Directional filter characteristics of optic nerve fibers in California ground squirrel (Spermophilus beecheyi)

1984 ◽  
Vol 52 (6) ◽  
pp. 1200-1212 ◽  
Author(s):  
M. E. McCourt ◽  
G. H. Jacobs
Keyword(s):  
Optic Nerve ◽  
Ground Squirrel ◽  
Receptive Fields ◽  
Spatial Summation ◽  
Nerve Fibers ◽  
Field Size ◽  
Image Motion ◽  
Spermophilus Beecheyi ◽  
California Ground Squirrel ◽  
Preferred Direction

Directional units in the optic nerve of the California ground squirrel (Spermophilus beecheyi) were studied with respect to their response to diffuse light, preferred directions of motion, tuning for preferred direction, the relationship between spatial and directional tuning characteristics, and receptive-field size and areal summating properties. Directional units in the ground squirrel optic nerve are of the “on-off” type. No purely on or off units were encountered in a sample of 356 directionally selective fibers. The distribution of preferred directions of image motion for 356 units was significantly anisotropic; greater than 50% of the directional units prefer motion in the direction of the superior-nasal visual quadrant. Mean directional bandwidth, measured at half-amplitude response, for 39 units was 88.5 degrees. The distribution of directional bandwidths suggests that two subpopulations of directional units may exist a broadly tuned (106.4 degrees bandwidth) group preferring image motion in the superior-nasal direction, and a narrowly tuned group (59.9 degrees bandwidth) with a uniform distribution of preferred direction. Tuning for direction of motion and for spatial frequency were significantly positively correlated in a sample of 35 directional units. Area-vs.-response measures for directional units show that they possess excitatory discharge centers with a concentric antagonistic surround, plus a larger suppressive surround activated specifically by moving luminance contours, which may be asymmetric. Critical activation areas for directional units, as measured along orthogonal orientations, were highly positively correlated. This suggests that these receptive fields possess the property of linear spatial summation, not of luminance flux, but of areas of moving luminance contours.

Behavioral and electrophysiological sensitivity to temporally modulated visual stimuli in the ground squirrel

1991 ◽  
Vol 6 (6) ◽  
pp. 593-606 ◽  
Author(s):  
Michael A. Crognale ◽  
Gerald H. Jacobs
Keyword(s):  
Optic Nerve ◽  
Spectral Sensitivity ◽  
Temporal Resolution ◽  
Ground Squirrel ◽  
Temporal Frequency ◽  
Nerve Fibers ◽  
Spermophilus Beecheyi ◽  
Unit Recording ◽  
California Ground Squirrel ◽  
Spectral Sensitivity Function

AbstractBehavioral and electrophysiological methods were used to measure sensitivity to flickering lights in a dichromatic species, the California ground squirrel (Spermophilus beecheyi). Discrimination tests were used to determine spectral sensitivity at stimulus frequencies from 5–50 Hz and increment threshold spectral sensitivity. The contributions of retinal mechanisms to these capacities were assessed by recording the responses of optic nerve fibers to temporally modulated monochromatic lights. In the ground squirrel, as in the human, the shape of the spectral-sensitivity function depends on the temporal frequency of the stimulus. Results from single-unit recording show that all of the classes of optic nerve fibers in the ground squirrel are highly phase-locked to the stimulus for modulation rates as high as 50 Hz. Neither the responses of photoreceptors nor any class of optic nerve fiber can singly account for the behavioral results. The electrophysiological results are also counter to models which propose that temporally dependent changes in the spectral sensitivity of spectrally opponent fibers account for the behavior. The temporal resolution of the optic nerve fibers exceeds that of the behaving animal suggesting that retinal mechanisms do not limit behavioral temporal resolution.

Spatial filter characteristics of optic nerve fibers in California ground squirrel (Spermophilus beecheyi)

1984 ◽  
Vol 52 (6) ◽  
pp. 1181-1199 ◽  
Author(s):  
M. E. McCourt ◽  
G. H. Jacobs
Keyword(s):  
Optic Nerve ◽  
Spatial Frequency ◽  
Contrast Sensitivity ◽  
Nerve Fibers ◽  
Spermophilus Beecheyi ◽  
Fourier Amplitude ◽  
Amplitude Response ◽  
California Ground Squirrel ◽  
Spatial Frequencies ◽  
Resolution Limits

