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Physiology and Psychophysics of Eye Movements

Physiology and Psychophysics of Eye Movements. Muscles and (cranial) nerves 2. Classes of eye movements/oculomotor behaviors 3. Saccadic Eye Movements, metrics and factoids 4. Brainstem control of saccadic eye movements 5. Superior Colliculus and cortical control of saccades

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Physiology and Psychophysics of Eye Movements

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  1. Physiology and Psychophysics of Eye Movements • Muscles and (cranial) nerves • 2. Classes of eye movements/oculomotor behaviors • 3. Saccadic Eye Movements, metrics and factoids • 4. Brainstem control of saccadic eye movements • 5. Superior Colliculus and cortical control of saccades • 6. Saccades and Visual Perception

  2. ExtraocularMuscles: three complimentary pair

  3. Measuring Eye Movements/Position Scleral search coil Infrared Eye Tracking magnetic field (2 axes) scleral coil Temporal resolution: analog Spatial resolution: <0.1 deg. Temporal resolution: video frame rate, <500 Hz Spatial resolution: <0.25 deg. older methods: electro-oculogram (EOG), coil contacts, suction caps of Yarbus

  4. Adapted from Yarbus (1967)

  5. Classes of Eye Movements • Vestibulo-Ocular (VOR): • Hold images of the seen world steady on the retina during brief head • movements (angular or translational). • -very short latency (<15 ms) because signal is from inner ear. • 2. Visual Fixation: • Holds image of a stationary image on the fovea • 3. Optokinetic: • Hold images of the seen world steady on the retina during prolonged head • movements. • 4. Smooth pursuit: • Holds the image of a small (moving) target on the fovea. • -cannot move gaze smoothly without stimulus • 5. Vergence: • Moves the eyes in opposite directions so that images of a single object are • placed or held simultaneously on both foveas. • -2 signals: disparity, accommodative • 6. Saccadic Eye Movements: • Bring objects of interest onto fovea

  6. Combinations of eye movement types. Optokinetic Nystagmus (OKN): Slow phase-optokinetic Quick phase-saccadic Saccades and pursuit: Pursuit pre- and post- saccadic Left eye Saccades and vergence: Vergence with a saccade is much faster Right eye Vergence Angle Without saccade With saccade time

  7. Saccadic Eye Movements (‘saccades’) Subtypes often referred to: 1. Volitional (‘purposive’) -predictive, anticipatory -memory-guided -antisaccades 2. Reflexive 3. Express saccades 4. Spontaneous 5. Quick phase of nystagmus

  8. Velocity, Duration and the ‘Main Sequence’ Visually Guided Saccades Deviations from main sequence: -saccades in complete darkness -saccades to auditory stimuli -saccades to remembered targets -saccades made in the opposite direction (antisaccades)

  9. [abducens, trochlear, om nucleus] [cerebellum, brainstem] [pprf, mrf] [dorsal raphe]

  10. Major Pathways for Saccadic Eye Movements in the Monkey

  11. Tuning of SC burst neuron to direction and amplitude of saccades Sparks and Mays, 1980

  12. ‘Movement field’ of Superior Colliculus neuron

  13. Map of Stimulation Evoked Saccades Rostral Caudal amplitude elevation

  14. Enhancement of Superior Colliculus Visual Responses and the Need to Dissociate Behavioral Components Passive fixation Saccade to RF target Saccade to Control target

  15. Striate cortex (V1) Extrastriate cortex (e.g. V4, MT) Parietal cortex (e.g. LIP) Frontal Eye Field Inferior Pulvinar Brainstem Saccade generator Dorsal lateral geniculate nucleus (dLGN) Medio-dorsal thalamus Major Connections of the Superior Colliculus SC Retina Superficial Layers Intermediate and Deep Layers

  16. Tasks used to characterize saccade-related activity 1. step task (simultaneous, overlap, gap) fixation point saccade target eye position (h) time

  17. Tasks used to characterize saccade-related activity 2. visually-guided, delayed saccade task fixation point saccade target eye position (h) time

  18. Tasks used to characterize saccade-related activity 3. memory-guided, delayed saccade task fixation point saccade target eye position (h) time

  19. Tasks used to characterize saccade-related activity 4. anti-saccade task fixation point saccade target eye position (h) time

  20. Visual and Motor Related Properties of Cells in the Superior Colliculus SC Superficial Layers: Visual Receptive Fields, Some enhanced Visual Responses, but no Presaccadic (motor) bursts; ‘visual’ cells Intermediate: Deep Layers Visual Receptive Fields and Presaccadic Bursts before saccades to ‘movement field’; ‘visuomotor cells’, ‘visually-triggered motor cells’ No visual RFs, just movement fields, Presaccadic burst gets earlier as you go deeper

  21. Major Pathways for Saccadic Eye Movements in the Monkey (SEF) Lateral Intraparietal Area (LIP) (FEF)

  22. Continuum of Visual and Motor Responses in the FEF

  23. Microstimulation of the Frontal Eye Field

  24. Arcuate post. ant. Functional Organization of Macaque FEF

  25. Stimulation-Evoked Smooth Pursuit Movements

  26. Stimulation-Evoked Vergence Movements

  27. Cortical Connections of the FEF: organized and reciprocal connections with ‘dorsal’ and ‘ventral’ visual pathways

  28. Major Pathways for Saccadic Eye Movements in the Monkey (SEF) Lateral Intraparietal Area (LIP) (FEF)

  29. Lateral Intraparietal Area (LIP): visual, saccade-related and mnemonic responses

  30. Incidence of ‘light-sensitive’, ‘saccade-coincident’ and ‘memory’ activity in LIP

  31. Microstimulation of Parietal Cortex: fixed and ‘modified’ vector saccades

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