MSGID: 1:317/3 642ba7e2   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Tiny eye movements are under a surprising degree of cognitive control   
      
      
     Date:   
         April 3, 2023   
     Source:   
         Weill Cornell Medicine   
     Summary:   
         A very subtle and seemingly random type of eye movement called   
         ocular drift can be influenced by prior knowledge of the expected   
         visual target, suggesting a surprising level of cognitive control   
         over the eyes, according to a new study.   
      
      
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   FULL STORY   
   ==========================================================================   
   A very subtle and seemingly random type of eye movement called ocular   
   drift can be influenced by prior knowledge of the expected visual target,   
   suggesting a surprising level of cognitive control over the eyes,   
   according to a study led by Weill Cornell Medicine neuroscientists.   
      
      
   ==========================================================================   
   The discovery, described Apr. 3 in Current Biology, adds to the scientific   
   understanding of how vision -- far from being a mere absorption of   
   incoming signals from the retina -- is controlled and directed by   
   cognitive processes.   
      
   "These eye movements are so tiny that we're not even conscious of them,   
   and yet our brains somehow can use the knowledge of the visual task to   
   control them," says study lead author Dr. Yen-Chu Lin, who carried out the   
   work as a Fred Plum Fellow in Systems Neurology and Neuroscience in the   
   Feil Family Brain and Mind Research Institute at Weill Cornell Medicine.   
      
   Dr. Lin works in the laboratory of study senior author Dr. Jonathan   
   Victor, the Fred Plum Professor of Neurology at Weill Cornell Medicine.   
      
   The study involved a close collaboration with the laboratory of   
   Dr. Michele Rucci, professor of brain and cognitive sciences and   
   neuroscience at the University of Rochester.   
      
   Neuroscientists have known for decades that information stored in   
   memory can strongly shape the processing of sensory inputs, including   
   the streams of visual data coming from the eyes. In other words, what   
   we see is influenced by what we expect to see or the requirements of   
   the task at hand.   
      
   Most studies of cognitive control over eye movement have covered more   
   obvious movements, such as the "saccade" movements in which the eyes   
   dart across large parts of the visual field. In the new study, Drs. Lin   
   and Victor and their colleagues examined ocular drift, tiny jitters of   
   the eye that occur even when gaze seems fixed. Ocular drifts are subtle   
   motions that shift a visual target on the retina by distances on the   
   order of a fraction of a millimeter or so - - across just a few dozen   
   photoreceptors (cones). They are thought to improve detection of small,   
   stationary details in a visual scene by scanning across them, effectively   
   converting spatial details into trains of visual signals in time.   
      
   Prior studies had suggested that ocular drift and other small-scale   
   "fixational eye movements" are under cognitive control only in a broad   
   sense -- for example, slowing when scanning across more finely detailed   
   scenes. In the new study, the researchers found evidence for a more   
   precise type of control.   
      
   Using sensitive equipment in Dr. Rucci's laboratory, the researchers   
   recorded ocular drifts in six volunteers who were asked to identify which   
   of a pair of letters (H vs. N, or E vs. F) was being shown to them on   
   a background of random visual noise. Based on computational modeling,   
   the scientists expected that optimal eye movements for discriminating   
   between letters would cross the key elements distinguishing the letters   
   at right angles. Thus, they hypothesized that a more precise cognitive   
   control, if it existed, would tend to direct ocular drift in both   
   vertical and oblique (lower left to upper right) directions for the H   
   vs. N discrimination, compared to more strictly vertical movements for   
   the E vs. F discrimination.   
      
   They found that the subjects' eye movements did indeed tend to follow   
   these patterns -- even in the 20 percent of trials in which the subjects,   
   though expecting to see a letter, were shown only noise. The latter   
   result showed that the cognitive control of ocular drift could be driven   
   solely by specific prior knowledge of the visual task, independently of   
   any incoming visual information.   
      
   "These results underscore the interrelationship between the sensory and   
   the motor parts of vision -- one really can't view them separately,"   
   said Dr.   
      
   Victor, who is also a professor of neuroscience in the Feil Family Brain   
   and Mind Research Institute at Weill Cornell.   
      
   He noted that the direction of fine eye movements is thought to come from   
   neurons in the brainstem, whereas the task knowledge presumably resides   
   in the upper brain: the cortex -- implying some kind of non-conscious   
   connection between them.   
      
   "The subjects are aware of the tasks they have to do, yet they don't   
   know that their eyes are executing these tiny movements, even when you   
   tell them," Dr.   
      
   Victor said.   
      
   Studies of this pathway, he added, could lead to better insights not only   
   into the neuroscience of vision, but possibly also visual disorders --   
   which traditionally have been seen as disorders of the retina or sensory   
   processing within the brain.   
      
   "What our findings suggest is that visual disorders may sometimes have a   
   motor component too, since optimal vision depends on the brain's ability   
   to execute these very tiny movements," Dr. Victor said.   
      
       * RELATED_TOPICS   
             o Mind_&_Brain   
                   # Intelligence # Perception # Brain-Computer_Interfaces   
                   # Neuroscience # Behavior # Psychology # Dementia #   
                   Brain_Injury   
       * RELATED_TERMS   
             o Dominant_eye_in_vision o Eye o Cognition o Animal_cognition   
             o Bitemporal_hemianopsia o Passive-aggressive_behavior o   
             Visual_perception o Cognitive_neuroscience   
      
   ==========================================================================   
   Story Source: Materials provided by Weill_Cornell_Medicine. Note:   
   Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Yen-Chu Lin, Janis Intoy, Ashley M. Clark, Michele Rucci,   
      Jonathan D.   
      
         Victor. Cognitive influences on fixational eye movements. Current   
         Biology, 2023; DOI: 10.1016/j.cub.2023.03.026   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230403133521.htm   
      
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