spatial summation is due to intrageniculate mechanisms.Institute of Experimental Medicine, Academy of Medical Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 7, No. 5, pp. 486–492, September–October, 1975.     

Inhibitory zones of receptive fields of the lateral geniculate body and visual cortex of the cat

Unit responses to moving strips were investigated. The organization of the inhibitory zones in the receptive fields of the lateral geniculate body and visual cortex of the cat was compared. The response in the receptive field of the lateral geniculate body was inhibited only during simultaneous stimulation of the excitatory and inhibitory zones of the field. Stimulation of the inhibitory zone in the receptive field of the visual cortex was effective for a long time (several hundreds of milliseconds) after stimulation of the excitatory zone. The inhibitory zones of the simple and complex receptive fields of the visual cortex differed significantly. An increase in the width of the strip above the optimal size reduced the inhibitory effect in the complex fields. This was not observed in the simple receptive fields. The functional and structural models of the receptive field of the visual cortex are discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 5, No. 2, pp. 201–209, March–April, 1973.     

Dependence of functional organization of receptive fields of the cat lateral geniculate body on visual stimulus contrast

The spatial organization of receptive fields of the lateral geniculate body in response to visual stimuli with different degrees of contrast was studied in cats. During variation of contrast changes in organization of the central zone were found to take place in some receptive fields. Inside the central zone of the receptive field as revealed by the use of low stimulus contrasts, an additional inhibitory ring appears in response to a stimulus of high contrast. The weighting function of the central zone of the receptive field becomes variable in sign. The role of this phenomenon in transmission of information on high spatial frequencies (increase in visus) at high contrasts is discussed.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 789–796, November–December, 1984.     

Age-related changes in nitric oxide synthase in the lateral geniculate nucleus of rats

Age-related changes in nitric oxide production in the visual system have not been well characterized. Therefore, we used staining and image-processing approaches to describe changes in levels of neuronal nitric oxide synthase (nNOS), the NADPH-diaphorase (NADPH-d) histochemical marker, and 3-nitrotyrosine in the lateral geniculate nucleus (LGN) of young and aged rats. The LGN plays an important role in the visual system, as it acts as a visual relay nucleus. Quantitative analysis of NADPH-d-positive and nNOS-immunoreactive neurons revealed significant optical density increases in the dorsal LGN and ventral LGN of aged rats; however, no significant changes were observed in the number of neurons with age. 3-Nitrotyrosine immunoreactivity was increased in the dorsal LGN and ventral LGN of aged rats. These results indicate that increased nitric oxide production and peroxynitrite may be associated with alterations in visual function during aging.     

Parvalbumin,calbindin, and calretinin mark distinct pathways during development of monkey dorsal lateral geniculate nucleus

