University of Texas at Austin > Institute for Neuroscience > What Do I Want to Discover? > Hitoshi Morikawa, PhD
Hitoshi Morikawa

Hitoshi Morikawa, PhD
Associate Professor of Neurobiology


What do you want to discover?

I want to discover how the brain becomes addicted.

A rat dopamine neuron filled with a
fluorescent calcium indicator.

Since the original description of Pavlov’s drooling dog in the early 20th century, a great deal of progress has been made in our understanding of the way in which animals (and humans) can be trained to attach meaning to and then respond to certain stimuli in the environment. We now know that the brain dopaminergic system, which originates in the ventral midbrain and projects to diverse brain areas, such as the striatum and the prefrontal cortex, plays a critical role in this learning process. A recent exciting theory posits that midbrain dopamine neurons provide a timed teaching signal for reward-based learning by promoting plasticity of synapses and neuronal excitability in target brain areas. However, it is not well understood how exactly this is accomplished at the single neuron and local circuit levels. To tackle this issue, we perform electrophysiological recording and fluorescence imaging of neuronal activities in an in vitro brain slice preparation. We also use animal models of drug addiction, which can be viewed as a maladaptive form of reward-based learning resulting from excessive dopaminergic transmission caused by addictive drugs. Using brain slices from animals conditioned to these drugs, we are discovering dramatic changes in the dopaminergic circuit that may explain why these animals are addicted to the environment and behavior associated with drug intake.

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