Letter and category fluency in patients with frontal lobe lesions.

This study examines the hypothesis that patients with frontal lobe lesions are impaired on tests of letter but not category fluency. This hypothesis was proposed by Moscovitch (1994), based on a series of cognitive studies with young, normal participants. A group of patients with lateral prefrontal lesions and age-matched controls were tested on 2 tests of verbal fluency, the FAS task and a category fluency task that used semantic categories as cues (e.g., animals). Patients with frontal lobe lesions generated fewer items than controls on both letter and category fluency. This effect did not interact with the type of fluency test, suggesting that the frontal lobes are more generally involved in verbal fluency. Moreover, this pattern of findings, along with previous results of impaired free recall and remote retrieval in this patient group, suggests that patients with frontal lobe lesions do not efficiently organize and develop retrieval strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal fluency deficits in Parkinson's disease.

Administered verbal (category naming, letter fluency) and nonverbal (category drawing, design fluency) tasks to patients with Parkinson's disease (PD). PD patients were significantly impaired only in their category naming for a semantic target like fruit. The hypothesis that compromised lexical retrieval contributed to PD patients' impaired category naming by examining free recall and recognition on a supraspan learning task was tested. PD patients were significantly impaired in free recall but not recognition. Category naming fluency correlated with free recall but not recognition on the supraspan learning task. It is argued that the verbal fluency deficit in PD is due to a lexical retrieval impairment and that the difference between category naming and letter fluency is due to the nature of the prompts for lexical retrieval that patients can derive from these tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence for intact semantic representations in patients with frontal lobe lesions.

Patients with frontal lobe lesions and control participants were assessed on 2 tests of semantic knowledge. In the triadic comparison task, participants were shown all possible triplets of 12 animal names and judged which 2 of each triplet were most alike. In the ordered similarity task, participants rank ordered animals in terms of their similarity to a target animal. For both tasks, semantic structure-- derived from multidimensional scaling techniques-- revealed similar representations in patients with frontal lobe lesions and control participants. Additional pathfinder analyses also produced networks that did not differ between groups. These patients exhibited intact semantic knowledge despite deficits on tests of free recall and verbal fluency that involved the same semantic category and exemplars. Thus, intact representation of semantic knowledge in frontal patients stands in contrast to their marked deficits in strategic retrieval of semantic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive resources and dual-task interference effects at retrieval in normal people: The role of the frontal lobes and medial temporal cortex.

Conducted 3 experiments to examine the hypothesis that concurrent secondary tasks at retrieval will interfere more with long-term, episodic memory functions involving the frontal lobes than those involving the medial temporal lobes hippocampus (MTL/H). The rationale is that strategic retrieval processes mediated by the frontal lobes place greater demands on cognitive resources than do relatively automatic associative retrieval processes (ecphory) mediated by the temporal lobes. In Exps 1 and 2, sequential finger tapping was performed at encoding, at retrieval, at both, or at neither. Recall of a categorized list of 16 words from the California Verbal Learning Test in Exp 1, and release from proactive inhibition (PI) in Exp 2, both being tests that involve the frontal lobes, were impaired if normal Ss tapped at both encoding and retrieval. Concurrent tapping had little effect on rate of learning in Exp 1 and on total words recalled during the buildup of PI in Exp 2, both of which are indices that are affected more by MTL/H than by frontal lesions. In Exp 3, tapping by normal Ss affected letter fluency, a test more sensitive to frontal lobe than temporal lobe damage, but not category fluency, for which the reverse is true. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbal fluency deficits in patients with schizophrenia: Semantic fluency is differentially impaired as compared with phonologic fluency.

Patients with schizophrenia show deficits in phonologic (ability to name words that begin with a specific letter, e.g., F) and semantic (ability to name members of a category, e.g., "animals" fluency.) Whereas the former deficit has been presumed to reflect a dysfunction of the frontal lobe, the latter has been linked to frontal and temporoparietal brain areas. These 2 verbal fluency measures were studied in a sample of 27 schizophrenia patients and 24 normal controls who were matched on age and a putative measure of premorbid intellectual ability. A 2-min production task of switching between letters and between categories measured demand for flexibility. On switching and nonswitching tasks controls produced more words during semantic versus phonologic fluency. Conversely, schizophrenia patients produced more words for letters than for categories, suggesting dysfunction of the frontal and temporoparietal areas of the brain. Furthermore, the greater impairment of semantic fluency may be related to a breakdown of semantic information processing beyond "executive" search and retrieval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conceptual and perceptual implicit memory in Huntington's disease.

