Understanding Disorders of Attention
Understanding Disorders of Attention
The commonality in disorders of attention appears to be a dysfunctional dopaminergic system at key structures across the frontal-subcortical circuits regulating complex cognition. Despite the clinical observation that treatment with stimulant medications improves several domains of complex cognition -- for instance, executive function -- the exact profile of dopaminergic dysfunction, and therefore improvement in function, within structures of the frontal-subcortical circuits is unknown.
In other words, multiple lines of evidence clearly show dysfunction in areas of the prefrontal cortex and striatum. Evidence is conflicting with regard to whether dopamine transmission, density of dopamine receptors, and affinity of dopamine for its different receptors are increased or decreased. Other lines of research are beginning to touch on genetic and epigenetic contributions, as well as the modulation by some neuropeptide systems on dopamine.
For researchers, these findings add to the current body of knowledge on the role of dopamine in attentional disorders, but also point to more questions that need answers; for example, elucidation is needed of the "where" (the exact brain areas) and "how" (the dopamine pharmacodynamics) of dopaminergic dysfunction. For the clinician, it indicates that the demarcation among different disorders in psychiatry is not as clear as the categorical DSM nosology describes.
Several points can be extracted from this brief review:
• The cluster of inattention, impulsivity, and executive dysfunction is linked to dysfunction within areas of the frontal lobes and subcortical structures.
• It is likely that dopamine plays an important, yet not fully elucidated, role in mediating the processing of information between the frontal and subcortical areas. Therefore, it is not necessarily that there is dysfunction per se of any particular area, but rather of the "flow" of information between the frontal and subcortical areas.
• Patients who present with inattention, impulsivity, and executive dysfunction should be further evaluated for an attentional disorder, such as ADHD, because these disorders tend to be alleviated by dopaminergic stimulant and nonstimulant medications.
• It is critical to keep in mind that inattention, impulsivity, and executive dysfunction are seen in other psychiatric disorders, such as major depression, bipolar disorder, and the anxiety disorders. Patients with substance abuse and dependence disorders can also present with this triad. Even across different DSM diagnoses, research points to dopaminergic dysfunction as at least part of a common mechanism of illness.
• If an attentional disorder, such as ADHD, is appropriately diagnosed, evidence is accumulating that dopamine neurotransmission plays a role in the development of some of its characteristic features (impulsivity, as described in this article) and therefore gives more credence to and rationale for the use of stimulant dopaminergic medications for its treatment.
Viewpoint and Clinical Relevance
The commonality in disorders of attention appears to be a dysfunctional dopaminergic system at key structures across the frontal-subcortical circuits regulating complex cognition. Despite the clinical observation that treatment with stimulant medications improves several domains of complex cognition -- for instance, executive function -- the exact profile of dopaminergic dysfunction, and therefore improvement in function, within structures of the frontal-subcortical circuits is unknown.
In other words, multiple lines of evidence clearly show dysfunction in areas of the prefrontal cortex and striatum. Evidence is conflicting with regard to whether dopamine transmission, density of dopamine receptors, and affinity of dopamine for its different receptors are increased or decreased. Other lines of research are beginning to touch on genetic and epigenetic contributions, as well as the modulation by some neuropeptide systems on dopamine.
For researchers, these findings add to the current body of knowledge on the role of dopamine in attentional disorders, but also point to more questions that need answers; for example, elucidation is needed of the "where" (the exact brain areas) and "how" (the dopamine pharmacodynamics) of dopaminergic dysfunction. For the clinician, it indicates that the demarcation among different disorders in psychiatry is not as clear as the categorical DSM nosology describes.
What Does It All Mean for the Clinic?
Several points can be extracted from this brief review:
• The cluster of inattention, impulsivity, and executive dysfunction is linked to dysfunction within areas of the frontal lobes and subcortical structures.
• It is likely that dopamine plays an important, yet not fully elucidated, role in mediating the processing of information between the frontal and subcortical areas. Therefore, it is not necessarily that there is dysfunction per se of any particular area, but rather of the "flow" of information between the frontal and subcortical areas.
• Patients who present with inattention, impulsivity, and executive dysfunction should be further evaluated for an attentional disorder, such as ADHD, because these disorders tend to be alleviated by dopaminergic stimulant and nonstimulant medications.
• It is critical to keep in mind that inattention, impulsivity, and executive dysfunction are seen in other psychiatric disorders, such as major depression, bipolar disorder, and the anxiety disorders. Patients with substance abuse and dependence disorders can also present with this triad. Even across different DSM diagnoses, research points to dopaminergic dysfunction as at least part of a common mechanism of illness.
• If an attentional disorder, such as ADHD, is appropriately diagnosed, evidence is accumulating that dopamine neurotransmission plays a role in the development of some of its characteristic features (impulsivity, as described in this article) and therefore gives more credence to and rationale for the use of stimulant dopaminergic medications for its treatment.
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