Rates of cerebral protein synthesis in primary visual cortex during sleep-dependent memory consolidation, a study in human subjects

If protein synthesis during sleep is required for sleep-dependent memory consolidation, we might expect rates of cerebral protein synthesis (rCPS) to increase during sleep in the local brain circuits that support performance on a particular task following training on that task. To measure circuit-specific brain protein synthesis during a daytime nap opportunity, we used the L-[1-(11)C]leucine positron emission tomography (PET) method with simultaneous polysomnography. We trained subjects on the visual texture discrimination task (TDT). This was followed by a nap opportunity during the PET scan, and we retested them later in the day after the scan. The TDT is considered retinotopically specific, so we hypothesized that higher rCPS in primary visual cortex would be observed in the trained hemisphere compared to the untrained hemisphere in subjects who were randomized to a sleep condition. Our results indicate that the changes in rCPS in primary visual cortex depended on whether subjects were in the wakefulness or sleep condition but were independent of the side of the visual field trained. That is, only in the subjects randomized to sleep, rCPS in the right primary visual cortex was higher than the left regardless of side trained. Other brain regions examined were not so affected. In the subjects who slept, performance on the TDT improved similarly regardless of the side trained. Results indicate a regionally selective and sleep-dependent effect that occurs with improved performance on the TDT.

A PILOT STUDY ON THE ENCODING OF A PERCEPTUAL LEARNING TASK FOLLOWING SLEEP DEPRIVATION

Memory encoding sometimes must occur during a period of sleep deprivation. The question was whether one night of sleep deprivation inhibits encoding on a perceptual learning task (the texture discrimination task). The sample was 18 human participants (M age=22.1 yr., SEM=0.5; 8 men). The participants were randomized to a sleep deprivation or sleep control condition and, after the manipulation, were given two administrations of the texture discrimination task. All participants were given an opportunity for a 90 min. nap between the two administrations. Performance was measured by the interpolated stimulus-to-mask-onset asynchrony (i.e., the inter-stimulus interval), at which the percentage of correct responses for the stimuli in the participant's peripheral vision fell below 80%. Offline consolidation was defined as a decrease in this index between the two administrations. Participants who were sleep deprived prior to encoding exhibited similar offline consolidation (M=-5.3 msec., SEM=2.3) compared to participants who were not sleep deprived prior to encoding (M=-6.2 msec., SEM=3.9); the two-way interaction between time and condition was not significant. In light of reports in the literature, these results indicate encoding following sleep deprivation may be influenced by both the type of task encoded and the brain regions involved in memory processing.

Psychiatric aspects of child and adolescent obesity: a review of the past 10 years

OBJECTIVE

To review the past 10 years of published research on psychiatric aspects of child and adolescent obesity and highlight information mental health professionals need for preventing obesity in youths and diagnosing and treating it.

METHOD

Researchers performed computerized and manual searches of the literature and summarized the most relevant articles.

RESULTS

The growing epidemic of child and adolescent obesity deserves attention for its immediate mental health and long-term medical complications. Mental health professionals working with obese youths should be aware of recent advances in neuroscience, genetics, and etiologies associated with obesity. Those who assess and treat obese youth should view obesity as a chronic disease. Currently, no approved pharmacological or surgical approaches exist to treat childhood obesity.

CONCLUSIONS

Health care providers should focus on modest weight-loss goals that correlate with significant health benefits. The most effective treatments include substantial parental involvement. Mental health professionals should help obese children build self-esteem to help them lead full lives regardless of weight.

Suicide in teenagers: assessment, management, and prevention

Adolescents who kill themselves invariably have an underlying psychiatric disorder. Biological markers are not yet clinically useful for identifying adolescents at risk, and there is a paucity of research data on the effectiveness of behavioral intervention for suicidal teenagers. A case of a 16-year-old scholar and athlete is presented to illustrate how multiple risk factors and a family diathesis often go undetected, resulting in tragic consequences. Psychiatric, familial, genetic, and social risk factors of adolescent suicide are reviewed, and the efficacy of lithium and antidepressant pharmacotherapy in reducing suicide rates is discussed. The importance of screening adolescent patients for depression is emphasized. Although teenage suicide is rare and hard to predict, identifying and treating adolescents at risk is essential to further reduce teenage suicide.

Aggression and psychiatric comorbidity in children with hypothalamic hamartomas and their unaffected siblings

OBJECTIVE

To assess aggression and psychiatric comorbidity in a sample of children with hypothalamic hamartomas and gelastic seizures and to assess psychiatric diagnoses in siblings of study subjects.

METHOD

Children with a clinical history of gelastic seizures and hypothalamic hamartomas (n = 12; age range 3-14 years) had diagnoses confirmed by video-EEG and head magnetic resonance imaging. Structured interviews were administered, including the Diagnostic Interview for Children and Adolescents-Revised Parent Form (DICA-R-P), the Test of Broad Cognitive Abilities, and the Vitiello Aggression Scale. Parents were interviewed with the DICA-R-P about each subject and a sibling closest in age without seizures and hypothalamic hamartomas. Patients were seen from 1998 to 2000.

RESULTS

Children with gelastic seizures and hypothalamic hamartomas displayed a statistically significant increase in comorbid psychiatric conditions, including oppositional defiant disorder (83.3%) and attention-deficit/hyperactivity disorder (75%). They also exhibited high rates of conduct disorder (33.3%), speech retardation/learning impairment (33.3%), and anxiety and mood disorders (16.7%). Significant rates of aggression were noted, with 58% of the seizure patients meeting criteria for the affective subtype of aggression and 30.5% having the predatory aggression subtype. Affective aggression was significantly more common (p < .05). Unaffected siblings demonstrated low rates of psychiatric pathology on semistructured parental interview and no aggression as measured by the Vitiello Aggression Scale.

