Interaction between cognitive and affective processes
Name: Bob Rafal
Position: Professor of Clinical Neuroscience and Neuropsychology
Primary affiliation:School of Psychology, Univeristy of Wales, Bangor
More Affiliations: Consultant Neurologist, North Wales Brain Injury Service
Postal address: Brigantia Building, Penrallt Road, Bangor LL572AS, UK
Voice: (+44) 124 838 3603
Facsimile: (+44) 124 838 2599
The goal of my research program is to understand the brain preparatory states and processes that determine whether a visual signal will be perceived or responded to. Selective attention allows the organism to respond to a given stimulus in one way under one set of circumstances, a different way under another, to not respond at all, or to delay a response pending further information. It is through such mechanisms that past learning, motivation, and emotion may influence behavior. The research employs two converging and complementary strands of inquiry involving normal adults and neurological patients. One approach is motivated by clinical observation in patients with classical neuropsychological disorders of visual attention, such as hemispatial neglect. We study deficits of perception, attention and eye movements in patients with focal brain lesions of frontal lobe, parietal lobe and thalamus. The second strand of inquiry involves experiments employing transcranial magnetic stimulation (TMS) in normal adults.
Key words: Neuropsychololgy; TMS; visual attention; eye movements; hemispatial neglect.
- 1973. M.D., Jefferson Medical College, Philadelphia, Pennsylvania.
- 1969 B.A., University of Delaware, Newark Biology.
Positions and Employment:
- 1999-to present. Professor of Clinical Neuroscience and Neuropsychology, University of Wales, Bangor.
- 1989. Associate Professor of Neurology, Brown University.
- 1989-1995. Associate Professor of Neurology, University of California, Davis.
- 1986-1989. Assistant Professor of Neurology, Brown University.
- 1985-1989. Professor of Neurology, University of California, Davis
- 1984-1986. Assistant Professor of Medicine, Brown University.
- 1980-1984. Clinical Assistant Professor of Neurology, University of Oregon HSU.
- 1977-1984. Private practice of Neurology, Hillsboror and Portland, Oregon.
- 1974-1977. Neurology Residency, Oregon Health Sciences University, Portland, Oregon.
- 1973-1974. General Medical Training (PGY1),Good Samaritan Hospital, Portland, Oregon.
1) Cortical control of eye movement reflexes
This research programme examines the integration of cortical and subcortical circuitry regulating a basic behaviour common to all vertebrates - visual orienting -and will help to explain how adaptive behaviour of the whole organism is generated to provide for a continuity of experience and coherent goal directed behaviour. Specifically it will examine how more phylogenetically recent regions of oculomotor cortex regulate archetypal midbrain mechanisms for reflexive visual orienting in order to co-ordinate strategic and environmental demands on the oculomotor system.
We employ a fixation offset effect (FOE) paradigm to measure the effect of strategic control of midbrain reflexes, and will identify the specific areas of cortex that exercise this control by transiently inactivating oculomotor cortex with TMS. Physiological studies have shown that the visual grasp reflex (VGR - reflexive eye movements toward a visual transient) is mediated by an opponent circuit within the superior colliculus. There are mutually inhibitory connections between movement cells that trigger the visual grasp reflex (VGR), and fixation cells that anchor the eyes when a visual signal is present at fixation. Our studies of the FOE in normals and neurological patients have indicated that: 1) there are separate neural systems for control of fixation for exogenous and endogenous saccades and; 2) these circuits can be modulated by strategic control. Currently we are conducting a series of experiments including:
(i) TMS studies of parietal and frontal lobe cortex on control of ocular fixation and voluntary and reflexive eye movements.
(ii) Effects of strategic oculmotor set and trace conditioning on the FOE in patients with Parkinson’s disease.
2) Neural Substrates for Saccade Remapping and Inhibitory Spatial Tagging
When we move our eyes the location of stationary objects is remapped on our retinae – but they stay at the same location in the world. To sustain a durable representation of objects in the world, therefore, the brain must 1) remap the location of objects to compensate for movement on the retina produced by the saccade; 2) maintain a record, within this remapped representation of space, of locations already examined. Our laboratory has helped identify the neural substrates for an inhibitory spatial tag (referred to as ‘inhibition of return’); and we are now studying how this inhibitory spatial tag is sustained in a durable representation of the external world across saccadic eye movements. In the coming year we plan to:
a) use TMS to identify the regions of cortex that are involved in spatial remapping.
b) study patients with lesion of the thalamus to specify the role of thalamic nucleii in saccade remapping and inhibitory spatial tagging.
1. Arend I, Rafal R, Ward R (2008). Spatial and temporal deficits are regionally dissociable in patients with pulvinar lesions. Brain, in the press.
2. Rafal R, Ward R, Danziger S (2006). Selection for action and selection for awareness: Evidence from hemispatial neglect. Brain Research 1080, 2-8.
3. Berger A, Henik A, Rafal R (2005). Competition between endogenous and exogenous orienting of visual attention. Journal of Experimental Psychology: General 134, 207–221.
4. Sapir A, Hayes A, Henik A, Danziger S, Rafal R (2004). Parietal lobe lesions disrupt saccadic remapping of inhibitory location tagging. Journal of Cognitive Neuroscience 6, 503-509.
5. Machado L, Rafal R (2004). Control of fixation and saccades in humans with chronic lesions of oculomotor cortex. Neuropsychology 18, 115-123.
6. Rafal R, Danziger S, Grossi G, Machado L, Ward R (2002).Visual detection is gated by attending for action: evidence from hemispatial neglect. Proceedings of the National Academy of Sciences U.S.A. 99, 16371-16375.
7. Ward R, Danziger S, Owen V, Rafal R (2002). Deficits in spatial coding and feature binding following damage to the human pulvinar. Nature Neuroscience 5, 99-100.
8. Vuilleumier P, Sagiv N, Hazeltine E, Poldrack RA, Swick D, Rafal R, Gabrieli JDE (2001). Neural fate of seen and unseen faces in visuospatial neglect: A combined event-related fMRI and ERP study. Proceedings of the National Academy of Sciences U.S.A. 98, 3495-3500.
9. Vuilleumier P, Rafal R (1999). "Both" means more than "two": localizing and counting in patients with visuospatial neglect. Nature Neuroscience 2, 783-784.
10. Ro T, Cheifet S. Ingle H, Shoup R, Rafal RD (1999). Localization of the human frontal eye fields and motor hand area with transcranial magnetic stimulation and magnetic resonance imaging Neuropsychologia 37, 225-231.