Enhanced attention-related alertness following right anterior insular cortex neurofeedback training.

The anterior insular cortex, a central node of the salience network, plays a critical role in cognitive control and attention. Here, we investigated the feasibility of enhancing attention using real-time fMRI neurofeedback training that targets the right anterior insular cortex (rAIC). 56 healthy adults underwent two neurofeedback training sessions. The experimental group received feedback from neural responses in the rAIC, while control groups received sham feedback from the primary visual cortex or no feedback. Cognitive functioning was evaluated before, immediately after, and three months post-training. Our results showed that only the rAIC neurofeedback group successfully increased activity in the rAIC. Furthermore, this group showed enhanced attention-related alertness up to three months after the training. Our findings provide evidence for the potential of rAIC neurofeedback as a viable approach for enhancing attention-related alertness, which could pave the way for non-invasive therapeutic strategies to address conditions characterized by attention deficits.

Shared neural mechanisms between imagined and perceived egocentric motion - A combined GVS and fMRI study.

Many cognitive and social processes involve mental simulations of a change in perspective. Behavioral studies suggest that such egocentric mental rotations rely on brain areas that are also involved in processing actual self-motion, thus depending on vestibular input. In a combined galvanic vestibular stimulation (GVS) and functional Magnetic Resonance Imaging (fMRI) study, we investigated the brain areas that underlie both simulated changes in self-location and the processing of vestibular stimulation within the same individuals. Participants performed an egocentric mental rotation task, an object-based mental rotation task, or a pure lateralization task during GVS or sham stimulation. At the neural level, we expected an overlap between brain areas activated during vestibular processing and egocentric mental rotation (against object-based mental rotation) within area OP2 and the Posterior Insular Cortex (PIC), two core brain regions involved in vestibular processing. The fMRI data showed a small overlap within area OP2 and a larger overlap within the PIC for both egocentric mental rotation against object-based mental rotation and vestibular processing. GVS did not influence the ability to perform egocentric mental rotation. Our results provide evidence for shared neural mechanisms underlying perceived and simulated self-motion. We conclude that mental rotation of one's body involves neural activity in the PIC and area OP2, but the behavioral results also suggest that those mental simulations of one's body might be robust to modulatory input from vestibular stimulation.

Canal-otolith interactions alter the perception of self-motion direction.

Few studies have investigated the perception of vestibular stimuli when they occur in sequences. Here, three experiments (ntotal = 33) are presented that focus on intravestibular motion sequences and the underlying perceptual decision-making process. Natural vestibular stimulation (yaw rotation or translation) was used to investigate the discrimination process of the direction of a subsequent spatially congruent or incongruent translation or rotation. The few existing studies focusing on unimodal motion sequences have uncovered self-motion aftereffects, similar to the visual motion aftereffect, possibly due to altered processing of sensory stimuli. An alternative hypothesis predicts a shift of spatial attention due to the cue motion influencing perception of the subsequent motion stimulus. The results show that participants systematically misjudged the direction of motion stimuli well above the detection threshold if the direction of the preceding cue motion stimulus was congruent with the direction of the target (a motion aftereffect). Hierarchical drift diffusion models were used to analyze the data. The results suggest that altered perceptual decision-making and the resulting misperceptions are likely to originate in altered processing of sensory vestibular information.

Tactile motion lacks momentum.

The displacement of the final position of a moving object in the direction of the observed motion path, i.e. an overestimation, is known as representational momentum. It has been described both in the visual and the auditory domain, and is suggested to be modality-independent. Here, we tested whether a representational momentum can also be demonstrated in the somatosensory domain. While the cognitive literature on representational momentum suggests that it can, previous work on the psychophysics of tactile motion perception would rather predict an underestimation of the perceived endpoint of a tactile stimulus. Tactile motion stimuli were applied on the left and the right dorsal forearms of 32 healthy participants, who were asked to indicate the subjectively perceived endpoint of the stimulation. Velocity, length and direction of the trajectory were varied. Contrary to the prediction based on the representational momentum literature, participants in our experiment significantly displaced the endpoint against the direction of movement (underestimation). The results are thus compatible with previous psychophysical findings on the perception of tactile motion. Further studies combining paradigms from classical psychophysics and cognitive psychology will be needed to resolve the apparently paradoxical predictions by the two literatures.

When less is more - Implicit preference for incomplete bodies in xenomelia.

Individuals with xenomelia identify with an amputated rather than with their physically complete, healthy body. They often mimic amputees and show a strong admiration of and sexual attraction towards them. Here we investigated for the first time empirically whether such unusual preference for amputated bodies is present also on an implicit level. Using the well-validated Implicit Association Test we show that individuals with xenomelia manifested a stronger implicit and explicit preference for amputated bodies than a normally-limbed control group and a group of involuntary amputees did. Interestingly, the two latter groups did not differ in their implicit and explicit preference for complete versus amputated bodies. These findings are an important step in understanding how deeply rooted attitudes about a socially normative body appearance may be influenced by a developmentally disordered experience of one's own bodily self. We conclude that this is the first behavioral evidence demonstrating a conflict of self-identification on an implicit level and this enriches current understandings of xenomelia as a primarily neurological disorder.

