Against our intuition, most neuronal activity is internally generated and not directly linked to sensory input or motor output. This internal activity, called spontaneous activity, actively contributes to network development, representation of sensory stimuli, information processing, and trial-to-trial variability of neural and behavioral
responses. Spontaneous activityis maintained even in brain slice preparations. Such in vitro spontaneous activitypurely reflects the intrinsic properties of local circuits and individual neurons and hence allows for the investigation of the internal dynamics of neuronal networks. Studies using functional multineuron calcium
imaging to probe action potentials with single-cell resolution revealed that spontaneous network activity is nonrandomly structured.
However, the functional significance of the spontaneousactivity and its spatiotemporal patterns is ill-defined. In my lecture, I will provide some keys for (re-)considering the spontaneous activity in the
brain, which include its basic properties and clinical aspects. In particular, spontaneous activity observed in fMRI and PET is expected to work as diagnostic markers for psychiatric disorders and cognitive
dysfunction, and thus it could be therapeutic targets for these diseases. If I have enoughtime, I will expand this topic to include not only neuronal networks but also glial and cerebrovascular networks, which I believe cannot be ignored for comprehensive understanding the brain operation.