Quantification of directional and orientational selectivities of visual neurons to moving stimuli

Directional and orientational components usually coexist and are mixed in the cell's overall responses when moving optical stimuli are used to study the response characteristics of visual neurons. While these two properties were quantified with all the previous methods for data analysis, their effects could not be efficiently separated from each other, and thus the analyses were imperfect. In this paper, theoretical evidence and examples are provided to show the defects of the old methods. In order to separate the two components completely, we propose to apply optimal regression analysis with the sine-cosine function series as the fundamental variables. Based on this separation, we defined the orientational selectivity as variation of response strength with orientation and performed integration and averaging to quantify the two properties [cf. Eqs. (5) and (6)]. The present method has the advantages of completeness and accuracy, and can detect some details which would have been missed by other methods. An explanation of the intrinsic implications of the method and our comprehension of directional and orientational selectivities and preferred direction and orientation are also given. Received: 4 January 1993/Accepted in revised form: 1 July 1993     

How to unconfound the directional and orientational information in visual neuron's response

When drifting bars or gratings are used as visual stimuli, information about orientation specificity (which has a period of 180°) and direction specificity (which has a period of 360°) is inherently confounded in the response of visual cortical neurons, which have long been known to be selective for both the orientation of the stimulus and the direction of its movement. It is essential to unconfound or separate these two components of the response as they may respectively contribute to form and motion perception, two of the main streams of information processing in the mammalian brain. Wörgötter and Eysel (1987) recently proposed the Fourier transform technique as a method of unconfounding the two components, but their analysis was incomplete. Here we formally develop the mathematical tools for this method to calculate the peak angles, bandwidths, and relative strengths, the three most important elements of a tuning curve, of both the orientational and the directional components, based on the experimentally-recorded neuron's response polar-plot. It will be shown that, in the 1-D Fourier decomposition of the polar-plot along its angular dimension, (1) the odd harmonics contain only the directional component, while the even harmonics are contributed to by both the orientational and the directional components; (2) the phases and the amplitudes of all the harmonics are related, respectively, to the peak angle and the bandwidth of the individual component. The basic assumption used here is that the two components are linearly additive; this in turn is immediately testable by the method itself.     

A model of the human visual system in its response to certain classes of moving stimuli

The purpose of this study is to construct a functional model of the human visual system in its response to certain classes of moving stimuli.Experimental data are presented describing the interdependence of the input variables, temporal frequency, spatial period, etc., for two constant response states, viz. threshold motion response and threshold flicker response. On the basis of these data, two basic units are isolated, a vertical (V) unit and a horizontal (H) unit. The H-unit is identified with the Reichardt multiplier (Reichardt and Varju, 1959), and the V-unit with the de Lange filter (de Lange, 1954).A definition of the general motion response of the H-units is obtained, and this is then reduced to an expression which may be applied directly to the observed motion response data. By this method, Thorson's simplification of the Reichardt scheme (Thorson, 1966) is adopted for the H-unit and total and relative (population) weighting factors, associated with the H-unit output, are defined.In order to reconcile the theoretical square-wave threshold motion response with the experimental data, Thorson's simplification is modified with the introduction of a low-pass filter on the output. The amended scheme is shown to predict a (temporal) frequency-dependent phase-sensitivity. This prediction is tested experimentally, and its validity indicated.     

Responses of medullary neurons to moving visual stimuli in the common toad

Summary Intracellular recording and labeling of cells from the toad's (Bufo bufo spinosus) medulla oblongata in response to moving visual (and tactual) stimuli yield the following results. (i) Various response types characterized by extracellular recording in medullary neurons were also identified intracellularly and thus assigned to properties of medullary cell somata. (ii) Focussing on monocular small-field and cyclic bursting properties, somata of such neurons were recorded most frequently in the medial reticular formation and in the branchiomotor column but less often in the lateral reticular formation. (iii) Visual object disrimination established in pretectal/tectal networks is increased in its acuity in 4 types of medullary small-field neurons. The excitatory and inhibitory inputs to these neurons evoked by moving visual objects suggest special convergence likely to increase the filter properties. (iv) Releasing conditions, temporal pattern, and refractoriness of cyclic bursting neurons resemble membrane characteristics of vertebrate and invertebrate neurons known to play a role in premotor/motor activity. (v) Integrating functions of medullary cells have an anatomical correlate in the extensive arborizations of their dendritic trees; 5 morphological types of medullary neurons have been distinguished.Abbreviations A stripe moving in antiworm configuration - (W) moving in worm configuration - S square - BMC branchiomotor column - EPSP excitatory postsynaptic potential - IPSP inhibitory postsynaptic potential - RetF medullary reticular formation - RF receptive field - M neurons response properties of medullary neurons - T neurons classes of tectal neurons - TH neurons classes of thalamic/pretectal neurons - tr.tb.d. tractus tecto-bulbaris directus - tr.tbs.c. tractus tecto-bulbaris et spinalis cruciatus     