CONCLUSIONS

Children with hypothalamic hamartomas and gelastic seizures had high rates of psychiatric comorbidity and aggression. Parents reported that healthy siblings had very low rates of psychiatric pathology and aggression.

Case study: sexual hyperactivity treated with psychostimulants in familial male precocious puberty

Familial male precocious puberty is a form of precocious puberty resulting from an activating mutation of the luteinizing hormone receptor. Behavior problems are associated with the early onset of puberty. In this case, sexual hyperactivity was treated with psychostimulants. Implications for the effectiveness of methylphenidate in reducing sexual hyperactivity with and without familial male precocious puberty are discussed, and testable hypotheses are proposed for the effects of stimulants on sexual behavior in adolescents.

Follow-up of radial arterial catheterization for positron emission tomography studies

Radial arterial catheterization is needed for repeated arterial blood samples to construct tracer input curves of positron emission tomography (PET) scans (Herscovitch [1993]: Rheum Dis Clin North Am 19:765-794). Complications resulting from such short-term catheterizations are rare. Sixteen investigators followed 106 subjects who had arterial lines placed in the context of a PET study. Abnormalities were reported in 8 of 106 (7.5%) cases. Of these eight cases, three (37.5%) were inpatients diagnosed with anorexia nervosa, a condition that may represent a risk factor. All abnormalities were benign, did not affect motor function, and did not require medical intervention.

Adrenergic and noradrenergic plasma levels in Lesch-Nyhan disease

Noradrenergic dysfunction and abnormality in monoamine oxidase (MAO) enzyme activity have been reported previously in Lesch-Nyhan (LN) disease. This study examines peripheral indices of adrenergic, noradrenergic, and MAO function in children and young adults with LN disease (n = 11), and healthy subjects (n = 9). Blood samples, collected in identical conditions prior to a positron emission tomography (PET) study, were assayed for concentrations of epinephrine (EPI), norepinephrine (NE), and 3-methoxy-4-hydroxyphenylglycol (DHPG) (which results from the degradation of NE by monoamine oxidase type A [MAO-A]). The LN subjects had significantly higher EPI levels by 245% (p < .00) and lower DHPG levels by 42% (p < .00) compared to the control group. No group differences were noted in NE plasma levels. Cognitive function (IQ tested by Stanford Binet Intelligence Scale) was associated with EPI in the LN group (r = 0.77, p = .009), but not in the control group. The abnormally high EPI plasma concentrations may indicate another biochemical dysfunction secondary to the absence of the HPRT enzyme in LN patients. Such a biochemical deficit is likely to originate from the adrenal medulla, which is the primary site of EPI synthesis. The adrenal medulla may be directly affected by the absence of hypoxanthine guanine phosphoribosyl transferase (HPRT) enzyme, or may receive inappropriately high descending activation input from the brain. The abnormally low DHPG levels, in the context of normal NE levels, indicates low MAO activity, either as a primary deficit, or as secondary adaptive changes to spare NE levels that would otherwise be too low for adequate noradrenergic function.

High midbrain [18F]DOPA accumulation in children with attention deficit hyperactivity disorder

OBJECTIVE

Attention deficit hyperactivity disorder (ADHD) is a highly prevalent childhood psychiatric disorder characterized by impaired attention, excessive motor activity, and impulsivity. Despite extensive investigation of the neuropathophysiology of ADHD by a wide array of methodologies, the neurobiochemical substrate of this disorder is still unknown. Converging evidence, however, suggests a primary role of the dopaminergic system.

METHOD

This study examined the integrity of presynaptic dopaminergic function in children with ADHD through use of positron emission tomography and the tracer [18F]fluorodopa ([18F]DOPA). Accumulation of [18F]DOPA in synaptic terminals, a measure of dopa decarboxylase activity, was quantified in regions rich in dopaminergic innervation, including caudate nucleus, putamen, frontal cortex, and midbrain (i.e., substantia nigra and ventral tegmentum).

RESULTS

Accumulation of [18F]DOPA in the right midbrain was higher by 48% in 10 children with ADHD than in 10 normal children. Despite its magnitude, this difference would not have reached statistical significance if corrected by the Bonferroni test for multiple comparisons. However, [18F]DOPA in the right midbrain was correlated with symptom severity. No other dopamine-rich regions significantly differed between groups.

CONCLUSIONS

These findings are suggestive of dopaminergic dysfunction at the level of the dopaminergic nuclei in children with ADHD. Abnormality in dopa decarboxylase activity may be primary or secondary to deficits in other functional units of the dopamine pathway (e.g., receptor, uptake transporter, vesicular transporter, degradation enzymes). Efforts toward defining the origin of this abnormality should help delineate mechanisms of midbrain control of attention and motor behavior important for the understanding of the causes and treatment of ADHD.

High presynaptic dopaminergic activity in children with Tourette's disorder

OBJECTIVE

Tourette's disorder is characterized by chronic fluctuating motor and vocal tics. Despite extensive investigation of the neuropathophysiology of the disorder by a wide array of methodologies, its neurobiochemical substrate is still unclear. Converging evidence, however, suggests a primary role of the dopaminergic system, particularly within the basal ganglia.

