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 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

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?

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

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)

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

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

Results: Experiment 2 Saccade condition: longest after-image persistence

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

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

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

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

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

Saccades and McCollough Effect: Preliminary Findings

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