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PubMed1992

Motion reveals spatial visual defects.

The question of how we can be unaware of the deficit in our (monocular) visual field, equivalent in size to 76 full moons, is examined. A new method of investigating the response to moving images on and near the blind spot has been found. The image of a computer-generated line, which is made to lengthen with time and pass over the blind spot, is seen as shorter than that of a similar, parallel line which passes outside the blind spot. This perceived difference in length corresponds to the actual width of the blind spot. Our unawareness of blind spots and scotomata is often described as involving some form of 'filling in' process. The rapid variation in cortical receptive field size, recently found to occur in response to stabilized images, may provide a general filling-in mechanism for the removal from perception of otherwise-distracting, stabilizing image regions (such as the shadows of blood vessels and clinical scotomata).

Humans↗
PubMedDate not supplied

Hemispheric prevalence changes in partial epileptic patients on perceptual and attentional tasks.

In relation to the general issue of the long-term effects of epileptic activity on the higher nervous functions, monohemispheric epileptic patients--divided into "lesional" [i.e., with computed tomography (CT) scan-visible lesions] and "nonlesional" (i.e., with CT scan-nonvisible lesions)--were submitted to dichotic verbal and tonal tasks, dichoptic verbal and spatial tasks, and a visual tachistoscopic attentional task. The aim was to investigate whether the typical patterns of hemispheric prevalence, which were observed in normal subjects by using these tests, undergo significant changes in epileptic patients. The findings versus normal subjects seem to demonstrate that (a) in lesional epileptic patients, the prevalence of the hemisphere without macroscopic lesions is a constant rule, whether or not this hemisphere is prevalent in normal subjects; (b) in nonlesional epileptic patients, the patterns are the following: when the epileptic hemisphere is the one that is prevalent in normal subjects, its prevalence is enhanced, whichever the hemisphere; when the epileptic hemisphere is not the hemisphere prevalent in normal subjects, the left one attracts and maintains prevalence, whereas the right one reduces and variously interferes with contralateral prevalence. It is concluded that, with respect to the functions tested, the nature of the epileptic foci seems to influence markedly the interhemispheric prevalence pattern.

Adult↗
PubMed2005

The emergence of social cognition in three young chimpanzees.

We report a series of 10 studies on the social-cognitive abilities of three young chimpanzees. The studies were all ones previously conducted with human infants. The chimpanzees were 1-5 years of age, had been raised mostly by humans, and were tested mostly directly by a familiar human experimenter. First, in a longitudinal investigation with repeated measurements from a social-cognitive test battery, the three young chimpanzees were similar in many ways to human infants; the major difference was a total lack of attempts to share attention with others either in joint attentional interactions or through declarative gestures. Second, in imitation-based tests of the understanding of intentional action, the chimpanzees, like human infants, showed an understanding of failed attempts and accidents; but they did not pay attention to the behavioral style of the actor or the actor's reasons for choosing a particular behavioral means. Third, in tests of their understanding of visual perception, the chimpanzees followed the gaze direction of a human to an out-of-sight location behind a barrier and gestured more to a human who could see them than to one who could not; but they showed no understanding that perceivers can focus their attention on one thing, or one aspect of a thing, within their perceptual fields for a reason. Finally, in tests of joint intentions and joint attention, the chimpanzees showed no ability to either reverse roles with a partner in a collaborative interaction or to set up a joint attentional framework for understanding the communicative intentions behind a pointing gesture. Taken together, these findings support the idea that the early ontogeny of human social cognition comprises two distinct trajectories, each with its own evolutionary history: one for understanding the basics of goal-directed action and perception, common to all apes, and another for sharing psychological states with others in collaborative acts involving joint intentions and attention, unique to the human species.

Affect↗
PubMed1978

Some notes on the use of family sculpture in therapy.

Therapists learning to use family sculpture as a tool often find difficulty in exploiting the technique to its fullest. This article, designed to encourage therapists to take the risks involved in using a technique new to them, describes how the author and his cotherapists used sculpture in three cases in different ways. In each case, the author explains how the therapists made the choices involved in directing the therapeutic process. He suggests that even when a sculpture itself seems to have failed to produce useful information, it can elicit from clients signals that will indicate opportunities for effective use of other techniques and that a sculpture, once used, can be restaged to reinforce client behavior change.

Art↗
PubMed1982

Clinical and experimental evidence that the pattern electroretinogram (PERG) is generated in more proximal retinal layers than the focal electroretinogram (FERG).

