Biomedical subjects

Ian H Robertson

Publications and source records attributed to Ian H Robertson.

At least 19 recordsLinked to original sources

PubMed2007

Awareness of deficits in traumatic brain injury: a multidimensional approach to assessing metacognitive knowledge and online-awareness.

Recent models of impaired awareness in brain injury draw a distinction between metacognitive knowledge of difficulties and online awareness of errors (emergent and anticipatory). We examined performance of 31 Traumatic Brain Injury (TBI) participants and 31 healthy controls using a three-strand approach to assessing awareness. Metacognitive knowledge was assessed with an awareness interview and discrepancy scores on three questionnaires--Patient Competency Rating Scale, Frontal Systems Behavioral Scale and the Cognitive Failures Questionnaire. Online Emergent Awareness was assessed using an online error-monitoring task while participants performed tasks of sustained attention. Online anticipatory awareness was examined using prediction performance on two cognitive tasks. Results indicated that the TBI Low Self-Awareness (SA) group and High SA group did not differ in terms of severity, chronicity or standard neuropsychological tasks but those with Low SA were more likely to exhibit disinhibition, interpersonal problems and more difficulties in total competency. Sustained attention abilities were associated with both types of online awareness (emergent and anticipatory). There was a strong relationship between online emergent and online anticipatory awareness. Metacognitive knowledge did not correlate with the other two measures. This study highlights the necessity in adopting a multidimensional approach to assessing the multifaceted phenomenon of awareness of deficits.

Adult↗

PubMed2007

Cognitive rehabilitation in the elderly: a randomized trial to evaluate a new protocol.

This study provides an introduction to, and overview of, several papers that resulted from a randomized control trial that evaluated a new cognitive rehabilitation protocol. The program was designed to improve general strategic abilities in ways that would be expressed in a broad range of functional domains. The trial, which was conducted on a sample of older adults who had experienced normal age-related cognitive decline, assessed performance in the following domains: memory, goal management, and psychosocial status. The general rationale for the trial, the overall experimental design, and the approach to statistical analyses that are relevant to each paper are described here. The results for each functional domain are reported in separate papers in this series.

Aged↗

PubMed2007

Cognitive rehabilitation in the elderly: effects on strategic behavior in relation to goal management.

Executive functions are highly sensitive to the effects of aging and other conditions affecting frontal lobe function. Yet there are few validated interventions specifically designed to address executive functions, and, to our knowledge, none validated in a healthy aging sample. As part of a large-scale cognitive rehabilitation randomized trial in 49 healthy older adults, a modified Goal Management Training program was included to address the real-life deficits caused by executive dysfunction. This program emphasized periodic suspension of ongoing activity to establish goal hierarchies and monitor behavioral output. Tabletop simulated real-life tasks (SRLTs) were developed to measure the processes targeted by this intervention. Participants were randomized to two groups, one of which received the intervention immediately and the other of which was wait-listed prior to rehabilitation. Results indicated improvements in SRLT performance and self-rated executive deficits coinciding with the training in both groups. These gains were maintained at long-term follow-up. Future research will assess the specificity of these effects in patient groups.

Aged↗

PubMed2007

Cognitive rehabilitation in the elderly: overview and future directions.

This study provides an overview of the papers emanating from the experimental trial that evaluated a new cognitive rehabilitation program in older adults who were experiencing normal cognitive decline. The main features of the design are summarized, along with evidence that the training produced long-lasting improvement in memory performance, goal management, and psychosocial status. The benefits were attributed to several factors, including the program's emphasis on techniques that promoted efficient strategic processing. Limitations of the program and directions for future research are discussed.

Aged↗

PubMed2006

Response variability in attention deficit hyperactivity disorder: evidence for neuropsychological heterogeneity.

