Scopolamine and physostigmine do not alter visual detection of change: relationships to a model of lateral geniculate operations.

The effects of physostigmine and scopolamine were tested on 5 male subjects using a task based on a model of cross-inhibition among lateral geniculate neurons. The task consisted of detecting and locating a change (appearance or disappearance) of one point of light in an array of points. Earlier research suggested that the task was sensitive to drugs and pathology. In the present study, neither drug showed significant effects on any of three task variables used, although differences between subjects were significant. These findings show that the task is sensitive to individual differences but insensitive to changes in cholinergic activity produced by physostigmine and scopolamine, even though such changes should affect neuronal functioning at the lateral geniculate.