reprint available: OscillatorSTM model

[Ole Jensen]

The following reprint is available (PDF) at
  http://lucifer.ccs.brandeis.edu/~ojensen
or
  http://www.jneurosci.org/current.shtml


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AN OSCILLATORY SHORT-TERM MEMORY BUFFER MODEL CAN ACCOUNT FOR DATA ON THE
STERNBERG TASK

Ole Jensen and John E. Lisman 

Journal of Neuroscience, 18:10699-10699, 1998 

A limited number (7+/-2) of items can be held in human short-term memory
(STM). We have previously suggested that observed dual (theta and gamma) 
oscillations could underlie a multiplexing mechanism that enables a single
network to actively store up to 7 memories. Here we have asked whether
models of this kind can account for the data on the Sternberg task, the
most quantitative measurements of memory search available. We have found
several variants of the oscillatory search model that account for the
quantitative dependence of the reaction time distribution on the number of
items (S) held in STM. The models differ on the issues of 1) whether theta
frequency varies with S and 2) whether the phase of ongoing oscillations
is reset by the probe. Using these models the frequencies of dual
oscillations can be derived from psychophysical data. The derived values
(f_theta = 6-10 Hz, f_gamma = 45-60 Hz) are in reasonable agreement with
experimental values. The exhaustive nature of the serial search that has
been inferred from psychophysical measurements can be plausibly explained
by these oscillatory models. One argument against exhaustive serial search
has been the existence of serial position effects. We find that these
effects can be explained by short-term repetition priming in the context
of serial scanning models. Our results strengthen the case for serial
processing and point to experiments that discriminate between variants of
the serial scanning process.



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Ole Jensen, Ph.D.
Volen Center for Complex Systems
Brandeis University 
Waltham
MA02454-9110 
USA

Home phone:        (617) 666 8274  
Work phone:        (781) 736 3146   
Fax:               (781) 736 2398 
Phone in Denmark:  (+45) 59517316

jensen at volen.brandeis.edu
http://lucifer.ccs.brandeis.edu/~ojensen