Hemispheric lateralization of cognitive functions in children with centrotemporal spikes

We assessed the impact of unilateral epileptic foci in benign idiopathic partial epilepsy of childhood with rolandic discharges (BECT) on performance and hemispheric specialization in lateralized cognitive functions. Six children with BECT with a left-sided focus (BECT-L), 6 children with BECT with a right-sided focus (BECT-R), and 12 control children were tested in verbal, visual-spatial, and visual-attention tasks, with visual hemifield presentation. Children with BECT-R were impaired in the visual-spatial task relative to those with BECT-L, and the typical left-hemisphere (LH) advantage was not reported in the verbal task in children with BECT-L. Additionally, the classic global superiority effect was lacking in children with BECT-R, which may be due to impaired performance of the right hemisphere specialized in global (vs local)-level processing. These data argue for the deleterious effect of epileptic discharges per se on cognitive functions in the developing brain, and the decisive role of epileptic focus lateralization in specific cognitive impairments and hemispheric specialization.     

Association between frequency of nocturnal epilepsy and language disturbance in children

In clinical practice, an association is commonly suggested between nocturnal epileptiform activity and language disorders in children. However, this association has not been studied systematically. This study explored the correlation between daily and nocturnal epileptiform discharges ratio, frequency of nocturnal epileptiform discharges, and severity of nocturnal seizures in correlation with the severity of language impairment. A total of 326 children referred to an epilepsy center were included. All children had a 24-hour electroencephalogram (EEG), a neuropsychologic assessment, and a reconfirmed diagnosis of epilepsy. The balance between verbal and performance IQ scores of the Wechsler Intelligence Scale for Children was a focus of the study. A significant correlation between the severity of nocturnal seizures and lower verbal IQ scores compared to performance IQ scores was found (P < 0.05). There was a clinically relevant difference between performance IQ and verbal IQ between the groups of children with only nocturnal epileptiform EEG discharges and only epileptiform EEG discharges during wake (P = 0.033). Children with nocturnal epileptiform EEG discharges have lower verbal than performance IQs when compared to children with only epileptiform EEG discharges during wake. Although a causal relationship is unclear, this indicates an association between the occurrence of nocturnal epileptiform EEG discharges and language disturbance.     

Interactions of epileptiform EEG discharges and cognition

Interactions of subclinical epileptiform EEG discharges and cognitive functioning were studied in 91 patients with epilepsy, under video monitoring, to exclude overt clinical ictal phenomena during the investigations. A short-term memory test was presented as an engaging television game, in two versions, using spatial, or verbal material. Transitory cognitive impairment (TCI) was demonstrated during EEG discharges, either generalised or focal, in half the patients. Right-sided discharges were associated with impairment of the spatial task and left-sided with errors on the verbal version. TCI was demonstrable only when the discharge occurred during presentation of the material to be recalled. Increasing task difficulty, up to the patients' limit of performance, was associated with increasing susceptibility to TCI. Sixteen patients showed a significant effect of task on discharge rate, but in some this increased during the stimulus and in others while responding. There are thus complex interactions of epileptiform EEG activity on cognitive function and vice versa.     

Psychological effects of subclinical epileptiform EEG discharges in children. II. General intelligence tests

Twenty-one children with suspected or proven epilepsy and subclinical epileptiform EEG discharges in the waking state were studied. The EEG was telemetered and behaviour recorded by closed-circuit television during performance of a general intelligence test (RAKIT, shortened version) which comprised 6 subtests. Mean total IQ was below that of control populations and the subtests profile was abnormal, due particularly to impaired performance on a subtest concerned with verbal short-term memory. This effect was accounted for by that subgroup of children who exhibited discharges during the test; those who did not show discharges at that time were unimpaired. Performance of 3 of the subtests was impaired when discharges occurred during presentation of the test item or between presentation and response. The findings suggest that cognitive impairment found in people with epilepsy may not only represent a more or less static disability, due to drugs, cerebral pathology, etc., but may in part be an intermittent process related to the occurrence of subclinical epileptiform discharges. These preliminary findings need to be amplified but have implications both for interpretation of neuropsychological studies in persons with epilepsy and also for the drug treatment of those who continue to exhibit subclinical EEG discharges when overt seizures have been controlled.     

