The Brain and Reward
There are three main components of the brain that are involved in processing reward. The first is called the nucleus accumbens. The nucleus accumbens is referred to as the brains pleasure centre. It is located above and just behind your sinuses. The second is called the prefrontal cortex.
We have four lobes to our brain the occipital lobe is at the back of the brain, the temporal lobe is behind the ears, the parietal lobe is at the top of the brain and the frontal lobe is at the front of the brain. The prefrontal cortex is at the front of the frontal lobe. The prefrontal cortex is the second major brain area involved in processing reward and controlling addictive behaviour. This is the thinking part of the brain. This is the part of the brain that creates; the plan of action, sets goals, and makes sure that they are accomplished.
The third major brain region is the ventral segmental area, or VTA for short. This is in the mid brain, located at the top of your brain stem and is also the most primitive part of the brain, sometimes called the reptilian brain. This part of the brain influences the nucleus accumbens as well as the prefrontal cortex and therefore influences both pleasure and self- control. What has been found is that the VTA reflects reward prediction error. When the VTA neurones fire, it means that there has been a prediction error signalling a need for new learning and this new learning has been found to be extremely general, powerful, and effective.
When individuals have an addiction there are three major changes to the brain that contributes to the addiction. The first major change is that the pleasure response in the nucleus accumbens starts to become numb. This reflects the first behavioural symptom, tolerance. The numbing reflects the brains attempt to compensate for repeated over stimulation of the reward circuit. It inhibits the stimulation of the nucleus accumbens by numbing the pleasure response. Repeated over stimulation strengthens associations with addiction related cues, increase in cravings, weakening the inanition from the prefrontal cortex, undermining the ability to maintain self control.
The body has mechanisms that maintain an internal equilibrium called homeostasis. This means that if the nucleus accumbens is repeatedly over stimulated just like a volume control on your radio, it will turn down the stimulation that it is receiving, meaning that the person will feel less pleasure from ingesting sugar. The sugar high won’t be as rewarding, meaning that the person will have to eat more and more in order to get the same level of reward. Eventually the person will have to eat the same amount in order just to feel normal without the high.
This doesn’t just effect the stimulation from ingesting sugar, it will also effect all kinds of stimulation, everyday pleasures of seeing a friend, or doing an activity that you enjoy might also start to feel numb. This will result in the need to just continue to eat, and eat and eat, because it is the only way a person can feel good.
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