The Cardioinhibitory Responses of the Right Posterior Insular Cortex in an Epileptic Patient

Abstract

Background: The insular cortex (IC) has long been implicated in the central regulation of the autonomic nervous system but its precise role remains to be determined. We studied the role of IC in cardiovascular control using a multimodality approach consisting of isometric handgrip exercises, functional magnetic resonance imaging (fMRI) activation during handgrip exercises, and direct electrical stimulations of the posterior right IC in a single patient. Method: A 24-year-old patient had medically intractable epilepsy secondary to a small ganglioglioma in the right posterior IC. His cardiovascular responses to 30 and 70% maximum voluntary contraction (MVC) handgrip exercises were recorded in the lab and during fMRI and compared to those of 10 healthy control subjects. He subsequently underwent stereo-electroencephalography with depth electrodes in the right posterior IC and further study of the cardiovascular responses to electrical stimulation at rest and during MVC handgrip exercises. Result: fMRI data showed nearly absent activation in the right IC relative to healthy subjects. At rest, electrical stimulation of the right posterior inferior IC but not the superior IC suppressed heart rate (HR) by 3 beats per minute. During exercise, the HR response to isometric handgrip contraction was weakened when the right posterior inferior IC was simultaneously stimulated. Conclusion: This study shows that, in this patient, the right posterior inferior IC is an important cardioinhibitory center and interference with this region alters the cardiac response to handgrip exercise. Further investigations are required to examine the cardiovascular control of the IC.

Forebrain neurocircuitry associated with human reflex cardiovascular control

“…First, electrical stimulation of brain regions in awake epileptic patients with indwelling electrodes have been performed in a very limited extent and, when performed, still only expose one site at a time. Nonetheless, this model has reinforced the important role that focal regions of the IC have (or do not have) on cardiac function (Oppenheimer et al, 1992a ; Al-Otaibi et al, 2010 ), the details of which are outlined below. More recently, the introduction of functional magnetic resonance imaging (fMRI) (Ogawa et al, 1990 , 1992 ) has enabled studies of the temporal and spatial patterns of cortical activation patterns in conscious humans.…”

“… Meta-analysis summary of data from our laboratory (n = 124) (Wong et al, 2007a , b ; Al-Otaibi et al, 2010 ; Goswami et al, 2011 ; Norton et al, 2013 ) of common cortical regions associated with heart rate control during non-fatiguing handgrip exercise task [this figure originally published in Shoemaker et al ( 2015 ) (used with permission)] . These participants each performed 3–7 bouts of moderate intensity (35–40% maximal strength) handgrip tasks each lasting 30 s. Left panels with red dots: Cortical areas of increased activation relative to baseline in response to short duration, moderate intensity isometric handgrip exercise.…”

Forebrain organization for autonomic cardiovascular control

“…Two models have been used to accomplish this goal in humans. First, electrical stimulation of brain regions have been performed in conscious epileptic patients with indwelling electrodes (Al-Otaibi et al, 2010;Oppenheimer et al, 1992). To our knowledge, these studies are few, and are limited to insula cortex stimulation.…”

Stuttered swallowing: Electric stimulation of the right insula interferes with water swallowing. A case report

“…The anterior insula has been implicated in the processing of visceral sensation from the pharynx [21], esophagus and gastrointestinal tract [22], vibrotactile stimulation [23], gustation [24], olfaction [25], and emotions such as disgust [26]. Other fMRI studies, however, reported swallow-related activation of the posterior insula [3], which is involved in autonomic regulation [18,27], including heart rate and respiration. Consistent with this, a meta-analysis of swallow-related brain imaging implicated both the anterior and posterior insula in swallowing [15].…”

“…Pre-surgical electric stimulation was performed using depth electrodes that were implanted in the right posterior insular cortex, above and below the tumor (1 mm diameter size; Ad Tec Medical Instrument Corp., Racine, WI, USA) [18]. The depth electrodes were inserted stereotactically using a Leksell stereotactic frame and a Stealth station planning system (Medtronic-Sofamor Danek, Minneapolis, MN, USA).…”