Preferred Spatial Frequency Research Articles

Monocular and binocular response properties of cells in the striate-recipient zone of the cat's lateral posterior-pulvinar complex.

1. We have studied response properties of single cells in the striate-recipient zone of the cat's lateral posterior-pulvinar (LP-P) complex. This zone is in the lateral section of the lateral posterior nucleus (LP1). Our purpose was to determine basic response characteristics of these cells and to investigate the possibility that the LP-P complex is a center of integration that is dominated by input from visual cortex. 2. The majority (72%) of cells in the striate-recipient zone respond to drifting sinusoidal gratings with unmodulated discharge. 3. Cells in the LP1 are selective to the orientation of gratings, and tuning functions have a mean bandwidth of 31 degrees. More than one-half of these units are direction-selective. The preferred orientation and the tuning widths for the two eyes are generally well matched. However, a few cells exhibited the interesting property of opposite preferred directions for the two eyes. Orientation tuning for a small group of cells was different for the mean discharge and first harmonic components, suggesting a convergence from different inputs to these cells. 4. Two-thirds of LP1 cells are tuned to low spatial frequencies (less than 0.5 c/deg). The tuning is broad with a mean bandwidth of 2.2 octaves. The remaining one-third of the units are low-pass because they show no attenuation of their responses to low spatial frequencies. Both eyes exhibit the same spatial frequency preference and the same spatial frequency tuning. There is a high correlation between spatial frequency and orientation selectivities. 5. All cells tested are tuned for temporal frequency with a sharp attenuation for low frequencies. The optimal values range between 4 and 8 Hz, and the mean bandwidth is 2.2 octaves. 6. Cells in LP1 are mostly binocular. When monocular, cells are almost always contralaterally driven. Dichoptic presentation of gratings reveals the presence of strong binocular interaction. In almost all cases, these interactions are phase specific. The cell's discharge is facilitated at particular phases and inhibited at phases 180 degrees away. These binocular interactions are orientation dependent. 7. Twenty-five percent of the cells with phase-specific binocular facilitation appear to be monocular when each eye is tested separately. For three cells, we observed a non-phase-specific inhibitory effect of the silent eye. 8. Our findings indicate that LP1 cells form a relatively homogeneous group, suggesting a high degree of integration of multiple cortical inputs.(ABSTRACT TRUNCATED AT 400 WORDS)

Spatial and temporal determinants of directionally selective velocity preference in cat striate cortex neurons

1. Direction-selective properties of neurons in cat striate cortex (area 17) were studied with flashed and continuously moving bar stimuli. Receptive fields were characterized by measurement of static and dynamic parameters, which were correlated with the velocity preference exhibited by the same cells. 2. Each neuron was found to be direction selective to a limited range of velocities. This behavior was characterized by measuring the optimal velocity (Vopt) to elicit responses in the preferred and null directions that were maximally distinct. 3. A bar stimulus flashed sequentially at two nearby locations in the receptive field also produced direction-selective behavior, which was characterized by an optimal displacement (Dopt) to drive maximally distinct responses in the preferred versus null directions. 4. The static spatial receptive field properties were quantified by measurement of the receptive field size (2 sigma) and the spatial subunit wavelength (lambda). The latter quantity was measured as twice the separation between adjacent ON and OFF regions in simple cells and as twice the optimal separation for lateral inhibition between two simultaneously flashed bars in complex cells. 5. Direction-selective velocity preference for continuously moving stimuli, Vopt, was found to be highly correlated with lambda and with the Dopt for 2-flash motion; Vopt was also correlated to a lesser degree with 2 sigma. These results suggest a fundamental linkage between spatial frequency preference, velocity preference, and spatial tuning to 2-flash motion. 6. The range of measured direction-selective velocity preference values (Vopt) spanned about a 100-fold range, whereas the corresponding values of Dopt or lambda spanned substantially smaller ranges. This discrepancy suggested that the dynamic range of velocity preference among cortical neurons might be determined jointly by the measured spatial properties and by a temporal property that covaries with the measured spatial properties. 7. Temporal properties of striate cortical neurons were assessed from responses to flashed stimuli having a prolonged duration ("step responses"). Neurons typically responded in the following manner: after some latency (L), a transient rise in spike frequency occurred, which then adapted to some sustained level. The adaptation dynamics (extent of sustained vs. transient behavior) were quantified by the first-order time constant (AT) of the adaptation decay, and by the ratio of initial transient rise to final sustained level [adaptation ratio (AR)].(ABSTRACT TRUNCATED AT 400 WORDS)