The effects of pediatric traumatic brain injury on verbal and visual-spatial working memory

The purpose of this study was to investigate the effects of pediatric traumatic brain injury (TBI) on verbal and visual-spatial working memory (WM). WM tasks examined memory span through recall of the last item of a series of stimuli. Additionally, both verbal and visual-spatial tests had a dual-task condition assessing the effect of increasing demands on the central executive (CE). Inhibitory control processes in verbal WM were examined through intrusion errors. The TBI group (n = 73) performed more poorly on verbal and visual-spatial WM tasks than orthopedic-injured children (n = 30) and non-injured children (n = 40). All groups performed more poorly on the dual-task conditions, reflecting an effect of increasing CE load. This effect was not greater for the TBI group. There were no group differences in intrusion errors on the verbal WM task, suggesting that problems in WM experienced by children with TBI were not primarily due to difficulties in inhibitory control. Finally, injury-related characteristics, namely days to follow commands, accounted for significant variance in WM performance, after controlling for relevant demographic variables. Findings suggest that WM impairments in TBI are general rather than modality-specific and that severity indices measured over time are better predictors of WM performance than those taken at a single time point.     

Psychological effects of subclinical epileptiform EEG discharges. I. Scholastic skills

The possible effects of subclinical epileptiform EEG discharges on educational skills have been studied. Twenty children with proven or suspected epilepsy and known subclinical EEG discharges underwent telemetric EEG and video monitoring during standard tasks of reading, mental arithmetic and manual dexterity, and at rest. The discharge rate was significantly lower at rest than during execution of a task. For both reading and arithmetic, the discharge rate was higher when the child was presented with material appropriate to his own level of ability than when easier or more difficult material was given. High discharge rates were associated with low test performance particularly for arithmetic. Reading speed was significantly increased during the discharges, but overall reading efficiency was significantly reduced with respect to the non-discharge condition. The decrement of reading efficiency was greater for longer than for shorter discharges. The findings confirm that otherwise subclinical EEG discharges may be accompanied by momentary impairment of scholastic skills. The interaction between discharges and cognitive function is, however, complex and the nature and level of difficulty of the task in turn affects the rate of EEG discharge.     

Arousal, performance and absence seizures in rats.

Rats of the WAG/Rij strain show bilateral symmetrical spontaneous spike-wave discharges in the EEG, with clinical concomitants. The present experiment investigated whether, during a learning task, the number of discharges would be diminished compared to a period of rest. Additionally, it was investigated whether behavioural differences would be noticed within the task in trials with and without spike-wave discharges. The length of the post reinforcement pause in a fixed interval task was used as a performance index. Eleven rats were extensively trained to press a lever for food in a fixed (60 sec) interval task until a stable response pattern emerged: a post-reinforcement pause of about half the interval. Next, EEG electrodes were implanted and baseline EEGs were made, before and after the first and fifth test sessions. In addition, the behavior of the animals in the task was monitored when an EEG was recorded. During the task, a significantly smaller number of spike-wave discharges was found, compared to the preceding and succeeding baseline hours. This reduction is probably related to a higher level of vigilance during the task compared to the rest hour. Furthermore, the post-reinforcement pause was significantly enhanced in trials with spike-wave discharges compared to trials without discharges, indicating a clear change in performance. Both results are in agreement with what could be expected in patients with absence epilepsy and provide further evidence for the validation of the spike-wave discharges as genuine epileptic phenomena.     

Recognition Impairment Correlated with Short Bisynchronous Epileptic Discharges

The occurrence of transitory cognitive impairment during diffuse subclinical electroencephalographic (EEG) discharges has been widely documented but the role of the parameters influencing the cognitive performance and the involvement of motor or verbal response in the tasks used is still under debate. Fifteen patients suffering from primary generalized epilepsy with frequent bisynchronous EEG epileptic bursts underwent a shape recognition task during EEG monitoring. The test sequence was as follows: memorandum, pause, and multiple choice set. After pressing the response button, the patient was asked to confirm the choice verbally. The following parameters were considered: geometrical complexity of the shape, chronological position of the burst occurring during the single test, and the duration of discharge ranging from 1 to 3 s. Results showed a significant increase in incorrect responses during the test when discharges occurred, with more errors occurring for difficult than for easy shapes. Neither the discharge position nor the duration of the epileptic burst influenced the performance. Diffuse epileptic activity of short duration produced selective effects on the cognitive process regardless of the motor component of the response.     

