ausblenden:
Schlagwörter:
Reward learning and memory, neural circuits, dopamine,
somatosensory cortices, conditioned place preference
Zusammenfassung:
Learning and memory are two corresponding neural processes. Learning is
a neural actitivity depending on experience and changing organ’s
behaviour to adapt the enviorement.Memory is a neural processing which
storages and retrieves learned information. Reward and punishment
learning and memory protect animals to approach the benefits and avoid
risks for better life. Although researches are exploring the mechanism
of the brain work, a large amount of studies are required to reveal the
truth in the future.
In the first chapter of this thesis, I will explain the research on
neural circuits underlying appetitive olfacotory associated learning and
memory in Drosophila melanogaster. I will introduce the methods and
technics to study the olfactory learning and memory in flies such as
classical olfactory conditioning and gene manipulation (i.e., GAL4/UAS
system), introduce the current status of studies on neural circuits in
olfactory associative learning and memory, and my project: a subset of
dopamine neurons signal reward for odour memory. Previous studies
revealed that dopamine signals aversive reinforcement in insects, and
identified that PPL1 cluster and MB-M3 neurons in PAM convey aversive
reinforcement to vertical lobes and tip of horizontal lobes of the
mushroom body, respectively. Octopamine was thought to be involved in
appetitive learning and memory, but no cellular identification and
circuit description. In our study, by transient activation and
inactivation of target neurons in intact behaving flies, we show that a
group of dopamine neurons in the protocerebral anterior medial (PAM)
cluster signals the sugar reward. In vivo calcium imaging revealed that
these dopamine neurons are activated by sugar stimulus and the activation
is increased in starved flies. Our results highlight the cellular
specificity underlying the various roles of dopamine and the importance
of spatially segregated local circuits within the mushroom bodies.We
identified the specific dopamine cluster neurons tht signal reward to the
horizontal lobes of the mushroom body for the first time, and suggested
a prelimary relationship between octopamine and dopamine signaling.
Drug addiction is a particular and extreme rewarded memory, and a
concerned social issue. In the second chapter, I will introduce
conditioned place preference model of drug related memory and local
leision in the rats’brain as the tools to investigate the characters of
drug related memory and the role of corresponding brain area in reward
conditioning.We revealed that somatosensory cortices are required for the
acquisition of morphine related memory whereas the urge to seek drugs
requires the insular cortex.
Although our studies have demonstrated neural circuits of reward
learning and memory in flies, and one of important brain cortices in
morphine related memory formation in rats. However, we can not completely
understand the mechanism of reward learning and memory, and solve the drug
abuse problems. Thus, lots of works need to be done in future.