Fidelity of first-person reports following intracranial neuromodulation of the human brain: An empirical assessment of sham stimulation in neurosurgical patients

Background: Brain stimulation, both invasive and non-invasive, is increasingly being used to modulate mood and other aspects of subjective experience in various neuropsychiatric conditions. Because this enterprise is deeply dependent on first-person reports provided by patients, sham stimulation is routinely employed to control for demand characteristics and placebo effects. However, a general empirical assessment of the fidelity of this control is missing.

Objective: To provide an empirical exploration of the fidelity of first-person reports following intracranial electrical stimulation (iES) in neurosurgical patients.

Methods: We assessed Type I (false positive) error rate following 159 sham stimulations administered to 44 adult epilepsy patients implanted with intracranial electrodes and undergoing iES as part of routine clinical procedures at the Stanford Medical Center.

Results: The majority of our patients (75%) never committed a single Type I error, and 93% of our sham stimulations (n = 148) yielded true negative reports. False positives were restricted to only 11 patients, and no patient committed more than a single Type I error, even after multiple sham stimulations.

Conclusion: Neurosurgical patients are highly resilient to Type I errors following sham intracranial brain stimulation. Our findings support the validity of prior research exploring first-person experiences elicited by electrical stimulation of the human brain. More broadly, our data are relevant to emerging efforts to use brain stimulation to modulate mood and other aspects of human subjective experience.