Exploring Saccadic Eye Movement

By Fatin Chowdhury ‘19

saccade photo.jpeg

Figure 1. Saccadic eye movement was examined in a recent experiment.

The nuances of eye movements form an overlooked part of human vision. Dr. Grace Edwards at Istituto Italiano di Technologia in Italy examined the effect of peripheral information near a saccade target. Saccading is the completion of rapid eye movement by healthy human eyes while being fixated on differing spatial points. Edwards hypothesized that the neural interpretation of a postsaccadic visual stimulus would be reliant upon the presaccadic visual stimulus in terms of accuracy and/or latency. The researchers proposed that information transfer would enhance accuracy, decrease latency, or achieve both outcomes.

Electroencephalography (EEG) technology was utilized, with female and male participants looking and saccading at a face or house, the image of which was stable, altered, or removed as the saccade occurred. Data examination was carried out with multivariate pattern analysis (MVPA), which detected and analyzed certain neuronal signals. ANOVA and paired t-tests were utilized for statistical analyses; one-sample t-tests were also used, but after data was collected to observe whether participants found that the presented images were identical.

A changed target was found to yield a larger time span of visual processing, and the nature of the stimulus was found to influence the latent period of information processing after saccade completion. Information was eventually interpreted at a new location in the retina, the cone-dense fovea. The researchers also found that the distinguishing neural characteristic for saccade target stimuli was observed when the stimulus applied during a saccade was displaced. The researchers suggested that a peripheral stimulus applied before a saccade was interpreted across the duration of a saccade.

The study was limited by a small sample size, as only fourteen participants were included and three were omitted from analysis. Nevertheless, the researchers suggested that presaccadic information influenced postsaccadic information as hypothesized, and further research could examine eye movement within the context of this type of processing.

References

  1. G. Edwards, et al., Decoding trans-saccadic memory. The Journal of Neuroscience 38, 1114 -1123 (2018). doi: 10.1523/JNEUROSCI.0854-17.2017
  2. Image retrieved from: https://unsplash.com/photos/KD8jKVdCFoQ
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