Brisk Y-type ganglion cells in the cat retina exhibit a high frequency
resonance (HFR) in their responses to large, rapidly modulated stimuli. We
used a computer model to test whether negative feedback mediated by
axon-bearing amacrine cells onto ganglion cells could account for the
experimentally observed properties of HFRs. Temporal modulation transfer
functions (tMTFs) recorded from model ganglion cells exhibited HFR peaks
whose amplitude, width, and locations were qualitatively consistent with
experimental data. Moreover, the wide spatial distribution of
axon-mediated feedback accounted for the observed increase in HFR
amplitude with stimulus size. Model phase plots were qualitatively similar
to those recorded from Y ganglion cells, including an anomalous phase
advance that in our model coincided with the amplification of low-order
harmonics that overlapped the HFR peak. When axon-mediated feedback in the
model was directed primarily to bipolar cells, whose synaptic output was
graded, or else when the model was replaced with a simple cascade of
linear filters, it was possible to produce large HFR peaks but the region
of anomalous phase advance was always eliminated, suggesting the critical
involvement of strongly non-linear feedback loops. To investigate whether
HFRs might contribute to visual processing, we simulated high frequency
ocular tremor by rapidly modulating a naturalistic image. Visual signals
riding on top of the imposed jitter conveyed an enhanced representation of
large objects. We conclude that by amplifying responses to ocular tremor,
HFRs may selectively enhance the processing of large image features.