General Intellectual Functioning Research Articles

Prenatal Programming of Postnatal Susceptibility to Memory Impairments

In the study reported here, we examined the effects of fetal exposure to a synthetic stress hormone (synthetic glucocorticoids) on children’s susceptibility to postnatal sociodemographic adversity. We recruited children who were born healthy and at term. Twenty-six had been treated with steroid hormones (glucocorticoids) during the prenatal period, and 85 had not. Only children exposed to both prenatal stress hormones and postnatal sociodemographic adversity showed impaired performance on standardized tests of memory function. The association was specific to long-term memory. General intellectual functioning and expressive language were not affected by fetal glucocorticoid exposure. Results were independent of maternal intelligence and maternal depression at the time of the study. These findings are consistent with a vulnerability-stress model: Prenatal exposure to synthetic stress hormones is associated with increased susceptibility to subsequent adversity, with consequences for cognitive functioning that persist 6 to 10 years after birth.

Digit Span is (mostly) related linearly to general intelligence: Every extra bit of span counts.

Historically, Digit Span has been regarded as a relatively poor indicator of general intellectual functioning (g). In fact, Wechsler (1958) contended that beyond an average level of Digit Span performance, there was little benefit to possessing a greater memory span. Although Wechsler's position does not appear to have ever been tested empirically, it does appear to have become clinical lore. Consequently, the purpose of this investigation was to test Wechsler's contention on the Wechsler Adult Intelligence Scale-Fourth Edition normative sample (N = 1,800; ages: 16 - 69). Based on linear and nonlinear contrast analyses of means, as well as linear and nonlinear bifactor model analyses, all 3 Digit Span indicators (LDSF, LDSB, and LDSS) were found to exhibit primarily linear associations with FSIQ/g. Thus, the commonly held position that Digit Span performance beyond an average level is not indicative of greater intellectual functioning was not supported. The results are discussed in light of the increasing evidence across multiple domains that memory span plays an important role in intellectual functioning.

How does change in alcohol misuse and depression comorbidity impact on neuropsychological test performance after 12 months?

How does change in alcohol misuse and depression comorbidity impact on neuropsychological test performance after 12 months?

Utility of the Montreal Cognitive Assessment and Mini-Mental State Examination in predicting general intellectual abilities.

To determine whether scores from 2 commonly used cognitive screening tests can help predict general intellectual functioning in older adults. Cutoff scores for determining cognitive impairment have been validated for both the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE). However, less is known about how the 2 measures relate to general intellectual functioning as measured by the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV). A sample of 186 older adults referred for neuropsychological assessment completed the MoCA, MMSE, and WAIS-IV. Regression equations determined how accurately the screening measures could predict the WAIS-IV Full Scale Intelligence Quotient (FSIQ). We also determined how predictive the MoCA and MMSE were when combined with 2 premorbid estimates of FSIQ: the Test of Premorbid Functioning (TOPF) (a reading test of phonetically irregular words) and a predicted TOPF score based on demographic variables. MoCA and MMSE both correlated moderately with WAIS-IV FSIQ. Hierarchical regression models containing the MoCA or MMSE combined with TOPF scores accounted for 58% and 49%, respectively, of the variance in obtained FSIQ. Both regression equations accurately estimated FSIQ to within 10 points in >75% of the sample. Both the MoCA and MMSE provide reasonable estimates of FSIQ. Prediction improves when these measures are combined with other estimates of FSIQ. We provide 4 equations designed to help clinicians interpret these screening measures.

Clinical and neuropsychological characteristics of euthymic bipolar patients having a history of severe suicide attempt.

Identifying bipolar patients at high-suicide risk is a major health issue. To improve their identification, we compared dimensional and neuropsychological profile of bipolar patients with or without history of suicide attempt, taking into account suicidal severity (i.e. admission to intensive ward). A total of 343 adult euthymic bipolar out-patients recruited in the French FondaMental Advanced Centres of Expertise for Bipolar Disorder were divided into three subgroups: 214 patients without history of suicide attempt, 88 patients with past history of non-severe suicide attempt and 41 patients with past history of severe suicide attempt. General intellectual functioning, speed of information processing, verbal learning and memory, verbal fluency and executive functioning were assessed. Severe suicide attempters had lower affective intensity and lability than non-severe attempters. Severe suicide attempters outperformed non-severe attempters for verbal learning and non-attempters for Stroop word reading part after adjustment for study centre, age, gender, educational level, antipsychotics use, depression score, anxious and addictive comorbidities. Neuropsychological tasks commonly used to assess bipolar patients do not seem accurate to identify suicide attempters in euthymic patients. In the future, decision-making and emotional recognition tasks should be assessed. Moreover, clinical and neuropsychological profiles should be considered together to better define suicidal risk.

