Analysis of Perisaccadic Field Potentials in the Occipitotemporal Pathway during Active Vision
Eye movement potentials (EMPs) associated with saccades appear in both subcortical and cortical structures of the primate visual system. In this study, EMPs are recorded across sites in the occipitotemporal (OT) pathway of monkeys performing a pattern-recognition task. We characterize pair recordings of saccade-triggered local field potentials (LFPs) in early extrastriate and inferotemporal regions of the ventral visual pathway using time-frequency spectrograms. Parameters of the spectrograms, including the centroids of identified regions of interest in the time-frequency plane, are extracted and analyzed. Comparisons among the distributions of the extracted parameters reveal that the occipital lobe EMPs are largely postsaccadic events centered at 100 ms after saccade onset that are typically not influenced in timing by the direction of the saccade or the appearance of a stimulus transient appearing either before or after the saccade. The occipital lobe EMPs also demonstrate a significant shift in frequency content during their transient time course that is influenced, in a few cases, by saccade direction. Temporal lobe EMPs, on the other hand, may be centered in either the presaccadic or postsaccadic intervals; the time of their appearance is significantly influenced by the direction of the saccade. Temporal lobe EMPs demonstrate less frequency modulation than those recorded in the occipital lobe. The prevalence of EMPs in the OT pathway suggests that many cortical regions important for pattern recognition can be modulated by saccades. The timing and frequency characteristics of these signals suggest that the nature of this perisaccadic modulation varies across the cortex.