Slower Information Processing Speed Research Articles

Gamma deficits as a neural signature of cognitive impairment in children treated for brain tumors.

Cognitive impairment is consistently reported in children treated for brain tumors, particularly in the categories of processing speed, memory, and attention. Although tumor site, hydrocephalus, chemotherapy, and cranial radiation therapy (CRT) are all associated with poorer function, CRT predicts the greatest deficits. There is a particularly high correlation between CRT and slowed information-processing speed. Cortical gamma-band oscillations have been associated with processing behaviorally relevant information; however, their role in the maintenance of cognition in individuals with processing deficits is unclear. We examined gamma oscillations using magnetoencephalography (MEG) in children undergoing CRT to test whether gamma characteristics can be a signature of cognitive impairment in this population. We collected resting-state data as well as data from baseline and active periods during two visual-motor reaction time tasks of varying cognitive loads from 18 healthy children and 20 patients. We found that only high-gamma oscillations (60-100 Hz), and not low-gamma oscillations (30-59 Hz), showed significant group differences in absolute power levels. Overall, compared with healthy children, patients showed the following: (1) lower total high-gamma (60-100 Hz) power during the resting state, as well as during task-related baseline and performance measures; (2) no change in gamma reactivity to increases in cognitive load; and (3) slower processing speeds both inside and outside MEG. Our findings show that high-gamma oscillations are disrupted in children after treatment for a brain tumor. The temporal dynamic of the high-gamma response during information processing may index cognitive impairment in humans with neurological injury.

Effects of APOE ε4, age, and HIV on glial metabolites and cognitive deficits.

We aimed to evaluate the combined effects of HIV and APOE ε4 allele(s) on glial metabolite levels, and on known cognitive deficits associated with either condition, across the ages. One hundred seventy-seven participants, primarily of white and mixed race (97 seronegative subjects: aged 44.7 ± 1.3 years, 85 [87.6%] men, 28 [28.9%] APOE ε4+; 80 HIV+ subjects: aged 47.3 ± 1.1 years, 73 [91.3%] men, 23 [28.8%] APOE ε4+), were assessed cross-sectionally for metabolite concentrations using proton magnetic resonance spectroscopy in 4 brain regions and for neuropsychological performance. Frontal white matter myo-inositol was elevated in subjects with HIV across the age span but showed age-dependent increase in seronegative subjects, especially in APOE ε4+ carriers. In contrast, only seronegative APOE ε4+ subjects showed elevated myo-inositol in parietal cortex. All APOE ε4+ subjects had lower total creatine in basal ganglia. While all HIV subjects showed greater cognitive deficits, HIV+ APOE ε4+ subjects had the poorest executive function, fluency memory, and attention/working memory. Higher myo-inositol levels were associated with poorer fine motor function across all subjects, slower speed of information processing in APOE ε4+ subjects, and worse fluency in HIV+ APOE ε4+ subjects. In frontal white matter of subjects with HIV, the persistent elevation and lack of normal age-dependent increase in myo-inositol suggest that persistent glial activation attenuated the typical antagonistic pleiotropic effects of APOE ε4 on neuroinflammation. APOE ε4 negatively affects energy metabolism in brain regions rich in dopaminergic synapses. The combined effects of HIV infection and APOE ε4 may lead to greater cognitive deficits, especially in those with greater neuroinflammation. APOE ε4 allele(s) may be a useful genetic marker to identify white and mixed-race HIV subjects at risk for cognitive decline.

Cognitive Effects of Late Life Depression: Review of Neuropsychological Findings

Normal aging and depression both slow information processing speed which leads to poorer attentional control, shallower inhibition monitoring, poorer encoding, poorer updating of short term memory, and subsequent poorer learning, set-shifting, error monitoring, inhibition control, and cognitive planning. A combination of aging and depression amplifies these cognitive effects. Deterioration in frontal brain functioning in normal aging is irreversible, but altering of frontal brain function due to depression may be reversible. Since the symptoms are indistinguishable, it is difficult to separate effects of depression and aging with use of neuropsychological tests, even when premorbid history is known. Statistical group effects show more severe cognitive effects in late life depression than in normal aging or depression in younger persons, but no particular cognitive markers of depression in older subjects have been identified. Attention and inhibition are closely related, but their relationship needs to be studied further. It is not clear, whether a problem with inhibition of irrelevant stimuli occurs because of attentional deficits due to late life depression, or if it is a primary consequence of the depression. Further studies on the relationship between inhibition, attention and processing speed involving homogeneous depressed and non-depressed groups of different age may help disentangle this relationship.

