PAPER Longitudinal study of perception of structured optic flow and random visual motion in infants using high-density EEG Seth B. Agyei, Magnus Holth, F.R. (Ruud) van der Weel and Audrey L.H. van der Meer Department of Psychology, Norwegian University of Science and Technology, Norway Abstract Electroencephalogram (EEG) was used in infants at 3–4 months and 11–12 months to longitudinally study brain electrical activity as the infants were exposed to structured forwards and reversed optic flow, and non-structured random visual motion. Analyses of visual evoked potential (VEP) and temporal spectral evolution (TSE, time-dependent amplitude changes) were performed on EEG data recorded with a 128-channel sensor array. VEP results showed infants to significantly differentiate between the radial motion conditions, but only at 11–12 months where they showed shortest latency for forwards optic flow and longest latency for random visual motion. When the TSE results of the motion conditions were compared with those of a static non-flow dot pattern, infants at 3–4 and 11–12 months both showed significant differences in induced activity. A decrease in amplitudes at 5–7 Hz was observed as desynchronized theta-band activity at both 3–4 and 11–12 months, while an increase in amplitudes at 9–13 Hz was observed as synchronized alpha-band activity only at 11–12 months. It was concluded that brain electrical activities related to visual motion perception change during the first year of life, and these changes can be observed both in the VEP and induced activities of EEG. With adequate neurobiological development and locomotor experience infants around 1 year of age rely, more so than when they were younger, on structured optic flow and show a more adult-like specialization for motion where fasteroscillating cell assemblies have fewer but more specialized neurons, resulting in improved visual motion perception. Research highlights • As infants become more and more mobile during the first year of life, they depend to a greater extent on the correct pick-up of visual information specifying (self-)motion. • We studied the development of perception of struc- tured optic flow and random visual motion in infants using high-density EEG. • Brain electrical activities related to visual motion perception change during the first year of life, and these changes can be observed both in VEP and induced activities in EEG. • With adequate neurobiological development and locomotor experience infants around 1 year of age rely, more so than when they were younger, on structured optic flow and show a more adult-like specialization for motion where faster oscillating cell assemblies have fewer but more specialized neurons, resulting in improved visual motion perception. Introduction Perception of optic flow, the pattern of visual informa- tion resulting from an observer’s own motion (Gibson, 1979), plays an important role when navigating through our surroundings (for a review, see Lappe, Bremmer & Van den Berg, 1999). Optic flow information helps in determining direction of heading, stabilizing posture, and estimating the time taken to make contact with objects (Vaina & Rushton, 2000). Developmental studies have shown that infants are able to discriminate large changes in heading from optic flow prior to the onset of locomotion (Gilmore, Baker & Grobman, 2004; Gilmore & Rettke, 2003; Wattam-Bell, Address for correspondence: Audrey L.H. van der Meer, Developmental Neuroscience Laboratory, Department of Psychology, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway; e-mail: audrey.meer@svt.ntnu.no © 2014 John Wiley & Sons Ltd Developmental Science (2014), pp 1–16 DOI: 10.1111/desc.12221