Brain - Behavior Relationships in ADHD

Using MRI to Examine Brain-Behavior Relationships in Males With Attention Deficit Disorder With Hyperactivity.

Author/s: Margaret Semrud-Clikeman
Issue: April, 2000

ABSTRACT

Objective: The relationship between neuropsychological measures of inhibition and sustained attention and structural brain differences in the regions of the caudate and the frontal region was examined in males with attention deficit disorder with hyperactivity (ADHD).

Children with ADHD were found to have reversed asymmetry of the head of the caudate, smaller volume of the left caudate head, and smaller volume of the white matter of the right frontal lobe.

Children with ADHD were found to score more poorly on measures of inhibition and sustained attention but not on measures of IQ, achievement, or motor speed.

Comparison of neuropsychological measures and brain structure measures indicated a significant relationship between reversed caudate asymmetry and measures of inhibition and externalizing behavior; i.e., children with reversed caudate asymmetry performed more poorly on measures of inhibition regardless of group membership.

Poorer performance on sustained attention tasks was related to smaller volume of the right-hemispheric white matter.

J. Am. Acad. Child Adolesc. Psychiatry, 2000, 39(4):477-484. Key Words: magnetic resonance imaging, attention-deficit hyperactivity disorder, neuropsychology, assessment.

http://www.findarticles.com/ has dozens of articles on this topic

Brain Circuit Abnormalities in ADHD

Subtle Brain Circuit Abnormalities Confirmed in ADHD

EMBARGOED FOR RELEASE: JULY 15, 1996

Subtle structural abnormalities in the brain circuit that inhibits thoughts have been confirmed in the first comprehensive brain imaging study of Attention Deficit Hyperactivity Disorder (ADHD).

Difficulty staying mentally focused is a primary symptom of ADHD, which affects about 5 percent of school age children.

Magnetic Resonance Imaging (MRI) scans of 57 boys with ADHD, aged 5-18, also revealed that their brains were more symmetrical than those of 55 age-matched controls. F. Xavier Castellanos, M.D., of the National Institute of Mental Health and colleagues report on their findings in the July issue of the Archives of General Psychiatry.

Three structures in the affected circuit on the right side of the brain -- prefrontal cortex, caudate nucleus and globus pallidus -- were smaller than normal in the boys with ADHD, when examined as a group.

The prefrontal cortex, located in the frontal lobe just behind the forehead, is believed to serve as the brain's command center. The caudate nucleus and globus pallidus, located near the middle of the brain, translate the commands into action. "If the prefrontal cortex is the steering wheel, the caudate and globus are the accelerator and brakes," explained Castellanos. "And it's this braking or inhibitory function that is likely impaired in ADHD." ADHD is thought to be rooted in an inability to inhibit thoughts. Finding smaller right hemisphere brain structures responsible for such "executive" functions strengthens support for this hypothesis.

The NIMH researchers also found that the entire right cerebral hemispheres in boys with ADHD were, on average, 5.2% smaller than those of controls.

http://www.nimh.nih.gov has dozens more studies like this.

Flaws in Some Brain Imaging Studies?

Researchers see flaws in brain-imaging studies

Insight on the News, August 19, 2003
by Kelly Patricia O'Meara

A recent review by Jonathan Leo, professor of anatomy at the Western University of Health Sciences in Pomona, Calif., and professor David Cohen of the School of Social Work at Florida International University in Miami, dispels the myth of brain imaging as a way to diagnose ADHD. And it finds that the majority of studies dating back to 1978 failed, unaccountably, to consider a major variable the use of psychotropic drugs by participants in the studies.

ED: What's interesting is that MRI, PET scans, and other imaging technologies are never used in the diagnosis of ADHD, only in research on potential causes or structural differences. So why the authors should be dispelling "the myths of brain imaging as a way to diagnose ADHD" is beyond us, since they are not used this way."

Leo and Cohen's review, entitled "Broken Brains or Flawed Studies? A Critical Review of ADHD Neuroimaging Research," was published last month in the Journal of Mind and Behavior and looked at 33 of the most recent studies using computerized topography, magnetic resonance imaging (MRI), single photon emission computerized topography or positron emission topography on ADHD-diagnosed subjects.

Although 14 scientists contributed to the study, it is generally referred to as the "Castellanos study" after the lead scientist, child psychiatrist F. Xavier Castellanos. Ten years in the making and unknown millions spent, Castellanos and his team conducted 544 MRI scans of 291 subjects 152 ADHD-diagnosed patients and 139 control subjects (normal). The Castellanos results were that "on initial scan, patients with ADHD had significantly smaller brain volumes in all regions, even after adjustment for significant covariates."