The spatial response properties of single optic nerve fibers in the California ground squirrel (Spermophilus beecheyi) were investigated. Results are reported for each of several response classes. Resolution limits determined for 165 spectrally nonopponent optic nerve fibers ranged from 0.1 to 4.2 cycles/degree (c/d), with a mean resolution limit of 1.49 c/d. Directionally selective units possessed the highest resolution limits (mean = 1.91 c/d.) Sustained and transient units possessed mean resolution limits of 1.44 and 1.09 c/d, respectively. The correlation between response and sensitivity measures of spatial tuning was examined for 29 units. Optimal spatial frequency and spatial frequency bandwidth estimates derived from the two measures were highly correlated. As measured from response functions, optimal spatial frequencies of 97 spectrally nonopponent units ranged from 0.1 to 2.2 c/d (mean = 0.44 c/d). Directionally selective units possessed the highest optimal spatial frequencies (mean = 0.60 c/d). Mean optimal spatial frequencies for sustained and transient units were 0.32 and 0.27 c/d, respectively. Mean half-amplitude response bandwidth for 96 optic nerve fibers was 2.80 octaves. Directionally selective units were narrowly tuned, possessing a mean half-amplitude bandwidth of 1.99 octaves. Sustained and transient units had mean half-amplitude response bandwidths of 3.56 and 2.80 octaves, respectively. The response bandwidths of directionally selective optic nerve fibers were highly negatively correlated with optimal spatial frequency; no significant correlation between these measures existed for sustained or transient units. Peak contrast sensitivity in 88 optic nerve fibers ranged from 3.0 to 55.0. Mean contrast sensitivity was 16.7 and did not differ between fiber response classes. Peak contrast sensitivity was not correlated with optimal spatial frequency. Poststimulus time histograms of unit responses to sinusoidal luminance modulation revealed that some sustained units modulate their discharge rates around spontaneous levels and show predominant Fourier amplitude at the fundamental frequency. Transient units possess low levels of spontaneous discharge and respond abruptly to the passage of grating half-cycles, resulting in a characteristically dispersed spectrum of Fourier amplitude. Directionally selective units respond to sinusoidal luminance gratings with an elevation of maintained firing rate and possess moderate Fourier amplitudes corresponding to the fundamental and second harmonic frequencies.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Visual Response Properties and Visuotopic Representation in the Newborn Monkey Superior Colliculus

1997 ◽  
Vol 78 (5) ◽  
pp. 2732-2741 ◽  
Author(s):  
M. T. Wallace ◽  
J. G. McHaffie ◽  
B. E. Stein
Keyword(s):  
Superior Colliculus ◽  
Ocular Dominance ◽  
Receptive Fields ◽  
Spatial Summation ◽  
Visual Space ◽  
Field Size ◽  
Visual Response ◽  
Response Latencies ◽  
Developmental Models ◽  
Response Properties

Wallace M. T., J. G. McHaffie, and B. E. Stein. Visual response properties and visuotopic representation in the newborn monkey superior colliculus. J. Neurophysiol. 78: 2732–2741, 1997. Visually responsive neurons were recorded in the superior colliculus (SC) of the newborn rhesus monkey. The receptive fields of these neurons were larger than those in the adult, but already were organized into a well-ordered map of visual space that was very much like that seen in mature animals. This included a marked expansion of the representation of the central 10° of the visual field and a systematic foveal to peripheral increase in receptive field size. Although newborn SC neurons had longer response latencies than did their adult counterparts, they responded vigorously to visual stimuli and exhibited many visual response properties that are characteristic of the adult. These included surround inhibition, within-field spatial summation, within-field spatial inhibition, binocularity, and an adult-like ocular dominance distribution. As in the adult, SC neurons in the newborn preferred a moving visual stimulus and had adult-like selectivities for stimulus speed. The developmentally advanced state of the functional circuitry of the newborn monkey SC contrasts with the comparative immaturity of neurons in its visual cortex. It also contrasts with observations on the state of maturation of the newborn SC in other developmental models (e.g., cat). The observation that extensive visual experience is not necessary for the development of many adult-like SC response properties in the monkey SC may help explain the substantial visual capabilities shown by primates soon after birth.

Are the preferred directions of neurons in cat extrastriate cortex related to optic flow?

1995 ◽  
Vol 12 (5) ◽  
pp. 887-894 ◽  
Author(s):  
Helen Sherk ◽  
Jong-Nam Kim ◽  
Kathleen Mulligan
Keyword(s):  
Receptive Field ◽  
Optic Flow ◽  
Visual Analysis ◽  
Receptive Fields ◽  
Image Motion ◽  
Extrastriate Cortex ◽  
Clear Correlation ◽  
Lower Visual Field ◽  
Preferred Direction ◽  
Flow Directions

AbstractIt has been proposed that one area of extrastriate cortex in the cat, the lateral suprasylvian area (LS), plays an important role in visual analysis during locomotion (Rauschecker et al., 1987). Cells in LS reportedly tend to prefer directions along a trajectory originating at the center of gaze, and passing outward through the receptive-field center. Such directions coincide with the directions of image motion in an optic flow field, the pattern seen by locomoting observers when they fixate the point towards which they are heading (Gibson, 1950). We re-examined this issue for cells in LS with receptive fields in the lower visual field. Cells recorded posterior to Horsley-Clarke A2 showed a clear correlation between preferred direction and receptive-field location, but not that predicted: preferred directions were generally orthogonal to “optic flow” directions. Since these cells were all located posterior to those in studies showing a bias for “optic flow” directions, we hypothesized that there are two cell populations within LS, an anterior population that tends to prefer radial-outward directions, and a posterior population that tends to prefer directions orthogonal to radial. Data from earlier mapping experiments (Sherk & Mulligan, 1993) supported this idea.

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