Peggy Mason

Research Summary
After a 25-year focus on the cellular mechanisms of pain modulation (how does morphine work? and related questions), my laboratory’s energy is now focused on the biological basis of empathy and helping. Important questions include: Do rats help another in distress? Yes Who do they help? Strangers and familiars alike, as long as they know the type (strain) of rat What motivates rats to help another in distress? This is a work in progress but right now, it looks as though the motivation is a rodent version of empathy What are the brain circuits that support affective communication between two individuals? We are using a variety of methods to go into the brain and understand the circuits underlying pro-social behavior In addition to leading a research laboratory, I am committed to teaching neurobiology to anyone that will listen. As the first “neuroevangelist,” I tweet as @NeuroMOOC and blog at I am also thrilled to be able to teach neurobiology to the interested public through a massively open online course (MOOC) on Coursera ( My initial session of Understanding the Brain: The Neurobiology of Everyday Life was offered in 2014 and attracted more than 55,000 students; a second session will be starting up in early 2015. I welcome all to come join in the neuro-fun!
Biosciences Graduate Program Association
  1. Simmons DH, Titley HK, Hansel C, Mason P. Behavioral Tests for Mouse Models of Autism: An Argument for the Inclusion of Cerebellum-Controlled Motor Behaviors. Neuroscience. 2020 May 15. View in: PubMed

  2. Mason P, Shan H. A valence-free definition of sociality as any violation of inter-individual independence. Proc Biol Sci. 2017 Nov 15; 284(1866). View in: PubMed

  3. Umana IC, Daniele CA, Miller BA, Abburi C, Gallagher K, Brown MA, Mason P, McGehee DS. Nicotinic modulation of descending pain control circuitry. Pain. 2017 Oct; 158(10):1938-1950. View in: PubMed

  4. Ben-Ami Bartal I, Shan H, Molasky NM, Murray TM, Williams JZ, Decety J, Mason P. Anxiolytic Treatment Impairs Helping Behavior in Rats. Front Psychol. 2016; 7:850. View in: PubMed

  5. Mason P. With a little help from our friends: how the brain processes empathy. Cerebrum. 2014 Sep-Oct; 2014:14. View in: PubMed

  6. Ben-Ami Bartal I, Rodgers DA, Bernardez Sarria MS, Decety J, Mason P. Pro-social behavior in rats is modulated by social experience. Elife. 2014; 3:e01385. View in: PubMed

  7. Wang Q, Fong R, Mason P, Fox AP, Xie Z. Caffeine accelerates recovery from general anesthesia. J Neurophysiol. 2014 Mar; 111(6):1331-40. View in: PubMed

  8. Hellman KM, Mason P. Opioids disrupt pro-nociceptive modulation mediated by raphe magnus. J Neurosci. 2012 Oct 03; 32(40):13668-78. View in: PubMed

  9. Mason P. Two negatives make a positive: telencephalic-mediated analgesia. Exp Neurol. 2012 Aug; 236(2):336-8. View in: PubMed

  10. Mason P. Medullary circuits for nociceptive modulation. Curr Opin Neurobiol. 2012 Aug; 22(4):640-5. View in: PubMed

  11. Ben-Ami Bartal I, Decety J, Mason P. Empathy and pro-social behavior in rats. Science. 2011 Dec 09; 334(6061):1427-30. View in: PubMed

  12. Foo H, Mason P. Ingestion analgesia occurs when a bad taste turns good. Behav Neurosci. 2011 Dec; 125(6):956-61. View in: PubMed

  13. Mason P. From descending pain modulation to obesity via the medullary raphe. Pain. 2011 Mar; 152(3 Suppl):S20-4. View in: PubMed

  14. Foo H, Crabtree K, Mason P. The modulatory effects of rostral ventromedial medulla on air-puff evoked microarousals in rats. Behav Brain Res. 2010 Dec 20; 215(1):156-9. View in: PubMed

  15. Mason P, Bartal BA. How the social brain experiences empathy: Summary of a gathering. Soc Neurosci. 2010; 5(2):252-6. View in: PubMed

