DEVELOPMENT OF CONTRAST SENSITIVITY AND TEMPORAL-FREQUENCY SELECTIVITY IN PRIMATE LATERAL GENICULATE-NUCLEUS

We studied the development of spatial contrast-sensitivity and tempora l-frequency selectivity for neurons in the monkey lateral geniculate n ucleus. During postnatal week 1, the spatial properties of P-cells and M-cells are hardly distinguishable, with low contrast-sensitivity, sl uggish responses, and poor spatial resolution. The acuity of P-cells i mproves progressively until at least 8 months, but there is no obvious increase in their maximum contrast-sensitivity with age. The contrast sensitivity of M-cells is already clearly higher than that of P-cells by 2 months, and at 8 months of age this characteristic difference be tween M- and P-cells approaches the adult pattern. There Is a major in crease in responsiveness during the first 2 postnatal months, especial ly for M-cells, the peak firing rate of which rises fivefold, on avera ge, between birth and 2 months. Many P-cells in the neonatal and 2-mon th-old animals did not give statistically reliable responses to achrom atic gratings, even at the highest contrasts: this unresponsiveness of P-cells might result from low gain and/or chromatic opponency. The up per limit Of temporal resolution in the neonate is low - about one-thi rd of that in the adult. Among M-cells, the improvement in temporal re solution, like that in contrast sensitivity, is rapid over the first 2 months, followed by a slower change approaching the adult value by 8 months of age. The development of contrast sensitivity, responsiveness and temporal tuning are little affected, if at all, by binocular depr ivation of pattern vision from birth for even a prolonged period.