S.M., sometimes referred to as SM-046, is an American woman with a peculiar type of brain damage that physiologically reduces her ability to feel fear. First described by scientists in 1994,[1] she has had exclusive and complete bilateral amygdala destruction since late childhood as a consequence of Urbach–Wiethe disease. Dubbed by the media as the "woman with no fear",[2] S.M. has been studied extensively in scientific research; she has helped researchers elucidate the function of the amygdala.[3]

Characteristics

An experiment with S.M. revealed no fear in response to exposure and handling of snakes and spiders (including tarantulas), a walk through a haunted attraction (Waverly Hills Sanatorium, specifically), or fear-inducing film clips (e.g., The Blair Witch Project, The Shining, and The Silence of the Lambs), instead only interest, curiosity, and excitement, though she expressed emotions appropriate to the film content such as happiness and disgust when viewing non-fear-inducing film clips.[3] Research has revealed that S.M. is not immune to all fear, however; along with other patients with bilateral amygdala damage, she was found to experience fear and panic attacks of greater intensity than the neurologically healthy controls in response to simulation of the subjective experience of suffocation via carbon dioxide inhalation, feelings which she and the others described as completely novel to them.[4]

Positive emotions

S.M. is described as very outgoing, extremely friendly, and uninhibited, as well as "somewhat coquettish" (playfully flirtatious) and having an abnormally high desire and tendency to approach others.[5] She is greatly impaired in recognizing negative social cues, such as being incapable of recognizing fear in the facial expressions of other people[1] and having difficulty judging trustworthiness and approachability in the faces of others.[5][6] These traits are consistent with the fact that she tends to quite indiscriminately approach and engage in physical contact with others.[6] In addition, S.M. appears to experience relatively little negative emotion,[3] whilst simultaneously experiencing a relatively high degree of positive affect, despite great adversity in her life.[5] Accordingly, she tends to be very positive about most people, situations, and issues.[5]

Music

S.M. exhibits impairments in the emotional processing of music; specifically, she shows selectively impaired recognition of sad and scary music.[7]

Danger appraisal

In addition to her lack of fear, S.M. shows a lack of a sense of personal space, and experiences virtually no discomfort standing extremely close to strangers, even nose-to-nose with direct eye contact. She does understand the concept of personal space, however, and acknowledges that other people need more personal space than she does.[8]

S.M. has been the victim of numerous acts of crime and traumatic and life-threatening encounters. She has been held up at both knifepoint and gunpoint, was almost killed in a domestic violence incident, and has received explicit death threats on multiple occasions. Despite the life-threatening nature of many of these situations, S.M. did not exhibit any signs of desperation, urgency, or other behavioral responses that would normally accompany such incidents. The disproportionate number of traumatic events in S.M.'s life has been attributed to a combination of her living in a dangerous area filled with poverty, crime, and to a marked impairment on her part of detecting looming threats in her environment and learning to steer clear of potentially dangerous situations. S.M. herself has never been convicted of a crime.[3][9]

Memory differences

S.M. shows memory differences. Emotionally arousing stimuli are known to undergo an enhancement of consolidation into long-term declarative memory (see emotion and memory), and this effect appears to be dependent on the amygdala.[10][11] In accordance, S.M. displays impaired declarative memory facilitation for emotional material, while her memory consolidation for neutral material is normal.[12][13]

Empathy

S.M. is still capable of being empathic to others despite being less capable of detecting negative emotion from faces; however, her threshold for noticing another person's pain was described as "fairly high".[5]

Personal life

S.M. is white[14] and was born in 1965.[15] She has been married and is a mother of three boys.[3][16]

S.M. has had a history of adversity in her life, including alienation, hardship, teasing, shunning and abuse from authority figures.[5]