A TV monitor was used to evoke either a pattern ERG to a contrast-reversing checkerboard (PERG), or a focal ERG to alternate increases and decreases of luminance of the blank screen within a bright surround (FERG). Both responses are small (approx 2 microV) and fast (approx 50 msec to peak) and are similar in several other properties. However, they differ in timing and respond differently to changes in contrast. Each frame of a TV picture evokes a "raster ERG," even though the screen is blank. The response is focal and specific to a small central strip of the screen. It is simpler to record than the FERG, where the whole screen is flashing. Because the FERG summation area is about 4 deg, small squares (checks) reversing in contrast produce little luminance response. In 5 of 7 cases where the PERG is unilaterally reduced, the FERGs or raster responses were not affected. Thus clinical evidence also suggests that the PERG may be a separate phenomenon to the FERG and produced at a different site. Toxic, traumatic, congenital, and degenerative diseases of the optic nerve reduce the PERG. The comparison is most easily made in unilateral disease. Ten weeks after an optic nerve insult, the PERG becomes reduced in the affected eye as if retrograde degeneration was occurring. In 27 amblyopes of various types, the PERG was reduced in 23 where orthoptic treatment had failed. In 4 patients responding to treatment, PERGs of the amblyopic eye were as large as, or larger than, those of the fellow eye. The loss is greater with smaller checks. Retinal changes do occur after age 4 but so slowly that responses in heavily occluded eyes are not reduced. An additional level in the visual pathway is thus accessible to evoked potential investigation.

Amblyopia↗
PubMed2001

Absolute pitch, early musical instruction, and spatial abilities.

The results of the study show that AP possessors performed better in the Hidden Figure Test than did NMs and musicians with RP and that age at which music instruction is initiated affects performance in specific spatial tasks. Individuals who begin extensive musical instruction at a very early age may have an advantage when completing selected spatial tests over those with no formal musical training. However, characteristics other than starting age of musical instruction are associated with AP and seem to affect musicians' performance in the Hidden Figure Test. The differences found between the performance of AP possessors and RP possessors in this nonmusical task suggest further research.

Aging↗
PubMed1981

Relationships among cognitive complexity, sex, and spatial task performance in college students.

This study examined the relationship between object differentiation (spatial ability) and social differentiation (cognitive complexity). Prior research had demonstrated a link between field independence and cognitive complexity, and between field independence and spatial ability. This raises the question whether some unitary cognitive style is involved in both spatial ability and cognitive complexity. The present study used a spatial task (a variation of Piaget & Inhelder's water level task) and several measures of cognitive complexity (the Barron Complexity scale, Intolerance of Ambiguity scale, and measures of self-differentiation and differentiation of other persons) to test the prediction that complexity will be positively related to performance on the water level task. On the basis of earlier findings, we also predicted that males would outperform females on the water level task. Thirty-eight male and 98 female undergraduates completed the water level task and the complexity measures. Results confirmed the predictions, except that the relationship between cognitive complexity and performance was different for males than for females. For males, the correlations between scores on the water level task and the several measures of complexity were considerably higher than for females. Such results suggest that for males spatial task performance can be related to a general construct such as cognitive style; for females, this does not appear to be the case.

Adolescent↗
PubMed1984

Reproduction of complex two-dimensional movements as a function of mode of presentation.

The experiment reported here examined the kinaesthetic reproduction of two-dimensional patterns from three different modes of presentation: kinaesthetic only, visual only and visual plus kinaesthetic. The patterns were open and consisted of three linear segments of different lengths. All reproductions tended to underestimate pattern size. Subjects who had received visual experience of the pattern with or without simultaneous kinaesthetic experience produced significantly greater underestimates than subjects who had not seen the patterns. This is discussed in terms of the dominance of vision over kinaesthesis, and differences in size perception in the two modalities. Least distortion of the pattern shape was found in the reproduction of subjects who had received both kinaesthetic and visual experience of the criterion.

Female↗
PubMed1970

The representation of three-dimensional visual space in the cat's striate cortex.

1. Binocularly driven single units were recorded in the cat's striate cortex. For each neurone the two monocular receptive fields were stimulated simultaneously in order to assess the optimal positioning of the image in both eyes to give the best binocular response.2. The electrode was driven perpendicular to the surface of the brain to explore cortical columns, all the cells of which are known to have the same preferred target orientation.3. All orientation columns were found to fit into one of two classes according to their binocular organization.4. In a constant depth column the receptive fields of binocular neurones cover a small retinal area and they are laid out in almost identical arrays in the two eyes. Consequently, the horizontal disparity is practically the same for all the units. The depth column as a whole is viewing a thin sheet of visual space, a few degrees wide, floating at some distance from the cat. There may be about 0.6 degrees disparity difference between neighbouring depth columns.5. In a constant direction column the binocular units' fields are all super-imposed on the retina contralateral to the hemisphere containing the column. In the ipsilateral eye they are more scattered horizontally. Therefore the horizontal disparity varies enormously from cell to cell and the column as a whole is viewing a cylinder of visual space directed towards the contralateral eye. Neighbouring direction columns may vary by about 4 degrees in their oculocentric visual direction.6. This columnar arrangement is probably important for space perception in the cat. Activity in only one depth and one direction column would specify the orientation and the three-dimensional locus of an object in space.7. The two types of column may be involved in the control of disjunctive and conjugate eye movements.

Animals↗
PubMed1976

Reversal of the behavioural effects of monocular deprivation in the kitten.

