We grew up thinking that all our channels are always available, waiting to be used, like the strings in a piano. Majaj et al. (2002 & this VSS) show that observers identifying letters or reading use only one spatial frequency channel, determined by the stroke frequency of the letters. We show that this is also true for faces and line drawings of common objects. There are indications that our visual system assigns an independent neural assembly to each perceived object/event in order to estimate speed or orientation, or track position (Verghese & Stone, 1995; Berger et al., submitted; Pylyshyn, 1989). Are all these mechanisms--channels, estimators, and trackers--just different aspects of the same neural assembly, synthesized, bottom-up, by the visual system, to represent each perceived object/event?

REFERENCES: Berger, T. D., Martelli, M., and Pelli, D. G. (submitted) Flicker flutter: Is an illusory event as good as the real thing? Journal of Vision. Majaj, N. J., Pelli, D. G., Kurshan, P., and Palomares, M. (2002) The role of spatial frequency channels in letter identification. Vision Res, 42 (9), 1165-84. Pylyshyn, Z. (1989) The role of location indexes in spatial perception: a sketch of the FINST spatial-index model. Cognition, 32 (1), 65-97. Verghese, P. and Stone, L. S. (1995) Combining speed information across space. Vision Res, 35 (20), 2811-23.