Friday 2 March 2012 12.27 GMT
The collection of abilities and experiences that we call the mind emerges from the brain, so the study of the brain can provide important information about the mind. For most of the 20th century, mind-brain relationships could only be explored in people with damaged brains, typically caused by strokes or head injuries. Such damage can result in loss of consciousness, and in extreme cases coma, but more interestingly it can also result in changes in the content of consciousness.
There can be loss of some aspects of sensory experience despite the sense organs remaining intact, and there can be novel and unusual sensory experiences such as hallucinations. For example, damage to the colour area in the visual part of the brain can result in loss of colour experience, even though the colour receptors in the eye are working normally. Furthermore, abnormal activity in this area can lead to hallucinations of colour.
Studies of patients with brain damage reveal how much can be achieved without awareness. Patients with damage to the right side of the brain (“spatial neglect“) can successfully pick out the better of two objects (eg. an intact rather than a damaged house) while reporting that they cannot see any difference between them. Patients with damage to visual areas of the brain (“visual agnosia”) can’t recognise objects from their shape, but will adjust their hand to the shape of the object when picking it up. In these cases, information of which the patient is unaware is nevertheless sufficient to achieve a successful action. (…)
Frith C.D. (2007) Making up the mind, Wiley-Blackwell.