Dysexecutive functioning in mild cognitive impairment: derailment in temporal gradients.

Libon et al. (2010) provided evidence for three statistically determined clusters of patients with mild cognitive impairment (MCI): amnesic (aMCI), dysexecutive (dMCI), and mixed (mxMCI). The current study further examined dysexecutive impairment in MCI using the framework of Fuster's (1997) derailed temporal gradients, that is, declining performance on executive tests over time or test epoch. Temporal gradients were operationally defined by calculating the slope of aggregate letter fluency output across 15-s epochs and accuracy indices for initial, middle, and latter triads from the Wechsler Memory Scale-Mental Control subtest (Boston Revision). For letter fluency, slope was steeper for dMCI compared to aMCI and NC groups. Between-group Mental Control analyses for triad 1 revealed worse dMCI performance than NC participants. On triad 2, dMCI scored lower than aMCI and NCs; on triad 3, mxMCI performed worse versus NCs. Within-group Mental Control analyses yielded equal performance across all triads for aMCI and NC participants. mxMCI scored lower on triad 1 compared to triads 2 and 3. dMCI participants also performed worse on triad 1 compared to triads 2 and 3, but scored higher on triad 3 versus triad 2. These data suggest impaired temporal gradients may provide a useful heuristic for understanding dysexecutive impairment in MCI.

To err is human, to monitor divine: environmental adaptations reduce everyday errors but do not improve monitoring.

The current study aimed to address error monitoring impairments in dementia using an intervention for execution deficits. Thirty-eight participants completed the Naturalistic Action Test (NAT) under two conditions: Standard and User-Centered. The Standard NAT followed the manual procedures; in the User-Centered NAT, objects were arranged sequentially, and distractor items were separated from target objects. While participants committed fewer errors in the User-Centered condition, there was no difference in the proportion of errors detected. However, the neuropsychological processes associated with monitoring differed across conditions. The results have implications for a neuropsychological model of error monitoring in dementia.

Verbal serial list learning in mild cognitive impairment: a profile analysis of interference, forgetting, and errors.

Using cluster analysis Libon et al. (2010) found three verbal serial list-learning profiles involving delay memory test performance in patients with mild cognitive impairment (MCI). Amnesic MCI (aMCI) patients presented with low scores on delay free recall and recognition tests; mixed MCI (mxMCI) patients scored higher on recognition compared to delay free recall tests; and dysexecutive MCI (dMCI) patients generated relatively intact scores on both delay test conditions. The aim of the current research was to further characterize memory impairment in MCI by examining forgetting/savings, interference from a competing word list, intrusion errors/perseverations, intrusion word frequency, and recognition foils in these three statistically determined MCI groups compared to normal control (NC) participants. The aMCI patients exhibited little savings, generated more highly prototypic intrusion errors, and displayed indiscriminate responding to delayed recognition foils. The mxMCI patients exhibited higher saving scores, fewer and less prototypic intrusion errors, and selectively endorsed recognition foils from the interference list. dMCI patients also selectively endorsed recognition foils from the interference list but performed similarly compared to NC participants. These data suggest the existence of distinct memory impairments in MCI and caution against the routine use of a single memory test score to operationally define MCI.

Improving everyday error detection, one picture at a time: a performance-based study of everyday task training.

OBJECTIVE: Research suggests that dementia patients detect fewer action errors than age-matched controls; however, little is known about the derivation of their error-monitoring difficulties. The aims of the study are to evaluate a novel, task-training action intervention (TT-NAT) designed to increase error monitoring in dementia patients and to pinpoint the relation between error monitoring and neuropsychological processes. METHOD: Participants (n = 45) with dementia were administered the Standard NAT, a performance-based test requiring completion of three everyday tasks. A second group (n = 42) was administered the TT-NAT, which includes a brief training session prior to the commencement of each task. All participants were compared on the following variables: total errors, proportion of errors detected, and proportion of errors corrected. Correlations between error-monitoring variables and neuropsychological tests of executive functioning and language were performed. RESULTS: TT-NAT participants produced fewer total errors and detected significantly more errors than Standard NAT participants (z = 3.0; t = 3.36; p < .05). Error detection was strongly related to only the language composite index (r = .57, p = .00) in the TT-NAT, whereas it was moderately related to both the language (r = .31, p = .04) and executive composite (r = .36, p = .02) indices in the Standard NAT condition. CONCLUSION: Review of task steps and objects before task performance may be a promising intervention for error-monitoring deficits in dementia patients; this finding has implications for neuropsychological rehabilitation of functional deficits in this population.

The importance of multiple assessments of object knowledge in semantic dementia: the case of the familiar objects task.

