title: Preparatory activations across a distributed cortical network determine production of express saccades in humans.
abstract: Reaction time variability across trials to identical stimuli may arise from both ongoing and transient neural processes occurring before trial onset. These processes were examined with dense-array EEG as humans completed saccades in a "gap" paradigm known to elicit bimodal variability in response times, including separate populations of "express" and regular reaction time saccades. Results indicated that express reaction time trials could be differentiated from regular reaction time trials by (1) pretrial phase synchrony of occipital cortex oscillations in the 8-9 Hz (low alpha) frequency range (lower phase synchrony preceding express trials), (2) subsequent mid- and late-gap period cortical activities across a distributed occipital-parietal network (stronger activations preceding express trials), and (3) posttarget parietal activations locked to response generation (weaker preceding express trials). A post hoc path analysis suggested that the observed cortical activations leading to express saccades are best understood as an interdependent chain of events that affect express saccade production. These results highlight the importance of a distributed posterior cortical network, particularly in right hemisphere, that prepares the saccade system for rapid responding.
authors.affiliation: Department of Psychology, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Jordan P
authors.initials: JP
authors.lastname: Hamm
authors.forename: Kara A
authors.initials: KA
authors.lastname: Dyckman
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Ethridge
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: McDowell
authors.forename: Brett A
authors.initials: BA
authors.lastname: Clementz
mesh_terms: D000704:Analysis of Variance; D001931:Brain Mapping; D016009:Chi-Square Distribution; D004569:Electroencephalography / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008954:Models, Biological; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult