Central processing deficiencies in children: toward a developmental neuropsychological model.
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Adolescent↗
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Developmental aspects of linguistic and mnestic abilities in normal children.
The Peabody Picture Vocabulary Test-Revised (PPVT-R), Boston Naming Test (BNT), Paired Associate Learning of the Wechsler Memory Scale (PAL), and verbal fluency tests were administered to 241 normal children aged 6-12 years. Normative data were compiled for the BNT, PAL, and verbal fluency tests. A Principal Components Factor Analysis with Varimax Rotation was conducted to determine whether the tests evaluated similar or differential functions. Three factors emerged, accounting for 67.7% of the variance: Factor 1 contained loadings from two semantic fluency measures (animals and food), Factor 2 contained the PPVT-R and the BNT, and Factor 3 contained two measures from the PAL (easy and hard associations). In children, the BNT relates more to word knowledge than to retrieval or fluency, and verbal memory appears to be relatively independent of these linguistic functions.
Child↗
Conversational discourse abilities following severe traumatic brain injury: a follow-up study.
The major aim of this study was to describe the conversational abilities of a group of severely injured TBI speakers, at a minimum of 2 years post-injury. The association between conversational impairment and (a) selected measures of executive function and (b) psychosocial handicap was also examined. Twenty-four members of the group of 26 severely injured TBI speakers who had initially been assessed between 3 and 6 months post-injury were reviewed at a minimum of 2 years post-injury (mean = 2 years, 10 months). At initial assessment, TBI speakers were compared with non-TBI orthopaedic patients and with a group of university students. At follow-up, however, they were compared only with the orthopaedic patients. Conversational assessment was carried out using a modified form of Damico's Clinical Discourse Analysis. As a group, the TBI speakers' conversational abilities did not improve over time. There was, however, a subgroup (n = 8) of speakers who did improve, and these could be distinguished by greater initial severity of injury and a significantly longer period of speech-language pathology intervention than the speakers who either remained the same or worsened over time. Modest associations between conversational discourse skills and measures of executive function and a measure of psychosocial handicap were identified. These findings indicate that disruptions in conversation persist into the longer term. More assiduous efforts may need to be made to (a) identify subtle discourse changes in the early months after injury and (b) engage TBI speakers in speech-language pathology services. Such services are also required over a longer time frame, in community-based models of service provision.
Adolescent↗
Grammatical performance of children with language disorder on structured elicitation and narrative tasks.
The primary objective was to compare the grammatical output of children with language disorders on different tasks. Sixty-five children with language disorders, aged six to eleven, completed the syntactic formulation (elicitation) and narrative subtests from the Assessment of Comprehension and Expression 6-11 (Adams et al. 2001). Grammatical variables were computed for the narrative data and their relationship with the syntactic formulation subtest score examined. The use of ten specific constructions was compared in the two contexts. The syntactic formulation score correlated highly with narrative grammatical variables. However, for seven of the ten constructions, the elicitation task was more likely than the narrative to yield specific target structures. Structured elicitation is an efficient normative measure of grammatical production capacity. For specific structures, elicitation and narrative may give a different picture of output. Elicitation is more facilitative and may more closely reflect grammatical knowledge. Target structures were less likely to be used in the narrative, which reflects grammatical performance in a cognitively and linguistically demanding task.
Child↗
Children's reading of words, pseudohomophones, and other nonwords.
In Experiment 1 children aged 8-9 and 9-10 years were tested for neighbourhood and pseudohomophone effects in nonword reading. Neighbourhood effects (N effects) were robust irrespective of group or type of nonword. Pseudohomophones were read more accurately than other nonwords but this finding was robust only for the younger 8-9-year-olds. High-frequency words were read more accurately than low-frequency words, but the reverse applied to pseudohomophones based on high- and low-frequency words, although this was not robust. Error rates for the 9-10-year-olds in Experiment 1 were low, and so it was difficult to interpret the lack of a pseudohomophone advantage for reading nonwords in this age group. Experiment 2 was therefore carried out, which consisted of a replication of the first study with a further group of 9-10-year-olds, but pronunciation latencies were measured, as well as accuracy. All the effects obtained in Experiment 1 were replicated but, in addition, an advantage for pseudohomophones in terms of pronunciation latencies was observed. The implications for accounts of reading development are discussed.