See also

References

  1. ^ a b Adolphs R, Tranel D, Damasio H, Damasio A (1994). "Impaired recognition of emotion in facial expressions following bilateral damage to the human amygdala" (PDF). Nature. 372 (6507): 669–72. Bibcode:1994Natur.372..669A. doi:10.1038/372669a0. PMID 7990957. S2CID 25169376. Archived from the original (PDF) on 2016-03-03.
  2. ^ Suzzan Babcock (2014-11-25). In Search of Peace: For the Children. Author House. pp. 359–. ISBN 978-1-4969-5336-0.
  3. ^ a b c d e Feinstein, Justin S.; Adolphs, Ralph; Damasio, Antonio; Tranel, Daniel (2011). "The Human Amygdala and the Induction and Experience of Fear". Current Biology. 21 (1): 34–38. doi:10.1016/j.cub.2010.11.042. ISSN 0960-9822. PMC 3030206. PMID 21167712.
  4. ^ Feinstein, Justin S; Buzza, Colin; Hurlemann, Rene; Follmer, Robin L; Dahdaleh, Nader S; Coryell, William H; Welsh, Michael J; Tranel, Daniel; Wemmie, John A (2013). "Fear and panic in humans with bilateral amygdala damage". Nature Neuroscience. 16 (3): 270–272. doi:10.1038/nn.3323. ISSN 1097-6256. PMC 3739474. PMID 23377128.
  5. ^ a b c d e f Tranel D, Gullickson G, Koch M, Adolphs R (2006). "Altered experience of emotion following bilateral amygdala damage" (PDF). Cogn Neuropsychiatry. 11 (3): 219–32. doi:10.1080/13546800444000281. PMID 17354069. S2CID 40421089. Archived from the original (PDF) on 2015-01-19.
  6. ^ a b Adolphs R, Tranel D, Damasio AR (1998). "The human amygdala in social judgment" (PDF). Nature. 393 (6684): 470–4. Bibcode:1998Natur.393..470A. doi:10.1038/30982. PMID 9624002. S2CID 205000950. Archived from the original (PDF) on 2015-08-13.
  7. ^ Gosselin, Nathalie; Peretz, Isabelle; Johnsen, Erica; Adolphs, Ralph (2007). "Amygdala damage impairs emotion recognition from music". Neuropsychologia. 45 (2): 236–244. doi:10.1016/j.neuropsychologia.2006.07.012. ISSN 0028-3932. PMID 16970965. S2CID 14537793.
  8. ^ Kennedy, Daniel P; Gläscher, Jan; Tyszka, J Michael; Adolphs, Ralph (2009). "Personal space regulation by the human amygdala". Nature Neuroscience. 12 (10): 1226–1227. doi:10.1038/nn.2381. ISSN 1097-6256. PMC 2753689. PMID 19718035.
  9. ^ Terburg, D; Morgan, B E; Montoya, E R; Hooge, I T; Thornton, H B; Hariri, A R; Panksepp, J; Stein, D J; van Honk, J (2012). "Hypervigilance for fear after basolateral amygdala damage in humans". Translational Psychiatry. 2 (5): e115. doi:10.1038/tp.2012.46. ISSN 2158-3188. PMC 3365265. PMID 22832959.
  10. ^ Anderson, Adam K.; Phelps, Elizabeth A. (2001). "Lesions of the human amygdala impair enhanced perception of emotionally salient events". Nature. 411 (6835): 305–309. Bibcode:2001Natur.411..305A. doi:10.1038/35077083. ISSN 0028-0836. PMID 11357132. S2CID 4391340.
  11. ^ Strange, B. A.; Hurlemann, R.; Dolan, R. J. (2003). "An emotion-induced retrograde amnesia in humans is amygdala- and -adrenergic-dependent". Proceedings of the National Academy of Sciences. 100 (23): 13626–13631. doi:10.1073/pnas.1635116100. ISSN 0027-8424. PMC 263864. PMID 14595032.
  12. ^ Adolphs, R; Cahill, L; Schul, R; Babinsky, R (1997). "Impaired declarative memory for emotional material following bilateral amygdala damage in humans". Learning & Memory. 4 (3): 291–300. doi:10.1101/lm.4.3.291. ISSN 1072-0502. PMID 10456070.
  13. ^ Adolphs, R. (2000). "Impaired Emotional Declarative Memory Following Unilateral Amygdala Damage". Learning & Memory. 7 (3): 180–186. doi:10.1101/lm.7.3.180. ISSN 1072-0502. PMC 311327. PMID 10837507.
  14. ^ Amaral et al. (2016), p. 17: "For many years, S. M. attended a church where she was the only white person in a crowd of all black people."
  15. ^ Amaral et al. (2016):
    p. 2: "in 2015 she celebrated her 50th birthday."
    p. 3-4: "On November 7, 1986, Dr. Daniel Tranel met S. M. for the very first time when a neurologist referred her to the Benton Neuropsychology Clinic at the University of Iowa. She was 20 years old [...]"
  16. ^ Amaral DG, Corbett BA (2003). "The amygdala, autism and anxiety". Autism: Neural Basis and Treatment Possibilities. Novartis Found Symp. Vol. 251. pp. 177–87, discussion 187–97, 281–97. doi:10.1002/0470869380.ch11. ISBN 9780470850992. PMID 14521193.

Bibliography

David G. Amaral; Ralph Adolphs, eds. (2016). Living without an Amygdala. Guilford Publications. ISBN 9781462525959.

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