Brain Activity

The brain spontaneously produces small amounts of electricity , which can be measured by electrodes placed on the scalp. This measure is called the electroencephalogram (EEG), and EEG recordings can be obtained for various regions of the brain while the participant is asleep, is relaxed but awake, or is doing a task. Such measures of regional brain activity can provide useful information about patterns of activation in various regions of the brain, which may be associated with dif ferent types of information-processing tasks (e.g., processing verbal versus spatial information, as in receiving directions from someone verbally or being shown a map of where to go). Personality psychologists have been especially interested in whether dif ferent regions of the brain show different activity for dif ferent people (e.g., introverts versus extraverts).

Another technique in measuring brain activity is called the evoked potential technique, in which the brain EEG is measured but the participant is given a stimulus, such as a tone or a flash of light, and the researcher assesses the participant s brain responsiveness to the stimulus. Several examples of how measurement of brain activity has contributed to our understanding of personality differences will be presented in the section on brain asymmetry in this chapter .

The powerful brain imaging techniques currently being developed and perfected are another class of physiological measures useful in personality research. For example, positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are noninva-sive imaging techniques used for mapping the structure and function of the brain. In fact, the 2003 Nobel prize for medicine was awarded to two researchers—Paul C. Lauterbur and Sir Peter Mansfield—for their discoverie leading to the development of fast functional magnetic resonance imaging (fMRI). This powerful imaging tool, which was developed primarily for medical diagnosis, allows physicians and researchers to look inside the working brains of their patients and subjects. This tool can show which portions of the brain are active while the person is performing a particular task. For example, if we wanted to know what part of the brain is involved in memory, we would have a sample of people perform a memory task (such as remember a phone number for 5 minutes) while their brains were scanned by fMRI.

Part The Brain Personality
Regions of the brain communicate with each other, and with other parts of the body, using electrical signals. Brain imaging techniques enable researchers to listen in on these communications.

Powerful brain imaging techniques are now being applied to the study of personality. An important study was published by Canli and colleagues (2001) in which they used fMRI to scan the brains of people as they looked at 20 negative pictures (e.g., spiders, people crying) and 20 positive pictures (a happy couple, cute puppies). They found specific brain changes associated with viewing the di ferent emotion-inducing photographs. More important, however , they found that personality correlated with the degree of brain activation in response to the positive and negative images. Specifically , neuroticism correlated with increased frontal brain activation to the negative images, and extraversion correlated with increased frontal brain activation to the positive images. Correlations between personality and other brain structures were also found, and the pattern of findings is consis tent with the notion that personality is associated with brain reactivity to emotional stimuli. The full report is posted on the Web by the American Psychological Association, at http://www .apa.org/journals/bne/bne115133.html. Brain imaging tools are very likely to revolutionize what we know about the brain and personality over the next few years, making this a particularly exciting area of research (Canli & Amin, 2002).

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