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Auditory target detection activates frontal and parietal cortices: Evidence from high gamma power and low-frequency phase coherence in the subdural electrocorticogram

Ryan T. Canolty1*, Maryam Soltani2, K. Koepsell3, C. Cadieu3, Sarang S. Dalal4, Erik Edwards5, Srikantan S. Nagarajan6, 7, Heidi E. Kirsch8, Nicholas M. Barbaro8, 9 and Robert T. Knight1, 2, 8
  • 1 Helen Wills Neuroscience Institute, University of California, United States
  • 2 Department of Psychology, University of California, United States
  • 3 Redwood Institute for Theoretical Neuroscience, University of California, United States
  • 4 Processus mentaux et activation cérébrale, INSERM Unite 821, France
  • 5 Department of Neurosurgery, University of Washington, United States
  • 6 Department of Radiology, University of California, United States
  • 7 Department of Bioengineering, University of California, United States
  • 8 Department of Neurology, University of California, United States
  • 9 Department of Neurosurgery, University of California, United States

Prior studies employing functional magnetic resonance imaging (fMRI) report cortical activation associated with target detection in both frontal and parietal areas. In contrast, studies using scalp electroencephalography (EEG) report large P300 event-related potentials (ERPs) over parietal sites with markedly reduced activity over frontal regions. We addressed this apparent electrophysiological-fMRI dissociation by recording the electrocorticogram (ECoG) from a 64-channel subdural grid during an auditory target detection task. Patients undergoing surgical treatment for intractable epilepsy were implanted with an electrode grid over fronto-temporal regions followed by approximately one week of continuous monitoring of the ECoG. During this time, patients engaged in a target detection task using auditory presentation of proper names (targets) and verbs or nonwords (distractors). ECoG high gamma (80-160 Hz) activation was observed in superior temporal areas for all auditory stimuli, while lateral frontal and parietal were selectively activated by targets as opposed to distractors. Importantly, the ECoG high gamma response to targets was more robust than ERPs over frontal areas. Several of the electrodes with target-specific responses also exhibited changes in the pattern and strength of low-frequency phase coupling, as revealed by a recently-developed multivariate phase fitting model, consistent with the hypothesis that phase coherence is critical for long-range communication. The finding that electrodes over lateral frontal cortex exhibit both strong high gamma activity and weak ERP generation during target detection supports the hypothesis that lateral frontal cortex is actively involved in target detection and resolves the ERP-fMRI dissociation since high gamma appears to be the cortical drive for the BOLD response. The observed changes in the large-scale pattern of low-frequency phase coupling suggest a role for the lateral frontal cortex in dynamic regulation of voluntary attention. Supported by NINDS Grants NS21135 (RTK), PO40813 (RTK), and 1F31NS060406-01A1 (RTC).

Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Türkiye, 1 Sep - 5 Sep, 2008.

Presentation Type: Poster Presentation

Topic: Brain Electrical Oscillations in Cognition

Citation: Canolty RT, Soltani M, Koepsell K, Cadieu C, Dalal SS, Edwards E, Nagarajan SS, Kirsch HE, Barbaro NM and Knight RT (2008). Auditory target detection activates frontal and parietal cortices: Evidence from high gamma power and low-frequency phase coherence in the subdural electrocorticogram. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.119

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Received: 03 Dec 2008; Published Online: 03 Dec 2008.

* Correspondence: Ryan T Canolty, Helen Wills Neuroscience Institute, University of California, Berkeley, United States, rcanolty@gmail.com