Brain areas sensitive to coherent visual motion

Detection of coherent motion versus noise is widely used as a measure of global visual-motion processing. To localise the human brain mechanisms involved in this performance, functional magnetic resonance imaging (fMRI) was used to compare brain activation during viewing of coherently moving random dots with that during viewing spatially and temporally comparable dynamic noise. Rates of reversal of coherent motion and coherent-motion velocities (5 versus 20 deg s-1) were also compared. Differences in local activation between conditions were analysed by statistical parametric mapping. Greater activation by coherent motion compared to noise was found in V5 and putative V3A, but not in V1. In addition there were foci of activation on the occipital ventral surface, the intraparietal sulcus, and superior temporal sulcus. Thus, coherent-motion information has distinctive effects in a number of extrastriate visual brain areas. The rate of motion reversal showed only weak effects in motion-sensitive areas. V1 was better activated by noise than by coherent motion, possibly reflecting activation of neurons with a wider range of motion selectivities. This activation was at a more anterior location in the comparison of noise with the faster velocity, suggesting that 20 deg s-1 is beyond the velocity range of the V1 representation of central visual field. These results support the use of motion-coherence tests for extrastriate as opposed to V1 function. However, sensitivity to motion coherence is not confined to V5, and may extend beyond the classically defined dorsal stream.     

Infants perceive human point-light displays as solid forms

While five-month-old infants show orientation-specific sensitivity to changes in the motion and occlusion patterns of human point-light displays, it is not known whether infants are capable of binding a human representation to these displays. Furthermore, it has been suggested that infants do not encode the same physical properties for humans and material objects. To explore these issues we tested whether infants would selectively apply the principle of solidity to upright human displays. In the first experiment infants aged six and nine months were repeatedly shown a human point-light display walking across a computer screen up to 10 times or until habituated. Next, they were repeatedly shown the walking display passing behind an in-depth representation of a table, and finally they were shown the human display appearing to pass through the table top in violation of the solidity of the hidden human form. Both six- and nine-month-old infants showed significantly greater recovery of attention to this final phase. This suggests that infants are able to bind a solid vertical form to human motion. In two further control experiments we presented displays that contained similar patterns of motion but were not perceived by adults as human. Six- and nine-month-old infants did not show recovery of attention when a scrambled display or an inverted human display passed through the table. Thus, the binding of a solid human form to a display in only seems to occur for upright human motion. The paper considers the implications of these findings in relation to theories of infants' developing conceptions of objects, humans and animals.     

Book reviews

BODEN, MARGARET A. Artificial Intelligence and Natural Man. Hassocks : Harvester Press Limited, and New York: Basic Books Inc., 1977. Pp. ix+537. £613.50 hardback; £64.95 paperback. ISBN 0 85527 435 2.

ESTES, W. K. (Ed.). Handbook of Learning and Cognitive Processes. Vol. 6. Linguistics. Functions in Cognitive Theory. Hillsdale, N.J. : Erlbaum Associates. 1979. Pp. 331. £12.70. ISBN o 470 26311 3.

O'KEEFE, J. and NADEL, L. The Hippocampus as a Cognitive Map. London: Oxford University Press. 1978. Pp. 543. £25.00. ISBN 0 12 524150 X.

FITZSIMONS, J. T. The Physiology of Thirst and Sodium Appetite. Cambridge: Cambridge University Press. 1979. Pp. 572. £32.50. ISBN 0 521 22292 3.

MURRAY, F. B. and PIKULSKI, J. J. (Eds). The Acquisition of Reading. Baltimore: University Park Press. 1978. Pp. 178. £8.95. ISBN 0 8391 1281 5.

NEWTON, M. J., THOMAS, M. E. and RICHARDS, I. L. Readings in Dyslexia. Wisbech: Benrose Ltd. 1979. Pp. 203. £4.50. ISBN 09 0511 4124.

SENDERS, J. W., FISHER, D. F. and MONTY, R. A. (Eds). Eye Movements and Higher Psychological Processes. Hillsdale, N. J. : Erlbaum. 1978. Pp. 394. £19.95. ISBN 0 470 26489 6.

GRUBER, H. E. and VONECHE, J. J. (Eds). The Essential Piaget. London: Routledge & Kegan Paul. 1977. Pp. 880. £12.95. ISBN 07100 87780.

