Cone contributions to cat retinal ganglion cell receptive fields

Extracellular microelectrode recordings were made from ganglion cells of the intact, in situ eyes of adult common domestic cats. Three different photopic systems, with peak spectral sensitivities at 450, 500, and 556 nm, were observed. All ganglion cells received input from a cone system with a peak spectral sensitivity of 556 nm. The blue-sensitive cone system was observed in about one-half of the ganglion cells studied. In each case the 450-nm cone system contributed to only one functional type of response, either ON or OFF, in the same cell. The other two photopic systems most often contributed to both the ON and OFF responses of an individual ganglion cell. In four cases the 450-nm cone system mediated responses that were opponent to those of the other two photopic systems. The third photopic mechanism has a peak spectral sensitivity at 500 nm and contributed to most receptive field surrounds and many receptive field centers. It is distinguished from the rod system by the occurrence of a break in both dark-adaptation curves and increment-sensitivity curves. No apparent differences in receptive field cone contributions between brisk-sustained and brisk-transient cells were seen.     

Antagonist actions of bicuculline methiodide and picrotoxin on extrasynaptic gamma-aminobutyric acid receptors

The effects of picrotoxin and bicuculline methiodide to block depolarizing responses of extrasynaptic receptors for gamma-aminobutyric acid (GABA) are compared using excitability testing of myelinated axons in amphibian peripheral nerve. The actions of the antagonists appear both complex and dissimilar. Picrotoxin (10-1000 microM) produces large reversible depressions of the maximal response to GABA (0.01-10mM) and increases the EC50 from 0.33 to 12.6 mM. With high concentrations of agonist and antagonist an insensitive component is apparent. The action of picrotoxin is not classically noncompetitive: it may represent a mixed antagonism (competitive and noncompetitive) or a noncompetitive one, masked by the presence of receptor reserve and (or) secondary depolarizing influences (e.g., GABA-evoked [K+] o accumulation). Bicuculline methiodide (10-200 microM) shifts the GABA concentration-response curve to the right; maximal responses persist and are even enhanced. The impression that bicuculline methiodide has a competitive action is supported by analysis of its inhibition of responses to low concentrations of the agonist. It is suggested that the enhancement of GABA responses by bicuculline methiodide and their apparent resistance to block by picrotoxin may be due to a common secondary effect of the antagonists such as a decrease in membrane conductance to K+ and (or) block of transmitter uptake.     

Spatio-temporal organization of receptive fields of the cat striate cortex

The responses of cortical cells to gratings and bars were compared. The excitatory and inhibitory on-and off-zones of a simple cell are composed of on- and off-subfields of CGL. Any zone is formed by an opponent pair of subfields one of which gives an excitatory effect, the other — inhibitory. Such organization assumes the linear properties of a simple field. The deviations from linearity are due to spatial dis-placements of the subfields, heterogeneity of subfields, or the absence of one subfield in the opponent pair. Subfields may be both phasic and tonic, even in the same RF. Analysis of the most common type of a complex cell with modulated responses against unmodulated background shows that a mask eliminating stimulation of any half of the RF causes (according to the theory of filtres) increasing the bandwidth due to the increase or the appearance of responses to side low and high frequencies. The modulated components of the responses from both halves of the RF are out of phase. Analysis of this fact and the responses to thin bars suggests that a complex field is formed by linear and nonlinear subsystems converging onto output neuron. Other types of complex fields are organized by different combinations of subsystems. Limited in area by masking the RF responds to much higher spatial frequencies than the whole RF. The optimal frequency in two-dimensional spatial frequency characteristics of the RF does not change with orientation. Simple RFs and a part of complex RF calculate the amplitude and the phase of the stimulus, the other part of complex RFs (with unmodulated response) calculate only amplitude. Given all this, the RFs are grating filters of spatial frequency.     

Dependence of center radius on temporal frequency for the receptive fields of X retinal ganglion cells of cat

We examined the dependence of the center radius of X cells on temporal frequency and found that at temporal frequencies above 40 Hz the radius increases in a monotonic fashion, reaching a size approximately 30% larger at 70 Hz. This kind of spatial expansion has been predicted with cable models of receptive fields where inductive elements are included in modeling the neuronal membranes. Hence, the expansion of the center radius is clearly important for modeling X cell receptive fields. On the other hand, we feel that it might be of only minor functional significance, since the responsivity of X cells is attenuated at these high temporal frequencies and the signal-to-noise ratio is considerably worse than at low and midrange temporal frequencies.     

