Naida L. Graham

Charting the progression in semantic dementia: implications for the organisation of semantic memory.

Abstract A patient, JL, with the syndrome of semantic dementia was assessed longitudinally over a two-year period. The data presented here address the controversy concerning the hierarchical organisation of semantic memory. On a range of category fluency tests, when first tested JL was just within the normal range on the broadest categories of animals and household items, but was virtually unable to produce any instances of specific categories such as breeds of dog or musical instruments. Longitudinal fluency data for the animal category demonstrate that while JL continued to produce the most prototypical responses (cat, dog, horse), other animal labels dropped out early from his vocabulary. On the picture-sorting tests from our semantic memory test battery, JLs discrimination between living things and man-made objects was preserved for a substantial time in conjunction with a marked decline in his sorting ability for more specific categories, particularly features or attributes (e.g. size, foreign-ness,...

The impact of semantic memory loss on phonological representations

Three patients with semantic dementia, involving progressive deterioration of semantic memory, performed immediate serial recall of short sequences of familiar words. On the basis of their performance in other tasks of word comprehension and production, the stimuli were selected individually for each patient as either known or unknown words. All patients showed a marked advantage in recall of known as compared to familiar but now unknown words. Errors consisted primarily of incorrect combinations of correct phoneme sequences in the stimulus string, with a large number of errors preserving onsethime syllable structure (e.g., mint, rug reproduced as rint, mug). Discussion focuses on the implication of these errors for the structure of phonological representations, and in particular on a hypothesis that meaning plays a crucial role in binding the elements of phonological word forms.

Naming and Knowing in Dementia of Alzheimer's Type

We studied the relationship between naming and the integrity of physical and associative knowledge in a group of patients with dementia of the Alzheimer type (DAT) and matched normal controls. All subjects named 48 line drawings and later generated verbal definitions in response to the names of a subset of the 48 items, which included a minimum of six definitions for correctly named objects and six definitions for items that the subject failed to name. A comprehensive scoring system was designed for the definitions, including physical and associative features of a general and a specific type, a superordinate label, the core concept, and various categories of errors. The definitions generated by the DAT patients, even those in the minimal group, contained significantly less correct information than those of normal subjects, and definitions corresponding to unnamed items were more impoverished than those for named items. Particularly striking was the loss of core concept for unnamed items. There was also a disproportionate reduction in physical information on unnamed compared to named items. We conclude that quantitative assessment of verbal definitions is a sensitive index of semantic memory breakdown. Our findings offer some support for the hypothesis that successful naming depends upon integrity of the subset of semantic knowledge comprising physical features.

Corticobasal degeneration as a cognitive disorder

The presence of cognitive impairment in corticobasal degeneration (CBD) is now widely recognised. Our review of the literature reveals that, although the pattern and severity of neuropsychological impairments can be highly variable across patients, several general trends can be identified. The most characteristic impairments are limb apraxia (usually ideomotor), constructional and visuospatial difficulties, acalculia, frontal dysfunction, and nonfluent aphasia. The limb apraxia is associated with deficits in drawing, copying, and handwriting, but there is emerging evidence that the problems with handwriting are not due exclusively to the apraxia. The findings with respect to episodic memory are more variable, but when there is impairment in this area, it tends to be milder than that seen in Alzheimers disease. Semantic memory functioning appears relatively preserved but has been poorly studied. Problems with speech are common, and may be due to dysarthria or buccofacial apraxia. Aphasia, although initially considered rare, is in fact a common accompaniment of CBD, may be the presenting feature, and is typically nonfluent in type. More systematic investigation of the clinical and neuropathological overlap between progressive nonfluent aphasia (generally considered to be a form of frontotemporal dementia) and CBD is needed.© 2003 Movement Disorder Society

The impact of semantic memory impairment on spelling: evidence from semantic dementia

We assessed spelling and reading abilities in 14 patients with semantic dementia (with varying degrees of semantic impairment) and 24 matched controls, using spelling-to-dictation and single-word reading tests which manipulated regularity of the correspondences between spelling and sound, and word frequency. All of the patients exhibited spelling and reading deficits, except at the very earliest stages of disease. Longitudinal study of seven of the patients revealed further deterioration in spelling, reading, and semantic memory. The performance of both subject groups on both spelling and reading was affected by regularity and word frequency, but these effects were substantially larger for the patients. Spelling of words with exceptional (or more precisely, unpredictable) sound-to-spelling correspondences was most impaired, and the majority of errors were phonologically plausible renderings of the target words. Reading of low frequency words with exceptional spelling-to-sound correspondences was also significantly impaired. The spelling and reading deficits were correlated with, and in our interpretation are attributed to, the semantic impairment.

Language function and dysfunction in corticobasal degeneration

Objectives: The authors assessed language functioning in corticobasal degeneration (CBD), an area that has received little systematic study. Aphasia has been reported occasionally, and the authors hypothesized that appropriate assessments would reveal at least mild language impairment, particularly affecting phonologic (sound-based) processing, even in cases without frank aphasia. Methods: A series of 10 unselected patients with CBD (one with pathologic confirmation) were administered neuropsychological tests assessing the following aspects of cognitive functioning: verbal fluency, naming, reading, oral spelling, auditory-verbal short-term memory, phoneme blending and segmentation, visuospatial skills, and semantic memory. Results: Phonologic and spelling impairments were prevalent, even in nonaphasic patients. The prevalence of visuospatial, constructional, and frontal impairments, demonstrated in previous research, was also replicated. A minority of patients had deficits in semantic memory, naming, and reading, but the impairments were usually mild. Conclusions: The authors found phonologic impairment to be a typical feature of CBD. There is substantial overlap between progressive nonfluent aphasia and CBD, and the linguistic impairment can be thought of as a continuum, with mild phonologic impairment at one end and severe aphasia at the other.

