Place Cell System
Pyramidal neurons in the hippocampus often show location specific activities in a given environment, and are called "place cells". Figure 1 shows a good example of the place cell activity as a place map (red implies higher neuronal activity). Place cell system along with the head direction system is believed to be critical for the place navigation. These marvelous neurons have amazing ability to learn and remember about the specific place. This ability of individual place cells enables us to study the physiological substrates of Learning & Memory. Furthermore, genetically engineered mice showing memory impairment in Morris water maze have shown the disruption of the hippocampal place cell system. Place cell recordings using various mutant mice with memory impairment or enhancement can provide intriguing clues that might be helpful to identify the mechanism of Learning & Memory.
Physiology of Hippocampus in NCX2 Knock-out mice
Impact of calcium flux on physiology using conditional knock-out of P/Q type calcium channel
Fig 1. Comparisons of place fields.
Sensory Gating In the Thalamus
Several thalamic nuclei such as VPL and VPM are known to relay pain or sensory information to the cortex through the thalamocortical pathway and/or interactions between thalamo-thalamic pathways. Direct delivery of those information to the cortex is made by thalamo-cortical neurons and proper feedbacks from the cortex modulate, either directly or via the reticular nucleus, the type and level of the information flows which are delivered from the spinothalamic pathway to the cortex. Single unit recordings in awake and freely moving mouse would provide more insights about how pain / sensory information are controlled by the thalamocortical - thalamothalamic networks. For this, in the lab, several different types of calcium-related mutant mice are currently being investigated.
Thalamic modulation of Pain
Figure 2. Thalamic-DBS stimulation effect on pain.
We develop MEMS tetrode for chronic recording.
Computational Neuron Model
Computational modeling based on empirical data is also used to provide more profound and fundamental understandings about functional circuits and neuronal mechanisms underlying central pain modulation and hippocampal dependent behaviors and more.
Chronic stress affects to Learning & Memory
Chronic exposure to uncontrollable stress has been shown to produce various physiological changes and impair mneomonic functions in the hippocampus. This lab work to understand how chronic stress impacts the hippocampus at the neuronal mechanism between cellular and behavioral changes by anylyzing place cell activities in the chronic stressed mouse model. This lab found that chronic stress reduced spatial stability of place field in the same environment and also induced shifts of place cell behavior to become more local cue-reliant compared than spatial cue.