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Eye movement statistics in humans are consistent with an optimal search strategy.

ABSTRACT: Most models of visual search are based on the intuition that humans choose fixation locations containing features that best match the features of the target. The optimal version of this feature-based strategy is what we term "maximum a posteriori (MAP) search." Alternatively, humans could choose fixations that maximize information gained about the target's location. We term this information-based strategy "ideal search." Here we compare eye movements of human, MAP, and ideal searchers in tasks where known targets are embedded at unknown locations within random backgrounds having the spectral characteristics of natural scenes. We find that both human and ideal searchers preferentially fixate locations in a donut-shaped region around the center of the circular search area, with a high density of fixations at top and bottom, while MAP searchers distribute their fixations more uniformly, with low density at top and bottom. Our results argue for a sophisticated search mechanism that maximizes the information collected across fixations.

SUBMITTER: Najemnik J

PROVIDER: S-EPMC2868380 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Eye movement statistics in humans are consistent with an optimal search strategy.

Najemnik Jiri J Geisler Wilson S WS

Journal of vision 20080307 3

Most models of visual search are based on the intuition that humans choose fixation locations containing features that best match the features of the target. The optimal version of this feature-based strategy is what we term "maximum a posteriori (MAP) search." Alternatively, humans could choose fixations that maximize information gained about the target's location. We term this information-based strategy "ideal search." Here we compare eye movements of human, MAP, and ideal searchers in tasks w ...[more]

PMID: 18484810

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Project description:BackgroundThe administration of dexmedetomidine is limited to highly monitored care settings because it is only available for use in humans as intravenous medication. An oral formulation of dexmedetomidine may broaden its use to all care settings. The authors investigated the effect of a capsule-based solid oral dosage formulation of dexmedetomidine on sleep polysomnography.MethodsThe authors performed a single-site, placebo-controlled, randomized, crossover, double-blind phase II study of a solid oral dosage formulation of dexmedetomidine (700 mcg; n = 15). The primary outcome was polysomnography sleep quality. Secondary outcomes included performance on the motor sequence task and psychomotor vigilance task administered to each subject at night and in the morning to assess motor memory consolidation and psychomotor function, respectively. Sleep questionnaires were also administered.ResultsOral dexmedetomidine increased the duration of non-rapid eye movement (non-REM) stage 2 sleep by 63 (95% CI, 19 to 107) min (P = 0.010) and decreased the duration of rapid eye movement (REM) sleep by 42 (5 to 78) min (P = 0.031). Overnight motor sequence task performance improved after placebo sleep (7.9%; P = 0.003) but not after oral dexmedetomidine-induced sleep (-0.8%; P = 0.900). In exploratory analyses, we found a positive correlation between spindle density during non-REM stage 2 sleep and improvement in the overnight test performance (Spearman rho = 0.57; P = 0.028; n = 15) for placebo but not oral dexmedetomidine (Spearman rho = 0.04; P = 0.899; n = 15). Group differences in overnight motor sequence task performance, psychomotor vigilance task metrics, and sleep questionnaires did not meet the threshold for statistical significance.ConclusionsThese results demonstrate that the nighttime administration of a solid oral dosage formulation of dexmedetomidine is associated with increased non-REM 2 sleep and decreased REM sleep. Spindle density during dexmedetomidine sleep was not associated with overnight improvement in the motor sequence task.Editor’s perspective

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Eye movement statistics in humans are consistent with an optimal search strategy.

Publications

Eye movement statistics in humans are consistent with an optimal search strategy.

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