Continuous performance tests: a comparison of modalities

Prenatal exposure to mixtures of per- and polyfluoroalkyl substances and organochlorines affects cognition in adolescence independent of postnatal exposure

BACKGROUND

Studies on cognitive and neurodevelopmental outcomes have shown inconsistent results regarding the association with prenatal exposure to perfluoroalkyl substance (PFAS) and organochlorines. Assessment of mixture effects of correlated chemical exposures that persist in later life may contribute to the unbiased evaluation and understanding of dose-response associations in real-life exposures.

METHODS

For a subset of the 4th Flemish Environment and Health Study (FLEHS), concentrations of four PFAS and six organochlorines were measured in respectively 99 and 153-160 cord plasma samples and 15 years later in adolescents' peripheral serum by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Sustained and selective attention were measured at 14-15 years with the Continuous Performance Test (CPT) and Stroop Test as indicators of potential neurodevelopmental deficits. Quantile g-computation was applied to assess the joint associations between prenatal exposure to separate and combined groups of PFAS and organochlorines and performance in the CPT and Stroop Test at adolescence. Subsequently, individual effects of each chemical compound were analyzed in mixed effects models with two sets of covariates. Analytical data at birth and at the time of cognitive assessment allowed for off-setting postnatal exposure.

RESULTS

In mixtures analysis, a simultaneous one-quantile increase in the natural log-transformed values of PFAS and organochlorines combined was associated with a decrease in the mean reaction time (RT) and the reaction time variability (RTV) in the CPT (β = -15.54, 95% CI:-29.64, -1.45, and β = -7.82, 95% CI: -14.97, -0.67 respectively) and for the mixture of PFAS alone with RT (β = -11.94, 95% CI: -23.29, -0.60). In the single pollutant models, these results were confirmed for the association between perfluorohexanesulfonate (PFHxS) with RT (β = -17.95, 95% CI = -33.35, -2.69) and hexachlorobenzene with RTV in the CPT (β = -5.78, 95% CI: -10.39, -0.76). Furthermore, the participants with prenatal exposure above the limit of quantification for perfluorononanoic acid (PFNA) had a significantly shorter RT and RTV in the CPT (β = -23.38, 95% CI: -41.55, -5.94, and β = -9.54, 95% CI: -19.75, -0.43, respectively).

CONCLUSION

Higher prenatal exposure to a PFAS mixture and a mixture of PFAS and organochlorines combined was associated with better sustained and selective attention during adolescence. The associations seemed to be driven by PFHxS and were not linked to exposure levels at the time of assessment.

Sensory processing abilities and their impact on disease severity in children with attention-deficit hyperactivity disorder

Objectives

Although several studies have shown sensory processing abnormalities in pediatric subjects with attention-deficit hyperactivity disorder (ADHD), there is significant heterogeneity among their results.

Materials and Methods

This study was performed to compare the sensory processing abilities of children and adolescents with and without ADHD aged 6-15 years and to correlate the sensory processing problems in these patients, with the symptom profile and severity of ADHD. While child sensory profile-2 (SP-2) was used to assess, the sensory processing abilities of ADHD patients, revised Connor's parent rating scale revised, Malin's intelligence scale for Indian children, grade level assessment device, and child behavior checklist were used to assess ADHD symptom severity, intelligence, learning, and behavioral problems, respectively.

Results

A total of 66 ADHD patients enrolled (60 boys), 22 (28%), 7 (9%), and 49 (63%) cases were the ADHD-hyperactive-impulsive (ADHD-HI), ADHD-inattentive, and ADHD-combined (ADHD-C) types, respectively, and 33 typically developing controls. The ADHD patients had a significantly low raw score on most of the factors, sections, and response patterns of SP-2 (P < 0.05), but only four and one ADHD patients had auditory and visual processing scores outside the normal clinical range. There was a trend toward higher scores in the children with ADHD-C and ADHD-HI subtypes. There was a moderate negative correlation between hyperactivity/impulsivity T-score and auditory processing scores in the SP (P < 0.05, r = -0.43). We observed a negative correlation, although weak, between visual processing scores and hyperactivity/impulsivity and a positive correlation between the severity of conduct disorder-related problems, oppositional defiant problems, anxiety problems, and auditory as well as tactile processing scores (P < 0.05). In the quadrant score summary, the scores for all four types, that is, sensory sensitivity, low registration, sensation avoiding, and sensation seeking, were significantly more in the ADHD group, as compared to healthy controls.

