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PubMed1996

The temporal lobe is a target of output from the basal ganglia.

The basal ganglia are known to receive inputs from widespread regions of the cerebral cortex, such as the frontal, parietal, and temporal lobes. Of these cortical areas, only the frontal lobe is thought to be the target of basal ganglia output. One of the cortical regions that is a source of input to the basal ganglia is area TE, in inferotemporal cortex. This cortical area is thought to be critically involved in the recognition and discrimination of visual objects. Using retrograde transneuronal transport of herpes simplex virus type 1, we have found that one of the output nuclei of the basal ganglia, the substantia nigra pars reticulata, projects via the thalamus to TE. Thus, TE is not only a source of input to the basal ganglia, but also is a target of basal ganglia output. This result implies that the output of the basal ganglia influences higher order aspects of visual processing. In addition, we propose that dysfunction of the basal ganglia loop with TE leads to alterations in visual perception, including visual hallucinations.

Animals↗
PubMed1993

Basic mechanisms of constructional apraxia in unilateral brain-damaged patients: role of visuo-perceptual and executive disorders.

The basic mechanisms of constructional apraxia (CA) are still a matter of debate. In this study we assessed the possible relationships between CA and performance on tasks assessing visual perception, low-level motor skill, manipulo-spatial ability, and general intellective efficiency in samples of healthy subjects, right-brain-damaged (RBD) and left-brain-damaged (LBD) patients. Multiple regression analyses, performed separately for the three groups, demonstrated that efficiency in perceiving the model as a whole is the factor mainly related to drawing performance of normal subjects. In the RBD group, instead, a disorder of the manipulo-spatial ability seems to play the most important role in producing CA. As for the LBD group, the most relevant finding is that patients drawing with the left hand are significantly more impaired than patients using the right hand and than control subjects. These results are discussed in relation to various hypotheses so far advanced to account for basic mechanisms of CA in unilateral brain-damaged patients.

Aged↗
PubMed2006

Do rats use shape to solve "shape discriminations"?

Visual discrimination tasks are increasingly used to explore the neurobiology of vision in rodents, but it remains unclear how the animals solve these tasks: Do they process shapes holistically, or by using low-level features such as luminance and angle acuity? In the present study we found that when discriminating triangles from squares, rats did not use shape but instead relied on local luminance differences in the lower hemifield. A second experiment prevented this strategy by using stimuli-squares and rectangles-that varied in size and location, and for which the only constant predictor of reward was aspect ratio (ratio of height to width: a simple descriptor of "shape"). Rats eventually learned to use aspect ratio but only when no other discriminand was available, and performance remained very poor even at asymptote. These results suggest that although rats can process both dimensions simultaneously, they do not naturally solve shape discrimination tasks this way. This may reflect either a failure to visually process global shape information or a failure to discover shape as the discriminative stimulus in a simultaneous discrimination. Either way, our results suggest that simultaneous shape discrimination is not a good task for studies of visual perception in rodents.

Animals↗
PubMed1982

Visual, kinaesthetic and cross-modal judgements of length by normal and clumsy children.

The ability of normal and clumsy children to match the length of lines within and between the modalities of vision and kinesthesis was studied. The clumsy children showed perceptual impairments, as indicated by their poor performance on the visual, kinaesthetic and cross-modal judgements of length and also by their low scores on spatial subtests of the WISC. Variations in motor skill correlated with performance on the visual perceptual measures, but not with performance on the kinaesthetic or cross-modal tasks. The idea that clumsiness may be caused by an impairment of visual perception is discussed, together with some alternative interpretations of this pattern of results.

Agnosia↗
PubMed1986

Peripheral vision and the aetiology of child pedestrian accidents.

Three experiments examined whether age and sex differences in pedestrian accidents might be partly attributable to differences in the visual perception of peripheral stimuli. Primary schoolchildren and adults responded individually to the presentation of lights at retinal eccentricities of 2 degrees, 20 degrees and 40 degrees. Experiments 1 and 2 measured reaction times and Expt 3 measured subjects' expectations of foveal and peripheral events. There were no age or sex differences in expectations. Lights were detected fastest in the 20-40 degrees range. Movement times were not variable across eccentricities. As expected, adults' and 11-year-olds' detections were faster than eight- and six-year-olds'. A case is made for more problem-analytic and multi-theoretical research in the area of the child pedestrian accidents.

