What is the neurological basis for 'daredevil' behaviour? What is the neurological basis for people being seemingly fearless and engaging in risk-taking and daredevil behaviour?

I am talking about those that frequently perform or participate in activities that are often described by a lot of people as reckless and life-threateningly dangerous.
Dopamine receptor agonists related to reckless driving and gambling

There are three case reports provided by Reactions Weekly (2010) demonstrating correlations between treatment with dopamine receptor agonists and reckless driving:


  Reckless driving occurred in three patients during treatment with
  dopamine receptor agonists (DA) ... DA are associated with impulse
  control disorders, and may alter how the brain perceives and avoids
  risk. DA-associated impulse control disorders include pathological
  gambling and hypersexuality. Reckless driving may be another
  manifestation of DA-associated impulse control disorders.


Some further evidence is provided to suggest neurological correlates between dopamine receptor agonist and risky choices in a gambling task (Riba et al., 2008):


  In summary, the present findings indicate that the dopamine D2/D3
  receptor agonist pramipexole is capable of blocking reward-related
  activations in the rostral basal ganglia and midbrain and may lead to
  a behavioral disinhibition characterized by increases in risky choices
  in a gambling task.


Neurological correlates between voluntary and involuntary risk taking in the brain

A study used functional magnetic resonance imaging (fMRI) and administered a modified BART with an active choice mode and a passive no-choice mode in order to examine the neural correlates of voluntary and involuntary risk taking in the human brain (Rao et al., 2008):


  In summary, the present study modiﬁed the BART in both active and
  passive modes for use during fMRI and the ﬁndings provide direct
  visualization of voluntary and involuntary risk processing in the
  human brain. Regardless of the involvement of voluntary decision
  making, risk in this task is processed in visual pathway regions in
  the occipital and parietal lobes. However, during active
  decision-making, risk is associated with additional robust activation
  in dopamine rich mesolimbic (VTA-striatum) and frontal regions
  (insula, ACC/MFC, and DLPFC). Voluntary decision making per se, is
  associated with activation in the right DLPFC, which is absent in the
  involuntary no-choice condition. These results contribute to
  understanding the neural basis of normal and high risk behavior.
  Extending this paradigm to pathological populations characterized by
  impaired decisionmaking, such as patients with drug addition and
  compulsive gambling, may allow the speciﬁc neural components of
  impaired risk behavior to be distinguished, and may ultimately inform
  more effective clinical treatment interventions.


References


Reactions Weekly. (2010). Dopamine receptor agonists: reckless
driving: 3 case reports.(Adverse Reaction Case Reports)(Case
study)(Brief article), 1300, 18(1)
Riba, J., Kramer, U.M., Heldmann, M., Richter, S. &amp; Munte, T.F. (2008). Dopamine agonist increases risk taking but blunts reward-related brain activity. PLoS One, 3(6)
Rao, H. Korczykowski, M., Pluta, J., Hoang, A. &amp; Detre, J.A. (2008). Neural correlates of voluntary and involuntary risk taking in the human brain: An fMRI study of the Balloon Analog Risk Task (BART). Neuroimage, 42, 902-910