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Our memory is a tricky mechanism: What we remember are not instances that happened, rather past circumstances that are influenced, and changed, by how much the incident means to us. According to a new study led by psychologists at the University of Toronto, our feelings about the memory influences how we see it as well as how vividly we can recall it later.

Rebecca Todd, a postdoctoral fellow in U of T's Department of Psychology and lead author of the study published recently in the Journal of Neuroscience told UT press that she and her colleagues determined discovered that we see things that are emotionally arousing with greater vividness than those memories that have no emotional ties to us.

"Whether they're positive - for example, a first kiss, the birth of a child, winning an award - or negative, such as traumatic events, breakups, or a painful and humiliating childhood moment that we all carry with us, the effect is the same," says Todd.

Researchers report that the part of the brain responsible for tagging the level of emotional or motivational importance to things according to one's own past experience - the amygdala - is more active when looking at images that are rated as vivid. This increased activation in turn influences our visual perceptional of the object and integrates that with sensations from the body, causing a purely sensational response.

Researchers used a combination of emotionally arousing, negative (scenes of violence or mutilation, or sharks and snakes baring their teeth), positive (mostly mild erotica), and neutral scenes (such as people on an escalator), overlaid with varying degrees of visual noise-similar to the snow of anold or poorly tuned television screen--- to later asked them questions about the amount of noise they perceived on each and what they could recall, in detail about the pictures.

The experiments showed that were rated higher in emotionally enhanced vividness were remembered more vividly, regardless of the level of noise.

"We know now why people perceive emotional events so vividly - and thus how vividly they will remember them - and what regions of the brain are involved," says Todd. He adds that the study further shows that the subjectivity that underlines the experiment in that people view things differently "could be useful in predicting an individual's vulnerability to trauma, including intrusive memories experienced by people with post-traumatic stress disorder."