Authors :
Presenting Author: Anna Duong, n/a – Stanford University
Aaron Kucyi, PhD – Drexel University; Zoe Lusk, BS – Stanford University; Josef Parvizi, MD/PhD – Stanford University; Julian Quabs, PhD – Heinrich Heine University Düsseldorf; James Stieger, PhD – Stanford University
Rationale:
Functions of the human insula have been explored extensively with neuroimaging methods and clinical electrical stimulation studies that have suggested a functional segregation across different anatomical subregions of the structure. However, little is known about the functional organization of the human insular cortex at the fine-parcellated microstructural chemo-cytoarchitectural level. It remains to be determined whether various responses to electrical stimulation can be topographically delineated by the microstructural diversity of the insular cortex. The present study addresses this gap of knowledge by applying a multimodal approach linking direct electrical stimulation and intracranial EEG recordings with recently discovered chemo-cytoarchitectonic map of the human insula.
Methods:
Electrical brain stimulation was performed as a clinical procedure in seventeen patients implanted with stereo-EEG electrodes in the insula for presurgical evaluation of their refractory epilepsy.
During this procedure, pairs of neighboring electrodes were selected for electrical stimulation. To determine the exact location of electrodes on the microstructural map of the human insula, the cytoarchitectonic maximum probability maps of the insula were registered to the individual brain MRI scans of each subject. We also recorded intracranial EEG signals during a gradual onset continuous performance task (gradCPT) which is designed to probe sustained top-down attention as well as bottom up attention.
Results:
Stimulation of 57 sites (40%) out of 142 total pairs induced a change in the human participants’ conscious experience in the categories of pain/temperature (53%), visceral/autonomic (14%), non-painful/non-thermal somatosensory (25%), anxiety (7%), and taste/olfactory sensations (5%) which showed a topographical allocation to microstructural areas when mapped onto the probabilistic cytoarchitectonic parcellation. In the posterior insula, significant clusters of pain/thermal responses were observed in areas lg2/ld2, while non-painful/non-thermal somatosensory responses were concentrated in area ld3. In the anterior insula, significant visceroceptive responses were elicited specifically in area Id6. In two subjects, the stimulation of the same area caused heightened anxiety. In the adjacent Id7 area coinciding with the hub of resting state “salience network”, stimulations were largely silent but intracranial EEG recordings captured significant time-locked high-frequency activity (HFA) during a task that requires detection of salient infrequent stimuli.
Conclusions:
Our findings provide causal evidence confirming a link between functional architecture of the human insular cortex and the microstructural fine-grained chemo-cytoarchitectonic organization of its subregions.
Funding: N/A