The aims of this study were to examine and compare perceptual and conceptual implicit memory (CIM) in Huntington's disease (HD) and to characterize the relationship between tests of frontal lobe functioning and CIM. Sixteen HD patients and 16 normal controls completed structurally parallel tests of perceptual implicit memory and CIM (i.e., rhyme and category exemplar generation), tests of explicit memory, and verbal fluency. HID patients showed intact implicit memory for both rhyme and category exemplars, despite evidence of frontal dysfunction on other tests. An unexpected finding was that patients showed a deficit in cued rhyme generation that correlated with severity of neurological impairment. The authors replicated findings in controls of a correlation between letter fluency and CIM but found no relationship in patients. Frontal dysfunction in HID may lessen the influence of generative strategies on tests of CIM without compromising performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Semantic fluency in Alzheimer's, Parkinson's, and Huntington's disease: Dissociation of storage and retrieval failures.

Patients with Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and normal controls were compared on 2 versions of a semantic fluency task: a standard, uncued version and a version in which Ss were cued with subordinate categories. All patients were impaired relative to controls on the standard version. On the cued version, PD and HD patients improved significantly, but AD patients did not. AD patients' fluency, but not PD or HD patients', correlated significantly with confrontation naming ability. Impairment exhibited by PD and HD patients on standard semantic fluency tasks may be due to a retrieval deficit, whereas that of AD patients may be due to degradation of semantic memory stores. In addition, the pattern of performance exhibited by a nonaphasic patient with bilateral frontal lobe lesions suggests that the retrieval functions involved may depend on integrity of the prefrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working Memory and Perseveration in Verbal Fluency.

Letter and semantic fluency tasks are often used in neuropsychological assessment and are sensitive to many conditions. Performance is assessed by correct responses and errors, including perseverations. Healthy young adults performed letter and semantic fluency tasks. One group performed these tasks in the conventional manner; 2 other groups performed them while maintaining memory loads. The memory loads consisted either of words from the same category as the fluency task or of words from a different category. The results showed little effect of memory loads on correct responses but significant effects of memory load on perseveration rates: Same-category loads resulted in higher rates, especially in letter fluency. The results are discussed in terms of frontal lobe function in verbal fluency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Meta-Analytic Review of Verbal Fluency Performance in Patients With Traumatic Brain Injury.

A meta-analysis of 30 studies with 1,269 participants was conducted to investigate the sensitivity of tests of verbal fluency to the presence of traumatic brain injury (TBI). As has been found for patients with focal frontal lobe injuries (but not for patients with focal temporal lobe lesions), TBI patients were comparably impaired on tests of phonemic and semantic fluency. The phonemic fluency deficit could not be accounted for by patients' level of premorbid or current verbal IQ and was also substantially (although not significantly) in excess of the deficit on a measure of psychomotor speed. Phonemic fluency was also significantly more sensitive to the presence of TBI than was the Wisconsin Card Sorting Test (R. K. Heaton, 1981). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Meta-Analytic Review of Verbal Fluency Deficits in Huntington's Disease.

A meta-analysis of 30 studies with 1,511 participants was conducted to estimate and compare the magnitude of deficits on tests of phonemic and semantic fluency for patients with Huntington's disease (HD) relative to healthy control participants. As has been found for patients with focal frontal cortical lesions (but not for patients with focal temporal cortical lesions), symptomatic HD patients were comparably impaired on tests of phonemic and semantic fluency (rs=.71 and .73, respectively). However, in contrast to patients with focal frontal lobe injuries, fluency deficits did not qualify as differential deficits relative to verbal intelligence or psychomotor speed. Therefore, for patients with HD, deficits on tests of phonemic and semantic fluency do not appear to reflect executive dysfunction but a more generalized cognitive impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of category and letter fluency in Alzheimer's disease and Huntington's disease.

