Microsaccade-induced prolongation of saccade latencies depends on microsaccade amplitude

Fixations consist of small movements including microsaccades, i.e., rapid flicks in eye position that replace the retinal image by up to 1 degree of visual angle. Recently, we showed in a delayed-saccade task (1) that the rate of microsaccades decreased in the course of saccade preparation and (2) that microsaccades occurring around the time of a go signal were associated with prolonged saccade latencies (Rolfs et al., 2006). A re-analysis of the same data set revealed a strong dependence of these findings on microsaccade amplitude. First, microsaccade amplitude dropped to a minimum just before the generation of a saccade. Second, the delay of response saccades was a function of microsaccade amplitude: Microsaccades with larger amplitudes were followed by longer response latencies. These finding were predicted by a recently proposed model that attributes microsaccade generation to fixation-related activity in a saccadic motor map that is in competition with the generation of large saccades (Rolfs et al., 2008). We propose, therefore, that microsaccade statistics provide a behavioral correlate of fixation-related activity in the oculomotor system

Color needs luminance for visual selection during scene search

When searching visual scenes, in addition to high-level scene semantics, we use low-level visual information from objects' defining features, such as color and luminance contrasts. What is the relative influence of color and luminance? Basic perceptual research suggests that we are not very sensitive to peripheral color. Yet color is thought to be an important basic feature guiding visual search. Previous gaze-contingent research shows that targets can be identified faster in color than in black-and-white scenes, therefore the availability of color in the visual periphery indeed helps visual search. However, color contrasts and luminance contrasts usually covary at object boundaries. Here we study the isolated roles of color and luminance during object-in-scene search by presenting either only color or only luminance contrasts in peripheral vision, using a gaze-contingent moving-window display and varying the amount and type of peripheral preview. We found that peripheral target selection was more efficient with luminance contrasts, whereas color was hardly used beyond the parafovea. We conclude that color contrasts in peripheral vision can only be efficiently used in scene search when they are correlated with luminance contrasts

Effects of Eye Movement Patterns and Scene-Object Relations on Description Production

This study investigates whether fixation behaviour during scene viewing can offer insights into sequentialisation in verbal scene description production. We explored the correlation between visual and linguistic attention on naturalistic scenes using scene descriptions and eye movement measures. Results demonstrate an overlap in object prioritization during scene viewing and describing. Our additional analysis of scene descriptions reveals a tendency towards selecting and prioritizing category-specific objects

Potsdam eye-movement corpus for scene memorization and search with color and spatial-frequency filtering

This repository provides data from a large scene corpus experiment with 200 participants, who memorized scenes in one session and searched for objects in different scenes in another session. Half of the participants saw the scenes in color, the other half saw the same scenes in grayscale. In each session, high or low spatial frequencies were gaze-contingently attenuated in central or peripheral vision while participants inspected the scenes. Scenes were displayed in one of five conditions: with a central low-pass filter, a central high-pass filter, a peripheral low-pass filter, a peripheral high-pass filter, or without any filtering

Microsaccade dynamics during covert attention

We compared effects of covert spatial-attention shifts induced with exogenous or endogenous cues on microsaccade rate and direction. Separate and dissociated effects were obtained in rate and direction measures. Display changes caused microsaccade rate inhibition, followed by sustained rate enhancement. Effects on microsaccade direction were differentially tied to cue class (exogenous vs. endogenous) and type (neutral vs. directional). For endogenous cues, direction effects were weak and occurred late. Exogenous cues caused a fast direction bias towards the cue (i.e., early automatic triggering of saccade programs), followed by a shift in the opposite direction (i.e, controlled inhibition of cue-directed saccades, leading to a ÔleakageÕ of microsaccades in the opposite direction)

Interoceptive focus shapes the experience of time.

The perception of time is a fundamental part of human experience. Recent research suggests that the experience of time emerges from emotional and interoceptive (bodily) states as processed in the insular cortex. Whether there is an interaction between the conscious awareness of interoceptive states and time distortions induced by emotions has rarely been investigated so far. We aimed to address this question by the use of a retrospective time estimation task comparing two groups of participants. One group had a focus on interoceptive states and one had a focus on exteroceptive information while watching film clips depicting fear, amusement and neutral content. Main results were that attention to interoceptive processes significantly affected subjective time experience. Fear was accompanied with subjective time dilation that was more pronounced in the group with interoceptive focus, while amusement led to a quicker passage of time which was also increased by interoceptive focus. We conclude that retrospective temporal distortions are directly influenced by attention to bodily responses. These effects might crucially interact with arousal levels. Sympathetic nervous system activation affecting memory build-up might be the decisive factor influencing retrospective time judgments. Our data substantially extend former research findings underscoring the relevance of interoception for the effects of emotional states on subjective time experience