ON and OFF activity gradients in the lateral geniculate nucleus of the cat: a combined 14C 2-deoxyglucose and D,L-2-amino-4-phosphonobutyric acid study.
Experiments on the lateral geniculate nucleus (LGN) of the cat based on 14C 2-deoxyglucose (2-DG) autoradiography and intraocular injections of 2-amino-4-phosphonobutyric acid (APB) provided evidence for gradients of metabolic activity in the ON and OFF pathways in layer A, but only very weakly, if at all, in layer A1. Alert and freely moving cats were exposed to square-wave gratings over a 45-min period after injection of the 2-DG. When one eye had been treated previously with APB, contralateral layer A showed a clear gradient of 2-DG label indicating that the remaining OFF pathway was most active ventrally in the layer and, by implication, that the ON pathway is normally most active dorsally. No gradient was apparent in layer A1 ipsilateral to the APB eye. Control experiments based on binocular injections of tetrodotoxin (TTX) demonstrated that no gradients were present in the baseline activity within the layers. Finally, monocular injections of TTX provided evidence for gradients of nondominant eye activity in layers A and A1 that were maximal near the interlaminar zone between layers A and A1 and declined in mirror-symmetric fashion toward the dorsal border of A and the ventral border of A1. Combined with earlier anatomical studies showing depth-dependent patterns of geniculo-cortical projection, these results indicate that in the cat, as in several other species, the visual input to striate cortex is partly organized around ON and OFF pathways. In addition, the results suggest that a systematic variation of binocular interaction, perhaps related to ocular dominance, exists through the depths of the geniculate layers.(ABSTRACT TRUNCATED AT 250 WORDS)
Thurlow
G A
GA
Department of Medical Physiology, University of Calgary, Alberta, Canada.
Bowling
D B
DB
Cooper
R M
RM
D000613:Aminobutyrates / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D002250:Carbon Radioisotopes; D002415:Cats; D003847:Deoxyglucose / Q000494:pharmacology; D005829:Geniculate Bodies / Q000033:anatomy & histology / Q000502:physiology*; D007091:Image Processing, Computer-Assisted; D015348:Vision, Binocular; D014793:Visual Cortex / Q000502:physiology; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology*
D000613:Aminobutyrates; D002250:Carbon Radioisotopes; D003847:Deoxyglucose; C012729:2-amino-4-phosphonobutyric acid