Responses of medullary neurons to moving visual stimuli in the common toad

The concept of coded 'command releasing systems' proposes that visually specialized descending tectal (and pretectal) neurons converge on motor pattern generating medullary circuits and release--in goal-specific combination--specific action patterns. Extracellular recordings from medullary neurons of the medial reticular formation of the awake immobilized toad in response to moving visual stimuli revealed the following main results. (i) Properties of medullary neurons were distinguished by location, shape, and size of visual receptive fields (ranging from relatively small to wide), by trigger features of various moving configural stimulus objects (including prey- and predator-selective properties), by tactile sensitivity, and by firing pattern characteristics (sluggish, tonic, warming-up, and cyclic). (ii) Visual receptive fields of medullary neurons and their responses to moving configural objects suggest converging inputs of tectal (and pretectal) descending neurons. (iii) In contrast to tectal monocular 'small-field' neurons, the excitatory visual receptive fields of comparable medullary neurons were larger, ellipsoidally shaped, mostly oriented horizontally, and not topographically mapped in an obvious fashion. Furthermore, configural feature discrimination was sharper. (iv) The observation of multiple properties in most medullary neurons (partly showing combined visual and cutaneous sensitivities) suggests integration of various inputs by these cells, and this is in principle consistent with the concept of command releasing systems. (v) There is evidence for reciprocal tectal/medullary excitatory pathways suitable for premotor warming-up. (vi) Cyclic bursting of many neurons, spontaneously or as a post-stimulus sustaining event, points to a medullary premotor/motor property.     

Parvalbumin-expressing interneurons linearly transform cortical responses to visual stimuli

The response of cortical neurons to a sensory stimulus is shaped by the network in which they are embedded. Here we establish a role of parvalbumin (PV)-expressing cells, a large class of inhibitory neurons that target the soma and perisomatic compartments of pyramidal cells, in controlling cortical responses. By bidirectionally manipulating PV cell activity in visual cortex we show that these neurons strongly modulate layer 2/3 pyramidal cell spiking responses to visual stimuli while only modestly affecting their tuning properties. PV cells' impact on pyramidal cells is captured by a linear transformation, both additive and multiplicative, with a threshold. These results indicate that PV cells are ideally suited to modulate cortical gain and establish a causal relationship between a select neuron type and specific computations performed by the cortex during sensory processing.     

老年猫视皮层细胞对刺激反应的对比敏感度下降伴随皮层内抑制作用减弱(英文)

对人类和动物的心理学研究证实,老年个体的视觉对比敏感度相对青年个体显著下降。为揭示其可能的神经机制,采用在体细胞外单细胞记录技术研究青、老年猫(Felis catus)初级视皮层(primary visual cortex,V1)细胞对不同视觉刺激对比度的调谐反应。结果显示,老年猫V1细胞对视觉刺激反应的平均对比敏感度比青年猫显著下降,这与灵长类报道的研究结果相一致,表明衰老影响视皮层细胞对视觉刺激反应的对比敏感度是灵长类和非灵长类哺乳动物中普遍存在的现象,并可能是介导老年性视觉对比敏感度下降的神经基础。另外,与青年猫相比,老年猫初级视皮层细胞对视觉刺激的反应性显著增强,信噪比下降,感受野显著增大,表明衰老导致的初级视皮层细胞对视觉刺激反应的对比敏感度下降伴随着皮层内抑制性作用减弱。     

Intracellular activity of morphologically identified neurons of the grass frog's optic tectum in response to moving configurational visual stimuli

