capable of making functional imaging measurements. There are many research centers that have scanners exclusively dedicated for research endeavors in psychology and in neuroscience. Therefore, neuroimaging resources are readily available for use as indirect measures of brain activities—including affective processes, executive function, or memory—that are not necessarily under the subject’s voluntary control.

PSYCHOLOGICAL APPLICATIONS OF NEUROIMAGING

Neuroimaging methods have a temporal resolution of a few seconds. This makes it possible to ask a question such as: Are there brain areas in which activity predicts whether or not items will be remembered or forgotten? In fact, Wagner and colleagues (1998) have found that the magnitude of activity in the left prefrontal cortex and in the medial temporal cortex predicts whether or not memories will form. Such a study is important not only in relation to understanding memory but also because it illustrates how these methods can be used in experiments in social psychology. Because the methods are indirect, they might be ideal for use in experimental work in which direct questions may not (or cannot) elicit an appropriate response, although questions remain about neuroimaging methodology and measurement in the elderly population.

It is important to remember that neuroimaging techniques are based on indirect measures of blood flow response properties. There are many physical and physiological properties that change with aging and these must be assessed methodologically. For example, the vascular system changes with age and many older individuals are hypertensive. There are all sorts of small, low-level effects on the arteries during aging, and all of these changes may affect the signals that result in the neuroimage. The coupling of neural activity to the neuroimaging signal—the basic assumption of MRI use—may have different properties in young and elderly subjects (D’Esposito, Zarahn, Aguirre, and Rypma, 1999).

As an analogy, the brain imaging methods available today produce images that are much like satellite pictures of earth: they take a relatively long time to complete and provide only a survey of the activities going on. The resolution is poor relative to the brain’s structural components. It would be useful to measure brain activity in a way that would show the activity of individual neurons and to observe it dynamically and across networks. But what is available is an indirect measure that provides a good cursory look at the broad regions of the brain that show activity. Even so, this measure appears to be sufficient for some of the questions being asked, especially in efforts to observe how broad pathways such as the affective systems or executive systems respond and change with age.



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