Reponse suppression by extending sine-wave gratings within the receptive fields of neurons in visual cortical area V3A of the macaque monkey

Even though there are many more cycles of the “optimal” grating extending across the receptive fields of cells in V3A than of cells in V1 and V2, the spatial frequency bandwidths in V3A are no narrower than in V1 or V2. Thus, the inputs to V3A cells are not combined in a phase coherent manner across the entire receptive field. Moreover, the defined receptive fields of cells in V3A are generally surrounded by suppressive regions which are, on average, much stronger than those found for neurons in V1 and V2. Even within the classical receptive field, most neurons in V3A respond far more vigorously to a limited patch of a few cycles of a grating at the preferred spatial frequency than to wider grating stimuli. This intra-receptive field suppression demonstrates a new level of response complexity, and suggests that V3A cells may antagonistically combine nonlinear mechanisms that themselves encode stimulus energy over a restricted region of space and spatial-frequency.

Spatial and temporal properties of neurons of the lateral suprasylvian cortex of the cat.

Neurons in the posteromedial lateral suprasylvian cortex (PMLS) of cats were recorded extracellularly to investigate their response to stimulation by bars and by sinusoidal gratings. Two general types of cells were identified: those that modulated in synchrony with the passage of drifting bars and gratings and those that responded with an unmodulated increase in discharge. Both types responded to contrast reversed gratings with a modulation of activity: the cells that modulated to drifting gratings modulated to the first harmonic of contrast reversed gratings (at appropriate spatial phase and frequency), whereas those that did not modulate to drifting gratings always modulated to the second harmonic of contrast reversed gratings. No cell had a clear null point. Nearly all cells were selective for spatial frequency. The preferred frequency ranged from 0.1 to 1 cycles per degree (cpd), and selectivity bandwidths (full width at half height) were around two octaves. Preferred spatial frequency was not correlated with receptive field size, but bandwidth and receptive field size were positively correlated. Preferred spatial frequency decreased with eccentricity, at about 0.05 octaves/deg. The response of all cells increased as a function of grating contrast up to a saturation level. The contrast threshold for response to a grating of optimal parameters was approximately 1% for most cells and the saturation contrast approximately 10%. The contrast gain was approximately 25 spikes/s per log unit of contrast. All cells were tuned for temporal frequency, preferring frequencies from approximately 3 to 10 Hz, with a selectivity bandwidth approximately 2 octaves. For some cells, the spatial selectivity did not depend on the temporal frequency and vice versa. Others were spatiotemporally coupled, with the preferred temporal frequency being lower at high than at low spatial frequencies, and the preferred spatial frequency lower at high than at low temporal frequencies. Previous results showing broad velocity tuning to a bar were replicated and found to be predictable from the combined spatial and temporal tuning of PMLS cells and the Fourier spectrum of a bar. Preferred temporal frequency steadily decreased with eccentricity, at 0.025 octaves/deg. The results for PMLS cells are compared with those of other visual areas. Acuity and spatial preference and selectivity bandwidth is comparable to all areas except area 17, where they are a factor of about two higher. Temporal selectivity in PMLS is as fine as observed in other areas. The possibility that PMLS cells may be involved with motion detection and detection of motion in depth is discussed.

Spatial and temporal frequency selectivity of neurones in visual cortical areas V1 and V2 of the macaque monkey.

The spatial and temporal frequency selectivity of 148 neurones in the striate cortex, V1, and of 122 neurones in the second visual cortical area, V2, of the macaque monkey were studied using sine-wave gratings of suprathreshold contrast drifting over the receptive field at the preferred orientation and direction. Neurones in V1 and V2 were selective for different but partially overlapping ranges of the spatial frequency spectrum. At retinal eccentricities of 2-5 deg from the fovea, the spatial frequency preferences for neurones ranged from 0.5 to 8.0 cycles/deg in V1 and from 0.2 to 2.1 cycles/deg in V2 and were on average almost 2 octaves lower in V2 than in V1. Spatial frequency full band widths in the two cortical areas were in the range 0.8-3.0 octaves, with a mean value of 1.8 octaves, in the parafoveal representation of both V1 and V2, and 1.4 and 1.6 octaves respectively in the foveal representation of V1 and V2. Most neurones in V1 and some in V2 responded well at temporal frequencies up to 5.6-8.0 Hz before their responses dropped off at still higher frequencies. In V1, 68% of the neurones exhibited low-pass temporal tuning characteristics and 32% were very broadly tuned, with a mean temporal frequency full band width of 2.9 octaves. However, in V2 only 30% of the neurones showed low-pass temporal selectivity and 70% of the cells had bandpass temporal characteristics, with a mean full band width of 2.1 octaves. In V2 the minimal overlap of bandpass tuning curves across the temporal frequency spectrum suggests that there are at least two distinct bandpass temporal frequency mechanisms as well as neurones with low-pass temporal frequency tuning at each spatial frequency. A matrix of spatial and temporal frequency combinations was employed as stimuli for neurones with bandpass temporal frequency selectivity in both V1 and V2. The resultant spatio-temporal surfaces provided evidence that a neurone's preference for spatial frequency is essentially independent of the test temporal frequency; however, in V2 there was some tendency for temporal frequency peaks to shift slightly towards lower frequencies when non-optimum values of spatial frequency either above or below the preferred value were tested. Neurones with pronounced directional selectivity were encountered over a wide range of spatial frequencies, although in both cortical areas there was a tendency for an increased incidence of directional selectivity among neurones which were selective for lower spatial frequencies and higher temporal frequencies.