Investigation of functional organization of receptive fields in the cat visual cortex

Receptive fields of neurons in Area 17 of the visual cortex were investigated in cats. Concentrically shaped fields, fields responding selectively to orientation of a strip or edge, and fields which can be regarded as intermediate between the first two types are described. The boundary between zones of summation and of lateral inhibition coincides in some receptive fields with the boundary between central and peripheral zones with opposite forms of response, while in other fields they do not coincide. For some cells there is no peripheral zone or it may disappear with worsening of the state of function. Cells were observed for which an increase in area of the stimulus in the central zone inhibits the response reaction. Analysis of these data suggests that several cells of the geniculate ganglion converge on some cortical neurons, and several cortical cells on others. An effect of adaptive inhibition was found in which constant illumination of an area in the center of the receptive field inhibits the response in another part. It is shown that this effect is unconnected with the action of scattered light. Constant illumination of the peripheral part of the receptive field deinhibits adaptive inhibition. The boundary between the zones of summation and of lateral inhibition coincides with the boundary between the zones of adaptive inhibition and deinhibition.I. V. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 1, No. 1, pp. 90–100, July–August, 1969.     

Inhibitory mechanisms within the receptive fields of X-and Y-type retinal ganglion cells of the cat (author's transl)]

Two-stages of the inhibitory mechanisms were assumed within the on-center receptive field (RF) of the cat's retinal ganglion cell on the basis of the following two experiments: 1) Effect of background intensity upon the magnitude of the response to the RF-centered spot of stimulus, and 2) the time course of the inhibitory effect when the additional spot of light is presented in the same RF center region. The first stage is an inhibitory feed-back from horizontal cell to the photoreceptor. Both X-and Y-fields have this feed-back route. By this gain control machanisms, the ganglion cell will respond to the intensity ratio of the spot to the backgound. The second stage of inhibitory mechanism in X-field is the feed-back from sustained amacrine cell to the bipolar cell. Above two stages of feed-back mechanism in X-field explain the strong maintained suppressive effect produced by the additional spot of light. On the other hand, the Y-type ganglion cell will recive the inhibitory input via feed-forward path from trannsient amacrine cell. This explains the transient on- and of f-suppressive effects     

The effect of strychnine, bicuculline, and picrotoxin on X and Y cells in the cat retina

The effect of intravenous strychnine and the GABA antagonists picrotoxin and bicuculline upon the discharge pattern of center-surround-organized cat retinal ganglion cells of X and Y type were studied. Stimuli (mostly scotopic, and some photopic) were selected such that responses from both on and off-center cells were either due to the center, due to the surround, or clearly mixed. Pre-drug control responses were obtained, and their behavior following administration of the antagonists was observed for periods up to several hours. X-cell responses were affected in a consistent manner by strychnine while being unaffected by GABA antagonists. All observed changes following strychnine were consistent with a shift in center-surround balance of X cells in favor of the center. For Y-cell responses to flashing annuli following strychnine, there was either no shift or a relatively small shift in center-surround balance. Compared to X-cell responses to flashing lights, those of Y cells were very little affected by strychnine and in most cases were unaffected. It thus appears that glycine plays a similar role in receptive field organization of X cells as does GABA in Y cells (Kirby and Enroth-Cugell, 1976. J. Gen. Physiol. 68:465-484).     

Construction of complex receptive fields in cat primary visual cortex.

In primary visual cortex, neurons are classified into simple cells and complex cells based on their response properties. Although the role of these two cell types in vision is still unknown, an attractive hypothesis is that simple cells are necessary to construct complex receptive fields. This hierarchical model puts forward two main predictions. First, simple cells should connect monosynaptically to complex cells. Second, complex cells should become silent when simple cells are inactivated. We have recently provided evidence for the first prediction, and here we do the same for the second. In summary, our results suggest that the receptive fields of most layer 2+3 complex cells are generated by a mechanism that requires simple cell inputs.     

Responses of receptive fields of frog retinal ganglion cells to the leading and trailing edges of moving stimuli

The position of on- and off-discharge centers in class 1 and 3 receptive fields of the frog retina was determined with the aid of moving bars of different lengths. On- and off-centers of receptive fields of the first group coincide, those of the second are spatially separate, and in fields of the 3rd group the discharge center of one contrast sign occupies the central position and discharge centers of the opposite sign are located at the periphery, to its right and left. Receptive fields of the frog retina thus have features which approximate them to the concentric receptive fields of geniculate neurons and the fields of the cat visual cortex. Asymmetry in the responses was found: during movement in opposite directions the distance between the discharge centers changed, during movement to one side only one of the peripheral centers was revealed, whereas during movement to the other side the second center was revealed on the opposite side of the receptive field. This asymmetry of spatiotemporal relations in the receptive fields is similar to that found in the fields of cortical neurons and is connected with their directional properties.Research Institute of Applied Mathematics and Cybernetics, N. I. Lobachevskii State University, Gor'kii. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 75–85, January–February, 1980.     

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.     

