FUNCTIONAL SPECIFICITY OF LONG-RANGE INTRINSIC AND INTERHEMISPHERIC CONNECTIONS IN THE VISUAL-CORTEX OF STRABISMIC CATS

The development of both long-range intracortical and interhemispheric connections depends on visual experience. Previous experiments showed that in strabismic but not in normal cats, clustered horizontal axon p rojections preferentially connect cell groups activated by the same ey e. This indicates that there is selective stabilization of fibers betw een neurons exhibiting correlated activity. Extending these experiment s, we investigated in strabismic cats: (1) whether tangential connecti ons remain confined to columns of similar orientation preference withi n the subsystems of left and right eye domains; and (2) whether callos al connections also extend predominantly between neurons activated by the same eye and preferring similar orientations. To this end, we anal yzed in strabismic cats the topographic relationships between orientat ion preference domains and both intrinsic and callosal connections of area 17. Red and green latex microspheres were injected into monocular iso-orientation domains identified by optical imaging of intrinsic si gnals. Additionally, domains sharing the ocular dominance and orientat ion preference of the neurons at the injection sites were visualized b y 2-deoxyglucose (2-DG) autoradiography. Quantitative analysis reveale d that 56% of the retrogradely labeled cells within the injected area 17 and 60% of the transcallosally labeled neurons were located in the 2-DG-labeled iso-orientation domains. This indicates: (1) that strabis mus does not interfere with the tendency of long-range horizontal fibe rs to link predominantly neurons of similar orientation preference; an d (2) that the selection mechanisms for the stabilization of callosal connections are similar to those that are responsible for the specific ation of the tangential intrinsic connections.