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Neglect |
| Much of my research deals with the
performance and rehabilitation of patients who have
suffered brain damage. This work (known as
'Neuropsychology') has two main goals: it gives us a
better understanding of the brain's function as well as
helping in developing and assessing techniques for
rehabilitation. By examining which abilities are impaired
or preserved following damage to different regions, we
can infer the role of those regions of the brain. A
classic example is the pioneering work by Paul Broca
during the nineteenth century. He observed a patient who
had great difficulties speaking despite being able to
understand speech. Broca inferred that the region damaged
in this patient (located on the left frontal portion of
the brain's surface) was involved with the motor aspects
of speech. My work is greatly aided by the participation
of members of the volunteer panel. These volunteers give
us an idea of the capabilities of neurologically healthy
individuals who are of the same age, sex and handedness
as the patients we see. I work with patients who have a debilitating disorder known as 'unilateral neglect'. These patients often fail to see or respond to objects on the side opposite to their lesion. For example, patients with damage to the right side of their brain will often only eat food from the right side of their plate, will bump into the left side of doorways, and only shave the right side of their face. Such behaviour can not be accounted for by a loss in visual acuity or basic perception: patients who have defects on one side of their visual fields will simply shift their body or eyes to observe objects in their blind field. In contrast, neglect patients fail to orient in order to perceive objects in their bad field. One simple demonstration of this phenomena is to ask the patient to describe all of the houses they would see on an imaginary walk from their house to the local pub. A patient with only perceptual damage will quickly be able to recall all of the houses. On the other hand, a patient with neglect following right brain damage would mention only the houses on the right side of the street, yet when asked to describe the route home the patients will only describe the houses which they previously neglected. Understanding the difficulties and preserved skills found in unilateral neglect has given us new insights into how the brain is organised. For example, unilateral neglect is more common and more severe following damage to the right side of the brain (while the left side of the brain generally deals with skills such as language). This has led scientists to speculate that the right side of the brain plays a special role in representing space. In particular, the damage to the right parietal lobe seems to induce neglect. Traditionally it has been assumed that these patients only have difficulty viewing or imagining one side of space. However, some of my recent work suggests that these patients also have difficulty initiating movements toward the impaired side of space. For example, if asked to move their arms to the left, patients with neglect following right parietal lobe damage are slower to begin moving than if they are asked to move toward the right. This provocative finding challenges traditional views of the parietal lobe's role. |
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