Summary In the grass frogRana temporaria, various classes of tectal neurons were identified by means of intracellular recording and iontophoretic staining using potassium-citrate/Co³⁺-lysine-filled micropipettes, which have been defined previously by extracellular recording methods. Class T5(1) neurons had receptive fields (RF) of 33°±5° diameter. In response to a moving 8°×8° square (S), a 2°×16° worm-like (W), or a 16°×2° antiworm-like (A) moving stripe, these cells showed excitatory postsynaptic potentials (EPSPs) and spikes which were interrupted occasionally by small inhibitory postsynaptic potentials (IPSPs). The excitatory responses (R) were strongest towards the square (R_S) and less to the worm (R_W). For the antiworm (R_A) the responses were smallest or equal to the worm stimulus yielding the relationship R_S>R_WR_A. Some of these cells were identified as pear-shaped or large ganglionic neurons, whose somata were located in the tectal cell layer 8. The somata of other large ganglionic neurons were found in layer 7 and the somata of other pear-shaped neurons at the top of layer 6, both displaying T5(1) properties. Class T5(2) neurons (RF=34°±3°) responded with large EPSPs and spikes, often interrupted by small IPSPs, when their RF was traversed by the square stimulus. The excitatory activity was somewhat less to the worm stimulus, whereas no activity at all, or only IPSPs, were recorded in response to the antiworm-stimulus; thus yielding the relationship for the excitatory activity R_S>R_W>R_A 0. Such a cell was identified as pyramidal neuron; the soma was located at the top of layer 6, with the long axon travelling into layer 7 to the medulla oblongata. Class T5(3) neurons (RF=29°±6°) showing EPSPs and spikes according to the relationship R_S>R_A>R_W have been identified as large ganglionic neurons. Their somata were located in layer 8. Class T5(4) neurons (RF=24±7°) responded only to the square stimulus with EPSPs and spikes, sometimes interrupted by IPSPs and yielding the relationship R_S>R_AR_W0. The somata of these large ganglionic or pear-shaped neurons were located in layer 8. Class T1(1) neurons (RF=30°–40°) were most responsive to stimuli moving at a relatively long distance in the binocular visual field, and have been identified as pear-shaped neurons. Their somata were located in layer 6.Further neurons are described and morphologically identified which have not yet been classified by extracellular recording methods. For example,IPSP neurons (RF=20°–30°) responded (R) with IPSPs only according to the relationship R_S>R_A R_W. The somata of these pear-shaped neurons were located in layer 6.The properties of tectal cells in response to electrical stimulation of the optic tract and to brisk changes of diffuse illumination suggest certain neuronal connectivity patterns. The results support the idea ofintegrative functional units (assemblies) of connected cells which are involved in various perceptual processes, such as configurational prey selection expressed by T5(2) prey-selective neurons.Abbreviations A antiworm-like 16°×2° stripe stimulus with long axis perpendicular to the direction of movement - W wormlike 2°×16° stripe stimulus with long axis oriented parallel to the direction of movement - S square 8°×8° moving stimulus - ERF excitatory receptive field - IRF inhibitory receptive field - RF receptive field - EPSP excitatory postsynaptic potential - IPSP inhibitory postsynaptic potential     

The brightness components of the visual evoked potential to color stimuli in the rabbit

Two earliest components of visual evoked potentials (N85 and P130) which were related with substitution of stimuli for those identical in spectra but different in brightness were detected in rabbits. This finding suggests an analogy between the N85 and P139 in rabbits and N87 and P120 in humans.     

Intermodulation components of the visual evoked potential: Responses to lateral and superimposed stimuli

Nonlinear interactions in the human visual system were studied using visual evoked potentials (VEPs). In one experiment (superimposed condition), all segments of a dartboard pattern were contrast reversed in time by a sum of two sinusoidal signals. In a second experiment (lateral condition), segments in some regions of the dartboard pattern were contrast reversed by a single sinusoid of one frequency, while segments in other (contiguous) regions of the pattern were contrast reversed by a single sinusoid of another frequency. An identical set of ten frequency pairs was used in each experiment. The frequency pairs were chosen such that the difference between frequencies in each pair was 2 Hz. Amplitudes and phases of the sum and difference frequency components of the VEP (intermodulation terms) were retrieved by Fourier analysis and served as measures of nonlinear interactions. The use of input pairs with a fixed separation in frequency enabled the estimation of the temporal characteristics of the visual pathways prior to a second linear stage. The use of superimposed and lateral conditions revealed antagonistic contributions to the VEP, possibly reflecting direct-through excitatory and lateral inhibitory pathways, respectively.Supported by grants from the U.S. National Eye Institute, the Esther A. and Joseph Klingenstein Fund, and the Harry Frank Guggenheim Foundation     

