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Affective neuroscience is the study of the neural mechanisms of emotion. This interdisciplinary field combines neuroscience with the psychological study of personality, emotion, and mood.[1]

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Emotions are thought to be related to activity in brain areas that direct our attention, motivate our behavior, and determine the significance of what is going on around us. Pioneering work by Paul Broca (1878),[2] James Papez (1937),[3] and Paul D. MacLean (1952)[4] suggested that emotion is related to a group of structures in the center of the brain called the limbic system, which includes the hypothalamus, amygdala, hippocampi, and other structures. Research has shown that limbic structures are directly related to emotion, but other non-limbic structures have also been found to have emotional relevance. The following brain structures are currently thought to be involved in emotion:[5]

Main Structures of the Limbic System

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  • Amygdala — The amygdalae are two small, round structures located anterior to the hippocampi near the temporal poles. The amygdalae are involved in detecting and learning what parts of our surroundings are important and have emotional significance. They are critical for the production of emotion, and may be particularly so for negative emotions, especially fear.[6] Multiple studies have shown amygdala activation when perceiving a potential threat, various circuits allow the amygdala to use related past memories to better judge the possible threat. [7] A study done by Whalen in 1998 hoped to investigate amygdala activation when viewing emotional stimuli without being aware of it. To do this they masked fearful and happy facial images with a neutral face. The results showed an isolated activation in the amygdala. This finding is a substantial because in other past studies using unmasked facial expressions at least four other brain regions also activated when preforming the task.[8]
  • Thalamus- The thalamus is involved in sensory perception and regulation of motor function. It is thought to play a role in processing visual stimuli. Pessoa argues that the primary role of pulvinar (found within the thalamus) is to coordinate the function of different networks during the evaluation of the affective visual stimuli. [9]
  • Hypothalamus- The hypothalamus is located below the thalamus. It plays a role in emotional responses by synthesizing and releasing neurotransmitters which can effect mood, reward and arousal. [10]
  • Hippocampus - The hippocampus is a structure of the medial temporal lobes that is mainly involved in memory. It works to form new memories and also connecting different senses such as visual input, smell or sound to memories. The hippocampus allows memories to be stored long term and also retrieves them when necessary. It is this retrieval that is used within the amygdala to help evaluate current affective stimulus.[11]
  • Fornix The fornix is the main output pathway from the hippocampus to the mammillary bodies. It has been identified as a main region in controlling spatial memory functions, episodic memory and executive functions.[12]
  • Mammillary body - Mammillary body plays an important role in memory processes particularly in delayed recall tasks and memory using spatial locations. The results of an experiment run by Satin using two separate groups of rats; one with mammillary body lesions and one healthy rats showed that damage to the mammillary body impairs spatial working memory which is the ability for the animal to remember a place they have already been. [13]
  • Olfactory bulbs- Olfactory bulbs are the first cranial nerves, located on the ventral side of the frontal lobe. Sensory information (smell) is transferred to the olfactory cortex where it is relayed through the medial-dorsal nucleus of the thalamus to the orbitofrontal cortex.
  • Cingulate gyrus- Sometime considered to be part of the limbic system, located above the corpus callosum It receives input from the thalamus. The cingulate gyrus is involved in emotion formation as well as memory and learning.
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  • Basal ganglia -Basal ganglia are groups of neuclei found on either side of the thalamus. Basal ganglia play an important role in recognizing facial emotion. Cheung looked at stroke victims that had damage to either the basal ganglia or the thalamus. She found that participants with this damage to these areas were able to recognize happiness but struggled with emotions such as anger, disgust and fear.[14]
  • Orbitofrontal cortex - Is a major structure involved in decision making and the influence by emotion on that decision. Researchers believe the outcome of a decision is based on possible future outcomes and weighing the risk to benefit of consequences for a particular action.[15]
  • Prefrontal cortex — The term prefrontal cortex refers to the very front of the brain, behind the forehead and above the eyes. It appears to play a critical role in the regulation of emotion and behavior by anticipating the consequences of our actions. The prefrontal cortex may play an important role in delayed gratification by maintaining emotions over time and organizing behavior toward specific goals.[16]
  • Anterior cingulate — The anterior cingulate cortex (ACC) is located in the middle of the brain, just behind the prefrontal cortex. The ACC is thought to play a central role in attention, and may be particularly important with regard to conscious, subjective emotional awareness. This region of the brain may also play an important role in the initiation of motivated behavior.
  • Ventral striatum — The ventral striatum is a group of subcortical structures thought to play an important role in emotion and behavior. One part of the ventral striatum called the nucleus accumbens is thought to be involved in the experience of goal-directed positive emotion. Individuals with addictions experience increased activity in this area when they encounter the object of their addiction.
  • Insula — The insular cortex is thought to play a critical role in the bodily experience of emotion, as it is connected to other brain structures that regulate the body’s autonomic functions (heart rate, breathing, digestion, etc.). This region also processes taste information and is thought to play an important role in experiencing the emotion of disgust.
  • Cerebellum - Recently, there has been a considerable amount of work that describes the role of the cerebellum in emotion as well as cognition, and a "Cerebellar Cognitive Affective Syndrome" has been described.[17] Both neuroimaging studies as well as studies following pathological lesions in the cerebellum (such as a stroke) demonstrate that the cerebellum has a significant role in emotional regulation. Lesion studies[18] have shown that cerebellar dysfunction can attenuate the experience of positive emotions. While these same studies do not show an attenuated response to frightening stimuli, the stimuli did not recruit structures that normally would be activated (such as the amydala). Rather, alternative limbic structures were activated, such as the ventromedial prefrontal cortex, the anterior cingulate gyrus, and the insula. This may indicate that evolutionary pressure resulted in the development of the cerebellum as a redundant fear-mediating circuit to enhance survival. It may also indicate a regulatory role for the cerebellum in the neural response to rewarding stimuli, such as money,[19] drugs of abuse,[20] and orgasm.[21]


