title: Heart cycle-related effects on event-related potentials, spectral power changes, and connectivity patterns in the human ECoG.
abstract: The perception of one's own heartbeat is a fundamental interoceptive process that involves cortical and subcortical structures. Yet, the precise spatiotemporal neuronal activity patterns underlying the cortical information processing have remained largely elusive. Although the high temporal and spatial resolution of electrocorticographic (ECoG) recordings is increasingly being exploited in functional neuroimaging, it has not been used to study heart cycle-related effects. Here, we addressed the capacity of ECoG to characterize neuronal signals within the cardiac cycle, as well as to disentangle them from heart cycle-related artifacts. Based on topographical distribution and latency, we identified a biphasic potential within the primary somatosensory cortex, which likely constitutes a heartbeat-evoked potential (HEP) of neuronal origin. We also found two different types of artifacts: i) oscillatory potential changes with a frequency identical to the heart pulse rate, which probably represent pulsatility artifacts and ii) sharp potentials synchronized to the R-peak, corresponding to the onset of ventricular contraction and the cardiac field artifact (CFA) in EEG. Finally, we show that heart cycle-related effects induce pronounced phase-synchrony patterns in the ECoG and that this kind of correlation patterns, which may confound ECoG connectivity studies, can be reduced by a suitable correction algorithm. The present study is, to our knowledge, the first one to show a focally localized cortical HEP that could be clearly and consistently observed over subjects, suggesting a basic role of primary sensory cortex in processing of heart-related sensory inputs. We also conclude that taking into account and reducing heart cycle-related effects may be advantageous for many ECoG studies, and are of crucial importance, particularly for ECoG-based connectivity studies. Thus, in summary, although ECoG poses new challenges, it opens up new possibilities for the investigation of heartbeat-related viscerosensory processing in the human brain.
authors.affiliation: Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany; Epilepsy Center, University Medical Center Freiburg, Breisacher Straße 64, 79106 Freiburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kern
authors.affiliation: Neurobiology and Biophysics, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, 79104 Freiburg, Germany; Bernstein Center Freiburg, University of Freiburg, Hansastr. 9A, 79104 Freiburg, Germany.
authors.forename: Ad
authors.initials: A
authors.lastname: Aertsen
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, Breisacher Straße 64, 79106 Freiburg, Germany; Bernstein Center Freiburg, University of Freiburg, Hansastr. 9A, 79104 Freiburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Schulze-Bonhage
authors.affiliation: Epilepsy Center, University Medical Center Freiburg, Breisacher Straße 64, 79106 Freiburg, Germany; Bernstein Center Freiburg, University of Freiburg, Hansastr. 9A, 79104 Freiburg, Germany. Electronic address: tonio.ball@uniklinik-freiburg.de.
authors.forename: Tonio
authors.initials: T
authors.lastname: Ball
mesh_terms: D000293:Adolescent; D016477:Artifacts; D001931:Brain Mapping / Q000379:methods; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013003:Somatosensory Cortex / Q000502:physiology*
keywords: CFA; CSF; Connectivity; ECoG; EEG; EMG; ESM; Electrocorticogram; FDR; HEP; Heartbeat-evoked potential; PSI; Phase synchrony; SNR; Signal quality; Somatosensory cortex; cardiac field artifact; cerebrospinal fluid; electrical stimulation mapping; electrocorticogram; electroencephalogram; electromyogram; false discovery rate; heartbeat-evoked potential; phase synchrony index; signal-to-noise-ratio