Peripheral dysgraphia: dissociations of lowercase from uppercase letters and of print from cursive writing.

Clinical analyses of patients with acquired dysgraphia provide unique opportunities to understand the cognitive and neural organization of written language production. We report J.B., a 50-year-old woman with peripheral dysgraphia who had prominent dissociations in her ability to write in lowercase versus uppercase and print versus cursive. We gave J.B. a series of tasks that evaluated her skills at writing uppercase and lowercase print and cursive, spelling aloud and in writing, writing numbers and symbols, and visual letter recognition and imagery. She was impaired in printing letters, with lowercase more affected than uppercase, but her cursive writing was relatively intact. This pattern was consistent across letter, word, and nonword writing tasks. She was unimpaired on tasks assessing her visual recognition and imagery of lowercase and uppercase letters. Her writing of numbers was preserved. J.B.'s handwriting disorder was accompanied by a central phonological dysgraphia. Our findings indicate functional independence of graphomotor programs for print and cursive letter styles and for letters and numbers. We discuss the relationship between peripheral and central writing disorders.

A comparison of letter and digit processing in letter-by-letter reading.

The extent to which letter-by-letter reading results from a specific orthographic deficit, as compared with a nonspecific disturbance in basic visuoperceptual mechanisms, is unclear. The current study directly compared processing of letters and digits in a letter-by-letter reader, G.M., using a rapid serial visual presentation (RSVP) task and a speeded matching task. Comparisons were made to a group of six brain-damaged individuals without reading deficits. In the RSVP task, G.M. had increased difficulty reporting the target identities when they were letters, as compared with digits. Although this general pattern was also evident in the control group, the magnitude of the letter-digit accuracy difference was greater in G.M. Similarly, in the matching task, G.M. was slower to match letters than digits, relative to the control group, although his response times to both item types were increased. These data suggest that letter-by-letter reading, at least in this case, results from a visuoperceptual encoding deficit that particularly affects letters, but also extends to processing of digits to a lesser extent. Results are consistent with the notion that a left occipitotemporal area is specialized for letter processing with greater bilaterality in the visual processing of digits.

Progressive anomia without semantic or phonological impairment.

We describe a 59-year-old woman, M.T., with a progressive language impairment and neuroimaging findings of decreased perfusion (SPECT) and focal atrophy (MRI) in the left temporal region. The most prominent feature of her cognitive profile was a profound and progressive impairment in naming. In spite of this, she performed normally on tests of semantic processing and phonological output. Her spontaneous speech was fluent with preserved syntax and articulation but with notable word-finding problems. All other cognitive abilities were relatively stable and intact. These features are not typical of either fluent or non-fluent forms of neurodegenerative language disturbance. The cognitive mechanisms that may underlie this case are discussed.

Preclinical vascular cognitive impairment and Alzheimer disease: neuropsychological test performance 5 years before diagnosis.

BACKGROUND AND PURPOSE: Neuropsychological changes that precede a diagnosis of vascular cognitive impairment (VCI) and the differences between preclinical VCI and Alzheimer disease (AD) are not well understood. We compared the neuropsychological performances of people with incident VCI, incident AD, and no cognitive impairment (NCI) 5 years before their clinical diagnoses. METHODS: The Canadian Study of Health and Aging is a prospective, cohort study of 10,263 randomly selected persons age 65 years or older. We studied 332 individuals who had completed a battery of neuropsychological tests and were diagnosed with NCI at baseline. After 5 years, 41 were diagnosed with VCI, 25 with AD, and 266 with NCI. RESULTS: At baseline, the incident-VCI group performed worse on a wide range of neuropsychological tests compared with the NCI group. A test of abstract reasoning was selectively low in the incident-VCI group, relative to both the incident-AD and NCI groups. The incident-AD group performed worse at baseline on memory tests compared with incident-VCI and NCI groups. CONCLUSIONS: This study suggests a preclinical phase may exist in VCI that differs from that in AD. Neuropsychological measures may aid the design of preventive strategies for VCI.

Temporal processing deficits in letter-by-letter reading.

