Sunday, 8 July 2012

Neurotransmitter circuits

Neurotransmitters act as chemical messengers in the synapse between neurons, there exist neurotransmitter pathways that are clusters of neurons and projections that communicate using a particular neurotransmitter. Four motivationally relevant neurotransmitters are

  1.  Dopamine, generates good feelings of reward
  2.  Serotonin which influences mood and emotion, serotonin deficiency is associated with depression.
  3. Norepinephrine which regulates  arousal and alertness
  4. Endorphin which inhibits pain, anxiety and fear by generating positive affect.
For Dopamine the ventral tegmental area is associated with the "want" to do one course of action over another, generally with biologically significant  events. The ventral tegmental area releases dopamine into other brain areas such as the prefrontal cortex and the pattern of release is predictable in proportion to the events expected outcome and actual outcome (hippocampus). Dopamine release is greatest when rewarding events occurs in ways that are not expected, it facilitates the learning of an events motivational significance.

Hormones  such as cortisol are released in response to stress via the hypothalamus- pituary-andrenocortical physiological pathway due to social-evaluative threats.
Testosterone is associated with high sexual motivation.

Oxytocin is a hormone produced by the hypothalamus and is colloquially known as a bonding hormone,"tend and befriend" stress response that enhances  reponses associated with counsel, support and nurturance (Reeve 2009 : 67) . This makes it sound like a wonder molecule for prosocial behaviour, of course the reality is more complex.

Amusingly,  IO9 which occasionally tries to be funny like with "lists" did one on why oxytocin is such a great molecule  but also features another more balanced article. The hype surrounding oxytocin  began with a study by Kosfield & Heinrichs (2005) in which participants played games of trust while sniffing Oxytocin. In fact its influence is dependent greatly on the orientations of the individual and is one of many interactions.


Kosfeld, Michael: Heinrichs, Markus: Zak, Paul J: Fishchbacker, Urs & Fehr, Ernst. (2005). Oxytocin increases trust in humans. In the International Journal of Nature. (June 2005). Pages 673- 676.

Reeve, Johnmarshall. (2009) . Understanding Motivation and Emotion. (5th Edition). Published by John Wiley & Sons. Pages 62- 71.

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