Pre-saccadic Preview Shapes Post-Saccadic Processing More Where Perception is Poor

Liu, Xiaoyi; Melcher, David; Carrasco, Marisa; Hanning, Nina M.

doi:10.1101/2023.05.18.541028

Cited by 3 publications

References 100 publications

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Presaccadic attention depends on eye movement direction and is related to V1 cortical magnification

Hanning

Himmelberg

Carrasco

2022

Preprint

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With every saccadic eye movement, humans bring new information into their fovea to be processed with high visual acuity. Notably, perception is enhanced already before a relevant item is foveated: During saccade preparation, presaccadic attention shifts to the upcoming fixation location, which can be measured via behavioral correlates such as enhanced visual performance or modulations of sensory feature tuning. The coupling between saccadic eye movements and attention is assumed to be robust and mandatory, and considered a mechanism facilitating the integration of pre- and post-saccadic information. However, until recently it had not been investigated as a function of saccade direction. Here, we measured contrast response functions during fixation and saccade preparation and found that the pronounced response gain benefit typically elicited by presaccadic attention is selectively lacking before upward saccades, some observers even showed a cost. Individual observers' sensitivity before upward saccades was negatively related to their amount of surface area in primary visual cortex representing the saccade target, suggesting a potential compensatory mechanism that optimizes the use of the limited neural resources processing the upper visual field. Our results raise the question how perceptual continuity is achieved and upward saccades can be accurately targeted despite the lack of (theoretically required) presaccadic attention.

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Presaccadic attention depends on eye movement direction and is related to V1 cortical magnification

Hanning

Himmelberg

Carrasco

2022

Preprint

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Saccade execution increases the preview effect with faces: An EEG and eye-tracking coregistration study

Huber-Huber,

Melcher

2023

Atten Percept Psychophys

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Under naturalistic viewing conditions, humans conduct about three to four saccadic eye movements per second. These dynamics imply that in real life, humans rarely see something completely new; there is usually a preview of the upcoming foveal input from extrafoveal regions of the visual field. In line with results from the field of reading research, we have shown with EEG and eye-tracking coregistration that an extrafoveal preview also affects postsaccadic visual object processing and facilitates discrimination. Here, we ask whether this preview effect in the fixation-locked N170, and in manual responses to the postsaccadic target face (tilt discrimination), requires saccade execution. Participants performed a gaze-contingent experiment in which extrafoveal face images could change their orientation during a saccade directed to them. In a control block, participants maintained stable gaze throughout the experiment and the extrafoveal face reappeared foveally after a simulated saccade latency. Compared with this no-saccade condition, the neural and the behavioral preview effects were much larger in the saccade condition. We also found shorter first fixation durations after an invalid preview, which is in contrast to reading studies. We interpret the increased preview effect under saccade execution as the result of the additional sensorimotor processes that come with gaze behavior compared with visual perception under stable fixation. In addition, our findings call into question whether EEG studies with fixed gaze capture key properties and dynamics of active, natural vision.

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An early effect of the parafoveal preview on post-saccadic processing of English words

Melcher,

Alaberkyan,

Anastasaki

et al. 2024

Atten Percept Psychophys

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A key aspect of efficient visual processing is to use current and previous information to make predictions about what we will see next. In natural viewing, and when looking at words, there is typically an indication of forthcoming visual information from extrafoveal areas of the visual field before we make an eye movement to an object or word of interest. This “preview effect” has been studied for many years in the word reading literature and, more recently, in object perception. Here, we integrated methods from word recognition and object perception to investigate the timing of the preview on neural measures of word recognition. Through a combined use of EEG and eye-tracking, a group of multilingual participants took part in a gaze-contingent, single-shot saccade experiment in which words appeared in their parafoveal visual field. In valid preview trials, the same word was presented during the preview and after the saccade, while in the invalid condition, the saccade target was a number string that turned into a word during the saccade. As hypothesized, the valid preview greatly reduced the fixation-related evoked response. Interestingly, multivariate decoding analyses revealed much earlier preview effects than previously reported for words, and individual decoding performance correlated with participant reading scores. These results demonstrate that a parafoveal preview can influence relatively early aspects of post-saccadic word processing and help to resolve some discrepancies between the word and object literatures.

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Pre-saccadic Preview Shapes Post-Saccadic Processing More Where Perception is Poor

Cited by 3 publications

References 100 publications

Presaccadic attention depends on eye movement direction and is related to V1 cortical magnification

Presaccadic attention depends on eye movement direction and is related to V1 cortical magnification

Saccade execution increases the preview effect with faces: An EEG and eye-tracking coregistration study

An early effect of the parafoveal preview on post-saccadic processing of English words

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