Theories of the cognitive impairment underlying letter-by-letter reading vary widely, including prelexical and lexical level deficits. One prominent prelexical account proposes that the disorder results from difficulty in processing multiple letters simultaneously. We investigated whether this deficit extends to letters presented in rapid temporal succession. A letter-by-letter reader, G.M., was administered a rapid serial visual presentation task that has been used widely to study the temporal processing characteristics of the normal visual system. Comparisons were made to a control group of 6 brain-damaged individuals without reading deficits. Two target letters were embedded at varying temporal positions in a stream of rapidly presented single digits. After each stream, the identities of the two letters were reported. G.M. required an extended period of time after he had processed one letter before he was able to reliably identify a second letter, relative to the controls. In addition, G.M.'s report of the second letter was most impaired when it immediately followed the first letter, a pattern not seen in the controls, indicating that G.M. had difficulty processing the two items together. These data suggest that a letter-by-letter reading strategy may be adopted to help compensate for a deficit in the temporal processing of letters.

Disconnection of language and memory in semantic dementia: a comparative and theoretical analysis.

In this paper, we present an illustrative case of Semantic Dementia (SD) and we review the literature on this relatively rare progressive neurodegenerative disorder. After reviewing the clinical, neuroimaging, neuropathological, and genetic features of SD, we propose a theoretical framework that addresses features of SD and relates them to features of other well known neuropsychiatric syndromes. Our 'on-line / off-line disconnection' model seeks to conceptualize SD as a syndrome of disconnection between two large distributed cortical networks, namely, between those networks that subserve language function and those that subserve memory function.

Five-year outcomes for dementia defined solely by neuropsychological test performance.

Cognitive impairment that does not meet criteria for dementia is common and progresses to dementia at a high rate. It is not clear how best to define this type of cognitive impairment. We assessed the predictive validity of different case definitions for cognitive impairment and dementia by comparing rates of adverse outcomes for individuals who did not meet dementia criteria but had neuropsychological test results indicating dementia (NPDementia), those who had traditional dementia diagnoses (mild and moderate-severe severity), those who had other cognitive impairment but no dementia (CIND), and those with no cognitive impairment (NCI). Our sample comprised 1,659 participants who had completed a neuropsychological assessment in the Canadian Study of Health and Aging, a prospective, cohort study of 10,263 randomly selected persons aged 65 years or older. Outcomes were determined after 5 years. Institutionalization and death rates for the NPDementia and CIND groups were higher than for the NCI group. Both groups had lower institutionalization rates than the two Dementia groups and lower death rates than the Moderate-Severe Dementia group. Rates of progression to dementia were increased in NPDementia and CIND groups, relative to the NCI group, and the NPDementia group was less likely than the CIND group to revert to a diagnosis of NCI at the 5-year follow-up. Thus, individuals with NPDementia and CIND have substantially worse outcomes over 5 years than those with NCI. The case definition of NPDementia identified individuals with cognitive impairment that is unlikely to resolve and likely to progress to dementia.

Neuropsychological predictors of incident dementia in patients with vascular cognitive impairment, without dementia.

BACKGROUND: Vascular cognitive impairment that does not fulfill dementia criteria (ie, vascular cognitive impairment, no dementia [CIND]) is common. Although progression to dementia is frequent, little is known about factors that predict progression. We examined whether performance on neuropsychological tests administered at baseline could predict incident cases of dementia in patients with vascular CIND after 5 years. Summary of Report- The Canadian Study of Health and Aging is a prospective, cohort study of 10 263 randomly selected persons aged > or =65 years. Of 149 people diagnosed with vascular CIND, 125 completed a battery of neuropsychological tests at baseline. Follow-up cognitive diagnoses were available for 102 individuals. After 5 years, 45 patients (44%) developed dementia. Low baseline scores on tests of memory and category fluency were associated with incident dementia. CONCLUSIONS: Neuropsychological measures can indicate risk of dementia in patients with vascular CIND. This study did not suggest a prediction-to-progression profile distinct from that seen in Alzheimer disease.