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PubMed2004

Use your words!

"Use your words!" is a phrase admonishing preschoolers to divert their action-proneness to thought and language. Freud's injunction against acting out had a similar aim, placing control over drives in the domain of "inner language." The twenty-first-century psychoanalyst continues to employ models that depend on mentalization viewed from two angles-neural inhibition and social discourse. Psychoanalysts bolster their position by borrowing from the basic scientific work in each area. The recent focus on enactments, intersubjectivity, and social constructivism is reconsidered from an historical vantage point, as is the work that seeks to reconcile recent findings in neuroimaging and cognitive neuroscience. Freud's vision included a holistic hope that a comprehensive science of human beings might be achieved by understanding derived from biological inquiry and the artifacts of social and cultural narratives. The author's experience in both domains is recounted, and a new reconciliation of disparate approaches is offered in linguistic complementarity.

Cognition↗

PubMed1982

Orientation disparity and plasticity of cortical cells in kittens following surgical rotation of the eye.

We have studied the effect of surgically induced monocular rotation of the eye on cells in visual area 17 of normal kittens (N = 420 cells) and of kittens monocularly deprived (N = 296 cells) at early (1-1.5 months) or late (3 months) ages. The receptive fields of cortical neurons in monocularly deprived kittens of the early operated group were abnormal in shape, a condition which is reflected by the high proportions of cells missing orientation (46.9%) and direction (47.7%) specificity when driven through the rotated eye. In addition, many cells (46%) were visually inactive in these kittens. The proportions of the above cell groups were less pronounced in the operated kittens with binocular vision and in all late operated kittens, indicating a specific effect of the rotation itself. In the early operated kittens with binocular vision, the rotation resulted in 35.9% binocular cells in the hemisphere contralateral and 40.0% in the hemisphere ipsilateral to the rotated eye. The results for the monocularly deprived early operated kittens were 42.8% and 21.5% respectively. Thus, the rotation was effective in limiting the influence of the deprivation to only the contralateral hemisphere. The distribution of the cells in accordance with their receptive field orientations following correction for the surgical rotation shows a considerable disturbance to orientation specificity, as reflected by the wide range of angular disparities found for the binocular cells. While for three kittens (28 cells) a tendency toward the zero line was found, for four kittens (28 cells) we could not prove, it indicating that a compensation for the interocular difference surgically induced is not seen.

Adaptation, Physiological↗

PubMed2004

"Acoustical vision" of below threshold stimuli: interaction among spatially converging audiovisual inputs.

Crossmodal spatial integration between auditory and visual stimuli is a common phenomenon in space perception. The principles underlying such integration have been outlined by neurophysiological and behavioral studies in animals; this study investigated whether the integrative effects observed in animals also apply to humans. In this experiment we systematically varied the spatial disparity (0 degrees, 16 degrees, and 32 degrees) and the temporal interval (0, 100, 200, 300, 400, and 500 ms) between the visual and the auditory stimuli. Normal subjects were required to detect visual stimuli presented below threshold either in unimodal visual conditions or in crossmodal audiovisual conditions. Signal detection measures were used. An enhancement of the perceptual sensitivity (d') for luminance detection was found when the audiovisual stimuli followed a simple spatial and temporal rule, governing multisensory integration at the neuronal level.

Acoustic Stimulation↗

PubMed2000

Motion detection from photopic to low scotopic luminance levels.

