Linear and non-linear analyses of Conner's Continuous Performance Test-II discriminate adult patients with attention deficit hyperactivity disorder from patients with mood and anxiety disorders

Diagnostic Utility of Conners Continuous Performance Test-3 for Attention Deficit/Hyperactivity Disorder: A Systematic Review

OBJECTIVE

To review the literature on the utility of the Conners CPT-3 in persons with ADHD.

METHODS

A systematic review was conducted. Six databases were searched using inclusion criteria: research studies, year 2000+, English, and ages 8+. Two raters independently screened 1,480 title/abstracts and subsequently reviewed 399 full texts. Data extraction and critical appraisal were conducted. Reflective thematic analysis through inductive coding identified qualitative themes.

RESULTS

Thirteen studies met inclusion criteria with five themes identified. Five studies found CPT-3 was a weak or poor predictor of ADHD diagnosis while two found it was an adequate predictor. Two studies found CPT-3 could differentiate clients with comorbid ADHD/anxiety from ADHD or ADHD from obsessive-compulsive disorder. One found CPT-3 could not differentiate ADHD from ASD or comorbid ADHD/ASD.

CONCLUSIONS

Results revealed CPT-3 as a standalone measure is a weak or poor predictor of ADHD. Multiple measures for evaluating persons with ADHD are recommended.

A systematic review of the utility of continuous performance tests among adults with ADHD

OBJECTIVE

The clinical utility of continuous performance tests (CPTs) among adults with attention-deficit/hyperactivity disorder (ADHD) has increasingly been brought under question. Therefore, the objective of this study was to systematically review the literature to investigate the clinical utility of various commercially available CPTs, including the Conner's Continuous Performance Test (CCPT), Test of Variables of Attention (TOVA), Gordon Diagnostic System (GDS), and Integrated Visual and Auditory Continuous Performance Test (IVA) in the adult ADHD population.

METHODS

This systematic review followed the a priori PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Articles were gathered from PsycINFO, PsycARTICLES, Academic Search Complete, and Google Scholar on 11 April 2022. Sixty-nine articles were included in the final review. Risk of bias was assessed using the National Institute of Health Quality Assessment Took for Observational Cohort and Cross-Sectional Studies.

RESULTS

Most articles demonstrated high risk of bias, and there was substantial heterogeneity across studies. Overall, the reviewed CPTs appeared to have limited diagnostic utility and classification accuracy. Although many studies showed differing scores between adults with ADHD and comparison groups, findings were not consistent. Characteristics of CPT performances among adults with ADHD were mixed, with little consistency and no evidence of a clear profile of performances; however, CCPT commission errors appeared to have the most utility when used a treatment or experimental outcome measure, compared to other CCPT scores.

CONCLUSION

Overall, CPTs should not be used in isolation as a diagnostic test but may be beneficial when used as a component of a comprehensive assessment.

Impact of Emotions on Test of Variables of Attention(TOVA) Performance in a Pediatric Clinical Population: A Retrospective Study

BACKGROUND

Continuous Performance Tests, like the Test of Variables of Attention (TOVA), are commonly used to assess attention processes in clinical settings. Although a few previous studies have explored the effects of emotions on the outcome of such tests, the results are scarce and contradictory at times.

OBJECTIVE

Through this retrospective study, we  aimed to explore the correlation between performance on the TOVA and parent-reported emotional symptoms in youth.

METHODS

We used preexisting datasets of Mood and Feelings Questionnaire, Screen for Child Anxiety Related Disorders, and Vanderbilt Attention-Deficit/Hyperactivity Disorder Diagnostic Rating Scale as well as preexisting results from the TOVA test from 216 patients aged between 8 and 18 years. Pearson's correlation coefficients, as well as linear regression models, were computed to examine the association between depressive and anxiety symptoms and the four indices of TOVA (response time variability, response time, commission errors, and omission errors). Additionally, we used generalized estimating equations to determine whether the reported emotional symptoms affect the TOVA outcome differently as the test progresses.

