Our amazing brains allow us to do incredible things, yet they remain mysterious in many ways. Researchers have discovered some situations in which the brain can be “fooled”, and these insights into the brain’s inner workings have led to some exciting new technologies, including virtual reality (VR). In addition to its well-known role in gaming and entertainment, VR has some amazing uses in the field of medicine. VR can help patients manage pain, and it can also help surgeons practice delicate procedures and guide them during operations. Other advances called brain-machine interfaces can listen to the brain’s chatter and translate thoughts into commands for computers or even robotic limbs, which could greatly improve the lives of people with certain disabilities. In this article, we will explain how researchers are using findings from cutting-edge brain research to produce exciting new technologies that can heal or even enhance the brain’s functions.

Functional connectivity patterns in the human brain, like the friction ridges of a fingerprint, can uniquely identify individuals. Does this "brain fingerprint" remain distinct even during Alzheimer's disease (AD)? Using fMRI data from healthy and pathologically ageing subjects, we find that individual functional connectivity profiles remain unique and highly heterogeneous during mild cognitive impairment and AD. However, the patterns that make individuals identifiable change with disease progression, revealing a reconfiguration of the brain fingerprint. Notably, connectivity shifts towards functional system connections in AD and lower-order cognitive functions in early disease stages. These findings emphasize the importance of focusing on individual variability rather than group differences in AD studies. Individual functional connectomes could be instrumental in creating personalized models of AD progression, predicting disease course, and optimizing treatments, paving the way for personalized medicine in AD management.

Background: Deficits in self are commonly described through different neuro-pathologies, based on clinical evaluations and experimental paradigms. However, currently available approaches lack appropriate clinical validation, making objective evaluation and discrimination of self-related deficits challenging. Methods: We applied a statistical standardized method to assess the clinical discriminatory capacity of a Self-Other Voice Discrimination (SOVD) task. This task, validated experimentally as a marker for self-related deficits, was administered to 17 patients eligible for neurosurgery due to focal hemispheric brain tumors or epileptic lesions. Results: The clinical discriminatory capacity of the SOVD task was evident in three patients who exhibited impairments for self-voice perception that could not be predicted by other neuropsychological deficits. Impairments in other-voice perception were linked to inhibitory neuropsychological deficits, suggesting a potential association with executive deficits in voice recognition. Conclusions: This exploratory study highlights the clinical discriminatory potential of the SOVD task and suggests that it could complement the standard neuropsychological assessment, paving the way for enhanced diagnoses and tailored treatments for self-related deficits.

Hallucinations can occur in the healthy population, are clinically relevant and frequent symptoms in many neuropsychiatric conditions, and have been shown to mark disease progression in patients with neurodegenerative disorders where antipsychotic treatment remains challenging. Here, we combine MR-robotics capable of inducing a clinically-relevant hallucination, with real-time fMRI neurofeedback (fMRI-NF) to train healthy individuals to up-regulate a fronto-parietal brain network associated with the robotically-induced hallucination. Over three days, participants learned to modulate occurrences of and transition probabilities to this network, leading to heightened sensitivity to induced hallucinations after training. Moreover, participants who became sensitive and succeeded in fMRI-NF training, showed sustained and specific neural changes after training, characterized by increased hallucination network occurrences during induction and decreased hallucination network occurrences during a matched control condition. These data demonstrate that fMRI-NF modulates specific hallucination network dynamics and highlights the potential of fMRI-NF as a novel antipsychotic treatment in neurodegenerative disorders and schizophrenia. fMRI-neurofeedback targeting a hallucination-related whole-brain network allows individuals to willfully control its temporal properties and modify proneness the hallucination induction, showing promise for investigating future therapies in disease.

One's own voice is one of the most important and most frequently heard voices. Although it is the sound we associate most with ourselves, it is perceived as strange when played back in a recording. One of the main reasons is the lack of bone conduction that is inevitably present when hearing one's own voice while speaking. The resulting discrepancy between experimental and natural self-voice stimuli has significantly impeded self-voice research, rendering it one of the least investigated aspects of self-consciousness. Accordingly, factors that contribute to self-voice perception remain largely unknown. In a series of three studies, we rectified this ecological discrepancy by augmenting experimental self-voice stimuli with bone-conducted vibrotactile stimulation that is present during natural self-voice perception. Combining voice morphing with psychophysics, we demonstrate that specifically self-other but not familiar-other voice discrimination improved for stimuli presented using bone as compared with air conduction. Furthermore, our data outline independent contributions of familiarity and acoustic processing to separating the own from another's voice: although vocal differences increased general voice discrimination, self-voices were more confused with familiar than unfamiliar voices, regardless of their acoustic similarity. Collectively, our findings show that concomitant vibrotactile stimulation improves auditory self-identification, thereby portraying self-voice as a fundamentally multi-modal construct.