METHOD

This study examined the integrity of presynaptic dopaminergic function in children with Tourette's disorder, using positron emission tomography and the tracer [18F]fluorodopa (FDOPA). Accumulation of FDOPA in synaptic terminals, a measure of DOPA decarboxylase activity, was quantified in caudate nucleus, putamen, frontal cortex, and midbrain (i.e., substantia nigra and ventral tegmentum).

RESULTS

Subjects with Tourette's disorder showed higher FDOPA accumulation than controls in the left caudate nucleus (by 25%; p = .03) and right midbrain (by 53%; p = .08).

CONCLUSION

These findings provide evidence of dopaminergic dysfunction in children with Tourette's disorder which affects both cell nuclei and nerve terminals. Based on the known regulation of DOPA decarboxylase activity by post- and presynaptic receptors, and by extracellular dopamine concentration, abnormal activity in this enzyme may reflect deficits in a variety of functional elements of the dopamine system. The precise mechanism underlying an up-regulation of DOPA decarboxylase activity needs to be identified in future studies.

DOPA decarboxylase activity in attention deficit hyperactivity disorder adults. A [fluorine-18]fluorodopa positron emission tomographic study

Converging evidence implicates the dopaminergic system and the prefrontal and nigrostriatal regions in the pathophysiology of attention deficit hyperactivity disorder (ADHD). Using positron emission tomography (PET) with [fluorine-18]fluorodopa (F18-DOPA), we compared the integrity of the presynaptic dopaminergic function between 17 ADHD adults and 23 healthy controls. The ratio of the isotope concentration of specific regions to that of nonspecific regions reflects DOPA decarboxylase activity and dopamine storage processes. Of three composite regions (prefrontal cortex, striatum, and midbrain), only the prefrontal cortex showed significantly different F18-DOPA ratios in ADHD as compared with control adults (p < 0.01). The medial and left prefrontal areas were the most altered (lower F18-DOPA ratios by 52 and 51% in ADHD as compared with controls). Similarly, the interaction [sex x diagnosis] was significant only in the prefrontal cortex (p < 0.02): lower ratios in men than in women in ADHD and vice versa in controls. These findings suggest that a prefrontal dopaminergic dysfunction mediates ADHD symptoms in adults and that gender influences this abnormality. On the basis of previous neuroimaging findings in ADHD showing discrepant findings in adults and adolescents and on evidence for midbrain dopaminergic defect in adolescents, we hypothesize that the prefrontal dopaminergic abnormality in ADHD adults is secondary and results from an interaction of the primary subcortical dopaminergic deficit with processes of neural maturation and neural adaptation.

The neurobiology of attention-deficit/hyperactivity disorder

We provide a comprehensive review of the neurobiological basis of attention-deficit/hyperactivity disorder. This summary was accomplished by a review of research in three areas: neuroimaging, genetics, and neurochemistry. Additionally, we also discuss a newer conceptualization of the disorder. Although none of the current findings present a unified picture of the pathophysiology of the disorder, the vast array of studies reviewed do highlight CNS abnormalities that, when taken together, present a convincing argument that the cause clearly resides within the realm of developing brain.

Age-related changes in brain glucose metabolism in adults with attention-deficit/hyperactivity disorder and control subjects

Using positron emission tomography and [18F]-2-fluoro-2-deoxy-D-glucose, the authors determined cerebral metabolic rates for glucose (CMRglc) in 39 adults (18-51 years old) with attention-deficit/hyperactivity disorder (ADHD) and 56 healthy control adults (19-56 years old) during the performance of a continuous attention task. Increased age was associated with reduced global CMRglc in ADHD women, but not in ADHD men, control men, or control women. Better performance on the attention task was significantly associated with increased age only in the ADHD female group. Determining the role of behavioral, hormonal, and genetic factors is a challenge for future research.

Laboratory and diagnostic testing in child and adolescent psychiatry: a review of the past 10 years

OBJECTIVE

To review in a critical fashion the literature of the past decade covering diagnostic and laboratory testing in the field of child and adolescent psychiatry.

METHOD

A computerized search of articles published during the past decade was made, and selected articles are presented. Because of the paucity of articles specifically relating to minors, selected articles from adult psychiatry are cited.

RESULTS

With a few notable exceptions, few controlled studies on the specificity and sensitivity of any laboratory test for any specific disorder of behavior presenting in children have been conducted in children and adolescents. A high index of suspicion will remain the clinician's best ally in utilizing laboratory measures in the assessment of psychopathology. Nonetheless, studies have appeared that will guide the clinician as to what tests are not clinically useful.

CONCLUSION

Indications and the lack of indications for specific laboratory studies are an integral part of the knowledge base that child psychiatrists must have. Much more empirical data will need to be collected prospectively to inform the field and to move the judicious use of the laboratory from an art to a science.

Health hazards of radiation exposure in the context of brain imaging research: special consideration for children

This review provides information on health and biological effects of low-dose radiation to help institutional review boards and investigators make educated assessments of the risks of low-level radiation exposure involved in research, particularly in children.

METHODS

Studies of low-level radiation exposure with large sample sizes and long follow-up were reviewed. To help interpret the studies, we clarified the measures and measurement strategies of radiation exposure and of health risks. The few large studies of risks of low-level radiation in children have failed to detect an increased incidence of cancer. Most studies of low-level radiation involve adults.

RESULTS

The risk of increased rates of cancer after low-level radiation exposure is not supported by population studies of health hazards from exposure to background radiation, radon in homes, radiation in the workplace or radiotherapy. Compared to the frequency of daily spontaneous genetic mutations, the biological effect of low-level radiation at the cellular level seems extremely low. Furthermore, the potentiation of cellular repair mechanisms by low-level radiation may result in a protective effect from subsequent high-level radiation. Studies approved by institutional review boards in the U.S. that involve the exposure of healthy normal children to ionizing radiation were reviewed.

