Memory Modulation by Weak Synchronous Deep Brain Stimulation: A Pilot Study

doi:10.1016/j.brs.2012.08.001

Brain Stimulation

Volume 6, Issue 3, May 2013, Pages 270-273

https://doi.org/10.1016/j.brs.2012.08.001 Get rights and content

Abstract

Zero-lag phase synchronization of EEG activity has been reported to be a central mechanism accompanying long-term memory formation. In this pilot study, we examined the effects of synchronous low-amplitude stimulation of the rhinal cortex and the hippocampus in eleven temporal lobe epilepsy patients. The impact of in-phase stimulation (zero lag) on long-term memory encoding of words was contrasted with anti-phase (180° phase lag) and sham stimulation. We hypothesized more correctly remembered words for the in-phase compared to the sham condition and fewer correctly remembered words for the anti-phase vs. the sham condition. Indeed, we observed a trend for a linear condition effect for correctly remembered words, which is in accordance to our prediction (in-phase > sham > anti-phase). This finding suggests that even weak synchronous deep brain stimulation of rhinal cortex and hippocampus may modulate memory performance, while clear evidence for an enhancement of memory by this kind of deep brain simulation is still lacking.

Section snippets

Patients

Eleven temporal lobe epilepsy patients (five female, mean age: 37 ± 9 years, all right handed) undergoing presurgical evaluation participated in the study. These patients were implanted because the seizure onset zone could not be defined unequivocally by non-invasive means. In none of the patients seizures occurred within 24 h before or after the experiment. The study was approved by the Ethics Committee of the University of Bonn and all patients gave written informed consent. The first six

Side effects of deep brain stimulation

None of the patients and none of the experimenters noticed an effect of stimulation or could distinguish the active stimulation conditions from the sham condition. Besides the expected markers of hippocampus sclerosis, histological examination of the resected hippocampi did not reveal any signs related to the impact of electrical currents. Furthermore, no effects of the different stimulation conditions on the back-counting task were observed, i.e. during all three experimental conditions

Conclusion

Up to now, very few studies have addressed the potentiality of memory improvement by deep brain stimulation [6], [7]. Recently, Suthana et al. [8] reported that stimulation of the entorhinal cortex during learning of destinations within virtual environments enhanced memory for this kind of spatial information.

In the present pilot study, weak deep brain stimulation was applied in epilepsy patients to the non-pathological, as well as pathological side. In the latter case stimulation was always on

Acknowledgements

The authors like to thank Christian Bien and Matthias Dümpelmann for helpful comments and suggestions concerning the stimulus protocol, as well as Albert Becker for histological examination of the resected hippocampi.

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: The study was supported by the Deutsche Forschungsgemeinschaft (Transregional Collaborative Research Centre SFB/TR 3, project A9).

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Deep Brain Stimulation (DBS)Short CommunicationMemory Modulation by Weak Synchronous Deep Brain Stimulation: A Pilot Study

Abstract

Section snippets

Patients

Side effects of deep brain stimulation

Conclusion

Acknowledgements

Curr Opin Neurobiol

Trends Cogn Sci

Neuron

The role of phase synchronization in memory processes

Nat Rev Neurosci

Human memory formation is accompanied by rhinal–hippocampal coupling and decoupling

Nat Neurosci

Gamma-band synchronization in the macaque hippocampus and memory formation

J Neurosci

Memory enhancement induced by hypothalamic/fornix deep brain stimulation

Ann Neurol

A phase I trial of deep brain stimulation of memory circuits in Alzheimer's disease

Ann Neurol

Memory enhancement and deep-brain stimulation of the entorhinal area

N Eng J Med

Deep Brain Stimulation (DBS)
Short Communication
Memory Modulation by Weak Synchronous Deep Brain Stimulation: A Pilot Study