Accidents, Traffic↗
PubMed1962

The visual space sense.

At the conclusion of this discussion it is important to keep in mind the influences of all the complex processes involved in visual spatial localization, among which stereopsis is only one. The various factors and cues for this spatial localization interact with, complement, reinforce, and perhaps even inhibit one another, depending upon the varying visual surroundings of the moment and upon the physiologic perfection of the visual apparatus. In one's daily work probably no single factor or group of factors dominates at all times. "Any one who knows how pliable our spatial visual perceptions are under the influence of various conditions of observation and under the influence of past experience, taken into account consciously or unconsciously, should not be surprised at the multiplicity of results of observations on different objects and with different observers" (see 18).

Cues↗
PubMed1997

Visual discrimination and motor reproduction of movement by individuals with mental retardation.

Visual discrimination and motor reproduction tasks involving computer-simulated arm movements were administered to 12 adults with mental retardation and a gender-matched control group to examine whether inadequacies in visual perception account for the poorer motor performance of individuals with mental retardation. In the discrimination phase subjects judged whether simulated arm movements were either of greater or lesser extent or shorter or longer in duration, respectively, than those of a standard display. In the reproduction phase accuracy in reproducing the movement in the standard display was measured. Results indicate that error in discriminating extent and duration was significantly greater for the individuals with mental retardation, who were also less accurate and more variable in matching the extent and duration of the standard displays. These outcomes implicate both perceptual and motor-reproduction inadequacies in skill acquisition for these individuals.

Adult↗
PubMed1990

Visuospatial orientation in Parkinson's disease.

Visuospatial functioning in patients with Parkinson's disease was investigated using neuropsychological measures of basic visual perception, complex perceptual discrimination, and spatial orientation. Three subgroups of patients were described: (a) those with broadly impaired visuospatial abilities, (b) those with generally intact abilities, and (c) those whose performance on a task of spatial orientation was lower than their performance on a task of complex perceptual discrimination. These subgroup differences were also concordant with three other variables: age, duration of disease, and degree of dementia. It is suggested that decreases in spatial orientation functioning in Parkinson's disease may reflect the speed of progression of this disease.

Adult↗
PubMed2005

Using afterimages for orientation and color to explore mechanisms of visual filling-in.

Simulations of Grossberg's FACADE model of visual perception have previously been used to explain afterimage percepts produced by viewing a sequence of orthogonally oriented gratings. Additional simulations of the model are now used to predict new afterimage percepts. One simulation emphasizes that the afterimage percepts are the result of orientation afterresponses and color afterresponses that interact at a filling-in stage. We report experimental data that agree with FACADE's prediction. A second simulation emphasizes the properties of the model's filling-in stage and predicts a situation where the afterimage percept should not appear. We report experimental data indicating that this model prediction is incorrect. We argue that the model is unable to account for this result unless the filling-in stage mechanisms are different from a diffusive-type process. We propose an alternative mechanism, and simulations demonstrate the system's ability to account for the afterimage data.

Afterimage↗
PubMed1986

Crossing the midline as a function of distance from midline.

This study examined the effect of differential block placement on the frequency of midline crossing during the Space Visualization test (SV) of the Southern California Sensory Integration Tests. The SV test was administered at distances of 0.75, 3.00, and 6.00 inches to a group of 71 normal right-handed boys (ages 5 and 7 years) to obtain the Space Visualization Contralateral Use score (SVCU) and the Space Visualization Contralateral Use Percentage score (SVCU percent). Space Visualization (SV) adjusted scores were also obtained to examine the effect of differential block placement on visual perception scores. The analyses for the SVCU and SVCU percent scores showed that age and distance were significant. Analysis of variance of the SV adjusted standard score indicated that trial, but not distance or age, was significant. There was a significant age-by-trial interaction. The need for a standard protocol for block placement during the administration of the SV test was shown. Future research needs were identified.

Age Factors↗
PubMed2003

[A case of agnosia for streets without visual memory disturbance].

