Our senses are constantly flooded with visual, tactile and auditory information, yet we are rarely, if ever, overwhelmed by these experiences. In fact, we only seem to become aware of sensory stimulations when they capture our attention. Much of my research is directed at understanding the mechanisms which determine which sensations enter our awareness, and whether we can use the relationship between attention and awareness to develop more effective therapies for patients who experience deficits of vision or awareness following brain damage.

PhD Students

I’m always interested to hear from students with an interest in my research areas. If you are considering a career in research you are welcome to contact me to discuss research ideas and funding opportunities such as the Durham Doctoral Fellowship.

I’m currently supervising Stephen Dunne, who is investigating the effects of operant conditioning on eye-movements and spatial attention.

Neurovisual Rehabilitation

Blindness on one side, known as a visual field deficit (VFD), is a common consequence of brain injury (~20000 cases per year). Patients with VFD are barred from driving and have great difficulty with activities of daily life but no treatment for VFD is available on the NHS. Our work on rehabilitation is based on developing compensatory visual exploration strategies for hemianopic patients [1], and is led by Prof Thomas Schenk.

The compensatory visual exploration training (VET) is a computer-based therapy which trains patients to explore their blind side more effectively. Our previous research has established that this training can produce significant improvements in patients’ visual ability when delivered in the laboratory under the supervision of a therapist. However, this method of delivery is time-consuming and expensive. In a current project Dr Lina Aimola is investigating the effectiveness of the therapy when patients administer the therapy themselves in their own homes without the presence of a therapist. This project is funded by a grant from the NHS Research for Patient Benefit scheme.

We also use a number of experimental approaches to develop treatments for hemianopia. For example, it had been suggested that of proprioceptive cues could greatly enhance the visual abilities of hemianopic patients [2]. However, when we applied this technique to a larger group of patients it did not reliably improve vision and unfortunately it appears that this technique is not beneficial for the majority of hemianopic patients [3]. Similarly, light-bending prisms have been used to treat VFDs by bringing visual information that normally falls in the blind side into the sighted side. However, this approach has not been scientifically evaluated so it is not known whether A) the prisms really reduce visual disability or B) the prisms benefit patients in their daily life beyond the lab.

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Attention and Awareness

We are constantly receiving sensory input from our eyes, ears and skin, yet only a small portion of this sensory information ever arrives in our conscious awareness. The question of what determines access to conscious awareness has been the subject of research interest for more than a century, yet remains one of the most controversial issues in psychology. This controversy has in part arisen because it is so difficult to disentangle “awareness” from other cognitive processes, making it very difficult to study in isolation. My research in this area makes use of paradigms in which participants fail to become aware of what should be obvious changes to a visual display (e.g. change blindness and inattentional blindness) and patients who have deficits of visual awareness or attention following brain damage (e.g. Hemianopia and hemineglect). Our findings so far suggest that it is usually necessary for a person to attend to a sensory event in order for it to reach conscious awareness, although some sensory events are sufficiently salient to ‘force’ their way into awareness.

Intriguingly, we have also been able to use attentional cues to manipulate awareness of visual events. More specifically, we used visible peripheral cues to modulate attention in a change detection task. Changes that occurred at cued locations were much more likely to be detected than changes at uncued locations. [4]. However, when we used a subliminal peripheral cue changes that occurred at cued locations were much less likely to be detected than changes at uncued locations [5]. We argue that this suppression of awareness appears to be caused by Inhibition of Return, which is a cognitive process that biases us against attending to things that we have already explored.

Recently, we have begun to investigate the effects of working memory on awareness in patients with deficits of attention with the aim of investigating the extent to which working memory can boost sensory inputs enough for them to enter awareness.

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Attention and eye-movements

Attention mediates access of sensory events to higher cognitive systems and can be driven by either top-down voluntary mechanisms or in a bottom-up fashion by the sensory properties of a stimulus. The exact mechanisms underlying these different modes of attention are controversial, but both types of attention appear to be tightly coupled to the systems used for the control of eye-movements. For example, visual spatial attention activates many of the same brain areas as eye-movements [6, 7].

Intriguingly, the nature of the coupling between oculomotor control and attention appears to be different for voluntary and reflexive attention, such that reflexive attention is more tightly bound to eye-movements. The main focus of my work in this area is to more precisely characterise the role of the eye-movement system in guiding attention. Much of this work has involved investigating the effect of lesions of the oculomotor system on attention. This research shows that problems making eye-movements lead to subtle deficits of reflexive attention, such that salient peripheral events fail to capture attention [8]. Interestingly, although oculomotor problems can disrupt reflexive attention they do not appear to disrupt inhibition of return [9], suggesting that 1) IOR does not depend on an initial attention shift and 2) IOR can be mediated by neural areas that are not directly responsible for generating eye-movements. Importantly, voluntary attention appears to be much more robust to damage to the oculomotor system, perhaps because voluntary attention can be driven by many cognitive systems (e.g. working memory).