In this study we quantify the influence of adaptation luminance on the threshold for direction-detection in coherently moving random-pixel arrays (RPAs). Square RPAs of a constant rms-contrast (35%) were used and we determined their 'critical' or threshold-width Wc. Mean retinal illuminances were varied in 13 steps of 0.5 log unit from the low photopic range (screen luminance 0.3 cd/m2) down to 6 log units attenuation, which appeared to be about the absolute threshold of vision under the conditions of our experiment. Moving RPAs were presented at six retinal locations (0, 3, 6, 12, 24 and 48 degrees) from the fovea to the far periphery in the temporal visual field of the right eye of three experienced observers (the authors). In order to ensure an honest comparison between these very disparate conditions, the spatial dimensions (including speed) were scaled according to the acuity, as measured separately for each of the viewing-conditions and observers. Acuity scaling proves to equate the performance for all eccentricities and luminance levels rather well. The fovea is special, but only in the sense that the absolute threshold for light detection is reahed earlier than in peripheral regions. In all other respects foveal results follow the pattern found for peripheral locations. Two different regimes can be discerned in the data, one for high and one for low speeds. In the low speed range Wc is almost constant, regardless of luminance level or eccentricity. The critical 'crossing-time' Tc for any pixel starting at one end of the stimulus and leaving at the opposite end is therefore inversely proportional to velocity in the low-speed range (time-velocity reciprocity). At medium-to-high speeds Wc increases linearly with velocity, so Tc is constant. This constant (minimum) value of Tc differs between subjects, but in all subjects it increases somewhat with decreasing luminance level, even for our acuity-scaled stimuli. The different behaviour for low and high speeds [reported before for photopic viewing conditions by van de Grind, W. A., van Doorn, A. J., & Koenderink, J. J. (1983. Journal of the Optical Society of America, 73, 1674-1683) and van de Grind, W. A., Koenderink, J. J., & van Doorn A. J. (1986. Vision Research, 26, 797-810)] proves to hold from photopic to low scotopic luminance ranges, provided the stimuli are scaled according to acuity. We draw the general conclusion that movement detection is a very robust process that tolerates extremely low retinal illuminance levels. Moreover, the visual system appears to use the same processing principles in combination with an acuity-scaled architecture under all adaptation states and at all eccentricities.

Adaptation, Ocular↗

PubMed1975

Amblyopia screening with random-dot stereograms.

A stereoscopic test was developed for the visual screening of preschool children. The TNO test for stereoscopic vision utilized the same principle as the Julesz random-dot stereogram, and provided a simple and unequivocal test criterion understood even by young children. The results of a comprative evaluation of the TNO and Titmus stereoscopic tests proved the TNO test to be the more reliable of the two, particularly in the 2- to 4-year-old age range. Failure to pass this test at the 240 seconds of arc disparity level yielded an excellent screening criterion, as attested by the results of a validation experiment employing 81 patients (2 to 7 years old) with known visual health records. Furthermore, the screening results obtained from 129 preschool children (2 to 5 years old) tested in the classroom by a nonprofessional examiner, suggest that, under these more realistic conditions, the TNO test yields at least 60% less overreferrals than the Titmus test.

Amblyopia↗

PubMed1978

Changes in retinal correspondence following surgery for intermittent exotropia.

An intermittent exotrope of 54delta had harmonious anomalous correspondence when squinting and normal correspondence when bifoveally fixating. Measures of the angle of deviation (H) and angle of anomaly (A) were made at the first postoperative dressing 6 hr after surgery (H = 8--14delta esotropia, A = 0--54delta exo) and at several times over a 2.5-mo period during which a second operation was performed. The final result was 3delta of exophoria with normal correspondence when fusing and harmonious anomalous correspondence (A = 3delta exo) when fusion was disrupted. The change in angle of anomaly created by the surgery cannot be explained by changes in fusional vergence. Halldén's "sensory-fusion" mechanism, which is based on diplopia resulting from stimulation of disparate retinal points, is more useful in explaining the obtained results.

Adult↗

PubMed2001

Responses of macaque V1 neurons to binocular orientation differences.

Interocular differences in orientation occur during binocular viewing of a surface slanted in depth. These orientation disparities could be exploited by the visual system to provide information about surface slant, but gradients of positional disparity provide an equally effective means to the same end. We examined the encoding of orientation disparities in V1 neurons that were recorded from two awake fixating monkeys. Monocular orientation selectivity was measured separately in each eye. Although the preferred monocular orientation in the left and right eyes was highly correlated (r = 0.98), 19 of 61 cells showed a significant interocular difference in preferred orientation (IDPO). By itself, an IDPO does not imply a specific binocular selectivity for orientation differences. We therefore examined the response to 25 binocular combinations of orientations by pairing each of five orientations in one eye with five in the other. Forty-four of 64 neurons showed responses that reflected the monocular orientation tuning selectivity; the preferred orientation disparity changed when the monocular orientation was changed in either eye. The remaining third (20 of 64) responded to a consistent orientation disparity in a way that was not simply predictable from monocular orientation selectivity. However, nearly all of these neurons were selective for positional disparity, and several characteristics of the responses suggest that the apparent selectivity for orientation disparities was just a consequence of the positional disparity sensitivity. Neither the data presented here nor previous data from the cat (Blakemore et al., 1972; Nelson et al., 1977) support the idea that a population of neurons early in the visual system has a separate encoding scheme for orientation disparities.

