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Abstract:
Aims
We previously reported that the activity of primary visual cortex (V1) transmits information about complex naturalistic video stimuli in two distinct frequency bands: a range of low frequency fluctuations below 20 Hz, and a high frequency (50-150 Hz) gamma oscillation range, with each range carrying its own independent information about the visual stimuli [1]. Here we ask whether these independent frequency channels are generated in distinct cortical laminae.
Methods
We used laminar electrodes with 150 micron spacing spanning the whole cortical depth to record extracellular field potentials from the primary visual cortex of opiate-anaesthetised macaques during presentation of a 2 minute long Hollywood colour movie clip. We then computed the Current Source Density (CSD) for each trial. From the time-resolved power of the CSD in each trial, we estimated the mutual information that the power at each frequency carries about which section of the movie is being presented, and how much information there is in frequency bands about fine and coarse spatial changes in luminance.
Results and Conclusions
We found, across depth and frequency, two distinct regions carrying large amounts of independent information about the movie stimulus: the low frequency (up to 20Hz) band had high information at depths corresponding to layers 4-6, whereas the 50-150Hz band had high information in layers 1-3. This suggests that different laminae of cortical circuits generate independent information channels that code information in separate frequency ranges.
