McGilchrist on the Left Brain’s Wilful Denial

The following paragraphs are a quote from Iain McGilchrist’s book, ‘The Master and his Emissary’. Self explanatory and compelling, as usual.

“Insight into illness generally is dependent on the right hemisphere, and those who have damage to the right hemisphere tend to deny their illness – the well-recognised, and extraordinary phenomenon of anosognosia, in which patients deny or radically minimise the fact that they have, for example, a blatant loss of use of what may be one entire half of the body.A patient with a completely paralysed (left) limb may pointedly refuse to accept that there is anything wrong with it, and will come up with the most preposterous explanations for why he is not actually able to move it on request. This happens to some degree in the majority of cases after a stroke affecting the left side of the body (involving right-hemisphere damage), but practically never after a right-sided stroke (involving lefthemisphere damage). The phenomenon of denial can be temporarily reversed by activating the affected right hemisphere.Equally, denial of illness (anosognosia) can be induced by anaesthetising the right hemisphere.

Note that it is not just a blindness, a failure to see – it’s a wilful denial. Hoff and Pötzl describe a patient who demonstrates this beautifully: ‘On examination, when she is shown her left hand in the right visual field, she
looks away and says ‘I don’t see it.’ She spontaneously hides her left hand under the bedclothes or puts it behind her back. She never looks to the left, even when called from that side.’If forced to confront the affected limb, there is not infrequently a sense of revulsion from it, known as misoplegia: if the examiner puts the patient’s own left hand in her right hand, ‘she takes hold of it only to drop it immediately with an expression of disgust’.

In right-hemisphere lesions, there is not only denial or indifference in the face of incapacity, but sometimes a disturbance of mood ‘reminiscent of the fatuousness of those with frontal lesions: euphoria, joviality, a penchant for feeble puns’. One of the patients reported by Hécaen and de Ajuriaguerra, who had complete hemi-asomatognosia caused by a parietal tumour ‘exhibited a surprising joviality, at the same time complaining of a fierce headache.’

Denial is a left-hemisphere speciality: in states of relative right hemisphere inactivation, in which there is therefore a bias toward the left hemisphere, subjects tend to evaluate themselves optimistically, view pictures more positively, and are more apt to stick to their existing point of view. In the presence of a right-hemisphere stroke, the left hemisphere is ‘crippled by naively optimistic forecasting of outcomes’. It is always a winner: winning is associated with activation of the left amygdala, losing with right amygdala activation.”