Behavioral activation of human hippocampal EEG: Relationship to recent memory

Behaviorally activated EEG was recorded from each hippocampus in 17 epilepsy surgery patients with unilateral (11 left, 6 right) mesial temporal lobe (MTL) seizure onset and correlated with preoperative material-specific memory test performances. Whole-band power (1–30 Hz) was recorded and subjected to spectral analysis under three conditions: (a) eyes closed resting, (b) eyes open with a verbal task, and (c) eyes open with a nonverbal task. Significantly less EEG desynchronization was observed in the epileptogenic hippocampus during the verbal activation condition but not during the eyes-open nonverbal task. Decreased EEG reactivity in the left hippocampus during verbal activation was correlated significantly with verbal memory test impairment among patients with left MTL seizure onset. However, similar relationships were not obtained between right seizure focus patients and performance on a visuospatial learning test. Results confirm the association of left MTL structures with verbal memory functions and emphasize the difficulty in demonstrating a consistent relationship between right MTL structures and visuospatial memory performance.     

RISK OF RECURRENCE AFTER A SINGLE, UNPROVOKED, GENERALIZED TONO- CLONIC SEIZURE

A cohort of 119 two- to 16-year-old patients was followed to assess the risk of recurrence after a single, unprovoked, generalized tonic-clonic seizure. Only children with a normal neurological examination and intellectual development, and an EEG showing no focal abnormality, were studied. The risk of recurrence at six months was 22 per cent, at one year 28.5 per cent, at three years 32.6 per cent and at eight years 37.7 per cent. 58 per cent of recurrences occurred within the first six months and 87 per cent within the first two years. Initial EEGs showing generalized, unprovoked spikes and waves, generalized paroxysmal discharges precipitated by intermittent photic stimulation, or isolated slowing, were associated with risks of recurrence at two years of 40, 50 and 26 per cent, respectively. These results do not differ significantly from those obtained when the initial EEG was normal (29 per cent). Age, seizure duration and history of epilepsy in the family were not associated with a significantly higher risk of recurrence. The risk of recurrence was similar for treated and untreated patients.     

Working-memory training improves developmental dyslexia in Chinese children

Although plasticity in the neural system underlies working memory, and working memory can be improved by training, there is thus far no evidence that children with developmental dyslexia can benefit from working-memory training. In the present study, thirty dyslexic children aged 8-11 years were recruited from an elementary school in Wuhan, China. They received working-memory training, including training in visuospatial memory, verbal memory, and central executive tasks. The difficulty of the tasks was adjusted based on the performance of each subject, and the training sessions lasted 40 minutes per day, for 5 weeks. The results showed that working-memory training significantly enhanced performance on the nontrained working memory tasks such as the visuospatial, the verbal domains, and central executive tasks in children with developmental dyslexia. More importantly, the visual rhyming task and reading fluency task were also significantly improved by training. Progress on working memory measures was related to changes in reading skills. These experimental findings indicate that working memory is a pivotal factor in reading development among children with developmental dyslexia, and interventions to improve working memory may help dyslexic children to become more proficient in reading.     

A novel multidomain computerized cognitive assessment for attention-deficit hyperactivity disorder: evidence for widespread and circumscribed cognitive deficits

