Global and regional gray matter reductions in ADHD: a voxel-based morphometric study.
ABSTRACT Attention deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by inattentiveness, motor hyperactivity and impulsivity. According to neuroimaging data, the neural substrate underlying ADHD seems to involve fronto-striatal circuits and the cerebellum. However, there are important discrepancies between various studies, probably due to the use of different techniques. The aim of this study is to examine cerebral gray (GM) and white (WM) matter abnormalities in a group of ADHD children using a voxel-based morphometry protocol. The sample consisted of 25 children/adolescents with DSM-IV TR diagnosis of ADHD (medicated, aged 6-16 years) who were compared with 25 healthy volunteer children/adolescents. ADHD brains on an average showed a global volume decrease of 5.4% as compared to controls. Additionally, there were regionally specific effects in the left fronto-parietal areas (left motor, premotor and somatosensory cortex), left cingulate cortex (anterior/middle/posterior cingulate), parietal lobe (precuneus bilaterally), temporal cortices (right middle temporal gyrus, left parahippocampal gyrus), and the cerebellum (bilateral posterior). There were no differences in WM volume between ADHD children and control subjects. The results are consistent with previous studies that used different techniques, and may represent a possible neural basis for some of the motor and attentional deficits commonly found in ADHD.
SourceAvailable from: Mohammad Ali Salehinejad[Show abstract] [Hide abstract]
ABSTRACT: Background: With a life time prevalence estimated at 16%, major depression (MD) is a major public health issue. Previous studies have shown that depression has been associated with a variety of cognitive impairments. In addition to cognitive impairments, major depression is usually accompanied by alterations of cortical activity, especially in prefrontal areas. Recent studies have highlighted the importance of noninvasive brain stimulation as a means of modulating cortical excitability. Recent studies on major depression (MD) have revealed that transcranial direct current stimulation induces cortical excitability which facilitates memory and especially working memory. On the other hand visual aspects of memory in MD have not been yet investigated. Objective: This study aimed to investigate whether anodal and cathodal tDCS applied over dorsolateral prefrontal cortex (DLPFC), would significantly improve visual memory in patients with major depression. Methods: Thirty (N=30) patients with major depression were randomly assigned to receive either experimental(active) or control (sham) tDCS. The participants underwent a series of visual memory tasks before and after 10 sessions of tDCS. The parameters of active tDCS included 2 mA for 20 minutes per day for 10 consecutive days, anode over the left DLPFC (F3), cathode over the right DLPFC (F4) region. Results: After 10 sessions of anodal and cathodal tDCS, patients showed significantly improved performance in visual and spatial aspects of memory tasks. Specifically, anodal stimulation improved visual memory perfo rmance for the experimental group relative to baseline, whereas sham stimulation did not differentiate performance from baseline in the control group. Conclusion: This study showed that anodal tDCS over DLPFC concurrently with cathodal tDCS over right DLPFC improved visual and spatial aspects of memory in patients with MD. This finding is in generally consistent with previous findings about effectiveness of tDCS on cognition in major depression, while additionally provides support for effectiveness of tDCS on visual memory in MD. Keywords: Major depression, memory, tDCS, visual memoryISNR 22 nd ANNUAL CONFERENCE, SAN DIEGO, CA, USA, SAN DIEGO, CA, USA; 10/2014
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ABSTRACT: Attention-deficit hyperactivity disorder (ADHD) is a prevalent psychiatric disorder in children that often continues into adulthood. It has been suggested that motor impairments in ADHD are associated with underlying cerebellar pathology. If such is the case, individuals with ADHD should be impaired on motor tasks requiring healthy cerebellar function. To test this, we compared performance of individuals with ADHD and ADHD-like symptoms with non-ADHD controls on a visuomotor adaptation task known to be impaired following cerebellar lesions. Participants adapted reaching movements to a visual representation that was rotated by 30°. Individuals with ADHD and those with ADHD-like symptoms took longer to correct the angle of movement once the rotation was applied relative to controls. However, post-adaptation residual effect did not differ for individuals with ADHD and ADHD-like symptoms compared to the control group. These results are consistent with the hypothesis that mild cerebellar deficits are evident in the motor performance of adults with ADHD.Experimental Brain Research 01/2015; DOI:10.1007/s00221-014-4190-8 · 2.17 Impact Factor
Acta Neuropsychologica 08/2012; 10(2):163-191. DOI:10.5604/17307503.1008234