Task dependence of human theta: The case for multiple cognitive functions

The recent finding of task-related theta oscillations in humans (M.J. Kahana, Sekuler, Caplan, Kirschen, Madsen, Nature 399 (1999) 781-784) raises a number of questions. We recorded from 345 intracranial electrodes in five patients with medically intractable epilepsy while they learned to navigate virtual mazes. Previously, we showed significant dependence of theta on two different task parameters, maze difficulty and study versus test modes. First, we show that these results hold for an additional 174 electrodes and two subjects, removing a previous confound between the two comparisons. Here we ask whether or not these two task parameters reflect some common, or correlated, task-correlates of theta. (C) 2000 Elsevier Science B.V. All rights reserved.