Multidomain assessment may enhance the diagnosis of cognitive impairment in children with attention-deficit hyperactivity disorder (ADHD). A set of novel Web-enabled computerized tests has recently been shown to be valid for identifying mild cognitive impairment and characterizing the cognitive profile associated with various disorders. It was anticipated that these tests would be well suited for use in children with ADHD. The authors tested this idea in a pilot study of 15 children (12 males, 3 females; mean age, 11 years 10 months; range, 9-15 years) with ADHD and 15 age-, education-, and gender-matched controls. The profile of cognitive impairment in ADHD children off methylphenidate across 6 cognitive domains (memory, executive function, visual-spatial skills, verbal function, attention, and motor skills) was described relative to controls. The effect of treatment with methylphenidate was examined by comparing the ADHD children on methylphenidate and on placebo (administered in a double-blind randomized fashion) relative to controls and by comparing the ADHD children on methylphenidate relative to placebo. Significant impairment in ADHD was evident in memory, visual-spatial, verbal, and attention domains, and near-significant impairment was observed in executive function and motor skills. On methylphenidate but not placebo, performance was comparable to controls in immediate verbal memory, psychomotor accuracy, visual-spatial, verbal rhyming, and overall battery performance. Significant improvement with administration of methylphenidate relative to placebo was evident for psychomotor accuracy, verbal rhyming, and overall battery performance. Hence, on the limited basis of this pilot study, the set of computerized tests studied appears to be useful for measuring cognitive function in ADHD; however, additional studies are needed to confirm this.     

Prevalence of epileptiform discharges in healthy 11- and 12-year-old children

We sought to determine the prevalence of interictal epileptiform discharges (IEDs) in healthy 11- and 12-year-old children. Sixth grade students with no history of seizure, or neurologic or psychiatric disease, were enrolled in a longitudinal physical activity intervention study. Per study protocol, each student had two EEG recordings approximately 6 months apart. Epileptiform discharges were present in 4 (2.9%) of 140 students: centrotemporal in three and generalized in one. In three children, the discharges were still present six months later. None of the children had developed seizures a minimum of one year after the second EEG. These results are consistent with those of two landmark European studies performed nearly a half century ago, before the modern era of digital EEG. Healthy 11- and 12-year-old children with no history of seizure may have centrotemporal or generalized epileptiform discharges on EEG, which can persist for at least 6 months. Based on both our results and those of the two prior European studies, such discharges, if found incidentally in otherwise healthy children in this age group, should not prompt further evaluation or treatment.     

Working memory impairments in children with attention-deficit hyperactivity disorder with and without comorbid language learning disorders

Our objectives were to examine whether children with attention-deficit hyperactivity disorder (ADHD) are impaired on one or more components of working memory (WM) independent of comorbid language learning disorders, and whether WM impairments are more strongly related to symptoms of inattention than to symptoms of hyperactivity-impulsivity. Four groups of children participated: ADHD (n = 62); ADHD+RD/LI (n = 32); RD/LI (n = 15); and a typically developing comparison group (n = 34). Four simple and brief measures of WM were used that varied in modality (auditory-verbal; visual-spatial) and processing demands (temporary storage versus manipulation of information). Children with ADHD without comorbid language learning disorders exhibited deficits in visual-spatial storage and verbal and visual-spatial central executive (C.E.) functions that were independent of comorbid psychiatric disorders. Children with language learning disorders, regardless of comorbidity with ADHD, exhibited impairments in both verbal and spatial storage as well as C.E. domains of WM. Symptoms of inattention, but not symptoms of hyperactivity/impulsivity, predicted performance on verbal and visual-spatial C.E. measures independent of age, verbal cognitive ability, and reading and language performance. Findings are consistent with data implicating neuropsychological impairments in ADHD. The dimensional results are also consistent with prior research demonstrating the neuropsychological impairments are more strongly associated with the inattention symptom dimension than with the hyperactive-impulsive dimension.     

Effects of gender and alcoholism on verbal and visual-spatial learning

Sex differences in cognitive abilities of chronic alcoholics were investigated using a paired-associates learning test with separate but similarly structured verbal and visual-spatial components. Four groups of 35 subjects each, equated for age and education, were tested: male and female alcoholics, and male and female community control subjects. As expected, sex differences were found on the component tasks: overall, nonalcoholic women performed significantly better than nonalcoholic men on the verbal measure, and nonalcoholic men performed better than nonalcoholic women on the visual-spatial measure. Nonalcoholic men had a larger discrepancy between component scores than nonalcoholic women, suggesting greater lateralization of cognitive functions; however, this difference did not reach significance. The effects of alcoholism were different for the sexes. Alcoholic women were not impaired on either the verbal or visual-spatial measure, but the alcoholic men demonstrated deficits in visual-spatial performance. In addition, they showed less difference between verbal and visual-spatial component scores than the other groups, suggesting that alcoholism attenuated the effects of hemispheric specialization for cognitive abilities normally found in men.     