Information Processing Speed and 8-Year Mortality Among Community-Dwelling Elderly Japanese

BackgroundCognitive function is an important contributor to health among elderly adults. One reliable measure of cognitive functioning is information processing speed, which can predict incident dementia and is longitudinally related to the incidence of functional dependence. Few studies have examined the association between information processing speed and mortality. This 8-year prospective cohort study design with mortality surveillance examined the longitudinal relationship between information processing speed and all-cause mortality among community-dwelling elderly Japanese.MethodsA total of 440 men and 371 women aged 70 years or older participated in this study. The Digit Symbol Substitution Test (DSST) was used to assess information processing speed. DSST score was used as an independent variable, and age, sex, education level, depressive symptoms, chronic disease, sensory deficit, instrumental activities of daily living, walking speed, and cognitive impairment were used as covariates.ResultsDuring the follow-up period, 182 participants (133 men and 49 women) died. A multivariate Cox proportional hazards model showed that lower DSST score was associated with increased risk of mortality (hazard ratio [HR] = 1.62, 95% CI = 0.97–2.72; HR = 1.73, 95% CI = 1.05–2.87; and HR = 2.55, 95% CI = 1.51–4.29, for the third, second, and first quartiles of DSST score, respectively).ConclusionsSlower information processing speed was associated with shorter survival among elderly Japanese.

Intra-individual variability in information processing speed reflects white matter microstructure in multiple sclerosis

Slowed information processing speed is commonly reported in persons with multiple sclerosis (MS), and is typically investigated using clinical neuropsychological tests, which provide sensitive indices of mean-level information processing speed. However, recent studies have demonstrated that within-person variability or intra-individual variability (IIV) in information processing speed may be a more sensitive indicator of neurologic status than mean-level performance on clinical tests. We evaluated the neural basis of increased IIV in mildly affected relapsing–remitting MS patients by characterizing the relation between IIV (controlling for mean-level performance) and white matter integrity using diffusion tensor imaging (DTI). Twenty women with relapsing–remitting MS and 20 matched control participants completed the Computerized Test of Information Processing (CTIP), from which both mean response time and IIV were calculated. Other clinical measures of information processing speed were also collected. Relations between IIV on the CTIP and DTI metrics of white matter microstructure were evaluated using tract-based spatial statistics. We observed slower and more variable responses on the CTIP in MS patients relative to controls. Significant relations between white matter microstructure and IIV were observed for MS patients. Increased IIV was associated with reduced integrity in more white matter tracts than was slowed information processing speed as measured by either mean CTIP response time or other neuropsychological test scores. Thus, despite the common use of mean-level performance as an index of cognitive dysfunction in MS, IIV may be more sensitive to the overall burden of white matter disease at the microstructural level. Furthermore, our study highlights the potential value of considering within-person fluctuations, in addition to mean-level performance, for uncovering brain–behavior relationships in neurologic disorders with widespread white matter pathology.