Conclusion

Sensory processing abilities in ADHD children differ from that of typically developing children when objectively assessed, although most of the ADHD children had scores in the clinically normal range. The sensory processing profile also has an impact on the severity and comorbidity profile of ADHD patients.

Common principles underlie the fluctuation of auditory and visual sustained attention

Sustained attention plays an important role in adaptive behaviours in everyday activities. As previous studies have mostly focused on vision, and attentional resources have been thought to be specific to sensory modalities, it is still unclear how mechanisms of attentional fluctuations overlap between visual and auditory modalities. To reduce the effects of sudden stimulus onsets, we developed a new gradual-onset continuous performance task (gradCPT) in the auditory domain and compared dynamic fluctuation of sustained attention in vision and audition. In the auditory gradCPT, participants were instructed to listen to a stream of narrations and judge the gender of each narration. In the visual gradCPT, they were asked to observe a stream of scenery images and indicate whether the scene was a city or mountain. Our within-individual comparison revealed that auditory and visual attention are similar in terms of the false alarm rate and dynamic properties including fluctuation frequency. Absolute timescales of the fluctuation in the two modalities were comparable, notwithstanding the difference in stimulus onset asynchrony. The results suggest that fluctuations of visual and auditory attention are underpinned by common principles and support models with a more central, modality-general controller.

Feasibility and Neurobehavioral Changes of 10-Day Simulated Microgravity in Acute Ischemic Stroke Patients

OBJECTIVE

The aim of the study was to investigate feasibility and functional changes of simulated microgravity with 6-degree head-down-tilt (HDT) bed rest in acute ischemic stroke.

DESIGN

Patients without lesions in the cingulate cortex and/or cerebellum were enrolled. They underwent HDT for 30 minutes twice per day for 10 weekdays. Systolic blood pressure, diastolic blood pressure, and heart rate were measured before the HDT, immediately after, and also 30 minutes after the stop. Mini-Mental State Examination, Geriatric Depression Scale, Neurobehavioral Tests (i.e., span test, finger-tapping test, continuous performance test, and trail-making test) were conducted before and after the 10-day HDT.

RESULTS

One male and four female patients (median age = 64.6 yrs [SD = 10.5 yrs]) were recruited. Changes in the finger-tapping test (57.80 [SD = 40.96 ] vs. 85.80 [SD = 0.46], P = 0.08) and in the digit span backward test (3.60 [SD = 1.14] vs. 1.42 [SD = 1.75], P = 0.07) were noticed. Few changes were found in other scales. No significant changes in systolic blood pressure, diastolic blood pressure, or heart rate were observed, and no adverse effects occurred.

CONCLUSIONS

The 6-degree HDT revealed no adverse effects on the cardiovascular system, showing nonsignificant increment in the finger-tapping test (representative of motor speed and performance) and nonsignificant reduction in the digit backward span test (representative of spatial memory).

Auditory and Visual Continuous Performance Tests

Elementary school children in three grade groups (Grades K/1, 3, and 5/6) completed either the auditory or the visual 1/9 vigilance task from the Gordon Diagnostic System (GDS) as well as subtests from the Wechsler Intelligence Scale for Children–Third Edition and auditory or visual processing subtests from the Woodcock-Johnson Tests of Cognitive Ability–Revised (WJ-R). Teachers rated the children's classroom attentional and self-control behaviors on the Child Behavior Checklist (CBCL) and the Self-Control Observation Scale (SCOS). Although performance on both auditory and visual continuous performance tests (CPTs) improved with age, gender effects were small and limited to the visual CPT. Neither auditory nor visual CPT scores were related to IQ scores. However, auditory CPT scores were related to classroom behaviors as reported by teachers whereas visual CPT scores were related to visual processing.

Impaired sustained attention in euthymic bipolar disorder patients and non-affected relatives: an fMRI study

OBJECTIVE

Behavioral deficits in sustained attention have been reported during both acute and euthymic phases of type I bipolar disorder (BD-I) and also in non-affected relatives of bipolar disorder (BD) patients. In particular, selective failure in target recognition was proposed as a potential trait marker for BD, but there are few studies exploring the neural correlates. The aim of the present study was to analyze the behavioral and functional magnetic resonance imaging (fMRI) response of euthymic BD-I patients and non-affected relatives during a sustained attention task.

