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
Magnocellular pathway = sensitive to movement (V2 to MT/MST)
Compression of bridge scene when scene presented just before saccade onset

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)
FEF activated during initiation of eye movement– therefore possible interaction in which saccades affect memory

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