references

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  1. ^ Panksepp J (1990). "A role for "affective neuroscience" in understanding stress: the case of separation distress circuitry". In Puglisi-Allegra S, Oliverio A (ed.). Psychobiology of Stress. Dordrecht, Netherlands: Kluwer Academic. pp. 41–58. ISBN 0-7923-0682-1.
  2. ^ Broca, P. (1878). Anatomie comparée des circonvolutions cérébrales: le grand lobe limbique. Rev. Anthropol., 1, 385-498.
  3. ^ Papez J.W. (1937). A proposed mechanism of emotion. 1937. J Neuropsychiatry Clin Neurosci., 7, 103-12.
  4. ^ Maclean, P.D. (1952). Psychiatric implications of physiological studies on frontotemporal portion of limbic system (visceral brain). Electroencephalogr Clin Neurophysiol Suppl., 4, 407-18.
  5. ^ Dalgleish, T. (2004). The emotional brain. Nature Reviews Neuroscience, 5, 583-9.
  6. ^ Ledoux, J.E, (1995). Emotion: clues from the brain. Annual Review of Psychology, 46, 209-35.
  7. ^ Breiter, Hans (November 1996). "Response and Habituation of the Human Amygdala during Visual Processing of Facial Expression". Neuron. 17 (5): 875–887. doi:10.1016/S0896-6273(00)80219-6. PMID 8938120. S2CID 17284478. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link)
  8. ^ Whalen, Paul (January 1998). "Masked presentations of emotional facial expressions modulate amygdala activity without explicit knowledge". The Journal of Neuroscience. 1. 18 (1): 411–418. doi:10.1523/JNEUROSCI.18-01-00411.1998. PMC 6793390. PMID 9412517. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link)
  9. ^ Pessoa, Luiz (November 2010). "Emotion Processing and the amygdala: from a 'low road' to 'many roads' of evaluating biological significance". Nature Review Neuroscience. 11 (11): 773–783. doi:10.1038/nrn2920. PMC 3025529. PMID 20959860. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link)
  10. ^ Cao, Bei-Bei (october 2012). "Cerebellar fastigal nuclear GABAergic projections to hypothalamus modulate immune function". Brain Behavior and Immunity. 27. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link)
  11. ^ Fischer, Hakan (2002). "Brain habituation during repeated exposure o fearful and neutral faces: a functional MRI study". Brain Research Bulletin. 59. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  12. ^ Modi, Shilpi (2012). "Individual differences in trait anxiety are associated with white matter tract integrity in fornix and uncinate fascicles: Preliminary evidence from a DTI based tractography study". Behavioural Brain Research. 238: 188–192. doi:10.1016/j.bbr.2012.10.007. PMID 23085341. S2CID 1741104. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  13. ^ Satin, L.J. (1999). "Effects of mammillary body lesions on spatial reference and working memory tasks". Behavioural Brain Research. 102 (1–2): 137–150. doi:10.1016/S0166-4328(99)00011-X. PMID 10403022. S2CID 4048952. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  14. ^ Cheung, Crystal (2006). "The differential effects of thalamus and basal ganglia on facial emotion recognition". Brain and Cognition. 61 (3): 262–268. doi:10.1016/j.bandc.2006.01.008. PMID 16540222. S2CID 39092069. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  15. ^ Bechara, Antoine (2000). "Emotion, Decision Making and the Orbitofrontal Cortex". Oxford Journals. 10 (3): 295-307. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ^ Davidson, R.J., & Sutton, S.K. (1995). Affective neuroscience: The emergence of a discipline. Current Opinion in Neurobiology, 5, 217-224.
  17. ^ Parvizi, Anderson, Damasio & Damasio, (2001). Pathological laughing and crying: a link to the cerebellum. Brain, Sep;124(Pt 9):1708-19.
  18. ^ Turner, Paradiso, Marvel, Pierson, Boles Ponto, Hichwa, Robinson (2007). Neuropsychologia 2007 March 25; 45(6): 1331–1341
  19. ^ Martin-Solch C, Magyar S, Kunig G, Missimer J, Schultz W, Leenders KL. Changes in brain activation associated with reward processing in smokers and nonsmokers. A positron emission tomography study. Experimental Brain Research (2001) 139(3):278–286
  20. ^ Sell LA, Morris J, Bearn J, Frackowiak RS, Friston KJ, Dolan RJ. Activation of reward circuitry in human opiate addicts. European Journal of Neuroscience (1999) 11(3):1042–1048
  21. ^ Holstege G, Georgiadis JR, Paans AM, Meiners LC, van der Graaf FH, Reinders AA. Brain activation during human male ejaculation. Journal of Neuroscience (2003) 23(27):9185–9193
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