This study is designed to look at the relationship between brain glucose utilization, neurotransmission (e.g., glutamate, also known as the main excitatory amino-acid neurotransmitter in the brain), and synaptic density. This relationship will be explored in the brain's prefrontal cortex, an area important in decision-making and impulsivity.

Inclusion Criteria:

1. Age 18-55 years;
2. Voluntary, written, informed consent;
3. Physically healthy by medical history, physical, neurological, ECG and laboratory examinations;
4. DSM-IV criteria for Cocaine Dependence (304.20) (Note: subjects will also meet DSM-5 criteria for Cocaine Use Disorder);
5. Documented evidence (by urine toxicology) of abstinence from cocaine (2 weeks for scan 1, and 2 and 4 weeks for scans 2 and 3, respectively)
6. Full scale and verbal IQs > 80;
7. For females, a negative serum pregnancy test (β-HCG) at screening and negative urine pregnancy test on PET scan day prior to imaging.

Exclusion Criteria:

1. A history of other substance dependence (e.g., alcohol, opiates, sedative hypnotics), except for nicotine;
2. A primary DSM-IV Axis I major psychiatric disorder (e.g., schizophrenia, bipolar disorder, major depression, etc.) as determined by the Structured Clinical Interview for DSM-IV (SCID);
3. A history of significant medical (e.g., cardiovascular, diabetic/metabolic) or neurological (e.g., cerebrovascular, seizure, traumatic brain injury) illness;
4. Current use of psychotropic and/or potentially psychoactive prescription medications;
5. Medical contraindications to participation in a magnetic resonance imaging procedure (e.g., ferromagnetic implants/foreign bodies, claustrophobia, cardiac pacemaker, prosthetic valve, otologic implant, etc.);
6. For females, laboratory (β-HCG) evidence of pregnancy, physical evidence of pregnancy;
7. For subjects interested in pharmacotherapy component, history of allergies to NAC and current elevation on liver function tests above twice the normal limit;
8. Subjects with history of prior radiation exposure for research purposes within the past year such that participation in this study would place them over FDA limits for annual radiation exposure. This guideline is an effective dose of 5 rem received per year;
9. Subjects with current, past or anticipated exposure to radiation in the work place within one year of proposed research PET scans;
10. History of a bleeding disorder or are currently taking anticoagulants (such as Coumadin, Heparin, Pradaxa, Xarelto);
11. Blood donation within eight weeks of the start of the study.