Theta oscillations index human hippocampal activation during a working memory task
AUTOR(ES)
Tesche, C. D.
FONTE
The National Academy of Sciences
RESUMO
Working memory (WM) is the ability to retain and associate information over brief time intervals. Functional imaging studies demonstrate that WM is mediated by a distributed network including frontal and posterior cortices, hippocampus, and cerebellum. In rodents, the presentation of stimuli in a WM task is followed by a reset of the phase of hippocampal theta. In this paper we report the observation of a similar phenomenon in normal human subjects. Neuromagnetic responses were recorded during presentation of a set of digits and a subsequent probe of the retained items. All stimuli were presented with a fixed temporal pattern. We observed phase reset of ≈7 Hz theta in left hippocampus ≈120 ms after probe stimuli, whereas reset of theta in right hippocampus was visible ≈80 ms prior to these anticipated stimuli. The duration of stimulus-locked theta increased with memory load, with a limiting value of ≈600 ms for 5–7 retained items. We suggest that, as in rats, stimulus-locked theta may index involvement of human hippocampal networks in the cognitive processing of sensory input. The anticipatory phase reset of theta indicates involvement of hippocampus in right hemisphere and cerebellar timing networks. Hippocampal structures are essential for orientation to perturbations in the sensory scene, a function that requires use of a context established by a constellation of stimuli. We suggest that the initiation and maintenance of stimulus-locked hippocampal theta observed here may facilitate processing of potentially salient and/or novel input with respect to a context established by the contents of WM.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=15431Documentos Relacionados
- Reset of human neocortical oscillations during a working memory task
- Functional magnetic resonance imaging of human prefrontal cortex activation during a spatial working memory task.
- Effect of nicotine on brain activation during performance of a working memory task
- Learners' processes during pre-task planning and Working Memory Capacity
- Cholinergic stimulation alters performance and task-specific regional cerebral blood flow during working memory