The celebrated doctor further concluded that "developmental trajectories for all structures, except caudate, remain roughly parallel for patients and controls during childhood and adolescence, suggesting that genetic and/or early environmental influences on brain development in ADHD are fixed, not progressive and unrelated to stimulant treatment." In other words, kids diagnosed with ADHD had smaller brains than those kids in the "normal" control group, and brain size isn't due to drug use.

Read this article in full...

SEE this article on a STUDY on children who NEVER used medication. It has a different conclusion than the author's study above, and was not considered by the authors above.

Frontal Lobe Differences in ADHD

Atypical Frontal Brain Activation in ADHD: Preschool and Elementary School Boys and Girls.

(Statistical Data Included)

Author/s: Lioba Baving
Issue: Nov, 1999

Attention-deficit/hyperactivity disorder (ADHD) is a common psychiatric disorder that significantly hampers psychosocial adaptation (e.g., Biederman et al., 1996; Tannock, 1998).

Several findings point to the involvement of a right-sided frontostriatal dysfunction in ADHD symptoms.

An alerting network for maintaining a vigilant state is assumed to be localized in the right frontal lobe (Posner and Petersen, 1990). This hypothesis is supported by the fact that the development of attention in normal children correlated with magnetic resonance imaging (MRI)-derived morphometric measures of the anterior cingulate, particularly the right (Casey et al., 1992).

Adults and children with focal, especially frontal, right-hemispheric lesions display behavior problems comparable with those in children with ADHD, such as inattention, defective response inhibition, and impersistence (Heilman et al., 1991).

Findings of structural neuroimaging studies underscore the assumption of a right frontal deficit in ADHD. Using MRI, abnormal - though markedly diverging - findings in several brain regions (e.g., basal ganglia, corpus callosum) were reported in children with ADHD (Filipek, 1999; Tannock, 1998), but all studies examining the frontal region found the right anterior frontal cortex to be smaller than in nonADHD children (Casey et al., 1997; Castellanos et al., 1996; Filipek et al., 1997; Hynd et al., 1990).

Casey et al. (1997) correlated performance of ADHD children and control children in 3 response inhibition tasks with MRI-based anatomical measures of the prefrontal cortex and the basal ganglia. Significant negative correlations between task performance and volume of the prefrontal cortex and caudate nuclei emerged, predominantly in the right hemisphere, suggesting that the right frontostriatal circuitry is intimately involved in response inhibition.

http://www.findarticles.com/ has dozens of articles

Neuroimaging Studies Review

Review of Neuroimaging Studies of Child and Adolescent Psychiatric Disorders From the Past 10 Years.

(Statistical Data Included)

Author/s: Robert L. Hendren
Issue: July, 2000

ABSTRACT

Objectives: To review recent neuroimaging studies of serious emotional disorders in youth and identify problems and promise of neuroimaging in clinical practice.

Method: Published reports from refereed journals are briefly described, critiqued, and synthesized into a summary of the findings to date.

Results:

• Childhood-onset schizophrenia shows progressive ventricular enlargement, reduction in total brain and thalamus volume, changes in temporal lobe structures, and reductions in frontal metabolism.
• Autistic disorder is associated with cerebellar changes, greater total brain and lateral ventricle volume, and asymmetry.
• The prefrontal cortex and the basal ganglia are consistently reported as abnormal in attention-deficit/hyperactivity disorder.
• Patients with anorexia nervosa show enlarged CSF spaces and reductions in gray and white matter that are only partially reversible with weight recovery.

Conclusions: Results from neuroimaging studies of childhood-onset psychiatric disorders suggest consistency in the structures found to be abnormal, but inconsistencies in the nature of these abnormalities. Although neuroimaging technology holds great promise for neurodevelopmental research, it is not yet a diagnostic instrument.

J. Am. Acad. Child Adolesc. Psychiatry 2000, 39(7):815-828.

Premature Birth and ADHD

Premature Or Low Birthweight Babies At Significantly Increased Risk Of Hyperactivity Disorder

Premature or low birthweight babies are up to three times as likely to become hyperactive, with low attention spans, suggests research published ahead of print in the Archives of Disease in Childhood.

The Danish research team compared the birth records of 834 children with confirmed HKD with those of 20,100 children with no mental disorders. All the children were born between 1980 and 1994.

Children born at between 34 and 36 weeks were around 70% more likely to develop the disorder than children born at term. Babies at born below 34 completed weeks were almost three times as likely to develop the disorder.

Low birthweight babies born at term were also at risk, the study showed.

Note: This story has been adapted from a news release issued by BMJ Specialty Journals.