Inclusion Criteria:  18-35 years of age Diagnosis of BD (DSM-5 criteria) in remission (euthymic for >2 months) or in a manic/hypomanic episode [manic/hypomanic or euthymic adults with BD (3-fifths manic/hypomanic); euthymic for > 2 months from most recent BD episode OR current manic/hypomanic episode] Not psychotic Score <3 on delusions, hallucinations, unusual thought content, and conceptual disorganization items of the Positive and Negative Syndrome Scale (PANSS) Unmedicated for >2 months or on any combination (except antidepressant monotherapy) of anxiolytics (benzodiazepines, buspirone, pregabalin, hydroxyzine) as needed, and/or atypical antipsychotics, and/or lithium, and/or other mood stabilizers, and/or non serotonin norepinephrine reuptake inhibitors (SNRI) antidepressants and/or non benzodiazepine hypnotics taken for >2 months, as these are commonly-prescribed medications for BD Right handed  Exclusion Criteria:  Not 18-35 years of age Diagnosis of BD in a depressive episode or diagnosis of BP in partial remission, euthymia that fails to meet full remission criterion of a period of at least 2 months in which there are no significant symptoms, e.g., only partial remission of symptoms or full remission of symptoms but for <2 months Diagnosis of BD in a depressive episode Personal and family history of epilepsy (TBS exclusion) Binge alcohol drinking Taking substances in the last month that can elevate seizure risk including but not limited to SNRI antidepressants, bupropion and stimulants (TBS exclusion) History of head injury, neurological, pervasive developmental disorder (e.g. autism), systemic medical disease and treatment (medical records, participant report) Mini-Mental State Examination score (cognitive state) <24 Premorbid North American Adult Reading Test (NAART) Intelligent Quotient (IQ) estimate<85 Visual disturbance: <20/40 Snellen visual acuity Left/mixed handedness (Annett criteria) History of alcohol/substance use disorder (SUD; all substances, including nicotine), and/or illicit substance use (except cannabis) over the last 6 months (SCID-5). Note: lifetime/present cannabis use (at non-abuse (<3 times in the past month) and non SUD levels) will be allowed, given its common usage in BD and young adults. Cannabis SUD over the last 6 months will not be allowed. Urine tests on scan days will exclude current illicit substance use (except cannabis). Salivary alcohol tests on scan days will exclude intoxicated individuals Binge drinking in the week before, and/or >3 units/day for the 3 days before, and/or alcohol in the last 12 hrs before, any TBS visit, confirmed at screening and scan days (to avoid TBS during alcohol withdrawal). Alcohol/nicotine/ caffeine/cannabis use (below SCID-5 SUD, binge levels) will be allowed, and used as covariates MRI exclusion: metallic objects, e.g., surgical implants; claustrophobia; positive pregnancy test for females (at the MRRC) or self-report pregnancy *Unable to understand English Scoring greater than or equal to 8 on Hamilton Depression Rating Scale (HRSD) at screen visit and depressive episode is confirmed on SCID-5 Scoring greater than or equal to 18 on HRSD at any study visit Psychosis Using allowed psychotropic medication for <2 months Using psychotropic medications other than those allowed in inclusion criteria Unmedicated for <2 months