Lateral Geniculate Body Of Cat Research Articles

Pioneers of cortical plasticity: six classic papers by Wiesel and Hubel

This essay looks at six APS classic papers published by D. H. Hubel and T. N. Wiesel that first identified a developmental critical period for environment influenced receptive field plasticity in the visual pathway. These classic papers are freely available online. These are listed here, in chronological order. Wiesel TN, Hubel DH. Effects of visual deprivation on morphology and physiology of cells in the cat's lateral geniculate body. J Neurophysiol 26: 978–993, 1963 ( http://jn.physiology.org/cgi/reprint/26/6/978 ). Hubel DH, Wiesel TN. Receptive fields of cells in striate cortex of very young, visually inexperienced kittens. J Neurophysiol 26: 994–1002, 1963 ( http://jn.physiology.org/cgi/reprint/26/6/994 ). Wiesel TN, Hubel DH. Single-cell responses in striate cortex of kittens deprived of vision in one eye. J Neurophysiol 26: 1003–1017, 1963 ( http://jn.physiology.org/cgi/reprint/26/6/1003 ). Wiesel TN, Hubel DH. Comparison of the effects of unilateral and bilateral eye closure on cortical unit responses in kittens. J Neurophysiol 28: 1029–1040, 1965 ( http://jn.physiology.org/cgi/reprint/28/6/1029 ). Hubel DH, Wiesel TN. Binocular interaction in striate cortex of kittens reared with artificial squint. J Neurophysiol 28: 1041–1059, 1965 ( http://jn.physiology.org/cgi/reprint/28/6/1041 ). Wiesel TN, Hubel DH. Extent of recovery from the effects of visual deprivation in kittens. J Neurophysiol 28: 1060–1072, 1965 ( http://jn.physiology.org/cgi/reprint/28/6/1060 ).

A new property of orientation-selective neurons of the cat lateral geniculate body

Neuronal mechanisms of description of local properties of visual object light-shadow surfaces are studied. Earlier we have shown the cat lateral geniculate body (LGB) neurons to have sensitivity to the value and direction of brightness vector in loci of object light-shadow surfaces. Further study of properties of orientational selectivity (OS) of these neurons has revealed that single LGB cells sensitive to direction of the brightness gradient vector also have the classical OS to direction of test bands. Such complex orientational sensitivity of neurons to direction of binary and light-shadow fragments of visual objects is of essential significance, in our opinion, for understanding of principles and mechanisms of object vision.

Characteristics of Gamma-Oscillations in Responses of Neurons of the Cat Lateral Geniculate Body

There were studied characteristics of gamma-oscillations in responses of neurons of the lateral geniculate body (LGB) in cat to exposure in their receptive fields (RF) of half-tone and binary test images. The gamma-oscillations were observed in 38.8% of cases (69 cells). The spectral characteristics (SC) (the band 20–100 Hz) of the neuronal responses to adequate stimuli (on- and off-responses correspondingly of on- and off-neurons) were analyzed. The total of 5930 poststimulus histograms (PSTH) of responses constructed from 177 900 neuronal impulse responses were considered. The mean value of the SC dominant frequencies of the whole sample of the neuronal responses amounted to 44.74 ± 21.46 Hz. In this cell sample, the neurons were revealed, which generated oscillations with markedly different frequencies in response to the same stimuli. Based on this property, three types of neurons were determined, with the mean oscillation frequencies of 26.95 ± 4.35, 52.02 ± 9.05, and 85.79 ± 7.19 Hz. The histograms of distribution of peak frequency values in SC of the neuronal responses and of index values of these oscillation peaks also revealed three maxima that corresponded to the frequencies of the three described types of neurons. The mean values of dominant frequencies of gamma-oscillations in responses of all three types of neurons remained constant (within the limits of dispersion) at changes of spatial-brightness parameters of test stimuli as well as at changes of the neuronal excitation level (the number of impulses in responses). The oscillation index values of dominant frequencies depended on parameters of the test images and correlated with the neuronal excitation level (the coefficient of correlation was 0.78 from data of 5930 CX). The suggestion is made about the existence in the neuronal network of the synchronization mechanisms functioning on the principle of “multiple synchronization. ”

The sensitivity of neurons in the lateral geniculate body of the cat to the orientation vectors of brightness gradients.