RESULTS

Our results showed no significant effect of the reported emotional symptoms on the TOVA results even when controlling for sex or reported inattention and hyperactivity.

CONCLUSION

TOVA results do not seem to be affected by emotional symptoms in youth. This being said, future studies should also explore other factors that can affect the performance on the TOVA, like motor disability, sleepiness, or neurodevelopmental disorders affecting cognitive abilities.

The efficacy of mindfulness-based intervention in ameliorating externalizing behaviors and attentional concerns among college students

Objective: The purpose of this study was to investigate the efficacy of a mindfulness-based intervention among college students with externalizing behaviors and attentional problems. Participants: Three students attending their first year in college received mindfulness-based stress reduction (MBSR) intervention and data were collected pre-intervention, during the intervention, post-intervention, and follow-up. Methods: The study utilized a single-case design (SCD). Data were collected via the Conners continuous performance test, Third Edition (CPT-3), the Conners Continuous Auditory Test of Attention (CATA), the Behavioral Assessment Scale for Children, Flex Monitor, Third Edition (BASC-3 FM), and the Mindfulness Attention Awareness Scale (MAAS). Results: Data were analyzed by calculating standard error of the difference, reliable change index, non-overlap of all pairs (NAP), and Tau-U. Conclusions: The results of this study strongly suggest that mindfulness may be an effective intervention for addressing externalizing behaviors and attentional problems among first-year college students.

Conner's Continuous Performance Test and Adult ADHD: A Systematic Literature Review

OBJECTIVE

ADHD is a neurodevelopmental disorder affecting millions of adults worldwide. Continuous performance tests (CPTs) are widely used as assessment and diagnostic tools; however, their use in diagnosing undiagnosed ADHD in adults has been questioned due to their lack of specificity and sensitivity. This review sought to outline relevant findings concerning the diagnostic utility of the Conner's Continuous Performance Test (CCPT) in adults.

METHOD

This systematic review followed the a priori guide outlined by the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. Articles were gathered from PsycINFO, PsycArticles, Cochrane, Scopus, Google Scholar, and PubMed.

RESULTS

Thirty-five articles were reviewed and analyzed. Most articles reviewed used outpatient and university populations. Moderate reliability, subpar discriminant and ecological validity, and mixed sensitivity and specificity were noted.

CONCLUSION

The results of this review lend support to previous critiques of the CCPT's diagnostic and utility as a treatment measure.

The Conners Continuous Performance Test CPT3™: Is it a reliable marker to predict neurocognitive dysfunction in Myalgic encephalomyelitis/chronic fatigue syndrome?

Introduction

The main objective is to delimit the cognitive dysfunction associated with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) in adult patients by applying the Continuous Performance Test (CPT3^™). Additionally, provide empirical evidence on the usefulness of this computerized neuropsychological test to assess ME/CFS.

Method

The final sample (n = 225; 158 Patients/67 Healthy controls) were recruited in a Central Sensitization Syndromes (CSS) specialized unit in a tertiary hospital. All participants were administered this neuropsychological test.

Results

There were significant differences between ME/CFS and healthy controls in all the main measures of CPT3^™. Mainly, patients had a worse indicator of inattentiveness, sustained attention, vigilance, impulsivity, slow reaction time, and more atypical T-scores, which is associated with a likelihood of having a disorder characterized by attention deficits, such as Attention Deficit Hyperactivity Disorder (ADHD). In addition, relevant correlations were obtained between the CPT3^™ variables in the patient's group. The most discriminative indicators of ME/CFS patients were Variability and Hit Reaction Time, both measures of response speed.

Conclusion

The CPT3^™ is a helpful tool to discriminate neurocognitive impairments from attention and response speed in ME/CFS patients, and it could be used as a marker of ME/CFS severity for diagnosing or monitoring this disease.

