東北大学脳科学GCOEセミナーのお知らせ（1/24 水関 健司 博士）
■会場 星陵キャンパス・5号館2階 201号室
■演者 水関 健司 博士
Center for Molecular and Behavioral Neuroscience, Rutgers University, U.S.A.
■演題 Temporal coordination of neuronal activity in the entorhinal-hippocampal circuit
Theta oscillations in the hippocampus are believed to be essential for the formation and retrieval of episodic memories. However, it is not clear how the information is processed and transferred in the hippocampal formation during theta states. We simultaneously recorded the activity of many (~100) neurons and local field potentials from multiple layers of the hippocampus and entorhinal cortex of rats performing spatial tasks. The temporal delays between population activities in successive anatomical stages were much longer (~60 msec) than expected from axon conduction velocities and passive synaptic integration of feed-forward excitatory inputs. We suggest that the temporal windows set by the theta cycles allow for local circuit interactions and thus a considerable degree of computational independence in subdivisions of the hippocampus-entorhinal cortex loop.
To uncover the mechanism of local circuit computation, it is essential to understand how the individual neurons in a given region participate in information processing. The hippocampal CA1 region is one of the most extensively studied regions of the brain and most studies tacitly assume that pyramidal neurons in this region represent a homogeneous cell population. However, using high spatial resolution silicon probes, we found that deep and superficial pyramidal cells were strikingly different in terms of firing rate, burst propensity, spatial representation, entrainment by slow oscillations of sleep, preferred gamma phase during waking and preferred theta phase during REM sleep. Thus, CA1 pyramidal cells in adjacent sub-layers can address their targets jointly or differentially, depending on brain states and oscillations, thereby form functionally distinct streams.
Mizuseki,K., Sirota,A., Pastalkova,E., and Buzsaki,G. (2009). Theta oscillations provide temporal windows for local circuit computation in the entorhinal-hippocampal loop. Neuron 64, 267-280.
Mizuseki,K., Diba,K., Pastalkova,E., and Buzsaki,G. (2011). Hippocampal CA1 pyramidal cells form functionally distinct sublayers. Nat. Neurosci. 14, 1174-1181.
Mizuseki,K., Royer,S., Diba,K., and Buzsaki,G. (2012). Activity dynamics and behavioral correlates of CA3 and CA1 hippocampal pyramidal neurons. Hippocampus. (in press).
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