Single unit activity (SUA) was extensively studied in the lateral geniculate nucleus (LGN) but less attention was paid to the analysis of the local field potentials (LFP). In the present study, we investigate how and to what extent LFP and SUA correlate with visual stimulus eccentricity. SUAs and LFPs recorded extracellularly from 52 electrode positions were analyzed. Both LFP and SUA recordings contained well defined time-segments, which correlated with stimulus eccentricity. The spectral analysis of the LFPs indicated that in addition to the phasic, short latency activity of the 20 Hz frequency band, a tonic, 2-10 Hz, elongated component was also present. The time-domain analysis of the phasic and tonic LFP segments revealed a non-linear decrease of the mean LFP amplitude. The frequency-domain investigation made it obvious that the low and high frequency components exhibit a spatially localized increase of the response, in contrast to the time-domain curve. Our results confirm that the local field potentials as a measure of the mesoscopic level neuronal activity provide additional information concerning the activity of neuronal populations, thus enhancing our present knowledge about the functional circuitry as the foundation of various neuronal processes.
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