Abstract
Optic flow provides an individual with information about her speed and direction of self-motion (Britten, 2008; Gibson, 1950). Radial (expansion/contraction) optic flow patterns elicit robust evoked potential responses in adults, while responses to rotation and translation (left/right) patterns are weaker. Comparatively, infants show the strongest evoked responses to lateral translation (Gilmore et al., 2007). Adult-like spatial and temporal tuning to global motion develops over a prolonged time period (Kiorpes & Movshon, 2004; Hou et al., 2009). For this study, we recorded steady-state visual evoked potential (SSVEP) responses among children of 4 to 8-years to coherence modulations of three optic flow pattern types (lateral translation, rotation, and radial expansion/contraction) at 3 different speeds (2, 4, and 8 deg/s), using an electrode net of 128 channels. Children (n= 20) viewed moving dot displays (7 amin dots, 79.4 cd/m2, density = 10%) that modulated in time from incoherent to 100% coherent global motion at 1.2 Hz (F1). All displays had the same dot update rate (24 Hz, F2). As a group, children’s responses to coherence modulation were largest for the radial patterns with peak responses observed over medial occipital electrodes. However, individual age groups displayed differential tuning. Four-year-olds showed the most robust responses to translation over the lateral occipital electrodes while 5-year-olds showed the strongest responses to translation and radial patterns. Six and 7-year-olds displayed strong responses to radial and rotation patterns. Finally, 8-year-olds displayed weak responses to translation and rotation, but strong responses to radial motion over medial occipital channels. Overall, speed tuning varied by pattern type, scalp location, and age group. The results suggest that adult-like sensitivity to optic flow patterns emerges in middle childhood, that optic flow engages a network of visually sensitive areas, and that there are multiple trajectories associated with the development of optic flow processing.
Meeting abstract presented at VSS 2012