Premature thoughts on writing disorders

Three papers appeared in the 19th century describing the dissociation between speech and writing: Marce (1856), Ogle (1867) and Pitres (1884). An account of the convincing evidence of dissociations put forward in these papers is presented. Three explanations are proposed as to the reason why the observations reported by these authors were overlooked or rejected by their contemporaries, namely: (a) in the first half of the century it seems that very little knowledge of the processes underlying writing (as opposed to speech) was available, (b) the debates focussed on the independence of speech versus motor control and language versus the intellect, (c) parallelisms between phylogeny, ontogeny and aphasia impeded the application of the principle of double dissociations, including the dissociations between speech and writing. It is argued that this phenomenon in the history of aphasia is best captured by the concept of prematurity in scientific discovery proposed by Stent (1972, 2003)

The history of written language disorders: reexamining Pitres’ case (1884) of pure agraphia

The first clinical description of pure agraphia was reported by the French neurologist Pitres in 1884. Pitres used the case study evidence to argue for modality-specific memory representations and the localization of writing. This article reviews Pitres’s contribution to the study of acquired writing disorders, the components of writing models and the cerebral localization which subserve writing, in light of the views entertained by his contemporaries and current authors. Although numerous cases have been reported throughout this century, the view that writing can be impaired while other language functions and motor activities remain intact is still challenged

Priming and Multiple Memory Systems: Perceptual Mechanisms of Implicit Memory

Research examining the relation between explicit and implicit forms of memory has generated a great deal of evidence concerning the issue of multiple memory systems. This article focuses on an extensively studied implicit memory phenomenon, known as direct or repetition priming, and examines the hypothesis that priming effects on various tasks reflect the operation of a perceptual representation system (PRS)—a class of cortically based subsystems that operate at a presemantic level and support non conscious expressions of memory. Three PRS subsystems are examined: visual word form, structural description, and auditory word form. Pertinent cognitive, neuropsychological, and neurobiological evidence is reviewed, alternative classificatory schemes are discussed, and important conceptual and terminological issues are considered.Psycholog

Disorders of Pitch Production in Tone Deafness

Singing is as natural as speaking for the majority of people. Yet some individuals (i.e., 10–15%) are poor singers, typically performing or imitating pitches and melodies inaccurately. This condition, commonly referred to as “tone deafness,” has been observed both in the presence and absence of deficient pitch perception. In this article we review the existing literature concerning normal singing, poor-pitch singing, and, briefly, the sources of this condition. Considering that pitch plays a prominent role in the structure of both music and speech we also focus on the possibility that speech production (or imitation) is similarly impaired in poor-pitch singers. Preliminary evidence from our laboratory suggests that pitch imitation may be selectively inaccurate in the music domain without being affected in speech. This finding points to separability of mechanisms subserving pitch production in music and language

Deafness for the meanings of number words

We describe the performance of an aphasic individual who showed a selective impairment affecting his comprehension of auditorily presented number words and not other word categories. His difficulty in number word comprehension was restricted to the auditory modality, given that with visual stimuli (written words, Arabic numerals and pictures) his comprehension of number and non-number words was intact. While there have been previous reports of selective difficulty or sparing of number words at the semantic and post-semantic levels, this is the first reported case of a pre-semantic deficit that is specific to the category of number words. This constitutes evidence that lexical semantic distinctions are respected by modality-specific neural mechanisms responsible for providing access to the meanings of words

Are developmental disorders like cases of adult brain damage? Implications from connectionist modelling

It is often assumed that similar domain-specific behavioural impairments found in cases of adult brain damage and developmental disorders correspond to similar underlying causes, and can serve as convergent evidence for the modular structure of the normal adult cognitive system. We argue that this correspondence is contingent on an unsupported assumption that atypical development can produce selective deficits while the rest of the system develops normally (Residual Normality), and that this assumption tends to bias data collection in the field. Based on a review of connectionist models of acquired and developmental disorders in the domains of reading and past tense, as well as on new simulations, we explore the computational viability of Residual Normality and the potential role of development in producing behavioural deficits. Simulations demonstrate that damage to a developmental model can produce very different effects depending on whether it occurs prior to or following the training process. Because developmental disorders typically involve damage prior to learning, we conclude that the developmental process is a key component of the explanation of endstate impairments in such disorders. Further simulations demonstrate that in simple connectionist learning systems, the assumption of Residual Normality is undermined by processes of compensation or alteration elsewhere in the system. We outline the precise computational conditions required for Residual Normality to hold in development, and suggest that in many cases it is an unlikely hypothesis. We conclude that in developmental disorders, inferences from behavioural deficits to underlying structure crucially depend on developmental conditions, and that the process of ontogenetic development cannot be ignored in constructing models of developmental disorders