Brain oscillatory substrates of visual short-term memory capacity
Heise, Kirstin F.
Gruber, Walter R.
Karim, Ahmed A.
Hummel, Friedhelm C.
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Sauseng, Paul; Klimesch, Wolfgang; Heise, Kirstin F. Gruber, Walter R.; Holz, Elisa; Karim, Ahmed A.; Glennon, Mark; Gerloff, Christian; Birbaumer, Niels; Hummel, Friedhelm C. (2009). Brain oscillatory substrates of visual short-term memory capacity. Current Biology 19 (21), 1846-1852
The amount of information that can be stored in visual short-term memory is strictly limited to about four items . Therefore, memory capacity relies not only on the successful retention of relevant information but also on efficient suppression of distracting information, visual attention, and executive functions [2-5]. However, completely separable neural signatures for these memory capacity-limiting factors remain to be identified. Because of its functional diversity [6-9], oscillatory brain activity may off er a utile solution. In the present study, we show that capacity-determining mechanisms, namely retention of relevant information and suppression of distracting information, are based on neural substrates independent of each other: the successful maintenance of relevant material in short-term memory is associated with cross-frequency phase synchronization between theta (rhythmical neural activity around 5 Hz) and gamma (&gt;50 Hz) oscillations at posterior parietal recording sites. On the other hand, electroencephalographic alpha activity (around 10 Hz) predicts memory capacity based on efficient suppression of irrelevant information in short-term memory. Moreover, repetitive transcranial magnetic stimulation at alpha frequency can modulate short-term memory capacity by influencing the ability to suppress distracting information. Taken together, the current study provides evidence for a double dissociation of brain oscillatory correlates of visual short-term memory capacity.