**Author details**

*Neurostimulation and Neuromodulation in Contemporary Therapeutic Practice*

this area remains preliminary, but consistent with this hypothesis.

The effects of epilepsy on these higher order oscillatory structures suggest that neurostimulation could restore normal function by reversing these effects. Work in

Therapeutic approaches using neurostimulation for epilepsy primarily involve

DBS in epilepsy has been applied to a number of targets, including the thalamus (anterior and centromedian nuclei), cerebellum, and basal ganglia (subthalamic nucleus, caudate, substantia nigra pars reticulata). Via the brainstem and basal forebrain arousal systems, the thalamus is hypothesized to underpin consciousness through distributed mechanisms of arousal regulation. Of these, the anterior nucleus of the thalamus appears to underlie limbic seizures and to present in medically resistant seizure formation, whereas the centromedian nucleus of the thalamus is involved in the reticulothalamocortical system that is considered integral to the modulation of vigilance. Significantly, deep brain stimulation of the anterior nucleus of the thalamus has emerged as a promising therapy for drug resistant epilepsy, with recent findings indicating a key mechanistic role for brain oscillations. A study by Chang, for example, showed that desynchronization of the ipsilateral hippocampal background electrical activity over a broad frequency range influenced epileptic discharges, including interictal spikes and high-frequency oscillations [29]. Furthermore, high-frequency stimulation of the anterior nucleus of the thalamus appeared to decouple large-scale neural activity between the hip-

Singer's discovery in the 1990s of patterned electrical activity for brain communication provided the conceptual basis for moving beyond temporal sequencing for encoded representations [30]. It also overcame the most significant theoretical limitation of Hubel and Wiesel's abstraction thesis for coding, which had been premised on their discovery of motion and edge detector cells in the occipital cortex. The use of rhythmic, typically oscillatory, activity for communication and the ordering of cognition has since been confirmed in a wide variety of studies. This understanding

vagal nerve stimulation (VNS), although other techniques such as deep brain stimulation and repetitive transcranial magnetic stimulation (rTMS) have seen limited use. Existing studies suggest that neurostimulation influences mechanisms of consciousness, which are altered during epilepsy [28]. For afferent vagal nerve fibers, the brainstem nucleus of the solitary tract (NST) is the main relay station. This nucleus has widespread projections to numerous areas in the forebrain, brainstem, thalamus, and areas involved in learning and memory formation (amygdala, hippocampus). Additionally, learning, memory encoding and recall are known to be modulated by arousal, an integral feature of consciousness. Consistent with the observations on the effect of epilepsy on memory consolidation, animal models of vagal nerve stimulation showed that it positively influenced hippocampal longterm potentiation (HLP). In humans, for instance, a chronic increased alertness is observed in VNS-implanted subjects with acute effects on memory consolidation.

**4.1 Neurostimulation treatments**

*4.1.1 Vagal nerve stimulation*

*4.1.2 DBS*

pocampus and regionally distant cortical areas.

**5. Summary and conclusion**

**12**

Denis Larrivee1,2

1 Loyola University Chicago, USA

2 Mind and Brain Institute, University of Navarra Medical School, Spain

\*Address all correspondence to: sallar1@aol.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