The influence of impaired processing speed on cognition in first-episode antipsychotic-naïve schizophrenic patients

BackgroundImpaired cognition is a prominent feature of schizophrenia. To what extent the heterogeneous cognitive impairments can be accounted for by considering only a single underlying impairment or a small number of core impairments remains elusive. This study examined whether cognitive impairments in antipsychotic-naïve, first-episode schizophrenia patients may be determined by a relative slower speed of information processing. MethodForty-eight antipsychotic-naïve patients with first-episode schizophrenia and 48 matched healthy controls were administered a comprehensive battery of neuropsychological tests to assess domains of cognitive impairments in schizophrenia. Composite scores were calculated, grouping tests into cognitive domains. ResultsThere were significant differences between patients and healthy controls on global cognition and all cognitive domains, including verbal intelligence, processing speed, sustained attention, working memory, reasoning and problem solving, verbal learning and memory, visual learning and memory, and reaction time. All these significant differences, except for verbal intelligence and global cognition, disappeared when processing speed was included as a covariate. ConclusionAt the first stage of illness, antipsychotic-naïve patients with schizophrenia display moderate/severe impairments in all the cognitive domains assessed. The results support the contention of a global cognitive dysfunction in schizophrenia that to some extent may be determined by impaired processing speed.

Mental fatigue and cognitive impairment after an almost neurological recovered stroke.

Mental fatigue is for many a distressing and long-term problem after stroke. This mental fatigue will make it more difficult for the person to return to work and previous activities. The intention with this study is to investigate mental fatigue in relation to depression and cognitive functions. We examined 24 well-rehabilitated stroke subjects, who suffered from mental fatigue one year or more after a stroke, and 24 healthy controls. Subjects were examined using self-assessment scales for mental fatigue, depression and anxiety, and cognitive tests. The results showed a highly increased rating for mental fatigue for the stroke group (P < 0.001). These participants also had a significantly higher rating on the depression (P < 0.001) and anxiety (P < 0.001) scales. Furthermore, they had a slower information processing speed (P < 0.001) and made more errors in a demanding attention and speed test (P < 0.05). Among the cognitive tests, processing speed and errors made in an attention and speed test were significant predictors for mental fatigue. We suggest mental fatigue following a stroke to be related to cognitive impairments, primarily information processing speed. Mental fatigue should also be treated as a separate phenomenon and should be differentiated from, and not confused with, depression, even if overlapping symptoms exist.

Cognitive functioning in euthymic recurrently depressed patients: Relationship with future relapses and prior course of disease

Cognitive impairment seems to persist during the euthymic phase of recurrent depression but its relationship with future relapses as with prior course of the disease has to be elucidated. The purpose of this study is to investigate the presence and prognostic value of cognitive dysfunctions for relapse in high risk euthymic patients and to identify relevant associations between cognitive functioning and prior course of illness. Standardized neuropsychological tests of mental speed, memory and executive functioning were assessed in 137 remitted patients and compared with clinically used published normative data. Previous episodes and relapses within 24 months were measured using the Structured Clinical Interview for DSM-IV. Cognitive performance was significantly impaired on 12 of the 14 variables indicating deficits in the domain of speed of information processing and memory. With Cox regression no significant neuropsychological predictors for relapse or recurrence were identified. Furthermore, Pearson correlations between neuropsychological test scores and number of previous episodes, residual depressive symptoms and duration of remission were non-significant. Later age of onset was correlated with a slower speed of information processing and lower verbal memory performance. Published test reference data were used but no healthy control group. Presence of mild cognitive impairment in remitted patients was demonstrated but did not predict future relapses nor was it related with prior course of disease except for age of onset. Though, mild cognitive impairment after remission might have an impact on the quality of life, adding techniques from cognitive rehabilitation might prove to be a treatment option.

Decomposing attention-deficit/hyperactivity disorder (ADHD)-related effects in response speed and variability.

Slow and variable reaction times (RTs) on fast tasks are such a prominent feature of attention-deficit/hyperactivity disorder (ADHD) that any theory must account for them. However, this has proven difficult because the cognitive mechanisms responsible for this effect remain unexplained. Although speed and variability are typically correlated, it is unclear whether single or multiple mechanisms are responsible for group differences in each. RTs are a result of several semi-independent processes, including stimulus encoding, rate of information processing, speed-accuracy trade-offs, and motor response, which have not been previously well characterized. A diffusion model was applied to RTs from a forced-choice RT paradigm in two large, independent case-control samples (NCohort 1 = 214 and NCohort 2 = 172). The decomposition measured three validated parameters that account for the full RT distribution and assessed reproducibility of ADHD effects. In both samples, group differences in traditional RT variables were explained by slow information processing speed, and unrelated to speed-accuracy trade-offs or nondecisional processes (e.g., encoding, motor response). RT speed and variability in ADHD may be explained by a single information processing parameter, potentially simplifying explanations that assume different mechanisms are required to account for group differences in the mean and variability of RTs.