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Eye abduction technique

We have also been using the eye abduction technique pioneered by [10] to investigate the role of the eye-movement system in cognitive processes such as spatial attention [11]. This paradigm involves participants performing experiments on a computer with their head turned at a forty degree Cartton for ESRC app.jpg angle, therefore having to look out of the corner of their eye (see figure 2). This manipulation prevents participants from planning eye-movements because the eye cannot move any further into the temporal hemifield. One great advantage of this technique is that it allows us to investigate the functional role of motor preparation in spatial cognition in healthy participants, avoiding the many methodological problems associated with experiments using neuropsychological patients. In one study [11] we asked participants to perform pop-out visual search tasks. We observed that eye abduction caused deficits of spatial attention at motorically inaccessible spatial locations. More specifically, participants were slower to detect targets during easy search, and began to miss targets when the search task was made more difficult (this deficit was reminiscent of patients with hemispatial neglect). These data suggest that the activation of the eye-movement system is critically important for attentional capture.

Figure 3

In a second study [12] we used the eye-abduction paradigm to investigate the importance of eye-movement preparation in exogenous attentional capture. JoCN Figure1.jpg Salient visual events trigger an exogenous shift of visuo-spatial attention which is superseded by a sustained inhibition of processing, known as inhibition of return (IOR- see figure 3). We observed that exogenous attentional capture was disrupted when the cue appeared at motorically inaccessible locations, but that IOR was unaffected. These data suggest that activation of the eye-movement system in critically important for exogenous attention but is not required for Inhibition of Return. Furthermore, they are evidence against the popular belief that IOR is caused by exogenous attentional capture, as we have shown IOR in the absence of exogenous attention. Instead, we propose the IOR and exogenous attention are controlled by tightly coupled but independent cognitive mechanisms.

In related work I’m about to begin an ESRC funded project (RES-000-22-4457) investigating the role of the oculomotor system in spatial working memory with Dr David Pearson and Dr Keira Ball.

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Gaze cueing

Dr Geoff Cole and I have conducted a series of experiments investigating gaze-cueing, which refers to automatic shifts of attention that are triggered by seeing someone else looking at something.

Sport Psychology

I’m currently supervising undergraduate projects investigating (a) the effects of different schedules of mental imagery on performance and (b) the role of motivational climate in performance (see here for a brief description of our preliminary findings)

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References

1. Lane, A.R., D.T. Smith, and T. Schenk, Clinical treatment options for patients with homonymous visual field defects. Clinical Opthalmology, 2008. 2(1): p. 93-102.

2. Schendel, K. and L.C. Robertson, Reaching out to see: Arm position can attenuate human visual loss. Journal of Cognitive Neuroscience, 2004. 16(6): p. 935-943.

3. Smith, D.T., A.R. Lane, and T. Schenk, Arm position does not attenuate visual loss in patients with homonymous field deficits. Neuropsychologia, 2008. 46: p. 2320-2325.

4. Smith, D.T. and T. Schenk, Reflexive attention attenuates change blindness (but only briefly) Perception & Psychophysics, 2008. 70(3): p. 489-495.

5. Smith, D.T. and T. Schenk, Inhibition of Return exaggerates change blindness. Quarterly Journal of Experimental Psychology, 2010. 63(11): p. 2231-2238.

6. Smith, D.T., S.R. Jackson, and C. Rorden, Transcranial magnetic stimulation of the left human frontal eye fields eliminates the cost of invalid endogenous cues. Neuropsychologia, 2005. 43(9): p. 1288-1296.

7. Smith, D.T., S.R. Jackson, and C. Rorden, Repetitive TMS over frontal eye fields disrupts visually cued auditory attention. Brain Stimulation, 2009. 2: p. 81-87.

8. Smith, D.T., C. Rorden, and S.R. Jackson, Exogenous orienting of attention depends upon the ability to execute eye movements. Current Biology, 2004. 14(9): p. 792-795.

9. Smith, D.T., S.R. Jackson, and C. Rorden, An intact eye-movement system is not required to generate Inhibition of Return. Journal of Neuropsychology, 2009(3): p. 267-271.

10. Craighero, L., M. Nascimben, and L. Fadiga, Eye position affects orienting of visuospatial attention. Current Biology, 2004. 14(4): p. 331-333.

11. Smith, D.T., et al., Deficits of reflexive attention induced by abduction of the eye. Neuropsychologia, 2010. 48: p. 1269-1276.

12. Smith, D.T., C. Rorden, and T. Schenk, Saccade preparation is required for exogenous attention but not endogenous attention or IOR. in review.