Objective assessment of motor activity in a clinical sample of adults with attention-deficit/hyperactivity disorder and/or cyclothymic temperament

BACKGROUND

Most research on patterns of motor activity has been conducted on adults with mood disorders, but few studies have investigated comorbid attention-deficit/hyperactivity disorder (ADHD) or temperamental factors that may influence the clinical course and symptoms. Cyclothymic temperament (CT) is particularly associated with functional impairment. Clinical features define both disorders, but objective, biological markers for these disorders could give important insights with regard to pathophysiology and classification.

METHODS

Seventy-six patients, requiring diagnostic evaluation of ADHD, mood or anxiety disorders were recruited. A comprehensive diagnostic evaluation, including the CT scale of the Temperament Evaluation of Memphis, Pisa, Paris and San Diego - Auto-questionnaire (TEMPS-A), neuropsychological tests and actigraphy, was performed. ADHD was diagnosed according to the DSM-IV criteria. There was a range of different conditions in this clinical sample, but here we report on the presence of CT and ADHD in relation to motor activity. Twenty-nine healthy controls were recruited. We analyzed motor activity time series using linear and nonlinear mathematical methods, with a special focus on active and inactive periods in the actigraphic recordings.

RESULTS

Forty patients fulfilled the criteria for ADHD, with the remainder receiving other psychiatric diagnoses (clinical controls). Forty-two patients fulfilled the criteria for CT. Twenty-two patients fulfilled the criteria for ADHD and CT, 18 patients met the criteria for ADHD without CT, and 15 patients had neither. The ratio duration of active/inactive periods was significantly lower in patients with CT than in patients without CT, in both the total sample, and in the ADHD subsample.

CONCLUSIONS

CT is associated with objectively assessed changes in motor activity, implying that the systems regulating motor behavior in these patients are different from both healthy controls and clinical controls without CT. Findings suggest that actigraphy may supplement clinical assessments of CT and ADHD, and may provide an objective marker for CT.

What can we learn about performance validity from TOVA response profiles?

Given the functional impairments associated with Attention Deficit/Hyperactivity Disorder (AD/HD), a valid diagnosis is important. However, particularly when carried out in adulthood, the diagnostic process can be challenging and is complicated by conclusive evidence that a proportion of individuals referred for evaluation of AD/HD exaggerate or feign their symptoms. Relatively few methods, however, exist to identify such feigning. While continuous performance tests (CPTs) may provide useful information regarding performance validity, the question remains as to whether there are consistent patterns of exaggeration demonstrated by those feigning AD/HD. Thus, this study used cluster analysis to determine whether valid and reliable performance clusters would emerge based on CPT performance. Using archival data from a university-based AD/HD screening clinic, we investigated the performance of 305 adults on the Test of Variables of Attention (TOVA). Three profiles emerged, including one cluster who demonstrated exceptionally low performance on the TOVA, exceptionally high reports of AD/HD symptomology, and higher rates of failure on symptom and performance validity tests. The implication from our analysis is that this group most likely represents individuals who were exaggerating or magnifying their difficulties. The results reaffirm previous research showing that performance profiles on a continuous performance test can be used as an indicator of credible performance.

Differentiation of ADHD and Depression Based on Cognitive Performance

Objective: The aim of this study was to assess whether self-report scales and neuropsychological tests used for adult patients with ADHD can help to distinguish between ADHD-specific and depressive symptoms. Method: In a cross-sectional design, differences in self-report questionnaires and neuropsychological tests among clinical subgroups and healthy controls (HC) were evaluated. Patients in clinical groups were diagnosed with major depressive disorder (MDD) or ADHD with or without depressive symptoms according to Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV) guidelines. Results: The Hyperactivity subscales of the Conners' Adult ADHD Rating Scale (CAARS) differed between MDD and ADHD, whereas self-concept and inattention scales even distinguished comorbidity subgroups within the ADHD population. A reduced alertness and higher variations in reaction times measured by performance tests indicated problems in sustained attention in ADHD patients compared with HC. Conclusion: The diagnostic process of ADHD, and thereby the distinction from other symptom-overlapping, comorbid mental disorders, might be improved by utilizing ADHD-specific self-report questionnaires and neuropsychological tests, which are short, cost-effective, and standardized screening methods.

