ADHD Research Today is a free monthly online journal that collates and summarizes the latest research about ADHD, including details on attention-deficit hyperactivity disorder, drugs, treatment, symptoms.

Top down attentional deficits in macaques with lesions of lateral prefrontal cortex.

Rossi AF, Bichot NP, Desimone R, Ungerleider LG

Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA. andrew.rossi@vanderbilt.edu

Brain imaging, electrical stimulation, and neurophysiological studies have all implicated the prefrontal cortex (PFC) in the top-down control of attention. Specifically, feedback from PFC has been proposed to bias activity in visual cortex in favor of attended stimuli over irrelevant distracters. To identify which attentional functions are critically dependent on PFC, we removed PFC unilaterally in combination with transection of the corpus callosum and anterior commissure in two macaques. In such a preparation, the ipsilesional hemisphere is deprived of top-down feedback from PFC to visual cortex, and the contralesional hemisphere can serve as an intact normal control. Monkeys were trained to fixate a central cue and discriminate the orientation of a colored target grating presented among colored distracter gratings in either the hemifield affected by the PFC lesion or the normal control hemifield. Locations of the targets and distracters were varied, and the color of the central cue specified the color of the target on each trial. The behavioral response was a bar release, and thus attentional impairments could be distinguished from impaired oculomotor control. When the cue was held constant for many trials, task performance in the affected hemifield was nearly normal. However, the monkeys were severely impaired when the cue was switched frequently across trials. The monkeys were unimpaired in a pop-out task with changing targets that did not require top-down attentional control. The PFC thus appears to play a critical role in the ability to flexibly reallocate attention on the basis of changing task demands.

Published 18 October 2007 in J Neurosci, 27(42): 11306-14.
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Articles on ADHD published 2 October 2007:

Prospective effects of attention-deficit/hyperactivity disorder, conduct disorder, and sex on adolescent substance use and abuse.   Arch Gen Psychiatry, 64(10): 1145-52.

CONTEXT: Attention-deficit/hyperactivity disorder (ADHD), an early manifestation of externalizing behavior, may identify children at high risk for later substance abuse. However, the ADHD-substance abuse relationship often disappears when co-occurring conduct disorder (CD) is considered. OBJECTIVE: To determine whether there is a prospective relationship between ADHD and the initiation of substance use and disorders, and whether this relationship depends on the ADHD subtype ... [Abstract] [Full-text]

Articles on ADHD published 24 September 2007:

Neuronal nicotinic receptor agonists for the treatment of attention-deficit/hyperactivity disorder: focus on cognition.   Biochem Pharmacol, 74(8): 1212-23.

Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed neurobehavioral disorder in children and adolescents, and in about half of these patients, significant symptomology continues into adulthood. Although impulsivity and hyperactivity are the most salient features of ADHD, cognitive deficits, particularly impairments in attention and executive function, are an important component, particularly in adolescents and adults, with over 90% of adults seeking treatment for ADHD ... [Abstract] [Full-text]

Articles on ADHD published 18 September 2007:

Emerging drugs for attention-deficit/hyperactivity disorder.   Expert Opin Emerg Drugs, 12(3): 423-34.

Symptoms of attention-deficit/hyperactivity disorder (ADHD) are heterogeneous and often accompanied by comorbid psychiatric disorders. Although symptoms tend to lessen with age, many patients continue to be affected by the disorder into adulthood. Although many medications are available to treat ADHD, it is unlikely that a single medication will ever be developed to work for all patients. Recent advances, such as long-acting, extended-release formulations and transdermal delivery systems, have ... [Abstract] [Full-text]

Articles on ADHD published 4 September 2007:

Prevalence, recognition, and treatment of attention-deficit/hyperactivity disorder in a national sample of US children.   Arch Pediatr Adolesc Med, 161(9): 857-64.

OBJECTIVE: To determine the US national prevalence of attention-deficit/hyperactivity disorder (ADHD) and whether prevalence, recognition, and treatment vary by socioeconomic group. DESIGN: Cross-sectional survey. SETTING: Nationally representative sample of the US population from 2001 to 2004. PARTICIPANTS: Eight- to 15-year-old children (N = 3082) in the National Health and Nutrition Examination Survey. MAIN OUTCOME MEASURES: The Diagnostic Interview Schedule for Children (caregiver module) ... [Abstract] [Full-text]

Improving attention-deficit/hyperactivity disorder treatment outcomes through use of a collaborative consultation treatment service by community-based pediatricians: a cluster randomized trial.   Arch Pediatr Adolesc Med, 161(9): 835-40.

OBJECTIVE: To test whether adoption of a collaborative consultative service model results in improved patient outcomes. DESIGN: Twelve pediatric practices were randomly assigned to receive access to collaborative consultative services or to a control group. SETTING: Community-based pediatric offices. PARTICIPANTS: Fifty-two pediatricians and their 377 patients with attention-deficit/hyperactivity disorder (ADHD). Intervention A collaborative consultative service promoting the use of titration ... [Abstract] [Full-text]

Articles on ADHD published 27 August 2007:

Working memory, processing speed, and set-shifting in children with developmental coordination disorder and attention-deficit-hyperactivity disorder.   Dev Med Child Neurol, 49(9): 678-83.

It has been suggested that the high levels of comorbidity between attention-deficit-hyperactivity disorder (ADHD) and developmental coordination disorder (DCD) may be attributed to a common underlying neurocognitive mechanism. This study assessed whether children with DCD and ADHD share deficits on tasks measuring working memory, set-shifting, and processing speed. A total of 195 children aged between 6 years 6 months and 14 years 1 month (mean 10y 4mo [SD 2y 2mo]) were included in this study. ... [Abstract] [Full-text]

Articles on ADHD published 23 August 2007:

Stimulant therapy in the management of ADHD: mixed amphetamine salts (extended release).   Expert Opin Pharmacother, 8(13): 2127-34.

The efficacy of amphetamines in the management of attention-deficit/hyperactivity disorder (ADHD) is well established. However, their value in improving the symptoms of ADHD has been compromised by concerns about compliance, abuse potential and adverse events. An extended-release formulation of mixed amphetamine salts (MAS XR) provided the first long-acting amphetamine formulation, and thus, filled an important gap in available treatments for ADHD. MAS XR has been shown to improve ADHD symptoms ... [Abstract] [Full-text]

Articles on ADHD published 22 August 2007:

Case report: "Purely" psychiatric presentation of multiple sclerosis in an adolescent boy.   J Am Acad Child Adolesc Psychiatry, 46(9): 1213-7.

We present the case of a 14-year-old Hispanic boy with a 6-month history of a psychotic disorder necessitating several hospitalizations who was incidentally found to have multiple sclerosis with no physical findings. Neuropsychological assessment has revealed impairments in word-finding, bilateral fine motor skills, and attention. Imaging and laboratory studies have supported the diagnosis of multiple sclerosis. Steroid and immunomodulating therapy has not significantly affected psychiatric ... [Abstract] [Full-text]

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