The 13th Annual Scheibel Distinguished Postdoctoral Fellow Lecture 2015 -- Denise Cai, PhD

The BRI's Arnold Scheibel Distinguished Postdoctoral Fellow in Neuroscience Lecture honors one postdoctoral fellow annually for outstanding research in neuroscience, comprises part of the Joint Seminars in Neuroscience series, and confers a prize to attend a scientific meeting.

The 2015 award winner, Denise Cai, PhD, is from the laboratory of Alcino Silva, PhD, in the UCLA Departments of Neurobiology, Psychiatry & Biobehavioral Sciences and Psychology. She presents "Linking Memories Across Time".

Denise is introduced by Alcino Silva, PhD, Distinguished Professor, Psychology and Behavioral Neuroscience, Director, Integrative Center for Learning and Memory, Distinguished Professor, Tennenbaum Center for the Biology of Creativity, Professor, Neurobiology at UCLA's David Geffen School of Medicine.

Abstract: Recent studies suggest the hypothesis that a shared neural ensemble could link distinct memories encoded close in time. According to this hypothesis, one memory triggers a temporary increase in neuronal excitability that biases the representation of a subsequent memory to the same neuronal ensemble encoding the first memory, such that recall of one memory increases the likelihood of the recall of the second memory. Accordingly, using in vivo calcium imaging with a miniature fluorescent microscope and immediate early gene expression with TetTag transgenic mice, we found that the overlap between the hippocampal CA1 ensembles activated by two distinct contexts acquired within a day is higher than when the two contexts are separated by a week. Multiple convergent findings indicate that this overlap of neuronal ensembles links two contextual memories. First, fear paired with one context is transferred to a neutral context when the two are acquired within a day but not across a week. Second, the first memory strengthens the second memory within a day but not across a week. Older mice, known to have lower CA1 excitability, appear to have disruptions with linking memories encoded close in time. They do not show the overlap between ensembles, the transfer of fear between contexts, or the strengthening of the second memory. Taken together, these findings demonstrate that contextual memories encoded close in time are linked by directing storage into overlapping ensembles. Alteration of these processes by aging could affect the temporal structure of memories, thus impairing efficient recall of related information.