Relationship between spatial-frequency and orientation tuning of striate-cortex cells.

If striate cells had the receptive-field (RF) shapes classically attributed to them, their preferred spatial frequencies would vary considerably with orientation. Other models of RF shape would predict a greater independence between orientation and spatial-frequency tuning. We have examined this by recording the responses of cat striate-cortex cells to a wide range of different spatial-frequency and orientation combinations. In almost all cells studied, peak orientation did not consistently vary with spatial frequency, but the majority of cells showed some change in peak spatial-frequency tuning with orientation. The amount of change in peak spatial frequency tended to be greater for cells that were narrowly tuned for orientation. However, cells narrowly (and also very broadly) tuned for spatial frequency tended to show considerable independence of spatial-frequency and orientation tuning, and in all but a few cells the degree of change was less than predicted by the classic RF model. Such cells were found to fire only to patterns whose local spatial spectra fell within a compact, restricted, roughly circular two-dimensional spatial-frequency region. We conclude that the two-dimensional RF shape of striate cells more closely approximates that predicted by a two-dimensional Gabor model or by a Gaussian-derivative model than it does the classic shape based on the output of geniculate cells with aligned RF's.

Spatial and temporal selectivity of the human motion detection system

Measurements were made of spatial frequency, orientation and temporal frequency selectivity of the visual motion system. The results suggest: (1) There exists in the motion system mechanisms selective for spatial frequency. The preferred spatial frequency varies considerably and extends down to at least 0.06 c/deg. (2) At all spatial frequencies (from 0.1 to 10 c/deg) there exist detectors selective for orientation which vary in (directed) orientation tuning to encompass 360°. (3) The bandwidth of both spatial frequency and orientation selectivity vary inversely with spatial frequency: the lower the spatial frequency, the broader the bandwidth. (4) There exist two classes of temporally tuned detectors, one lowpass (sustained) and one bandpass (transient), of preferred temporal frequency of 7–13 Hz (depending on spatial frequency).

Use of gabor elementary functions to probe receptive field substructure of posterior inferotemporal neurons in the owl monkey

The large receptive fields of inferotemporal neurons in the owl monkey were studied with visual stimuli whose luminance profiles were one-dimensional Gabor functions i.e. sinusoidal gratings within Gaussian envelopes. The members of one set of such patterns all had a full bandwidth at half-amplitude of 0.8 octaves, but different center frequencies and spatial extents. These spatially restricted stimuli were ideal for determining whether one or more than one spatial frequency band projected onto discrete subsections of the neuron's receptive field. The other set of Gabor stimuli comprised sine waves within Gaussian envelopes of constant size, but with different center frequencies and hence different bandwidths. These stimuli allowed assessment of the neuron's spatial frequency selectivity across the full breadth of its receptive field. Results suggest that only one orientation band and one spatial frequency band provide an input onto each inferotemporal neuron under our experimental conditions. The preferred spatial frequencies found (0.2–0.6 c/deg) were all in the very low spatial frequency range for this animal. Calculations show that about 3.5–7.0 full cycles of the optimal grating usually cover the full width of the receptive field, but the observed spatial frequency tuning is not nearly as sharp as that which would be predicted according to phase coherent linear summation. Moreover, at the preferred spatial frequency, the peak response to gratings in the constant aperture series was generally less than the response to the same preferred spatial frequency in the constant relative bandwidth series. These results suggest either incomplete phase coherent summation from contributing subgroups, non-linear processing, or both.

Correlation between the preferred orientation and spatial frequency of neurones in visual areas 17 and 18 of the cat.

