Browsing by Author "Ruda, Kiersten"
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Item Open Access Ignoring correlated activity causes a failure of retinal population codes.(Nature communications, 2020-09-14) Ruda, Kiersten; Zylberberg, Joel; Field, Greg DFrom starlight to sunlight, adaptation alters retinal output, changing both the signal and noise among populations of retinal ganglion cells (RGCs). Here we determine how these light level-dependent changes impact decoding of retinal output, testing the importance of accounting for RGC noise correlations to optimally read out retinal activity. We find that at moonlight conditions, correlated noise is greater and assuming independent noise severely diminishes decoding performance. In fact, assuming independence among a local population of RGCs produces worse decoding than using a single RGC, demonstrating a failure of population codes when correlated noise is substantial and ignored. We generalize these results with a simple model to determine what conditions dictate this failure of population processing. This work elucidates the circumstances in which accounting for noise correlations is necessary to take advantage of population-level codes and shows that sensory adaptation can strongly impact decoding requirements on downstream brain areas.Item Open Access Retinal Ganglion Cell Population Codes From Starlight to Sunlight(2020) Ruda, KierstenThe retina signals visual information to the brain with the parallel channels of different retinal ganglion cell (RGC) types, whose signals ultimately lead to visual perception. Between cloudy nights and sunny days, the retina must combat the trillion-fold change in mean light intensity to successfully convey visual information. Critically, the nature of both signal and noise in RGC populations is altered across this broad range of light levels, creating a rich problem of how visual messages are encoded by the retina and transmitted to the brain. This thesis addresses these topics using large-scale multielectrode array recordings of RGC populations in different light conditions. In Chapter 2, I characterize how retinal signaling is altered over a wide range of light intensities. Chapter 3 investigates how adaptation impacts visual encoding of different RGC types. My results suggest that although retinal computations change substantially over light conditions, there are some elements of visual encoding that are invariant to light adaptation. Finally, Chapter 4 examines adaptation-induced changes in the structure of correlated activity and the subsequent impact on processing retinal output. The findings of this chapter clarify the nature of RGC responses crucial for downstream readout across light levels. Overall, this work identifies aspects of RGC activity that are important for encoding visual information and decoding retinal output from starlight to sunlight.