Striatal dopamine release in reading and writing measured with [123I]iodobenzamide and single photon emission computed tomography in right handed human subjects

Videogames and Young People with Developmental Disorders

Young people with developmental disorders experience difficulties with many cognitive and perceptual tasks, and often suffer social impairments. Yet, like typical youth, many appear to enjoy playing videogames. This review considers the appeal of videogames to individuals with autism spectrum disorders, attention deficit hyperactivity disorder, and specific language impairment. It examines how they respond to the various challenges that play entails with particular reference to sensory, cognitive, and social dimensions. It is argued that research into how these young people engage voluntarily with this dynamic and challenging medium offers great potential to extend our empirical and theoretical understanding of the disorders. Many gaps in our current knowledge are identified and several additional themes for possible future research are proposed.

The dopaminergic basis of human behaviors: A review of molecular imaging studies

This systematic review describes human molecular imaging studies which have investigated alterations in extracellular DA levels during performance of behavioral tasks. Whilst heterogeneity in experimental methods limits meta-analysis, we describe the advantages and limitations of different methodological approaches. Interpretation of experimental results may be limited by regional cerebral blood flow (rCBF) changes, head movement and choice of control conditions. We revisit our original study of striatal DA release during video-game playing [Koepp, M.J., Gunn, R.N., Lawrence, A.D., Cunningham, V.J., Dagher, A., Jones, T., Brooks, D.J., Bench, C.J., Grasby, P.M., 1998. Evidence for striatal dopamine release during a video game. Nature 393, 266-268] to illustrate the potentially confounding influences of head movement and alterations in rCBF. Changes in [(11)C]raclopride binding may be detected in extrastriatal as well as striatal brain regions-however we review evidence which suggests that extrastriatal changes may not be clearly interpreted in terms of DA release. Whilst several investigations have detected increases in striatal extracellular DA concentrations during task components such as motor learning and execution, reward-related processes, stress and cognitive performance, the presence of potentially biasing factors should be carefully considered (and, where possible, accounted for) when designing and interpreting future studies.

Imaging the dopamine system with in vivo [11C]raclopride displacement studies: understanding the true mechanism

Measuring changes in dopamine (DA) levels in humans using radioligand-displacement studies and positron emission tomography (PET) has provided important empirical findings in diseases and normal neurophysiology. These studies are based on the assumption that DA exerts a competitive inhibition on D(2)-radioligand binding. However, the transfer of this hypothesis to a proven mechanism has not been fully achieved yet and an accumulating number of studies challenge it. In addition, new evidence suggests that DA exerts a noncompetitive inhibition on D(2)-radioligand binding under amphetamine conditions. This article reviews the theoretical basis for the DA competition hypothesis, the in vivo and in vitro evidences supporting a noncompetitive action of DA on D(2)-radioligand binding under amphetamine conditions, and discusses possible mechanisms underlying this noncompetitive interaction. Finally, we propose that such noncompetitive interactions may have important implications for how one interprets findings obtained from radioligand-displacement PET studies in neuropsychiatric diseases, especially in schizophrenia in which a dysregulation of the DA-promoted internalization of D(2) receptors was recently suggested.

Magnetic resonance imaging study of brain asymmetries in dyslexic patients

Research studies suggest that the left hemisphere is involved in the pathophysiology of dyslexia. Thus far, the exact location and nature of the purported lesion(s) remain a matter of contention. The present study describes the distribution of structural abnormalities as related to brain symmetry in the brains of dyslexic individuals. High-resolution three-dimensional magnetic resonance images (MRIs) were analyzed in 16 dyslexic men and 14 controls matched for sex, age, educational level, and handedness. A computerized image analysis system was used to assess the volumetric deformations required to match each brain with its left-right mirror image. The results showed significant abnormalities in five left hemisphere structures involving the extrapyramidal and limbic systems: amygdala, hippocampus proper, parahippocampal gyrus, putamen, and globus pallidus. The left hemisphere is thought to play a major role in the temporal analysis of information. This stream of temporal analysis is of importance in motor movements. Reading might have evolved as an exaptation to motor movements requiring the sequential analysis of information.

Oscillatory local field potentials recorded from the subthalamic nucleus of the alert rat

Hitherto, high-frequency local field potential oscillations in the upper gamma frequency band (40-80 Hz) have been recorded only from the region of subthalamic nucleus (STN) in parkinsonian patients treated with levodopa. Here we show that local field potentials recorded from the STN in the healthy alert rat also have a spectral peak in the upper gamma band (mean 53 Hz, range 46-70 Hz). The power of this high-frequency oscillatory activity was increased by 30 +/- 4% (+/-SEM) during motor activity compared to periods of alert immobility. It was also increased by 86 +/- 36% by systemic injection of the D2 dopamine receptor agonist quinpirole. The similarities between the high-frequency activities in the STN of the healthy rat and in the levodopa-treated parkinsonian human argue that this oscillatory activity may be physiological in nature and not a consequence of the parkinsonian state.