Anatomical and functional differences between the Paced Auditory Serial Addition Test and the Symbol Digit Modalities Test

The Paced Auditory Serial Addition Test (PASAT) and the Symbol Digit Modalities Test (SDMT) are generally used to detect cognitive impairments in multiple sclerosis patients. Although both seem to be sensitive to the slow information-processing speed, some results suggest that they do not involve the same cognitive functions. The aim of the present study is to observe possible differences between these tasks to help understand their utility to cognitive assessment. A total of 17 participants were recruited for the study and completed a block-design version of each task. Comparisons between tasks were calculated using an analysis of variance (ANOVA; p < .05, familywise error, FWE, corrected). We observed activations in the left frontal and parietal areas during both tasks; however, the PASAT activated more frontal areas than did the SDMT. These tasks require an efficient transfer of information among large areas. Moreover, the PASAT requires more executive functions to be executed.

The Association Between Serum Cortisol and Cognitive Decline in Older Persons

To investigate whether serum cortisol levels are associated with cognitive performance and cognitive decline in elderly persons and whether this association differs by age, sex, and depression status. Data from the Longitudinal Aging Study Amsterdam, with repeated measurements of cognitive performance after 3 and 6 years. A total of 1,154 persons, aged 65-88 years. Serum concentrations of total cortisol (CRT) and corticosteroid binding globulin (CBG) were measured at baseline, and from these free cortisol index (CRT/CBG) was computed. At baseline and 3 and 6 years of follow-up, global cognitive functioning, verbal memory performance, and speed of information processing were assessed. After adjustment for demographics, health, and life style variables, a significant association between high levels of free cortisol and poorer performance on verbal learning (B = -0.32; 95% confidence interval: -0.64 to -0.01) was found in both women and men. Additional adjustment for depression did not change this association. In women, but not in men, high levels of free cortisol (B = -0.85; 95% confidence interval: -1.40 to -0.31) were associated with slower speed of information processing. The associations between cortisol and cognitive performance were the same for the younger and the older old and for depressed and nondepressed persons. Higher levels of cortisol were not associated with cognitive decline over a period of 6 years. Our study provides further evidence that high levels of cortisol measured during the day are associated with lower memory function and speed of information processing but not with decline in cognitive functioning over 6 years of time.

Neuropsychological Features of Indigent Murder Defendants and Death Row Inmates in Relation to Homicidal Aspects of Their Crimes

Neuropsychological features of 77 indigent murder defendants and death row inmates were examined in relation to criminal variables underlying their homicidal acts. Clinically, the sample was characterized by elevated rates of developmental disorders (49%), personality disorders (54%), Axis I psychiatric disorders (45%), substance abuse (86%), and history of violence (43%). By statute, killing more than one person is an aggravating factor in many jurisdictions that renders a murder defendant eligible for the death penalty. Individuals who committed a single murder were characterized by executive dysfunction, lower intelligence, slower speed of information processing, and a higher frequency of developmental disorders (58%), relative to those charged and/or convicted of killing two or more people, who were characterized by a significantly higher rate of personality disorders (79%) and a lower rate of developmental disorders (34%). Additionally, using the FBI criminal classification system for categorizing homicide by motive, a significant difference in the frequency of psychosis was found among subgroups associated with the following motives: Criminal enterprise; personal cause; and sex. The collective neuropsychological profile of the sample revealed that executive functions were significantly decreased, relative to memory functions, with over half of the sample (55%) demonstrating executive dysfunction.