Heterogeneity of neuron populations with complex receptive fields in the cat visual cortex

The selectivity of striate neurons with complex receptive fields to the orientation, direction, and velocity of movement of various stimuli was investigated in unanesthetized and uncurarized cats. On the basis of all characteristics obtained by the study of single-unit responses to a stationary flickering slit, a moving spot of light, and a moving oriented stimulus, four groups of complex neurons were distinguished. The characteristics of group I neurons indicate a mechanism of orientation selectivity in the organization of their receptive fields, group IV neurons have a mechanism of directional selectivity, and neurons of groups II and III possess both mechanisms. The existence of separate neuronal systems coding the orientation and direction of stimulus movement is suggested.V. Kapsukas State University, Vilnius. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 109–116, March–April, 1979.     

Structure of receptive fields of hyppocampal visually-sensitive neurons in the cat

We studied the structure of receptive fields (RF) in the visually sensitive CA1 and CA3 fields of the dorsal hippocampus in alert cats subjected to pretrigeminal section of the brain stem. Scanning with moving stimuli and mapping the whole RF area with point by point application of a stationary stimulus, we studied 76 RF neurons. We found no significant differences in the response characteristics of neurons of fields CA1 and CA3. Our data are a basis for classifying the neurons in the following groups: homogeneous RF structure of the RF (54%) and nonhomogeneous structure (28%) and weak reaction to the standard stimulus, but a strong reaction to movement (18%). The results showed that responses of some of the hippocampal neurons exhibit high specificity. Thus, 9% of the neurons with nonhomogeneous RF structure disclosed with static stimuli reacted variously to a change in contrast and contours of moving stimuli. The data presented indicate that visually sensitive neurons of the hippocamus have a relatively well-developed mechanism for processing visual sensory information and this obviously ensures participation of the limbic system in visually controlled behavior of the animal.Institute of Experimental Biology, Academy of Sciences of the Armenian SSR, Yerevan. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 160–167, March–April, 1991.     

Organization of receptive fields of motion-senstitive neurons in the cat pulvinar

The distribution of 70 visually sensitive neurons in the cat pulvinar sensitive to motion in the receptive fields was studied. The experimental results showed that components with directional characteristics are present in the structure of these fields of both direction-selective and unselective neurons. In the receptive fields of direction-selective neurons the directional elements of the substructure have identical preferred directions, which coincide with the preferred directions of response to stimulus movement over the entire receptive field. The organization of receptive fields of direction-selective neurons of the visual association structure thus does not differ significantly from that of analogous fields of visual projection neurons. Directional elements of the receptive fields of direction-unselective neurons were found to have different preferred directions, thereby providing a basis for organization of the nondirectional response of the neuron to a stimulus moving across the entire receptive field.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 14, No. 4, pp. 339–346, July–August, 1982.     

Neuronal organization of the left celiac ganglion in the cat

Unit responses of the isolated left celiac ganglion to stimulation of various nerves of the solar plexus were studied by intracellular microelectrode recording in cats before and after degeneration of the preganglionic fibers. The resting potential of the ganglionic neurons was ?62.2±2.9 mV and the amplitude of the spike potential 72.4±3.2 mV. The spike was followed by after-hyperpolarization with a mean amplitude of 24% of the spike amplitude and a duration of between 25 and 180 msec. A characteristic feature of the ganglion was the presence of orthodromic unit responses to stimulation of peripheral nerve fibers of the solar plexus. The higher threshold of activation of the neurons by peripheral fibers than by preganglionic fibers and the preservation of orthodromic unit responses to stimulation of peripheral nerves after degeneration of the preganglionic fibers are evidence that the peripheral reflex arc is closed in this ganglion. Neurons of the left celiac ganglion are divided into three groups. Only preganglionic fibers of the splanchnic nerve with different properties converge on the neurons of the first group (the most numerous); only afferent fibers of peripheral nerves converge on the neurons of the third group (the least numerous); both types of fibers terminate on neurons of the second group. This convergence may lie at the basis of the mechanism of the centrifugal and peripheral reflex interaction in the ganglion for coordinated visceral activity.     

A model for the temporal organization of X- and Y-type receptive fields in the primate retina

A model is proposed for the temporal characteristics of X-and Y-type responses of ganglion cells in the primate retina. The main suggestions of the model are: (I) The X-type temporal response is determined primarily by the delay between center and surround contributions. (II) The Y-type response is generated in the inner plexiform layer by a derivativelike operation on the bipolar cell's input, followed by a rectification in the convergence of these inputs onto the Y-ganglion-cell. (III) The derivative-like operation is obtained by recurrent inhibition in the dyad synaptic structure.The X-and Y-type responses predicted by the model, for a variety of stimuli, were examined and compared with available electrophysiological recordings. Finally, certain predictions derived from the model are discussed.