Most humans, for example, think that they will live longer, stay healthier and be more successful than average, a mindset experts call "optimism bias".
But so far the exact location in the brain of neuronal activity related to feelings of optimism - and pessimism - have remained incomprehensible.
For the study, researchers used magnetic resonance imaging to observe the brains of 15 volunteers aged 18 to 36 while they were asked to think about specific future and past events such as "winning an award" or "the end of a romantic relationship".
The respondents were then asked to evaluate several aspects of their own reactions, including degree of arousal and vividness.
Analysis showed enhanced activity in two regions, the amygdala and the rostral anterior cingulate cortex, both of which are known to play a critical role in the subjective evaluation of emotions.
The team found that participants were more likely to expect positive events to happen closer in the future than negative events, and to imagine them with greater vividness.
"When participants imagined positive future events relative to negative ones, enhanced activation was detected in the rostral anterior cingulate and amygdala, which are the same brain areas that seem to malfunction in depression," Nature quoted lead author Tali Sharot, as saying.
"Activation of the rostral anterior cingulate was correlated with trait optimism, with more optimistic participants showing greater activity in this region when imagining future positive events," Sharot added.
NYU Professor Elizabeth Phelps said, "Our behavioral results suggest that while the past is constrained, the future is open to interpretation, allowing people to distance themselves from possible negative events and move closer toward positive ones."
"Understanding optimism is critical as optimism has been related to physical and mental health. On the other hand, a pessimistic view is correlated with severity of depression symptoms," she added.
According to the researchers, the study pulls together new and different parts of research on optimism and the brain.
The current findings are published in the most recent issue of Nature.