Individual Variability in Reaction Time and Prediction of Clinical Response to Methylphenidate in Adult ADHD: A Prospective Open Label Study Using Conners' Continuous Performance Test II

Objective: The aim of this study was to examine whether reaction time parameters in adult patients with ADHD could predict their response to methylphenidate (MPH). Method: Previously unmedicated patients (N = 123) were administered the Conners' Continuous Performance Test II (CPT II) at baseline and after 6 weeks of treatment with immediate-release MPH. In addition to traditional CPT measures, we extracted intraindividual raw data and analyzed time series using linear and nonlinear mathematical models. Results: Clinical responders, assessed with the Clinical Global Impression-Improvement scale, showed significant normalization of target failures, reduced variability and skewness, and increased complexity of reaction time series after 6 weeks of treatment, while nonresponders showed no significant changes. Prior to treatment, responders had significantly higher variability and skewness, combined with lower complexity, compared with nonresponders. Conclusion: These results show that the CPT test is useful in the evaluation of treatment response to MPH.

Diurnal variation of motor activity in adult ADHD patients analyzed with methods from graph theory

Attention-deficit /hyperactivity disorder (ADHD) is a common neurodevelopmental syndrome characterized by age-inappropriate levels of motor activity, impulsivity and attention. The aim of the present study was to study diurnal variation of motor activity in adult ADHD patients, compared to healthy controls and clinical controls with mood and anxiety disorders. Wrist-worn actigraphs were used to record motor activity in a sample of 81 patients and 30 healthy controls. Time series from registrations in the morning and evening were analyzed using measures of variability, complexity and a newly developed method, the similarity algorithm, based on transforming time series into graphs. In healthy controls the evening registrations showed higher variability and lower complexity compared to morning registrations, however this was evident only in the female controls. In the two patient groups the same measures were not significantly different, with one exception, the graph measure bridges. This was the measure that most clearly separated morning and evening registrations and was significantly different both in healthy controls and in patients with a diagnosis of ADHD. These findings suggest that actigraph registrations, combined with mathematical methods based on graph theory, may be used to elucidate the mechanisms responsible for the diurnal regulation of motor activity.

Associations of executive and functional outcomes with full-score intellectual quotient among ADHD adults

Associations between executive and functional impairment, intelligence, and attention deficit hyperactivity disorder (ADHD) have been scarcely investigated among adult populations and lead to inconsistent results. This study tested the impact of intellectual level on executive and functional impairment in a clinical sample of adults diagnosed with ADHD. Participants were recruited in a specialized center for the diagnosis and treatment of ADHD (n=66, mean age=27.9 ± 10.8). Measures included intellectual quotient (IQ, Wechsler Adult Intelligence Scale) categorized as ≤110 or >110, the continuous performance test (CPT3^TM), grade retention, educational attainment, and having an activity (job or studies). Participants with a higher IQ had significantly better functional outcomes than participants with a standard IQ: higher educational attainment, lower grade retention, and often having an activity. Participants with higher IQ performed significantly better on all CPT variables assessing executive functioning. Intelligence seemed to work as a protective factor for executive and functional outcomes in a clinical population of ADHD adults and might reduce long-lasting detrimental consequences in life.

Vulnerability in Executive Functions to Sleep Deprivation Is Predicted by Subclinical Attention-Deficit/Hyperactivity Disorder Symptoms

BACKGROUND

Sleep loss results in state instability of cognitive functioning. It is not known whether this effect is more expressed when there is an increased cognitive demand. Moreover, while vulnerability to sleep loss varies substantially among individuals, it is not known why some people are more affected than others. We hypothesized that top-down regulation was specifically affected by sleep loss and that subclinical inattention and emotional instability traits, related to attention-deficit/hyperactivity disorder symptoms, predict this vulnerability in executive function and emotion regulation, respectively.

