A Comparison of Local Field Potentials and Spiking Activity to Predict Perpetual Report During Bistable Visual Simulation

Author: Xing Wang

Primary Advisor:

Committee Members: H. Liang (co-author); Z. Wang (co-author); N.K. Logothetis (co-author); D.A. Leopold (co-author); A. Maier (co-author)

Masters thesis, The University of Texas School of Health Information Sciences at Houston.

Certain continuously moving objects appear to spontaneously reverse their motion direction (e.g., the illusion of structure-from-motion, SFM). The neuronal mechanisms underlying these perceptual fluctuations still remain elusive. Spiking activity from individual neurons in cortical middle temporal visual area (MT) has been shown to correlate to a certain degree with an animal’s perceptual report during stimulation with SFM and related paradigms of bistable perception. Similarly, certain frequency bands of the local field potentials (LFPs) can be used to predict these perceptual judgments (Maier et al., SFN 2005). Here we ask whether spiking activity or local field potentials are better correlated with the perceptual outcome of bistable stimulation. Two macaque monkeys were trained to report the perceived direction of motion in an SFM task while single-unit activity (SUA), multiunit activity (MUA) and LFPs were recorded from area MT. Using receiver operating characteristic (ROC) analysis, we compared the capability of each neural signal to predict the monkeys’ perceptual report on individual trials (choice probability, CP). Percept-related LFP changes were assessed by evaluating the power spectrum of the LFP as well as the spike-field coherence before and around the time of perceptual report. We found that both LFP power and spike-field coherence in the gamma band showed choice probabilities significantly greater than expected by chance. Lower frequency bands revealed smaller or insignificant values, thus revealing reduced coupling with the outcome of perceptual analysis. Choice probability of LFP gamma band and above (>50 Hz) was similar to that of the spiking activity measured in SUA and MUA on the same electrodes while the non-filtered LFP (standard LFP) performed worse than spiking activities. These results suggest that gamma band and above (>50 Hz) of the LFP in area MT reflects the perceptual state of an animal, to a similar degree compared to its spiking activity.