MONOCULARLY INDUCED 2-DEOXYGLUCOSE PATTERNS IN THE VISUAL-CORTEX AND LATERAL GENICULATE-NUCLEUS OF THE CAT .2. AWAKE ANIMALS AND STRABISMICANIMALS

In the course of experiments studying the organization of ocular domin ance columns in the visual cortex of cats, we noticed that-contrary to common belief-labelling with 2-deoxyglucose after monocular stimulati on failed to induce a pattern of ocular dominance columns but resulted in a rather homogeneous 2-deoxyglucose uptake throughout area 17 in a naesthetized and paralysed animals. We wondered whether 2-deoxyglucose columns could be obtained in awake animals and/or in strabismic anima ls, which have a more pronounced segregation of ocular dominance colum ns. To this end, we investigated 2-deoxyglucose patterns after monocul ar stimulation in three groups of animals: (i) in awake normally reare d cats, (ii) in awake strabismic cats and (iii) in anaesthetized and p aralysed strabismic cats. Additionally, we labelled ocular dominance c olumns with intraocular [H-3]proline injections. In all cats, monocula r stimulation induced 2-deoxyglucose patterns that were in precise reg ister with the proline-labelled ocular dominance columns in layer IV. Regions of increased 2-deoxyglucose uptake extended in a columnar fash ion through all cortical layers. In contrast to normally reared animal s, in strabismic cats, the expression of 2-deoxyglucose labelled ocula r dominance columns was not abolished by anaesthesia or paralysis. How ever, there was a difference between the 2-deoxyglucose patterns in th e awake normally reared cats and the strabismic animals. In the former , the patches of 2-deoxyglucose labelling were smaller and occupied le ss territory than the afferents of the stimulated eye in layer IV. Tog ether with the results of the previous study, these data indicate that in awake normally reared and in awake and anaesthetized strabismic ca ts, but not in anaesthetized and paralysed normally reared animals, mo nocular stimulation activates selectively neurons in columns that are in register with the termination sites of afferents from the stimulate d eye. This suggests the existence of a mechanism in normally reared a nimals which restricts cortical activation after monocular stimulation to territories that are in register with the afferents from the stimu lated eye. This mechanism appears to be effective only when the animal s are awake and actively exploring their environment. This and the fac t that the active columns were narrower than the terminal fields of th e stimulated eye suggest an active inhibitory process, perhaps related to mechanisms of selective attention. The observation that ocular dom inance columns persist in strabismic cats even under anaesthesia can b e accounted for by the lack of binocular convergence in these animals.