The Foreground Bias: Initial Scene Representations Across the Depth Plane

When you walk into a large room, you perceive visual information that is both close to you in depth and farther in the background. Here, we investigated how initial scene representations are affected by information across depth. We examined the role of background and foreground information on scene gist by using chimera scenes (images with a foreground and background from different scene categories). Across three experiments, we found a foreground bias: Information in the foreground initially had a strong influence on the interpretation of the scene. This bias persisted when the initial fixation position was on the scene background and when the task was changed to emphasize scene information. We concluded that the foreground bias arises from initial processing of scenes for understanding and suggests that scene information closer to the observer is initially prioritized. We discuss the implications for theories of scene and depth perception.

Decoding 3D spatial location across saccades in human visual cortex

Visual signals are initially processed as two-dimensional images on our retina, but we live in a 3D world. Depth information needs to be reconstructed from the 2D retinal images, using cues such as binocular disparity. But in daily life, we also make frequent, rapid eye movements, which alter the 2D retinal input. How do we achieve stable 3D perception across saccades? Using fMRI pattern analysis, we investigated how 3D spatial representations in human visual cortex are influenced by saccades. Participants viewed stimuli in four possible 3D locations, defined by 2D vertical position (above or below screen center) and depth position (in front of or behind central screen plane). We compared the amount of 2D and depth information in visual cortical regions during no-saccade blocks (stationary fixation) with that during saccade blocks (series of guided saccades). On no-saccade blocks, decoding of stimulus location was highly dependent on fixation position: in later visual areas we could decode both vertical and depth information across blocks that shared the same fixation position (as previously reported), but little vertical or depth information could be decoded across blocks with different fixation positions. Strikingly, the neural similarity patterns appeared tolerant to changes in fixation position during saccade blocks: despite the saccade-induced retinal and fixation changes, we could reliably decode both vertical and depth information. The findings suggest that representations of 3D spatial locations may become more tolerant of fixation positions during dynamic saccades, perhaps due to active remapping which may encourage more stable representations of the world.SignificanceThis study investigates two fundamental challenges for visual perception: how to preserve spatial information across frequent eye movements, and how to integrate binocular depth location with 2D location to form coherent 3D percepts. Aspects of these challenges have been studied in isolation, but surprisingly no studies have investigated them jointly to ask how 3D spatial representations in human visual cortex are influenced by saccades. Our fMRI pattern analysis findings highlight a potentially critical role of active, dynamic saccades on stabilizing 3D spatial representations in the brain, revealing that representations of 3D space may be modulated by eye position during sustained fixation, but could become tolerant of changes in eye position during active, dynamic saccades.

Outcomes in two patients with vocal fold palsy who underwent revision arytenoid adduction surgery

ObjectiveThis study investigated the position of adduction thread attachment, pulling direction and fixation position in revision arytenoid adduction surgery performed in two patients with left vocal fold palsy in whom satisfactory speech improvement had not been obtained by arytenoid adduction and type 1 thyroplasty.MethodsRevision arytenoid adduction surgery was performed with the vocal fold in the midline position in both cases. A type 1 thyroplasty procedure was subsequently added in one case because of worsened quality of speech following arytenoid adduction.Results and conclusionAlthough the arytenoid adduction procedure is conceptually well established, there is still room for debate concerning the actual surgical procedures used. The technique described in this report is effective, suggesting that it is worthy of recognition as an index procedure.

Accurate internal representation of eye position in saccade planning

Fixation position changes slightly after each blink (Lau & Maus, 2019). We investigated whether these changes affect subsequent saccades. We tested if the oculomotor system uses an internal representation of eye position to plan a saccade. Naïve participants (N = 12) made 10° visually-guided (VG) and memory-guided (MG) saccades to a dot target presented to the left or right of fixation. Participants blinked once (blink) or remained fixated (no-blink) before an auditory cue instructed them to saccade to the target. We hypothesized that if participants had access to an eye position signal at the onset of their saccade, blink-induced position shifts should be corrected for. The alternative hypothesis was that without such an internal eye position signal, blink-induced position shifts should correlate with landing positions. This was not the case either in VG or MG saccades. Saccades started more forward from fixation for MG than VG saccades and landed more backward of the target for MG than VG saccades. Blinking did not contribute to these positional differences. Instead, blinks enlarged both saccade amplitudes. MG amplitudes were also smaller than VG amplitudes. We found no correlation between starting and landing errors across saccades. Hence, start position changes did not influence saccade landing errors. Our results suggest that to plan accurate saccades, the oculomotor system uses an internal representation of eye position that is updated after each blink. Although blinking was introduced to increase eye position changes, it did not influence saccade starting nor landing positions.

The Foreground Bias: Initial Scene Representations across the Depth Plane

When you walk into a large room, you perceive visual information that is both close to you in depth and farther in the background. Here, we investigated how initial scene representations are affected by information across depth. We examined the role of background and foreground information on scene gist by using Chimera scenes (images with foreground and background from different scene categories). Across three experiments, we found a Foreground Bias in which foreground information initially had a strong influence on the interpretation of the scene. This bias persisted when the initial fixation position was on the scene background and when the task was changed to emphasize scene information. We conclude that the Foreground Bias arises from initial processing of scenes for understanding and suggests that scene information closer to the observer is initially prioritized. We discuss the implications for theories of scene and depth perception.

Eye movements, attention, and expert knowledge in the observation of Bharatanatyam dance

Previous research indicates that dance expertise affects eye-movement behaviour—dance experts tend to have faster saccades and more tightly clustered fixations than novices when observing dance, suggesting that experts are able to predict movements and process choreographic information more quickly. Relating to this, the present study aimed to explore (1) the effects of expertise on eye movements (as a proxy for attentional focus and the existence of movement-dance schemas) in Indian Bharatanatyam dance, and (2) narrative dance, which is an important component of Bharatanatyam. Fixation durations, dwell times, and fixation-position dispersions were recorded for novices and experts in Bharatanatyam (N = 22) while they observed videos of narrative and non-narrative Bharatanatyam dance. Consistent with previous research, experts had shorter fixation durations and more tightly clustered fixations than novices. Tighter clustering of fixations was also found for narrative dance versus non-narrative. Our results are discussed in relation to previous dance and eye-tracking research.

Prior expectation of objects in space is dependent on the direction of gaze

Many studies of multisensory spatial localization have shown that observers' responses are well-characterized by Bayesian inference, as localization judgments are influenced not only by the reliability of sensory encoding, but expectations about where things occur in space. Here, we investigate the frame of reference for the prior expectation of objects in space. Using an audiovisual localization task, we systematically manipulate fixation position and evaluate whether this prior is encoded in an eye-centered, head-centered, or hybrid frame of reference. Results show that in a majority of participants, this prior is encoded in an eye-centered frame of reference.