Decoding of attentional state using high-frequency local field potential is as accurate as using spikes

Local field potentials (LFPs) in visual cortex are reliably modulated when the subjects focus of attention is cued into versus out of the receptive field of the recorded sites, similar to modulation of spiking activity. However, human psychophysics studies have used an additional attention condition, neutral cueing, for decades. The effect of neutral cueing on spiking responses was examined recently and found to be intermediate between cued and uncued conditions. However, whether LFPs are also precise enough to represent graded states of attention is unknown. We found that LFPs during neutral cueing were intermediate between cued and uncued conditions, and, for a single electrode, attention was more discriminable using high frequency (>30 Hz) LFP power than spikes. Surprisingly, spikes did not outperform LFPs even when discriminability was computed using multiple electrodes. These results constrain the spatial scale attention operates over and highlight the usefulness of LFPs in studying attention.