The responses to illusory contours of neurons in cortex areas 17 and 18 of the cats

Responses to illusory contours (ICs) were sampled from neurons in cortical areas 17 and 18 of the anesthetized cats. For ICs sensitive cells, the differences of receptive field properties were compared when ICs and real contour stimuli were applied. Two hundred orientation or direction selective cells were studied. We find that about 42 percent of these cells were the ICs sensitive cells. Although their orientation or direction tuning curves to ICs bar and real bars were similar, the response modes (especially latency and time course) were different. The cells’ responses to ICs were independent of the spatial phases of sinusoidal gratings, which composed the ICs. The cells’ optimal spatial frequency to composing gratings the ICs was much higher than the one to moving gratings. Therefore, these cells really responded to the ICs rather than the line ends of composing gratings. For some kinds of velocity-tuning cells, the optimal velocity to moving ICs bar was much lower than the optimal velocity to moving bars. The present results demonstrate that some cells in areas 17 and 18 of cats have the ability to respond to ICs and have different response properties of the receptive fields to ICs and luminance boundaries via different neural mechanisms.     

Responses of class R3 retinal ganglion cells of the frog to moving configurational bars: effect of the stimulus velocity

Discrimination of 'prey' (bars elongated in the direction of movement; W- or H-orientation) and 'non-prey' (bars perpendicular to the direction of movement; A- or V-orientation) stimuli in freely moving amphibians is velocity-invariant. Whether or not this phenomenon is present in cells belonging to a general decision making neuronal process remains questionable. Present investigations report the effect of the angular velocity of the stimulus on the discrimination function of class R3 (transient ON-OFF) retinal ganglion cells. The main conclusions of this work are the following: (1) irrespective of the angular velocity, class R3 neurons always prefer vertically (A-) to horizontally (W-) oriented stripes as long as the stimulus length remains inferior to the receptive field size; (2) this preference for small A-stimuli is best expressed when stimuli are moved at V = 7.6 degrees/s; (3) a preference reversal is induced by stripes longer than the receptive field via a dual process involving both spatial and temporal mechanisms; (4) this preference reversal is velocity-dependent: the longer the bar, the faster the velocity should be.     

Single-cell responses in the ectostriatum of the zebra finch

The responses of single cells to computer-generated spots, bars, gratings, and motion-in-depth stimuli were studied in the ectostriatum and the adjacent neostriatum of the zebra finch, Taeniopygia guttata. No differences in neuronal properties could be detected between ectostriatum and neostriatum. The receptive fields of ectostriatal neurons are large, often extending over the entire visual field of the contralateral eye, and have oddly defined borders. The centers of the receptive fields, located in the foveal region, generally yielded better responses than the periphery, and exhibited different subdivisions. Neurons responded selectively to moving bars, preferring those moving parallel to their longest axis. An SDO (sensitivity, direction, orientation) analysis of responses to sinusoidal gratings showed that all orientations were equally represented by ectostriatal neurons, while there was a slight preference for forward and upward movements. The neurons also showed preferences for gratings of a particular spatial frequency, and responded vigorously to stimuli moving towards the eye (looming). Our results indicate that the ectostriatum is involved in both detecting displacement of the surround and in stimulus identification. By comparison with results obtained in the extrastriate cortex of mammals, it is concluded that the homology of the ectostriatum with the extrastriate cortex of mammals, which was proposed on the basis of hodological findings, is supported by our study.Abbreviations Di index of directionality - HW HH half-width at half-height - PLLS posterolateral lateral suprasylvian cortex - PMLS posterior medial lateral suprasylvian area - PSTH poststimulus time histogram - SDO sensitivity, direction, orientation     

Orientation selectivity and spatial frequency characteristics of receptive fields of occipital cortical neurons in cats

Spatial frequency characteristics of receptive fields of occipital cortical neurons were investigated in cats during presentation of visual stimuli consisting of gratings in four or eight standard orientations. The maximal increase in discharge frequency of the neurons was observed when the grating was presented in one particular orientation, which was taken to be optimal for those particular neurons. Responses of some neurons to presentation of gratings in nonoptimal orientations were less than optimal; inhibition of activity below the spontaneous discharge level was observed in other cells in this case. Maximal inhibition was observed to the orientation perpendicular to optimal. Inhibition of unit activity evoked by presentation of gratings in the nonoptimal orientation was shown to be a function of spatial frequency.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 13, No. 3, pp. 227–232, May–June, 1981.     

