Corticothalamic feedback enhances stimulus response precision in the visual system.
There is a tightly coupled bidirectional interaction between visual cortex and visual thalamus [lateral geniculate nucleus (LGN)]. Using drifting sinusoidal grating stimuli, we compared the response of cells in the LGN with and without feedback from the visual cortex. Raster plots revealed a striking difference in the response pattern of cells with and without feedback. This difference was reflected in the results from computing vector sum plots and the ratio of zero harmonic to the fundamental harmonic of the fast Fourier transform (FFT) for these responses. The variability of responses assessed by using the Fano factor was also different for the two groups, with the cells without feedback showing higher variability. We examined the covariance of these measures between pairs of simultaneously recorded cells with and without feedback, and they were much more strongly positively correlated with feedback. We constructed orientation tuning curves from the central 5 ms in the raw cross-correlograms of the outputs of pairs of LGN cells, and these curves revealed much sharper tuning with feedback. We discuss the significance of these data for cortical function and suggest that the precision in stimulus-linked firing in the LGN appears as an emergent factor from the corticothalamic interaction.
Andolina
Ian M
IM
Department of Visual Science, Institute of Ophthalmology, 11-43 Bath Street, University College London, London EC1V 9EL, United Kingdom. i.andolina@ucl.ac.uk
Jones
Helen E
HE
Wang
Wei
W
Sillito
Adam M
AM
D000818:Animals; D002415:Cats; D003344:Cortical Synchronization; D004594:Electrophysiology; D025461:Feedback, Physiological; D005829:Geniculate Bodies / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D010775:Photic Stimulation; D016012:Poisson Distribution; D013997:Time Factors; D014785:Vision, Ocular; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014795:Visual Pathways; D014796:Visual Perception