Semantic dementia (SD) is characterized by a dramatic loss of conceptual knowledge about the meaning of words and the identity of objects. Previous research has suggested that SD patients' knowledge is differentially influenced by the disease and may decline at different degrees depending on a patient's everyday familiarity with certain items. However, no study has examined (a) semantic knowledge deterioration and (b) the potential significance of autobiographical experience for the maintenance of object concepts in the same cohort of SD patients by using comprehensive assessments of different aspects of object knowledge across an experience-based, distributed semantic memory network. Here, we tested four SD patients and three Alzheimer's disease (AD) control patients using a range of tasks - including naming, gesture generation, and autobiographical knowledge - with personally familiar objects or perceptually similar or different object analogs. Our results showed dissociations between performance on naming relative to other assessments of object knowledge between SD and AD patients, though we did not observe a reliable familiar objects advantage. We discuss different factors that may account for these findings, as well as their implications for research on SD.

Target-related distractors disrupt object selection in everyday action: evidence from participants with dementia.

This study evaluated the impact of distractor objects and their similarity to target objects on everyday task performance in dementia. Twenty participants with dementia due to Alzheimer's disease (n = 12) or subcortical vascular disease (n = 8) were videotaped while they performed 3 discrete tasks: (1) make a cup of coffee, (2) wrap a gift, and (3) pack a lunch under two conditions that were counterbalanced across participants. The conditions differed in terms of the type of distractor objects included in the workspace: (1) Target-Related Distractor Condition - distractor objects were functionally and visually similar to target objects (e.g., salt for sugar) (2) Unrelated Distractor Condition - distractors were neither visually nor functionally similar to targets (e.g., glue for sugar). Participants touched (t = 4.19; p < .01) and used (z = 3.00; p < .01) significantly more distractors, made more distractor errors (i.e., substitutions; t = 2.93; p < .01), and took longer to complete tasks (t = 2.27; p < .05) in the Target-Related Distractor condition. The percent of steps accomplished and non-distractor errors did not differ across conditions (t < 1.26; p > .05 for both). In summary, distractors that were similar to targets elicited significant interference effects circumscribed to object selection.

Neuropsychological deficits associated with Complex Regional Pain Syndrome.

We sought to elucidate the existence of neuropsychological subtypes in Complex Regional Pain Syndrome (CRPS). One hundred thirty seven patients with CRPS were administered tests that assess executive control, naming/lexical retrieval, and declarative memory. A 2-step cluster analysis that does not require any a priori specification regarding the number of clusters, classified patients into three groups. Group 1 obtained scores that were in the average range on all tests (n = 48; normal CRSP group). Group 2 (n = 58; dysexecutive CRSP group) presented with mild impairment or statistically low average test performance on working memory/verbal fluency tests. Group 3 (n = 31; global CRSP group) produced scores in the statistically low average/borderline range on all tests with particularly reduced scores on naming/declarative memory tests. Between-group analyses found that the CRPS group 1 obtained higher scores than CRPS groups 2 and 3 on all tests. However, groups 2 and 3 were equally impaired on executive tests. CRPS group 3 was impaired on tests of naming/memory tests compared to the other groups. Significant neuropsychological deficits are present in 65% of patients, with many patients presenting with elements of a dysexecutive syndrome and some patients presenting with global cognitive impairment.

The heterogeneity of mild cognitive impairment: a neuropsychological analysis.

A group of 94 nondemented patients self-referred to an outpatient memory clinic for memory difficulties were studied to determine the incidence of single versus multi-domain mild cognitive impairment (MCI) using Petersen criteria. Fifty-five community dwelling normal controls (NC) participants without memory complaints also were recruited. Tests assessing executive control, naming/lexical retrieval, and declarative memory were administered. Thirty-four patients exhibited single-domain MCI, 43 patients presented with multi-domain MCI. When the entire MCI sample (n = 77) was subjected to a cluster analysis, 14 patients were classified with amnesic MCI, 21 patients with dysexecutive MCI, and 42 patients were classified into a mixed/multi-domain MCI group involving low scores on tests of letter fluency, "animal" fluency, and delayed recognition discriminability. Analyses comparing the three cluster-derived MCI groups versus a NC group confirmed the presence of memory and dysexecutive impairment for the amnesic and dysexecutive MCI groups. The mixed MCI group produced lower scores on tests of letter fluency compared with the amnesic MCI and NC groups and lower scores on tests of naming and memory compared with the NC group. In summary, multi-domain MCI is quite common. These data suggest that MCI is a highly nuanced and complex clinical entity.

Characterization of everyday functioning in mild cognitive impairment: a direct assessment approach.

AIMS: To evaluate the degree and pattern of functional difficulties in mild cognitive impairment (MCI) via direct observation of everyday task performance. METHODS: MCI (n = 25), mild Alzheimer's disease (AD; n = 25), and control (n = 18) participants performed three everyday tasks of increasing complexity. RESULTS: Although caregivers reported no functional difficulties in MCI, direct observation measures of overall impairment and total errors showed MCI participants performed worse than controls, but better than AD participants, even on simple tasks. MCI and control participants exhibited significantly more difficulty performing steps accurately (i.e. commission errors) than completing task steps (i.e. omission errors), but AD participants showed an even distribution of commissions and omissions. CONCLUSIONS: Diagnostic criteria for MCI should specify mild functional deficits due to the inefficient and imprecise execution of task steps. Functional deficits characterized by omission of major task segments may indicate a diagnosis of dementia.