Action Potentials↗

PubMed1995

Comparison of fixation disparity curve variables measured with the Sheedy Disparometer and the Wesson Fixation Disparity Card.

BACKGROUND: Previous studies suggest differences in the fixation disparity curves obtained with the Sheedy Disparometer and the Wesson Fixation Disparity Card, the two most commonly used methods for measuring fixation disparity. In one study the investigators proposed that the differences do not exist for subgroups divided by phoria. The purpose of this paper is to try to clarify this issue by use of two large sets of data. METHODS: Dissociated phorias were measured by the von Graefe method. Fixation disparity curves were plotted using the Disparometer and the Wesson card. RESULTS: Type I fixation disparity curves were most common with the Wesson card. Type II curves were found more often with the Disparometer than with the Wesson card. The x-intercepts were shifted in the base-in (BI) direction with the Wesson card compared to the Disparometer. The y-intercepts were shifted in the exo direction with the Wesson card compared to the Disparometer. The differences were statistically significant regardless of whether the dissociated phoria was exo or eso. The slope of the fixation disparity curve was steeper with the Wesson card than with the Disparometer. The difference was statistically significant for exophores but not for esophores. The differences between results obtained with the two instruments are not consistent from one subject to another as shown by high standard deviations of the differences. CONCLUSIONS: The fixation disparity curves measured with these two instruments are different. Fixation disparity parameters obtained from one of these instruments cannot be used with normative findings from the other.

Evaluation Studies as Topic↗

PubMedDate not supplied

Borish Vectographic Nearpoint Card II contour and random dot stereoacuity in children.

PURPOSE: To determine the completion rate and normative values for the Borish Vectographic Nearpoint Card II (Stereo Optical Co, Inc, Chicago, III) contour and random dot stereoacuity tests in children. METHODS: Children had to pass a modified clinical screening technique to be included in the study to eliminate vision problems that could potentially affect stereoacuity. One hundred forty-six children in second through fourth grade (mean age: 8.27 years) from a middle class, suburban, primarily white, elementary school near Columbus, Ohio participated in this investigation. Random dot and contour stereoacuity were measured using the Borish Vectographic Nearpoint Card II. RESULTS: All of the children were able to identify which circle had disparity on the 1280 seconds of arc contour stereoacuity target, but six children were unable to perceive the "E" on the 1280 seconds of arc random dot target. The median stereoacuity was 80 seconds of arc on both the contour and random dot stereotests in this population. CONCLUSION: A high completion rate was found on both the contour and random dot stereoacuity tests. Median stereoacuities were higher on the Borish Vectographic Nearpoint Card II in this population than those previously reported with the Randot contour stereoacuity test and Randot Preschool random dot stereoacuity test in children.

Child↗

PubMed1997

The TINS Lecture. The parietal association cortex in depth perception and visual control of hand action.

Recent neurophysiological studies in alert monkeys have revealed that the parietal association cortex plays a crucial role in depth perception and visually guided hand movement. The following five classes of parietal neurons covering various aspects of these functions have been identified: (1) depth-selective visual-fixation (VF) neurons of the inferior parietal lobule (IPL), representing egocentric distance; (2) depth-movement sensitive (DMS) neurons of V5A and the ventral intraparietal (VIP) area representing direction of linear movement in 3-D space; (3) depth-rotation-sensitive (RS) neurons of V5A and the posterior parietal (PP) area representing direction of rotary movement in space; (4) visually responsive manipulation-related neurons (visual-dominant or visual-and-motor type) of the anterior intraparietal (AIP) area, representing 3-D shape or orientation (or both) of objects for manipulation; and (5) axis-orientation-selective (AOS) and surface-orientation-selective (SOS) neurons in the caudal intraparietal sulcus (cIPS) sensitive to binocular disparity and representing the 3-D orientation of the longitudinal axes and flat surfaces, respectively. Some AOS and SOS neurons are selective in both orientation and shape. Thus the dorsal visual pathway is divided into at least two subsystems, V5A, PP and VIP areas for motion vision and V6, LIP and cIPS areas for coding position and 3-D features. The cIPS sends the signals of 3-D features of objects to the AIP area, which is reciprocally connected to the ventral premotor (F5) area and plays an essential role in matching hand orientation and shaping with 3-D objects for manipulation.