CONCLUSION

Health risks from low-level radiation could not be detected above the "noise" of adverse events of everyday life. In addition, no data were found that demonstrated higher risks with younger age at low-level radiation exposure.

Intravenous dextroamphetamine and brain glucose metabolism

This study reports the effects of intravenous dextroamphetamine on cerebral glucose metabolism assayed by positron emission tomography (PET) and [fluorine-18]fluorodeoxyglucose (FDG) in 13 healthy adults during the performance of a continuous visual attention task. Two FDG PET scans were performed within a single experimental session. The first scan was preceded by the injection of placebo and the second scan by the injection of 0.15 mg/kg dextroamphetamine. Global and normalized regional glucose metabolic rates (rCMRglc) were examined as a function of pharmacological challenge and subjective experience. Subcortical, limbic, frontal, and cerebellar rCMRglc significantly increased after dextroamphetamine, whereas rCMRglc of the temporal cortex significantly decreased. Physiological and self-report measures of subjective states showed the expected alterations. These rCMRglc changes reflect both the direct pharmacological effect of dextroamphetamine on monoaminergic neurotransmitter systems as well as enhancement of the activation of the neural network mediating the performance of the continuous attention task.

Cerebral glucose metabolism in childhood onset schizophrenia

Decreased frontal cortical glucose metabolism has been demonstrated in adult schizophrenics both at rest and while engaging in tasks that normally increase frontal metabolism, such as the Continuous Performance Test (CPT). The authors tested the hypothesis that adolescents with childhood onset schizophrenia would also demonstrate hypofrontality while performing the CPT. Cerebral glucose metabolism was examined in 16 adolescents (mean age 14.1 +/- 1.7) with onset of schizophrenia by age 12 (mean age at onset 9.9 +/- 1.8) and 26 healthy adolescents selected to be similar in age, sex and handedness using positron emission tomography and 18F-fluorodeoxyglucose. Patients with childhood onset schizophrenia made fewer correct and more incorrect identifications on the CPT. Region of interest analysis revealed no significant group differences in global cerebral glucose metabolism, but increased metabolic rate in supramarginal gyrus (F = 6.74, P < 0.05) and inferior frontal gyrus/insula (F = 7.09, P < 0.05) and decreased metabolic rate in middle frontal gyrus (F = 6.72, P < 0.05) and superior frontal gyrus (t = 2.04, P < 0.05) in schizophrenics. Comparison of effect sizes with an identically designed study of adult schizophrenics did not indicate more severe hypofrontality in childhood onset schizophrenia. Pixel-based analyses indicated a more complex pattern of group differences in cerebral metabolism with bilaterally increased cerebellar metabolic rate in childhood onset schizophrenics. These findings suggest that childhood onset schizophrenia may be associated with a similar, but not more severe, degree of hypofrontality relative to that seen in adult onset schizophrenia.

Cerebral glucose metabolism in adolescent girls with attention-deficit/hyperactivity disorder

OBJECTIVE

Low cerebral metabolic rates for glucose (CMRglc) have been reported in a small sample of girls with attention-deficit/hyperactivity disorder (ADHD). This study was an effort to replicate this finding in a larger independent sample.

METHOD

Using positron emission tomography and [18F]fluorodeoxyglucose, CMRglc were compared between 10 girls with ADHD (14.10 +/- 1.91 years) and 11 normal girls (14.3 +/- 1.70 years).

RESULTS

Global CMRglc was similar between ADHD and control girls. Lateralization of normalized CMRglc differed significantly between ADHD and control girls in parietal and subcortical regions, with rCMRglc lower on the left than on the right side in girls with ADHD, and conversely in control girls. The sylvian area of the parietal region and the anterior putamen of the subcortical region were the main contributors to this effect. Normalized rCMRglc of the hippocampus was higher in ADHD than in control girls. Sexual maturation was the only clinical characteristic that differed between present and previous samples, and it correlated with global CMRglc.

CONCLUSIONS

Although failing to confirm abnormally low CMRglc in girls with ADHD, this study suggested that (1) functional interactions between sex and brain development may contribute to ADHD pathophysiology, and (2) sexual maturation should be controlled in future CMRglc studies of adolescent girls.

Selegiline in ADHD adults: plasma monoamines and monoamine metabolites

Plasma monoamines and monoamine metabolites were assessed before and during selegiline treatment in adults with attention deficit/hyperactivity disorder (ADHD). Selegiline, at low dose, is a selective monoamine oxidase inhibitor type B (MAOI-B). After 2-week placebo baseline, 36 ADHD adults were randomized to 6-week placebo or 20 mg/day or 60 mg/day selegiline, followed by 2-week posttreatment placebo. Twenty-seven subjects continued into a 6-week 20-mg/day or 60-mg/day selegiline period. Behavioral variables included self-rated scores on the Conners' Abbreviated Teacher Rating Scale (Conners-ATRS) and performance on a Continuous Performance Task (CPT). Plasma samples were assayed for amines (dopamine, norepinephrine, epinephrine), precursor (DOPA), and metabolites (HVA, DOPAC, DHPG, normetanephrine, metanephrine, 5-HIAA). Selegiline produced dose-dependent changes in monoamine metabolites and DOPA plasma levels. Dopaminergic indices were associated with ADHD symptom severity (Conners-ATRS) and noradrenergic indices with CPT performance. Serotonergic metabolism, challenged by selegiline, correlated with clinical changes. These findings support a multisystem dysfunction underlying ADHD pathophysiology.