When More Yields Less: Speaking and Writing Deficits in Nonfluent Progressive Aphasia

Fourteen patients with nonfluent progressive aphasia (NFPA) performed a picture description task in both spoken- and written-output conditions, as well as tests of confrontation naming, spelling to dictation and reading aloud of single words and text. Relative to controls, the patients’ spoken and written picture descriptions were reduced in length, speed and amount of information. Of particular interest, and accounting for the first part of the article’s title, was a pervasive pattern of poorer spoken and written output associated with the requirement to produce more; this was true when ‘more’ meant either (a) longer vs. shorter single words or (b) connected language vs. single words. Deficits in spoken and written naming were largely parallel, and modality-specific output impairments (such as dysarthria in speech or letter-formation problems in writing) seemed to account for the minority of cases who exhibited a discrepancy. Most patients showed no evidence of agrammatism or of reduced verb production in their speech, which typically had normal proportions of content and function words as well as nouns and verbs. By contrast, some degree of telegraphic output was observed in the written narratives of a number of the patients. Our results argue against several candidates for the main functional locus of impairment in NFPA, but it is likely that deficits in grammatical processing, working memory, planning/executive skills, speech motor abilities and phonological processing all play a role.

Dyspraxia in a patient with corticobasal degeneration: the role of visual and tactile inputs to action

OBJECTIVES To investigate the roles of visual and tactile information in a dyspraxic patient with corticobasal degeneration (CBD) who showed dramatic facilitation in miming the use of a tool or object when he was given a tool to manipulate; and to study the nature of the praxic and neuropsychological deficits in CBD. METHODS The subject had clinically diagnosed CBD, and exhibited alien limb behaviour and striking ideomotor dyspraxia. General neuropsychological evaluation focused on constructional and visuospatial abilities, calculation, verbal fluency, episodic and semantic memory, plus spelling and writing because impairments in this domain were presenting complaints. Four experiments assessed the roles of visual and tactile information in the facilitation of motor performance by tools. Experiment 1 evaluated the patient’s performance of six limb transitive actions under six conditions: (1) after he described the relevant tool from memory, (2) after he was shown a line drawing of the tool, (3) after he was shown a real exemplar of the tool, (4) after he watched the experimenter perform the action, (5) while he was holding the tool, and (6) immediately after he had performed the action with the tool but with the tool removed from his grasp. Experiment 2 evaluated the use of the same six tools when the patient had tactile but no visual information (while he was blindfolded). Experiments 3 and 4 assessed performance of actions appropriate to the same six tools when the patient had either neutral or inappropriate tactile feedback—that is, while he was holding a non-tool object or a different tool. RESULTS Miming of tool use was not facilitated by visual input; moreover, lack of visual information in the blindfolded condition did not reduce performance. The principal positive finding was a dramatic facilitation of the patient’s ability to demonstrate object use when he was holding either the appropriate tool or a neutral object. Tools inappropriate to the requested action produced involuntary performance of the stimulus relevant action. CONCLUSIONS Tactile stimulation was paramount in the facilitation of motor performance in tool use by this patient with CBD. This outcome suggests that tactile information should be included in models which hypothesise modality specific inputs to the action production system. Significant impairments in spelling and letter production that have not previously been reported in CBD have also been documented.

Progressive Dysgraphia: Co-occurrence of Central and Peripheral Impairments

We studied two patients with a novel focal neurodegenerative syndrome: a progressive dysgraphia in which both central (linguistic) and peripheral aspects of the writing process were affected. In one patient the dysgraphia was remarkably pure. Longitudinal testing over roughly 4 years showed that the dysgraphia evolved in a broadly similar pattern for both patients. At presentation, SC and FM exhibited (central) surface dysgraphia on both oral and written spelling. Over time, nonphonologically plausible spelling errors increased, and eventually became the dominant response type for both patients in both response modes. The peripheral dysgraphia consisted of difficulty with producing letters, particularly in lower case, without a model to copy. Examination of a further 28 dysgraphic patients with cortical dementia revealed a strong concordance between spelling and letter production problems, indicating that the association is more common than previously recognised. Although this association may simply refle...

Progressive non-fluent aphasia is not a progressive form of non-fluent (post-stroke) aphasia

Background: The speech of patients with progressive non-fluent aphasia (PNFA) has been described as similar to that in non-fluent aphasia (NFA) consequent on stroke. There are, however, few direct empirical comparisons of these two patient populations in the literature. Aims: To test the hypotheses that PNFA cases differ from NFA (a) in the extent to which their speech production deficit varies as a function of speaking task, and (b) in the nature of their phonological deficit. Methods & Procedures: Groups of PNFA and NFA patients (N = 10 each), matched on scores in a picture-naming test, were assessed on tasks of narrative picture description, reading aloud of text and single words, and phonological abilities such as rhyme judgement and rhyme production. Outcomes & Results: (a) The NFA cases showed equivalent speech rates in self-generated speech and reading text aloud, and equivalent error rates when reading text or isolated single words. In contrast, the PNFA cases spoke more rapidly when reading aloud than when producing narrative speech, and achieved higher accuracy when reading single words aloud than when reading words in text. (b) Variation in success rate for reading different types of words (e.g., content words, function words, and nonsense words), error types in reading, and performance on phonological tasks all indicated a different and better quality of phonological processing in PNFA than NFA. Conclusions: Despite some surface similarities, there are telling differences between the speech impairments in PNFA and NFA. The deficit in PNFA particularly compromises self-generated connected speech.