Spatio-temporal tuning of coherent motion evoked responses in 4-6 month old infants and adults.

Motion cues provide a rich source of information about translations of the observer through the environment as well as the movements of objects and surfaces. While the direction of motion can be extracted locally these local measurements are, in general, insufficient for determining object and surface motions. To study the development of local and global motion processing mechanisms, we recorded Visual Evoked Potentials (VEPs) in response to dynamic random dot displays that alternated between coherent rotational motion and random motion at 0.8 Hz. We compared the spatio-temporal tuning of the evoked response in 4-6 months old infants to that of adults by recording over a range of dot displacements and temporal update rates. Responses recorded at the frequency of the coherent motion modulation were tuned for displacement at the occipital midline in both adults in infants. Responses at lateral electrodes were tuned for speed in adults, but not in infants. Infant responses were maximal at a larger range of spatial displacement than that of adults. In contrast, responses recorded at the dot-update rate showed a more similar parametric displacement tuning and scalp topography in infants and adults. Taken together, our results suggest that while local motion processing is relatively mature at 4-6 months, global integration mechanisms exhibit significant immaturities at this age.

Acquisition of intellectual and perceptual-motor skills.

Recent evidence indicates that intellectual and perceptual-motor skills are acquired in fundamentally similar ways. Transfer specificity, generativity, and the use of abstract rules and reflexlike productions are similar in the two skill domains; brain sites subserving thought processes and perceptual-motor processes are not as distinct as once thought; explicit and implicit knowledge characterize both kinds of skill; learning rates, training effects, and learning stages are remarkably similar for the two skill classes; and imagery, long thought to play a distinctive role in high-level thought, also plays a role in perceptual-motor learning and control. The conclusion that intellectual skills and perceptual-motor skills are psychologically more alike than different accords with the view that all knowledge is performatory.

Body-centered representations for visually-guided action emerge during early infancy.

The nature of the spatial representations that underlie simple visually guided actions early in life were investigated through the application of a 'double-step' saccade paradigm to 3- and 7-month-old infants. Saccades in the older infants, like those observed in adults, were executed within body-centered spatial coordinates that take into account the effects of intervening eye movements. In contrast, younger infants tended to respond according to the targets' retinocentric locations and did not incorporate the effects of displacements caused by previous saccades. These results indicate that contrary to prevailing views, body-centered representations for action are not present from birth but emerge, probably through experience, over the first few months of life.

Working memory in infancy: six-month-olds' performance on two versions of the oculomotor delayed response task.

The capacity of 6-month-old infants to maintain information in working memory for several seconds was studied using two versions of an oculomotor delayed response task. Infants were presented with either a cue stimulus in a target location (Experiment 1), or an abstract, central stimulus (Experiment 2) which could be used to predict the peripheral location in which an attractive target stimulus subsequently appeared. Eye movements during delay periods from 600 to 5000 ms were recorded. The results indicated that infants maintained information about stimulus locations in working memory for 3-5 s. These results imply maturity of regions of the prefrontal cortex closely associated with a similar task used in neurophysiological and neuroimaging studies.