This thesis presents experiments investigating the cognitive neuropsychological mechanisms underlying anosognosia for motor deficit, i. e. lack of awareness or underestimation of a deficit in motor functioning following brain injury. Two contemporary explanations of anosognosia were considered. First, an account based on the Somatic Marker Hypothesis (SMH; Damasio, 1994), which suggests that anosognosia might be explained by emotional disturbance leading to irrational reports regarding motor deficits, via an impairment in somatic feedback to the brain. The second account, proposed by Frith, Blakemore and Wolpert (2000a), provides a cognitive neuropsychological explanation of anosognosia. This -model proposes that motor awareness depends on predicting the expected sensory consequences of intended movements, and comparing these predictions with the actual sensory consequences of movement. Three research predictions regarding anosognosia arose from Frith et al. (2000a): (i) preservation of internal representations of movement involving the impaired limb, (ii) failure to register discrepancies between intended (predicted) and actual movement, and (iii) absent contrary information regarding the actual state of the motor system. Experiments investigating these contemporary accounts of anosognosia are presented. An initial, psychophysiological pilot study concerning the SMH failed to replicate effects alleged to occur in healthy individuals; therefore, subsequent inspection of the SMH in a patient cohort was not pursued. Subsequent cognitive neuropsychological investigations focussed on the three predictions arising from Frith et al. (2000a) in patients with anosognosia for motor deficit, control patients without anosognosia, and age-matched healthy individuals. The main results of these studies showed (i) distorted internal representations of movement, (ii) impaired monitoring of movements, and (iii) increased levels of unilateral neglect (i.e. ignoring one half of space) in anosognosia. Findings inform current accounts of anosognosia and are discussed in the context of a normal model of action control and awareness.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:489025 |
| Date | January 2008 |
| Creators | Jenkinson, Paul Mark |
| Publisher | Keele University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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