Animals↗

PubMed2005

Synchronizing to real events: subjective audiovisual alignment scales with perceived auditory depth and speed of sound.

Because of the slow speed of sound relative to light, acoustic and visual signals from a distant event often will be received asynchronously. Here, using acoustic signals with a robust cue to sound source distance, we show that judgments of perceived temporal alignment with a visual marker depend on the depth simulated in the acoustic signal. For distant sounds, a large delay of sound relative to vision is required for the signals to be perceived as temporally aligned. For nearer sources, the time lag corresponding to audiovisual alignment is smaller and scales at rate approximating the speed of sound. Thus, when robust cues to auditory distance are present, the brain can synchronize disparate audiovisual signals to external events despite considerable differences in time of arrival at the perceiver. This ability is functionally important as it allows auditory and visual signals to be synchronized to the external event that caused them.

Auditory Perception↗

PubMed2003

Topography of photoreceptors and retinal ganglion cells in the spotted hyena (Crocuta crocuta).

The spatial distributions of photoreceptors and retinal ganglion cells were examined in the spotted hyena (Crocuta crocuta). Two populations of cones were identified by immunocytochemical labeling. The hyena retina contains approximately 2.3 million middle- to long-wavelength sensitive (M/L) cones that reach peak densities of about 7,500/mm(2) in the vicinity of the optic nerve head. A sparser population of short-wavelength sensitive (S) cones, totaling about 0.3 million, was also detected. There is a striking disparity in the spatial distributions of the two cone types with S cones achieving peak density in a region located well below the optic nerve head. The differences in the spatial distributions of the two cone types have implications both for visual sensitivity and for color vision. Hyena rods outnumber cones by about 100:1 with rod density falling off modestly along a central-peripheral gradient. Ganglion cells were identified in retinal wholemounts by Nissl staining patterns. Their distribution defines a prominent visual streak with highest spatial packing (approx. 4,200/mm(2)) in an area centralis that is located in the temporal retina. The total number of ganglion cells is estimated at about 260,000. Using standard assumptions the maximum spatial resolution of the spotted hyena is calculated to be about 8.4 cycles/degree, a value similar to estimates obtained for other terrestrial carnivores.

Animals↗

PubMed1998

A framework for considering the role of afference and efference in the control and perception of ocular position.

It has been well established that extra-retinal information is used in the perception of visual direction and distance. Furthermore, a number of studies have established that both efference copy and afferent discharge contribute to the extra-retinal signal. Despite this, no model currently exists to explain how the signals which arise through oculomotor control contribute to perception. This paper attempts to provide such a framework. The first part of the paper outlines the framework [the cyclopean equilibrium point (EP) model] and considers the binoculus or cyclopean eye from the perspective of a current account of motor control (the EP hypothesis). An existing model is used to describe how the nervous system could utilise available efference copy and afferent extra retinal signals when determining the direction and distance of cyclopean fixation. Although the cyclopean EP model is speculative, it allows for a parsimonious framework when considering the oculomotor contribution to perception. The model has the additional advantage of being consistent with current theories regarding the control and perception of limb movement. The second part of the paper shows that the model is biologically plausible, demonstrates the use of the proposed model in describing the central control of eye movements with regard to non-conjugate peripheral adaptation and reconciles seemingly disparate empirical findings.

Adaptation, Ocular↗

PubMed1996

Judgments by monkeys of apparent depth in dynamic random-dot stereograms.