SIEGEL, L. S. and BRAINERD, C. J. (Eds). Alternatives to Piaget. New York: Academic Press. 1978. Pp. 262. £11.70. ISBN 12 641950 7.

BRANSFORD, J. D. Human Cognition: Learning, Understanding and Remembering. Belmont, California: Wadsworth. 1979. Pp. xii+300. £11.85. ISBN 0 534 00699 X.

VON FIEANDT, K. and MOUSTGAARD, I. K. The Perceptual World. London: Academic Press. 1977. Pp. 680. £32.00. ISBN 0 12 725050 6.

BURTON, A. and RADFORD, J. (Ed.). Thinking in Perspective: Critical Essays in the Study of Thought Processes. London: Methuen. 1978. Pp. xxii+232. £3.95. ISBN 0 416 85840 6.

MAYER, R. E. Thinking and Problem Solving: An Introduction to Human Cognition and Leavning. Glenview, Illinois: Scott, Foresman and Company. 1977. Pp. viii+214. £4.95. ISBN 0 673 15055 0.

BATES, E. Language and Context: The Acquisition of Pragmatics. New York: Academic Press. 1976. Pp. 375. £14.50. ISBN 0 12 081550 8.

MILGHAM, N. W., KRAMES, L. and ALLOWAY, T. M. Food Aversion Learning. New York: Plenum Press. 1977. Pp. 263. £27. ISBN 0 306 31040 6.

O'CONNOR, N. and HERMELIN, B. Seeing and Hearing and Space and Time. London: Academic. 1978. Pp. 157+viii. £6.80. ISBN 0 12 524150 X.     

Development of illusory-contour perception in infants

We investigated whether infants from 8-22 weeks of age were sensitive to the illusory contour created by aligned line terminators. Previous reports of illusory-contour detection in infants under 4 months old could be due to infants' preference for the presence of terminators rather than their configuration. We generated preferential-looking stimuli containing sinusoidal lines whose oscillating, abutting terminators give a strong illusory contour in adult perception. Our experiments demonstrated a preference in infants 8 weeks old and above for an oscillating illusory contour compared with a stimulus containing equal terminator density and movement. Control experiments excluded local line density, or attention to alignment in general, as the basis for this result. In the youngest age group (8-10 weeks) stimulus velocity appears to be critical in determining the visibility of illusory contours, which is consistent with other data on motion processing at this age. We conclude that, by 2 months of age, the infant's visual system contains the nonlinear mechanisms necessary to extract an illusory contour from aligned terminators.     

Real-time generation of random-element motion displays

Random-element motion patterns for visual research, in which a set of the elements are shifted uniformly on successive exposures, can be generated in real time on a CRT display, using a relatively low-cost, commercially available display processor (Sigma QVEC). The software achieves economy of time by not rewriting large amounts of the display file for each exposure. Instead it changes only the “chaining addresses” that determine the order in which strips of the display are arranged. Further features of the hardware and software are described.     

Visually guided step descent in children with Williams syndrome

Individuals with Williams syndrome (WS) have impairments in visuospatial tasks and in manual visuomotor control, consistent with parietal and cerebellar abnormalities. Here we examined whether individuals with WS also have difficulties in visually controlling whole-body movements. We investigated visual control of stepping down at a change of level in children with WS (5-16-year-olds), who descended a single step while their movement was kinematically recorded. On each trial step height was set unpredictably, so that visual information was necessary to perceive the step depth and position the legs appropriately before landing. Kinematic measures established that children with WS did not use visual information to slow the leg at an appropriate point during the step. This pattern contrasts with that observed in typically developing 3- and 4-year-old children, implying severe impairment in whole-body visuomotor control in WS. For children with WS, performance was not significantly predicted by low-level visual or balance problems, but improved significantly with verbal age. The results suggest some plasticity and development in WS whole-body control. These data clearly show that visuospatial and visuomotor deficits in WS extend to the locomotor domain. Taken together with evidence for parietal and cerebellar abnormalities in WS, these results also provide new evidence for the role of these circuits in the visual control of whole-body movement.     