Negative components of the direct cortical response

Dendritic (DPs) and slow negative potentials (SNPs) arising in response to direct electrical stimulation of the cortex in cats under deep Nembutal anesthesia were studied. Monosynaptic DPs reflect EPSPs of apical dendrites; they develop in response to impulses arriving from fibers in layer I. DPs are strengthened by application of eserine and by Ca⁺⁺, and weakened by the action of Mg⁺⁺, Br^–, and caffeine. Analysis of changes in DPs evoked by paired stimuli indicates that Ca⁺⁺, Mg⁺⁺, and Br^– influence the presynaptic elements of axo-dendritic synapses, while caffeine acts on their postsynaptic elements. DPs are abolished by application of GABA; strychnine does not affect them. From these and other facts it can be concluded that there are no inhibitory synapses on apical dendrites. Evidence of the participation of the neuroglia in SNP genesis is analyzed. SNPs are selectively depressed by x-rays, strengthened by Ca⁺⁺, and weakened by Mg⁺⁺. Against the background of SNPs, DPs are inhibited and the ratio between amplitudes of DPs evoked by paired stimuli is changed. It is concluded that during SNPs the dendrites and presynaptic terminals of axo-dendritic synapses are deploarized.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 2, No. 4, pp. 339–348, July–August, 1970.     

Ensemble cortical responses to rival visual stimuli: Effect of monocular transient

Binocular rivalry is a fascinating perceptual phenomenon that has been characterized extensively at the psychophysical level. However, the underlying neural mechanism remains poorly understood. In particular, the role of the early visual pathway remains controversial. In this study, we used voltage-sensitive dye imaging to measure the spatiotemporal activity patterns in cat area 18 evoked by dichoptic orthogonal grating stimuli. We found that after several seconds of monocular stimulation with an oriented grating, an orthogonal stimulus to the other eye evoked a reversal of the cortical response pattern, which may contribute to flash suppression in perception. Furthermore, after several seconds of rival binocular stimulation with unequal contrasts, transient increase in the contrast of the weak stimulus evoked a long-lasting cortical response. This transient-triggered response could contribute to the perceptual switch during binocular rivalry. Together, these results point to a significant contribution of early visual cortex to transient-triggered switch in perceptual dominance.     

Varying response of caudate neurons to visual stimuli in awake cats

Activity in 62 caudate nucleus neurons produced during presentation of visual stimuli was recorded during experiments on awake cats. Response of a sensory pattern, associated with a photic stimulus falling within a certain section of the visual field was observed in 52% of the neurons tested as against only 11% manifesting motor response related to eye movement guided towards a target. About a quarter of the cells responded to biologically significant stimuli, producing a nonspecific response, i.e., not specifically related to the nature of the visual stimuli presented. Several different response patterns could be recorded from a single unit. A hypothesis that more than one parallel pathway for afferent visual inferences on the caudate nucleus may exist is presented on the basis of findings from this research.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 21, No. 3, May–June, pp. 372–378, 1989.     

Postsynaptic excitation and in hibition in neurons of the turtle general cortex in response to moving stimuli

Responses of the general cortex to moving stimuli were studied in turtles. The evoked potential, the synaptic nature of its individual components, and the mechanisms of their generation were analyzed. The evoked potential had a negative-positive sequence. The negative part consisted of a slow negative wave on which fast negative complexes were superposed. These components reflected EPSPs of afferent nature generated on dendrites of the principal neurons. The first fast negative complex was followed by a rhythmic discharge superposed on the slow negative and positve waves. The negative waves of the rhythmic discharge were shown to reflect EPSPs and the positive waves IPSPs, probably generated on dendrites of cortical neurons. The rhythmic EPSP — IPSPs are evidently generated by a feedback mechanism, whereas the positive wave reflects dendritic IPSPs of the principal neurons.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 9, No. 3, pp. 249–256, May–June, 1977.