Perception, 1981, volume 10, pages 511-518 A study of interocular transfer of spatial adaptation Roald A Bjrfrklund, Svein Magnussen Institute of Psychology, University of Oslo, Box 1094, Blindern, Oslo 3, Norway Received 27 November 1980, in revised form 23 February 1981 Abstract. The threshold-elevation aftereffect was measured ipsiocularly and interocularly following grating adaptation of one eye. The functions relating aftereffect magnitude to adapting contrast and adaptation time were similar under the two testing conditions, with interocular transfer remaining fairly constant; decay times were similar for ipsiocular and interocular aftereffects of comparable magnitude, and their frequency selectivities were the same. It is concluded that the stimulus-response characteristics of monocular and binocular spatial channels are fundamentally similar. 1 Introduction Prolonged inspection of a high-contrast spatial luminance grating may affect the perception of a subsequently presented test grating in several ways (Anstis 1975; Braddick et al 1978). One consequence is a rise in the contrast threshold for detecting test gratings of similar spatial frequencies and orientations (Pantle and Sekuler 1968; Gilinsky 1968; Blakemore and Campbell 1969). This threshold- elevation aftereffect must have a cortical basis because it transfers interocularly, even when the adapted eye is pressure-blinded during the transfer test (Blake and Fox 1972). Blakemore and Campbell (1969) and Gilinsky and Doherty (1969) found, however, that the ipsiocular threshold elevation (adapting and test grating to the same eye) was larger than the interocular effect (adapting and test gratings to separate eyes), suggesting that the aftereffect has both a monocular and a binocular component. Similar results have been reported for other well-known aftereffects, such as the tilt aftereffect (Gibson 1937), the movement aftereffect (Mitchell et al 1975), and the perceived spatial-frequency shift (Blakemore et al 1970). The amount of interocular transfer of simple visual aftereffects varies with several factors including type of stimuli employed, testing conditions, and subjects. Sharpe (1974) found that the interocular transfer of the threshold-elevation aftereffect was greater for adapting and test gratings of different colour than for gratings of the same colour, even though threshold elevation as such was much larger in the latter condition, suggesting that the monocular component of adaptation is tied to colour- coded cortical cells (see also Stromeyer 1978). Fiorentini et al (1976) report that the threshold-elevation aftereffect transfers interocularly when tested with gratings but not when tested with single lines, in contrast to the tilt aftereffect which exhibits interocular transfer for both types of stimuli (Gibson 1937; Movshon et al 1972; Mitchell and Ware 1974). Both the threshold-elevation (Bj^rklund 1976) and movement aftereffects (Lehmkuhle and Fox 1976) exhibit greater transfer when the unadapted eye is diffusely illuminated during the adaptation phase compared to when it is occluded, and several authors (eg Movshon et al 1972; Mitchell and Ware 1974) report that transfer is greater from the dominant to the nondominant eye than vice versa. For a particular set of testing conditions there is considerable variability among subjects; an important factor here is the fidelity of the subject's stereoscopic vision (Movshon et al 1972; Mitchell and Ware 1974; Mitchell et al 1975; Lema and Blake 1977; Anderson et.al 1980).