胼胝体输入对猫皮层17/18交界区细胞方向和取向选择性的影响

用抑制性神经递质GABA阻断胼胝体输入、用微机控制的运动光棒作为视觉刺激,用金属电极胞外记录技术,研究猫皮层17/18区交界附近细胞方向选择性和取向选择性的变化.在被检测的48个细胞中,50%细胞的方向选择性强度,54.2%细胞的取向选择性强度发生了改变;约20%细胞的最优反应方向或.及最优取向发生了10-30°的偏移;共有56.2%细胞的方向选择性、58.3%细胞的取向选择性受到明确的影响.这些结果表明胼胝体对皮层细胞视觉反应的贡献是多方面的.     

Isoluminant monochromatic and polychromatic visual backgrounds alter response characteristics of cat visual neurons after stimulation with stationary and moving light bars

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum PSTH peaks of some 40% of the neurons tested was influenced by both moving and stationary bars. About 2 thirds of maximum peak-sensitive cells showed also altered direction selectivity. Latencies and field widths, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.     

Monochromatic and polychromatic visual backgrounds influence the response of area 17 and 18 neurons after stimulation with stationary and moving light bars

The role of colour vision in night-active cats has not been elucidated completely hitherto. In order to assess the colour sensitivity in cat cortical neurons we used large isoluminant computer-generated monochromatic and polychromatic background stimuli which were superimposed on moving and stationary (on/off) light bars. Background stimuli were moved at different speeds either inphase or antiphase. The modulatory effect of the visual noise on the neuronal bar was the primary objective of the study. The maximum amplitudes of some 40% of the neurons tested was influenced by both moving and stationary bars. About two thirds of amplitude-sensitive cells showed aldo altered direction selectivity. Latencies and field widths, on the other hand, turned out to be rather stable. The retino-cortical conduction time was not influenced either. In conclusion, a large portion of cat cortical visual neurons is remarkably sensitive to the spectral composition of the visual noise process surrounding the stimulating light bar.     

Computational models of visual neurons specialised in the detection of periodic and aperiodic oriented visual stimuli: bar and grating cells

Computational models of periodic- and aperiodic-pattern selective cells, also called grating and bar cells, respectively, are proposed. Grating cells are found in areas V1 and V2 of the visual cortex of monkeys and respond strongly to bar gratings of a given orientation and periodicity but very weakly or not at all to single bars. This non-linear behaviour, which is quite different from the spatial frequency filtering behaviour exhibited by the other types of orientation-selective neurons such as the simple cells, is incorporated in the proposed computational model by using an AND-type non-linearity to combine the responses of simple cells with symmetric receptive field profiles and opposite polarities. The functional behaviour of bar cells, which are found in the same areas of the visual cortex as grating cells, is less well explored and documented in the literature. In general, these cells respond to single bars and their responses decrease when further bars are added to form a periodic pattern. These properties of bar cells are implemented in a computational model in which the responses of bar cells are computed as thresholded differences of the responses of corresponding complex (or simple) cells and grating cells. Bar and grating cells seem to play complementary roles in resolving the ambiguity with which the responses of simple and complex cells represent oriented visual stimuli, in that bar cells are selective only for form information as present in contours and grating cells only respond to oriented texture information. The proposed model is capable of explaining the results of neurophysiological experiments as well as the psychophysical observation that the perception of texture and the perception of form are complementary processes. Received: 4 June 1996 / Accepted in revised form: 7 October 1996     

Independent component analysis of natural image sequences yields spatio-temporal filters similar to simple cells in primary visual cortex.

Simple cells in the primary visual cortex process incoming visual information with receptive fields localized in space and time, bandpass in spatial and temporal frequency, tuned in orientation, and commonly selective for the direction of movement. It is shown that performing independent component analysis (ICA) on video sequences of natural scenes produces results with qualitatively similar spatio-temporal properties. Whereas the independent components of video resemble moving edges or bars, the independent component filters, i.e. the analogues of receptive fields, resemble moving sinusoids windowed by steady Gaussian envelopes. Contrary to earlier ICA results on static images, which gave only filters at the finest possible spatial scale, the spatio-temporal analysis yields filters at a range of spatial and temporal scales. Filters centred at low spatial frequencies are generally tuned to faster movement than those at high spatial frequencies.     

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.     

Asymmetric temporal properties in the receptive field of retinal transient amacrine cells

The speed of signal conduction is a factor determining the temporal properties of individual neurons and neuronal networks. We observed very different conduction velocities within the receptive field of fast-type On-Off transient amacrine cells in carp retina cells, which are tightly coupled to each other via gap junctions. The fastest speeds were found in the dorsal area of the receptive fields, on average five times faster than those detected within the ventral area. The asymmetry was similar in the On- and Off-part of the responses, thus being independent of the pathway, pointing to the existence of a functional mechanism within the recorded cells themselves. Nonetheless, the spatial decay of the graded-voltage photoresponse within the receptive field was found to be symmetrical, with the amplitude center of the receptive field being displaced to the faster side from the minimum-latency location. A sample of the orientation of varicosity-laden polyaxons in neurobiotin-injected cells supported the model, revealing that approximately 75% of these processes were directed dorsally from the origin cells. Based on these results, we modeled the velocity asymmetry and the displacement of amplitude center by adding a contribution of an asymmetric polyaxonal inhibition to the network. Due to the asymmetry in the conduction velocity, the time delay of a light response is proposed to depend on the origin of the photostimulus movement, a potentially important mechanism underlying direction selectivity within the inner retina.     