METHODS

Twenty-four euthymic BD-I patients, 22 non-affected first-degree relatives of BD-I subjects, and 24 matched controls underwent a continuous performance test (CPT) with two levels of difficulty during event-related fMRI scanning.

RESULTS

Both patients and relatives showed a lower accuracy in target detection when compared to controls. The fMRI data analysis revealed between-group differences in several brain regions involved in sustained attention. During error in target recognition, both patients and relatives showed a larger activation in the bilateral insula and the posterior part of the middle cingulate cortex. By contrast, during correct target response, only patients failed to activate the right insula, whereas relatives showed an increased activation of the left insula and bilateral inferior parietal lobule - limited to the higher attention load - and an augmented deactivation of the posterior cingulate/retrosplenial cortex.

CONCLUSIONS

A selective impairment in target recognition during a CPT was behaviorally and functionally detectable in both euthymic BD-I patients and non-affected first-degree relatives, suggesting that specific sustained attention deficits may be a potential trait marker for BD-I.

Modulation of attention-deficit/hyperactivity disorder symptoms by short- and long-acting methylphenidate over the course of a day

The purpose of this study was to investigate whether a long-acting methylphenidate formulation (MPH-ret) is as effective as two doses of immediate-release methylphenidate (MPH-IR) in reducing attention-deficit/hyperactivity disorder (ADHD) symptoms including inattention, impulsivity, and hyperactivity during the course of the day. Two groups of children (n=18 each) with ADHD aged between 8 and 12 years completed a continuous performance test in combination with a motion-tracking system four times a day within 8 hours. Inattention (standard deviation of reaction time), impulsivity (commission error rate), and hyperactivity (path length of the headband) were simultaneously measured. We included a control group (n=20) to rule out circadian fluctuations of attentional performance and motor activity. We observed a postlunch dip in attentional performance and an increasing trend of motor activity throughout the day whereas impulsivity remained stable in controls. The MPH-ret and MPH-IR groups had comparable treatment effects on measures of hyperactivity and inattention and normalized participant performance to control levels. In contrast, MPH-IR seems to have an advantage over MPH-ret in impulsivity treatments. Thus, our data suggest that it is crucial to assess the different domains of ADHD symptoms precisely over the course of a day to determine the optimal titration and stimulant formulation for a person with ADHD.

A Meta-Analysis of the Convergent Validity of Self-Control Measures

There is extraordinary diversity in how the construct of self-control is operationalized in research studies. We meta-analytically examined evidence of convergent validity among executive function, delay of gratification, and self- and informant-report questionnaire measures of self-control. Overall, measures demonstrated moderate convergence (r(random) = .27 [95% CI = .24, .30]; r(fixed) = .34 [.33, .35], k = 282 samples, N = 33,564 participants), although there was substantial heterogeneity in the observed correlations. Correlations within and across types of self-control measures were strongest for informant-report questionnaires and weakest for executive function tasks. Questionnaires assessing sensation seeking impulses could be distinguished from questionnaires assessing processes of impulse regulation. We conclude that self-control is a coherent but multidimensional construct best assessed using multiple methods.

Assessing inattention and impulsivity in children during the Go/NoGo task

Behavioural performance in the Go/NoGo task was compared with caregiver and teacher reports of inattention and hyperactivity-impulsivity in 1,151 children (N = 557 boys; N = 594 girls) age 9- 10-years-old. Errors of commission (NoGo errors) were significantly correlated with symptom counts of hyperactivity-impulsivity, while errors of omission (Go errors) were significantly correlated with symptom counts for inattention in both caregiver and teacher reports. Cross-correlations were also evident, however, such that errors of commission were related to inattention symptoms, and errors of omission were related to hyperactivity-impulsivity. Moreover, hyperactivity-impulsivity and inattention symptoms were highly intercorrelated in both caregiver (r = .52) and teacher reports (r = .70), while errors of commission and omission were virtually uncorrelated in the Go/NoGo task (r = .06). The results highlight the difficulty in disentangling hyperactivity-impulsivity and inattention in questionnaires, and suggest that these constructs may be more clearly distinguished in laboratory measures such as the Go/NoGo task.