Attention↗
Feedforward and feedback consistency effects for high- and low-frequency words in lexical decision and naming.
In three experiments, we examined feedforward and feedback consistency effects in word recognition. Feedforward consistency is the degree to which a word's pronunciation is consistent with that of similarly spelled words, and feedback consistency refers to whether there is more than one way to spell a pronunciation. Previously, Stone, Vanhoy, and Van Orden (1997) reported feedforward and feedback consistency effects for low-frequency words in a lexical decision task. We investigated the effect of feedforward and feedback consistency for both high- and low-frequency words in lexical decision and naming. In both tasks, we found that feedforward and feedback inconsistent words were processed more slowly than consistent words, regardless of word frequency. These findings indicate that both types of consistency are involved in visual word recognition.
Comprehension↗
Refractory effects in picture naming as assessed in a semantic blocking paradigm.
In the cyclic semantic blocking paradigm participants repeatedly name sets of objects with semantically related names (homogeneous sets) or unrelated names (heterogeneous sets). The naming latencies are typically longer in related than in unrelated sets. In Experiment 1 we replicated this semantic blocking effect and demonstrated that the effect only arose after all objects of a set had been shown and named once. In Experiment 2, the objects of a set were presented simultaneously (instead of on successive trials). Evidence for semantic blocking was found in the naming latencies and in the gaze durations for the objects, which were longer in homogeneous than in heterogeneous sets. For the gaze-to-speech lag between the offset of gaze on an object and the onset of the articulation of its name, a repetition priming effect was obtained but no blocking effect. Experiment 3 showed that the blocking effect for speech onset latencies generalized to new, previously unnamed lexical items. We propose that the blocking effect is due to refractory behaviour in the semantic system.
Association Learning↗
The formulation as a collaborative conversation.
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Adult↗
The impact of low-grade brain tumors on verbal fluency performance.
Verbal fluency has traditionally represented left hemispheric function, based on large acquired lesion studies. However, recent functional imaging studies have demonstrated bilateral hemispheric activation during phonemic and semantic word generation tasks. We examined 25 left hemisphere (LH) and 26 right hemisphere (RH) low-grade brain tumor patients on semantic and phonemic fluency. Patients were also assigned to a combined posterior (left and right) group (n = 26) or a combined posterior (left and right) group (n = 20) and compared with normal controls (NC; n = 57). We hypothesized that there would be greater left than right hemispheric phonemic and semantic fluency impairments. We also hypothesized that there would be greater anterior, specifically left anterior, than posterior impairments on phonemic fluency given their respective retrieval and initiation requirements. Finally, it was predicted that the LH patients, particularly the left posterior group, would exhibit the greatest semantic fluency impairments. Results indicated that on semantic fluency, the LH group produced significantly fewer semantic fluency responses compared to the RH group, but the expected left posterior and left frontal group differences were not found. There were no significant patient group differences associated with phonemic fluency. While we encountered semantic fluency impairments in this brain tumor population, we did not find the extensive deficits associated with the distinct or localized brain regions previously reported in the literature.
Adult↗
Verbal fluency component analysis in adults with HIV/AIDS.
The present study examined the impact of HIV disease severity, depressed mood, and highly-active antiretroviral therapy (HAART) on verbal fluency components in a sample of adults with HIV-infection. Switching and clustering have been identified as dissociable components that contribute to performance on tests of phonemic and semantic verbal fluency. Advanced HIV-infection was predicted to differentially impair switching. Switching has been shown to be reduced in disorders affecting frontal-striatal systems (e.g., Parkinson's disease). Verbal fluency protocols (FAS and Animals) of 217 adults with HIV-infection were scored for total switches and average cluster size following the method of Troyer, et al. (1998). Component scores were compared to published norms. Analysis of variance (ANOVA) was used to examine the impact on switching and clustering performance of (1) HIV disease severity (presence of AIDS diagnosis) and depressed mood, and (2) AIDS diagnosis and medication status (current HAART therapy). FAS switching was more often impaired in participants with AIDS. Depressed mood did not affect switching. Neither AIDS diagnosis nor depressed mood was associated with clustering performance. Participants with an AIDS diagnosis who were receiving HAART showed better performance on FAS switching relative to participants with AIDS who were not taking antiretroviral medication. FAS switching appears to be sensitive to cognitive changes associated with advanced HIV-infection. Further research is needed to determine if switching is a specific marker of frontal-striatal dysfunction in this population.