视皮层反馈对猫外膝体神经元方位调制特性的影响

以扫描正弦光栅作为刺激,用冰冻法毁损皮层17、18、19区和外侧上雪氏回(LS区)来阻断皮层对外膝体的反馈投射,记录并描绘了猫外膝体597个细胞的方位调制特性.去视皮层猫外膝体神经元的平均方位选择性强度(Bias)为0.154,与正常猫(0.155)几乎相同,其最优方位偏向于水平方位.与正常猫外膝体不同的是,去视皮层猫外膝体失去了最优方位的切向分布规律,用GABA或KCl压抑皮层活动得到了相近的实验结果.结果说明正常外膝体的最优方位切向分布规律来自皮层反馈投射.     

Orientation selectivity of visual cortical neurons at different stimulus intensities in cats

Orientation selectivity of 24 neurons in area 17 of the visual cortex at different intensities of test bars of light, flashing against a constant light background in the center of the receptive field, was investigated in acute experiments on immobilized cats. Five neurons were invariant in orientation tuning to stimulus intensity (contrast): Although the magnitude of the response and acuteness of orientation selectivity were modified, preferential orientation was unchanged. More than half of the cells studied (13) were classed as noninvariant, for their preferential orientation was significantly shifted by 22–90° with a change in contrast. Small shifts of the peak of orientation selectivity, not statistically significant, were observed for the other neurons. Invariant neurons, unlike noninvariant, were characterized by preferential horizontal and vertical orientation, a lower frequency of spontaneous and evoked discharges, and the more frequent presence of receptive fields of simple type. The mechanisms of the change of orientation selectivity during contrast variation and also the different use of the two types of cells in orientation detection operations are discussed.     

Spatial frequency characteristics of receptive fields of neurons in the lateral suprasylvian area of the cat cortex

Two-dimensional spatial frequency characteristics of receptive fields of 46 neurons in the lateral suprasylvian area of the cat cortex were obtained. These receptive fields possessed orientation anisotropy. Peak frequencies lay in the frequency region below 1.5 cycles/deg. The transmission band width was measured during optimal orientation of test gratings in 21 neurons. It averaged 1.47±0.6 octave. In the remaining neurons the lower boundary frequency was shifted into the region of spatial frequencies below the range used. During nonoptimal orientation of test gratings, inhibition of the discharge was observed in 17 neurons. The inhibitory spatial frequency characteristics of six neurons were of the narrow band type, and averaged 1.1±0.6 octave.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 14, No. 6, pp. 608–614, November–December, 1982.     

Response properties of visual interneurons to motion stimuli in the praying mantis,Tenodera aridifolia

Intracellular responses of motion-sensitive visual interneurons were recorded from the lobula complex of the mantis, Tenodera aridifolia. The interneurons were divided into four classes according to the response polarity, spatial tuning, and directional selectivity. Neurons of the first class had small, medium, or large receptive fields and showed a strong excitation in response to a small-field motion such as a small square moving in any direction (SF neurons). The second class neurons showed non-directionally selective responses: an excitation to a large-field motion of gratings in any direction (ND neurons). Most ND neurons had small or medium-size receptive fields. Neurons of the third class had large receptive fields and exhibited directionally selective responses: an excitation to a large-field motion of gratings in preferred direction and an inhibition to a motion in opposite, null direction (DS neurons). The last class neurons had small receptive fields and showed inhibitory responses to a moving square and gratings (I neurons). The functional roles of these neurons in prey recognition and optomotor response were discussed.     

猫外膝体神经元非寻常的方位调谐特性——Ⅰ、在正常猫的研究

在九只成年猫上用玻璃电极记录了单个外膝体神经元对不同方位的移动正弦光栅刺激的反应共详细测定了４００个细胞的方位调谐特性。少数外膝体神经元具有非寻常的方位调谐特性,包括：具蝴蝶状调谐曲线的方位调谐特性;双调谐的方位调谐特性和最优方位随刺激光栅空间频率的改变而变化的方位调谐特性。这些细胞非寻常的方位调谐特性往往伴随着非寻常的空间频率调谐特性。空们的方位调谐特性和空间频率调谐特性都不能用Ｓｏｏｄａｋ等提     

