A Neurosensory Account

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 headinjury or loss of consciousness)

• Patients: Diagnosis of PTSD

• Patients: If taking psychotropic medications, medication stability in the past 2months

• 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, metabolicsyndrome, 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 usedisorder are allowed given their high comorbidity with PTSD).

• Healthy controls: A history of diagnosis for a DSM-5 Axis I disorder or current useof psychoactive medications.

• Severe psychiatric instability or severe situational life crises, including evidenceof being actively suicidal or homicidal, or any behavior that poses an immediatedanger 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, amphetamines, narcotics, solvents, cocaine, hallucinogens,tranquilizers, barbiturates, etc.) or sleep medication for 48 hours before beingscanned.

• Are on calcium channel blockers (e.g., verapamil, nifedipine) or alpha-blockers (e.g., prazosin, terazosin) and are unable to stop these medications for a 48-hourperiod prior to scanning (to exclude the impact of these medications on theinterpretation of fMRI/EEG).

• Failed Urine Drug Screening Test: A rapid urine screening test that utilizesmonoclonal antibodies to detect elevated levels of specific drugs (includingalcohol, amphetamines, benzodiazepines, barbiturates, cocaine, marijuana, opiates,etc.) in urine (iCup)

• Pregnancy based on urine test. The safety of MR systems has not been established forfetuses

• Having electrically, magnetically, or mechanically activated implants (e.g., cardiacpacemakers), because the electromagnetic fields produced by the MR system mayinterfere with the operation of these devices.