Systematic review maps real-time fMRI neurofeedback of the insula

A systematic review published in Nature examines the accumulating literature on real-time functional MRI (rt-fMRI) neurofeedback directed at the insula — the deep cortical structure the neuroanatomical literature has long called the "Island of Reil."

The review, titled "Self-navigating the 'Island of Reil': a systematic review of real-time fMRI neurofeedback training of insula activity," consolidates studies in which participants view a dynamic representation of their own blood-oxygen-level-dependent (BOLD) signal from the insula while attempting to modulate it. The modality here matters: this is not scalp EEG neurofeedback, the kind familiar from quantitative EEG labs and connectivity suites. It is real-time fMRI, in which the hemodynamic response of a targeted region — or of a distributed network anchored in that region — is fed back to the subject within seconds of acquisition, allowing volitional control training that EEG cannot reach, given the insula's depth and its proximity to structures that generate noise in surface recordings.

The insula sits at the intersection of interoception, emotional processing, pain perception, and autonomic regulation. That anatomical position explains why researchers have aimed rt-fMRI training at it: if participants can learn to up-regulate or down-regulate insular activity, the reasoning goes, the technique could serve as an adjunctive intervention in conditions where interoceptive and emotional circuits are implicated. The review's framing — "self-navigating" — captures the core mechanism: the participant, not the experimenter, discovers the mental strategy that moves the feedback signal, whether by attending to bodily sensations, imagery, or emotional recall.

For clinical neurophysiologists and EEG readers, the significance is twofold. First, the paper contributes to the growing evidence base that regionally specific self-regulation of brain activity is trainable in humans — a claim that neurofeedback research in general, whether EEG-based or fMRI-based, has had to defend against skepticism about non-specific effects and expectancy. A systematic review of this kind exists precisely to weigh that evidence across studies rather than rely on single-lab demonstrations. Second, it clarifies the division of labor between modalities. Where scalp EEG neurofeedback targets rhythmic activity measurable at the surface — sensorimotor rhythm, alpha, theta/beta ratios — rt-fMRI targets deep, hemodynamically defined activity in structures like the insula that standard montages cannot resolve. Readers who field referrals for "neurofeedback" should note that these are distinct techniques with distinct evidence bases, and that rt-fMRI neurofeedback remains an investigational research tool rather than a clinically deployed, regulator-cleared therapy.

The insula target itself deserves the reader's attention. sometimes called the "Island of Reil," the structure is buried in the lateral sulcus, covered by frontal, parietal, and temporal opercula. Its anterior portion integrates interoceptive and affective signals; its posterior portion maps somatosensory and pain inputs. Intracranial EEG work in presurgical epilepsy populations has shown that insular seizures can masquerade as temporal or frontal onset — a well-known diagnostic trap — which makes any non-invasive window onto insular function of interest to the epilepsy reading room as well as to the neurofeedback lab.

What the review offers, above all, is consolidation. Individual rt-fMRI studies of insula training have appeared across psychiatry, pain, and addiction journals for more than a decade, with heterogeneous targets, feedback schedules, and control conditions. By pooling and appraising that literature systematically, the authors provide a reference point for what has actually been demonstrated: which cohorts have been trained, what regulation effects have been reported, and where methodological gaps remain. Claims about clinical benefit should be kept to what the underlying studies showed, and this review exists partly to enforce exactly that discipline.

Looking forward, the paper positions rt-fMRI insula neurofeedback as a maturing research line whose next steps depend on controlled trials, standardized feedback protocols, and convergent validation — including, potentially, combined fMRI-EEG approaches that would let the field link deep hemodynamic regulation to the rhythmic signatures an EEG lab can monitor. For now, the "Island of Reil" has a map, and it is made of systematic evidence rather than single-study enthusiasm.