METHODS

Healthy subjects (ages 17-45 years) rated trait inattention and emotional instability before being randomized to either a night of normal sleep (n = 86) or total sleep deprivation (n = 87). Thereafter, they performed a neutral and emotional computerized Stroop task, involving words and faces. Performance was characterized primarily by cognitive conflict reaction time and reaction time variability (RTV), mirroring conflict cost in top-down regulation.

RESULTS

Sleep loss led to increased cognitive conflict RTV. Moreover, a higher level of inattention predicted increased cognitive conflict RTV in the neutral Stroop task after sleep deprivation (r = .30, p = .0055) but not after normal sleep (r = .055, p = .65; interaction effect β = 6.19, p = .065). This association remained after controlling for cognitive conflict reaction time and emotional instability, suggesting domain specificity. Correspondingly, emotional instability predicted cognitive conflict RTV for the emotional Stroop task only after sleep deprivation, although this effect was nonsignificant after correcting for multiple comparisons.

CONCLUSIONS

Our findings suggest that sleep deprivation affects cognitive conflict variability and that less stable performance in executive functioning may surface after sleep loss in vulnerable individuals characterized by subclinical symptoms of inattention.

Does the Continuous Performance Test Predict ADHD Symptoms Severity and ADHD Presentation in Adults?

Objective: Our study aimed to provide empirical evidence on the usefulness of one of the most popular neuropsychological tests, the Continuous Performance Test (CPT), as a marker of ADHD severity and presentations among adults. Method: ADHD participants were recruited in a specialized center for the diagnosis and treatment of adults suffering from ADHD (n = 201). Measures included the CPT3™ and ADHD symptoms using a clinical interview and self-reported measures. Results: Only 51.7% of the participants were classified as likely to have a disorder characterized by attention deficit, such as ADHD, by the CPT. The relationships between CPT variables and ADHD symptoms were small. The classification error was 80.3% for the inattentive presentation and 22.5% for the hyperactive presentation when using the CPT to identify ADHD presentations. Conclusion: There was no evidence of the clinical utility of the CPT to assess or monitor ADHD in adult populations diagnosed and treated for ADHD.

The Novelty of Bupropion As a Dopaminergic Antidepressant for the Treatment of Adult Attention Deficit Hyperactive Disorder

Attention deficit hyperactive disorder (ADHD), a hyperactivity disorder prevalent among children may continue as an adulthood attention deficit. To date, treating an individual with an adult ADHD may be an arduous task as it involves numerous challenges, which include a need for high index of suspicion to diagnose this medical condition. Many psychiatric disorders masquerade as ADHD and delay the necessary assessment and proper treatment for this debilitating medical disorder. Adult ADHD is often misdiagnosed (or under diagnosed) due to the fact that this medical condition is being masked by the patients' high level of intellectual achievement. As the ADHD in adult persists, it may end-up with impairment in the personal-social-occupational function in which the management becomes a great challenge. The treatment of ADHD can be optimized by using various drugs targets agents like norepinephrine-dopamine reuptake inhibitor (NDRI), with or without psycho stimulants like methylphenidate, which is marketed as Ritalin. Bupropion, an NDRI has a novel effect on ADHD as the molecule exerts its effects by modulating the reward-pleasure mesolimbic dopaminergic system and at the same time regulates the elevating mood dimension of the noradrenergic neurotransmission. The role of Bupropion in the neural and psychopharmacological perspective treatment of ADHD was deliberated. The present review highlights the novel effects of Bupropion in ADHD treatment, together with the help of other successful bio-psycho-social measures. This may be of immense benefit to the psychiatrists for treating their patients.

Can neuropsychological testing facilitate differential diagnosis between at-risk mental state (ARMS) for psychosis and adult attention-deficit/hyperactivity disorder (ADHD)?

Background:

Patients with an at-risk mental state (ARMS) for psychosis and patients with attention-deficit/hyperactivity disorder (ADHD) have many overlapping signs and symptoms and hence can be difficult to differentiate clinically. The aim of this study was to investigate whether the differential diagnosis between ARMS and adult ADHD could be improved by neuropsychological testing.

