neuronal coding in the retina and fixational eye movements
DESCRIPTION
Neuronal Coding in the Retina and Fixational Eye Movements. Christian Mendl Tim Gollisch Lab. Friday Seminar Talk November 6, 2009. Outline. Experimental setup Review of fixational eye movements Research questions and strategy A look at the observed data - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/1.jpg)
Neuronal Coding in the Retinaand Fixational Eye Movements
Friday Seminar TalkNovember 6, 2009
Christian Mendl Tim Gollisch Lab
![Page 2: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/2.jpg)
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
![Page 3: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/3.jpg)
ganglion cells
Experimental Setup
![Page 4: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/4.jpg)
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)
![Page 5: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/5.jpg)
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)
![Page 6: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/6.jpg)
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?
![Page 7: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/7.jpg)
Research Strategy
Concrete task: based on spike responses, discriminate 5 different angles
![Page 8: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/8.jpg)
Observed Data
stimulus period: 800 ms
![Page 9: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/9.jpg)
Spike Timing Cross-Correlations
![Page 10: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/10.jpg)
Spike Timing Cross-Correlations II
stimulus period
![Page 11: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/11.jpg)
Encoding the Spike Train
stimulus-locked binning
unlockedbinning
Encoding spike patterns
→ observer knows the stimulus phase
![Page 12: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/12.jpg)
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
![Page 13: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/13.jpg)
Mutual Information
unlocked binningstimulus-locked binning
individual cells
cell pairs
![Page 14: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/14.jpg)
Population Code: Synergy
Synergy versus mutual information for several recordings
unlocked binningstimulus-locked binning
![Page 15: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/15.jpg)
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
![Page 16: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/16.jpg)
Outlook
• Effect of shorter stimulus periods and smaller amplitudes?
• Try different decoding stategies: optimal patterns, bin sizes?
![Page 17: Neuronal Coding in the Retina and Fixational Eye Movements](https://reader036.vdocuments.mx/reader036/viewer/2022062501/568164c2550346895dd6d49f/html5/thumbnails/17.jpg)
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