Research Areas

1. Investigating the role of the evolutionary conserved limbic circuit within vertebrates.
   We investigate the role of neural circuits that control the selection and execution of emotional behaviors. We study fish and rodents using various methods including the genetics, molecular and cell biology and physiology. In mammalian telencephalon, the cortico-basal ganglia circuit is thought to be involved in selection of the behavioral programs (Figure A). External physical information and related emotional information enter the cortico basal ganglia circuit via the hippocampus and amygdala, respectively, and modulate this circuit to establish ensembles of neurons encoding various behavioral programs (Figure A). However, it is still unclear how a particular ensemble of neurons becomes selected through this neural circuit.
   Zebrafish (teleosts) have the simplest neural system in the vertebrates. By the movement of the neural tube called eversion, the hippocampus and amygdala in fish become located in the medial and lateral part of the telencephalon, respectively (Figure B), showing the inside out position with respect to that of mammals. Furthermore, it has been recently shown that the zebrafish telencephalon may contain the cortico-basal ganglia circuit where the behavioral programs become stored. Zebrafish brain is so small that we can analyze the neural activities of the entire cortico-basal ganglia circuit by the calcium imaging. By combining with the optogenetics to interfere the activity of the cortico-basal ganglia circuit, we believe that the common neural mechanisms between fish and mammals which underly the establishment of the memory for the behavioral program will be unveiled.
2. Exploring the role of habenula in emotional behaviors.
   We also focus on the habenula, a nucleus located in the dorsal midbrain. Mammalian habenula consists of the medial and lateral nucleus (Figure C, E), which control directly and indirectly dopaminergic neurons in the ventral tegmental area and serotonergic neurons in the Raphe, respectively (Figure C, D). The medial and lateral parts of the habenula in mammals correspond to the dorsal and ventral habenula in fish, respectively (Figure E), and the connectivity of each subnucleus is well conserved between fish and mammals (Figure D, E). We are trying to reveal the role of this well conserved habenula circuit in the control of emotional behaviors. In deed, when the zebrafish dorsal habenula is inactivated by the neurotoxin, fish tend to select the freezing instead of the agitating behavior in the cued-fear conditioning (Figure F). We study the role of the habenula in switching of the emotional behaviors, the adaptive fear learning, the aggressiveness or the social dominant-subordinate relationships, using zebrafish, rats and mice.
3. Studying the mechanism of the sensory neuron development and adult neurogenesis.
   We study the role of Trk signaling pathway in the sensory neuron development and adult neurogenesis using zebrafish and mice.

Research Subject

1. Investigating the role of the evolutionary conserved limbic circuit within vertebrates.
2. Exploring the role of habenula in emotional behaviors.
3. Studying the mechanism of the sensory neuron development and adult neurogenesis.

Related links

1. RIKEN Brain Science Institute Website_Laboratories Page
2. Individual Website Laboratory Page
3. National BioResource Project ZEBRA FISH Page

Press release

January 27, 2011

Mechanism uncovered explaining why neuronal stem cell mitosis is restricted to only the ventricle side

October 11, 2010

Study identifies neural pathways governing switching of fear responses in the zebrafish

RIKEN RESEARCH

April 28, 2011

Following directions
A key regulator of nervous system development works by blocking a signaling protein with multiple roles in stem cell maturation

December 17, 2010

Fish frozen in fear
Fear responses of zebrafish are controlled by brain structures of previously unknown function

March 23, 2007

Timing is everything
New work sheds light on the processes determining brain asymmetry