Papathanasiou, Ilias; (2002) Writing and its recovery after stroke: A behavioural and neurophysiological investigation. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The production of written language is a complex function. Various linguistic, cognitive and motor processes are involved. Acquired disorders of writing have received relatively little attention from researchers and clinicians. The purpose of this thesis to study the rehabilitation of writing and use the techniques of modern neurosciences to investigate the underlying mechanisms of recovery. The first aim is to study the phenomenon of hemiplegic writing, a treatment approach, which involves using a prosthesis to promote recovery of writing with the hemiplegic right arm. This rehabilitation strategy is derived from information about models of written language and knowledge of writing impairment. It is based on the premise that since writing is a complex and multi-component task, enhancing interaction between the different linguistic and motor systems involved can enhance recovery of writing. To date, no information is available about the interactions between the different components of writing such as the visual perceptual aspects of symbolic representation and the motor planning of writing movements and their neuronal organization in neurologically intact subjects. Therefore, the second aim of this thesis is to examine these interactions between the linguistic and motor aspects of writing in normal neurologically intact adults using transcranial magnetic stimulation. The first study examined the behavioural features of writing in patients (n=10) and how they are altered following rehabilitation therapy using a writing aid to overcome the motor impairment of the dominant hand to enable patients to write. The results from an outcome study in these patients highlighted the nature of the behavioral changes that occurred following therapy and examined their relationship to changes observed in the aphasia profile and linguistic type errors. The second study used transcranial magnetic stimulation to examine the mechanisms of recovery associated with the motor changes observed in the paretic arm following the use of the writing aid. The results from seven patients indicated that the recruitment of ipsilateral pathways from the non-dominant right hemisphere is an important feature of the recovery. This was evident only during the task of writing. The third study employed transcranial magnetic stimulation and investigated the changes produced by performance of visual matching and imaginal writing tasks on corticospinal excitability of human hand muscles in normal subjects. The results from eight subjects showed lateralised effects during visual matching but not during imaginal writing. The fourth study compared the effects of actual writing versus drawing on motor cortex excitability using transcranial magnetic stimulation. The results from eight normal subjects revealed differences between writing and drawing in terms of their influence on motor excitability as indicated by changes in the size of motor evoked potentials and the duration of the silent period. Writing is a complex and mutli-component task, which involves the activation of diverse neuronal pathways as is evident from study 3 and 4. Recruitment of alternative motor pathways for writing following rehabilitation therapy may be responsible for the effects observed in the patients as reported in study 1 and 2. It is suggested that to facilitate recovery as part of rehabilitation therapy, understanding of the contributions of these diverse neuronal pathways is crucial.

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