Spatial Organization of Neuronal Population Responses in Layer 2/3 of Rat Barrel Cortex. Jason N. D. Kerr, Christiaan P. J. de Kock, David S. Greenberg, Randy M. Bruno, Bert Sakmann, and Fritjof Helmchen. Take Home Points:. 1. Sparse spiking, no precise patterns.
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Spatial Organization of Neuronal Population Responses in
Layer 2/3 of Rat Barrel Cortex
Jason N. D. Kerr,Christiaan P. J. de Kock, David S. Greenberg, Randy M. Bruno,Bert Sakmann,and Fritjof Helmchen
Take Home Points:
1. Sparse spiking, no precise patterns.
2. Spatially organized probalistic spiking patterns.
3. Position Not related direction sensitivity (unlike afferents)
4. Population coding: Each feature many neurons.
Each neuron several features.
How much information two things share.
. . . . ?
A measure of how knowledge about one thing reduces your uncertainty about another thing.
~ a more sophisticated correlation.
Large single cell variability.
Sparse and short-lived patterns
BUT could have an unambiguous pattern,
but requires many neurons.
(Think sample size)
Development of spatial maps of neural activity.
– normally impossible with extracellular recording.
1: Woolsey and Van der Loos, 1970
Location of all cells
Single-cell and single-spike resolution.
Skull exposed, optical imaging while stimulating whisker.
Patch-clamp recordings – visually targeted.
Random whisker deflected for 500ms. Interstim ~3-6 sec
Cortex sectioned and area of WB determined.
….. Then a significant variety of analysis.
Layout & Identification
Deflection transients similar to spontaneous ones.
Electrical and microscopy produced similar results.
Question: Spatial organization?
Conclusion: (1) Depends on distance from BCC
(2) Highly variable
(3) For both onset & offset
(4) Highly significant topology.
(5) Offset ~ onset, but smaller.
(6) Spontaneous: all similar.
Tuning amount varied by individual.
Little individual direction tuning.
Tuning corrected for
No spatial organization for directional tuning.
Question: Sparse/Dense responses?
(1) Varies trial-to-trial
(2) Varies greatly between cells.
(3) Onset-Offset active cells may vary.
Fraction active by location:
Stimulus – different.
Spontaneous – similar.
Assuming independence does not match the data.
Subsets activated not consistent trial-to-trial.
Correlations present in spontaneous,
but increased with stimulus.
Distance between neurons means little.
Distance from BCC significant meaning.
For both spontaneous and stimulus.
“During sensory stimulation, neighboring neurons may be bound together by common inputs.”
Question: Is effect of distance to BCC on correlation a result of pairs in the BCC being packed closely?
Stimulus detection always > false positive.
Classification accuracy improves with population size considered.
% small errors increased with size.
% large errors decreased with size.
Spatially organized – but probalistically
Correlated spiking, but variant
No discrete subpopulations observed.