Gender differences in brain metabolic and plasma catecholamine responses to alpha 2-adrenoceptor blockade

alpha 2-Adrenergic receptors modulate the release of several neurotransmitters implicated in the treatment and pathophysiology of mood and anxiety disorders. Significant sex differences occur in the prevalence of both disorders. To test whether gender affects alpha 2 function, the plasma catecholamine and brain metabolic responses to alpha 2 blockade were measured in male and female volunteers. Ten female and thirteen male volunteers underwent [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) scans before and after infusion of idazoxan (200 micrograms/kg). Measures of plasma catecholamines, blood pressure, and anxiety were obtained. Norepinephrine responses were larger in males. Women showed global increases in metabolism, whereas males had no global changes and some regional decreases in FDG uptake following idazoxan administration. The differences in norepinephrine increases are consistent with previously reported effects of gender on sympathetic activation. The PET data suggest gender differences in responses to alpha 2-receptor blockade in brain as well.

Cerebral glucose metabolism during pharmacologic studies: test-retest under placebo conditions

The reliability of serial [18F]fluorodeoxyglucose (FDG) PET scans for psychopharmacologic studies was tested by using placebo infusions.

METHODS

FDG scans were obtained before and after a 30 min placebo infusion (n = 10; Group 1) or after each of two bolus infusions with placebo (n = 8; Group 2). Subjects performed a continuous performance task (CPT) during each scan. Cardiovascular measures and ratings of anxiety were obtained in all subjects. Samples for determination of plasma norepinephrine (NE) were taken at multiple time points in Group 1.

RESULTS

A slight increase in apparent global metabolism occurred between scans in both Groups 1 and 2. A few regions significantly increased in both groups. While an apparent increase in sympathetic activity occurred during the placebo infusion, neither NE levels, anxiety ratings nor cardiovascular measures correlated with global or regional FD6 uptake.

CONCLUSION

Test-retest differences of global and regional glucose metabolism were highly consistent across two experimental designs. While increases in cerebral glucose metabolism appeared to occur during the second scan, differences between scans were small. This method may offer advantages for selected psychopharmacologic studies.

Presynaptic dopaminergic deficits in Lesch-Nyhan disease

BACKGROUND

Lesch-Nyhan disease is a rare, devastating, X-linked recessive disorder of purine synthesis. Patients present with hyperuricemia, choreoathetosis, dystonia, and aggressive and self-injurious behavior. Although the genetic and biochemical abnormalities have been identified, the causes of the neuropsychiatric syndrome remain unclear.

METHODS

We used positron-emission tomography to measure presynaptic accumulation of fluorodopa F 18 tracer in the dopaminergic regions of the brains of 12 patients with Lesch-Nyhan disease (age, 10 to 20 years) and 15 healthy controls (age, 12 to 23). The results were expressed as ratios of specific to nonspecific radioactive counts. A low ratio indicates decreased dopa decarboxylase activity and dopamine storage.

RESULTS

The fluorodopa F 18 ratio was significantly lower in the putamen (31 percent of control values), caudate nucleus (39 percent), frontal cortex (44 percent), and ventral tegmental complex (substantia nigra and ventral tegmentum; 57 percent) in the patients with Lesch-Nyhan disease than in the controls. Uptake of the tracer was abnormally low even in the youngest patients tested, and there was no overlap in the values between patients and controls.

CONCLUSIONS

Patients with Lesch-Nyhan disease have abnormally few dopaminergic nerve terminals and cell bodies. The abnormality involves all dopaminergic pathways and is not restricted to the basal ganglia. These dopaminergic deficits are pervasive and appear to be developmental in origin, which suggests that they contribute to the characteristic neuropsychiatric manifestations of the disease.

Abnormalities in sustained attention and anterior cingulate metabolism in subjects with resistance to thyroid hormone

Attention deficit disorders are a frequent manifestation of resistance to thyroid hormone (RTH), a disorder caused by mutations in the hormone-binding domain of the human thyroid hormone receptor beta gene. Positron emission tomography was used to measure cerebral glucose metabolism in regions known to be biological determinants of sustained attention in 13 adult RTH and 13 unaffected subjects. Compared to the control group, performance on a continuous auditory discrimination task was severely impaired in the RTH subjects, while metabolism was higher both in the right parietal cortex and the anterior cingulate gyrus. Abnormally high functional activity of the anterior cingulate during sustained attention may be associated with a decreased signal-to-noise ratio for the neural processing of task stimuli in subjects with RTH.

Regional brain glucose metabolism after acute alpha 2-blockade by idazoxan

BACKGROUND

Several classes of antidepressant drugs act on alpha 2-adrenergic receptors. Studies of patients with disorders responsive to treatment with these drugs report group differences in ex vivo measures of alpha 2-binding and in vivo responses mediated by alpha 2-receptors. Measurement of regional brain metabolic response to an alpha 2-antagonist may be a useful method for further definition of the role alpha 2-receptor regulation plays in the treatment of neuropsychiatric disorders.

METHODS

Regional brain glucose metabolism was measured before and after infusion with 200 micrograms/kg idazoxan with use of 18F-fluoro-2-deoxyglucose positron emission tomography in 13 healthy men. Arterial drug concentration, behavioral responses, and cardiovascular responses were also measured.

RESULTS

The absolute and normalized glucose metabolic rate significantly increased in primary visual cortex. Significant increases and decreases occurred in normalized metabolic rates in prefrontal cortical regions. Measurement of metabolic effects occurred during the peak cardiovascular response.