1. Eighteen kittens were monocularly deprived of vision until the age of 5, 6 or 7 weeks. Their eyes were then reverse-sutured, and they were allowed to survive for 3-63 days, before physiological recording from area 17. 2. At the time the reverse-suture was performed, and immediately before the recording session, each kitten was tested separately in the two eyes to elicit five simple behavioural responses: optokinetic nystagmus, visual startle reaction, visually-guided paw placing, visual following and negotiation of a "visual cliff". 3. Following the opening of their initially deprived eye, all kittens appeared behaviourally blind when forced to use that eye; their performance through the initially open eye was then perfect on all tests. After the period of reversed lid-suture, however, their performance when using the initially deprived eye had improved, while that through the initially open eye deteriorated. This complementary improvement and deterioration was most rapid in kittens reverse-sutured at the age of 5 weeks, and less rapid when reverse-suturing was delayed until the age of 6 or 7 weeks. 4. Most of the kittens showed gross abnormalities of interocular alignment, and exhibited marked exotropia or esotropia. 5. The results of these tests were well correlated with the changes seen in cortical ocular dominance in the same animals.

Age Factors↗
PubMed2003

Effects of target height and width on 2D pointing movement duration and kinematics.

This study examined the impact of target geometry on the trajectories of rapid pointing movements. Participants performed a graphic point-to-point task using a pen on a digitizer tablet with targets and real time trajectories displayed on a computer screen. Circular- and elliptical-shaped targets were used in order to systematically vary the accuracy constraints along two dimensions. Consistent with Fitts Law, movement time increased as target difficulty increased. Analysis of movement kinematics revealed different patterns for targets constrained by height (H) and width (W). When W was the constraining factor, movements of greater precision were characterized by a lower peak velocity and a longer deceleration phase, with trajectories that were aimed relatively farther away from the center of the target and were more variable across trials. This indicates an emphasis on reactive, sensory-based control. When H was the constraining factor, however, movements of greater precision were characterized by a longer acceleration phase, a lower peak velocity, and a longer deceleration phase. The initial trajectory was aimed closer to the center of the target, and the trajectory path across trials was more constrained. This suggests a greater reliance on both predictive and reactive control.

Acceleration↗
PubMed1975

Moving visual phantoms: a new contour completion effect.

Moving contours surrounding an empty region make phantoms appear to move through the empty region. The phantoms are contours, dimmer than the inducing contours but of the same pattern, color, speed, and direction of movement. The phantoms originate in the brain and may be related to completion effects most often seen with visual pathology.

Fixation, Ocular↗
PubMed1972

Visual spatial illusions: a general explanation.

Representation at the visual receptors of such properties of the object as its size, shape, orientation, and movement undergo considerable variation as the distance, bearing, posture, and motion of the observer, relative to the object, changes. However, despite these gross and frequent deformations of the image, perceived properties remain extraordinarily stable. Such constancy has obvious biological utility; the observer perceives his world according to its fixed physicalfeatures rather than in terms of its variable sensory representation. Constancy of apparent size, shape, orientation, and movement is dependent on information for the distance, bearing, lateral tilt, and movement of the observer, respectively. Thus, as the retinal image shrinks with distance, constancy of apparent size is maintained by five classes of distance, stimuli that operate singly or in various combinations. Likewise, visual orientation and visual stimuli for the orientation of the observer, and movement constancy on visual and nonvisual stimuli for the movement of the observer. Illusion occur when stimuli that normally preserve constancy are operative but with the image of the object not varied. Thus if retinal disparity, convergence-accommodation, projected stimuli, or other distance stimuli are varied with the image not varied, illusions of size occur. Those rsluting from variation of projected stimuli are the. well-known geometrical size illusions and include the Mü llerLyer group. In essentially the same manner, independent manipulation of stimuli for the orientation and the motion of the observer, with the orientation and the motion of the image at the retina not varied, gives rise to illusory orientations and movements of the object. Limited attempts to explain size illusions in terms of the projected stimuli that preserve perceptual constancy are by no means new; Thiéry (51) proposed such a view in the later part of the last century, and in recent times there has been a spate of such proposals including the " misapplied constancy hypothesis" advanced by Gregory (2). However, Gregory's theory is confined largely to geometrical size illusions and invoks only distance scaling given by a limited number of projected stimuli. Furthermore, the Müller-Lyer illusion is seen by him to be a consequence of distance scaling resulting from the converging arrows. There is no recognition of the range of such effects with various attached elements, as shown in Fig3, and no attention is accorded the recently established difference between the illusions with inward and outward-directed elements. The theory of spatial illusions outlined here distinguishes between classes of illusory effect and, in linking each to its particular class of spatial constancy, offers a general and testable explanation. Failure to recognize classes of illusion(and perceptual constancy), such as those of size, orientation, and movement, can be regarded as among the major deficiencies of recent attempts (2, 44) to explain illusory effects. I do not claim that this explanation, which I call the general constancy theory, satisfactorily encómpasses all known illusions, but merely that it is more comprehensive than alternative explantions I conclude that any stimulus which serves to maintain perceptual constancy of a property of an object as the visual representation of that property varies will, when independently manipulated with the retinal image not varied, produce an illusion. This general principle predictS the conditions under which illusory effects will occur and has wide explanatory application.

Age Factors↗