Examining the Link between Information Processing Speed and Executive Functioning in Multiple Sclerosis

Slowed information processing speed (IPS) is frequently reported in those with multiple sclerosis (MS), and at least 20% are compromised on some aspect of executive functioning also. However, any relationship between these two processes has not been examined. The Sternberg Memory Scanning Test, Processing Speed Index (WAIS-III), Delis Kaplan Executive Function System (D.KEFS), and Working Memory Index (WMS-III) were administered to 90 participants with MS. Their performance on the PSI was significantly below the normative scores but no deficits in memory scanning speed were evident. The initial response speed of the Sternberg and the PSI were more closely related to D.KEFS performance, particularly in timed tasks with a high cognitive demand (switching tasks). In contrast, memory scanning speed was related to working memory. This study reinforces the link between IPS and working memory in MS, and supports the suggestion that IPS is not a unitary construct.

Can CBT substantially change grey matter volume in chronic fatigue syndrome?

Sir, I wish to comment on the paper ‘Increase in prefrontal cortical volume following cognitive behavioural therapy (CBT) in patients with chronic fatigue syndrome (CFS)’ (De Lange et al. , 2008). The authors compared the grey matter volume (GMV) of 22 patients with CFS before and after treatment with CBT, and with 22 healthy controls who were assessed at a similar time interval but received no treatment. The patient sample at baseline had a 5% smaller GMV as compared to healthy controls. In patients, GMV at baseline was correlated with slow information processing speed and physical activity. At …

Core neurocognitive functions in children treated for posterior fossa tumors.

Identifying cognitive deficits associated with pediatric brain tumors and their treatment is important in delineating the mechanisms of intellectual decline often associated with these diseases. The authors evaluated sustained attention, information processing speed, working memory, and IQ in 64 patients with posterior fossa tumors, including those treated with either: (a) surgery and cranial radiation (n = 32), and (b) surgery without radiation (n = 32). Ten patients treated for non-CNS solid tumors were included as a comparison group. The authors also examined the impact of relevant demographic and medical variables on neurocognitive outcome. The authors found that neither age at, nor time since, diagnosis predicted cognitive outcome in this sample. Further, sustained attention and working memory were largely intact and there were no differences between groups. Patients treated with cranial radiation demonstrated lowered short-form IQ and slow information processing speed: Patients treated with cranial radiation and who experienced postsurgical complications demonstrated the poorest performance. The authors consider information processing speed to be an excellent candidate mechanism in understanding the impact of cranial radiation on intellectual outcome.

Depression and cognition in older adults

Recognition that depression is associated with neurocognitive impairment and renewed recent interest in milder forms of cognitive impairment in older people (typified by the concept of mild cognitive impairment) have stimulated researchers to investigate the relationship between depression and cognitive impairment. This review identifies and clarifies recent progress in this rapidly developing research area. Neurocognitive impairment persists in most depressed older people after clinical recovery, and slowed information processing speed and possibly executive dysfunction and vascular risk factors underlie this. Most studies suggest that this neurocognitive impairment in turn leads to increased mild cognitive impairment as well as dementia. White matter disease appears to directly contribute to depression in older people and this worsens over time. Polymorphisms in the serotonin transporter gene may be a key risk factor as well, and depression worsens vascular outcome in peripheral arterial disease. Clinicians should be aware that neurocognitive deficits persist and have an adverse effect on outcome, and that vascular risk factors may contribute to these deficits.

Neuropsychological dysfunction related to earlier occupational exposure to mercury vapor

We assessed the neuropsychological test performances of 26 patients (mean age = 41.5 +/- 6.1 years; mean years of education = 9.8 +/- 1.8; 20 males) diagnosed with chronic occupational mercurialism who were former workers at a fluorescent lamp factory. They had been exposed to elemental mercury for an average of 10.2 +/- 3.8 years and had been away from this work for 6 +/- 4.7 years. Mean urinary mercury concentrations 1 year after cessation of work were 1.8 +/- 0.9 microg/g creatinine. Twenty control subjects matched for age, gender, and education (18 males) were used for comparison. Neuropsychological assessment included attention, inhibitory control, verbal and visual memory, verbal fluency, manual dexterity, visual-spatial function, executive function, and semantic knowledge tests. The Beck Depression Inventory and the State and Trait Inventory were used to assess depression and anxiety symptoms, respectively. The raw score for the group exposed to mercury indicated slower information processing speed, inferior performance in psychomotor speed, verbal spontaneous recall memory, and manual dexterity of the dominant hand and non-dominant hand (P < 0.05). In addition, the patients showed increased depression and anxiety symptoms (P < 0.001). A statistically significant correlation (Pearson) was demonstrable between mean urinary mercury and anxiety trait (r = 0.75, P = 0.03). The neuropsychological performances of the former workers suggest that occupational exposure to elemental mercury has long-term effects on information processing and psychomotor function, with increased depression and anxiety also possibly reflecting the psychosocial context.

