Neuroscience Meeting Abstract   # 572.16

RECEPTIVE FIELD PROPERTIES OF K CELLS IN THE LATERAL
GENICULATE NUCLEUS (LGN) OF OWL MONKEYS (AOTUS TRIVIRGATUS)
  X-M. Xu1 ,  J. Boyd 2, J.D. Allison3, J. Ichida1, A.B. Bonds 3, & V. Casagrande* 1,2
Departments of  Psychology 1, Cell Biology 2, & Electrical Engineering 3, Vanderbilt
University; Nashville, TN 37232.

Primate striate cortex (V1) receives signals from the Koniocellular (K), Parvocellular
(P), Magnocellular (M) layers of the LGN, but little is known  in simian primates about
the properties of the K input.  To compare the receptive field properties of K LGN cells
with those of M and P LGN cells  in the owl monkey, a nocturnal simian, we recorded
the responses of LGN cells in paralyzed, anesthetized animals either directly from the
LGN or from LGN axons in cortex after cellular activity was silenced with muscimol.
In V1, K axons can be distinguished anatomically since they terminate within layers 3
and 1, while M and P axons terminate within the upper and lower halves of layer 4,
respectively.  Receptive fields were qualitatively examined with manually controlled
stimuli then quantitatively analyzed using drifting or counterphased sinusoidal gratings.
The locations of LGN cells were identified by lesions on sections stained for Nissl,
cytochrome oxidase, or calbindin.  A total of 15 K, 9 M, and 20 P cells were examined.
Four K cells exhibited unusual properties and could not be driven by grating stimuli.
Five K cells exhibited traditional center/surround fields and six had either ON-OFF
surrounds or no clear surround.  At  matched eccentricities of ?10?, K and P cells had
similar spatial frequency cut offs (K=2.32±0.48; P=2.38±0.50) which were higher than
those of M cells (1.73±0.63). Temporal frequency cut offs for all three cell classes
were similar (K=12.6±1.82; M=11.8±2.04; P=11.8±1.28).  K cells, like M cells,
exhibited higher contrast gain than P cells.  These results suggest that the K pathway
consists of at least two classes of cells, one of which could contribute to conventional
aspects of form and motion vision. (Supported by EY01778, EY03778, EY08126,
HD15052)