Young macaques discriminated apparent depths of targets embedded in dynamic random dot stereograms; a test of stereopsis. In a 'same/different' paradigm, the discrimination took longer if the pair of stimuli appeared to be in same depth plane, than when they appeared to be located in a different depth plane. The decision time was an inverse function of the disparity difference. Apparent depth discrimination performance decreased as a function of disparity, with no differences in judgments regarding crossed or uncrossed disparities.

Animals↗

PubMed1993

Binocular enhancement of visual acuity.

Using a computerized test system, we compared binocular and monocular visual optotype acuity, varying both contrast and contrast disparity between the two eyes. When contrast was the same in the two eyes, binocular acuity was better than best monocular acuity by an average of 0.045 log minimum angle of resolution, or 11%. When contrast differed in the two eyes, binocular acuity in most but not all cases was still better than the monocular acuity of the eye that received the higher contrast. This binocular advantage became smaller but remained significant as contrast disparity became larger. These results are most simply explained by threshold contrast summation of high-spatial-frequency letter components.

Adult↗

PubMed1986

Pattern-reversal visual-evoked potentials in the diagnosis of amblyopia in children.

We assessed the potential clinical usefulness of pattern-reversal visual-evoked potentials in the diagnosis of amblyopia. Twenty-seven children with anisometropic amblyopia and four children without amblyopia participated. Estimates of visual acuity for each eye (Snellen visual acuity) were obtained by conventional psychometric methods. Visual-evoked potentials to reversing checks subtending 15 minutes of visual arc were also obtained. Visual-evoked potential testing and interpretation were done in a masked fashion. Ten of the 31 children were retested seven to 21 days after the first test to estimate reliability of the procedures. Of the 27 amblyopic children, 22 were correctly identified by the visual-evoked potential test alone. In four patients initial visual-evoked potential tests failed to identify the disparity in visual acuity between the eyes and retests in two of the four again had false-negative results. In one child initial visual-evoked potential testing incorrectly identified the amblyopic eye but repeat testing did identify it. Of the four children with symmetrically good vision, three were correctly identified as normal by the initial visual-evoked potential test. The other normal child was incorrectly identified by the visual-evoked potential test as having amblyopia.

Adolescent↗

PubMed2002

The effect of disparity change on binocular visual evoked potential parameters elicited by convergent dynamic random-dot stereogram stimuli in humans.

Binocular visual evoked potentials (VEP) were recorded from the left and right occipital cortices of right-handed subjects in response to six different levels of convergent disparity using the stimulus of dynamic random-dot stereogram (DRDS). The VEP obtained consisted of a negative (N1) and a positive peak (P1) within intervals of 200-400 ms and 400-600 ms, respectively. The latency of the N1 wave decreased with disparity and the amplitude of the same wave displayed a concave-down curve. The tuning-curve of N1 showed that the cortical focus, which produced this wave, was sensitive to mid-disparities. The fact that the tuning-curve of the right hemisphere was sharper than that of the left implied that the right hemisphere was more disparity-selective. In contrast to N1, the change of the latency and the amplitude of the P1 with disparity consisted of concave-up curves. The inverse correlation between the amplitudes of N1 and P1 with disparity made me think that the activation of the neuron population, which gave rise to N1 wave, changed the synchronization level of the cortical focus responsible for the P1 wave. If we keep in mind that the perception of depth is the result of the disparity detection, then we may conclude that N1 is related to disparity detection and P1 is the electrophysiological correlate of a depth percept.

Adult↗

PubMed1994

Some temporal aspects of stereoacuity.

Stereoacuity thresholds improve considerably with practice when measured using three vertical lines 15' apart horizontally and presented briefly. For experienced observers, these thresholds are relatively independent of exposure time for stimulus durations smaller than 100 msec. The thresholds are 2-3 times larger when the outer flanking lines are shown continuously than when they and the central target line are turned on and off simultaneously. When the target and flanking lines are shown sequentially, stereoacuity thresholds can be predicted from the number of times the configuration is presented. Changes in thresholds can be measured for intervals as small as 5 msec between successive presentation of the relative disparity configuration. The underlying mechanism is modeled well by a first order auto-regression process.

Depth Perception↗