Immunocyochemical labeling was applied to follow the developmental changes in the calcium-binding proteins parvalbumin (PV), calbindin D28k (CaB), and calretinin (CaR) during fetal and infant development of Macaca monkey dorsal lateral geniculate nucleus (LGN). For all three proteins, LGN cell body and retinal ganglion cell (RGC) axon labeling patterns changed temporally and spatially over development, and many of these were LGN laminar specific. CaR+ and CaB+ cells were present at the youngest age studied, fetal day 55 (F55). After lamination of the LGN occurred between F90 and F115, CaR+ and CaB+ neurons were specific markers for the S, intercalated, and interlaminar layers. Double label immunocytochemistry showed that all CaR+ cells contained CaB, and none contained GABA. CaR+ cell bodies decreased in number soon after birth so that adult LGN contained only a very small number of CaR+ cells. These patterns and cell counts indicated that a downregulation of CaR had occurred in the CaB+ population. Although CaB+ cell density in S and interlaminar zones declined in the adult, cell counts indicated that this is due to dilution of a stable population into a much larger nucleus during development. PV+ cells appeared at F85 only within the putative magnocellular (M) and parvocellular (P) layers, and PV remained a marker for these layers throughout development. Fetal PV cells also contained GABA, indicating that they were LGN interneurons. After birth, GABA−/PV+ cell numbers increased dramatically throughout the whole nucleus so that by the end of the first year, P and M layers were filled with PV+ cells. Their number and size indicated that these were the LGN projection neurons. Beginning at F66, bundles of PV+ axons occupied the anterior-middle LGN and filled the optic tract. Up to F101, PV+ synaptic terminals were restricted to P layers, but after F132 labeling in M layers was heavier than in P layers. Axonal labeling for CaR began at F125. Prenatally CaR+ terminals were present mainly in P layers, whereas by postnatal 9 weeks labeling in M layers much exceeded P layers. Axonal labeling for CaB was present at F132, but CaB+ terminals were observed only after birth with labeling always heavier in M than P layers. By postnatal 9 weeks, PV, CaR, and CaB were colocalized in the same axons and terminals. These experiments indicated that during development and in the adult LGN, both CaR and CaB were markers for the LGN neurons in the S and intercalated pathway. CaR was present transiently while CaB persisted into adulthood. PV was a M and P layer marker first for interneurons and later for projection cells. The complex temporal developmental patterns found in this study suggested that viewing PV, CaB, and CaR simply as calcium-buffering proteins severely underestimates their functional roles during visual system maturation. © 1996 John Wiley & Sons, Inc.     

The role of cortical feedback in the generation of the temporal receptive field responses of lateral geniculate nucleus neurons: a computational modelling study

The influence of cortical feedback on thalamic visual responses has been a source of much discussion in recent years. In this study we examine the possible role of cortical feedback in shaping the spatiotemporal receptive field (STRF) responses of thalamocortical (TC) cells in the lateral geniculate nucleus (LGN) of the thalamus. A population-based computational model of the thalamocortical network is used to generate a representation of the STRF response of LGN TC cells within the corticothalamic feedback circuit. The cortical feedback is shown to have little influence on the spatial response properties of the STRF organization. However, the model suggests that cortical feedback may play a key role in modifying the experimentally observed biphasic temporal response property of the STRF, that is, the reversal over time of the polarity of ON and OFF responses of the centre and surround of the receptive field, in particular accounting for the experimentally observed mismatch between retinal cells and TC cells in respect of the magnitude of the second (rebound) phase of the temporal response. The model results also show that this mismatch may result from an anti-phase corticothalamic feedback mechanism.     

Characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons of cat in response to changes in photic stimulation parameters

The effect of parameters of local photic stimulation of different points of the receptive field on the characteristics of dynamic reorganization of receptive fields of cortical and geniculate visual neurons within microintervals of time observed previously was studied in computer-controlled experiments on unanesthetized, curarized cats. Dependence on the degree of widening of the receptive field and the temporal characteristics of this process on the background illumination level, intensity, contrast, area, duration, energy, and orientation of a local rectangular or circular photic stimulus flashing in random order at 100 points of the tested part of the visual field was studied. It was concluded that the background illumination level and the intensity, size, duration, and orientation of the stimulus have a specific effect on dynamic reorganization of the receptive field. The effects of all the parameters studied on the dynamics of the receptive field were shown to be nonlinear functions with optimal values that differed for different cells. The possible functional role of this effect and also the probability that it may participate in information coding in the visual system are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 15, No. 4, pp. 339–346, July–August, 1983.     

Fine structural morphology of identified X- and Y-cells in the cat's lateral geniculate nucleus