  16. Foo H, Mason P. Analgesia accompanying food consumption requires ingestion of hedonic foods. J Neurosci. 2009 Oct 14; 29(41):13053-62. View in: PubMed

  17. Hellman KM, Mendelson SJ, Mendez-Duarte MA, Russell JL, Mason P. Opioid microinjection into raphe magnus modulates cardiorespiratory function in mice and rats. Am J Physiol Regul Integr Comp Physiol. 2009 Nov; 297(5):R1400-8. View in: PubMed

  18. Mason P, Foo H. Food consumption inhibits pain-related behaviors. Ann N Y Acad Sci. 2009 Jul; 1170:399-402. View in: PubMed

  19. Foo H, Crabtree K, Thrasher A, Mason P. Eating is a protected behavior even in the face of persistent pain in male rats. Physiol Behav. 2009 Jun 22; 97(3-4):426-9. View in: PubMed

  20. Mason P. Chapter 15 Descending pain modulation as a component of homeostasis. Handb Clin Neurol. 2006; 81:211-8. View in: PubMed

  21. Frazier CR, Mason P, Zhuang X, Beeler JA. Sucrose exposure in early life alters adult motivation and weight gain. PLoS One. 2008 Sep 17; 3(9):e3221. View in: PubMed

  22. Hellman KM, Brink TS, Mason P. Activity of murine raphe magnus cells predicts tachypnea and on-going nociceptive responsiveness. J Neurophysiol. 2007 Dec; 98(6):3121-33. View in: PubMed

  23. Mason P, Gao K, Genzen JR. Serotonergic raphe magnus cell discharge reflects ongoing autonomic and respiratory activities. J Neurophysiol. 2007 Oct; 98(4):1919-27. View in: PubMed

  24. Mason P. Placing pain on the sensory map: classic papers by Ed Perl and colleagues. J Neurophysiol. 2007 Mar; 97(3):1871-3. View in: PubMed

  25. Brink TS, Hellman KM, Lambert AM, Mason P. Raphe magnus neurons help protect reactions to visceral pain from interruption by cutaneous pain. J Neurophysiol. 2006 Dec; 96(6):3423-32. View in: PubMed

  26. Nason MW, Mason P. Medullary raphe neurons facilitate brown adipose tissue activation. J Neurosci. 2006 Jan 25; 26(4):1190-8. View in: PubMed

  27. Foo H, Mason P. Sensory suppression during feeding. Proc Natl Acad Sci U S A. 2005 Nov 15; 102(46):16865-9. View in: PubMed

  28. Mason P. Ventromedial medulla: pain modulation and beyond. J Comp Neurol. 2005 Dec 05; 493(1):2-8. View in: PubMed

  29. Mason P. Deconstructing endogenous pain modulations. J Neurophysiol. 2005 Sep; 94(3):1659-63. View in: PubMed

  30. Baez MA, Brink TS, Mason P. Roles for pain modulatory cells during micturition and continence. J Neurosci. 2005 Jan 12; 25(2):384-94. View in: PubMed

  31. Foo H, Mason P. Movement-related discharge of ventromedial medullary neurons. J Neurophysiol. 2005 Feb; 93(2):873-83. View in: PubMed

  32. Brink TS, Mason P. Role for raphe magnus neuronal responses in the behavioral reactions to colorectal distension. J Neurophysiol. 2004 Oct; 92(4):2302-11. View in: PubMed

  33. Nason MW, Mason P. Modulation of sympathetic and somatomotor function by the ventromedial medulla. J Neurophysiol. 2004 Jul; 92(1):510-22. View in: PubMed

  34. Foo H, Mason P. Discharge of raphe magnus ON and OFF cells is predictive of the motor facilitation evoked by repeated laser stimulation. J Neurosci. 2003 Mar 01; 23(5):1933-40. View in: PubMed

  35. Foo H, Mason P. Brainstem modulation of pain during sleep and waking. Sleep Med Rev. 2003 Apr; 7(2):145-54. View in: PubMed

