A Neurosensory Account of Anxiety and Stress (Study 2)

Inclusion Criteria: * Right-handed * With normal or corrected-to-normal vision and normal olfaction * Between the ages of 18 and 50 years * Meeting the tACS screening criteria (see List I below; e.g., lack of a serious head injury or loss of consciousness) * Patients: Diagnosis of PTSD * Patients: If taking psychotropic medications, medication stability in the past 2 months * If having mild substance use disorder (for patients) or occasional substance use, abstention from use 48 hours before the experiment. Exclusion Criteria: * A history of diagnosis for a major medical illness (e.g., cancer, metabolic syndrome, cardiovascular disease, inflammatory disorders) or a neurological disorder (e.g., seizure, stroke, Parkinson's disease). * Patients: Concurrent Axis I diagnosis (depression, anxiety, and mild substance use disorder are allowed given their high comorbidity with PTSD). * Healthy controls: A history of diagnosis for a Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 Axis I disorder or current use of psychoactive medications. * Severe psychiatric instability or severe situational life crises, including evidence of being actively suicidal or homicidal, or any behavior that poses an immediate danger to self or others. * History of head trauma with unconsciousness (\> 5 minutes) * Report that they regularly drink 3 or more alcoholic beverages a day. * Report that they are unable to abstain from substance use (including alcohol, nicotine, cannabis, amphetamin…