Relating children's attentional capabilities to intelligence, memory, and academic achievement: a test of construct specificity in children with asthma

The relationship between attention, intelligence, memory, achievement, and behavior in a large population (N = 939) of children without neuropsychologic problems was investigated in children with mild and moderate asthma. It was hypothesized that different levels of children's attentional capabilities would be associated with different levels of intellectual, memory, and academic abilities. Children ages 6-12 at the eight clinical centers of the Childhood Asthma Management Program (CAMP) were enrolled in this study. Standardized measures of child neuropsychological and behavioral performance were administered to all participants, with analyses examining both the developmental trajectory of child attentional capabilities and the associations between Continuous Performance Test (CPT) scores and intellectual functioning, and measures of memory, academic achievement, and behavioral functioning. Findings demonstrated that correct responses on the CPT increase significantly with age, while commission errors decrease significantly with age. Performance levels on the CPT were associated with differences in child intellectual function, memory, and academic achievement. Overall these findings reveal how impairments in child attention skills were associated with normal levels of performance on measures of children's intelligence, memory, academic achievement, and behavioral functioning, suggesting that CPT performance is a salient marker of brain function.

The treatment of spasticity with Delta9-tetrahydrocannabinol in persons with spinal cord injury

STUDY DESIGN

Open label study to determine drug dose for a randomized double-blind placebo-controlled parallel study.

OBJECTIVES

To assess the efficacy and side effects of oral Delta(9)-tetrahydrocannabinol (THC) and rectal THC-hemisuccinate (THC-HS) in SCI patients.

SETTING

REHAB Basel, Switzerland.

METHOD

Twenty-five patients with SCI were included in this three-phase study with individual dose adjustment, each consisting of 6 weeks. Twenty-two participants received oral THC open label starting with a single dose of 10 mg (Phase 1, completed by 15 patients). Eight subjects received rectal THC-HS (Phase 2, completed by seven patients). In Phase 3, six patients were treated with oral THC and seven with placebo. Major outcome parameters were the spasticity sum score (SSS) using the Modified Ashworth Scale (MAS) and self-ratings of spasticity.

RESULTS

Mean daily doses were 31 mg with THC and 43 mg with THC-HS. Mean SSS for THC decreased significantly from 16.72 (+/-7.60) at baseline to 8.92 (+/-7.14) on day 43. Similar improvement was seen with THC-HS. We observed a significant improvement of SSS with active drug (P=0.001) in the seven subjects who received oral THC in Phase 1 and placebo in Phase 3. Major reasons for drop out were increase of pain and psychological side effects.

CONCLUSION

THC is an effective and safe drug in the treatment of spasticity. At least 15-20 mg per day were needed to achieve a therapeutic effect.

Measurement of attention and related functions in the preschool child

The goal of this review of the clinical and research literature is to identify, describe, and critique published methods for assessment of attention and related functions in preschool children (ages 6 and younger). The need for valid assessment of preschool children has grown dramatically in the past two decades following the implementation of special education services for infants, toddlers, and preschoolers under Public Law 99-457. At the same time, the number of preschool children presenting to clinicians for assessment of attention problems has grown at a steady rate. In contrast to assessment methods for school-age children, the availability of reliable and valid measures of attention for preschool children is much more limited. The majority of instruments developed to measure attention in preschoolers are described in the experimental literature, with fewer available commercially. Attention tests that can be appropriately used with children aged 3 and younger are scarce. Most preschool tests of attention report validity data involving sensitivity in contrasting clinical groups to controls, while the literature describing the utility of these measures in differentiating between clinical groups is much more limited. The review provides information on performance based tests (e.g., continuous performance, cancellation, auditory/visual span), as well as parent and teacher rating scales. The review concludes that valid assessment of attention and related skills can be effectively achieved in preschool children, with appropriate cautions.

Construct validity of the auditory continuous performance test for preschoolers

Development of diagnostic instruments directed toward neuropsychological assessment of preschoolers lags significantly behind those available for school-age children (DeWolfe, Byrne, & Bawden, 2000). This is particularly true for measures of executive function (EF). The Auditory Continuous Performance Test for Preschoolers (ACPT-P; Mahone, Pillion, & Hiemenz, 2001) is a computerized, Go-No-go test developed to measure selected EF skills in preschoolers. First, to determine whether performance on the ACPT-P is associated with hearing impairment, we compared performance of children with mild hearing loss (MHL) to controls on the ACPT-P, and measures of spatial working memory (SWM) and motor persistence (MP). There were no differences between performance of the MHL group and controls on any of these measures. Second, to examine the construct validity of the ACPT-P, we compared performance of 40 preschoolers with ADHD to 40 age- and sex-matched controls, using the ACPT-P to measure response preparation, sustained attention, and inhibitory control. We also compared these groups on measures of SWM and MP. The group with attention deficit hyperactivity disorder (ADHD) performed significantly worse than controls on the ACPT-P (omissions, mean response time, variability) and MP. The ACPT-P was correlated with the MP, but not with the SWM measure. Both the ACPT-P and the MP measures showed low to moderate correlations with parent ratings of behavior associated with ADHD. These findings support the use of performance-based assessment of executive control skills in preschoolers suspected of having ADHD. In this age group, the ACPT-P may be particularly useful in assessing sustained attention and response preparation and may complement behavior rating scales.

