Our primary goal is to contribute to a better understanding of the neural mechanisms underlying memory-influenced behaviors, including spatial navigation, deliberation, and decision. 

Our brain has the capacity to remember a large amount of things: your best friend from elementary school in your hometown, being poked by a cactus spine in a botanic garden yesterday, a restaurant you went to on 5th avenue last month. These memories, manifested by the relationships among the underlying elements (what) embedded in spatial (where) and temporal (when) domains, are vital in guiding our future behaviors. Our brain makes, retrieves, and uses these memories through changes in neuronal activity over distributed networks comprised of many brain regions. We seek to reveal and manipulate the neural dynamics that support these complex cognitive processes. 

We use rhesus macaque as the animal model to understand how neural activity in interconnected brain networks supports memory and behavior. We are particularly interested in the hippocampal formation, retrosplenial cortex, orbitofrontal cortex, and their connected regions. We believe that higher cognition is achieved through coordinated activity over large brain networks, during both active behavior and quiescent states. To this end, we have developed a paradigm in which we combine telemetric electrophysiology, wireless eye tracking, and accurate motion tracking during naturalistic behavioral tasks. We have also designed touchscreen-based tasks to probe memory encoding and consolidation. 

We currently focus on the following questions: 

1. Relationship between the encoding of 3D spatial information and visual memory, and causal links of individual regions
To bridge the gap between rodent and human studies, this project will compare hippocampal-neocortical activity between 3D spatial exploration and visual memory tasks. We will test the hypothesis that spatial and visual mnemonic processing involves gradient computation in the hippocampal-retrosplenial-orbitofrontal circuit, differentially distributed along the hippocampal long axis and its projections. 

2. Neural dynamics underlying (long and short) memory-guided spatial exploration
In the wild, monkeys often rely on past memories to guide behavior: Where to forage about based on yesterday’s and last season’s experience? In this project, we will train macaques to navigate based on image recognition. We will study the interactions between spatial encoding and memory demands. We will test the hypothesis that strong attention & memory demands enhance spatial encoding, and spatial exploration influences mnemonic processing. 

3. Network computation in the default mode network (DMN) and Papez circuit in memory: What is the relationship between online (active processing) and offline (spontaneous) activity?
Our brains are very active during quiescent state: Neural activity exhibits rich pre-existing patterns. At the ensemble level, how neurons & network activity encode external information is somewhat restricted by the pre-existing activity, yet also very flexible. We are particularly interested in the network computation during memory encoding and navigation in the DMN and Papez circuit. This project will test how new information encoding alters (and not alter) the pre-exiting activity, and how the latter constrains possible responses. 

4. Closed-loop system to intervene in spatial navigation and memory behaviors
The lab also has a strong interest in brain-machine interface, particularly that with an application to memory. Based on the results from above-mentioned projects, we will identify particular network activity (e.g. local field potentials) that is involved in successful navigational behaviors and memory tasks. This project will employ closed-loop system to manipulate neural circuit on the fly.