Response time (RT) variability is a common finding in ADHD research. RT variability may reflect frontal cortex function and may be related to deficits in sustained attention. The existence of a sustained attention deficit in ADHD has been debated, largely because of inconsistent evidence of time-on-task effects. A fixed-sequence Sustained Attention to Response Task (SART) was given to 29 control, 39 unimpaired and 24 impaired-ADHD children (impairment defined by the number of commission errors). The response time data were analysed using the Fast Fourier Transform, to define the fast-frequency and slow-frequency contributions to overall response variability. The impaired-ADHD group progressively slowed in RT over the course of the 5.5min task, as reflected in this group's greater slow-frequency variability. The fast-frequency trial-to-trial variability was also significantly greater, but did not differentially worsen over the course of the task. The higher error rates of the impaired-ADHD group did not become differentially greater over the length of the task. The progressive slowing in mean RT over the course of the task may relate to a deficit in arousal in the impaired-ADHD group. The consistently poor performance in fast-frequency variability and error rates may be due to difficulties in sustained attention that fluctuate on a trial-to-trial basis.

Adolescent↗

PubMed2006

Electrophysiological and information processing variability predicts memory decrements associated with normal age-related cognitive decline and Alzheimer's disease (AD).

Recent theoretical models of cognitive aging have implicated increased intra-individual variability as a critical marker of decline. The current study examined electrophysiological and information processing variability and memory performance in normal younger and older controls, and older adults with Alzheimer's disease (AD). It was hypothesized that higher levels of variability would be indicative of age-related and disease-related memory deficits. Results indicated both implicit and explicit memory deficits associated with AD. Consistent with previous research, behavioral speed and variability emerged as sensitive to age- and disease-related change. Amplitude variability of P3 event-related potentials was a unique component of electrophysiological activity and accounted for significant variance in reaction time (RT) mean and RT standard deviation, which in turn accounted for significant variance in memory function. Results are discussed in light of theoretical and applied issues in the field of cognitive aging.

Adult↗

PubMed2006

Variance in neurocognitive performance is associated with dysbindin-1 in schizophrenia: a preliminary study.

Susceptibility genes for schizophrenia have been hypothesised to mediate liability for the disorder at least partly by influencing cognitive performance. We investigated the association between genotype and cognitive performance for a Dysbindin risk haplotype which is associated with schizophrenia in our sample. Fifty-two patients with schizophrenia or schizoaffective disorder (24 risk haplotypes carriers versus 28 non-risk haplotype carriers) were assessed in areas of cognition showing evidence of familial deficits in schizophrenia. Verbal and spatial memory, working memory, and attentional control was assessed using selected measures from the Weschler memory scale (WMS), Cambridge automated test battery (CANTAB), continuous performance test (CPT), and a simple go/no-go task. Pre-morbid IQ was also assessed using the Weschler Test of Adult Reading (WTAR). Patients carrying the Dysbindin risk haplotype showed significantly lower spatial working memory performance than patients who were non-risk carriers, with genotype explaining 12% of variance in performance. Our study suggests that the increased risk for schizophrenia associated with dysbindin may be partly mediated by its influence on pre-frontal function.

Adolescent↗

PubMed2006

Latent structure of the Test of Everyday Attention in a non-clinical Chinese sample.

The validity and clinical viability of Posner and Petersen's (1999) 3-factor model of attention was tested through a confirmatory factor analysis of attentional performance (Test of Everyday Attention [Robertson, I. H., Ward, T., Ridgeway, V., & Nimmo-Smith, I. (1996). The structure of normal human attention: The Test of Everyday Attention. Journal of the International Neuropsychological Society, 2, 525-534]) in a sample of 133 Chinese participants. This study served both as a cross-cultural replication of the clinical implementation of this leading theoretical model of attention, and as a more stringent test of the validity of the hypothesized attentional processes underlying human cognitive control. The results support the validity of a 3-factor model of attention consistent with that proposed by Posner and Petersen (selective attention, sustained attention, and attentional switching/control), and demonstrate that clinical assessment of neuroanatomically-distinct attentional processes using simulated real life activities is possible.

