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PubMedDate not supplied

Relationship between the characteristics of visual short-term memory in monkeys and the spatial properties of images.

Experiments were performed on Rhesus macaques to study the relationship between delayed visual differentiation processes and stimulus properties. These investigations showed that the processes of short-term storage of visual information in monkeys has significant features associated with differences in stimulus properties. These consisted of different durations of storage and motor response times. Because of these differences, stimuli (15 pairs) could be grouped into compact clusters on the bases of similarity between their delayed differentiation characteristics. These experiments characterized the processes of short-term information storage during the differentiation of stimuli differing in terms of spatial relationships between elements, as compared with stimuli differing in terms of other attributes (shape, color, etc.); spatial information was stored for shorter periods of time and motor response times were longer. It is suggested that visual short-term memory involves a set of mechanisms operating on attributes of different types and which, along with signs and working programs associated with the visual system, stores spatial discriminatory signs, in which the major role is played by visual-vestibular interactions.

Animals↗
PubMed1988

Compression and lateral shift of mental coordinate systems in a line bisection task.

Subjects (N = 18) were required to imagine how far lines of three different lengths which were presented to them previously would extend to the left or to the right of a vertical mark. They were asked to indicate the midpoint of the imagined line length. The frequency of deviations to the left or to the right of the geometrical midpoint of the line which had to be visualized was dependent on the length of the line and on the direction towards which the subjects imagined the line to extend. Whereas a compression of imagined half space compared to geometric half space was observed both for the left and right side, imagined half space on the right side of the visual field was shifted in addition more towards the periphery. It is suggested that the latter result is related to properties of left hemisphere functioning which could explain the occurrence of a typical symptom of unilateral neglect after a right hemisphere lesion.

Adult↗
PubMed1994

The enhanced representation of surface texture consequent on the loss of sight.

The unitisation effect in probed feature-recall was exploited to reveal changes in the representation of objects consequent on the loss of sight. Blind and sighted adults were given verbal descriptions of simple objects and later recalled the colour and surface texture of each object. While the blind and sighted were equally capable of recalling an object's colour, the blind were more capable than the sighted at recalling its surface texture. The superior recall of surface texture by the blind emerged very gradually as an increasing percentage of their lifetime was spent without sight. It is concluded that features salient for the haptic sense are increasingly likely to be incorporated in the blind person's representation of objects.

Adolescent↗
PubMed1995

Refraction, aliasing, and the absence of motion reversals in peripheral vision.

Reversals in perceived direction of motion of a grating when its spatial frequency exceeds half that of the sampling mosaic provide a potential tool for estimating sampling frequency in peripheral retina. We used two-alternative forced-choice tasks to measure performance of three observers detecting or discriminating direction of motion of high contrast horizontal or vertical sinusoidal luminance gratings presented either 20 or 40 deg from the fovea along the horizontal meridian. A foveal target at a comfortable viewing distance aided fixation and accommodation. A Maxwellian view optometer with 3 mm artificial pupil was used to correct the refraction of the peripheral grating, which was presented in a circular patch, 1.8 deg in diameter, in a surround of similar colour and mean luminance (47.5 cd.m-2). The refractive correction at each eccentricity was measured by recording the aerial image of a point after a double pass through the eye. The highest frequency which can reliably be detected (7-14 c/deg at 20 deg, 5.5-7.5 c/deg at 40 deg) depends critically on refraction. Refraction differs by up to 5 D from the fovea to periphery, and by up to 6 D from horizontal to vertical. Direction discrimination performance shows no consistent reversals, and depends less on refraction. It falls to chance at frequencies as low as one-third of the highest that can be detected. Gratings which can be detected but whose direction of motion cannot be discriminated appear as irregular speckle patterns whose direction of motion varies from trial to trial.(ABSTRACT TRUNCATED AT 250 WORDS)

Discrimination, Psychological↗
PubMed2002

Behavioral evidence for working memory of sensory dimension in macaque monkeys.

For animals, which lack language codes, there might be limitations in the use of abstract concepts in guiding their behavior. We trained two macaque monkeys in a computerized version of Wisconsin Card Sorting Task (WCST) with two dimensions (shape and color) to test their capability for memorizing, updating and using representation of sensory dimension. A sample had to be matched with one of three test items by either matching in color or shape. The monkeys had to find the relevant sensory dimension and its sudden changes by trial and error only based on reward and error signals. Both monkeys succeeded in more than ten shifts in the rules within a daily session. Several probe tests showed that the monkeys in fact used the dimension-based matching rules, because the rule shift was generalized from the experience of some samples to all of the others in the sample set, and because the rules were immediately applied to newly introduced samples. The frequent shifts can be overcome only with representation of the sensory dimension in working memory. These results, thus, suggest that nonhuman primates can store sensory dimension such as color and shape in working memory, dynamically update it based on the behavioral outcomes, and use it to guide behavior, despite their lack of apparent language.

Animals↗
PubMed2006

Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?

The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there is a trend to overconstancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer's task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, underconstancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe underconstancy, and beyond this age, with mild underconstancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly overconstancy) to underconstancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of underconstancy that occurs in larger distances, where adults presented lower levels of underconstancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception.

Adolescent↗
PubMed1992

Intertrial interval and sequential effects in magnitude scaling.

The intertrial interval (ITI) was varied within subjects in magnitude estimation and cross-modality matching experiments. Fits of a recently proposed time series regression model show that the influence of the previous stimulus intensity on the current response decreases when the ITI is increased. The results can be interpreted as showing that an assimilative or additive perceptual or memory effect decreases with an increase in ITI. Fits of an earlier model, on the other hand, suggest that the influence of the previous stimulus intensity increases with an increase in ITI, which is counter to expectations. The new regression model (a) provides a simple explanation for the counterintuitive results obtained with the earlier model, (b) shows that assimilation in perception or memory can appear as contrast, and (c) reduces to a simpler model for longer ITIs.

Adult↗