The Neurology of Eye Movements – Part 2: Antisaccades

Looks like the opening to a Monty Python sketch, doesn’t it?  It’s actually a graphic depiction of the antisaccade task, which is given extensive treatment in the new edition of Leigh & Zee’s Neurology of Eye Movements.  Simply put, a patient fixating a target is instructed to make an eye movement in the direction opposite to the location in which a new stimulus appears.  It’s a form of inhibiting one’s impulse to look in the direction of something new.  Graham and Paula Peachey made reference to this in their article on neuro-developmental assessment and treatment for optomotor deficits, based on the work of Professor Burkhart Fischer.

Leigh & Zee

Although Leigh & Zee don’t reference Fischer or Peachey, they do have a nice discussion of Eye Movements in Autism Spectrum Disorder, noting that patients with ASD show increased errors and latencies on the antiscaccade task.  They cite ample evidence showing that deficits in executive control of saccades assessed with antisaccade and memory-guided saccade tasks are a feature of autism, implicating alterations in prefrontal systems.  Functional imaging shows reduced inhibition-related activation in bilateral frontal eye fields and dorsal anterior cingulate cortex, pointing to reduced functional connectivity between these regions.

Antisaccade therapy procedures are often done by having the patient look back toward the center fixation spot after making the saccade in the direction opposite that the new stimulus appears.  In one sense it’s a ocular motor (or optomotor) variant of Bob Sanet’s “Look/Ready/Touch/Back” procedure for the Space Fixator (see Tanner Gates’ Appendix A here for reference).  Functional neurology has bundled the anti saccade procedure as part of the Focus Builder App exercises.

As an aside, there are many applications of the “anti” paradigm involving inhibition of one’s initial impulse, or the resolving of incongruence.  This is famously the case in the Stroop Task which involves verbalizing the color rather than the spelling of a word.  I recall Arnie Sherman designing a variety of procedures in which the patient had to respond by doing the opposite action to the motor command.  For example, calling out directional arrows not as they are printed, but the direction they’d be facing if you rotated it 90 degrees.  Or Hart Chart saccades done in between beats of the metronome rather than on the beat.  To show ultimate flexibility, the patient might have to switch between the “pro” and the “anti” (challenging for many of the patients we work with), and this is the terminology used for saccades as well.

Prosaccade en antisaccade

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