Free thyroxine levels after very preterm birth and neurodevelopmental outcomes at age 7 years.

Preterm infants commonly have transient hypothyroxinemia of prematurity after birth, which has been associated with deficits in general intellectual functioning, memory, attention, and academic achievement. However, research has predominantly focused on thyroxine levels in the first 2 weeks of life and outcomes are limited to the preschool period. Our objective was to evaluate the relationships between free thyroxine (fT₄) levels over the first 6 weeks after very preterm (VPT) birth with cognitive functioning and brain development at age 7 years. A total of 83 infants born VPT (<30 weeks' gestation) had fT₄ concentrations measured postnatally and 2- and 6-week area under the curve (AUC) summary measures were calculated. Follow-up at age 7 years included a neuropsychological assessment and brain MRI. Univariable and multivariable regression modeling was used where AUC for fT₄ was the main predictor of neurodevelopmental outcome at age 7 years. Multivariable modeling revealed that higher, not lower, postnatal fT₄ levels (2-week AUC) were associated with poorer cognitive performances at age 7 years on tasks of verbal learning (P = .02), verbal memory (P = .03), and simple reaction time (P < .001). A similar pattern of results was found when the 6-week AUC was examined. No significant associations between postnatal fT₄ levels and brain volumes at age 7 years were identified. Results are contradictory to previous observations and suggest that after adjustment for confounders, higher postnatal fT₄ levels in VPT infants, rather than lower levels, may be a marker of adverse neuropsychological development in childhood.

Phenotypic cognitive impairment in late-onset delusional disorder

Previous use of heterogeneous diagnostic criteria and insensitive cognitive measures has impeded clarification of the extent and type of cognitive impairment specific to late-onset delusional disorder. We examined whether clinical presentations of late-onset delusional disorder are associated with prodromal or established dementia, and whether it might be a discrete clinical syndrome characterized by its own profile of cognitive impairment. Nineteen patients with late-onset delusional disorder from a hospital psychiatric service and 20 patients with dementia of the Alzheimer's type (AD) from an outpatient memory clinic were recruited in a consecutive case series. All patients underwent comprehensive neuropsychological assessment that included general intellectual function, executive function, new learning and delayed memory, language, processing speed, and visuo-perceptual skills. Late-onset delusional disorder patients showed moderate impairment to conceptual reasoning, visual object recognition, processing speed, and confrontation naming. Severe impairment appeared in visuo-perceptual planning and organization, and divided attention. Compared with the Alzheimer's disease (AD) group, the late-onset delusional disorder group demonstrated significantly poorer visuo-perceptual skills but a significantly better capacity to consolidate information into delayed memory. A high rate of marked cognitive impairment occurs in late-onset delusional disorder. There was evidence of a conceptual reasoning deficit, plus the presence of a visuo-perceptual impairment affecting object recognition. This impairment profile can explain the genesis and maintenance of the observed delusions. Understanding late-onset delusional disorder as other than a purely psychiatric phenomenon or a precursor to AD will lead to better assessment and management approaches.

Cognitive predictors of cognitive change following bilateral subthalamic nucleus deep brain stimulation in Parkinson’s disease

The beneficial effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN) for the motor symptoms in advanced Parkinson’s disease (PD) are well established. Early in PD, mild cognitive impairment is present in a proportion of patients. Hence, it can also be present in PD patients considered for DBS. The potential impact of even a modest decline post-surgically is a concern because it could result in impaired cognitive function. Therefore, attempts to determine which pre-operative cognitive measures predict post-operative cognitive change warrant further attention. We report our findings in a cohort of 30 routinely operated non-demented patients who underwent detailed neuropsychological assessments on average 7.1months before and 9.4months after STN DBS. We report the individual and group differences pre- and post-DBS. Stepwise regression analysis was used to analyse the best cognitive predictors of post-operative cognitive changes. We describe our data in relation to published normative data. Post-STN DBS, the immediate story recall component of verbal memory was the most affected cognitive function showing a significant decline in its group mean with a large effect size. The best predictors for this change were pre-surgical list learning and Full Scale Intelligence Quotient. These results suggest that non-demented patients, with even mild impairments in both general intellectual functions and list learning, may be at greater risk of decline in other aspects of verbal memory after STN DBS. Pre-existing mild executive dysfunction was not influenced post-operatively. These findings may help selection and consent for STN DBS.