Arterial spin labeling imaging reveals widespread and Aß-independent reductions in cerebral blood flow in elderly apolipoprotein epsilon-4 carriers.

Changes in cerebral blood flow are an essential feature of Alzheimer's disease and have been linked to apolipoprotein E-genotype and cerebral amyloid-deposition. These factors could be interdependent or influence cerebral blood flow via different mechanisms. We examined apolipoprotein E-genotype, amyloid beta-deposition, and cerebral blood flow in amnestic mild cognitive impairment using pseudo-continuous arterial spin labeling MRI in 27 cognitively normal elderly and 16 amnestic mild cognitive impairment participants. Subjects underwent Pittsburgh Compound B (PiB) positron emission tomography and apolipoprotein E-genotyping. Global cerebral blood flow was lower in apolipoprotein E ɛ4-allele carriers (apolipoprotein E4+) than in apolipoprotein E4- across all subjects (including cognitively normal participants) and within the group of cognitively normal elderly. Global cerebral blood flow was lower in subjects with mild cognitive impairment compared with cognitively normal. Subjects with elevated cerebral amyloid-deposition (PiB+) showed a trend for lower global cerebral blood flow. Apolipoprotein E-status exerted the strongest effect on global cerebral blood flow. Regional analysis indicated that local cerebral blood flow reductions were more widespread for the contrasts apolipoprotein E4+ versus apolipoprotein E4- compared with the contrasts PiB+ versus PiB- or mild cognitive impairment versus cognitively normal. These findings suggest that apolipoprotein E-genotype exerts its impact on cerebral blood flow at least partly independently from amyloid beta-deposition, suggesting that apolipoprotein E also contributes to cerebral blood flow changes outside the context of Alzheimer's disease.

The Moving History of Vestibular Stimulation as a Therapeutic Intervention.

Although the discovery and understanding of the function of the vestibular system date back only to the 19th century, strategies that involve vestibular stimulation were used long before to calm, soothe and even cure people. While such stimulation was classically achieved with various motion devices, like Cox's chair or Hallaran's swing, the development of caloric and galvanic vestibular stimulation has opened up new possibilities in the 20th century. With the increasing knowledge and recognition of vestibular contributions to various perceptual, motor, cognitive, and emotional processes, vestibular stimulation has been suggested as a powerful and non-invasive treatment for a range of psychiatric, neurological and neurodevelopmental conditions. Yet, the therapeutic interventions were, and still are, often not hypothesis-driven as broader theories remain scarce and underlying neurophysiological mechanisms are often vague. We aim to critically review the literature on vestibular stimulation as a form of therapy in various selected disorders and present its successes, expectations, and drawbacks from a historical perspective.

Binding body and self in visuo-vestibular conflicts.

Maintenance of the bodily self relies on the accurate integration of multisensory inputs in which visuo-vestibular cue integration is thought to play an essential role. Here, we tested in healthy volunteers how conflicting visuo-vestibular bodily input might impact on body self-coherence in a full body illusion set-up. Natural passive vestibular stimulation was provided on a motion platform, while visual input was manipulated using virtual reality equipment. Explicit (questionnaire) and implicit (skin temperature) measures were employed to assess illusory self-identification with either a mannequin or a control object. Questionnaire results pointed to a relatively small illusion, but hand skin temperature, plausibly an index of illusory body ownership, showed the predicted drop specifically in the condition when participants saw the mannequin moving in congruence with them. We argue that this implicit measure was accessible to visuo-vestibular modulation of the sense of self, possibly mediated by shared neural processes in the insula involved in vestibular and interoceptive signalling, thermoregulation and multisensory integration.

Neural coupling of cooperative hand movements: a reflex and fMRI study.

The neural control of "cooperative" hand movements reflecting "opening a bottle" was explored in human subjects by electromyographic (EMG) and functional magnetic resonance imaging (fMRI) recordings. EMG responses to unilateral nonnoxious ulnar nerve stimulation were analyzed in the forearm muscles of both sides during dynamic movements against a torque applied by the right hand to a device which was compensated for by the left hand. For control, stimuli were applied while task was performed in a static/isometric mode and during bilateral synchronous pro-/supination movements. During the dynamic cooperative task, EMG responses to stimulations appeared in the right extensor and left flexor muscles, regardless of which side was stimulated. Under the control conditions, responses appeared only on the stimulated side. fMRI recordings showed a bilateral extra-activation and functional coupling of the secondary somatosensory cortex (S2) during the dynamic cooperative, but not during the control, tasks. This activation might reflect processing of shared cutaneous input during the cooperative task. Correspondingly, it is assumed that stimulation-induced unilateral volleys are processed in S2, leading to a release of EMG responses to both forearms. This indicates a task-specific neural coupling during cooperative hand movements, which has consequences for the rehabilitation of hand function in poststroke patients.