Introduction
The reward system, or reward pathway, is a part of the brain that becomes activated when we experience or about to experience something pleasurable. It is what allows us to feel joy and motivation. Without this feedback, we will not be able to think, remember and feel properly.
History
The reward system was first discovered in 1950 by James Olds and Peter Milner. They implanted electrodes into rats that sent small shocks when the rat pulled a lever. The two found there is a region in the brain where rats repeatedly pulled the lever to receive the stimulus. One of the rats pressed the lever up to 7500 times in just half a day.
Mechanism
When the brain receives a rewarding signal, it releases the neurotransmitter dopamine. There are several dopamine pathways that do this. The four major ones being, the Mesolimbic Dopamine Pathways, Mesocortical Dopamine Pathways, Nigrostriatal Dopamine Pathways, and the Tuberoinfundibular Dopamine Pathways. The first and second of these are particularly involved in our reward system.
The Mesolimbic Dopamine Pathways start at the ventral tegmental area (VTA) located in the midbrain. The VTA releases dopamine that is sent mainly to the nucleus accumbens, amygdala, and the hippocampus. The nucleus accumbens is considered to control both the motor system and the limbic system. So it is thought that it is here that we feel the pleasure and makes us do the action again. The amygdala on the other hand controls emotions. Here we feel happiness from the action we took. The hippocampus is where information is stored in the brain. This section is activated so we can remember precisely what caused the pleasure.
The Mesocortical Dopamine Pathways is similar to the Mesolimbic pathway but the destination of dopamine is the prefrontal cortex, along with other areas of the cerebral cortex. The prefrontal cortex allows us to concentrate on tasks.
Parallel to the dopamine pathway, information is also transmitted around the brain. Information is passed around the regions of the brain dopamine activated. After the VTA, information is passed to the prefrontal cortex, where it is turned to short term memory and we make things like decisions. Then, if the information is important, it will be sent to the hippocampus for long term storage.
Adaptation
The two major adaptations of studies on the reward system is in the studies of addiction and disease of the brain such as Parkinson’s disease.
Another adaptation is to enhance our ability to think and recognise. For example, say you want to study. By using how the dopamine from the VTA is what activates areas like the prefrontal cortex and the hippocampus, we can see that we must somehow enjoy the experience of studying to get the most out of our brains.
[1] Neuroscientifically Challenged (2015), “2-Minute Neuroscience: Reward System”. https://www.youtube.com/watch?v=f7E0mTJQ2KM. Last accessed: 2020/01/28
[2] Neuroscientifically Challenged (2018), “2-Minute Neuroscience: Dopamine”. https://www.youtube.com/watch?v=Wa8_nLwQIpg. Last accessed: 2020/01/28
[3] Neuroscientifically Challenged (2016), “2-Minute Neuroscience: Ventral Tegmental Area (VTA)”. https://www.youtube.com/watch?v=4t1EsfhPBTk. Last accessed: 2020/01/28
[4] Neuroscientifically Challenged (2015), “2-Minute Neuroscience: The Hippocampus”. https://www.youtube.com/watch?v=5EyaGR8GGhs. Last accessed: 2020/01/28
[5] Neuroscientifically Challenged (2016), “2-Minute Neuroscience: Amygdala”. https://www.youtube.com/watch?v=JVvMSwsOXPw. Last accessed: 2020/01/28
[6] Neuroscientifically Challenged (2016), “2-Minute Neuroscience: Nucleus Accumbens”. https://www.youtube.com/watch?v=3_zgB19TE-M. Last accessed: 2020/01/28
[7] Hayashi, Nariyuki (2009), “脳に悪い7つの習慣”. Gentosha Literary Publication. Last accessed: 2020/01/28
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