Download traditional approach

question:
how are neurons in the primary visual cortex encoding the visual scene?
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
• center-surround suppr
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
• center-surround suppr
• luminance, phase, etc
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
• center-surround suppr
• luminance, phase, etc
carandini 2004
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
• center-surround suppr
• luminance, phase, etc
question:
how are neurons in the primary visual cortex encoding the visual scene?
traditional approach:
• saturation
• cross-orientation suppr
• center-surround suppr
• luminance, phase, etc
gratings
natural images
2 important directions:
• characterize response of neural populations
• use natural stimuli
natural images
population coding, natural image stimulation:
Coding of Natural Scenes in Primary Visual Cortex
Weliky, Fiser, Hunt, Wagner
Neuron 37: 703-718, (2003).
the setup:
• anesthetized ferrets
• multi-electrode cortical surface recorder,
~40 sites
• flashed gratings, white squares, nat images
model for single cell response
CRF
white squares, reverse correlation
tuning curves
sine wave gratings
phase insensitive!
model for single cell response
CRF
white squares, reverse correlation
tuning curves
sine wave gratings
phase insensitive!
model:
band-pass filter, localized to CRF
output
correlation across all images, all recording sites
neurons
output
effect of surround modulation on prediction accuracy
restrict stimuli to CRF, compare to large-field
no effect on site-specific correlation
better predictions of pop response for large-field
both still badly predicted by local models
in their words,
“...we found no significant differences between recorded activity on the
surface compared to activity recorded with penetrating electrodes in layer 2/3.”
“Although the correlation between local contrast structure and cell responses is
modest at the level of individual cortical sites, a very simple population code,
derived from activity integrated across cortical sites having retinotopically
overlapping receptive fields, represents the local contrast structure of natural
scenes very well.”
“...our results demonstrate that by integrating across retino topically neighboring
recording sites, a significant degree of linearity is restored to the distributed
representation of natural scenes in primary visual cortex.”
“...our study is a restoration of this original classical model claiming that relevant
information for coding natural scenes is in the classical receptive field.”
problems
• anesthetized ferrets
• surface recording
• flashed images, not movies
• correlation, not percent variance explained
• predict “retinotopic map”, not neural activity or stimulus identity
• neurons coding “local contrast structure”?
• sparseness = efficiency?
• sparseness, efficiency measures for multiple cell recordings
references/future discussions
Vinje and Gallant (2002)
stimulation of nCRF with nat-vis movies makes firing sparse and efficient
David, Vinje, and Gallant (2004)
phase-sep fourier receptive fields are diff for gratings and nat-vis movies
Felsen, Touryan, and Dan (2005)
quad-pair model doesn’t predict response to naturilistic images
Guo, Robertson, Mahmoodi, and Young (2005)
surround of nat images modulates response; phase important
Smyth, Willmore, Baker, Thompson, Tolhurst (2003)
reverse corr invalid for nat stims; reg-inverse more correct, leads to similar
receptive fields for gratings and nat images
Kayser, Salazar, and Koenig (2003)
LFP and spiking show diff activity for broad-band stims, motion important
Guo, Robertson, Mahmoodi, Young (2005)
David, Vinje, Gallant (2004)
David, Vinje, Gallant (2004)