Neuronal Coding in the Retina and Fixational Eye Movements Friday Seminar Talk November 6, 2009 Christian Mendl Tim Gollisch Lab
Feb 23, 2016
Neuronal Coding in the Retinaand Fixational Eye Movements
Friday Seminar TalkNovember 6, 2009
Christian Mendl Tim Gollisch Lab
Outline
• Experimental setup• Review of fixational eye movements• Research questions and strategy• A look at the observed data• Spike timing cross-correlations• Information theory: entropy, mutual
information, synergy, ...• Summary and outlook
ganglion cells
Experimental Setup
Fixational Eye Movements
source: Martinez-Conde laboratory
• Constant feature of normal vision
• Visual perception fading• Enhancement of spatial
resolutionRiggs LA and Ratliff F. The effects of counteracting the normal movements of the eye. Journal of the Optical Society of America (1952)
Ditchburn RW and Ginsborg BL. Vision with a stabilized retinal image. Nature (1952)
Meister M, Lagnado L and Baylor DA. Concerted signaling by retinal ganglion cells. Science (1995)
Martinez-Conde S et al. Microsaccades counteract visual fading during fixation. Neuron (2006)
Fixational Eye Movements IIEye movements of the turtle during fixation
• Periodic component at approximately 5 Hz• Imitating fixational eye movements →
retina better encoder• Neurons synchronize more
Greschner, Ammermüller et.al. Nature Neuroscience (2002)
Research Questions
• How can the brain discriminate between various stimuli in the context of fixational eye movements? Optimal decoding strategy?
• Synchronized responses of several retinal ganglion cells → population code?
Research Strategy
Concrete task: based on spike responses, discriminate 5 different angles
Observed Data
stimulus period: 800 ms
Spike Timing Cross-Correlations
Spike Timing Cross-Correlations II
stimulus period
Encoding the Spike Train
stimulus-locked binning
unlockedbinning
Encoding spike patterns
→ observer knows the stimulus phase
Information Theory
Mutual information Imutual
→ How much information („bits“) do the spikes contain about the stimulus
Synergy→ How much additional information is contained in the simultaneous activity of two cells as compared to the individual cells’ responses
Mutual Information
unlocked binningstimulus-locked binning
individual cells
cell pairs
Population Code: Synergy
Synergy versus mutual information for several recordings
unlocked binningstimulus-locked binning
Summary
• Fixational eye movements provide information about the stimulus
• If the brain uses individual cells, it needs to know the phase of the fixational eye movements
• For multiple cells, the phase information becomes less important since the cells are synergistic
Outlook
• Effect of shorter stimulus periods and smaller amplitudes?
• Try different decoding stategies: optimal patterns, bin sizes?
Acknowledgements
Tim Gollisch Lab• Tim Gollisch• Daniel Bölinger• Vidhya Krishnamoorthy
Thesis Advisory Board• Tim Gollisch• Erwin Frey (LMU)• Andreas Herz• Günther Zeck
Boehringer Ingelheim FondsFoundation for Basic Research in Medicine