Ramp-to-threshold dynamics in a hindbrain population controls the timing of spontaneous saccades

Organisms have the capacity to make decisions based solely on internal drives. However, it is unclear how neural circuits form decisions in the absence of sensory stimuli. Here we provide a comprehensive map of the activity patterns underlying the generation of saccades made in the absence of visual stimuli. We perform calcium imaging in the larval zebrafish to discover a range of responses surrounding spontaneous saccades, from cells that display tonic discharge only during fixations to neurons whose activity rises in advance of saccades by multiple seconds. When we lesion cells in these populations we find that ablation of neurons with pre-saccadic rise delays saccade initiation. We analyze spontaneous saccade initiation using a ramp-to-threshold model and are able to predict the times of upcoming saccades using pre-saccadic activity. These findings suggest that ramping of neuronal activity to a bound is a critical component of self-initiated saccadic movements.

Structural and Contextual Cues in Third-Person Pronoun Interpretation by Children with Autism Spectrum Disorder and Their Neurotypical Peers

This study investigates the use of structural and discourse contextual cues in the interpretation of third-person pronouns by children and adolescents with autism and their neurotypical peers. Results show that referent-biasing contextual information influences pronominal interpretation and modulates looking patterns in both groups compared to a context-neutral condition. These results go against the predictions of Weak Central Coherence and the notion that pragmatics in general is impaired in ASD, since the ASD group was able to use details in discourse context to influence the pronominal interpretation process. However, although discourse context influenced looking patterns in both groups, the groups nevertheless diverged in the nature of these patterns, suggesting that behavioral differences may emerge in more complicated discourse tasks.

An experimental eye-tracking study of text adaptation for readers with dyslexia: effects of visual support and word frequency

Easy-to-read guidelines recommend visual support and lexical simplification to facilitate text processing, but few empirical studies confirm a positive effect from these recommendations in individuals with dyslexia. This study examined the influence of the visual support and lexical simplification on sentence processing through eye movements at both the text- and word-level, and the differences between readers with and without dyslexia. Furthermore, we explored the influence of reading experience and vocabulary, as control variables. We tested 20 young adults with dyslexia and 20 chronological age-matched controls. Participants read 60 sentences in total. Half the sentences contained an image and the other half did not, and half contained a low-frequency word and half a high-frequency word. Results showed that visual support and lexical simplification facilitated sentence processing, potentially by jointly facilitating lexical semantic access. We also found that participants with lower print exposure and lower vocabulary benefited more from word-level lexical simplification. We conclude that both adaptations could benefit readers with low print exposure and smaller vocabularies, and therefore, to many dyslexic readers who show these characteristics.

Using head-mounted eye tracking to examine visual and manual exploration during naturalistic toy play in children with and without autism spectrum disorder

Multimodal exploration of objects during toy play is important for a child's development and is suggested to be abnormal in children with autism spectrum disorder (ASD) due to either atypical attention or atypical action. However, little is known about how children with ASD coordinate their visual attention and manual actions during toy play. The current study aims to understand if and in what ways children with ASD generate exploratory behaviors to toys in natural, unconstrained contexts by utilizing head-mounted eye tracking to quantify moment-by-moment attention. We found no differences in how 24- to 48-mo children with and without ASD distribute their visual attention, generate manual action, or coordinate their visual and manual behaviors during toy play with a parent. Our findings suggest an intact ability and willingness of children with ASD to explore toys and suggest that context is important when studying child behavior.

Avoidance of tobacco health warnings? An eye-tracking approach

AIMS

Among three eye-tracking studies, we examined how cigarette pack features affected visual attention and self-reported avoidance of and reactance to warnings.

DESIGN

Study 1: smoking status × warning immediacy (short-term versus long-term health consequences) × warning location (top versus bottom of pack). Study 2: smoking status × warning framing (gain-framed versus loss-framed) × warning format (text-only versus pictorial). Study 3: smoking status × warning severity (highly severe versus moderately severe consequences of smoking).

