title: Beat-to-beat control of human optokinetic nystagmus slow phase durations.
abstract: This study provides the first clear evidence that the generation of optokinetic nystagmus fast phases (FPs) is a decision process that is influenced by performance of a concurrent disjunctive reaction time task (DRT). Ten subjects performed an auditory DRT during constant velocity optokinetic stimulation. Eye movements were measured in three dimensions with a magnetic search coil. Slow phase (SP) durations were defined as the interval between FPs. There were three main findings. Firstly, human optokinetic nystagmus SP durations are consistent with a model of a Gaussian basic interval generator (a type of biological clock), such that FPs can be triggered randomly at the end of a clock cycle (mean duration: 200-250 ms). Kolmogorov-Smirnov tests could not reject the modeled cumulative distribution for any data trials. Secondly, the FP need not be triggered at the end of a clock cycle, so that individual SP durations represent single or multiple clock cycles. Thirdly, the probability of generating a FP at the end of each interval generator cycle decreases significantly during performance of a DRT. These findings indicate that the alternation between SPs and FPs of optokinetic nystagmus is not purely reflexive. Rather, the triggering of the next FP is postponed more frequently if a recently presented DRT trial is pending action when the timing cycle expires. Hence, optokinetic nystagmus FPs show dual-task interference in a manner usually attributed to voluntary movements, including saccades.
  
  
  
  This study provides the first clear evidence that the generation of optokinetic nystagmus (OKN) fast phases is a decision process that is influenced by performance of a concurrent disjunctive reaction time task (DRT). The slow phase (SP) durations are consistent with a Gaussian basic interval generator and multiple interval SP durations occur more frequently in the presence of the DRT. Hence, OKN shows dual-task interference in a manner observed in voluntary movements, such as saccades.
authors.affiliation: Department of Otolaryngology, University of Pittsburgh, Pittsburgh, Pennsylvania; cbalaban@pitt.edu.|Departments of Neurobiology and Communication Sciences and Disorders, University of Pittsburgh, Pittsburgh, Pennsylvania.|Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania; and.
authors.forename: Carey D
authors.identifier: 0000-0002-3570-3844
authors.initials: CD
authors.lastname: Balaban
authors.affiliation: Department of Otolaryngology, University of Pittsburgh, Pittsburgh, Pennsylvania.|Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania; and.|Departments of Neurology and Physical Therapy, University of Pittsburgh, Pittsburgh, Pennsylvania.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Furman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D003657:Decision Making / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D017120:Nystagmus, Optokinetic / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology*; D018709:Statistics, Nonparametric; D013997:Time Factors; D055815:Young Adult
keywords: eye movements; interval generator; optokinetic nystagmus; slow phase duration