PubMed · 6141411
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1984-02-11. Right hemisphere dysfunction and schizophrenia.. https://pubmed.ncbi.nlm.nih.gov/6141411/
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We report on a left-handed patient with an ischemic infarction affecting exclusively the total length of the corpus callosum. This lesion clinically correlated with an almost complete callosal disconnection syndrome as described in callosotomy subjects, including unilateral verbal anosmia, hemialexia, unilateral ideomotor apraxia, unilateral agraphia, unilateral tactile anomia, unilateral constructional apraxia, lack of somesthetic transfer and dissociative phenomena. Despite the patient's left-handedness, his pattern of deficits was similar to the disconnection syndrome found in right-handers. Our report focusses on motor dominance and praxis. We followed-up the improvement in left apraxia and investigated the ability to initiate and learn a new visuo-motor skill. The results permit two tentative assumptions: (1) that the improvement in left apraxia was due to a compensatory increase in ipsilateral proximal muscle control, and (2) that motor dominance, i.e. the competence to initiate and learn a new movement pattern, was hemispherically dissociable from manual dominance in the sense of praxis control.
The classical features of motor disorders due to neurological disease affecting the pyramidal pathways, cerebellum and basal ganglia in humans are well known. What is less understood is the clinical world of apraxia--'inability to perform purposeful skilled movements in the absence of any elementary motor (weakness, akinesia, abnormal posture or tone) or sensory deficits, or impaired comprehension or memory'. Much of what clinicians call apraxia is a failure of gesture production to command, due to problems of transcoding language into motor action, without motor deficit in ordinary life. However, damage to premotor regions and superior parietal lobules provokes devastating spontaneous higher-order motor deficits, including limb-kinetic apraxia, diagnostic apraxia, visuomotor apraxia and ideational apraxia.
This paper presents a reconceptualisation of apraxia of speech (AOS) and reviews a range of acoustic and articulatory data which have been reported on apraxia of speech. Data from both domains, and previous theoretical debate are discussed as support for this cognitive-based reconceptualisation.