I'll discuss two research studies which strongly infer that, yes, it is indeed possible to activate "peace circuits" within the brain and stablize them through consistent mental practice.

In their scholarly paper, "Making a life worth living: Neural correlates of wellbeing," Heather Urry and colleagues discuss their research findings on the particular neural firing patterns that mediate a profound sense of wellbeing, which they define as "eudaimonic wellbeing." According to neuroscientist Daniel J. Siegel, eudaimonic wellbeing "is more about a sense of equanimity than about the sensory pleasure focus of hedonia [i.e., pleasure through external stimulation]. A eudaimonic form of well-being embraces the psychological qualities of autonomy, mastery of the environment, positive relationships, personal growth, self-acceptance, and meaning and purpose in life." The higher levels of such wellbeing are intimately associated with profound peace and joy, and are less dependent upon outer surroundings and more dependent upon an individual's perceptions, interpretations, and inner way of being in the world.

The specific neural correlates of eudaimonic wellbeing - greater activity in the left prefrontal lobe, also define the basic neural shift that takes place with consistent practice of most forms of meditation. Numerous studies have highlighted meditation's tendency to catalyze this left prefrontal shift, activating the brain sites most highly correlated with higher levels of meaning, purpose, peace, and compassion.

A scholarly paper by Antoine Lutz and company, "Long-term meditators self-induce high-amplitude gamma synchrony during mental practice," demonstrates this observation well.

Eight Tibetan Buddhists with a range of 15 - 40 years of prior training were examined during meditation. A control group of 10 student volunteers also participated. The two groups practiced Metta meditation, a "non-referential state of loving kindness and compassion."

Several interesting observations became apparent:

 

• There was more gamma band activity during relaxed states amongBuddhist practitioners.
  
  
• 5 to 15 seconds after the meditation began, all meditators exhibitedextraordinarily high degrees of synchronized gamma activity. 
   
• The more hours each practitioner had practiced during prior years, the higher was their absolute gamma activity.
   
• Long-distance synchronizations were evident between the frontal and parietal leads. Long-term practitioners exhibited the highest degree of these synchronization effects.
   
• Two areas of the brain that were significantly active during meditation were the caudate and putamen, whixh indicates the  formation of higher-level habits.
   
• Significant gamma band activity increased in the left middle frontal gyrus, which is correlated with positive  emotions such as happiness, enthusiasm, and joy, as well as feelings of high energy and alertness.
   
• One Buddhist practitioner's gamma activity, in particular, was the highest ever recorded in history.

First, it's important to understand that gamma activity, which is between 30 Hz and 80 Hz (or cycles per second), is associated with higher than average levels of sensory unification, the kind associated with intense "aha" moments. In fact, Dr. Richard Davidson, one of the principle investigators, theorizes that these monks live in a perpetual "aha" moment, continuously experiencing life in richer, more meaningful, multi-faceted ways.

Secondly, much of this increased activity was taking place in the left prefrontal lobe, which indicates that the specific brain sites correlated with higher levels of wellbeing were being systematically activated and developed through willed mental training. In effect, these results strongly infer that our basic emotional disposition, contrary to popular belief, can in fact be transformed to reflect greater peace, poise, and equanimity. Another way to express this idea is, "Temporal states become permanent traits." In other words, these temporary higher states of consciousness, when evoked consistently on a daily basis, are eventually integrated into the brain's neural firing patterns as permanent traits.