CAUSES AND ASSOCIATIONS OF SEVERE AND PERSISTENT SPECIFIC SPEECH AND LANGUAGE DISORDERS IN CHILDREN

Eighty-two school-age children with severe and persistent specific speech and language disorders were studied. 71 had specific developmental language disorders, three had structural malformations (cleft palate) and eight had disorders acquired after a period of normal language development, including five with Landau-Kleffner syndrome. The sex ratio was 3.8 boys to one girl. Nearly half had a family history of speech-language disorder, with one in 5.2 affected siblings. Aetiological factors were found in 26 per cent: 11 per cent prenatal, 3 per cent perinatal and 12 per cent postnatal. 21 per cent had had a seizure and 7 per cent had had seizures after the age of eight. 29 per cent were left-handed, 90 per cent were clumsy and 22 per cent first walked after 18 months. The complex origins of specific speech and language disorders are discussed.     

DISSOCIATION AND NEUROSCIENCE: HISTORY AND NEW PERSPECTIVES

History of the study of dissociation begins in the second half of the nineteenth century. It begins in the works of Hughlings Jackson and Pierre Janet, and markedly influences development of psychoanalysis and other psychological trends. According to the modern definition, dissociation represents a disturbance or alteration in the normally integrative functions of identity, memory, or consciousness. Dissociative symptoms occur mainly due to some traumatic events and probably cannot be generally explained on the basis of neurological focal lesion. However, from recent findings, it may be inferred that temporal lobe epileptic activity is important in the generation of dissociative symptoms. Recent findings show that neural networks provide an attractive framework for modeling dissociative mental processes and dissociative mechanisms. In the article we propose a new theoretical connection among neural network models of dissociation, Freeman's model of chaos in the brain and electrophysiological findings regarding dissociative states. Concluding remarks are concerned with connections of dissociation and inter-hemispheric communication.     

REGENERATION AND INNERVATION OF NORMAL AND DYSTROPHIC MUSCLE CULTURED WITH NORMAL AND DYSTROPHIC SPINAL CORD

Teased strips of normal or dystrophic adult mouse muscle were cultured with embryonic normal or 'dystrophic' mouse spinal cord explants, in order to determine whether muscular dystrophy is of primary myopathic or neuropathic origin. When cultured with normal spinal cord, both normal and dystrophic muscle regenerated to form new cross-striated muscle fibres with peripherally located nuclei and showing spontaneous, synchronized contractions. Silver impregnation and acetyl-cholinesterase activity showed that neuromuscular junctions were formed. In marked contrast, both normal and dystrophic muscle cultured with spinal cord from dystrophic animals failed to show such functional regeneration, and neuromuscular junctions could not be identified. Only a few myotubes were formed, and these were rarely cross-striated, had internal nuclei, and only some showed asynchronous fibrillatory contractions. These results strongly suggest that murine muscular dystrophy has a neural pathogenesis. Histochemical reactions were carried out on serial frozen sections of the regenerated muscle fibres, and also of embryonic mouse muscle cultured in cord-myotome explants, to determine whether 'fibre types' were formed. All the fibres gave uniformly strong or medium reactions to phosphorylase, NADH-TR, myofibrillar ATPase, ATPase after acid preincubation, and the PAS reaction for glycogen, except a few fibres in an embryonic muscle which gave weak reactions for all enzymes. Histochemical fibre types were not formed. Two studies of explants of human muscle in association with normal embryonic mouse spinal cord resulted in the establishment of functional neuromuscular contact and the production of well striated myotubes, with peripherally placed nuclei and spontaneous regular contractions.     

EYE-SIGHTING PREFERENCE OF NORMAL AND HEMIPLEGIC CHILDREN AND ADULTS

Monocular eye-sighting preference was examined in 32 children with hemiplegia, 51 adult-onset hemiplegic patients and 57 normal children and adults. Eye preference was compared with ear preference on dichotic listening for 25 of the hemiplegic children. No independent association could be detected between eye preference and ear preference. In both the children and adults with hemiplegia the preferred eye tended to be on the same side as the damaged hemisphere. Among the adults, this tendency was more pronounced with more extensive lesions, as manifested by aphasia and/or hemianopia. These findings are interpreted as indicating that eye-sighting preference is unrelated to unitary hemispheric dominance, and that, unlike dominance for hearing and speech, it is not irreversible after a critical period of development. A simpler explanation than incomplete hemispheric dominance is offered for the weakly positive association between mixed laterality and cerebral dysfunction.