, , ,

Underestimation of perceived number at the time of saccades,Vision Res, 1 (51), 34-42.

Underestimation of perceived number at the time of saccades,Vision Res, 1 (51), 34-42. 

Download

Saccadic eye movements produce transient distortions in both space and time. Mounting evidence suggests that space and time perception are linked, and associated with the perception of another important perceptual attribute, numerosity. Here we investigate the effect of saccades on the perceived numerosity of briefly presented arrays of visual elements. We report a systematic underestimation of numerosity for stimuli flashed just before or during saccades, of about 35% of the reference numerosity. The bias is observed only for relatively large arrays of visual elements, in line with the notion that a distinct perceptual mechanism is involved with enumeration of small numerosities in the ‘subitizing’ range. This study provides further evidence for the notion that space, time and number share common neural representations, all affected by saccades.

, , ,

Brief periods of monocular deprivation disrupt ocular balance in human adult visual cortex, Curr Biol. 2011 Jul 26;21(14):R538-9.

Brief periods of monocular deprivation disrupt ocular balance in human adult visual cortex, Curr Biol. 2011 Jul 26;21(14):R538-9.

Download

Neuroplasticity is a fundamental property of the developing mammalian visual system, with residual potential in adult human cortex [1]. A short period of abnormal visual experience (such as occlusion of one eye) before closure of the critical period has dramatic and permanent neural consequences, reshaping visual cortical organization in favour of the non-deprived eye [2,3]. We used binocular rivalry [4] – a sensitive probe of neural competition – to demonstrate that adult human visual cortex retains a surprisingly high degree of neural plasticity, with important perceptual consequences. We report that 150 minutes of monocular deprivation strongly affects the dynamics of binocular rivalry, unexpectedly causing the deprived eye to prevail in conscious perception twice as much as the non-deprived eye, with significant effects for up to 90 minutes. Apparent contrast of stimuli presented to the deprived eye was also increased, suggesting that the deprivation acts by up-regulation of cortical gain-control mechanisms of the deprived eye. The results suggest that adult visual cortex retains a good deal of plasticity that could be important in reaction to sensory loss.

, , , ,

Spatiotopic selectivity of adaptation-based compression of event duration, J Vis, 2 (11), 21; author reply 21a.

Spatiotopic selectivity of adaptation-based compression of event duration, J Vis, 2 (11), 21; author reply 21a.

Download

A. Bruno, I. Ayhan, and A. Johnston (2010) have recently challenged our report of spatiotopic selectivity for adaptation of event time (D. Burr, A. Tozzi, & M. C. Morrone, 2007) and also our claim that retinotopic adaptation of event time depends on perceived speed. To assist the reader judge this issue, we present here a mass of data accumulated in our laboratories over the last few years, all confirming our original conclusions. We also point out that where Bruno et al. made experimental measurements (rather than relying on theoretical reasoning), they too find clearly significant spatiotopically tuned adaptation-based compression of event time but of lower magnitude to ours. We speculate on the reasons for the differences in magnitude