Effects of electrical brain stimulation on brain indices and presence experience in immersive, interactive virtual reality

The subjective presence experience in virtual reality (VR) is associated with distinct brain activation patterns. Particularly, the dorsolateral prefrontal cortex (DLPFC) seems to play a central role. We investigated the effects of electric brain stimulation (transcranial direct current, tDCS) on the presence experience as well as on brain activity and connectivity. Thirty-eight participants received either anodal (N = 18) or cathodal (N = 20) stimulation of the DLPFC before interacting in an immersive VR as well as sham stimulation. During VR interaction, EEG and heart rate were recorded. After VR interaction, participants rated their subjective presence experience using standardized questionnaires. Cathodal stimulation led to stronger brain connectivity than sham stimulation. Increased brain connectivity was associated with numerically lower levels of subjective presence. Anodal stimulation did not lead to changes in brain connectivity, and no differences in subjective presence ratings were found between the anodal and sham stimulation. These results indicate that cathodal tDCS over the DLPFC leads to a more synchronized brain state, which might hamper the activity in networks, which are generally associated with the evolvement of the subjective presence experience. Our results underline the importance of the DLPFC for the presence experience in VR.

Active Imagination as an Alternative to Lucid Dreaming: Theory and Experimental Results

Lucid dreaming (LD) is a fun and interesting activity, but most participants have difficulties in attaining lucidity, retaining it during the dream, concentrating on the needed task and remembering the results. This motivates to search for a new way to enhance lucid dreaming via different induction techniques, including chemicals and electric brain stimulation. However, results are still unstable. An alternative approach is to reach the lucid dreaming-like states via altered state of consciousness not related to dreaming. Several methods such as guided visualization, internal dialog, creative writing, hypnosis, hypnagogia, daydreaming, DMT trips, voice dialog, shamanic journey, rebirthing, and “forcing” tulpas can help in attaining such states. One of the most promising of them is Jungian “active imagination” (AIM) technique, which allows unconscious content to build up inside some mental frames. This article explores the hypothesis of replacing lucid dreaming research with active imagination, and the conditions and ways to accomplish it. Method: An open label pilot experiment was performed in 2004-2005 in Moscow, Russia with 100 participants. Results: The results show that there are two groups of people: ones with “visual imagination screen” and others have “mental imagination screen”. AIM works perfectly as a replacement for lucid dreams only for the first group of people. For the second group, it created interesting content, but not visual or emotional intensity equal to enter lucid dreaming like state. No known instruments helped to move the person from one group to another. The first group consisted of young females, while the second mostly contained males with rational and mathematical type of personality. Conclusion: AIM partly works as a replacement for LD, as it works great only for half of people, and it requires a sitter. However, AIM outperforms LD in reliability and availability in any circumstance: it could be performed even by text chat or in a crowd. It is also better than LD in retaining concentration on topic and the easiness of memorizing the results (which could be recorded). Self-performed AIM is less effective. AIM can be improved by intelligent chat bots as sitters and weak brain stimulation that can increase the probability of attaining something like hypnogogic state.

Head models of healthy and depressed adults for simulating the electric fields of non-invasive electric brain stimulation

During the past decade, it became clear that the electric field elicited by non-invasive brain stimulation (NIBS) techniques such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are substantially influenced by variations in individual head and brain anatomy. In addition to structural variations in the healthy, several psychiatric disorders are characterized by anatomical alterations that are likely to further constrain the intracerebral effects of NIBS. Here, we present high-resolution realistic head models derived from structural magnetic resonance imaging data of 19 healthy adults and 19 patients diagnosed with major depressive disorder (MDD). By using a freely available software package for modelling the electric fields induced by different NIBS protocols, we show that our head models are well-suited for assessing inter-individual and between-group variability in the magnitude and focality of tDCS-induced electric fields for two protocols targeting the left dorsolateral prefrontal cortex.

Head models of healthy and depressed adults for simulating the electric fields of non-invasive electric brain stimulation

During the past decade, it became clear that the electric field elicited by non-invasive brain stimulation (NIBS) techniques such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are substantially influenced by variations in individual head and brain anatomy. In addition to structural variations in the healthy, several psychiatric disorders are characterized by anatomical alterations that are likely to further constrain the intracerebral effects of NIBS. Here, we present high-resolution realistic head models derived from structural magnetic resonance imaging data of 19 healthy adults and 19 patients diagnosed with major depressive disorder (MDD). By using a freely available software package for modelling the electric fields induced by different NIBS protocols, we show that our head models are well-suited for assessing inter-individual and between-group variability in the magnitude and focality of tDCS-induced electric fields for two protocols targeting the left dorsolateral prefrontal cortex.

A tribute to Jose M.R. Delgado (1915–2011): The pioneer of electric brain-stimulation

IntroductionJosé Manuel Rodriguez Delgado (1915–2011), a Spanish physiologist, was among the first scientist to perform electric brain stimulation in both animals and humans. His work on brain-stimulation research during the 1960s and 1970s was innovative but also controversial.ObjectivesTo present the scientific papers of Jose Delgado on psychosurgery.AimsTo review available literature and to show evidence that Jose Delgado made a significant contribution to the development of psychosurgery.MethodsA biography and private papers are presented and discussed followed by a literature review.ResultsDelgado showed that with electrical brain stimulation one could evoke well-organized complex behavior in primates. A rhesus monkey was stimulated with an electrode implanted inside the red nucleus, followed by a complex sequence of events. After stimulation of an area three millimeters from the red nucleus, the rhesus monkey just yawned. Delgado also investigated the mechanisms of aggressive behavior in other animals. Stimulation of the caudate nucleus by remote control in a fighting bully resulted in sudden paralysis. In some human patients suffering from depression, euphoria was induced after stimulation of the septum.ConclusionDelgado pioneered the brain electrode implantation in order to electrically stimulate specific brain areas for treatment epilepsy and of different types of mental illness. He was severely criticized. His studies, however, paved the way for new modulation techniques such as the development of deep brain stimulation.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Direct cortical stimulation of human posteromedial cortex

Background:The posteromedial cortex (PMC) is a collective term for an anatomically heterogeneous area of the brain constituting a core node of the human default mode network (DMN), which is engaged during internally focused subjective cognition such as autobiographical memory.Methods:We explored the effects of causal perturbations of PMC with direct electric brain stimulation (EBS) during presurgical epilepsy monitoring with intracranial EEG electrodes.Results:Data were collected from 885 stimulations in 25 patients implanted with intracranial electrodes across the PMC. While EBS of regions immediately dorsal or ventral to the PMC reliably produced somatomotor or visual effects, respectively, we found no observable behavioral or subjectively reported effects when sites within the boundaries of PMC were electrically perturbed. In each patient, null effects of PMC stimulation were observed for sites in which intracranial recordings had clearly demonstrated electrophysiologic responses during autobiographical recall.Conclusions:Direct electric modulation of the human PMC produced null effects when standard functional mapping methods were used. More sophisticated stimulation paradigms (e.g., EBS during experimental cognitive tests) will be required for testing the causal contribution of PMC to human cognition and subjective experience. Nonetheless, our findings suggest that some extant theories of PMC and DMN contribution to human awareness and subjective conscious states require cautious re-examination.