THE TIME-COURSE OF LEARNING A VISUAL SKILL

SEVERAL examples of experience-dependent perceptual improvement (perce ptual learning) suggest that plasticity in specific neuronal loci coul d underlie the learning process1-6. For a basic visual discrimination task (using an optimal stimulus for 'automatic' pre-attentive texture segregation7-10), discrete retinal input-dependent changes within a ve ry early stage in the stream of visual processing were indicated as th e locus of a large and consistent learning effect5. When do these chan ges occur? Here we report that except for a fast, rapidly saturating i mprovement early in the first practice session, performance was very s table within sessions. Indeed, observers showed little or no improveme nt until up to 8 hours after their last training session (latent phase ). But large improvements occurred thereafter. Finally, there was almo st no forgetting; what was gained was retained for at least 2-3 years. We conjecture that some types of perceptual experience trigger perman ent neural changes in early processing stages of the adult visual syst em. These may take many hours to become functional.