Graded sparing of visually-guided orienting following primary visual cortex ablations within the first postnatal month

We compared the abilities of intact cats and cats that incurred lesions of areas 17 and 18 in adulthood, at one month of age (P28), or on the day of b irth (P1), to detect and orient towards visual stimuli either moved into or illuminated in the periphery of the visual field, and to detect and orient towards a stationary, broad-band white-noise auditory stimulus. For all gr oups of cats, movement of a stimulus into the visual field was a more poten t stimulus for evoking visually-guided orienting movements than illuminatio n of a static light-emitting diode (LED). The potency of the auditory stimu lus was also extremely high. Proficiency on both visual tasks was graded ac cording to the age at which areas 17 and 18 were ablated in the sequence: a dult, P1, P28 and intact in the sequence worst double right arrow best perf ormance. The superior performance of the P1- and P28-groups provided eviden ce for sparing of visually-guided orienting, but the sparing was incomplete because it did not match performance of intact cats. Lesions of areas 17 a nd 18 incurred in adulthood had no significant impact on orienting to audit ory white-noise stimuli. However, orienting performance to auditory stimuli presented in the peripheral quadrants was slightly superior in the P28 gro up and reduced in the P1 group. Thus, the visual sparing exhibited by the P 1 group may be at the expense of highly proficient orienting to auditory cr ies. Overall, these results extend our knowledge by showing that in additio n to P1-cats, cats that incur lesions of areas 17 and 18 at one month-of-ag e also exhibit sparing of visually-guided orienting, and that the sparing i s not confined to a single stimulation paradigm. Finally, the covariation i n the magnitude of pathway modifications with the scale of the orienting pr oficiency in P1- and P28 cats helps to solidify the linkage between rewired brain pathways and spared visually-guided behaviors. (C) 2000 Elsevier Sci ence B.V. All rights reserved.