Exposure induced changes in EEG phase synchrony and entropy: A snake phobia case report

In this case study the electroencephalographic (EEG) activity of a 23 years old snake phobic patient was recorded one week before treatment, one week after successful one-session exposure therapy, and one year later. EEG recordings were obtained at rest and during exposure to pictures of snakes, pictures of equivalent arousing power, and emotionally neutral images, all of them taken from the International Affective Pictures System. Measures of brain dynamics were sample entropy (SampEn) for each EEG signal/channel and phase synchronization between pairs of EEG channels. Results showed dramatic changes in both measures one week after treatment: SampEn increased and phase synchrony decreased at all sites and pairs of channels respectively. At follow-up, however, we found patterns of entropy and synchrony change across conditions that were similar to the pre-treatment ones, while the patient did not report any fear at all. Despite the limitations of single case studies, these results suggest that the exposure-induced changes in EEG entropy and synchronization are large but transient. The transient increase of the brain's flexibility could be one of the working neurophysiological mechanisms of exposure therapy.