SETTING

University of Bristol, UK, eye-tracking laboratory.

PARTICIPANTS

Study 1: non-smokers (n = 25), weekly smokers (n = 25) and daily smokers (n = 25). Study 2: non-smokers (n = 37), smokers contemplating quitting (n = 37) and smokers not contemplating quitting (n = 43). Study 3: non-smokers (n = 27), weekly smokers (n = 26) and daily smokers (n = 26).

MEASUREMENTS

For all studies: visual attention, measured as the ratio of the number of fixations to the warning versus the branding, self-reported predicted avoidance of and reactance to warnings and for study 3, effect of warning on quitting motivation.

FINDINGS

Study 1: greater self-reported avoidance [mean difference (MD) = 1.14; 95% confidence interval (CI) = 0.94, 1.35, P < 0.001, ηp2  = 0.64] and visual attention (MD = 0.89, 95% CI = 0.09, 1.68, P = 0.03, ηp2  = 0.06) to long-term warnings, but not for reactance (MD = 0.14, 95% CI = -0.04, 0.32, P = 0.12, ηp2  = 0.03). Increased visual attention to warnings on the upper versus lower half of the pack (MD = 1.8; 95% CI = 0.33, 3.26, P = 0.02, ηp2  = 0.08). Study 2: higher self-reported avoidance of (MD = 0.70; 95% CI = 0.59,0.80, P < 0.001, ηp2  = 0.61) and reactance to (MD = 0.37; 95% CI = 0.27, 0.47, P < 0.001, ηp2  = 0.34) loss-framed warnings but little evidence of a difference for visual attention (MD = 0.52; 95% CI = -0.54, 1.58, P = 0.30, ηp2  = 0.01). Greater visual attention, avoidance and reactance to pictorial versus text-only warnings (all Ps < 0.001, ηp2  > 0.25). Study 3: greater self-reported avoidance of (MD = 0.37; 95% CI = 0.25, 0.48, P < 0.001, ηp2  = 0.33) and reactance to (MD = 0.14; 95% CI = 0.05, 0.23, P = 0.003, ηp2  = 0.11) highly severe warnings but findings were inconclusive as to whether there was a difference in visual attention (MD = -0.55; 95% CI = -1.5, 0.41, P = 0.24, ηp2  = 0.02).

CONCLUSIONS

Subjective and objective (eye-tracking) measures of avoidance of health warnings on cigarette packs produce different results, suggesting these measure different constructs. Visual avoidance of warnings indicates low-level disengagement with warnings, while self-reported predicted avoidance reflects higher-level engagement with warnings.

A novel eye-tracking paradigm for indexing social avoidance-related behavior in fragile X syndrome

Fragile X syndrome (FXS) is characterized by hallmark features of gaze avoidance, reduced social approach, and social anxiety. The development of therapeutics to manage these symptoms has been hindered, in part, by the lack of sensitive outcome measures. This study investigated the utility of a novel eye-tracking paradigm for indexing social avoidance-related phenotypes. Adolescent/young adult-aged males with FXS (n = 24) and typical development (n = 23) participated in the study. Participants viewed faces displaying direct or averted gaze and the first fixation duration on the eyes was recorded as an index of initial stimulus registration. Fixation durations did not differ across the direction of gaze conditions in either group, although the control group showed longer initial fixations on the eyes relative to the FXS group. Shorter initial fixation on averted gaze in males with FXS was a robust predictor of the severity of their social avoidance behavior exhibited during a social greeting context, whereas parent-reported social avoidance symptoms were not related to performance in the semi-naturalistic context. This eye-tracking paradigm may represent a promising outcome measure for FXS clinical trials because it provides a quantitative index that closely maps onto core social avoidance phenotypes of FXS, can be completed in less than 20 min, and is suitable for use with individuals with low IQ.