Spotlight on the October 29 Issue

Patients with newly diagnosed childhood absence epilepsy had neuropsychological testing, including assessments of general intellectual functioning, attention, memory, executive function, and achievement. These children had a higher rate of pretreatment attentional deficits that persisted despite seizure freedom. Vigilant cognitive and behavioral assessment of children with absence epilepsy is warranted. See p. 1572; Editorial, p. 1564 Fatigue is common following stroke and may hinder rehabilitation. This longitudinal study found that fatigue during the acute phase after stroke predicted self-reported …

Effort Testing in Children: Can Cognitive and Symptom Validity Measures Differentiate Malingered Performances?

Recent efforts have contributed to significant advances in the detection of malingered performances in adults during cognitive assessment. However, children's ability to purposefully underperform has received relatively little attention. The purpose of the present investigation was to examine children's performances on common intellectual measures, as well as two symptom validity measures: the Test of Memory Malingering and the Dot-Counting Test. This was accomplished through the administration of measures to children ages 6 to 12 years old in randomly assigned full-effort (control) and poor-effort (treatment) conditions. Prior to randomization, children's general intellectual functioning (i.e., IQ) was estimated via administration of the Kaufman Brief Intellectual Battery-Second Edition (KBIT-2). Multivariate analyses revealed that the conditions significantly differed on some but not all administered measures. Specifically, children's estimated IQ in the treatment condition significantly differed from the full-effort IQ initially obtained from the same children on the KBIT-2, as well as from the IQs obtained in the full-effort control condition. These findings suggest that children are fully capable of willfully underperforming during cognitive testing; however, consistent with prior investigations, some measures evidence greater sensitivity than others in evaluating effort.

Neuropsychological and neurobehavioral outcome following childhood arterial ischemic stroke: Attention deficits, emotional dysregulation, and executive dysfunction

Objectives. To investigate neuropsychological and neurobehavioral outcome in children with arterial ischemic stroke (AIS).Background. Childhood stroke can have consequences on motor, cognitive, and behavioral development. We present a cross-sectional study of neuropsychological and neurobehavioral outcome at least one year poststroke in a uniquely homogeneous sample of children who had experienced AIS.Method. Forty-nine children with AIS aged 6 to 18 years were recruited from a specialist clinic. Neuropsychological measures of intelligence, reading comprehension, attention, and executive function were administered. A triangulation of data collection included questionnaires completed by the children, their parents, and teachers, rating behavior, executive functions, and emotions.Key Findings. Focal neuropsychological vulnerabilities in attention (response inhibition and dual attention) and executive function were found, beyond general intellectual functioning, irrespective of hemispheric side of stroke. Difficulties with emotional and behavioral regulation were also found. Consistent with an “early plasticity” hypothesis, earlier age of stroke was associated with better performance on measures of executive function.Conclusions. A significant proportion of children poststroke are at long-term risk of difficulties with emotional regulation, executive function, and attention. Data also suggest that executive functions are represented in widespread networks in the developing brain and are vulnerable to unilateral injury.

Selective neuropsychological impairments and related clinical factors in children with moyamoya disease of the transient ischemic attack type

Moyamoya disease is characterized by progressive narrowing of bilateral internal carotid arteries. Neuropsychological impairments are suspected due to frequent involvement of the frontotemporal areas. The present study thus aimed to investigate the pattern of neuropsychological function in children diagnosed with moyamoya disease. Thirteen children with moyamoya disease of the transient ischemic attack type received standardized neuropsychological tests that evaluate general intellectual function, verbal comprehension, perceptual organization, working memory, processing speed, episodic memory, category fluency and visuospatial function. Related clinical factors were also analyzed. The results showed single-domain cognitive impairment in around 15 % of patients and multiple-domain cognitive impairments in 23 % of patients. Selective impairments of episodic memory and processing speed were especially noted in those with younger age of onset and prolonged symptom duration. Neuropsychological impairments are not infrequent in children with moyamoya disease despite normal general intellectual functioning. The pattern of cognitive dysfunction is often associated with lesions in frontotemporal areas. Early detection and intervention shall be considered regarding cognitive outcome in pediatric group.

