Cellular and circuit mechanisms underlying hippocampal information processing
Title: Cellular and circuit mechanisms underlying hippocampal information processing
Presenter: Qian Sun (孙钱)
Associate Research Scientist
Department of Neuroscience
The hippocampus, composed of areas CA1, CA2 and CA3, is crucial for spatial navigation and learning and memory. Despite the intense studies over the past half century, the cellular and circuit mechanisms by which information flows through the hippocampal circuitry are still incompletely understood. In the first part of this seminar, I will present my findings at the cellular level on how hippocampal CA1 and CA2 pyramidal neurons utilize distinctive dendritic and synaptic mechanisms─including dendritic sodium spikes (Sun et al., eLife 2014) and presynaptic NMDA receptors (Sun et al., in preparation)─to dynamically regulate information transfer from entorhinal cortex to the hippocampus. The second part of the seminar will focus on CA3 circuitry, a hippocampal area crucial for associative learning and memory (Sun et al., Neuron 2017). I will present my recent work at the circuit level that marked transverse (or proximodistal) gradients in dorsal CA3 neuron synaptic connectivity can account for distinct spatial encoding and behavioral role of CA3 subregions (CA3a, b, and c) along the proximodistal axis. Furthermore, I will present evidence that the proximodistal heterogeneity in excitation-to-inhibition balance of CA3 recurrent network leads to a nonuniform pattern of memory reactivation during contextual fear learning. Together, my data and others suggest CA3 pyramidal neurons at different anatomical position are functionally heterogeneous and play diverse behavioral roles.