Activities of Daily Living↗

PubMed2006

Impaired temporal resolution of visual attention and dopamine beta hydroxylase genotype in attention-deficit/hyperactivity disorder.

BACKGROUND: Dopamine beta hydroxylase (DbetaH) catalyzes the conversion of dopamine to noradrenaline. Attention-deficit/hyperactivity disorder (ADHD) has been associated with the A2 allele of a Taq I polymorphism of the DBH gene. Since catecholamines regulate visual attention, we examined whether participants with ADHD were impaired on a task requiring temporal attention and how DBH genotype influenced temporal attention in ADHD. METHODS: Thirty-seven children and adolescents with ADHD and 52 matched, normal control subjects participated. Participants were presented with two visual stimuli, separated in time by either 50, 100, or 200 milliseconds, and were asked to judge the temporal order of their onset. Genotypes for the Taq 1 polymorphism were available for 33 of the ADHD participants. RESULTS: Attention-deficit/hyperactivity disorder participants were more error prone than control subjects, particularly when stimuli were presented close together in time (i.e., at the 50 milliseconds asynchrony). Moreover, ADHD individuals homozygous for the A2 allele performed more poorly than those without this allele, and this difference was accentuated at the 50 milliseconds asynchrony. CONCLUSIONS: Attention-deficit/hyperactivity disorder participants have an impaired rate of perceptual processing for rapidly presented visual events. Deficits in the temporal resolution of visual attention in ADHD are associated with the A2 allele of the Taq I DBH polymorphism or another variant with which it is in linkage disequilibrium.

Adolescent↗

PubMed2006

Are deficits in executive sub-processes simply reflecting more general cognitive decline in schizophrenia?

BACKGROUND: Schizophrenia is associated with both global and specific cognitive deficits. We sought to investigate whether deficits in executive subcomponents differed in their relationship to global cognitive impairments. METHOD: 95 patients were classified according to pre-morbid and current general cognitive ability as having either (a) intact pre-morbid and current general cognitive ability; (b) intact pre-morbid but deteriorated current ability, and (c) deteriorated both pre-morbid and current cognitive ability. All patients completed measures of verbal and spatial working memory, sustained selective attention, attentional set sifting, and inhibitory control. RESULTS: Deficits on both measures of working memory were associated with general cognitive ability. None of the attentional control deficits observed were associated with general ability. Further, spatial working memory deficits were also associated with more severe negative symptoms. CONCLUSIONS: These results provide further evidence of the discreet nature of attentional deficits in schizophrenia. By contrast, this study suggests that working memory deficits may to some extent index more general cognitive decline. Awareness of such overlap is important for schizophrenia genetics studies where working memory measures has been used to index supposedly discreet aspects of cognitive dysfunction.

Adult↗

PubMed2006

Investigating the enhancing effect of music on autobiographical memory in mild Alzheimer's disease.

The enhancing effect of music on autobiographical memory recall in mild Alzheimer's disease individuals (n = 10; Mini-Mental State Examination score >17/30) and healthy elderly matched individuals (n = 10; Mini-Mental State Examination score 25-30) was investigated. Using a repeated-measures design, each participant was seen on two occasions: once in music condition (Vivaldi's 'Spring' movement from 'The Four Seasons') and once in silence condition, with order counterbalanced. Considerable improvement was found for Alzheimer individuals' recall on the Autobiographical Memory Interview in the music condition, with an interaction for condition by group (p < 0.005). There were no differences in terms of overall arousal using galvanic skin response recordings or attentional errors during the Sustained Attention to Response Task. A significant reduction in state anxiety was found on the State Trait Anxiety Inventory in the music condition (p < 0.001), suggesting anxiety reduction as a potential mechanism underlying the enhancing effect of music on autobiographical memory recall.

Acoustic Stimulation↗

PubMed2006

The anterior cingulate and error avoidance.

