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Two crucial sources of information available to an organism when moving through an environment are visual and vestibular stimuli. Macaque cortical area MSTd processes visual motion, including cues to self-motion arising from optic flow and also receives information about self-motion from the vestibular system. In humans, whether human MST (hMST) receives vestibular afferents is unknown. We have combined 2 techniques, galvanic vestibular stimulation and functional MRI (fMRI), to show that hMST is strongly activated by vestibular stimulation in darkness, whereas adjacent area MT is unaffected. The activity cannot be explained in terms of somatosensory stimulation at the electrode site. Vestibular input appears to be confined to the anterior portion of hMST, suggesting that hMST as conventionally defined may contain 2 subregions. Vestibular activity was also seen in another area previously implicated in processing visual cues to self-motion, namely the cingulate sulcus visual area (CSv), but not in visual area V6. The results suggest that cross-modal convergence of cues to self-motion occurs in both hMST and CSv.

Eye-tracking paradigms are increasingly used to investigate higher-level social and cognitive processing in autism spectrum disorder (ASD). However, the integrity of the oculomotor system within ASD is unclear, with contradictory reports of aberrant eye-movements on basic oculomotor tasks. The purpose of the current study was to determine whether reducing population heterogeneity and distinguishing neurocognitive phenotypes can clarify discrepancies in oculomotor behaviour evident in previous reports. Reflexive and volitional eye-movement control was assessed in 73 children aged 8-14 years from four distinct groups: Autism Language Normal (ALN), Autism Language Impaired (ALI), non-autistic Language Impaired (LI) and Typically Developing (TD). Eye-movement control was measured using pro- and antisaccade tasks and a novel 'search distracter' task to measure distractibility. Reflexive eye-movements were equivalent across groups, but deficits in volitional eye-movement control were found that aligned with language status, and were not specific to ASD. More than 80% of ALI and LI children presented error rates at least 1.5 SDs below the TD mean in an antisaccade task. In the search distracter task, 35.29% of ALI children and 43.75% of LI children had error rates greater than 1.5 SDs compared with 17.64% of ALN children. A significant proportion of children with neurodevelopmental disorders involving language function have pronounced difficulties suppressing reflexive saccades and maintaining fixations in the presence of competing stimuli. We extend the putative link between ALI and LI populations to non-language tasks, and highlight the need to account for co-morbidity in understanding the ontogenesis of ASD.

Optic flow motion patterns can be a rich source of information about our own movement and about the structure of the environment we are moving in. We investigate the information available to the brain under real operating conditions by analyzing video sequences generated by physically moving a camera through various typical human environments. We consider to what extent the motion signal maps generated by a biologically plausible, two-dimensional array of correlation-based motion detectors (2DMD) not only depend on egomotion, but also reflect the spatial setup of such environments. We analyzed the local motion outputs by extracting the relative amounts of detected directions and comparing the spatial distribution of the motion signals to that of idealized optic flow. Using a simple template matching estimation technique, we are able to extract the focus of expansion and find relatively small errors that are distributed in characteristic patterns in different scenes. This shows that all types of scenes provide suitable motion information for extracting ego motion despite the substantial levels of noise affecting the motion signal distributions, attributed to the sparse nature of optic flow and the presence of camera jitter. However, there are large differences in the shape of the direction distributions between different types of scenes; in particular, man-made office scenes are heavily dominated by directions in the cardinal axes, which is much less apparent in outdoor forest scenes. Further examination of motion magnitudes at different scales and the location of motion information in a scene revealed different patterns across different scene categories. This suggests that self-motion patterns are not only relevant for deducing heading direction and speed but also provide a rich information source for scene structure and could be important for the rapid formation of the gist of a scene under normal human locomotion.

In two experiments, the source of competition in the saccadic Stroop effect was investigated. Colored strings of letters were presented at fixation with colored patches in the surround. The task of the participants was to make an eye movement to the patch in the same color as the central string of letters. Three types of cues were compared: Either the string of letters composed a word indicating a direction (the saccadic Stroop condition), or it was a set of arrow signs, or a peripheral stimulus appeared. Whereas response times and saccade errors were similarly influenced by the different types of cues, saccade trajectory deviations away from the cue were found only for peripheral onsets. A second experiment demonstrated that the absence of the curvature effects for direction words was not due to insufficient time to process the words. The results raise doubts on whether the saccadic Stroop effect is effectively an oculomotor effect and could pose a challenge to models of saccade target selection.

