Investigations of the neural mechanisms underlying activation, rehearsal, and decay in human working memory

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Working memory is a cognitive system that has evolved for the purpose of storing, processing, and manipulation of small quantities of information. For instance, working memory is used to keep a phone number in mind, to do mental arithmetic, or to juggle two tasks at once. When the information to be maintained in working memory is verbal, the system can take advantage of the fact that speech can be represented both in terms of the way it sounds (i.e. its perceptual code) and in the way it is spoken (i.e. its motor code). Many years of cognitive psychological research on verbal working memory has shown that the way verbal information is kept "active" in memory is by a continual conversion between auditory and motor representations of speech; and this process occurs in a system that is called the "phonological loop". In the past 20 years, the phonological loop has been mapped out in the brain using functional neuroimaging techniques. The current research seeks to demonstrate, using functional magnetic resonance imaging (fMRI), that the brain's ability to convert between auditory and motor representations of sound crucially depends on a brain region located in a posterior part of the superior temporal lobe, named area Spt. In addition, this research will show that Spt is not just important for verbal working memory, but is indeed generally important for cognitive activities that involve the linking or mapping between auditory perception and motor production -- which includes vocabulary acquisition, foreign language learning, and many musical abilities.