1. In seventy-six penetrations through areas 17 and 18 of the cat, neurones were regularly sampled at intervals of 100 micrometers and preferred orientation, optimal spatial frequency and resolving power were determined for each neurone in response to drifting sinusoidal gratings. 2. As already shown for area 17, in tangential penetrations through area 18, whenever the preferred orientation rotates progressively from cell to cell, the optimal spatial frequency tends to remain constant. 3. A statistical analysis on 1574 cells in areas 17 and 18 showed that for pairs of cells separated 200-300 micrometers along a track the difference in preferred orientation delta alpha and the difference in optimal spatial frequency delta f are not randomly distributed: cell pairs with small delta alpha are most likely to have large delta f and vice versa. 4. These findings indicate that in areas 17 and 18 neurones with the same optimal frequency are aligned along a direction orthogonal to the orientation columns. 5. The optimal spatial frequency, resolving power and the velocity cut-off were averaged for cells from different penetrations located in the same cortical layer or sublayer of area 18: mean optimal spatial frequency and acuity are highest in layer IV and lowest in layers II and V, while the velocity cut-off is highest in layers II and V and lowest in layer IV. 6. Our data suggest that the layering of cells according to optimal spatial frequency is a more subtle subdivision than the six histological layers.

Spatial computation performed by simple and complex cells in the visual cortex of the cat

Simple and complex cells have been tested with drifting sine-wave and square-wave gratings. Despite the known differences in the response pattern of each cell type to drifting sine-wave gratings, the tuning curves for square-wave gratings for both cell types show a similar secondary response band peaking at one-third the preferred spatial frequency as determined from sine-wave studies. These results establish that both cell types respond predominantly to the third harmonic of square-wave gratings in this frequency range. At the simple cell stage, all the information required to specify the amplitude and phase for a channel at a given orientation, direction and spatial frequency can be conveyed by four cells for a given subsection of visual space. At the complex cell stage, the cell's mean firing rate appears to represent the amplitude of a local Fourier coefficient, but phase information is not conveyed in the action potential code.

Spatial contrast sensitivity of cells in the lateral geniculate nucleus of the rat.

1. The responses to visual stimuli of cells in the dorsal lateral geniculate nucleus of the rat were recorded with micro-electrodes. 2. Maps made with small spots of light showed that most units had concentrically organized receptive fields. Some units gave 'on-off' responses to spots flashed anywhere within the receptive field. These units were not directionally selective. 3. By the use of grating patterns as stimuli, units with concentrically organized receptive fields could be divided into groups that showed linear or non-linear spatial summation. Those unit showing linear spatial summation behaved like the 'X' cells of the cat, those showing non-linear summation like 'Y' cells. 4. 'On-off' units showed non-linear spatial summation of a kind that readily distinguished them from Y cells. 5. Measurements of spatial contrast sensitivity made with moving gratings showed, for both X and Y cells, peak sensitivities for spatial frequencies between 0.05 and 0.09 c/deg X and Y cells were not distinguished by their preferred spatial frequencies at any eccentricity.

Spatial and temporal contrast sensitivity of neurones in areas 17 and 18 of the cat's visual cortex.

1. We have examined the spatial and temporal tuning properties of 238 cortical neurones, recorded using conventional techniques from acutely prepared anaesthetized cats. We determined spatial and temporal frequency tuning curves using sinusoidal grating stimuli presented to each neurone's receptive field by a digital computer on a cathode ray tube. 2. We measured tuning curves either by determining response amplitude as a function of spatial or temporal frequency, or by measuring contrast sensitivity (the inverse of the contrast of the grating that just elicited a detectable response). The two measures give very similar tuning curves in all cases. 3. We recorded from 184 neurones in area 17; of these 156 had receptive fields within 5 degrees of the area centralis. The range of preferred spatial frequency for these neurones was 0.3--3 c/deg, and their spatial frequency tuning band widths varied from 0.7 to 3.2 octaves at half-amplitude. The most common band width was roughly 1.3 octaves. Simple and complex cells in area 17 did not differ in their distributions of preferred spatial frequency, although complex cells were, on average, slightly less selective for spatial frequency than simple cells. 4. We recorded from fifty-four neurones from area 18, and performed several experiments in which we recorded from corresponding portions of both area 17 and area 18 in the same electrode penetration. Neurones in area 18 preferred spatial frequencies that were, on average, one third as high as those preferred by area 17 neurones at the same retinal eccentricity. Thus the range of preferred spatial frequency in area eighteen cells having receptive fields within 5 deg of the area centralis was between less than 0.1 and 0.5 c/deg. The distributions of optimum spatial frequency in the two areas were practically non-overlapping at eccentricities as high as 15 deg, the greatest eccentricity we examined. Neurones in area 18 were about as selective for spatial frequency as were neurones in area 17. 5. We determined temporal frequency tuning characteristics for some neurones from each area, using gratings that moved steadily across the screen. Neurones from area 17 all responded well to low temporal frequencies, and less well to higher frequencies (in excess of, usually, 2 or 4 Hz). In contrast, neurones recorded from area 18 sometimes had similar tuning properties, but more commonly showed a pronounced reduction in response as the temporal frequency was moved either above or below some optimum value (usually 2--8 Hz). 6. We conclude from these results that areas 17 and 18 act in parallel to process different aspects of the visual information relayed from the retina via the lateral geniculate complex. Some or all of the differences between the areas may be attributable to the predominance of Y cell input to area 18 and the predominance of X cell input to area 17...