Atypical Onset of Symptoms in Huntington Disease: Severe Cognitive Decline Preceding Chorea or Other Motor Manifestations

To describe the onset of Huntington disease (HD) in a patient with atypical progression of symptoms. The authors report the case of a 39-year-old man with severe cognitive impairment and diffuse cortical atrophy before the onset of motor manifestations or symptoms of an extrapyramidal movement disorder. Clinical examinations, neuropsychologic assessments, magnetic resonance imaging, electroencephalogram, and genetic testing were conducted. Although HD was eventually confirmed through genetic testing, chorea was not part of the clinical picture until well after the patient had developed a frank dementia, with a decline in global intellectual functioning, memory deficits, slowed information processing speed, and executive dysfunction. This case indicates HD may present with atypical clinical features in the early course of the disease, and warrants diagnostic consideration in patients with early dementia of unknown etiology.

Effects of Mild Traumatic Brain Injury: Comparison of Direct and Indirect Injury Groups

AbstractThe aims were to investigate the general and specific effects of mild traumatic brain injury (mTBI), and if people with orthopaedic injuries who had sustained their injuries through exposure to acceleration/deceleration force could have sustained a brain injury. The Rapid Screen of Concussion and Digit Symbol Substitution Test were given to patients with mTBI (89 male, 23 female), and patients with orthopaedic injuries that did (27 male, 5 female) or did not (27 male, 15 female) involve deceleration forces within 24 hours of injury. A group of uninjured people (31 male, 12 female) were also tested. Compared to all other groups, patients with mTBI recalled fewer words and correctly answered fewer orientation questions. Patients with either mTBI or deceleration orthopaedic injuries showed slower speed of information processing than patients with nondeceleration orthopaedic injuries or participants without injury. Nondeceleration patients and uninjured participants did not differ. These results suggest that there are both general injury effects and specific mTBI effects on efficiency of cognitive functioning. The results also highlight the probability that patients with a diagnosis of orthopaedic injury who were exposed to acceleration/deceleration forces may have suffered a mild brain injury as well.

The Relationship of Structural Alterations to Cognitive Deficits in Schizophrenia: A Voxel-Based Morphometry Study

Region of interest studies have identified a number of structure-cognition associations in schizophrenia and revealed alterations in structure-cognition relationship in this population. We examined the relationship of structural brain alterations, identified using voxel-based morphometry, to cognitive deficits in 45 schizophrenia patients relative to 43 healthy control subjects and tested the hypothesis that structure-cognition relationship is altered in schizophrenia. Patients had smaller total brain, gray matter, and white matter volumes. Regional alterations were left-hemisphere specific, including: gray matter reduction of inferior frontal, lingual, and anterior superior temporal gyri; white matter reduction of posterior and occipital lobes; and gray matter increase of the putamen and the precuneus. Smaller whole brain and gray matter volumes were associated with lower premorbid intelligence quotient (IQ) and poorer performance on IQ-dependent cognitive measures in patients and to a similar extent in control subjects. Larger precuneus was associated with better immediate verbal memory in patients, whereas verbal and nonverbal memory were positively associated with inferior frontal gyrus volume in control subjects. Smaller occipital white matter volume was associated with slower information processing speed in patients but not in control subjects. Regional volume alterations are associated with specific cognitive deficits in schizophrenia. Some structure-cognition relationships differentiate this population from healthy control subjects.