Vagal influence on working memory and attention

The aim of the present study was to investigate the effect of vagal tone on performance during executive and non-executive tasks, using a working memory and a sustained attention test. Reactivity to cognitive tasks was also investigated using heart rate (HR) and heart rate variability (HRV). Fifty-three male sailors from the Royal Norwegian Navy participated in this study. Inter-beat-intervals were recorded continuously for 5 min of baseline, followed by randomized presentation of a working memory test (WMT) based on Baddeley and Hitch's research (1974) and a continuous performance test (CPT). The session ended with a 5-min recovery period. High HRV and low HRV groups were formed based on a median split of the root mean squared successive differences during baseline. The results showed that the high HRV group showed more correct responses than the low HRV group on the WMT. Furthermore, the high HRV group showed faster mean reaction time (mRT), more correct responses and less error, than the low HRV group on the CPT. Follow-up analysis revealed that this was evident only for components of the CPT where executive functions were involved. The analyses of reactivity showed a suppression of HRV and an increase in HR during presentation of cognitive tasks compared to recovery. This was evident for both groups. The present results indicated that high HRV was associated with better performance on tasks involving executive function.

Age and task parameters in continuous performance tests for preschoolers

66 children (M=56.2 mo., SD=10.9), recruited from preschool and daycare centers, were administered two continuous performance tests, one auditory and one visual. Both tests utilized a format with one target and one nontarget. Interstimulus interval was fixed at 1350 msec. for the visual test and 5000 msec. for the auditory test. The visual test produced greater rates of omission and commission errors than the auditory test. Age was significantly related to mean reaction time and response variability for both tests; however, the visual test produced an unexpected pattern of increasing response time across age groups. On both tests omission rates improved significantly with age, while commission rates were consistent across ages 3-6 years. When considering continuous performance test paradigms for preschoolers, 3-yr.-olds may need at least a 4000-msec. interstimulus interval to make a choice for the stimulus cue. Hits following an interstimulus interval shorter than 1400 msec. may reflect younger preschoolers' response to a previous stimulus.

Event-related potentials in schizophrenic patients during a degraded stimulus version of the visual continuous performance task

Previous studies of the auditory P300 event-related potential (ERP) have reported smaller amplitudes in chronic schizophrenics but similar consistencies have not been observed with visual P300s. This study examined P300s in symptomatically stable, medicated, chronic schizophrenics (n = 14) and normal controls (n = 14) performing a visual continuous performance task utilizing degraded stimuli to burden encoding processes. Performance analysis found slower response times, fewer target detections and more false alarms in patients than in controls. Analysis of ERPs showed P300 amplitudes of schizophrenics to be significantly smaller than those of controls and, unlike controls, schizophrenics failed to exhibit significant target vs. non-target P300 amplitude differences. Discriminant analysis indicated target and non-target midline (Fz, Cz, Pz) P300 amplitudes together correctly classified all patients and controls. Exploratory topographic analysis indicated that P300 amplitudes were not asymmetrical in patients, as has been observed with auditory P300s, and, unlike the performance measures, the P300s did not correlate with the patient's positive or negative symptom ratings. The implications of these findings are described in relation to attentional disturbances and trait versus state issues in schizophrenics.

A new visual performance test offers new variables for assessing daytime vigilance: short pauses in performance

A new visual performance test, VigiMouse, was evaluated with the aid of 6 volunteering pediatry residents. The results were compared with a visual analogue scale in differentiating four different states: mild sleep deprivation, low blood alcohol level, a combination of both, and the normal state. A normal night shift at a busy pediatric ward was chosen to represent sleep deprivation. A new set of parameters based on short pauses in performance proved to be more sensitive in detecting small changes in performance than parameters based on reaction times.