44 patients with dementia of the Alzheimer type (DAT), 44 elderly normal control (ENC) Ss demographically matched to the DAT group, 42 patients with Huntington's disease (HD), and 42 middle-aged normal control (MNC) Ss demographically matched to the HD group were administered letter and category fluency tasks. DAT patients showed an overproportional impairment on category than on letter fluency tasks, whereas HD patients were equally impaired. Analyses based on receiver operating characteristic curves revealed that category fluency correctly classified significantly more DAT and ENC Ss than did letter fluency, whereas the 2 fluency tasks did not differ in this respect for HD and MNC Ss. Results suggest that HD patients' failures on fluency tasks are caused by impaired initiation/retrieval capacities. In contrast, DAT patients' greater category than letter fluency deficits are primarily due to a breakdown in the structure of semantic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dual-task performance in dysexecutive and nondysexecutive patients with a frontal lesion.

Patients with defined frontal lobe lesions were assigned to 1 of 2 groups based on whether they showed a behaviorally assessed dysexecutive syndrome or were behaviorally normal. All participants were tested on dual-task performance and on 2 tasks assumed to measure frontal lobe function, the Wisconsin Card Sorting Test and verbal fluency. The dysexecutive group differed significantly from the nondysexecutive in showing impaired capacity for dual-task coordination, but there were no significant differences on the Wisconsin Card Sorting Test and verbal fluency. Results are interpreted in terms of a multicomponent central executive, whose function is linked to, but not coterminous with, the operation of the frontal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Commonalities and differences in the working memory components underlying letter and category fluency tasks: A dual-task investigation.

This study used a dual-task interference paradigm to test the hypothesis that different subcomponents of working memory differentially contribute to performance on letter fluency and category fluency tasks. College students (N = 96) performed each type of verbal fluency task in isolation and concurrently with I of 3 secondary tasks. The secondary tasks were chosen for their putative involvement in different working memory subcomponents. Two subsystems of working memory, the phonological loop and the visuospatial sketchpad, were identified as important contributors to fluency performance, especially to performance on letter fluency and category fluency tasks, respectively. Moreover, the results also suggest that the executive function, mental set shifting, may be deployed to perform both letter fluency and category fluency tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological effects of closed head injury in older adults: A comparison with Alzheimer's disease.

In this study, neuropsychological profiles of 14 older adult patients with mild or moderate closed head injury (CHI). 14 patients with probable Alzheimer's disease (AD), and 14 community residing elderly controls were compared. The groups were similar in demographic features, and the CHI and AD patients had comparable Mini-Mental State Examination scores. Tests of verbal learning and memory, letter and category fluency, and naming were administered. Relative to the CHI group, AD patients exhibited more devastated memory and did not show a normal facilitation on the category retrieval task. The patient groups exhibited similar levels of categorical clustering and naming accuracy for both high- and low-frequency words. These results suggest that neuropsychological markers of memory and semantic processing may be useful in differentiating the cognitive effects from AD versus early recovery from CHI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inaccurate prediction of retrieval in a face matrix learning task after right frontal lobe lesions.

This study partly supports the hypothesis that frontal lobe lesions cause impairment of metamemory. Fifty-nine patients with a focal brain lesion and 21 non-brain-damaged patients memorized a 4?×?4 matrix of 16 faces in 6 consecutive trials and predicted the number of locations of faces they would be able to remember before each retrieval. When age-related impairment of learning was adjusted, the patients with right posterior lesions were inferior to the controls and to the patients with right frontal lesions on the total number of correctly placed faces. The patients with right frontal lesions were less accurate than the patients with right posterior lesions or the controls in the prediction of retrieval. The inaccuracy of retrieval prediction in the face test was associated with that in a word-list learning task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychological correlates of short-term memory distractor tasks among patients with surgical repair of anterior communicating artery aneurysms.

The relative utility of the visual consonant trigram (VCT) and release from proactive inhibition (PI) versions of the short-term memory (STM) distractor task in investigating the separate but related cognitive realms of memory and executive frontal lobe functioning were explored in patients with anterior communicating artery (ACoA) aneurysms n?=?24. Compared with normal controls n?=?19, ACoA patients were impaired on clinical measures of memory and on measures of executive functioning, including concept formation and fluent word generation. Furthermore, ACoA patients were impaired on the VCT task but not on the release-from PI task, indicating a differential sensitivity of these tasks to the impairment manifested by ACoA patients. Regression modeling indicated that the VCT and release-from-PI tasks were closely associated with clinical memory tests, although the release-from-PI-task was also associated with fluency, an executive functioning domain. In general, our results fail to support the broad generalization that impaired performance on STM distractor tasks is necessarily symptomatic of frontal lobe dysfunction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hemispheric asymmetries in category-specific word retrieval

