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Saccades actively maintain perceptual continuity

Saccades actively maintain perceptual continuity. John Ross & Anna Ma-Wyatt. Overview. Introduction Methods Results Discussion Critique joeLAB Preliminary Findings. Introduction. 2 (opposing) views on saccades and perceptual continuity: Saccades hinder perceptual continuity

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Saccades actively maintain perceptual continuity

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  1. Saccades actively maintain perceptual continuity John Ross & Anna Ma-Wyatt

  2. Overview • Introduction • Methods • Results • Discussion • Critique • joeLAB Preliminary Findings

  3. Introduction • 2 (opposing) views on saccades and perceptual continuity: • Saccades hinder perceptual continuity • Suppression of magnocellular pathway • Compression of perceived object position • Saccades help perceptual continuity • Memory for scenes built up over time across saccades • Overlap between programming an eye movement and deployment of attention in LIP

  4. Introduction • Purpose: To examine the question of whether saccades help or hinder perceptual continuity • Experiment 1: Do saccades help or hinder perception of immediately past perceptual states? • Experiment 2: Do saccades help or hinder learned associations?

  5. Methods: Experiment 1 • 3 bistable ambiguous stimuli Necker Cube Binocular rivalry Glass Line

  6. Methods: Experiment 1 • 3 conditions 1. Continuous 2. Intermittent 3. Saccade Fixate on cube (5s)  Cube disappears  Fixate on same spot (5s) Fixate Fixate on cube (5s)  Saccade  Fixate on peripheral target (5s)

  7. Results: Experiment 1 • Saccade condition: shortest state duration (most rapid reversal rate) • Intermittent condition: longest state duration

  8. Methods: Experiment 2 • McCollough Effect • 50s adaptation period; 5s alternation • Presentation of the 3 conditions of Exp. 1 (continuous, intermittent, saccade) while viewing test stimulus

  9. Results: Experiment 2 • Saccade condition: longest after-image persistence

  10. Results Summary • Experiment 1 state duration for ambiguous stimuli: Intermittent > Continuous > Saccade • Experiment 2 after-image duration for McCollough effect: Saccade > Intermittent > Continuous

  11. Discussion • Experiment 1 results suggest that saccades erase immediately past perceptual states that could inhibit visual analysis • May be explained by parietal neurons that shift receptive fields before the eyes move for a saccade Duhamel et al., 1992

  12. Discussion • Experiment 2 results suggest that saccades strengthen learned associations (e.g. McCollough effect) • Re-establishing position in the world • Frontal eye field neurons may control influence of saccades on memory • maintain a memory of the visual world in the absence of visual stimulation (e.g. when making a saccade away from the test stimulus)

  13. Critique • “Eye movements were not monitored, as all subjects were experienced in making voluntary saccades…” • “…and maintaining fixation between saccades”

  14. Critique • 3 subjects; 3 trials per condition • Experiment 1: voluntary vs. involuntary changes of state?

  15. Saccades and McCollough Effect: Preliminary Findings

  16. Special thanks to: • Joint Oculomotor Experimentation Laboratory • NSERC • Centre for Vision Research • Celeste McCollough d

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