Abstract
Neuroimaging plays a crucial role in psychiatry and mental health as it can potentially be used to identify causal factors, biomarkers of a disorder, prognosis or treatment, elucidate biological pathways along with informing and monitoring newer therapies. Early and prophylactic interventions present an emerging future direction in clinical psychiatry, and neuroimaging has the potential to help in identification of individuals at risk and monitor the effects of intervention. In the chapter an attempt is made to elaborate the concept of brain mapping, and differences between structural and functional brain imaging are discussed. The chapter focusses on advent of neuroimaging in psychiatry along with discussing the major functional neuroimaging techniques.
TopChapter Outline
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Introduction
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History of neuroimaging and brain mapping
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Difference between structural and functional brain mapping
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Importance of brain mapping in psychiatric disorders
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Methods of study in brain mapping
learning objectives
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To describe human brain mapping
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To describe the historical advent of brain mapping
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To differentiate between structural and functional brain mapping
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To describe the importance of brain mapping in neuropsychiatric disorders
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To describe the various methods of brain mapping
TopIntroduction
Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the nervous system. It is a relatively new discipline within medicine, neuroscience and psychology. Neuroimaging is the discipline that deals with the in vivo depiction of anatomy and function of the central nervous system (CNS) in health and disease. The term ‘neuroimaging’ is more comprehensive than the older term of neuroradiology; although in the past, neuroimaging was considered the domain of radiologists with a specific interest in the nervous system, the participants in this rapidly changing field now come from diverse backgrounds. Contributors exist in all areas in the neurosciences, including basic scientists, neurologists, neurosurgeons, psychologists, psychiatrists, physicists, chemists, and clinicians in radiology and nuclear medicine. It is important to realize that neuroimaging is a dynamic and evolving field.
In many clinical situations, neuroimaging plays the most decisive role among neurobiological investigations. Over the past four decades, the field of cognitive neuroscience has emerged as an important area in neurosciences. Cognitive neuroscience combines the experimental strategies of cognitive psychology with various techniques to examine how brain function supports mental activities (Raichelle, 2008). Neurobiological factors are important determinants of brain functioning and psychiatric illnesses. However, the cause and effect relationship between these neurobiological factors and observed psychiatric symptoms is still not well established. Although, both direct (CT scan, MRI, electrophysiological recordings) and indirect methods (plasma, urine, cerebrospinal fluid studies have established the association of neurobiological factors with psychiatric symptoms; however, these findings and associations are still under evaluation. There are many neuroimaging techniques that have been developed over years and have helped our understanding of neurobiological basis of behavior. The most commonly used neuroimaging techniques that interest students of clinical psychology will be discussed in this chapter.
Key Terms in this Chapter
f-MRI: Functional magnetic resonance imaging (f-MRI) measures the small changes in blood flow that occur with brain activity. fMRI is usually able to detect abnormalities within the brain that cannot be detected with other imaging techniques.
QEEG: Quantitative electroencephalogram (QEEG) is a diagnostic tool, which measures electrical activity in the form of brainwave patterns. QEEG is defined as a method for analyzing the electrical activity of the brain to derive quantitative patterns that may correspond to diagnostic information and/ or cognitive deficits. It is a painless, noninvasive procedure that takes around 30 minutes and helps in identification of neuropsychiatric problems.
PET: PET scan is an imaging technique that uses a very small dose of radioactive substance/s called radiotracer, to help image and study the functioning of various organs and tissues. The radioactive tracers used for PET are specially synthesized molecules which contain positron emitting isotope of common elements like carbon, oxygen, nitrogen and fluoride.
EP: An evoked potential (EP)or evoked response is an electrical potential recorded from the nervous system after the presentation of a stimulus. Neuroelectrical responses to sensory stimuli can be readily and non-invasively recorded using this averaging technique first employed by Dawson (1947) . To generate EP record, the EEG may be used to measure brain activity following a sensory stimulus.
Neuroimaging: Neuroimaging or brain imaging is the use of various techniques to either directly or indirectly image the structure, function, or pharmacology of the nervous system. It is a relatively new discipline within medicine, neuroscience and psychology. Neuroimaging is the discipline that deals with the in vivo depiction of anatomy and function of the central nervous system (CNS) in health and disease.
SPECT: Single photon emission computed tomography is a functional nuclear imaging technique that allows visualization and quantification of different in vivo physiological and pathological features of brain neurobiology. Brain SPECT can be used to define a patient's pathological status when neurological or psychiatric symptoms cannot be explained by structural neuroimaging findings.