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Non-invasive long-term recordings of cortical ‘direct current’ (DC–) activity in humans using magnetoencephalography

✍ Scribed by Bruno-Marcel Mackert; Gerd Wübbeler; Martin Burghoff; Peter Marx; Lutz Trahms; Gabriel Curio

Book ID
117478034
Publisher
Elsevier Science
Year
1999
Tongue
English
Weight
102 KB
Volume
273
Category
Article
ISSN
0304-3940

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Theta bandwidth determines human visual
Theta bandwidth determines human visual working memory capacity Human visual short term memory (VSTM) is capacity limited1. The neurophysiological basis for this limitation is, however, currently unknown. Here we apply the principle of efficient information transfer, derived from communications theory, to provide a mechanistic account of VSTM capacity. Shannon's information theory states that to increase the capacity of information encoded along a frequency axis, it is more efficient to expand the bandwidth than to increase the transmitted power for a given level of noise2. By applying Shannon's principles to human magnetoencephalography (MEG) recordings of oscillatory activity in the theta band during a VSTM task, we demonstrate that increasing memory load to capacity induces a parametric shift in theta frequency band during the delay period, from 4 to 8 Hz, in a right fronto-parietal network. Critically, we show that an individual's VSTM capacity is proportional to that parametric shift. Thus, the adherence of cortical neuronal oscillations to a fundamental principle of efficient information transfer appears to underlie the limited nature of visual representation in short-term memory.
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