Short-term reorganization of the cortical network? Some questions from visual psychophysics.

Research into visual system function requires the use of test stimuli as (would-be) neutral probes. Although the risk of transient 'fatigue' is well recognized, e.g. in relation to dark adaptation, we tend otherwise to assume that the system will respond reversibly to stimuli within normal physiological limits. It is on this assumption that gratings of near-parallel lines, for example, are commonly used to determine both physiological and psychophysical response characteristics. This paper reviews evidence suggesting that certain classes of visual stimuli, including gratings in particular, can induce a short-term cooperative reorganization of the visual network that leaves it far from normal in its responsiveness to other inputs. It is suggested that the resulting abnormalities may help to shape our ideas as to the cooperative ensemble properties of cortical neuronal network.