Aberrant basal ganglia metabolism in fragile X syndrome: a magnetic resonance spectroscopy study

BackgroundThe profile of cognitive and behavioral variation observed in individuals with fragile X syndrome (FXS), the most common known cause of inherited intellectual impairment, suggests aberrant functioning of specific brain systems. Research investigating animal models of FXS, characterized by limited or lack of fragile X mental retardation protein, (FMRP), has linked brain dysfunction to deficits in the cholinergic and glutamatergic systems. Thus, we sought to examine in vivo levels of neurometabolites related to cholinergic and glutamatergic functioning in males and females with FXS.MethodsThe study participants included 18 adolescents and young adults with FXS, and a comparison group of 18 individuals without FXS matched for age, sex and general intellectual functioning. Proton magnetic resonance spectroscopy (MRS) was used to assess neurometabolite levels in the caudate nucleus, a region known to be greatly enlarged and involved in abnormal brain circuitry in individuals with FXS. A general linear model framework was used to compare group differences in metabolite concentration.ResultsWe observed a decrease in choline (P = 0.027) and in glutamate + glutamine (P = 0.032) in the caudate nucleus of individuals with FXS, relative to individuals in the comparison group.ConclusionsThis study provides evidence of metabolite differences in the caudate nucleus, a brain region of potential importance to our understanding of the neural deficits underlying FXS. These metabolic differences may be related to aberrant receptor signaling seen in animal models. Furthermore, identification of the specific neurometabolites involved in FXS dysfunction could provide critical biomarkers for the design and efficacy tracking of disease-specific pharmacological treatments.

The Self- and Other-Deception Questionnaires-Intellectual Disabilities (SDQ-ID and ODQ-ID): Component analysis and reliability

The objectives of this research were to: (1) investigate the component structure and psychometric properties of the Self- and Other-Deception Questionnaires-Intellectual Disabilities (SDQ-ID and ODQ-ID), (2) examine the relationship between social desirability and IQ, and (3) compare social desirability scores of those with intellectual disabilities (IDs) and a history of criminal offending to the social desirability scores of participants with IDs and those without IDs and no such history, controlling for general intellectual functioning. Men with mild to borderline IDs detained within medium secure inpatient forensic mental health services (N=40) completed the SDQ-ID and ODQ-ID at Time 1 and then two-weeks later at Time 2. Data for the men with and without IDs and no known criminal offending history were taken from a previous study (N=60). Following exploratory Principal Components Analysis, the number of questionnaire items were reduced, and a two-factor structure was found for the SDQ-ID which was labelled: (1) Positive Self Representation and (2) Denial of Intrusive Thoughts. A two-factor structure was also found for the ODQ-ID and these two factors were labelled: (1) Denial of Negative Social Interaction and (2) Untrustworthiness. Both the SDQ-ID and ODQ-ID had acceptable internal consistency and test-retest reliability. Fifteen percent of the variance in SDQ-ID scores was explained by Full Scale IQ, while 21% of the variance in ODQ-ID scores was explained by Full Scale IQ. Between group comparisons controlling for intelligence did not yield any significant differences. The shortened SDQ-ID and ODQ-ID have promising psychometric properties, and their component structures appear robust. Differences between men with and without IDs on these two measures of social desirability can be accounted for by differences in general intellectual functioning.