Age-related macular degeneration (AMD) is the single most common cause of vision loss in people over the age of 501. Individuals with low vision caused by macular disease, experience severe difficulty with everyday tasks such as reading2, which has profound detrimental consequences for their quality of life3. We have developed an app for the iPad (the MD evReader) that aims to improve reading (of electronic books) by enhancing the effectiveness of the eccentric viewing technique (EV) using dynamic text presentation. Eccentric viewing is a simple strategy adopted by individuals with AMD that involves using the relatively preserved peripheral region of their retina in order to see. A limiting factor of the EV technique is that it relies on the individual holding their gaze away from the focus of interest and suppressing the natural and strong, tendency to make eye-movements (saccades). During normal reading, for example, a stereotypical pattern of horizontal saccades are made, from left-to-right, enabling fixations to be made on each word4 – Figure 1a). The natural inclination to make saccades is, however, difficult to suppress and limits the effectiveness of eccentric viewing in people with macular disease.

The neural basis of parallel saccade programming was examined in an event-related fMRI study using a variation of the double-step saccade paradigm. Two double-step conditions were used: one enabled the second saccade to be partially programmed in parallel with the first saccade while in a second condition both saccades had to be prepared serially. The intersaccadic interval, observed in the parallel programming (PP) condition, was significantly reduced compared with latency in the serial programming (SP) condition and also to the latency of single saccades in control conditions. The fMRI analysis revealed greater activity (BOLD response) in the frontal and parietal eye fields for the PP condition compared with the SP double-step condition and when compared with the single-saccade control conditions. By contrast, activity in the supplementary eye fields was greater for the double-step condition than the single-step condition but did not distinguish between the PP and SP requirements. The role of the frontal eye fields in PP may be related to the advanced temporal preparation and increased salience of the second saccade goal that may mediate activity in other downstream structures, such as the superior colliculus. The parietal lobes may be involved in the preparation for spatial remapping, which is required in double-step conditions. The supplementary eye fields appear to have a more general role in planning saccade sequences that may be related to error monitoring and the control over the execution of the correct sequence of responses.

Illusory position shifts induced by motion suggest that motion processing can interfere with perceived position. This may be because accurate position representation is lost during successive visual processing steps. We found that complex motion patterns, which can only be extracted at a global level by pooling and segmenting local motion signals and integrating over time, can influence perceived position. We used motion-defined Gabor patterns containing motion-defined boundaries, which themselves moved over time. This ‘motion-defined motion’ induced position biases of up to 0.5°, much larger than has been found with luminance-defined motion. The size of the shift correlated with how detectable the motion-defined motion direction was, suggesting that the amount of bias increased with the magnitude of this complex directional signal. However, positional shifts did occur even when participants were not aware of the direction of the motion-defined motion. The size of the perceptual position shift was greatly reduced when the position judgement was made relative to the location of a static luminance-defined square, but not eliminated. These results suggest that motion-induced position shifts are a result of general mechanisms matching dynamic object properties with spatial location.

Perceiving someone's averted eye-gaze is thought to result in an automatic shift of attention and in the preparation of an oculomotor response in the direction of perceived gaze. Although gaze cues have been regarded as being special in this respect, recent studies have found evidence for automatic attention shifts with nonsocial stimuli, such as arrow cues. Here, we directly compared the effects of social and nonsocial cues on eye movement preparation by examining the modulation of saccade trajectories made in the presence of eye-gaze, arrows, or peripheral distractors. At a short stimulus onset asynchrony (SOA) between the distractor and the target, saccades deviated towards the direction of centrally presented arrow distractors, but away from the peripheral distractors. No significant trajectory deviations were found for gaze distractors. At the longer SOA, saccades deviated away from the direction of the distractor for all three distractor types, but deviations were smaller for the centrally presented gaze and arrow distractors. These effects were independent of whether line-drawings or photos of faces were used and could not be explained by differences in the spatial properties of the peripheral distractor. The results suggest that all three types of distractors (gaze, arrow, peripheral) can induce the automatic programming of an eye movement. Moreover, the findings suggest that gaze and arrow distractors affect oculomotor preparation similarly, whereas peripheral distractors, which are classically regarded as eliciting an automatic shift of attention and an oculomotor response, induce a stronger and faster acting influence on response preparation and the corresponding inhibition of that response.

