Echolocating bats produce ultrasonic vocalizations in the air and listen to the echoes returning from objects to obtain information about their surroundings. They have been extensively experimented in artificial environments as model animals to investigate the auditory mechanism that achieves highly-sophisticated echolocation. On the other hand, the use of ultrasound by bats in natural environments has not been well-studied due to its high measurement difficulty, although the bats have shown high sonar performance of feeding small flying insects one after another in the field. In this century, with the improvement of measurement technology, many observations on bio-sonar operations by bats such as directional control for prey search and localization have been reported. Furthermore, the rational strategy of echolocating bats to catch multiple prey effectively one after another in a row has become clear in recent years. In this paper, we review the bat echolocation during foraging flight, focusing particularly on field studies. We first overview the fundamental characteristics of bat echolocation, and then divide the foraging flight into following three situations; (1) prey search, (2) prey-capture flight and (3) multi-target capture flight, in order to discuss their echolocation strategy for foraging.
The brain is a system that can generate information internally and spontaneously to create its own functional structure as well as updating specific persistent internal states to optimize the information representation. Recent studies have suggested that “spontaneous activity patterns” play important roles during these processes. However, we still do not know how the patterned spontaneous activity of the brain network translates the information to regulate these processes. Moreover, molecular mechanisms underlying the patterned spontaneous activity are largely unknown. In this review, we introduce recent studies showing temporal structure of spontaneous activity patterns as well as their molecular regulatory mechanisms. By reviewing common and different mechanistic strategies between developmental and adult stages, we hypothesize that spontaneous activity patterns allow for diverse signaling mechanisms that can be useful in signifying specific persistent internal states of the brain. Also, we discuss the necessity of advanced methodological approaches in both experimental and computational techniques towards better understanding of the functional significance of temporal structure of spontaneous activity of the brains.