Persistence and extinction of the effect of visual pattern deprivation in the fly.

Visual pattern discrimination in the fly (Boettcherisca peregrina) is dependent on post-emergence experience of light and visual patterns (Mimura 1986). A behavioural study was made on the persistence of the functional modification that results from visual deprivation. When the fly was kept in the dark for 5 days post-emergence, the development of visual pattern discrimination was impaired completely, irrespective of the subsequent light condition, while photosensitivity was not impaired. A "deprivation" effect could also be produced by exposing the fly for at least 1 h soon after emergence to a definite pattern instead of its usual contrasted environment. Persistence of this deprivation effect depended on the subsequent light conditions: The effect was more persistent when the flies were kept in continuous darkness (DD) than when they were raised in light-dark (LD) environment; and The longer the presentation of a definite pattern, the more stable was the deprivation effect. Extinction of the deprivation effect was replaced with the development of normal pattern discrimination. In flies that had experienced a lighted, white, unpatterned environment after emergence, the normal development of pattern discrimination was impaired. This deprivation effect was persistently maintained when flies were kept in DD, but when flies were exposed to this environment for 5 h or more and then kept in LD, normal pattern discrimination developed gradually.