The 'anti-shift': Shifting attention opposite to a saccade

Training enables substantial decoupling of visual attention and saccade preparation

Visual attention is typically shifted toward the targets of upcoming saccadic eye movements. This observation is commonly interpreted in terms of an obligatory coupling between attentional selection and oculomotor programming. Here, we investigated whether this coupling is facilitated by a habitual expectation of spatial congruence between visual and motor targets. To this end, we conducted a dual-task (i.e., concurrent saccade task and visual discrimination task) experiment in which male and female participants were trained to either anticipate spatial congruence or incongruence between a saccade target and an attention probe stimulus. To assess training-induced effects of expectation on premotor attention allocation, participants subsequently completed a test phase in which the attention probe position was randomized. Results revealed that discrimination performance was systematically biased toward the expected attention probe position, irrespective of whether this position matched the saccade target or not. Overall, our findings demonstrate that visual attention can be substantially decoupled from ongoing oculomotor programming and suggest an important role of habitual expectations in the attention-action coupling.

Crowding expands and is less sensitive to target-flanker differences during a shift of visual attention

Target-flanker similarity and critical spacing control visual crowding when attention is pre-allocated, but these have not been studied when attention shifts. Flanked target Gabors appeared 8° left and right of central fixation throughout each 1.5 s trial. Subjects reported target Gabor tilt. In Expt. 1, target blinks increased accuracy, and flanker blinks decreased it, but only when attention shifted left or right from a central RSVP cue, hardly before it, indicating an exogenous/endogenous synergy. Whether parallel or orthogonal, flankers of the same wavelength as the target crowded substantially. Parallel half-wavelength flankers also crowded, but orthogonal half-wavelength ones did not. In Expt. 2, crowding when attention shifts was the same for targets and flankers within Bouma's bound (2.5° apart) as outside it (5.0° apart.) In Expt. 3, Bouma's bound was restored when attention was focused continuously on the target. We conclude that crowding temporarily expands and becomes less discriminative when attention shifts.

Blue-light effects on saccadic eye movements and attentional disengagement

People are constantly exposed to high-energy blue light as they spend considerable amounts of time reading and browsing materials on electronic products like computers and cellphones. Recent studies suggest that the stimulation of intrinsically photosensitive retinal ganglion cells (ipRGCs)-a newly discovered type of photoreceptor shown to be particularly sensitive to blue light-activates brain regions related to eye movements and attentional orienting (e.g., frontal eye fields). It remains unclear, however, whether and how blue light affects eye movements and attention behaviorally. We examined this by adopting the gap paradigm in which participants made saccades to a peripheral target as quickly and accurately as possible while the fixation sign vanished (i.e., the gap condition) or remained visible. Participants were exposed to blue and orange light on two separate days. Faster saccade latency under blue light was found across two experiments, and the results indicate that blue light shortened saccade latency when attention and eye movements operate simultaneously. Our findings provide evidence for the blue-light facilitatory effect on eye movements and attentional disengagement, and suggest that blue light can enhance the speed of saccadic eye movements.

Spatial attention and spatial short term memory in PSP and Parkinson's disease

Progressive Supranuclear Palsy (PSP) is a neurodegenerative disorder characterised by deterioration in motor, oculomotor and cognitive function. A key clinical feature of PSP is the progressive paralysis of eye movements, most notably for vertical saccades. These oculomotor signs can be subtle, however, and PSP is often misdiagnosed as Parkinson's disease (PD), in its early stages. Although some of the clinical features of PD and PSP overlap, they are distinct disorders with differing underlying pathological processes, responses to treatment and prognoses. One key difference lies in the effects the diseases have on cognition. The oculomotor system is tightly linked to cognitive processes such as spatial attention and spatial short-term memory (sSTM), and previous studies have suggested that PSP and PD experience different deficits in these domains. We therefore hypothesised that people with PSP (N = 15) would experience problems with attention (assessed with feature and conjunction visual search tasks) and sSTM (assessed with the Corsi blocks task) compared to people with PD (N = 16) and Age Matched Controls (N = 15). As predicted, feature and conjunction search were sgnificantly slower in the PSP group compared to the other groups, and this deficit was significantly worse for feature compared to conjunction search. The PD group did not differ from AMC on feature search but were significantly impaired on the conjunction search. The PSP group also had a pronounced vertical sSTM impairment that was not present in PD or AMC groups. It is argued that PSP is associated with specific impairment of visuospatial cognition which is caused by degeneration of the oculomotor structures that support exogenous spatial attention, consistent with oculomotor theories of spatial attention and memory.

Attention as a Unitary Concept

In this paper, I discuss attention in terms of selecting visual information and acting on it. Selection has been taken as a bedrock concept in attention research since James (1890). Selective attention guides action by privileging some things at the expense of others. I formalize this notion with models which capture the relationship between input and output under the control of spatial and temporal attention, by attenuating or discarding certain inputs and by weighing energetic costs, speed, and accuracy in meeting pre-chosen goals. Examples are given from everyday visually guided actions, and from modeling data obtained from visual searches through temporal and spatial arrays and related research. The relation between selection, as defined here, and other forms of attention is discussed at the end.