We examined whether 53 adult non-aphasic patients with either left (22) or right temporal lobe lesions (31) demonstrate dissociable patterns of hemispheric asymmetries in category-specific word fluency tasks. The patients were asked to articulate as many appropriate words as possible within 60 or 90 s in response to six target categories. There was no effect of patient groups on the overall fluency. However, patients with a left-sided temporal lobe lesion were impaired retrieving words to 'initial letters' and to the category 'animals'. Right temporal lobe patients were impaired retrieving 'tools' and words referring to specific visual attributes. There were no fluency differences for 'food-supermarket goods' and 'flat interior'. We conclude that temporal lobe damage can result in category-specific impairments in word retrieval depending on the affected hemisphere.     

Impaired retrieval from remote memory in patients with frontal lobe damage.

Patients with unilateral dorsolateral frontal lobe lesions and matched controls were given 2 tests of remote memory for public information, the Public Events Test and the Famous Faces Test. On both tests, the patients with frontal lobe lesions exhibited impaired recall for remote information. Recognition memory was relatively preserved. Provision of semantic and phonemic cues in the Famous Faces Test did not completely compensate for their recall deficit. These findings suggest that the remote memory impairment exhibited by frontal patients may be related to deficits in strategic search of memory. These deficits in retrieval from remote memory extend the array of memory deficits associated with damage to the frontal lobes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impaired generation and use of strategy in schizophrenia: evidence from visuospatial and verbal tasks

BACKGROUND: The aim of this study was to investigate mnemonic strategic deficits in schizophrenic patients. METHODS: Analogous tasks were used that required the self-generation of an efficient strategy and its implementation in two domains: visuospatial and verbal. The tasks were given to 20 IQ preserved schizophrenics and 20 matched normal controls. A number of different scores was derived from each task including strategy, short-term memory capacity and perseveration. RESULTS: Overall, the schizophrenic patients were significantly impaired in their ability to generate effective mnemonic strategies on both tasks. In addition, on the visuospatial task there was no difference between the groups on the memory scores, but the schizophrenic patients made significantly more perseverative errors than controls. They were disproportionately worse on the verbal strategy task, showing impairment on memory as well as on strategy scores and were also impaired at semantically classifying the words. Performance was similar to the deficit seen in patients with frontal lobe excisions and Parkinson's disease, in terms of the inability to generate an effective strategy. The deficit on the verbal task was similar to patients with temporal lobe excisions who show impaired verbal memory. However, the pattern differed in the sense that the temporal lobe patients were able to generate effective strategies, unlike the patients with schizophrenia. CONCLUSIONS: High functioning schizophrenic patients are impaired in utilizing visuospatial and verbal mnemonic strategies. By comparing the results with those of neurosurgical excision patients, further evidence is provided for both frontal and temporal lobe involvement in schizophrenia.     

Temporal and spatial context memory in patients with focal frontal, temporal lobe, and diencephalic lesions

Patients with focal frontal, temporal lobe, or diencephalic lesions were investigated on measures of temporal (recency) and spatial (position) context memory, after manipulating exposure times to match recognition memory for targets (pictorial stimuli) as closely as possible. Patients with diencephalic lesions from an alcoholic Korsakoff syndrome showed significant impairment on the temporal context (recency) task, as did patients with frontal lesions penetrating the dorsolateral frontal cortex, according to MRI (and PET) evidence. Patients with temporal lobe lesions showed only a moderate (non-significant) impairment on this task, and patients with medial frontal lesions, or large frontal lesions not penetrating the dorsolateral cortical margins, performed as well as healthy controls at this task. On the spatial context memory task, patients with lesions in the temporal lobes showed significant impairment, and patients with right temporal lesions performed significantly worse than patients with left temporal lesions. Patients with diencephalic lesions showed only a modest (non-significant) impairment on this task, and the frontal lobe group performed normally. When a group of patients with temporal lobe lesions resulting from herpes encephalitis were examined separately, an identical pattern of results was obtained, the herpes group being significantly impaired on spatial memory and showing a trend towards impairment for temporal context memory. There were strong correlations between anterograde memory quotients and context memory performance (despite the use of an exposure time titration procedure) and a weak association in the frontal group with one frontal/executive task [corrected] (card-sorting perservations). It is predicted that correlations between temporal context memory and frontal/executive tasks will be greater in samples of patients all of whom have frontal lesions invading the dorsolateral cortical margin.