Probing human vision with spatial adaptation

Adaptation to spatial displays has robust effects on the perception of visual stimuli presented after adaptation. Referred to as the ‘psychophysicist’s microelectrode’ (Frisby, 1979), spatial adaptation and aftereffects has proved to be a powerful technique in the investigation of the functional organization of the human visual system. Our 20 years of collaboration on spatial adaptation research in the hospitable atmosphere of Lothar Spillmann’s laboratory at the University of Freiburg has resulted in a number of experiments that we believe have contributed to the understanding of the mechanism of these short-lived plasticity effects, and to the understanding of the development of spatial channels in the human visual system. It was quickly realized that visual aftereffects could be explained by mechanisms at the cellular level (Barlow, 1972; Braddick et al., 1978), and our psychophysical experiments pointed to the, now accepted, explanation in terms of lateral inhibition between stimulus-specific neural channels (Ursino et al., 2008). It now appears that a similar mechanism governs higher-level adaptation to complex stimuli such as human faces. The Gestalt psychologists described many of the figural aftereffects more than half century ago. It is appropriate that our research in this area was carried out in a German laboratory that so strongly continued the Gestalt tradition in perception research. Perception remains a mystery, but we now know a little more about the neural circuitry responsible for visual aftereffects, and we know a little more about ‘the way we see the world the way we do’ (Spillmann, 2009)