Cognitive dysfunction and depression in Fabry disease: a systematic review

Fabry disease, an X-linked lysosomal storage disorder, leads to multi-organ dysfunction, including cerebrovascular disease and psychological disorders. However, the prevalence and pattern of associated cognitive dysfunction is not well understood. To investigate whether there is reliable evidence for neuropsychological impairment in patients with Fabry disease and which cognitive domains are affected. To estimate the prevalence of and factors associated with depression in patients with Fabry disease. Qualitative systematic review of the literature of studies conducting neuropsychological assessment or measuring the prevalence of depression in adults with Fabry disease using the preferred reporting items for systematic reviews and meta-analysis (PRISMA) guidelines where appropriate. There is some evidence for neuropsychological impairment in Fabry disease in executive functioning, information processing speed and attention, with preservation of: general intellectual functioning, memory, naming, perceptual functioning and global cognitive functioning. Prevalence rates of depression in Fabry disease ranged from 15% to 62%, with the largest study to date reporting a prevalence rate of 46%. The most common factor associated with depression was neuropathic pain, both directly and indirectly by affecting social and adaptive functioning. Our review suggests that Fabry disease may be associated with a characteristic pattern of cognitive deficits and a high prevalence of psychological disorders such as depression but highlights the limited available data. Exploring the nature of cognitive impairment in Fabry disease using standardised neuropsychological assessment, brain imaging and measures of depression is an important task for future research.

Number of antigens in early childhood vaccines and neuropsychological outcomes at age 7–10 years

Concerns have been raised that children may be receiving too many immunizations under the recommended schedule in the USA. We used a publicly available dataset to evaluate the association between antibody-stimulating proteins and polysaccharides from early childhood vaccines and neuropsychological outcomes at age 7-10 years. Children aged 7-10 years from four managed care organizations underwent standardized tests for domain-specific neuropsychological outcomes: general intellectual function, speech and language, verbal memory, attention and executive function, tics, achievement, visual spatial ability, and behavior regulation. Vaccination histories up to 24 months of age were obtained from medical charts, electronic records, and parents' records. Logistic regressions and structural equation modeling (SEM) were used to determine associations between total antigens up to 7, 12, and 24 months and domain-specific outcomes. On average, children (N = 1047) received 7266, 8127, and 10 341 antigens by ages 7, 12, and 24 months, respectively. For adjusted analyses, increase (per 1000) in the number of antigens was not associated with any neuropsychological outcomes. Antigen counts above the 10th percentile, compared with lower counts, were also not associated with any adverse outcomes. However, children with higher antigen counts up to 24 months performed better on attention and executive function tests (odds ratio for lower scores = 0.51, 95% confidence interval = 0.26, 0.99). Similar results were found with SEM analysis (b = 0.08, p = 0.02). We did not find any adverse associations between antigens received through vaccines in the first two years of life and neuropsychological outcomes in later childhood. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

General intellectual functioning as a buffer against theory-of-mind deficits in individuals at ultra-high risk for psychosis

The influence of neurocognition, including general intelligence, on theory of mind (ToM) among patients with schizophrenia spectrum disorder is controversial. The purpose of the present study was to identify the influences of the non-ToM cognition and general intelligence on ToM performance in individuals at ultra-high risk (UHR) for psychosis. Fifty-five UHR subjects and 58 healthy controls (HCs) completed neurocognitive, verbal, and nonverbal ToM tasks. UHR individuals showed poorer performance in the two verbal ToM tasks, the false-belief task and the strange-story tasks. Moreover, the UHR subjects displayed poorer recall on the interference list of the verbal learning test. Linear regression analysis revealed that neurocognitive functioning, including executive functioning, working memory, and general intelligence, accounted for significant amounts of the variance in the results for UHR individuals: 20.4% in the false-belief task, 44.0% in the strange-story task, and 49.0% in the nonverbal cartoon task. Neurocognition, including general intelligence, was not a significant contributor to performance on ToM tasks in HCs. ToM deficits were not noted in UHR individuals with above-average IQ scores (≥110) compared with UHR subjects with IQ scores less than 110, who displayed significant differences on all ToM tasks compared with HCs. The present results suggest that ToM deficits in UHR individuals are complex and may be influenced by non-ToM cognition. Our findings are discussed in relation to the role of neurocognitive abilities in ToM-related impairments in UHR individuals.

