(Cancelled) Daisuke Shimaoka: “Mesoscale structure of spontaneous dynamics and visual processing”


July 31, 2018  16:00 〜 15:00

CiNet 1F Conference Room
(Cancelled) Daisuke Shimaoka

UCL Institute of Ophthalmology
University College London

Host :  Izumi Ohzawa (PI)




Without sensory stimulation, the sensory cortex is spontaneously active, at the scale of single neuron up to multiple cortical areas. The spontaneous activity shifts its temporal characteristic according to the level of arousal, from spontaneous transition of depolarized and hyperpolarized phases (slow wave) under deep sleep to fluctuation at a certain level of membrane potential without slow waves under the fully alert state.
In each of the arousal level, what is the spatial structure of the spontaneous activity on the cortical surface?

To address this question, we optically imaged population neural activity of a large portion of the mouse left and right cortices using genetically encoded voltage or calcium indicator, near millisecond time resolution and at columnar-level spatial resolution, from various levels of arousal.
High and stable expression of the indicator achieved by a transgenic mouse line enabled to chronically monitor genetically identified neurons over several months.

From deep anesthesia till awakening, we found that depolarizing waves recruiting the majority of the cortex appeared as a conserved repertoire of distinct wave motifs. Toward awakening, the incidence of individual motifs changed systematically and both local and global cortical dynamics accelerated.
During free-running, we found transient depolarization or hyperpolarization depending on the modality of sensory cortex. In between the two extreme conditions when the animal is awake and constantly engaged in a visual detection task, we observed that spontaneous slow waves appeared symmetrically in both hemispheres, and found that they were linearly superimposed upon visually-evoked activity in the mouse cortex.

In summary, these studies revealed that spatio-temporal structure of spontaneous activity changes systematically according to the arousal level, and it impacts on visual information processing.