RT Journal Article
SR Electronic
T1 Functional Circuitry of the Retinal Ganglion Cell's Nonlinear Receptive Field
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 9756
OP 9767
DO 10.1523/JNEUROSCI.19-22-09756.1999
VO 19
IS 22
A1 Jonathan B. Demb
A1 Loren Haarsma
A1 Michael A. Freed
A1 Peter Sterling
YR 1999
UL http://www.jneurosci.org/content/19/22/9756.abstract
AB A retinal ganglion cell commonly expresses two spatially overlapping receptive field mechanisms. One is the familiar “center/surround,” which sums excitation and inhibition across a region somewhat broader than the ganglion cell's dendritic field. This mechanism responds to a drifting grating by modulating firing at the drift frequency (linear response). Less familiar is the “nonlinear” mechanism, which sums the rectified output of many small subunits that extend for millimeters beyond the dendritic field. This mechanism responds to a contrast-reversing grating by modulating firing at twice the reversal frequency (nonlinear response). We investigated this nonlinear mechanism by presenting visual stimuli to the intact guinea pig retina in vitro while recording intracellularly from large brisk and sluggish ganglion cells. A contrast-reversing grating modulated the membrane potential (in addition to the firing rate) at twice the reversal frequency. This response was initially hyperpolarizing for some cells (either ON or OFF center) and initially depolarizing for others. Experiments in which responses to bars were summed in-phase or out-of-phase suggested that the single class of bipolar cells (either ON or OFF) that drives the center/surround response also drives the nonlinear response. Consistent with this, nonlinear responses persisted in OFF ganglion cells when ON bipolar cell responses were blocked by l-AP-4. Nonlinear responses evoked from millimeters beyond the ganglion cell were eliminated by tetrodotoxin. Thus, to relay the response from distant regions of the receptive field requires a spiking interneuron. Nonlinear responses from different regions of the receptive field added linearly.