Tuned thalamic excitation is amplified by visual cortical circuits.
Cortical neurons in thalamic recipient layers receive excitation from the thalamus and the cortex. The relative contribution of these two sources of excitation to sensory tuning is poorly understood. We optogenetically silenced the visual cortex of mice to isolate thalamic excitation onto layer 4 neurons during visual stimulation. Thalamic excitation contributed to a third of the total excitation and was organized in spatially offset, yet overlapping, ON and OFF receptive fields. This receptive field structure predicted the orientation tuning of thalamic excitation. Finally, both thalamic and total excitation were similarly tuned to orientation and direction and had the same temporal phase relationship to the visual stimulus. Our results indicate that tuning of thalamic excitation is unlikely to be imparted by direction- or orientation-selective thalamic neurons and that a principal role of cortical circuits is to amplify tuned thalamic excitation.
Neurosciences Graduate Program, University of California San Diego, La Jolla, California, USA. anthony.d.lien@gmail.com
Anthony D
AD
Lien
Massimo
M
Scanziani
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001931:Brain Mapping; D000075402:Channelrhodopsins; D004558:Electric Stimulation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008959:Models, Neurological; D009415:Nerve Net / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D062308:Optogenetics; D009949:Orientation / Q000502:physiology*; D010320:Parvalbumins / Q000235:genetics / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D013788:Thalamus / Q000502:physiology*; D014161:Transduction, Genetic; D014793:Visual Cortex / Q000166:cytology* / Q000378:metabolism; D014794:Visual Fields; D014795:Visual Pathways / Q000502:physiology*
D000075402:Channelrhodopsins; D010320:Parvalbumins