CONCLUSIONS

Our findings are consistent with regionally specific effects of alpha 2-blockade. This method may be useful for the study of alpha 2-receptor function in humans.

Regional cerebral glucose metabolism in autopsy-confirmed Creutzfeldt-Jakob disease

Regional cerebral glucose metabolism was measured in a 72-year-old man, with Creutzfeldt-Jakob disease (CJD), by positron emission tomography using [18F]-2-fluoro-2-deoxy-D-glucose as the tracer. The diagnosis of CJD, a rare neurodegenerative disorder, was confirmed at autopsy 13 months later. Compared with five unaffected elderly men, the patient had reduced metabolism heterogeneously distributed throughout the brain. The hypometabolism was most evident in the right hemisphere, particularly in the posterior frontal, parietal, Sylvian, and temporal regions. This left-right asymmetry is more extensive than that previously reported in Alzheimer's disease, and may provide a useful metabolic marker for early diagnosis of CJD.

Right frontotemporal activation by tonal memory in dyslexia, an O15 PET Study

A prior study documented the failure of dyslexic men to activate left temporoparietal cortex during phonologic processing. Because of reports of an anomalous right planum temporale in developmental dyslexia, the functional implications of which are unknown, this study examined the ability of dyslexics to activate right temporal cortex. Regional cerebral blood flow was measured in 15 right-handed dyslexic men during rest and during a tonal memory task expected to activate right-sided cortex in controls. A matched control sample (n = 18) showed significant activation of several right frontotemporal regions as well as of left temporal cortex. In contrast, severely dyslexic men activated fewer right frontotemporal regions, while making many more errors than controls, but showed normal activation of left mid to anterior temporal cortex. These results support hypothesized underlying deficits in rapid temporal processing and possible involvement of right (in addition to left) temporal cortex in severe dyslexia.

Reduced brain metabolism in hyperactive girls

OBJECTIVE

This study assesses the effect of attention-deficit hyperactivity disorder (ADHD) and gender on cerebral glucose metabolism (CMRglu), using positron emission tomography and 18F-fluorodeoxyglucose.

METHOD

Nineteen normal (6 females; 14.3 +/- 1.3 years old) and 20 ADHD adolescents (5 females; 14.7 +/- 1.6 years old) participated in the study. An auditory continuous performance task was used during the 30-minute uptake of 18F-fluorodeoxyglucose.

RESULTS

There were no statistically significant differences in global or regional CMRglu between ADHD (N = 20) and normal (N = 19) adolescents. However, the global CMRglu in ADHD girls (N = 5) was 15.0% lower than in normal girls (N = 6) (p = .04), while global CMRglu in ADHD boys was not different than in normal boys. Furthermore, global CMRglu in ADHD girls was 19.6% lower than in ADHD boys (p = .02) and was not different between normal girls and normal boys. Clinical rating scales did not differentiate ADHD girls from ADHD boys, nor normal girls from normal boys.

CONCLUSIONS

The greater brain metabolism abnormalities in females than males strongly stress that more attention be given to the study of girls with ADHD.

A double FDG/PET study of the effects of scopolamine in older adults

Two consecutive positron emission scans were done in one session using a double injection method of [18F]2-fluoro-2-deoxyglucose administration to examine the effects of the antimuscarinic drug scopolamine on cerebral glucose metabolism in ten older adults. Scopolamine causes temporary memory impairment, and its effects have been used to model aspects of the cognitive impairment that occur in Alzheimer's disease (AD). Cortical metabolic rates of patients with AD have been reported to be depressed, especially in parietal, temporal, and frontal association areas. After scopolamine administration to the elderly volunteers, absolute and normalized glucose metabolic rates were depressed in prefrontal and occipital regions and increased in parietal-occipital cortical regions and a left middle temporal region. These changes in the older volunteers are generally not consistent with changes seen in AD. We conclude that deficits in muscarinic system function may contribute to some but not all of the hypometabolic changes seen in AD patients.

Cerebral glucose metabolism in adults with attention deficit hyperactivity disorder after chronic stimulant treatment

OBJECTIVE

The authors examined the effects of chronic stimulant treatment on cerebral glucose metabolism in adults diagnosed with attention deficit hyperactivity disorder (ADHD), who were studied by means of positron emission tomography (PET) with [18F]fluorodeoxyglucose as the tracer.

METHOD

Each subject received two PET scans, the first before drug treatment and the second after treatment with daily oral doses, individually titrated for clinical effect, of either methylphenidate (N = 19) or d-amphetamine (N = 18) for a minimum of 6 weeks. The subjects completed behavioral self-report measures before and at the end of the medication period.

RESULTS

Neither stimulant medication changed global, or whole-brain, metabolism, although both drugs increased systolic blood pressure. Metabolism in only two of the 60 brain regions sampled was changed by methylphenidate, while d-amphetamine exhibited no effect on regional metabolism. Both drugs were associated with significant improvement in behavior, as evidenced by improved ratings for restlessness and ability to maintain attention.

CONCLUSIONS

While the present study does not demonstrate any robust metabolic effects of chronic stimulant treatment, the behavioral data strongly indicate that methylphenidate and d-amphetamine are effective agents for the treatment of adults with ADHD.

Gender-related differences in regional cerebral glucose metabolism in normal volunteers

Positron emission tomography studies have correlated changes in the cerebral metabolic rate of glucose utilization (CMRglu) with symptoms of depression, aggression, impulsivity, and hyperactivity. Psychiatric disorders in which these symptoms are manifested are disproportionately represented among the sexes. We evaluated gender differences in regional CMRglu in control subjects (21 men and 18 women) with particular interest in the global, orbital frontal, and left anterolateral prefrontal cortical (LAPFC) CMRglu. A trend was present for global CMRglu to be greater in women than in men. Regional CMRglu was lower in men than in women in the orbital frontal area. No differences were observed in the LAPFC region.

