Brain Research, 338 (1985) 341- 345 341 Elsevier BRE 20924 Retinal and tectal responses to alternating gratings are unaffected by monocular deprivation in pigeons PAOLA BAGNOLP, VITTORIO PORCIATTI 2and WALTER FRANCESCONI 1 llstituto di Fisiologia dell'Universitd e lstituto di Neurofisiologia del C.N.R., 56100 Pisa and 2Divisione Oculistica, USL 13, 57100 Livorno (Italy) (Accepted February 19th, 1985) Key words: electroretinogram - - tectal evoked potential - - grating - - monocular deprivation - - pigeon Retinal and tectal potentials to alternating gratings were recorded in pigeons raised monocularly deprived. Deprived eyes showed consistent myopia and anterior-posterior axis elongation. In addition, vitreal opacities were observed in 70% of the deprived eyes. In pigeons with vitreal opacities, a reduction of retinal and tectal response amplitude was consistently found in the high spatial frequency range. Pigeons with clear media of the deprived eyes showed normal retinal and tectal responses. Although the morphofunctional changes observed in the mammalian geniculocortical pathway after prolonged early monocular deprivation are extreme- ly dramatic and well documented, questions remain concerning the extent of the deprivation-induced changes at the retinal level. On the one hand, kittens either monocularly de- prived or raised with a convergent squint showed a reduction in the spatial resolving power of retinal ganglion cells6:3: 9. Reduction in pattern-electroreti- nogram (ERG) amplitude was also shown in human amblyopes~,25, and a reduction in the ERG b-wave was reported in dark-reared kittens S and guinea pigs is. In addition, morphological and biochemical changes were reported at the retinal level in animals exposed to varying visual environmentslS,21.26,28 (see ref. 3 for references). On the other hand, several studies on monocularly lid-sutured kittens have consistently reported normal spatial resolution7,J7 and normal receptive field prop- erties24 of deprived 'X' and 'Y' ganglion cells. Recently, the avian visual system has provided a useful model in searching for the neuronal correlates of early visual deprivation. A dramatic loss of binoc- ularly driven neurons was demonstrated in the visual Wulst of owls raised with one eye sutured 20. In addi- tion, significant deficits in pattern discrimination learning and interocular transfer were described in early monocularly deprived pigeons 5. Furthermore, preliminary results have indicated a behavioral im- pairment of the spatial acuity of pigeons' deprived eyes (Burkhalter and Kniisel, personal communica- tion). The aim of this work was to determine whether pattern-ERG and tectal surface-evoked potentials (TEPs) were affected by early monocular depriva- tion. In monocularly deprived pigeons, we compared the amplitudes of ERG and TEP to alternating grat- ings of various spatial frequencies presented to the deprived eyes to those of the responses elicited by the stimulation of the undeprived eyes. Experiments were performed on 10 pigeons of both sexes weighing 350-400 g which were monocu- larly deprived during the first 6 months of life by cov- ering one eye with a black plastic cap immediately af- ter hatching (for details of the procedure see Burk- halter and Cu6nod5). Details of the electrophysiological technique have been previously describedL Briefly, the pigeons Correspondence: P. Bagnoli, Instituto di Fisiologia dell'Universit~ e Istituto di Neurofisiologia del C.N.R., Via S. Zeno, 31-51, 56100 Pisa, Italy. 0006-8993/85/$03.30 © 1985 Elsevier Science Publishers B.V. (Biomedical Division)