We describe here a new property of visual neurons: sensitivity to the magnitude and orientation of the brightness gradient vector in a test stimulus presented in the receptive field of the neuron. The brightness gradient test image was a spot (diameter 4 degrees) on the dark background of the slide. Brightness changed linearly within the spot. The absolute value of the brightness gradient varied over the range 0.4-2.7 cd/m2 /degrees in the direction of the brightness gradient. The integral brightness in the test spot containing the gradient image was identical for different values of the brightness gradient. The numbers of spikes in the on- and off-responses of on and off neurons in the lateral geniculate body of cats depended on the orientation of the brightness gradient vector in the test stimulus. The sensitivity of neurons to the orientation of the brightness gradient vector, K (the coefficient of sensitivity), was assessed as the normalized difference between the number of spikes in neuron responses in the preferred and non-preferred orientations of the brightness gradient vector in the neuron's receptive field. The mean sensitivity coefficient for 53 cells was 0.55 +/- 0.20. A 6.7-fold decrease in the brightness gradient resulted in a 3.7-fold decrease in the coefficient of sensitivity (for the preferred direction of the orientation of the gradient vector); there was no change in the latent period of responses. The preferred orientation of the brightness gradient vector in the receptive fields of neurons coincided (to within +/-22.5 degrees) with the radial direction on the map of the field of vision in 45% of cases, and with the tangential direction in 26% of cells.

Estimation of Local and Global Characteristics of Half-Tone Surfaces by the Cat's Lateral Geniculate Body

We investigated neuronal mechanisms in the cat's dorsal LGN that could carry information about the spatial brightness distribution across half-tone visual object surfaces. Stimuli were halftone spheres, cylinders, toroids, etc. We have found that geniculate neuronal structures describe and estimate both local and global characteristics of the brightness distribution on these surfaces. The search for local mechanisms of perception of half-tone surfaces revealed a new property of geniculate neurons: their sensitivity to changes in both the magnitude and vector direction of the spatial brightness gradient in the test stimulus. The quantitative estimation of gradient sensitivity in each case has been calculated by the formula: K=( Nmax- Nmin)/ Nmax, where Nmax is the number of spikes (in a 500 ms interval) in response to the preferred (and Nmin to the nonpreferred) gradient direction. The average value of K was 0.49 (range 0.15 – 0.95) for a mean brightness gradient of 2.7 cd m−2 deg−1. A ninefold decrease of the gradient reduced K by a factor of 6.5. The preferred direction of most (82%) neurons coincided with the radial direction from the centre of the receptive field to area centralis. The basis of this phenomenon probably lies in the influence of the spatial brightness gradient on spatiotemporal relations between excitatory and inhibitory processes in geniculate receptive fields. Global characteristics of the surface brightness distribution were represented in the population response of the neurons. The pattern of neuronal activity elicited in on-neurons and off-neurons in response to surface stimuli correlated with the isophot structure of the surface ( rav=0.86 for 23 cases). Therefore, separate descriptions of local and global brightness distributions originate at subcortical levels of the visual system.

Stimulus-dependent oscillatory activity in the lateral geniculate body of the cat.