Normal activation of frontotemporal language cortex in dyslexia, as measured with oxygen 15 positron emission tomography

OBJECTIVE

To assess the ability of dyslexic men to activate left middle to anterior language cortex normally.

DESIGN

Positron emission tomography using oxygen 15-labeled water as a tracer during rest and during a syntax task involving sentence comprehension.

SETTING

Research hospital.

PATIENTS OR OTHER PARTICIPANTS

Fifteen right-handed, severely dyslexic men (mean [+/- SD] age, 27 +/- 5 years) and 20 matched controls.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

Cerebral blood flow.

RESULTS

During rest, dyslexics showed reduced blood flow (relative to controls) in one left parietal region near the angular/supramarginal gyri, but otherwise normal flow. During syntactic processing, dyslexics and controls showed similar, significant activation of left middle to anterior temporal and inferior frontal cortex.

CONCLUSIONS

These results, together with the previously reported failure of dyslexics to activate left temporoparietal cortex during phonologic processing, argue for dysfunction of left cortical language areas restricted to posterior language regions in dyslexia.

Effects of acute stimulant medication on cerebral metabolism in adults with hyperactivity

Recent work in our laboratory has demonstrated both global and regional reductions in cerebral glucose metabolism in adult subjects with attention-deficit hyperactivity disorder (ADHD). The purpose of the present study was to examine the effects of an acute dose of stimulant medication on cerebral metabolism in adults with ADHD using positron emission tomography with fluorodeoxyglucose-18 as the tracer. Each subject underwent scanning twice, once off-drug and again after receiving a single oral dose of either dextroamphetamine (0.25 mg/kg) or methylphenidate (0.35 mg/kg). Subjects completed behavioral self-report measures before and after the scan and performed an auditory continuous performance task during the tracer uptake period. Neither drug changed global metabolism. Both drugs increased systolic blood pressure, and dextroamphetamine improved performance on the auditory attention task. Each stimulant produced a differential pattern of increases and decreases in regional metabolism throughout the regions of interest that were sampled. Rather than increasing glucose utilization in specific brain regions with lowered metabolic rates in adults with ADHD, stimulants may act by altering glucose use throughout the brain.

Brain metabolism in teenagers with attention-deficit hyperactivity disorder

OBJECTIVES

We sought to obtain and compare values of cerebral glucose metabolism in normal minors and minors with Attention Deficit Hyperactivity Disorder (ADHD). We also sought to confirm our earlier findings of reduced brain metabolism in adults with ADHD, and to examine whether these results might be diagnostically useful.

DESIGN

Case-control study.

SETTING

Adolescents were recruited to National Institutes of Health Clinical Center/Research Facility through advertisement at local high schools and ADHD organizations.

PATIENTS

Subjects were 10 normal adolescents and 10 adolescents with ADHD diagnosed with structured interviews using DSM-III-R criteria.

MAIN OUTCOME MEASURES

Positron emission tomography and fludeoxyglucose F18 were used to study cerebral glucose metabolism in minors while they performed an auditory-attention task.

RESULTS

Global or absolute measures of metabolism did not statistically differ between groups, although hyperactive girls had a 17.6% lower absolute brain metabolism than normal girls. As compared with the values for the controls, normalized glucose metabolism was significantly reduced in six of 60 specific regions of the brain, including an area of the left anterior frontal lobe (P < .05). Lower metabolism in that specific region of the left anterior frontal lobe was significantly inversely correlated with measures of symptom severity (P < .001-.009, r = -.56 to -.67).

CONCLUSIONS

Global or absolute measures of metabolism using positron emission tomography and fludeoxyglucose F18 did not statistically differentiate between normal adolescents with ADHD. Positron emission tomography scans can be performed and are well tolerated by normal teenagers and teenagers with ADHD. The feasibility of normal minors participating in research involving radiation was established.

Attention deficit-hyperactivity disorder in people with generalized resistance to thyroid hormone

BACKGROUND

Attention deficit-hyperactivity disorder is a well-recognized psychiatric disorder of childhood. Its cause is unknown, but there is evidence of a familial predisposition. Symptoms suggestive of this disorder have been reported in subjects with generalized resistance to thyroid hormone, a disease caused by mutations in the thyroid receptor-beta gene and characterized by reduced responsiveness of peripheral and pituitary tissues to the actions of thyroid hormone. We systematically evaluated the presence and severity of attention deficit-hyperactivity disorder in 18 families with a history of generalized resistance to thyroid hormone.

METHODS

We studied 49 affected and 55 unaffected family members; 52 were adults, and 52 were children. All subjects were evaluated with structured psychiatric questionnaires by interviewers who were unaware of the medical diagnosis. The number of symptoms of attention deficit-hyperactivity disorder was calculated for each subject.

RESULTS

Among the adults, 11 of 22 subjects with generalized resistance to thyroid hormone (50 percent) and 2 of 30 unaffected subjects (7 percent) had met the criteria for attention deficit-hyperactivity disorder as children (P < 0.001). Among the children, 19 of 27 subjects resistant to thyroid hormone (70 percent) and 5 of 25 unaffected subjects (20 percent) met the criteria for the disorder (P < 0.001). The odds of having attention deficit-hyperactivity disorder were 3.2 times higher for affected male subjects than for affected female subjects and were 2.7 times higher for unaffected male subjects than for unaffected female subjects. The mean symptom score was 2.5 times higher in the affected group than in the unaffected group (7.0 vs. 2.8, P < 0.001). The frequency of other psychiatric diagnoses was similar in the two groups.

