Topographical map of subjective states evoked by focal seizures and electrical stimulation of the human insula.

OBJECTIVE

The goal of this study was to investigate how the topographical map of human subjective experiences induced by intracranial electrical stimulation (iES) compares to the map of subjective auras experienced by patients during seizures involving the same cortical areas (here, the insular cortex).

METHODS

We recruited 14 patients with insular epilepsies confirmed with intracranial electroencephalography in the United States (N = 7) and France (N = 7). We identified insular regions involved early in seizures (i.e., presumed seizure-onset zones [SOZs]), and documented the auras reported by each patient. Data from subjective reports of auras were then compared with subjective reports during insular iES in 10 of the 14 patients with confirmed insular seizures and in 17 other patients with stimulation of normal insular sites (previously reported by our group).

RESULTS

Epileptic auras reported by patients with seizures involving the insula were largely categorized as visceral, pain/temperature, or non-painful/non-temperature bodily sensations. We observed a striking similarity between the topographical maps of auras during insular seizures and the subjective states induced by the stimulation of the same insular regions (either identified as epileptic or not-epileptic).

SIGNIFICANCE: Our findings may guide informed clinical decision-making in patients with similar ictal semiology and insular lesions identified on magnetic resonance imaging. On the basis of our findings, we conclude that (1) electrically evoked and seizure-induced subjective symptoms are similar when the presumed SOZ involves the insula; (2) the topography of subjective experiences evoked by insular iES and seizures is largely anatomically consistent across subjects; and (3) stimulation of radiographically abnormal brain tissue seems to cause symptoms that are similar and reliable compared to the ones evoked by the stimulation of the same site in subjects without structural insular abnormalities. The extent to which these findings can be generalized to other cortical regions and networks remains to be determined.