The brain or central nervous system forms a network composed of so many neurons and their function is based on complex interactions among electric neural activities, intracellular calcium signals, intercellular communications by neurotransmitter, and so on. For multi-point measurement of neural activities, fluorescent-imaging technique using voltage-sensitive dyes or calcium-sensitive dyes can be a powerful technique. This technique has been applied to measure spatiotemporal neural activities involved in the olfactory processing of the land slug Limax. In Limax, the procerebral (PC) lobe, which is the olfactory center located in the lateral part of each cerebral ganglion, spontaneously produces a periodic oscillation of local field potential (LFP) of about 1 Hz, and the phase of the LFP oscillation is advanced at the distal region, resulting in periodic propagating waves of neural activity from the distal to proximal regions. The previous studies showed that odor stimuli change the LFP frequency and the wave propagation speed. In this article, we review the previous studies, as well as our recent studies, on the spatiotemporal neural activities of the land slug Limax using fluorescent-imaging technique.
Part of the book: Organismal and Molecular Malacology
Green tea has been used as a medicine in East Asia for thousands of years. Plant-derived compounds called flavanols, which are included in green tea, may have potentials to help maintain healthy brain function. In this chapter, we review the effects of flavanols, e.g. epicatechin (EpiC), on cognitive ability in the pond snail, Lymnaea stagnalis. In this decade, the Lukowiak’s group has tested the effects of EpiC on cognition ability in Lymnaea. In a Lymnaea model system, they showed that EpiC and EpiC-containing foods have a rapid and activity-dependent effect enhancing the formation of long-term memory (LTM) following operant conditioning of aerial respiratory behavior. In the last part of this chapter, we also introduce our study for the effects of EpiC on LTM formation in another model system in Lymnaea. This study showed that EpiC increases the persistence of LTM formed by classical conditioning of feeding behavior, and suggested that EpiC alters some electrophysiological properties of a neuron in the feeding system.
Part of the book: Update on Malacology
Stochastic Loewner evolution (SLE), which was discovered by Schramm, is a kind of growth processes described by the Loewner equation having a stochastic driving function. The SLE is used as a model for random curves in statistical mechanics. On the other hand, there exist many types of self-organized curves in biological systems. Among them, the neurite curves are very diverse and inherently constitute ambiguous messages in their forms, being closely related to their functions and development. Recently, we have proposed a statistical-physical approach to analyze neurite morphology based on the Loewner equation, which leads to not only a physical interpretation of neurite outgrowth mechanism but also a new description of self-organization mechanism of complex curves. In this chapter, we first review the concept of the Loewner equation and its calculation algorithm. We next show that neurite outgrowth process can be described by the Loewner equation having a deterministic (chaotic) driving function, which differs from the SLE. Based on this point of view, we finally analyze induced-pluripotent stem cell (iPSC)-derived neurons from a healthy person and an Alzheimer’s disease (AD) patient and discuss pathological neurite states and the possibility of a medical application of our approach.
Part of the book:[Working title]