Detection of global coherent form in patterns of line segments gives a measure of extrastriate processing in the ventral stream. This is analogous to the measurement of dorsal stream performance through motion coherence. In infancy, sensitivity to local pattern (orientation discrimination & VEP) develops before the corresponding sensitivity to directional motion. However, using preferential looking, we have shown detection of global coherent form in infants only after 12 weeks of age. We have now also tested infants’ sensitivity to form coherence by habituation/recovery. Preference for an array containing concentrically aligned line segments was tested, following repeated exposure to a random array, in infants aged 8-20 weeks. Results with this method support our finding that infants over 12 weeks, but not younger, are sensitive to global form coherence. In comparison, we have demonstrated global motion sensitivity in infants as young as 8-10 weeks, suggesting more rapid development of dorsal compared to ventral global processing. We will compare form and motion coherence sensitivity in individual infants, and discuss this in relation to the slower maturation and relative vulnerability of global motion vs form processing in later childhood and in developmental disorders (Williams Syndrome, autism, hemiplegia, prematurity; e.g. Atkinson et al, VSS, 2003, ARVO 2004). A further possibility is that sensitivity to different types of global form organization develop at different ages, reflecting functioning in different extrastriate networks: e.g. sensitivity to parallel texture vs global concentric pattern, which have been shown to involve different integrative processes in adults (Braddick et al, VSS 2004). This suggests that extrastriate ventral stream processing, and its development, involves distinct multiple networks.

Medical Research Council grant G7908507