The ability to localize the neural circuitry underlying specific mental processes is rapidly increasing our understanding of normal brain function. Processes such as perception, attention, emotion, memory, language, and motor function can be investigated in increasing detail, and at various levels of development.
These techniques can also be used to examine brain dysfunction in the setting of neuropsychiatric disorders. This is of particular importance in the study of psychiatric disease, in which there is often no obvious gross abnormality in brain structure. Symptoms can be imaged directly, as they are occurring, in a bottom-up approach. Alternatively, neuropsychological functions that are hypothesized to be abnormal in a particular disorder can be probed in a more top-down examination. In addition, the functioning of specific brain regions or circuits can be assessed using psychological probes known to activate those regions in normal control subjects. Localization of sites of abnormal function is a first step toward the development of more targeted diagnostic and therapeutic approaches. In conditions such as stroke, these methods are modifying our understanding of brain plasticity that occurs with recovery of function, with implications for novel rehabilitative approaches.
Recent studies have evaluated the effect of fMRI results on the diagnostic work-up and treatment planning of consecutive seizure disorder, or Epilepsy patients. The fMRI findings helped five patients avoid additional surgery and altered the extent of surgery in four others.
Until recently, the Wada test and electrical cortical mapping--both invasive, costly tests that require large medical teams--were the only methods for identifying these critical areas. fMRI, which uses radio waves and a strong magnetic field, is a non-invasive test capable of identifying the location of critical brain functions that could be affected by the location of the seizure focus. Based on fMRI results, five patients in the study avoided a two-stage surgery with extra-operative direct electrical stimulation mapping and instead received a one-stage resection surgery. The extent of surgical resection was altered in another four patients, because fMRI images identified critical areas of the brain close to the seizure focus.
For more information on Epilepsy and the role of neuroimaging in its treatment and diagnosis, visit our Medivision web portal at epilepsy-info.com.
Pharmacodynamics is often summarized as the study of what a drug does to the body, whereas pharmacokinetics is the study of what the body does to a drug. Pharmacodynamics is sometimes abbreviated as "PD", and when referred to in conjunction with pharmacokinetics can be referred to as "PKPD". Scientists have made significant progress in understanding the possible causes of Alzheimer's disease, but many questions remain. It is likely that both inherited and environmental factors interact in complex, poorly understood ways to cause the disease.
Understanding the pharmacodynamic principles of antipsychotic medications can be very helpful in guiding clinicians in certain key aspects of psychopharmacologic practice, including medication selection, dosing, and management of adverse events. Presenting the clinically salient aspects of antipsychotic pharmacodynamics involves understanding the concept of how these agents differentially affect the dopamine system, and the range of binding actions on other monoamine receptors besides the family of dopamine receptors. Understanding the pharmacology or drug disposition of atypical antipsychotic agents - including their absorption, distribution, metabolism, and elimination - is essential, as these characteristics impact dosing, drug-drug interactions, withdrawal effects, and eventually the efficacy and safety of these medications. Side effects can complicate and undermine antipsychotic treatment in various ways by causing or worsening symptoms associated with schizophrenia, including negative, positive, and cognitive symptoms as well as agitation.
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