Transcranial slow oscillation stimulation during sleep enhances memory consolidation in rats

Brain Stimul. 2014 Jul-Aug;7(4):508-15. doi: 10.1016/j.brs.2014.03.001. Epub 2014 Mar 12.

Abstract

Background: The importance of slow-wave sleep (SWS), hallmarked by the occurrence of sleep slow oscillations (SO), for the consolidation of hippocampus-dependent memories has been shown in numerous studies. Previously, the application of transcranial direct current stimulation, oscillating at the frequency of endogenous slow oscillations, during SWS enhanced memory consolidation for a hippocampus dependent task in humans suggesting a causal role of slowly oscillating electric fields for sleep dependent memory consolidation.

Objective: Here, we aimed to replicate and extend these findings to a rodent model.

Methods: Slow oscillatory direct transcranial current stimulation (SO-tDCS) was applied over the frontal cortex of rats during non-rapid eye movement (NREM) sleep and its effects on memory consolidation in the one-trial object-place recognition task were examined. A retention interval of 24 h was used to investigate the effects of SO-tDCS on long-term memory.

Results: Animals' preference for the displaced object was significantly greater than chance only when animals received SO-tDCS. EEG spectral power indicated a trend toward a transient enhancement of endogenous SO activity in the SO-tDCS condition.

Conclusions: These results support the hypothesis that slowly oscillating electric fields causal affect sleep dependent memory consolidation, and demonstrate that oscillatory tDCS can be a valuable tool to investigate the function of endogenous cortical network activity.

Keywords: EEG; Memory consolidation; Sleep; Slow oscillation stimulation; tDCS.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Frontal Lobe / physiology
  • Hippocampus / physiology
  • Male
  • Memory, Long-Term / physiology*
  • Models, Animal
  • Rats
  • Rats, Long-Evans
  • Sleep / physiology*
  • Time Factors
  • Transcranial Direct Current Stimulation / methods*