A 70-year-old, right-handed man was admitted to our hospital for his sudden-onset topographical disorientation. He failed to find his way to familiar places, but he knew distance and direction to the places. Neurological examination revealed homonymous left-upper quadrantanopsia on Goldmann perimeter and hypoesthesia over the left side of his body. Magnetic resonance imaging showed an abnormal intensity area at the right medial temporo-occipital region, due to the infarct of the right posterior cerebral arterial territory. The neuropsychological examination revealed agnosia for streets, and prosopagnosia without any other disturbance of visual perception. Both visual and topographical memories were intact. It is suggested that, in this case, the agnosia for streets was caused by impairment of recognizing familiar streets and houses or disconnection between their recognition and memory.

Aged↗
PubMed1989

[Neuropsychological differentiation of specific dyslexia in children].

An approach to dyslexia is substantiated in terms of a multilevel organization of written speech (gnostico-praxical and symbolical levels). Two dyslexia forms were differentiated in a neuropsychological investigation of 32 children. First had a selective written speech disorder based upon a visual perception deficit. Second type of dyslexia was caused by a distortion of acoustic symbols of the language which was evident not only in writing and reading disorders but also in impaired notional thinking (language acoustic coding disorder). This approach provides a basis for an adequate pedagogical correction of dyslexia.

Child↗
PubMed1997

Visual motion perception after brain damage: I. Deficits in global motion perception.

We report on the test results of a group of 32 mostly unilaterally brain-damaged patients examined for global visual motion perception. Three of these patients had severely impaired visual motion perception in their contralateral visual half-field, a deficit remarkably similar to the perceptual defects found in V5-lesioned monkeys. Two of these three patients had a right-hemisphere lesion; the remaining one had a left-hemisphere lesion. We conclude that both hemispheres of the human brain contain an area, functionally equivalent to V5, which subserves visual motion perception in the contralateral visual half-field. Lesion analysis revealed that this area is located in the posterior medial temporal gyrus.

Adult↗
PubMed2003

Voluntary head movement and allocentric perception of space.

Although visual input is egocentric, at least some visual perceptions and representations are allocentric, that is, independent of the observer's vantage point or motion. Three experiments investigated the visual perception of three-dimensional object motion during voluntary and involuntary motion in human subjects. The results show that the motor command contributes to the objective perception of space: Observers are more likely to apply, consciously and unconsciously, spatial criteria relative to an allocentric frame of reference when they are executing voluntary head movements than while they are undergoing similar involuntary displacements (which lead to a more egocentric bias). Furthermore, details of the motor command are crucial to spatial vision, as allocentric bias decreases or disappears when self-motion and motor command do not match.

Awareness↗
PubMedDate not supplied

Lateralization of visual-spatial perception in man in conditions of verbal reinforcement.

Studies were carried out on the effects of positive and negative verbal reinforcement on the mental ability of normal subjects and patients with chronic alcoholism to construct standard geometrical shapes from two fragments presented tachystoscopically. Negative verbal reinforcement in healthy subjects produced reductions in the latent period and increases in the amplitude of evoked N200-P300 potentials, particularly in the right parietal lobe and the vertex. These changes were not observed in patients, and patients lesser ability to carry out visual-spatial tasks could be explained by the general reduction in evoked brain potentials and the disappearance of interhemisphere functional asymmetry, which plays an important role in visual-perceptive activity in man.

Adult↗
PubMed1979

A test battery to assess intrasensory and intersensory development of young children.

The purpose of the study was to develop a battery of tests for use in evaluation of intra- and intersensory development of young children. A battery of 15 tests (4 visual, 4 auditory, 4 tactile-kinesthetic, and 3 intersensory) was administered to 109 normally developing 6- and 8-year-old and 32 slowly developing or learning disabled children. Interdependence of test items within each intrasensory and the intersensory category was determined; intercorrelations ranged from .00 to .78. Reliability estimates were also determined. Face validity was claimed for each item. The effects of age or developmental level on test performance were established. Based upon the interdependence of the tests, reliability estimates, and the capacity of the tests to discriminate among groups classified according to age or developmental level, a battery of 10 intra- and intersensory tests was proposed. The battery has 3 tests of visual perception-visual memory, dynamic depth perception, and size discrimination; 3 tests of auditory perception-auditory discrimination, auditory memory of related syllables, and auditory sequential memory of numbers; 2 tests of tactile-kinesthetic perception-tactile integration and movement awareness; and 2 tests of intersensory integration-auditory-tactile intergration and auditory-visual integration.

Age Factors↗