Acquired Immunodeficiency Syndrome↗
Affective tasks elicit material-specific memory effects in temporal lobectomy patients.
Eighteen patients who had undergone a right (9) or left (9) temporal lobectomy (RTL, LTL) including removal of the amygdala and hippocampus were evaluated. Sixteen male and sixteen female undergraduate subjects were evaluated for normative comparison. All subjects were administered Verbal (words) and Visual (faces) paired associates tasks. The present study sought to evaluate material-specific memory after temporal lobectomy, and to compare affective versus neutral memory as well. Thus, there were 4 tasks: Verbal Affective, Verbal Neutral, Visual Affective, and Visual Neutral. The material-specific effects of better Verbal memory performance by the RTL subjects compared to the LTL subjects and better Visual memory performance by the LTL subjects than the RTL subjects were only significant for the Affective tasks, and not the Neutral tasks. Perhaps adding an affective dimension to the material-specific memory tasks engaged the amygdala in addition to the other structures known to be important in memory. A strong interpretaion of the present data is made difficult by task differences and the low average IQ and possible reorganization of function that may have occurred in the patient sample.
Adult↗
Discordance between WMS-III Word Lists subtest and RAVLT scores in older patients: four case examples.
To examine the adequacy of the WMS-III in the identification of memory deficits in older individuals, we administered the Word Lists subtest, along with a comparison measure, the Rey Auditory Verbal Learning Test (RAVLT), to four patients referred for assessment of dementia. Although the number of words recalled by the patients on the delayed trials of the Word Lists subtest and RAVLT were nearly identical, norms for the Word Lists subtest indicated that memory performance was within normal limits (i.e., low average or higher), while the RAVLT norms accurately characterized performance as impaired. We suspect that normative data for the WMS-III were compromised by inadvertent inclusion of older subjects with dementia or mild cognitive impairment. The findings from our cases call into question the use of the WMS-III Word Lists for older patients.
Aged↗
Covariates of production and perseveration on tests of phonemic, semantic and alternating fluency in normal aging.
Standard measures of phonemic and semantic fluency, as well as fluency measures that impose additional demands upon set-switching were administered to younger and older adults. No age effect was found for total output on semantic fluency, while older participants generated significantly more responses relative to their younger counterparts on the phonemic measure. However, older adults made significantly more perseverative errors on both these measures. For tests of alternating fluency, only where participants were required to switch between two semantic dimensions, was an age deficit observed. Although the correlation between phonemic repetitions and age remained significant when performance on the Digit Symbol Test or a measure of fluid intelligence was partialled out, age effects for semantic repetitions and semantic alternating fluency were substantially reduced. The age benefit for number of correct responses upon phonemic fluency was significantly attenuated when a measure of crystallized intelligence was entered as a control variable. The theoretical and practical implications of these results are discussed.
Adolescent↗
Verbal fluency patterns in two subgroups of patients with Alzheimer's disease.