The role of landmarks and boundaries in the development of spatial memory

It has been suggested that learning an object's location relative to (1) intramaze landmarks and (2) local boundaries is supported by parallel striatal and hippocampal systems, both of which rely upon input from a third system for orientation. However, little is known about the developmental trajectories of these systems' contributions to spatial learning. The present study tested 5- and 7-year-old children and adults on a water maze-like task in which all three types of cue were available. Participants had to remember the location of an object hidden in a circular bounded environment containing a moveable intramaze landmark and surrounded by distal cues. Children performed less accurately than adults, and showed a different pattern of error. While adults relied most on the stable cue provided by the boundary, children relied on both landmark and boundary cues similarly, suggesting a developmental increase in the weighting given to boundary cues. Further, adults were most accurate in coding angular information (dependent on distal cues), whereas children were most accurate in coding distance, suggesting a developing ability to use distal cues to orient. These results indicate that children as young as 5 years use boundary, intramaze landmark, and distal visual cues in parallel, but that the basic accuracy and relative weighting of these cues changes during subsequent development.     

Pre-attentive detection of a target defined by stereoscopic slant.

Does the visual system represent stereoscopic depth purely as a map of local disparities, or does it explicitly represent local relationships of disparity, such as disparity gradients? Experiments are reported in which visual search for a target containing the same disparity range as other elements in the display, but differing in the relationship of the disparities (stereo slant), was used to determine whether the target showed 'pop-out' like a unitary feature, or the serial search characteristic of feature conjunctions. Each stereo pair of elements was selected randomly from a range of outline parallelograms leaning to the right or to the left, so that the target could not be identified using any monocular shape cue. Response times for detection of the target (present on 50% of the trials) were independent of the number of elements in the display. This result was confirmed by varying element size and spacing, and by using oblique crosses rather than parallelograms as stimuli. It is concluded that stereoscopically defined slant, or disparity gradient, can be processed and compared in parallel across the display, and acts in this respect as an explicit unitary visual property. This contrasts with findings in analogous experiments on movement, which show that targets defined by divergence or deformation of optic flow can only be identified by serial search.     

Book reviews

SCHIFF, W. AND FOULKE, E. (Eds.). Tactual Perception: A Source Book. Cambridge: Cambridge University Press. 1982. Pp. 464. ISBN 0 521 24095 6. £25.00.

GILHOOLY, K. J. Thinking: Directed, Undirected and Creative. London: Academic Press. 1982. Pp. 178. ISBN 0 12283482 8. £5.50.

DEUTSCH, D. The Psychology of Music. New York: Academic Press, 1982. Pp. 542. $49.50. ISBN 0 12 2135601.

SHEPARD, R. N. and COOPER, L. A. Mental Irnuges and Their Transfomutions. Cambridge, Mass: MIT Press. 1982. Pp. 364. ISBN 0 262 19200 4. £17.50

WADE, N. The Art and Science of Visual Illusions. London: Routledge & Kegan Paul. 1982. Pp. 293. E1y. 95 ISBN 0 7100 0868 6.

REED, S.K. Cognition: Theory and Applications. Montery, Calif.; BrooksiCole Publishing Co. 1982. Pp. 394. $19.95 ISBN 0 8185 0462 5.

CAELLI, T. Visual Perception Theonl and Practice. Oxford: Pergamon Press. 1981Pp. 197. £8.50 (paper) ISBN 0 08 oz4419/0~4420.

A. M. UTTLEY. Infomation Transmission in the Nervous System. London: Academic Press. 1979.Pp. 111 £7.50 ISBN 0 12709750 3.

ANDERSON, J. R. (Ed.). Cognitive Skills and their-Acquisition. Hillsdale, New Jersey: Erlbaum. 1981. Pp. 386. 00.00. ISBN 0 89859 093 0.

KUCZAC, S. (Ed.). Language Development. Volume I: Syntux and Semantics. Hillsdale, N.J.: Erlbaum. 1982. Pp. 492. ISBN 0 89859 1OO 7.

DEUTSCH, W. (Ed.). The Child's Construction of Languuge. London: Academic Press. 1981. Pp. 393. ISBN 0 12213580 6. £19.20.

BAKER, C. L. and MCCARTHY, J. J. (Eds). The Logical Problem of Language Acquisition. Cambridge, Mass.: MIT Press. 1981. Pp. 358. ISBN 0 262 02159 5. £19.25.

DIXON, N. F. Preconscious Processing Chichester: Wiley 1981. Pp. 313. ISBN 0 471 27982 X. £14.95.