Recent observations of synchronous oscillatory activity of cell assemblies in cat primary visual cortex [1] have led to a marked resurgence of interest in the functional role of periodic neuronal behavior in information processing [2]. In the current discussion, however, precortical oscillatory activities in the visual system appear to be neglected. Neuronal oscillatory activities in the gamma frequency range have been described in retinal ganglion cells and in cells of the lateral geniculate body [3]. Moreover, it has been demonstrated that neurons in cat lateral geniculate body (LGB) show appropriate average firing rates in response to scanned figures [4]. The present study investigates responses of three simultaneously recorded neurons in cat LGB, which were stimulated with a photograph of a white three-dimensional cylinder illuminated from the top (Fig. 1 a). The photograph was moved stepwise across the receptive field (RF) of three adjacent neurons in order to reconstruct a response profile for the object [5]. The average firing rate and the dominant period length of the oscillatory multiunit activity (MUA) of the three cells during the stepwise scanning were analyzed and mapped in scale with the mirror-inverted stimulus picture. The experiment was conducted on an adult unanaesthetized cat weighing about 2.5 kg two days after preparation. During preparation, the cat was anaesthetized with intravenous injection of ketalar; pressure points, injection sites, and cuts were additionally infiltrated with a local anaesthetic. Multiunit activity of three neurons (two offand one on-neuron) was recorded extracellularly from layer A of the left LGB with a tungsten microelectrode (tip diameter about 1 /zm). During the experiment, total immobilization was achieved by regular intravenous administration of flaxedil ( 5 1 0 mg kg1 h 1). The refractive power of the contralateral eye was corrected by an appropriate contact lens and the nictitating membrane was withdrawn by the application of neosynephrine. The ipsilateral eye was covered with an opaque occluder. The cat was artificially respirated and the heart rate was controlled. The experiment lasted about 90 min. At the end of the experiment the cat received a lethal dose of barbiturate. During the experiment, the cat's head was fixed facing a tangential screen at 1 m distance. The RF of the three neurons overlapped and had an eccentricity of 5.3 ° visual angle along the horizontal meridian. Extracellular MUA was measured and spike occurrence was detected with a Schmitt trigger. Data were collected with a sampling rate of 1 500 s~ and analyzed in histograms of 2 ms bin width. The photograph of the cylinder was projected on a tangent screen. The stimulus had a maximum intensity of 10.83 cd /m 2 and the constant background intensity was of 1.11 cd /m 2. The picture (total size about 1 3 ° x 10 °) could be moved stepwise horizontally and vertically following a grid of 10 x 10 equidistant points in scale with the whole stimulus, using two mirrors which were placed in the light beam. Beginning from the upper left point the stimulus was tachistoscopically presented 30 times for 500 ms (on-condition) interrupted by dark periods of 500 ms (offcondition) and was then moved stepwise to the lower right point of the grid. Thus, the whole stimulus was systematically scanned by the RF. For each of the 100 grid points of stimulus presentation a poststimulus time histogram (PSTH) of the MUA of the 30 repeated measures was calculated for the onand off-responses separately. Figures 1 b, c illustrate the PSTHs of one grid point for the offand on-condition. The corresponding autocorrelation functions (ACF), presented in Fig. 1 d, e, make the inherent periodicity more obvious. The analysis of periodicity is based on a method published previously [6]. For each histogram a dominant periodicity was estimated by ACF and fast Fourier transformation (FFT) with a maximum lag of 128 histogram bins. The estimations based on the analysis of the trend-reduced difference distribution of the original PSTHs. With the exception of one PSTH of the off-condition, all histograms could be classified as multimodal periodic. Figure 1 f, g shows maps of the normalized average firing rate of the offand on-response across the grid points

Modification of spontaneous unit discharge in the lateral geniculate body by a magnetic field

The effects of a 1230-G static magnetic field on spontaneous discharge frequency and discharge pattern of principle cells in the cat's lateral geniculate body (LGB) were examined. In 45% of cells studied, a decrease in frequency was seen after the field was turned on. This progressed, even after the field was turned off, with return to baseline after an average duration of 250 s. Onset typically was 75 s after the field was activated, with maximum effect occurring 135 sec thereafter. In 67% of those cells which exhibited a decrease in frequency and in 50% of those which did not, a change in discharge pattern, as reflected by the interspike interval histogram, was seen. When present, this was manifested as a decrease in short interspike intervals. The change in the interspike interval histogram usually persisted longer than the change in frequency. The gradual onset and prolonged time course of changes in LGB cell activity suggest either an alteration in the synaptic ionic environment or in neurotransmitter availability. It is hypothesized that strong magnetic fields produce a partial realignment of diamagnetically anisotropic molecules within the cell membrane, thereby distorting ion-specific channels sufficiently to alter their function.

