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neurobiology of addictive behavior
Research Strategy
 Addiction is a state of mind that is represented with compulsive need or desire to intake chemical substances or indulging in some behavior, such as gambling. Trying to stop or reduce addictive behavior is very frequently unsuccessful despite the clear will to do so. Why addictive behavior could be a research topic of the implicit brain function? Addictive behavior is out of our intentional control. Addicts are not aware of origins of their motivation. Their decision making, preference, and seeking/approaching behavior are clearly biased, but the biases are mainly originated from unconscious neural information processing. Therefore, addictive behavior is thought to be a phenomenon that the function of implicit brain is manifested in its extreme form.
 As a part of the implicit brain function project, our research group has two major missions.
 One is to elucidate biological bases underlying our unconscious information processing related to liking and/or wanting. Addictive behavior has many common features with implicit brain functions, unawareness, autonomic, task-independency, physical, and so on. Neural mechanisms that produce these features mainly belong to phylogenically old subcortical regions, such as the limbic system, the midbrain, and the brain stem. Our group will explore influences of functions of these regions on behavior by means of electrophysiological and neurochemical analysis in experimental animals.
 The second mission is to explore the biological markers that distinguish normal and abnormal behaviors, if they exist. Many addictive behaviors interfere with everyday life and cause social problems. However, it is not clear whether specific neural systems or chemical substances in the brain are active when addicts’ need or desire to become compulsive. Surely it is difficult to distinguish normal and abnormal behavior in experimental animals, but recent literature propose several possible methods to reproduce behavioral features of human addicts in animals. Finding biological markers which depicts abnormal preferences or the seeking of some objects has clinical and social significance.
 Our studies consists of the following three major strategies:

1) Study on neural mechanisms of animals’ preference: Animals show preference for the environment that associate with the rewarding effect of chemical substances and/or events. They choose the environment more frequently and stay longer time in it. This well known behavior is called “conditioned place preference” and the brain “reward” system relates to this behavior. However, the very basic question, why an animals’ body moves toward the “preferred” side has not been answered. This is a type of spatial learning where neural systems including hippocampus are thought to play important roles. We will seek for the neural mechanisms that integrate information about environmental cues, rewarding events, spatial memory, and those that generate the motor commands.

2) Study on regulating mechanisms of substance intake: The intake of natural reward, such as food and water, is usually regulated by the homeostatic mechanisms. However, binge intake of addictive substances occurs when such homeostatic mechanisms become aberrant. Recent studies show such aberration is related to cyclic up and down of mood and putative neural substrates of the cycle have been proposed. We develop a model behavior of binge intake using drug self-administration technique, monitoring neural activity and/or dynamism of neurotransmitters in the brain, then feed back them to the animals’ brain and examine the influence on behavior.

3) Study on sensory reward: Many abused chemical substances produce sensory modification in humans, sensitizing specific sensory experiences, causing hallucinations, or distorting time perception. These sensory modifications produce a hedonistic mood and the mood reinforces compulsive access to these substances. However, due to technical difficulties in examining sensory experience in animals, the role of sensory modification in addiction has not been well documented. Recent advancement of studies on cannabinoid receptors and their endogeneous ligands opened the way to examine modulating roles of cannabinoid system on the sensory experience. We developed a behavioral technique to evaluate sensory modification and explore the interaction between cannabinoid and other neurotransmitter systems.

 We try to elucidate the neurobiological origin of unconscious compulsive motivation, addiction, based on these studies and collaboration with other research groups in the implicit brain project, as well as the leading research facilities in this field.

Staff Members
Group Leader Naoyuki Hironaka
Researcher Miwako Matsuda
Research Assistant Nobuaki Takahashi
Tomoko Tanaka
Michio Itasaka
Yuji Takano
Address of
Research Laboratory
NTT Atsugi Research and Development Center 3-1,
Morinosatowakamiya, Atsugi-shi,Kanagawa 243-0198, Japan
Phone : 046-290-5615
FAX : 046-248-2911

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Exploratory Research for Advanced Technology 
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