The intriguing experience that somebody is nearby when no one is actually present and cannot be seen or heard has been reported in many different contexts and has been referred to as the sense of presence, feeling of a presence, invisible presences, or presence hallucination (PH) (James, 1902; Critchley, 1979). PHs are often vivid experiences, have a clear location in space—with people frequently turning around to search for the invisible presence—and some even offering it a chair or food (Jaspers, 1913; Nightingale, 1982). PHs are a common theme in fiction, having been alluded to in the literature of divinity, occultism, and parapsychology (Green and McCreery, 1975; Critchley, 1979) and studied in history and anthropology (Solomonova et al., 2011; Wyatt et al., 2016). Following reports of PHs in extrememountaineering (Smythe, 1935; Messner, 2003), long-distance solo-biking (Davie, 2013), solo-sailing (Suedfeld and Mocellin, 1987) and in shipwreck survivors (Critchley, 1943), PHs have also been investigated in psychology and medicine (Critchley, 1979; Brugger et al., 1996; Arzy et al., 2006). Initially described in psychiatry (Jaspers, 1913; Llorca et al., 2016), PHs have more recently been mostly investigated in neurological patients with epilepsy, stroke, neoplasia, and Parkinson’s disease (PD) (Brugger et al., 1996; Fénelon et al., 2011). However, despite its intriguing experiential characteristics and the broad academic and clinical interest, scientific studies and experimental data on PHs continue to be sparse. This is likely due to difficulties in investigating a spontaneously occurring phenomenon, the absence of experimental procedures able to induce PHs reliably in real time, and to their occurrence in the large majority of cases in situations not prone to empirical investigations (far from laboratories). Here we provide an overview of recent investigations in clinical neuroscience on PH and in neuroscience using methods to induce PH experimentally, linking them to altered self-monitoring and sensorimotor processing. We analyze selected spiritual-religious experiences associated with PH and propose a new extended account of PH, by integrating and extending the altered self-monitoring account with the prominent agent detection theory in spiritual-religious experiences (Guthrie, 1989; Barrett and Lanman, 2008). We conclude by proposing that the mechanism and the controlled induction of invisible presences will likely have an impact in clinical and fundamental neurosciences and may provide a powerful experimental approach in biological anthropology and the cognitive science of religion.

A fundamental scientific question concerns the neuronal basis of perceptual consciousness, which encompasses the perceptual experience and reflexive monitoring associated with a sensory event. Although recent human studies identified individual neurons reflecting stimulus visibility, their functional role for perceptual consciousness remains unknown. Here, we provide neuronal and computational evidence indicating that perceptual and reflexive consciousness are governed by an all-or-none process involving accumulation of perceptual evidence. We recorded single-neuron activity in a participant with a microelectrode implant in the posterior parietal cortex, considered a substrate for evidence accumulation, while he detected vibrotactile stimuli around detection threshold and provided confidence estimates. We found that detected stimuli elicited firing rate patterns resembling evidence accumulation during decision-making, irrespective of response effectors. Similar neurons encoded the intensity of task-irrelevant stimuli, suggesting their role for consciousness per se, irrespective of report. We generalized these findings in healthy volunteers using electroencephalography and reproduced their behavioral and neural responses with a computational model. This model considered stimulus detection if accumulated evidence reached a bound, and confidence as the distance between maximal evidence and that bound. Applying this mechanism to our neuronal data, we were able to decode single-trial confidence ratings both for detected and undetected stimuli. Our results show that the specific gradual changes in neuronal dynamics during evidence accumulation govern perceptual consciousness and reflexive monitoring in humans.

Psychosis is often depicted as a disruption of the self-model. Patients suffering from psychosis report many symptoms relating to deficiencies in the minimal self, including loss of the sense of control over their actions (Sense of Agency) as well as numerous disturbances of body representation (e.g. Body Ownership). Positive symptoms of psychosis such as passivity symptoms and auditory hallucinations (termed first-rank symptoms) are characterized by a diminished demarcation of self-other boundaries, causing misattribution of self-generated actions to external sources. It has been suggested that this deficiency in self-monitoring in schizophrenia is due to abnormal sensorimotor prediction mechanisms, causing a loss of agency for actions and thoughts. While the neurobiological underpinnings of schizophrenia are yet unclear, many studies have reported aberrant neural connectivity in schizophrenia patients which may impact sensorimotor prediction and integration. Recently, we have shown that introducing sensorimotor conflict (SMC) can induce psychosis like symptoms in healthy patients. Employing a master-slave robotic system we induced a conflict by introducing a delay between the participants’ movements and the haptic feedback. The SMC caused a feeling of a Presence (FoP) which is a first rank symptom of psychosis. The FoP is also found in neurological patients with lesions in cortical regions of the temporoparietal cortex, insular cortex and fronto-parietal cortex related to abnormal bodily self-representation. Here, we tested if SMC may cause misattribution of auditory stimuli and if this is related to neural connectivity. We tested first episode psychosis patients (N=31) with and without first rank symptoms (related to the sense of control over actions and thoughts) as well as healthy participants (N=20) on an auditory attribution task while inducing conflict with the master-slave robot. We found that when a SMC was introduced patients with first rank symptoms showed a decrease in their ability to judge if the auditory stimuli were in their own voice or the voice of another person. Resting state functional connectivity analysis indicated that the first rank patients had reduced connectivity in the network related to the SMC, but not in other control regions. Furthermore, the reduced functional connectivity correlated with the rates of auditory misattribution. Our results show that induction of SMC can cause auditory misattributions, and that this is related to reduced cortical communication in regions related to sensorimotor body representation. These findings connect two influential theories of psychosis linking cognitive theories of sensorimotor prediction error in schizophrenia with systems level theories of neural disconnectivity. Understanding these neurocognitive mechanisms underlying the disruption of the self-model in psychosis may allow novel approaches in early diagnosis and treatment of these conditions.

Schneiderian first rank symptoms (FRS) are characterized by a diminished demarcation of self-other boundaries, causing misattribution of self-generated thoughts and actions to external sources. We have shown that introducing sensorimotor prediction error (SPE) by a robotic device in healthy subjects can induce a Feeling of a Presence (FoP) which is related to the FRS (Blanke et al. 2014). Here, we tested if SPE may induce auditory misattribution in psychotic patients and if this is related to neural connectivity in the temporoparietal cortex, insular cortex and fronto-parietal cortex (FoP Network).