Abstract
We studied the development of spatial lateral interactions. Participants were adults (mean age = 23 years-old) and children aged 8, 10, 12, 14 and 16 years (n = 18 per age). We measured the apparent contrast of a foveally viewed Gabor as a function of the spacing of horizontally adjacent Gabors. Each Gabor had a contrast of 40%, a vertical carrier spatial frequency of 3 cycles per degree (γ = σ = 20 arc min), and a spread of 0.58 degrees. Inter-element spacing ranged from 1.5 to 6 cycles from the centre of the target to the centre of either of its adjacent flankers. The data make three points. First, at the smallest inter-element spacing, there is a reduction in the apparent contrast of the central Gabor for each age group tested. Second, at the smallest inter-element spacing, apparent contrast was significantly less reduced for the 8, 10, 12 and 14-year-olds compared to the two older groups. There was no significant difference between the 16-year-olds and the adults. Finally, compared to the adults, the measured reduction in apparent contrast extends over shorter distances for all other groups tested. Together, these results suggest that spatial lateral interactions mature very slowly and that they still have not reached adult-like characteristics by 16 years of age. This is consistent with recent findings that GABA expression in the human visual cortex does not become adult-like until late teens or even early adulthood [Boley et al., (2005). Society for Neuroscience].
Supported by an NSERC grant to D.E.