Methods:

168 ARMS patients, 123 adult ADHD patients and 109 healthy controls (HC) were recruited via specialized clinics of the University of Basel Psychiatric Hospital. Sustained attention and impulsivity were tested with the Continuous Performance Test, verbal learning and memory with the California Verbal Learning Test, and problem solving abilities with the Tower of Hanoi Task. Group differences in neuropsychological performance were analyzed using generalized linear models. Furthermore, to investigate whether adult ADHD and ARMS can be correctly classified based on the pattern of cognitive deficits, machine learning (i.e. random forests) was applied.

Results:

Compared to HC, both patient groups showed deficits in attention and impulsivity and verbal learning and memory. However, in adult ADHD patients the deficits were comparatively larger. Accordingly, a machine learning model predicted group membership based on the individual neurocognitive performance profile with good accuracy (AUC = 0.82).

Conclusions:

Our results are in line with current meta-analyses reporting that impairments in the domains of attention and verbal learning are of medium effect size in adult ADHD and of small effect size in ARMS patients and suggest that measures of these domains can be exploited to improve the differential diagnosis between adult ADHD and ARMS patients.

Linking alpha oscillations, attention and inhibitory control in adult ADHD with EEG neurofeedback

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Resting alpha power is reduced in adult ADHD suggesting cortical hyper-activation.

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Adult ADHD patients successfully reduce alpha power during neurofeedback.

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A post-neurofeedback rebound normalizes alpha power in adult ADHD.

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Alpha power rebound correlates with improvement of inhibitory control in adult ADHD.

Abnormal patterns of electrical oscillatory activity have been repeatedly described in adult ADHD. In particular, the alpha rhythm (8–12 Hz), known to be modulated during attention, has previously been considered as candidate biomarker for ADHD. In the present study, we asked adult ADHD patients to self-regulate their own alpha rhythm using neurofeedback (NFB), in order to examine the modulation of alpha oscillations on attentional performance and brain plasticity. Twenty-five adult ADHD patients and 22 healthy controls underwent a 64-channel EEG-recording at resting-state and during a Go/NoGo task, before and after a 30 min-NFB session designed to reduce (desynchronize) the power of the alpha rhythm. Alpha power was compared across conditions and groups, and the effects of NFB were statistically assessed by comparing behavioral and EEG measures pre-to-post NFB. Firstly, we found that relative alpha power was attenuated in our ADHD cohort compared to control subjects at baseline and across experimental conditions, suggesting a signature of cortical hyper-activation. Both groups demonstrated a significant and targeted reduction of alpha power during NFB. Interestingly, we observed a post-NFB increase in resting-state alpha (i.e. rebound) in the ADHD group, which restored alpha power towards levels of the normal population. Importantly, the degree of post-NFB alpha normalization during the Go/NoGo task correlated with individual improvements in motor inhibition (i.e. reduced commission errors) only in the ADHD group. Overall, our findings offer novel supporting evidence implicating alpha oscillations in inhibitory control, as well as their potential role in the homeostatic regulation of cortical excitatory/inhibitory balance.

A Comparison of Virtual Reality Classroom Continuous Performance Tests to Traditional Continuous Performance Tests in Delineating ADHD: a Meta-Analysis

Computerized continuous performance tests (CPTs) are commonly used to characterize attention in attention deficit-hyperactivity disorder (ADHD). Virtual classroom CPTs, designed to enhance ecological validity, are increasingly being utilized. Lacking is a quantitative meta-analysis of clinical comparisons of attention performance in children with ADHD using virtual classroom CPTs. The objective of the present systematic PRISMA review was to address this empirical void and compare three-dimensional (3D) virtual classroom CPTs to traditional two-dimensional (2D) CPTs. The peer-reviewed literature on comparisons of virtual classroom performance between children with ADHD and typically developing children was explored in six databases (e.g., Medline). Published studies using a virtual classroom to compare attentional performance between children with ADHD and typically developing children were included. Given the high heterogeneity with modality comparisons (i.e., computerized CPTs vs. virtual classroom CPTs for ADHD), both main comparisons included only population comparisons (i.e., control vs. ADHD) using each CPT modality. Meta-analytic findings were generally consistent with previous meta-analyses of computerized CPTs regarding the commonly used omission, commission, and hit reaction time variables. Results suggest that the virtual classroom CPTs reliably differentiate attention performance in persons with ADHD. Ecological validity implications are discussed pertaining to subtle meta-analytic outcome differences compared to computerized 2D CPTs. Further, due to an inability to conduct moderator analyses, it remains unclear if modality differences are due to other factors. Suggestions for future research using the virtual classroom CPTs are provided.