Spatial frequency rows in the striate visual cortex

We have recorded the unitary activity of the neurons of area 17 of the cat either in penetrations perpendicular to the surface of the cortex or parallel to it. We have examined the functional architecture of this cortical area with respect to the spatial frequency of the visual stimulus (sinusoidal gratings) at which each neuron is most sensitive. In penetrations perpendicular to the surface of the cortex (columns) the cells of the various layers or even of the same layer have the same preferred orientation but different preferred spatial frequencies. In penetrations parallel to the surface of the cortex the cells of the same layer or sublayer present a variety of preferred orientations, but maintain the same preferred spatial frequency and visual acuity over long microelectrode track distances.

Estimation of lipoproteins using capillary blood.

The superior colliculus (SC) receives direct input from the retina and integrates it with information about sound, touch, and state of the animal that is relayed from other parts of the brain to initiate specific behavioral outcomes. The superficial SC layers (sSC) contain cells that respond to visual stimuli, whereas the deep SC layers (dSC) contain cells that also respond to auditory and somatosensory stimuli. Here, we used a large-scale silicon probe recording system to examine the visual response properties of SC cells of head-fixed and alert male mice. We found cells with diverse response properties including: (1) orientation/direction-selective (OS/DS) cells with a firing rate that is suppressed by drifting sinusoidal gratings (negative OS/DS cells); (2) suppressed-by-contrast cells; (3) cells with complex-like spatial summation nonlinearity; and (4) cells with Y-like spatial summation nonlinearity. We also found specific response properties that are enriched in different depths of the SC. The sSC is enriched with cells with small RFs, high evoked firing rates (FRs), and sustained temporal responses, whereas the dSC is enriched with the negative OS/DS cells and with cells with large RFs, low evoked FRs, and transient temporal responses. Locomotion modulates the activity of the SC cells both additively and multiplicatively and changes the preferred spatial frequency of some SC cells. These results provide the first description of the negative OS/DS cells and demonstrate that the SC segregates cells with different response properties and that the behavioral state of a mouse affects SC activity. <b>SIGNIFICANCE STATEMENT</b> The superior colliculus (SC) receives visual input from the retina in its superficial layers (sSC) and induces eye/head-orientating movements and innate defensive responses in its deeper layers (dSC). Despite their importance, very little is known about the visual response properties of dSC neurons. Using high-density electrode recordings and novel model-based analysis, we found several novel visual response properties of the SC cells, including encoding of a cell9s preferred orientation or direction by suppression of the firing rate. The sSC and the dSC are enriched with cells with different visual response properties. Locomotion modulates the cells in the SC. These findings contribute to our understanding of how the SC processes visual inputs, a critical step in comprehending visually guided behaviors.

A relationship between the detection of size, rate, orientation and direction in the human visual system

Differential increment thresholds for stationary gratings of variable spatial frequency and for moving patterns of variable velocity following adaptation to either of two velocities (2.5 and 6.5 deg/sec) or to either of two spatial frequencies (1.5 and 4.5 c/deg), respectively, indicate that the human visual system contains units of analysis which respond selectively to stimulus size and velocity. A distinction between two types of units, speed and velocity (i.e. speed and direction) analyzers, was established. Under conditions of systematically varied background illumination levels, correspondingly systematic changes in the size velocity preference of the hypothesized analyzers occurred, suggesting that the unit impulse response i.e. the response of a unit to a pulsed stimulus presentation, determines their size-velocity preference. The preferred velocity, ν, and spatial frequency (size), f 6, were shown to be relatable by the formula f sνi = 1, where i is the interval between the onsets of the primary and secondary excitatory discharges of the unit impulse response.