A. Catherine King

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.

Positron emission tomography in schizophrenic patients with and without neuroleptic medication

Positron emission tomography using [18F]2-fluoro-2-deoxy-d-glucose was performed in nine chronic schizophrenic patients both when medication-free and when medicated with neuroleptics. Total brain cortex, temporal cortex, and basal ganglia glucose use was significantly increased with medication; however, there was no change in anterior/posterior metabolic gradients.

Dysfunction in a prefrontal substrate of sustained attention in schizophrenia

Regional brain metabolism was measured in normal subjects and patients with schizophrenia while they performed an auditory discrimination task designed to emphasize sustained attention. A direct relationship was found in the normal subjects between metabolic rate in the middle prefrontal cortex and accuracy of performance. The metabolic rate in the middle prefrontal cortex of patients with schizophrenia, even those who performed as well as normals, was found to be significantly lower than normal and unrelated to performance. The findings point to a role of the mid-prefrontal region in sustained attention and to dysfunction of this region in schizophrenia.

Increased temporal lobe glucose use in chronic schizophrenic patients.

Temporal lobe glucose metabolic rate was assessed in 21 off-medication patients with schizophrenia and 19 normal controls by positron emission tomography with 18F-deoxyglucose. Patients with schizophrenia had significantly greater metabolic activity in the left than the right anterior temporal lobe, and the extent of this lateralization was in proportion to the severity of psychopathology.

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 typeractivity 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 flurodeoxyglucose-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.

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.

Plasma catecholamines and their metabolites in obsessive-compulsive disorder

Plasma catecholamines and their metabolites were sampled in 13 medication-free patients with obsessive-compulsive disorder (OCD) and 29 normal controls. In addition to severe OCD symptoms, the patients had significantly higher anxiety, tension, and resting pulse rates than the controls. Nonetheless, mean plasma concentrations of norepinephrine (NE) and epinephrine (E), the catecholamine metabolites 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA), and the stress-related hormone cortisol did not differ between OCD patients and normal controls. When the patients and control populations were combined and average plasma NE and E levels calculated over 35 min, subjects with a higher mean NE output (greater than 1.1 pm/ml) had higher Profile of Mood States depression scores than subjects with a low NE output (less than 1.1 pm/ml). Altogether, these results indicate that elevated plasma catecholamine measures are not likely to be associated with the pathophysiology of OCD.