Much of our research focuses on understanding human memory functions and their implementation in the brain. Multiple techniques for measuring brain activity are combined using a Cognitive Neuroscience approach that respects the complexity of cognition as well as the detailed organization of the brain.
A central type of memory currently under study is conscious recollection, which is associated with memory for facts and events. This is the experience most people would associate with remembering. Another type of memory, perceptual priming, is generally measured as a facilitation in performance on implicit memory tests -- in these tests subjects are not necessarily aware that memory is being tested. Juxtapositions of recollection and priming serve to illuminate the ways in which these two types of memory differ in both their cognitive and neural facets.
Evidence from Neuropsychology suggests that anterograde amnesia, which can occur following damage to midline diencephalic or medial temporal brain regions, involves a disruption of recollection while sparing priming. Many theoretical explanations for this dissociation have been put forward. One possibility is that amnesia arises due to a disruption of a special process ("cross-cortical consolidation"), that is specifically required for memory storage with respect to facts and events. Some of our recent investigations explore the possibility that consolidation can move forward during sleep, not just during waking.
Functional Neuroimaging (using PET or FMRI methods) has been used to obtain images of brain areas active during normal cognition. These methods can also be used in patients with amnesia to show how focal brain damage can disrupt functioning in distant brain locations. Results from neuroimaging in the coming years may thus be helpful for clarifying the critical roles played by particular brain areas in encoding, storage, and retrieval.
Measures of the electrophysiological activity of the brain, such as event-related potentials or ERPs, can also be very useful. In my laboratory, ERPs are recorded noninvasively to monitor human brain activity that occurs in association with various cognition functions. These brain potentials provide real-time measures of neural information processing with an unsurpassed degree of temporal precision. Recent results from my laboratory have shown that particular brain potentials are associated with memory retrieval during recollection, with certain aspects of strategic retrieval, and with various types of priming.