What if neurologists were able to excavate the human mind for a complete history of past experiences? Although it may sound like something out of science fiction, new advances in neurology have placed it within the realm of possibility, according to research conducted at the Weizmann Institute of Science.

The research, published in The Journal of Neuroscience, focused on the puzzling phenomenon of spontaneously emerging brain activity during periods of rest. Unlike its owner, the brain is never inactive — and as soon as the daily onslaught of outside stimuli ceases, nerve cell activity associated with incoming information is immediately replaced by a series of different, ultra-slow sequences of neuronal activity. The wave patterns in which they result exhibit a hieroglyphic blend of unintelligibility and clear-cut symmetry.

Determined to crack the code, research student Tal Harmelech hypothesized that spontaneously emerging brain activity during periods of rest could be understood as imprints of past experiences — wave patterns resurfacing from a fragmented “cache” of neuronal activity. Due to the tremendously flexible structure of the brain, certain information is isolated and embedded within connections between brain cells. This feature is referred to as “plasticity,” and gradually allows the brain to anticipate certain key properties of experiences, even entirely new ones. The study theorized that for this reason, information about earlier stimuli would inevitably be partially incorporated in intercellular links, and subsequently manifest as spontaneous wave patterns.

The researchers conducted a series of tests where patients were asked to imagine a situation requiring rapid decision-making. Later, it was shown that subsequent fMRI scans indeed corresponded to the activity recorded during the test, with traces lingering for at least 24 hours.

Beyond providing an invaluable “mapping tool” when outlining an individual’s recent cognitive history, the discovery may also allow for a new method of personality profiling. The unique patterns of spontaneous brain activity could eventually reveal each individual’s habits, talents and biases.

"Today, we are discovering more and more of the common principles of brain activity, but we have not been able to account for the differences between individuals," said Dr. Rafi Malach. "In the future, spontaneous brain patterns could be the key to obtaining unbiased individual profiles."

Source: Harmelech T, Preminger S, Wertman E, Malach R. The Day-After Effect: Long Term, Hebbian-Like Restructuring of Resting-State fMRI Patterns Induced by a Single Epoch of Cortical Activation. The Journal of Neuroscience. 2013.