title: Discrete states of attention during active visual fixation revealed by Markovian analysis of the time series of intrusive saccades.
abstract: The frequency of intrusive saccades during maintenance of active visual fixation has been used as a measure of sustained visual attention in studies of healthy subjects as well as of neuropsychiatric patient populations. In this study, the mechanism that generates intrusive saccades during active visual fixation was investigated in a population of young healthy men performing three sustained fixation tasks (fixation to a visual target, fixation to a visual target with visual distracters, and fixation straight ahead in the dark). Markov Chain modeling of inter-saccade intervals (ISIs) was utilized. First- and second-order Markov modeling provided indications for the existence of a non-random pattern in the production of intrusive saccades. Accordingly, the system of intrusive saccade generation may operate in two "attractor" states, one in which intrusive saccades occur at short consecutive ISIs and another in which intrusive saccades occur at long consecutive ISIs. These states might correspond to two distinct states of the attention system, one of low focused - high distractibility and another of high focused - low distractibility, such as those proposed in the adaptive gain theory for the control of attention by the noradrenergic system in the brain. To the authors knowledge, this is the first time that Markov Chain modeling has been applied to the analysis of the ISIs of intrusive saccades.
authors.affiliation: School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytexneiou, GR-15780 Zografou, Athens, Greece.
authors.forename: Alexandra I
authors.initials: AI
authors.lastname: Korda
authors.affiliation: School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytexneiou, GR-15780 Zografou, Athens, Greece.
authors.forename: Mariniki
authors.initials: M
authors.lastname: Koliaraki
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Agiou Spyridonos Street, GR-122 43 Egaleo, Athens, Greece.
authors.forename: Pantelis A
authors.initials: PA
authors.lastname: Asvestas
authors.affiliation: School of Electrical and Computer Engineering, National Technical University of Athens, 9 Iroon Polytexneiou, GR-15780 Zografou, Athens, Greece.
authors.forename: George K
authors.initials: GK
authors.lastname: Matsopoulos
authors.affiliation: Department of Biomedical Engineering, Technological Educational Institute of Athens, Agiou Spyridonos Street, GR-122 43 Egaleo, Athens, Greece.
authors.forename: Errikos M
authors.initials: EM
authors.lastname: Ventouras
authors.affiliation: Department of Psychiatry, Eginition Hospital, National and Kapodistrian University of Athens, 72 V. Sofias Avenue, GR-11528 Athens, Greece.
authors.forename: Periklis Y
authors.initials: PY
authors.lastname: Ktonas
authors.affiliation: Laboratory of Sensorimotor Control, University Mental Health Research Institute, 2 Soranou Efesiou Street, GR-11527 Papagou, Athens, Greece; Department of Psychiatry, Eginition Hospital, National and Kapodistrian University of Athens, 72 V. Sofias Avenue, GR-11528 Athens, Greece. Electronic address: smyrnis@med.uoa.gr.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Smyrnis
mesh_terms: D000293:Adolescent; D001288:Attention; D053483:Eye Movement Measurements; D005403:Fixation, Ocular; D006801:Humans; D008297:Male; D008390:Markov Chains; D008954:Models, Biological; D008960:Models, Psychological; D012438:Saccades; D055815:Young Adult
keywords: Markov chains; attractors; oculomotor; saccades; sustained attention; time-series