Four physiologically identified neurons in the A laminae of the cat's dorsal lateral geniculate nucleus were filled with horseradish peroxidase and studied using the electron microscope. Two were X-cells and two were Y-cells. Each had electrophysiological properties appropriate for its X- Or Y-cell class, and each also had an axon that projected into the optic radiation, indicative of a geniculocortical relay cell. Representative samples from about 10% of each neuron's entire dendritic arbor (proximal and distal) were taken to obtain an estimate of the types and distributions of synapses contacting these arbors. One X-cell had a cytoplasmic laminar body, but there were no other significant cytological differences seen among the neurons. Common to each of the neurons were the following synaptic features: (i) retinal terminals (r.l.p.) were mostly or entirely restricted to proximal dendrites or dendritic appendages (less than 100 microns from the soma). These terminals constituted about 15-25% of the synapses on the proximal dendrites. (ii) Terminals with flattened or pleomorphic synaptic vesicles (f. terminals) were predominant on the proximal dendrites (30-55% of the total synapses for that region) and were mainly located near the retinal terminals. A smaller percentage (10-20%) were also distributed onto the distal dendrites. (iii) Small terminals with round synaptic vesicles (r.s.d.), many presumably having a cortical origin, predominated (60-80%) on distal dendrites (greater than 100 microns), but also formed a large proportion (40-70%) of the synapses on the intermediate (50-150 microns) dendrites. Total synaptic contacts for one X-cell and one Y-cell were estimated at about 4000 and 5000, respectively. The major fine structural differences observed between X- and Y-cells were almost entirely related to the retinal afferents. First, the retinal synapses for X-cells were mostly made on to dendritic appendages (spines, etc.), whereas Y-cells had most of their retinal synapses onto the shafts of primary and proximal secondary dendrites (that is, near branch points. Second, the retinal terminals that contacted X-cell dendrites nearly always formed triadic arrangements that included nearby f. terminals, but those on Y-cells rarely did so. Finally, the main type of f. terminals associated with X-cells were morphologically different from most of those associated with the Y-cells, and this also related directly to the triadic arrangements; that is, f. terminals in the triadic arrangements were morphologically distinguishable from f. terminals that did not participate in triadic arrangements.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ageing and monoamine turnover in the lateral geniculate nucleus and visual cortex of the rat

The effects of ageing on the turnover of dopamine, noradrenaline and serotonin in the lateral geniculate nucleus and the visual cortex were evaluated, using high performance liquid chromatography (HPLC) with electrochemical detection. Compared to adult animals, aged rats showed more changes in the visual cortex than in the lateral geniculate nucleus, with dopamine turnover decreased in both structures and noradrenaline turnover unaltered. Changes in serotonin turnover were witnessed only in the visual cortex. A decrease in the monoamine oxidase-A to -B ratio was also observed with increased age for both the lateral geniculate nucleus and visual cortex.     

Origin and dynamics of extraclassical suppression in the lateral geniculate nucleus of the macaque monkey

In addition to the classical, center/surround receptive field of neurons in the lateral geniculate nucleus (LGN), there is an extraclassical, nonlinear surround that can strongly suppress LGN responses. This form of suppression likely plays an important role in adjusting the gain of LGN responses to visual stimuli. We performed experiments in alert and anesthetized macaque monkies to quantify extraclassical suppression in the LGN and determine the roles of feedforward and feedback pathways in the generation of LGN suppression. Results show that suppression is significantly stronger among magnocellular neurons than parvocellular neurons and that suppression arises too quickly for involvement from cortical feedback. Furthermore, the amount of suppression supplied by the retina is not significantly different from that in the LGN. These results indicate that extraclassical suppression in the macaque LGN relies on feedforward mechanisms and suggest that suppression in the cortex likely includes a component established in the retina.     

Termination of retinofugal fibers and lamination pattern in the lateral geniculate nucleus of the gibbon

The lateral geniculate nucleus (LGN) of the gibbon (Hylobates sp.) consists of four principal layers, i.e., layers 1 and 2 containing large somata and layers 3 and 4 comprising medium-sized neurons. In addition, there are intercalated layers S, imm and imp, each consisting of small cells. Tracing of retinofugal fibers with the autoradiographic method revealed that the retina projects to the ipsilateral layers 2, 3 and imp and to the contralateral layers 1, 4, S and imm. No 'hidden' layers have been found. This type of lamination pattern sets the LGN of the gibbon apart from that of all Old World monkeys, chimpanzee and man. Retinal projections to other subcortical regions are also described.