Our capacity for short-term memory depends on the synchronization of two types of brainwaves – rapid cycles of electrical activation – says a new study.
When the patterns of theta waves (4-7 Hz) and gamma waves (25-50 Hz) are closely synchronized, pieces of verbal information seem to be “written” into our short-term memory. But it also turns out that longer theta cycles help us remember more bits of information, while longer gamma cycles are correlated with lower recall.
These patterns are measured using electroencephalography (EEG), a lab technique with a long and successful history. Back in the 1950s, it helped scientists unravel the distinct brainwave patterns associated with REM (rapid-eye movement) and deep sleep. More recently, it’s been used to help people with disabilities control computers, and it’s even helped home users get an up-close look at their own brain activity.
Though more modern techniques like fMRI and DTI are much better at mapping tiny activity patterns deep within the brain, EEG remains a useful tool for measuring the overall patterns of synchronized electrical activity that sweep across the entire brain in various wave-like patterns – hence the term “brainwaves.”
Several types of brainwaves have been well studied since the 1950s: alpha waves, which are correlated with active attention; beta and delta waves, which are associated with logical processing; theta waves, which are associated with meditation and acceptance; and gamma waves, which burst rapidly across the brain when we come to a realization or an understanding.
And now, as the International Journal of Psychophysiology reports, a team led by Jan Kamiński at the Polish Academy of Sciences has discovered a new way of mapping relationships between these patterns of wave activity, to arrive at a new understanding of how theta and gamma waves work together: they studied the lengths of these two cycles relative to one another - and what they found was pretty amazing:
We have observed that the longer the theta cycles, the more information ‘bites’ the subject was able to remember; the longer the gamma cycle, the less the subject remembered.
The researchers discovered this in a very straightforward way – they simply kept tabs on volunteers’ EEG activity as they sat with eyes closed and let their minds wander; then they compared these recordings against ones taken as the volunteers memorized longer and longer strings of numbers - from three digits up to nine.
The correlation between long theta cycles and greater memory for digits turned out to be quite strong – and for gamma waves, the reverse turned out to be true. This means that gamma waves are probably much more crucial for forming ideas than they are for rote memorization.
Though this finding might not seem all that revolutionary, it provides an elegant demonstration of how even older technologies like EEG can still be used to help us make brand-new discoveries. Which means that in the brains of those of us who keep pluggin’ away at home EEG experiments, there’s probably still a place of honor for those wonderful little gamma waves.