Occupational outcome in bipolar disorder is not predicted by premorbid functioning and intelligence

Bipolar disorder (BD), over the long term, can manifest a variety of outcomes depending on a number of different conditions. There is a need for further knowledge regarding preventive factors as well as predictors of the disabling course of the disorder. Studies regarding the impact on functional outcome of premorbid and current general intellectual function [intelligence quotient (IQ)] and premorbid functioning in BD patients are sparse. The present study addressed the role of premorbid functioning [assessed with the Premorbid Adjustment Scale (PAS)], intelligence, course of illness, and sociodemographics on occupational outcome in BD. Bipolar disorder patients were recruited consecutively from psychiatric units (outpatient and inpatient) in four major hospitals in Oslo, Norway [(N = 226: 64.4% bipolar I disorder (BD-I); 30.1% bipolar II disorder (BD-II); 5.5% bipolar disorder not otherwise specified (BD-NOS); 38.6% males]. The associations between current IQ, premorbid IQ [assessed using the National Adult Reading Test (NART)], PAS, clinical and sociodemographic characteristics, and receipt of disability benefit were analysed using descriptive statistics and logistic regression analyses. The number of hospitalizations for depressive episodes and illness duration was associated with a higher risk of receipt of disability benefit. PAS, premorbid and current IQ, as well as decline in IQ, did not explain the higher risk of receipt of disability benefits. Severe clinical course of BD was associated with receipt of disability benefit. Occupational outcome was unrelated to PAS, premorbid and current IQ, as well as decline in IQ. This suggests that the persistence of severe clinical symptoms, rather than global cognitive functioning, determines occupational outcome in BD and emphasizes the protective potential of early and continuous clinical treatment.

Cognitive outcomes in pediatric heart transplant recipients bridged to transplantation with ventricular assist devices

Ventricular assist devices (VADs) have been associated with high rates of neurologic injury in pediatric patients during the period of support, but the delayed consequences of this type of injury have not been described in the literature. In this study we assess cognitive outcomes with indices of general intellectual functioning, including working memory, processing speed, perceptual reasoning and verbal comprehension, for pediatric heart transplant recipients who required VAD support as a bridge to transplant (n = 9). We present an aggregate of these VAD patients combined with heart transplant recipients who did not require mechanical circulatory support (n = 11), and compare the performance of all transplant patients (n = 20) to typically developing, healthy comparators (n = 12). We also present a post hoc analysis of those transplant recipients with significant medical morbidity in the first year of life, referred to as the "high-risk" transplant group (n = 5), and compare them with the "low-risk" transplant group (n = 15) and the typically developing comparators (n = 12). The mean performance of the VAD patients was in the average range for each of the examined indices of cognitive functioning. A total of 11% of the VAD patients performed in the impaired range and 78% performed in the average range, with 11% in the superior range on measures of general intellectual functioning. The typically developing participants performed significantly better than the aggregated transplant recipients on all indices except verbal comprehension. Lower cognitive performance in the combined transplant group appears to be associated with medical morbidity in the first year of life. Despite significant neurologic risk factors, this cohort of pediatric patients who were bridged to transplant with VAD demonstrated resiliency in terms of cognitive outcomes. In this heterogeneous population, it is likely that multiple factors contributed to the cognitive outcomes. As VAD use becomes more common in pediatric patients, a prospective evaluation of cognitive outcomes is warranted.

Decreased fragile X mental retardation protein (FMRP) is associated with lower IQ and earlier illness onset in patients with schizophrenia

The purpose of this study was to investigate Fragile X Syndrome (FXS)-related mechanisms in schizophrenia, including CGG triplet expansion, FMR1 mRNA, and fragile X mental retardation protein (FMRP) levels in lymphocytes. We investigated 36 patients with schizophrenia and 30 healthy controls using Southern blot analysis, mRNA assay, and enzyme-linked immunosorbent assay (ELISA). General intellectual functions were assessed with the Wechsler Adult Intelligence Scale-III, and the clinical symptoms were evaluated with the Positive and Negative Syndrome Scale. Results revealed that, relative to healthy controls, CGG triplet size and FMR1 mRNA were unaltered in patients with schizophrenia. However, the FMRP level was significantly reduced in patients compared with controls. We found an association between lower FMRP levels, reduced IQ, and earlier illness onset in schizophrenia. Chlorpromazine-equivalent antipsychotic dose did not correlate with FMRP levels. These results raise the possibility of impaired translation of FMR1 mRNA, altered epigenetic regulation, or increased degradation of FMRP in schizophrenia, which may play a role in dysfunctional neurodevelopmental processes and impaired neuroplasticity.