Representation, Storage, and Decay in Auditory-Verbal Working Memory

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The overarching goal of the proposed research is to significantly advance our understanding of the neural mechanisms underlying verbal working memory. Decades of research on the cognitive psychology of verbal working memory have shown that the primary way in which people keep verbal information in mind is through subvocal rehearsal, or inner speech. In other words, to keep verbal information aloft in consciousness we make use of our capacity to carry on an internal conversation with ourselves. In Baddeley and colleagues' classic model of verbal working memory, the phonological loop, inner speech is decomposed into two communicating components: a motor/articulatory process and a phonological/auditory component. In the last 20 years, cognitive neuroscience has tried to understand how these two components "map" on to the brain. However, we still have a poor understanding of the mechanistic basis of verbal working memory. Thus, while we know that during the online maintenance of verbal information both motor/ and auditory cortical areas are "active", we have a poor of the computations carried out by these regions.***In this proposal we use a series of functional magnetic resonance imaging (fMRI) studies to elucidate memories for speech are coded in the brain's auditory cortex. With the advent of multivoxel pattern analysis (MVPA) techniques, it is now possible to capture and reliably identify distributed patterns of neural activation that code for particular stimuli or cognitive states. Here we take advantage of this extraordinary development in fMRI technology to "decode" the patterns of activity in auditory cortex that are manifested during auditory memory retrieval and inner speech. First, we will test the hypothesis that patterns of activity evoked by external and inner speech share a representational basis in auditory cortex. Second, we will test a prominent account of inner speech that suggests that it emerges as a result of motor-to-sensory discharges that are part of an internal monitoring circuit important for error correction in speech production. Last, we will investigate how "surface features" of perceived speech, such as gender and accent, are incorporated into the auditory memory traces that are activated during working memory.***Although the focus of this proposal is in the auditory-verbal modality, the implications go beyond this "model subsystem" because the what we learn from the current set of experiments will be relevant and applicable to other memory domains. Furthermore, a key aim of this work is to continue to pursue a set of unifying principles that underlie the storage, representation, and activation of different kinds of memory, including verbal, visuospatial, short- and long-term, episodic and semantic. This work, therefore, is part of a larger career-spanning program with the long-term goal of devising a more coherent and less compartmentalized understanding of human memory.**