Cortico-geniculate feedback linking the visual fields surrounding the blind spot in the cat.
Previous studies have shown that neurons in layer 6 of V1 are activated by visual stimuli that induce perceptual filling-in at the blind spot (BS). As the main target of layer 6 neurons is the lateral geniculate nucleus (LGN), we speculate that the cortico-geniculate projection is involved in mediating filling-in at BS. To begin to test that hypothesis, we examined whether there is an anatomical basis for integration of visual signals from both sides of BS by cortico-geniculate feedback neurons in V1. We injected an anterograde tracer into a site adjacent to the region representing BS. We observed that numerous axons traverse the neuron-free gap that retinotopically corresponds to BS within LGN. This indicates that visual signals from one side of BS are conveyed to the opposite side via a feedback connection. Cortico-geniculate feedback projection may integrate visual signals from around BS and contribute to perceptual filling-in at BS.
Yokoi
Isao
I
Division of Sensory and Cognitive Information, National Institute for Physiological Sciences, Okazaki, 444-8585, Aichi, Japan.
Komatsu
Hidehiko
H
D000818:Animals; D001369:Axons; D001710:Biotin / Q000031:analogs & derivatives; D002415:Cats; D003911:Dextrans; D025461:Feedback, Physiological; D005829:Geniculate Bodies / Q000033:anatomy & histology* / Q000166:cytology; D056325:Neuronal Tract-Tracers; D009474:Neurons / Q000166:cytology*; D009898:Optic Disk / Q000033:anatomy & histology* / Q000166:cytology; D014793:Visual Cortex / Q000033:anatomy & histology* / Q000166:cytology; D014795:Visual Pathways / Q000033:anatomy & histology* / Q000166:cytology; D014796:Visual Perception
D003911:Dextrans; D056325:Neuronal Tract-Tracers; C076397:biotinylated dextran amine; D001710:Biotin