2nd TAC Meeting
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Transcript of 2nd TAC Meeting
2nd TAC Meeting
Christian B. MendlTim Gollisch Lab
Neuronal Coding in the Retinaand 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 Typesa) 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 Latencytime 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 ofoff-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