Putting order into the development of sensitivity to global motion.
We studied differences in the development of sensitivity to first-versus second-order global motion by comparing the motion coherence thresholds of 5-year-olds and adults tested at three speeds (1.5, 6, and 9 degrees s(-1)). We used Random Gabor Kinematograms (RGKs) formed with luminance-modulated (first-order) or contrast-modulated (second-order) concentric Gabor patterns with a sinusoidal spatial frequency of 3c deg(-1). To achieve equal visibility, modulation depth was set at 30% for first-order Gabors and at 100%, for second-order Gabors. Subjects were 24 adults and 24 5-year-olds. For both first- and second-order global motion, the motion coherence threshold of 5-year-olds was less mature for the slowest speed (1.5 degrees s(-1)) than for the two faster speeds (6 and 9 degrees s(-1)). In addition, at the slowest speed, the immaturity was greater for second-order than for first-order global motion. The findings suggest that the extrastriate mechanisms underlying the perception of global motion are different, at least in part, for first- versus second-order signals and for slower versus faster speeds. They also suggest that those separate mechanisms mature at different rates during middle childhood.
Ellemberg
D
D
McGill Vision Research, Department of Ophthalmology, McGill University, Montréal, Québec, Canada. dave.ellemberg@staff.mcgill.ca
Lewis
T L
TL
Dirks
M
M
Maurer
D
D
Ledgeway
T
T
Guillemot
J-P
JP
Lepore
F
F
D000293:Adolescent; D000328:Adult; D000375:Aging / Q000523:psychology*; D000704:Analysis of Variance; D002675:Child, Preschool; D006801:Humans; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D012684:Sensory Thresholds / Q000502:physiology