  36. Brink TS, Mason P. Raphe magnus neurons respond to noxious colorectal distension. J Neurophysiol. 2003 May; 89(5):2506-15. View in: PubMed

  37. Gao K, Mason P. Physiological and anatomic evidence for functional subclasses of serotonergic raphe magnus cells. J Comp Neurol. 2001 Oct 29; 439(4):426-39. View in: PubMed

  38. Mason P. Contributions of the medullary raphe and ventromedial reticular region to pain modulation and other homeostatic functions. Annu Rev Neurosci. 2001; 24:737-77. View in: PubMed

  39. Gao K, Mason P. The discharge of a subset of serotonergic raphe magnus cells is influenced by baroreceptor input. Brain Res. 2001 May 11; 900(2):306-13. View in: PubMed

  40. Mason P, Escobedo I, Burgin C, Bergan J, Lee JH, Last EJ, Holub AL. Nociceptive responsiveness during slow-wave sleep and waking in the rat. Sleep. 2001 Feb 01; 24(1):32-8. View in: PubMed

  41. Gao K, Mason P. Serotonergic Raphe magnus cells that respond to noxious tail heat are not ON or OFF cells. J Neurophysiol. 2000 Oct; 84(4):1719-25. View in: PubMed

  42. Mason P. Central mechanisms of pain modulation. Curr Opin Neurobiol. 1999 Aug; 9(4):436-41. View in: PubMed

  43. Leung CG, Mason P. Physiological properties of raphe magnus neurons during sleep and waking. J Neurophysiol. 1999 Feb; 81(2):584-95. View in: PubMed

  44. Leung CG, Mason P. Physiological survey of medullary raphe and magnocellular reticular neurons in the anesthetized rat. J Neurophysiol. 1998 Oct; 80(4):1630-46. View in: PubMed

  45. Gao K, Chen DO, Genzen JR, Mason P. Activation of serotonergic neurons in the raphe magnus is not necessary for morphine analgesia. J Neurosci. 1998 Mar 01; 18(5):1860-8. View in: PubMed

  46. Gao K, Mason P. Somatodendritic and axonal anatomy of intracellularly labeled serotonergic neurons in the rat medulla. J Comp Neurol. 1997 Dec 15; 389(2):309-28. View in: PubMed

  47. Kusmirek J, Owens CA, Mason P. Lumbar but not cervical intrathecal DAMGO suppresses extrasegmental nociception in awake rats. Brain Res. 1997 Sep 05; 767(2):375-9. View in: PubMed

  48. Gao K, Kim YH, Mason P. SEROTONERGIC pontomedullary neurons are not activated by antinociceptive stimulation in the periaqueductal gray. J Neurosci. 1997 May 01; 17(9):3285-92. View in: PubMed

  49. Mason P. Physiological identification of pontomedullary serotonergic neurons in the rat. J Neurophysiol. 1997 Mar; 77(3):1087-98. View in: PubMed

  50. Mason P, Leung CG. Physiological functions of pontomedullary raphe and medial reticular neurons. Prog Brain Res. 1996; 107:269-82. View in: PubMed

  51. Leung CG, Mason P. Spectral analysis of arterial blood pressure and raphe magnus neuronal activity in anesthetized rats. Am J Physiol. 1996 Aug; 271(2 Pt 2):R483-9. View in: PubMed

  52. Mason P, Owens CA, Hammond DL. Antagonism of the antinocifensive action of halothane by intrathecal administration of GABAA receptor antagonists. Anesthesiology. 1996 May; 84(5):1205-14. View in: PubMed

  53. Leung CG, Mason P. Effects of isoflurane concentration on the activity of pontomedullary raphe and medial reticular neurons in the rat. Brain Res. 1995 Nov 13; 699(1):71-82. View in: PubMed

  54. Mason P. Lipopolysaccharide induces fever and decreases tail flick latency in awake rats. Neurosci Lett. 1993 May 14; 154(1-2):134-6. View in: PubMed