Neuropsychological Assessment of Cognitive Functioning in Children with Epilepsy

Summary: The variety of cognitive dysfunctions related to learning disabilities in children with epilepsy have been studied by linking electroencephalogram (EEG) and computerized neuropsychological testing. This showed that "subclinical" discharges impaired performance in 61% of the patients on a simple and a choice reaction time test, although some discharges lasted 1 s only. Neuropsychological investigation of subclinical EEG discharges may help to determine their adverse effect on learning.     

Mental object rotation in Parkinson's disease.

Deficits in visual-spatial ability can be associated with Parkinson's disease (PD), and there are several possible reasons for these deficits. Dysfunction in frontal-striatal and/or frontal-parietal systems, associated with dopamine deficiency, might disrupt cognitive processes either supporting (e.g., working memory) or subserving visual-spatial computations. The goal of this study was to assess visual-spatial orientation ability in individuals with PD using the Mental Rotations Test (MRT), along with other measures of cognitive function. Non-demented men with PD were significantly less accurate on this test than matched control men. In contrast, women with PD performed similarly to matched control women, but both groups of women did not perform much better than chance. Further, mental rotation accuracy in men correlated with their executive skills involving mental processing and psychomotor speed. In women with PD, however, mental rotation accuracy correlated negatively with verbal memory, indicating that higher mental rotation performance was associated with lower ability in verbal memory. These results indicate that PD is associated with visual-spatial orientation deficits in men. Women with PD and control women both performed poorly on the MRT, possibly reflecting a floor effect. Although men and women with PD appear to engage different cognitive processes in this task, the reason for the sex difference remains to be elucidated.     

Hemiparetic forms of cerebral palsy in relation to epilepsy and mental retardation

Fifty-one children with hemiparetic cerebral palsy underwent clinical, EEG and CT examinations to assess mental performance, laterality of CP and incidence of epilepsy, 80 per cent of the children had epileptic abnormalities on EEG, but less than half had clinical signs of epilepsy. Clinical paroxysms were more frequent in those with right-sided hemiparesis. Focal or epileptic EEG changes were usual in those with right-hemisphere involvement, but unless clinical paroxysms developed, these had no bearing on mental performance. Lower IQ was found in the patients with clinical epilepsy--in nearly all cases with left-sided hemiparesis and in half of those with right-sided hemiparesis.     

Variables Related to Differences in Standardized Test Outcomes for Children with Autism

The purpose of this experiment was to assess whether manipulation of variables related to motivation and attention in children with autism would influence performance on standardized tests. Two different testing conditions were compared: One consisted of the usual standardized testing procedures; during the other, specific variables that were hypothesized to relate to each child's responsiveness to task stimuli were manipulated. Data were collected in the context of a repeated reversals experimental design with condition order varied within and across children. Six children participated in a total of 44 separate testing sessions, controlled for order of conditions, number of sessions, and type of test. Results showed consistent differences between the two conditions, suggesting that improving motivation and attention in children with autism may considerably influence test performance and interpretation. Findings are discussed in relation to the difficulty in administering and interpreting changes in performance on standardized tests with this population.     

Beneficial effects of antiepileptic medication on absence seizures and cognitive functioning in children

In this prospective clinical study, the effects on cognitive functioning of absence seizures, epileptiform EEG discharges, and their abolishment by antiepileptic medication were evaluated in patients newly diagnosed with childhood absence epilepsy or juvenile absence epilepsy. Eleven children in the study group and ten age- and gender-matched controls with mild asthma underwent combined video/EEG and neurocognitive assessment (IQ, fine-motor fluency, attention, visual and spatial memory). The neuropsychological assessment was repeated after the introduction of antiepileptic medication. Ten children with absence epilepsy became clinically seizure free. The study group improved in attention, fine-motor fluency, and visual memory. The controls improved only in fine-motor and attention skills. Duration of generalized 3-Hz spike-wave discharges and clinical absence seizures was negatively correlated with performance on the visual memory task. Cessation of seizures induced by antiepileptic medication may support neurocognitive functioning in children.