Gamma tACS over the temporal lobe increases the occurrence of Eureka! moments

• Published in: Scientific reports Vol. 9; no. 1; p. 5778
• Main Authors: Santarnecchi, Emiliano, Sprugnoli, Giulia, Bricolo, Emanuela, Costantini, Giulio, Liew, Sook-Lei, Musaeus, Christian S., Salvi, Carola, Pascual-Leone, Alvaro, Rossi, Alessandro, Rossi, Simone
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.04.2019; Nature Publishing Group
• Subjects: 59/36; 631/378/2649/1749; 631/378/3920; 631/443/376; Accuracy; Adult; Alpha Rhythm; Brain research; Cognition; EEG; Electroencephalography; Female; Functional magnetic resonance imaging; Gamma Rhythm; Humanities and Social Sciences; Humans; Investigations; Male; multidisciplinary; Neural networks; Neurology; Neurophysiology; Neurosciences; Problem Solving; Science; Science (multidisciplinary); Semantics; Temporal lobe; Temporal Lobe - physiology; Transcranial Direct Current Stimulation - methods
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-42192-z

The solution to a problem might manifest itself as a burst of unexpected, unpredictable clarity. Such Eureka! events, or Insight moments, are among the most fascinating mysteries of human cognition, whose neurophysiological substrate seems to include a role for oscillatory activity within the α and γ bands in the right parietal and temporal brain regions. We tested this hypothesis on thirty-one healthy participants using transcranial Alternating Current Stimulation (tACS) to externally amplify α (10 Hz) and γ (40 Hz) activity in the right parietal and temporal lobes, respectively. During γ-tACS over the right temporal lobe, we observed an increase in accuracy on a verbal insight task. Furthermore, electroencephalography (EEG) data revealed an increase in γ spectral power over bilateral temporal lobes after stimulation. Additionally, resting-state functional MRI data acquired before the stimulation session suggested a correlation between behavioral response to right temporal lobe tACS and functional connectivity of bilateral temporal lobes, in line with the bilateral increase in γ band revealed by EEG. Overall, results suggest the possibility of enhancing the probability of generating Eureka! moments in humans by means of frequency-specific noninvasive brain stimulation.