In masked priming, responses are often speeded when primes are similar to targets (‘positive compatibility effect’). However, sometimes similarity of prime and target impairs responses (‘negative compatibility effect’). A similar distinction has been found for the curvature of saccade trajectories. Here, we test whether the same inhibition processes are involved in the two phenomena, by directly comparing response times and saccade curvature within the same masked priming paradigm. Interestingly, we found a dissociation between the directions of masked priming and saccade curvature, which could indicate that multiple types of inhibition are involved in the suppression of unwanted responses.

When we Wxate an object, our eyes are not entirely still, but undergo small displacements such as microsaccades. Here, we investigate whether these micro- saccades are sensitive to the preparatory processes involved in programming a saccade. We show that the frequency of microsaccades depends in a specific manner on the intention where to move the eyes (towards a target location or away from it), when to move (immediately after the onset of the target or after a delay), and what type of cue is followed (a peripheral onset or a centrally presented symbolic cue). In particular, in the preparatory interval before and early after target onset, more microsaccades were found when a delayed saccade towards a peripheral target was prepared than when a saccade away was programmed. However, no such divergence in the frequency of microsaccades was observed when saccades were initiated immediately after the onset of the target or when the saccades were programmed on the basis of a centrally presented arrow cue. The results are discussed in the context of the neural correlates of response preparation, known as preparatory set.

Neurophysiological studies have demonstrated multisensory interaction effects in the neural structures involved in saccade generation when visual, auditory or somatosensory stimuli are presented bimodally. Visual-auditory interaction effects have been demonstrated in numerous behavioural studies of saccades but little is known about interaction effects involving somatosensory stimuli. The present study examined visual-somatosensory interaction effects on saccade generation using a multisensory paradigm, whereby task-irrelevant distractors appeared spatially-coincident with, or remote from the designated saccade target. Somatosensory distractors reduced the latency of saccades when presented before the visual target and the greatest facilitation effect was observed with spatially-coincident stimuli. Visual distractors spatially-coincident with a somatosensory target reduced latency (and increased peak velocity) when presented before and after the target. Visual distractors contralateral to somatosensory targets increased saccade latency and produced high error rates of saccades made to the distractor. The high error rates and latency modulation with visual distractors is consistent with a bias for visual stimuli in the saccadic system. In the visual target condition, saccade latency was modulated by a somatosensory distractor that was entirely task-irrelevant and this effect was always greatest with spatially-coincident distractors. The multisensory distractor effects are discussed in terms of saccades being programmed to the non-target modality, the early triggering of a non-spatial saccade 'when' signal, and multisensory neuronal enhancement effects.

Studies investigating the effects of observing a gaze shift in another person often apply static images of a person with an averted gaze, while measuring response times to a peripheral target. Static images, however, are unlike how we normally perceive gaze shifts of others. Moreover, response times might only reveal the effects of a cue on covert attention and might fail to uncover cueing effects on overt attention or response preparation. We therefore extended the standard paradigm and measured cueing effects formore realistic, dynamic cues (video clips),while comparing response times, saccade direction errors and saccade trajectories. Three cues were compared: A social cue, consisting of a eye-gaze shift, and two socially less relevant cues, consisting of a head tilting movement and a person walking past. Similar results were found for the two centrally presented cues (eye-gaze shift and head tilting) on all three response measures, suggesting that cueing is unaffected by the social status of the cue. Interestingly, the cue showing a person walking past showed a dissociation in the direction of the effects on response times on the one hand, and saccade direction errors and latencies on the other hand, suggesting the involvement of two types of (endogenous and exogenous) attention or a distinction between attention and sacadic response preparation. Our results suggest that by using dynamic cues and multiple response measures, properties of cueing can be revealed that would not be found otherwise.