A generalized linear model of the impact of extra-retinal
input to the lateral geniculate nucleus
In press, J. of
Vision
Relay neurons in the Lateral Geniculate Nucleus (LGN) receive direct
visual input predominantly from a single retinal
ganglion cell (RGC), in addition to indirect input from other sources
including interneurons, thalamic reticular nucleus
(TRN) and the visual cortex. To address the extent of influence of
these indirect sources on the response properties of the
LGN neurons, we fit a Generalized Linear Model (GLM) to the spike
responses of cat LGN neurons driven by spatially
homogeneous spots that were rapidly modulated by a pseudo-random
luminance sequence. Several spot sizes were used
to probe the spatial extent of the indirect visual effects. Our
extracellular recordings captured both the LGN spikes and the
incoming RGC input (S potentials), allowing us to divide the inputs to
the GLM into two categories: the direct RGC input,
and the indirect input to which we have access through the luminance
of the visual stimulus. For spots no larger than the
receptive field center, the effect of the indirect input is
negligible, while for larger spots its effect can on average account
for 5% of the variance of the data, and for as much as 25% in some
cells. The polarity of the indirect visual influence is
opposite to that of the linear receptive field of the neurons. We
conclude that the indirect source of response modulation of
the LGN relay neurons arises from inhibitory sources, compatible with
thalamic interneurons or TRN.
Preprint (pdf, 700K) | Liam Paninski's home