Unconscious interference without conscious re-representation
30 September 2010
Researchers from Institute of Psychiatry at King’s have solved one piece of an ancient puzzle: to what extent are we influenced by mental processes taking place outside of our conscious awareness? Recent advances in neuroscience suggest that unconscious mental processes have a significant effect on our conscious behaviour and awareness. Yet very little is known about how this occurs in the brain.
An important source of insight into these questions comes from the study of brain damaged patients who have lost the ability to consciously appreciate certain experiences, but retain an unconscious awareness which appears to influcence their behaviour. One such condition, called anosognosia for hemiplegia, provides researchers with a window into the very nature of self-awareness. Anosognosic patients are partially paralysed following a stroke but are unaware of their disability.
Fotopoulou and colleagues asked 14 stroke patients, half of whom were anosognosic, to carry out a task in which they had to complete a series of sentences of varying emotional content with an unrelated word, thus suppressing their automatic inclination to complete the sentence correctly. The idea was that if the patients were unconsciously aware of their paralysis, processing the emotional information in the sentences that related to paralysis would slow their reaction time. They were also asked, on a different occasion, to rate the same sentences in terms of how relevant they were to their own situation.
As expected, the anosognosic patients were significantly slower than the control group at completing the paralysis-related sentences, compared with sentences about other emotionally negative themes (relative to neutral themes), yet they denied the self-relevance of these sentences.
These findings strongly suggest that, while these patients are not consciously aware of their paralysis and associated negative emotions, information about their disability has been unconsciously laid down in their memories.
Dr Fotopoulou, who led the study, said: 'These findings have implications for understanding the neural and psychological mechanisms that allow motor failures and other experiences to be selectively, purposefully, yet unconsciously forgotten.'
The researchers also compared the patients’ brain scans and found that the anosognosic patients had brain damage in different areas to the control patients, helping to pinpoint the areas of the brain involved in explicit cognitive and emotional awareness.
'Damage to the anterior insular cortex, and some possible involvement of basal ganglia and limbic circuits, seems to impair patients’ ability to integrate these memories and their associated emotions into an explicit, affectively personalised and stable self-awareness,' said Dr Fotopoulou.
Fotopoulou, A. et al. (2010). Implicit awareness in anosognosia for hemiplegia: Unconscious interference without conscious re-representation. Brain.
Published online: http://brain.oxfordjournals.org/content/early/2010/09/07/brain.awq233.abstract