Previous research has identified two subgroups of patients with Alzheimer's disease (AD) based on performance discrepancies on semantic and visual-constructional measures: Left AD (LAD) and Right AD (RAD). In this study, verbal fluency performances (Animal Fluency [AF] and Letter Fluency [FAS]) of these two subgroups were examined. It was hypothesized that LAD patients would perform worse on AF compared to FAS, due to an underlying breakdown of left-hemisphere semantic networks. On the other hand, the RAD group, which theoretically has a relatively preserved semantic system, yet difficulties retrieving overlearned information, was not expected to differ on the two fluency tasks. These predictions were based on the notion that the AF task requires intact retrieval and semantic processes, whereas the FAS task is reliant on retrieval processes alone. Patients were classified into subgroups on the basis of performance discrepancies on the Boston Naming Test (BNT) and Copy tasks: LAD (BNT < Copy); RAD (BNT > Copy). A split-plot ANOVA using demographically corrected standard T-scores revealed a significant main effect for fluency task, and a significant subgroup x fluency task interaction. LAD patients performed poorer on AF compared to FAS; there was no fluency task difference for the RAD group. Analysis of within-subcategory response clustering on AF revealed more instances of serial subclass exemplar responses by RAD members. These results support the loss theory in explaining the semantic deficit of LAD, and suggest that retrieval difficulties underlie the fluency problems of RAD.
Aged↗
Reproduction and recognition in short-term visual memory.
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Adult↗
Mobilization of cognitive resources and the generation effect.
The generation effect refers to the memory advantage of words that have been generated rather than read. Such a read-generate comparison confounds qualitative task differences and raises methodological problems. A revised methodology is proposed circumventing these problems in that the encoding task is held constant and all stimuli have to be generated, but the degree of generativeness (i.e. the amount of cueing) is varied. In Experiment 1, 1, the (refined version of the) generation effect is demonstrated in a within-subjects design; with increasing generation activity left to the subject, free recall performance increases. No effect is obtained for degree of target masking. The same finding is replicated and shown to be independent of self-paced study time when generative activity is manipulated between subjects (Experiment 2) or within subjects (Experiment 3). As all learning trials involve generation, encoding time is controlled statistically, and free recall is used as a measure of memory, this refined generation effect cannot be explained as an artifact of selective attention or elaboration. Rather, generative activity seems to increase the mobilization of cognitive resources. This motivational account is supported by Experiment 4 showing an enhanced generation effect for positive mood.
Adult↗
Individual differences in memory span: the contribution of rehearsal, access to lexical memory, and output speed.
Rehearsal speed has traditionally been seen to be the prime determinant of individual differences in memory span. Recent studies, in the main using young children as the subject population, have suggested other contributors to span performance, notably contributions from long-term memory and forgetting and retrieval processes occurring during recall. In the current research we explore individual differences in span with respect to measures of rehearsal, output time, and access to lexical memory. We replicate standard short-term phenomena; we show that the variables that influence children's span performance influence adult performance in the same way; and we show that lexical memory access appears to be a more potent source of individual differences in span than either rehearsal speed or output factors.
Adult↗
Semantic memory loss in dementia of Alzheimer's type. What do various measures measure?
This paper examines three methodological issues concerning the measurement of semantic memory impairment in brain-damaged patients. Ten carefully selected patients with dementia of Alzheimer's type (DAT) and anomia were studied. A battery of perceptual tests and direct tests of semantic memory led to the conclusion that these patients represented a homogeneous group having a prominent deterioration of their semantic memory store without visual perceptual deficits. The first issue addressed in this patient group was whether verbal fluency impairment accurately reflected the loss of semantic memory. It was found that verbal fluency (generation of semantic category lists) was impaired due to two major constraints: deterioration of semantic memory store, and variable difficulties in semantic search. Verbal fluency, therefore, reflects semantic memory loss to some degree, but is not a direct test of semantic memory store in DAT. The second issue was whether semantic memory impairment in our patients conformed to the 'semantic storage disorder' syndrome hypothesized by Shallice (1987). It was shown that, consistent with this hypothesis, the patients demonstrated co-occurrence of consistency of errors, loss of semantic cueing, and preserved superordinate knowledge with loss of detailed knowledge of concept items. The third issue was whether semantic cueing and semantic priming are altered in a similar manner in DAT. It demonstrated that semantic cueing and semantic priming, using the same words whose concepts were degraded in semantic memory, yielded an entirely different pattern of results. Cueing and priming therefore may not be used interchangeably in the study of semantic loss after brain damage.
Aged↗