Infants’ sensitivity to statistical distributions of motion direction and speed

Abstract

Adults combine different local motions to form a global percept of motion. This study explores the origins of this process by testing how perturbations of local motion influence infants' sensitivity to global motion. Infants at 6-, 12-, and 18-weeks of age viewed random dots moving with a gaussian distribution of dot directions defined by a mean of 0 degree (rightward) or 180 degrees (leftward) and a standard deviation (SD) of 0, 34, or 68 degrees. A well-practiced observer used infants' optokinetic responses to judge the direction of stimulus motion. Infants were studied both cross-sectionally and longitudinally. Direction discrimination was relatively high at all ages when the SD was 0 degree. When the SD was 34 or 68 degrees, performance declined with age. Adult performance was nearly perfect at these SDs. A similar developmental pattern was found with distributions of dot speed. The decline in infant performance is consistent with the development of both neural tuning and receptive field size. The subsequent improvement by adulthood suggests the development of additional processes such as long-range interactions.

Spontaneously emerging direction selectivity maps in visual cortex through STDP

“…Presumably circuits and mechanisms at both levels contribute to cortical direction selectivity (see also Mineiro and Zipser 1998;Bartsch and van Hemmen 2001;Yao et al 2004;Shon et al 2004) and our approach is to be understood as a hypothesis for and crude approximation of the intracortical part of a more complex mechanism. The finding of orientation selectivity being already present in newborn and thus visually inexperienced animals (Banton et al 1999;Issa et al 1999;Crair et al 1998;Katz and Shatz 1996;Chapman et al 1996;Sur and Leamey 2001;Ferster and Miller 2000) renders the scenario of cortex-intrinsic spontaneous activity (section 3.3) an imaginable model for the formation of direction selectivity and its corresponding map by spike-timing-dependent synaptic plasticity in early postnatal animals, possibly even before eye-opening.…”

Plasticity of the Dorsal “Spatial” Stream in Visually Deprived Individuals

“…Importantly, studies on the normal development of global motion processing, which is usually considered as an indicator of the dorsal stream maturation [22] suggest that sensitivity to global motion emerges between 6 to 11 weeks of age [23, 24] but reaches adult-like level of performance later in life, although the age of mature performance remains unclear. Some have reported that global motion perception is mature before 3 years of age [25], others between 6 and 11 years of age [17, 26, 27].…”

Development of Sensitivity to Texture and Contour Information in the Human Infant

“…Infants have been found to discriminate structure from motion random-dot displays by 7 months (Spitz, Stiles, & Siegel, 1993). At a more basic level of processing, the coherence threshold for the discrimination of a pattern made by moving dots is first measurable after approximately 3 months (Mason, Braddick, & Wattam-Bell, 2003;Banton, Dobkins, & Bertenthal, 2001;Banton, Bertenthal, & Seaks, 1999;Wattam-Bell, 1994). Fully adult performance appears to occur only in late childhood or early adolescence in both form and motion coherence tasks (Ellemberg, Lewis, Maurer, Brar, & Brent, 2002;Gunn et al, 2002;Lewis et al, 2002;Atkinson, 2000;Giaschi & Regan, 1997) as well as texture segmentation (Sireteanu & Rieth, 1992).…”