The precise role of the anterior cingulate cortex in monitoring, evaluating, and correcting behavior remains unclear despite numerous theories and much empirical data implicating it in cognitive control. The present event-related functional magnetic resonance imaging study was able to separate monitoring from error-specific functions by allowing subjects to reject a trial so as to avoid errors. Cingulate and left dorsolateral prefrontal activity was greatest on rejection trials but comparable for correct and error trials, whereas an error-specific response was observed in bilateral insula. A dissociation was also observed between the cingulate and the nucleus accumbens with the latter more active for error than reject trials. These results reveal that the functional role of the cingulate is not particular to errors but instead is related to an evaluative function concerned with on-line behavioral adjustment in the service of avoiding losses.

Adult↗

PubMed2006

The cognitive genetics of attention deficit hyperactivity disorder (ADHD): sustained attention as a candidate phenotype.

Here we describe the application of cognitive genetics to the study of attention deficit hyperactivity disorder (ADHD). Cognitive genetics owes much to the pioneering work of cognitive neuropsychologists such as John Marshall, whose careful observations of cognitive dissociations between brain-lesioned patients greatly advanced the theoretical understanding of normal cognitive function. These theories have in turn helped to constrain linkages between candidate genes and cognitive processes and thus help to drive the relatively new field of cognitive genetics in a hypothesis-driven fashion. We examined the relationship between sustained attention deficits in ADHD and genetic variation in a catecholamine-related gene, dopamine beta hydroxylase (DbetaH). DBH encodes the enzyme that converts dopamine to noradrenaline and is crucial to catecholamine regulation. A polymorphism with the DBH gene has been associated with ADHD. In fifty-two children with ADHD, we examined whether variation in the Taq I DBH gene polymorphism was related to sustained attention performance. Participants performed the Sustained Attention to Response Test (SART). Performance on the SART discriminates ADHD from control children, and in imaging work, is associated with right frontoparietal activation. A significant effect of DBH genotype was found on SART performance measures. Children possessing two copies of the ADHD-associated risk allele (A2) had significantly poorer sustained attention than those ADHD children who did not possess this allele or a non-genotyped control group. The DBH gene may contribute to the susceptibility for ADHD, in part because of its varying effects on the development of brain mechanisms mediating sustained attention.

Adolescent↗

PubMed2006

Do antisaccade deficits in schizophrenia provide evidence of a specific inhibitory function?

BACKGROUND: Despite its inhibitory control requirements, antisaccade deficits have been consistently associated with working memory impairments in schizophrenia. We investigated whether variance in antisaccade performance could be better accounted for in terms of a specific inhibitory function. METHOD: We assessed 48 clinically stable out-patients with schizophrenia on an antisaccade task, as well as on measures of spatial and verbal working memory, sustained selective attention, and a simple motoric go/no-go measure of response inhibition. RESULTS: In a stepwise multiple regression analysis, go/no-go task performance accounted for a considerably greater percentage of variance in antisaccade performance (25.3%) than either working memory (8.4%) or sustained selective attention task (9.1%). DISCUSSION: We conclude that antisaccade deficits in schizophrenia appear to be better understood in terms of a specific deficit of inhibitory control than in terms of more general difficulties with context maintenance or goal neglect.

Adult↗

PubMed2006

Cognitive remediation in ADHD: effects of periodic non-contingent alerts on sustained attention to response.

Few studies have attempted direct cognitive remediation of attention deficits in attention-deficit hyperactivity disorder (ADHD). The present study investigated the efficacy of periodic non-informative alerting cues for improving sustaining attention in ADHD. This technique is known to improve sustained attention in right frontal injury patients and may be effective in ADHD, given that this disorder has also been linked with right frontal dysfunction. Fifteen children with ADHD and 15 matched controls completed four blocks of a modified version of the Sustained Attention to Response Task (SART). Eight random non-contingent alerts were introduced on two of these blocks as a cue for participants to adopt a more supervisory stance to their performance. While the alerting cues did not alter the total number of commission errors committed by ADHD children over a task block, they did produce a significant short-term reduction in commission errors in the period immediately following an alerting cue. Our data demonstrate that sustained attention performance can be enhanced in children with ADHD using a simple cognitive training strategy. Methods from the field of cognitive rehabilitation may be viably applied to the remediation of attention deficits in ADHD.