CONCLUSIONS

In our study sample, attention deficit-hyperactivity disorder is strongly associated with generalized resistance to thyroid hormone.

Regional cerebral glucose metabolism in bulimia nervosa

OBJECTIVE

The authors' purpose in this study was to further delineate the character of cerebral metabolism in bulimia nervosa and to determine if functional links could be made between regional cerebral metabolism and the symptoms of depression, obsessive-compulsive disorder, and bulimia nervosa.

METHOD

Regional cerebral glucose metabolism was measured by using positron emission tomography in 11 inpatients with bulimia nervosa and 18 normal comparison subjects matched in sex (all were women), age, and educational level. The bulimic patients were also tested for symptoms of major depression and obsessive-compulsive disorder.

RESULTS

The patients with bulimia showed a correlation between lower left anterolateral prefrontal regional cerebral glucose metabolism and greater depressive symptoms. However, the orbitofrontal regional cerebral glucose metabolism of patients with bulimia was not greater than that of comparison subjects, nor was higher orbitofrontal metabolism correlated with greater obsessive-compulsive disorder symptoms.

CONCLUSIONS

These findings lead to the conclusion that left anterior lateral prefrontal cortex hypometabolism varies with the depressive symptoms observed in bulimia but that temporal lobe hypermetabolism and asymmetries appear to be independent of the mood state.

Failure to activate the left temporoparietal cortex in dyslexia. An oxygen 15 positron emission tomographic study

To test the hypothesis of left temporoparietal dysfunction in dyslexia, suggested by neuropsychological and neuropathologic data, cerebral blood flow was measured with positron emission tomography in 14 right-handed men with severe developmental dyslexia (mean [SD] age, 27 [5] years; median reading level, fifth grade) and 14 matched controls at rest and during an auditory phonologic task (rhyme detection) and an auditory attention task involving the detection of target tones. As expected, normal readers activated left temporoparietal cortex during rhyme detection but not during the nonphonologic attentional task. Dyslexic men failed to activate those left temporoparietal regions activated in controls during rhyme detection but did not differ from controls in these regions during rest or attentional testing. Thus, the expected left temporoparietal dysfunction was demonstrated only when specific probes for these regions were employed.

Cerebral glucose metabolism in adults with hyperactivity of childhood onset

BACKGROUND AND METHODS

The cause of childhood hyperactivity (attention deficit-hyperactivity disorder) is unknown. We investigated the hypothesis that cerebral glucose metabolism might differ between normal adults (controls) and adults with histories of hyperactivity in childhood who continued to have symptoms. Each patient was also the biologic parent of a hyperactive child. None of the adults had ever been treated with stimulant medication. To measure cerebral glucose metabolism, we administered 148 to 185 MBq (4 to 5 mCi) of [18F]fluoro-2-deoxy-D-glucose intravenously to 50 normal adults and 25 hyperactive adults while they performed an auditory-attention task. Images were obtained for 30 minutes with a Scanditronix positron-emission tomograph with a resolution of 5 to 6 mm. Whole-brain and regional rates of glucose metabolism were measured with computer assistance by two trained research assistants, working independently, who were blinded to the subjects' status (control or hyperactive).

RESULTS

Global cerebral glucose metabolism was 8.1 percent lower in the adults with hyperactivity than in the normal controls (mean +/- SD, 9.05 +/- 1.20 mg per minute per 100 g vs. 9.85 +/- 1.68 mg per minute per 100 g; P = 0.034). In the adults with hyperactivity, glucose metabolism was significantly reduced, as compared with the values for the controls, in 30 of 60 specific regions of the brain (P less than 0.05). Among the regions of the brain with the greatest reductions in glucose metabolism were the premotor cortex and the superior prefrontal cortex. When the seven women with hyperactivity or the six patients with learning disabilities were omitted from the analysis, the results were similar.

CONCLUSIONS

Glucose metabolism, both global and regional, was reduced in adults who had been hyperactive since childhood. The largest reductions were in the premotor cortex and the superior prefrontal cortex--areas earlier shown to be involved in the control of attention and motor activity.

The neuropharmacology of attention-deficit hyperactivity disorder

Attention-deficit hyperactivity disorder, as described in the American Psychiatric Association's diagnostic manual DSM III-R (1), is a broadly defined syndrome of cognitive and behavioral problems that were originally found in children, but that have been increasingly identified in adults who had similar complaints in childhood (2). This paper briefly reviews the definition and treatment of this syndrome in children, evidence for specific neurochemical abnormalities, and effects of stimulants on neurochemistry. Finally, problems of diagnosis and treatment in adults are discussed.

The effect of methylphenidate on urinary catecholamine excretion in hyperactivity: a partial replication

Children with attention deficit disorder with hyperactivity were treated with methylphenidate HCl (0.74 +/- 0.2 mg/kg/day) for 2 weeks in an open trial to assess changes in the urinary excretion of catecholamines and behavior. The purpose of this study was to confirm earlier work that methylphenidate has a distinctly different effect on urinary 3-methoxy-4-hydroxyphenylglycol (MHPG) excretion as compared to earlier studies with dextroamphetamine. Results confirmed the earlier finding that methylphenidate does not significantly change urinary MHPG excretion. No significant relationship was found between behavioral change and any of the urinary catecholamines or metabolites measured.