A Comparison of Koniocellular ( K ) , Magnocellular ( M ) , and Parvocellular ( P ) Receptive Field Properties in the Lateral Geniculate Nucleus ( LGN ) of the Owl Monkey ( Aotus trivirgatus )

1. We examined the receptive properties of the Koniocellular (K), Magnocellular (M), and Parvocellular (P) cells in the lateral geniculate nucleus (LGN) of the New world nocturnal simian owl monkey, aiming to characterize receptive field properties of K LGN cells by comparing the K cell properties with those of M and P LGN cells. The key objective of the present study was to proceed by analogy to previous physiological work on magnocellular (M) and Parvocellular (P) lateral geniculate nucleus (LGN) cells and put together a physiological profile of koniocellular (K) LGN cells that might be linked to particular visual perceptual attributes. 2. Conventional extracellular recording techniques were employed to study the receptive field properties of neurons in the LGN or their axons in silenced V1 cortex in nine anesthetized paralyzed owl monkeys. Receptive field center and surround properties were mapped using flashing spots and field center sizes were measured. Spatial and temporal tuning, and contrast response characteristics of cells were examined by using drifting sine-wave gratings. Cells were tested with counterphased sine-wave gratings to examine linearity of spatial summation. Locations of recorded cells were determined based upon electrode tracts marked with lesions as well as changes in eye dominance, and structural boundaries determined by histological (Nissl), histochemical (cytochrome oxidase), or immuncytochemical (K cells contain calbindin-D 28K) criteria. 3 3. The receptive field properties of a total of 133 LGN cells and 10 LGN afferent axons were analyzed at eccentricities ranging from 2.8 to 31.3 degrees. From this population 38 K, 45 P, and 34 M units could be assigned with confidence to specific LGN layers. 4. The K cells as a population are quite heterogenous in response properties and receptive field organization, relative to the P and M cells. A significant proportion (34%) of K cells responded poorly or not at all to drifting gratings whereas only 9% of P and 6% of M cells responded poorly to drifting gratings. Cells in all 3 classes exhibited increases in receptive field center size with eccentricity but the K population showed more scatter. 5. All K, P and M cells except one M cell, tested with counterphased gratings, showed linearity in spatial summation of their receptive fields. 6. K, P, and M cell populations showed significant overlap in spatial and temporal resolution and in contrast response. On average, at matched eccentricities, K cells exhibited lower spatial resolution than the P and M …