Categorization of novel animals by patients with Alzheimer's disease and corticobasal degeneration.

We taught a novel animal category by rule-based and similarity-based processes to participants with Alzheimer's disease (AD), corticobasal degeneration (CBD), and healthy age-matched participants. Healthy participants successfully categorized by either process. AD patients' rule-based categorization was impaired, while their similarity-based categorization resembled that of healthy participants. Correlations of AD patients' performance with measures of executive functioning suggested a deficit in the cognitive resources necessary for engaging rule-based categorization. The contribution of limited executive resources to categorization difficulty in AD was further demonstrated in a second experiment in which features determining category membership were of lower salience. CBD patients were relatively impaired at similarity-based processing, suggesting that qualitatively distinct categorization processes can be selectively compromised in patients with focal neurodegenerative diseases. Moreover, AD patients' impaired categorization correlated with performance on a measure of semantic memory, implicating this categorization deficit in AD patients' semantic memory difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Assessing visual memory disorders.

The Biber Figure Learning Test (BFLT) was administered to 19 patients with right- and 20 with left-hemisphere cerebrovascular accidents, 11 severe amnesics and 42 controls. Results indicate that the BFLT reliably assesses impairments in long-term visual memory independent of primary visuoperceptual, visuoconstructional, and language deficits. Healthy controls showed no effects of education and minimal age effects on the BFLT. Normal learning curves were found for cortical lesions patients, but their overall scores were below those of normals. Amnesics with subcortical-limbic pathology showed grossly impaired acquisition, retention, and recognition memory, but normal short-term visual memory and primary visuoperceptual/visuoconstructional abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age, executive functions, and visuospatial functioning in healthy older adults.

Visuospatial test performance declines with age, whereas verbal test performance remains fairly constant. This pattern has been attributed to an age-related decline in either right-hemisphere functioning or executive functions (EFs), which may be associated with prefrontal cortical decline. Timed and untimed EF tests, and visuospatial tests requiring substantial integrative skill (I-VS) or little or no integrative skill (non-I-VS) were administered to young-old (aged 74 yrs and younger) and old-old (aged 75 yrs and older) healthy volunteers. Groups differed on I-VS tests and on many EF tests but not on non-I-VS tests. I-VS tests correlated highly with tests of EFs, but non-I-VS tests did not. These results are interpreted as supporting the proposal that an age-related decline in EF underlies the decline in visuospatial test performance observed with advancing age. Other issues regarding the relationship between age and EF are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lexical semantic and associative priming in Alzheimer's disease.

Semantic memory impairment was investigated in patients with probable Alzheimer's disease (AD) using a threshold oral word reading task to assess priming of different lexical relationships. Healthy elderly controls showed significant priming for associatively related nouns (tempest-teapot) and also for nouns semantically related either because both designate basic-level exemplars of a common superordinate category (cousin-nephew) or because the target names the superordinate category of the prime (daughter-relative). AD patients, in contrast, showed preserved priming of lexical associates but impaired priming of certain semantic relationships. They showed no priming between words designating coordinate exemplars within a category, despite preserved priming of the superordinate category label. Findings are consistent with the view that at least part of the semantic deficit in AD is due to disruption of semantic knowledge that affects relationships among basic-level concepts, more than the relationships between these concepts and their corresponding superordinate category of membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural Basis for Verb Processing in Alzheimer's Disease: An fMRI Study.

Patients with probable Alzheimer's disease (AD) have difficulty understanding verbs. To investigate the neural basis for this deficit, the authors used functional magnetic resonance imaging to examine patterns of neural activation during verb processing in 11 AD patients compared with 16 healthy seniors. Subjects judged the pleasantness of verbs, including MOTION verbs and COGNITION verbs. Healthy seniors and AD patients both activated posterolateral temporal and inferior frontal regions during judgments of verbs. These activations were relatively reduced and somewhat changed in their anatomic distribution in AD patients compared with healthy seniors, particularly for the subcategory of MOTION verbs, but AD patients showed minimal activation in association with COGNITION verbs. These findings imply that poor performance with verbs in AD is due in part to altered activation of the large-scale neural network that supports verb processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clues to the cognitive organization of reading and writing from developmental hyperlexia.

Controversies regarding the organization of the cognitive systems used for processing written language were investigated in a case study of a mentally retarded hyperlexic child. Despite severe impairments in semantic processing, this child demonstrated intact phonological and orthographic processing. Detailed assessments of his nonword reading abilities provided support for the hypothesis that phonological processing of written words was accomplished by using lexical representations instead of applying nonlexical grapheme-phoneme transcoding rules. Longitudinal investigation of the hyperlexic child's development of writing supports the notion that reading and spelling rely on common mental representations rather than separate input and output mental lexicons. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neural organization of material-specific memory functions in temporal lobe epilepsy patients as assessed by the intracarotid amobarbital test.

Lateralization of material-specific memory processing was evaluated in 105 epilepsy patients undergoing the intracarotid amobarbital test prior to temporal lobectomy (TL). Left hemisphere (LH) language dominant patients demonstrated LH specialization for long-term verbal recognition memory and right hemisphere specialization for visuospatial recognition memory. The pattern of hemispheric memory specialization was similar for LH language dominant patients with brain injuries before 2 yrs of age and those without history of early brain injury, suggesting that the apparent sparing of memory post-TL in early brain injury patients reflects reorganization of memory functions within the epileptic hemisphere. Non-LH-language dominant patients showed no lateral specialization for either verbal or visuospatial memory processing, suggesting that in these individuals reorganization of memory functions between hemispheres accompanies the lateral shift in language representation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease.

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of reading and spelling in patients with probable Alzheimer's disease.

Patients with probable Alzheimer's disease (AD) are reported to show mild, but reliable, difficulties reading aloud and spelling to dictation exception words, which have unusual or unpredictable correspondence between their spelling and pronunciation (e.g., touch). To understand the cognitive dysfunction responsible for these impairments, 21 patients and 27 age- and education-matched controls completed specially designed tests of single-word oral reading and spelling to dictation. AD patients performed slightly below controls on all tasks and showed mildly exaggerated regularity effects (i.e., the difference in response accuracy between words with regular spellings minus exception words) in reading and spelling. Qualitative analyses, however, did not demonstrate response patterns consistent with impairment in central lexical orthographic processing. The authors conclude that the mild alexia and agraphia in AD reflect semantic deficits and nonlinguistic impairments rather than a specific disturbance in lexical orthographic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences between nouns and verbs after anterior temporal lobectomy.

To test the claim that lesions of left anterior and middle temporal cortical structures specifically impair processing of nouns but not verbs, 56 left-hemisphere-language-dominant patients who had undergone anterior temporal lobectomy (ATL) completed tasks assessing confrontation naming of pictured objects and actions, generation of synonyms for nouns and verbs, and semantic lexical judgments about nouns and verbs. Compared with right ATL patients left ATL patients were impaired across different tasks that assessed naming and comprehension of high-imageability as well as low-imageability nouns. These groups did not differ, however, in verb naming or comprehension on most tasks. Results are consistent with the hypothesized specialization of left temporal lobe structures for processing nouns and suggest that naming problems commonly seen after left ATL extend beyond difficulties with retrieving object names and may be related to subtle disturbances in comprehension of the meanings underlying nominal word forms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)