2nd TAC Meeting Christian B. Mendl Tim Gollisch Lab Neuronal Coding in the Retina and Fixational Eye Movements Neuronal Coding in the Retina and Fixational Eye Movements April 22, 2010

Outline Review of last TAC meeting Informative spike response features Latency coding by cell pairs Modeling response features Outlook

Review of Last TAC Meeting Fixational eye movements, microsaccades Counteract visual perception fading Enhancement of spatial resolution Last TAC meeting: information theory: mutual information, synergy → use as screening tool To-do: – stimulus variation: grating instead of border – neuronal model building – decoding strategies

Informative Spike Response Features Observed spike responses of a single cell

Various Response Types a)b) d)c)

Informative Spike Features (cont) Observed spike responses of a single cell

Informative Spike Responses: Number of Spikes/Trial

Informative Spike Responses: Internal Structure ISI (inter-spike-interval)

Informative Spike Responses: Latency

Latency Coding by Cell Pairs Latency emerges as most informative spike response feature Timing reference? (Brain doesn’t know stimulus onset) → Need several cells

Cell Pairs: Experimental Data

Relative Latency time intervals accessible to readout by higher brain regions

Cell Pairs: Latency Scatter Plot K-means clustering: relative weight of off- diagonal elements: 19.1%

Global Drift Correction

Drift-Corrected Latency Scatter Plot K-means clustering: relative weight of off-diagonal elements: 9.6%

Latency Correlations Observation: global latency drift leads to (artificial) correlations, can correct for that Question: cells internally interacting on short-term scale? → Compare spikes shuffled by one trial

Latency Correlations (cont) shuffled version: no correlations

Latency Correlation Statistics

Conclusions Latency Coding Use latency instead of spike count and inter-spike- interval High information content in latency data from two cells Correlations might improve coding

Comparison with LN Models

LN Models (cont)

Conclusions Modeling Qualitative agreement But still much room for improvement, latency data on 10 ms scale not reproduced Gain control might be able to reproduce experimental spike histogram

Outlook Fixational eye movements have been reported in Salamander But precise quantification still missing → Search coil setup