Human Behavior in Military Contexts (2008) / Chapter Skim
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Neurophysiological Approaches to Understanding Behavior--Todd F. Heatherton, Anne C. Krendl, and Dylan D. Wagner
Neurophysiological Approaches to Understanding Behavior--Todd F. Heatherton, Anne C. Krendl, and Dylan D. Wagner
Pages 217-238
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. Most recently, social neuroscience is an emerging field that uses the methods of neuroscience to understand how the brain processes social information.
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Throughout this paper we focus on the vexing issue of the extent to which psychological functions are localized in discrete brain regions, which can be considered one of the major challenges in much contemporary brain research. INTELLECTUAL HISTORY By the beginning of the 19th century, anatomists had a reasonably good understanding of the basic structures of the brain.
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That is, although there is considerable support for the general idea of specialization, virtually every behavior involves the joint activity of many brain regions. As we discuss below, identifying specific functions for discrete brain structures remains an ongoing challenge for neurophysiological approaches to studying behavior.
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that accompanies neuronal activity. Methods such as PET and fMRI are relatively high in spatial resolution, but because of the rather sluggish nature of blood flow, they are low in temporal resolution.
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EEG provides a wealth of information about global brain activity and is therefore commonly used in clinical settings to study sleep cycles and diagnose neurological disorders, such as epilepsy. However, because EEGs register all brain activity, the signal is noisy, and it cannot provide information about specific changes in brain activity in response to a stimulus or cognitive task.
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Unlike EEG, MEG does not require electrodes; rather, it uses special sensors that detect magnetic fields. MEG has the same temporal resolution as ERP because it is basically measuring the same neural activity measured by EEG; however, because magnetic signals are not distorted by the skull, as are EEG signals, the MEG signal localization is far superior.
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Positron Emission Tomography (PET) The brain imaging methods that have produced the greatest scientific enthusiasm in recent times measure metabolic processes rather than electrical activity.
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In addition to identifying the specific underlying mechanisms that motivate physical and psychological processes, PET provided investigators with a powerful method for addressing research questions that are difficult to study using behavioral methods. Memory researchers, for instance, long debated whether different forms of memory (e.g., encoding new memories or retrieving old ones)
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. Research using fMRI has provided insight on the modulatory role of the prefrontal cortex over subcortical regions, such as the amygdala.
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Afterwards, memory for the items was tapped in a surprise recognition task. By contrasting brain activation elicited by items that were later remembered with those that were later forgotten, it was possible to identify brain regions that predict successful recognition.
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An early limitation of morphometry was that it relied on manually segmenting brain regions, a method that is prone to subjective bias or error. As morphometry becomes increasingly popular, numerous automated segmentation techniques for measuring grey and white matter have developed.
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used VBM to show that experienced musicians have increased grey matter density in Broca's, an area of the brain important for language. Another popular method for studying cortical structures is analyzing cortical thickness (Fischl and Dale, 2000)
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To understanding how different brain regions are connected, it has proven useful to examine white matter fiber tracks, which are bundles of myelinated axons that connect brain regions. The advent of diffusion tensor imaging (DTI)
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Transcranial magnetic stimulation (TMS) allows for the reversible experimental disruption of neural activity in relatively circumscribed cortical regions while study participants engage in a cognitive task (Jahanshahi and Rothwell, 2000; Walsh and Cowey, 2000; Wig, Grafton, Demos, and Kelley, 2005)
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By applying repetitive TMS over the posterior parietal cortex of the left or right hemisphere, thereby disrupting activity in that area, the researchers were able to show a concomitant increase in visuospatial attention in the opposite visual field. This finding demonstrates that visual attention is a resource that is shared between brain areas responsible for the left and ride side of visual space and that by inhibiting activity in one region, competition for attentional resources is eliminated and attention to the noninhibited side of visual space is increased.
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Assessing patients who have brain injuries can provide complementary evidence for the causal involvement of a brain region for a given psychological function. Another conceptual issue is the difficulty in localizing specific psychological functions to discrete brain regions.
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Conversely, a region in vACC was uniquely sensitive to social feedback, with significantly greater response to negative feedback than positive feedback, irrespective of expectancy violations. The lesson from this study is that simply observing activation in a specific brain region does not necessarily identify the psychological processes that underlie that activation.
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. Whole-brain voxel-based statistical analysis of gray matter and white matter in temporal lobe epilepsy.
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. Transcranial magnetic stimulation of the human frontal eye field facilitates visual awareness.
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. Compromised white matter tract integrity in schizophrenia inferred from diffu sion tensor imaging.
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. Loss of connectivity in Alzheimer's disease: An evaluation of white matter tract integrity with colour coded MR diffusion tensor imaging.
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. Transcranial magnetic stimulation and cognitive neurosci ence.
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