Visual cortex contribution to the organization of eye movements produced by local electrical stimulation of the cat lateral geniculate body

Eye movements evoked by local electrical stimulation of the dorsal nucleus of the lateral geniculate body were analyzed after removal of the visual cortex and in intact animals during trials on awake cats. No significant difference was observed between the eye movement patterns of the two animal groups evoked by electrical stimulation. These movements could be classed into three main groups: those unassociated with the starting position of the eyes in orbit (or unidirectional movements), goal-directed, and centered movements, with direction depending on the initial position of the eyes in their orbits. Our findings indicate that the cortical visual areas are neither the principal nor an indispensable link in the chain for transmitting signals evoked by (electrically) stimulating the geniculate body from the cortical structures of the direct visual pathway towards the operative links of the oculomotor system. Potential pathways for conducting information from the dorsal nucleus of the lateral geniculate body to oculomotor system structures are discussed.

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.

Cortical control of the afferent flow in the cat lateral geniculate body

Single unit responses in the dorsal lateral geniculate body to stimulation of the optic chiasma (testing) and area 17 (conditioning) of the visual cortex were studied in unanesthetized cats immobilized with tubocurarine. Two types of unit responses were found: P-responses (considered to be of relay, or principal, cells) and I-responses (considered to be of interneurons), whose parameters differed distinctly. Interaction between stimulation of the visual cortex and optic chiasma consisted of depression of the ability of the P cells of the nucleus to respond to testing stimulation. It is suggested that cortical influences on stimulus conduction by P cells of the nucleus is based on postsynaptic inhibition with the participation of interneurons.

The effect of monocular pattern deprivation on the signal transmission by neurons of the cat lateral geniculate body.

The effect of monocular pattern deprivation on the signal transmission by neurons of the cat lateral geniculate body.

Analysis of unit activity in the cat lateral geniculate body

Spontaneous and evoked single unit activity of lateral geniculate body neurons was recorded extracellularly in acute experiments on cats. Eight groups of neurons differing in the durations of the minimal and mean interspike intervals of spontaneous unit activity, and in the latent period and duration of the first volley of spikes of evoked activity, were distinguished by analysis of the data. On the basis of this classification a scheme for interaction between neurons of the lateral geniculate body is suggested.

Characteristics of residual neurons during retrograde degeneration in the cat lateral geniculate body

The dynamics of structural and functional characteristics of residual neurons in the degenerating lateral geniculate body was studied in cats during the 4–12 months after division of all cortico-subcortical projection connections, including axons of relay cells of the lateral geniculate body [9]. Spontaneous and evoked activity of the residual cells, their number, and also the dimensions of the cell bodies were investigated. With lengthening of the postoperative period a decrease in the number of cells of the lateral geniculate body responding to photic stimulation and also destruction of their receptive fields were observed; 12 months after the operation the residual neurons of the lateral geniculate body lose their sensitivity to photic stimulation. Morphological investigation revealed a progressive reduction in the number of neurons in the degenerating lateral geniculate body and predominance of small neurons among them. The nature of interneuronal relations in the lateral geniculate body are discussed on the basis of the results.

Dependence of unit responses of the catlateral geniculate body on photic stimulus contrast

Unit responses in the lateral geniculate body of cats to photic stimuli of different contrast were investigated. The number of spikes in the initial phase of the responses (the first 30–45 msec) was found not to change at first, but then to decrease with an increase in the intensity of background illumination. The background intensity starting from which the response diminishes was shown to increase with an increase in the intensity of the test stimulus. The unit response is a linear function of the logarithm of stimulus contrast if the contrast is changed through variation of the intensity of the test stimulus. If contrast increases on account of a decrease in the intensity of background illumination the responses first increase and then remain unchanged. The range of contrasts within which the response is a linear function is narrowed if the intensity of the test stimulus is reduced. Counting the number of spikes in different time intervals of the response (Δt) showed that the greater the value of Δt (within the first 70–90 msec of the response) the steeper the curve of the number of spikes as a function of contrast. The Weber-Fechner law applies in the receptive field of the lateral geniculate body. The results are compared with those of some psychophysiological experiments.

