Direct cortical stimulation of human posteromedial cortex

Neurology. 2017 Feb 14;88(7):685-691. doi: 10.1212/WNL.0000000000003607. Epub 2017 Jan 18.


Background: The posteromedial cortex (PMC) is a collective term for an anatomically heterogeneous area of the brain constituting a core node of the human default mode network (DMN), which is engaged during internally focused subjective cognition such as autobiographical memory.

Methods: We explored the effects of causal perturbations of PMC with direct electric brain stimulation (EBS) during presurgical epilepsy monitoring with intracranial EEG electrodes.

Results: Data were collected from 885 stimulations in 25 patients implanted with intracranial electrodes across the PMC. While EBS of regions immediately dorsal or ventral to the PMC reliably produced somatomotor or visual effects, respectively, we found no observable behavioral or subjectively reported effects when sites within the boundaries of PMC were electrically perturbed. In each patient, null effects of PMC stimulation were observed for sites in which intracranial recordings had clearly demonstrated electrophysiologic responses during autobiographical recall.

Conclusions: Direct electric modulation of the human PMC produced null effects when standard functional mapping methods were used. More sophisticated stimulation paradigms (e.g., EBS during experimental cognitive tests) will be required for testing the causal contribution of PMC to human cognition and subjective experience. Nonetheless, our findings suggest that some extant theories of PMC and DMN contribution to human awareness and subjective conscious states require cautious re-examination.

MeSH terms

  • Adult
  • Brain Mapping*
  • Cerebral Cortex / physiology*
  • Cerebral Cortex / physiopathology
  • Cerebral Cortex / surgery
  • Consciousness / physiology
  • Drug Resistant Epilepsy / physiopathology
  • Drug Resistant Epilepsy / surgery
  • Electric Stimulation*
  • Electrocorticography*
  • Female
  • Functional Laterality
  • Humans
  • Male
  • Motor Activity / physiology
  • Neurophysiological Monitoring
  • Preoperative Period
  • Touch Perception / physiology
  • Visual Perception / physiology