Patterns in the discharge of simple and complex visual cortical cells

The activity of visual cortical neurons (area 17) was recorded in anaesthetized cats in response to sinusoidal drifting gratings. The statistical structure of the discharge of simple and complex cells has been studied as a function of the various parameters of a drifting grating: spatial frequency, orientation, drifting velocity and contrast. For simple cells it has been found that the interspike interval distributions in response to drifting gratings of various spatial frequencies differ only by a time scale factor. They can be reduced to a unique distribution by a linear time transformation. Variations in the spatial frequency of the grating induce variations in the mean firing rate of the cell but leave unchanged the statistical structure of the discharge. On the contrary, the statistical structure of the simple cell activity changes when the contrast or the velocity of the stimulus is varied. For complex cells it has been found that the invariance property described above for simple cells is not valid. Complex cells present in their activity in response to visual stimuli two different firing patterns: spikes organized in clusters and spikes that do not show this organization ('isolated spikes'). The clustered component is the only component of the complex cell discharge that is tuned for spatial frequency and orientation, while the isolated spike component is correlated with the contrast of the stimulus.     

猫后内侧上雪氏区视神经元对运动棒反应的取向和方向特征

猫后内侧上雪区（ｐｏｓｔｅｒｏｍｅｄｉａｌｌａｔｅｒａｌｓｕｐｒａｓｙｌｖｉａｎａｒｅａ,ＰＭＬＳ）的绝大多数神经元（１７１／２００）对运动棒的取向调谐,６２％（１２４／２００）细胞的取向调谐宽度（半高波宽）小于９０°：按方向选择性和取向选择性可分辨出几类特征明显的细胞类型：１、强取向和强方向选择性细胞;２、强取向调谐的双向选择细胞;３、弱取向调谐的强方向选择细胞;４、无取向无方向选择性细胞;以及５、特征不明显的或中间类型细胞。它们与最近光学记录揭示的鹰猴中颞叶视区（ｍｉｄｄｌｅｔｅｍｐｏｒａｌｖｉｓｕａｌａｒｅａ,ＭＴ）的组织有很好的吻合。     

Spatial properties of goldfish ganglion cells

We systematically classified goldfish ganglion cells according to their spatial summation properties using the same techniques and criteria used in cat and monkey research. Results show that goldfish ganglion cells can be classified as X-, Y-, or W-like based on their responses to contrast-reversal gratings. Like cat X cells, goldfish X-like cells display linear spatial summation. Goldfish Y-like cells, like cat Y cells, respond with frequency doubling at all spatial positions when the contrast-reversal grating consists of high spatial frequencies. There is also a third class of neurons, which is neither X- nor Y-like; many of these cells' properties are similar to those of the "not-X" cells found in the eel retina. Spatial filtering characteristics were obtained for each cell by drifting sinusoidal gratings of various spatial frequencies and contrasts across the receptive field of the cell at a constant temporal rate. The spatial tuning curves of the cell depend on the temporal parameters of the stimulus; at high drift rates, the tuning curves lose their low spatial frequency attenuation. To explore this phenomenon, temporal contrast response functions were derived from the cells' responses to a spatially uniform field whose luminance varied sinusoidally in time. These functions were obtained for the center, the surround, and the entire receptive field. The results suggest that differences in the cells' spatial filtering across stimulus drift rate are due to changes in the interaction of the center and surround mechanisms; at low temporal frequencies, the center and surround responses are out-of-phase and mutually antagonistic, but at higher temporal rates their responses are in-phase and their interaction actually enhances the cell's responsiveness.     

Orientation-sensitive Neurons in the Brain of the Honey Bee (Apis mellifera)

Recent behavioural experiments have shown that bees are able to distinguish vertically presented patterns with orientation cues, although the locations of areas of black are randomized. To discriminate between two orientations, the bees must possess more than one orientation-sensitive neuron type. Therefore, the aim is to search for different types of orientation-sensitive cells of the honey bee, and measure their receptive field, velocity sensitivity and contrast sensitivity. Orientation-sensitive cells with two different types of orientation tuning-curves were recorded intracellularly in the mid-brain of the honey bee when the stimulus was a narrow bar (bar width = 5 degrees ). These cells are sensitive to bar movement within their large receptive field, which covers the visual field of one eye. They are quite distinct from the well-known directional motion detectors. The contrast sensitivity of the orientation-sensitive cells recorded in this study corresponds to results from behavioural experiments. The velocity-sensitivity curves of the orientation-sensitive cells differ from those of the direction-sensitive cells. Measurements of orientation sensitivity and contrast sensitivity when the stimulus is a wide bar (bar width = 10 degrees ), done in different eye regions, suggest that each orientation-sensitive cell receives visual signals from an array of orientational subunits within its receptive field. The correspondence between these physiological results and the results of recent behavioural experiments are discussed. Copyright 1997 Elsevier Science Ltd. All rights reserved