Adolescent↗

PubMed2006

Evidence that specific executive functions predict symptom variance among schizophrenia patients with a predominantly negative symptom profile.

INTRODUCTION: Although deficits in executive functioning in schizophrenia have been consistently reported, their precise relationship to symptomatology remains unclear. Recent approaches to executive functioning in nonschizophrenia studies have aimed to "fractionate" the individual cognitive processes involved. In this study, we hypothesised that if these processes are fractionable, then particular symptom syndromes may be selectively related to executive deficits. In particular, it was hoped that this approach could clarify whether negative and positive symptoms of schizophrenia are differentially related to particular aspects of executive/attentional functions. METHODS: A total of 32 patients with schizophrenia and 16 matched controls were assessed on a series of tasks designed to tap the theoretically derived executive functions of Inhibition, Shifting set, Working memory, and Sustained attention. RESULTS: Negative symptoms were significantly predicted by performance on an "Inhibition" task (Stroop), and not by performance on any other task. Furthermore, for a subgroup of patients with predominantly negative symptoms variance in positive symptoms was only significantly predicted by performance on a set-shifting task (Visual Elevator), and not by performance on other tasks, including inhibition. CONCLUSIONS: Our results support the contention that negative symptoms can, at least partly, be conceived of as cognitive behaviours expressing specific executive deficits. Specifically, we discuss the possibility that negative symptoms may, in part, express a failure in response monitoring. We further suggest that the disordered metacognition resulting in positive symptoms may be mediated by cognitive flexibility in patients with a predominantly negative symptom profile.

Adult↗

PubMed2006

In vivo characterization of traumatic brain injury neuropathology with structural and functional neuroimaging.

Quantitative neuroimaging is increasingly used to study the effects of traumatic brain injury (TBI) on brain structure and function. This paper reviews quantitative structural and functional neuroimaging studies of patients with TBI, with an emphasis on the effects of diffuse axonal injury (DAI), the primary neuropathology in TBI. Quantitative structural neuroimaging has evolved from simple planometric measurements through targeted region-of-interest analyses to whole-brain analysis of quantified tissue compartments. Recent studies converge to indicate widespread volume loss of both gray and white matter in patients with moderate-to-severe TBI. These changes can be documented even when patients with focal lesions are excluded. Broadly speaking, performance on standard neuropsychological tests of speeded information processing are related to these changes, but demonstration of specific brain-behavior relationships requires more refined experimental behavioral measures. The functional consequences of these structural changes can be imaged with activation functional neuroimaging. Although this line of research is at an early stage, results indicate that TBI causes a more widely dispersed activation in frontal and posterior cortices. Further progress in analysis of the consequences of TBI on neural structure and function will require control of variability in neuropathology and behavior.

Brain Injuries↗

PubMed2006

Executive "brake failure" following deactivation of human frontal lobe.

In the course of daily living, humans frequently encounter situations in which a motor activity, once initiated, becomes unnecessary or inappropriate. Under such circumstances, the ability to inhibit motor responses can be of vital importance. Although the nature of response inhibition has been studied in psychology for several decades, its neural basis remains unclear. Using transcranial magnetic stimulation, we found that temporary deactivation of the pars opercularis in the right inferior frontal gyrus selectively impairs the ability to stop an initiated action. Critically, deactivation of the same region did not affect the ability to execute responses, nor did it influence physiological arousal. These findings confirm and extend recent reports that the inferior frontal gyrus is vital for mediating response inhibition.

Adolescent↗