The effect of reticular stimulation on binocular inhibition in the cat lateral geniculate body.

The effect of reticular stimulation on binocular inhibition in the cat lateral geniculate body.

Serotonin in the lateral geniculate

Serotonin was introduced, by means of a fine cannula, into the lateral geniculate body of cats immobilized with Flaxedil and artificially ventilated, while the electrical activity at the point of injection was monitored by means of microelectrodes. Doses of 1.25 to 30 μg dissolved in 0.5 to 2.0 μl of saline produced, in 2–30 min, changes in electrical activity characteristic of synchronization: increase in the rhythmicity and in the amplitude of the spontaneous gross waves and increase in the clustering of the spontaneous neuronal action potentials. At the same time the activity of neurons which produced action potentials of high amplitudes was decreased, the activity of neurons which produced action potentials of low amplitudes was increased. Action potentials of different amplitudes wete produced, in this case, by neurons of different types. Thus, in the lateral geniculate as in other thalamic nuclei studied in previous investigations, the synchronization of spontaneous activity seems to require the simultaneous excitation and inhibition of two different types of neurons. The action of serotonin on activity evoked by stimulation with brief flashes of light was limited to the decrease in the amplitude of the average gross response and the inhibition of only one type of neuron. This suggests that, in the lateral geniculate body, serotonin may be implicated in different ways in the different network structures responsible for the development of spontaneous as contrasted with evoked activity.

Threshold and temporal characteristic of unit responses of the cat lateral geniculate body to electrical stimulation of the optic tract

Unit responses of the lateral geniculate body of the immobilized cat to electrical stimulation of the optic tract were studied. Responses of about 80 cells were compared and histograms of latencies and thresholds of their responses to electrical stimulation of their afferents were plotted. The distribution of the cells by latent periods was bimodal and by thresholds monomodal. Correlation was established between the various parameters of the cell reponses to electrical stimulation of afferents and to light. Correlation analysis showed that the cell population investigated is heterogeneous and consists of three groups.

Corticofugal control of unit responses of the cat lateral geniculate body

Acute experiments on anesthetized cats showed that blocking the projection connections of the cortex unilaterally increased the number of lateral geniculate neurons which generated long-latency phasic responses and the number of spikes in the responses of single neurons. Unit responses were monophasic more frequently in the lateral geniculate body on the side of the operation than in the same structure on the opposite side. On the basis of these results a hypothesis is developed to explain the mechanisms of monomodal descending cortical effects in microsystems of neurons of the lateral geniculate body.

Visual radiation activity during a cortical penicillin discharge

The electrical behavior of 274 principal cells of the dorsal nucleus of the lateral geniculate body of cat has been studied during the discharge of a penicillin focus in the primary visual cortex. In 17% of the cells, spike activity was observed during the penicillin discharge. The activity consisted of 1–40 spikes at frequencies as high as 500/sec. When the penicillin discharge initiated a prolonged seizure, activity in the principal cells continued throughout the seizures at rates from 100–200/sec. The temporal properties of the activity and the detailed structure of single spikes studied with glass microelectrodes in the geniculate suggest that this activity is antidromic. Stimulation of the visual radiation at its origin in the geniculate at various times during a penicillin discharge revealed marked reduction in amplitude of the population response recorded at the terminus of the radiation in the cortex. The degree of reduction followed approximately the time course of the penicillin discharge and was great enough to suggest two additive etiologies, viz., refractoriness or occlusion during the penicillin discharge and depolarization of the radiation fiber terminals.

Characteristics of P-and I-cellsof the cat's lateral geniculate body

Lateral geniculate cells of the cat were characterized by their extracellular and intracellular responses to single pulse stimulation of optic tract and visual cortex. The characteristic responses of the P-cells was a chloride dependent IPSP following rapidly brief and variable excitation. The typical I-cell response was a high frequency discharge and an EPSP which reversed during the application of depolarizing currents. Optic tract and the cortical areas 17, 18 and 19 were equally effective in producing these responses.