Adolescent maturation of the relationship between cortical gyrification and cognitive ability

There are changes to the degree of cortical folding from gestation through adolescence into young adulthood. Recent evidence suggests that degree of cortical folding is linked to individual differences in general cognitive ability in healthy adults. However, it is not yet known whether age-related cortical folding changes are related to maturation of specific cognitive abilities in adolescence. To address this, we examined the relationship between frontoparietal cortical folding as measured by a Freesurfer-derived local gyrification index (lGI) and performance on subtests from the Wechsler Abbreviated Scale of Intelligence and scores from Conner's Continuous Performance Test-II in 241 healthy adolescents (ages 12-25 years). We hypothesized that age-related lGI changes in the frontoparietal cortex would contribute to cognitive development. A secondary goal was to explore if any gyrification-cognition relationships were either test-specific or sex-specific. Consistent with previous studies, our results showed a reduction of frontoparietal local gyrification with age. Also, as predicted, all cognitive test scores (i.e., Vocabulary, Matrix Reasoning, the CPT-II Commission, Omission, Variabiltiy, d') showed age × cognitive ability interaction effects in frontoparietal and temporoparietal brain regions. Mediation analyses confirmed a causal role of age-related cortical folding changes only for CPT-II Commission errors. Taken together, the results support the functional significance of cortical folding, as well as provide the first evidence that cortical folding maturational changes play a role in cognitive development.

Patterns of motor activity in spontaneously hypertensive rats compared to Wistar Kyoto rats

BACKGROUND

Increased motor activity is a defining characteristic of patients with ADHD, and spontaneously hypertensive rats have been suggested to be an animal model of this disorder. In the present study, we wanted to use linear and non-linear methods to explore differences in motor activity patterns in SHR/NCrl rats compared to Wistar Kyoto (WKY/NHsd) rats.

METHODS

A total number of 42 rats (23 SHR/NCrl and 19 WKY/NHsd, male and female) were tested. At PND 51, the animals' movements were video-recorded during an operant test procedure that lasted 90 min. Total activity level and velocity (mean and maximum), standard deviation (SD) and root mean square successive differences (RMSSD) were calculated. In addition, we used Fourier analysis, autocorrelations and two measures of complexity to characterize the time series; sample entropy and symbolic dynamics.

RESULTS

The SHR/NCrl rats showed increased total activity levels in addition to increased mean and maximum velocity of movements. The variability measures, SD and RMSSD, were markedly lower in the SHR/NCrl compared to the WKY/NHsd rats. At the same time, the SHR/NCrl rats displayed a higher complexity of the time series, particularly with regard to the total activity level as evidenced by analyses of sample entropy and symbolic dynamics. Autocorrelation analyses also showed differences between the two strains. In the Fourier analysis, the SHR/NCrl rats had an increased variance in the high frequency part of the spectrum, corresponding to the time period of 9-17 s.

CONCLUSION

The findings show that in addition to increased total activity and velocity of movement, the organization of behavior is different in SHR/NCrl relative to WKY/NHsd controls. Compared to controls, behavioral variability is reduced in SHR/NCrl at an aggregate level, and, concomitantly, more complex and unpredictable from moment-to-moment. These finding emphasize the importance of the measures and methods used when characterizing behavioral variability. If valid for ADHD, the results indicate that decreased behavioral variability can co-exist with increased behavioral complexity, thus representing a challenge to current theories of variability in ADHD.