Most of the world's languages include multiple varieties and dialects. Individual ability to successfully alternate between these varieties can be a socio-cultural and academic necessity for many bilingual speakers, including children in the US who alternate between African American English (AAE) and Mainstream American English (MAE). This dissertation study asked, "how does bidialectal language experience influence how the brain supports monodialectal and bidialectal language processing?" To answer this question, this dissertation focused on theoretical perspectives that suggest that early language experiences, especially with more than one language form, change how the brain processes and manages its languages. Much is now known about the cognitive and neurobiological mechanisms underlying language use and language mixing in bilinguals, yet little is known about related processes in bidialectal speakers. Critically, there is no research examining the neurobiology of code switching in bidialectal AAE speakers. Through two interrelated questions, I examine the neuro-cognitive processes of bidialectal speakers during an auditory functional infrared spectroscopy (fNIRS) task. The first study revealed differences in the way the brain supports monodialectal processing of AAE and MAE, with AAE revealing more overall brain activity. There were also notable differences in the regions that support monodialectal and bidialectal processing. My second study reciprocally supports my first study as I developed a novel culturally sensitive fNIRS protocol to collect high-quality data from ethnically and racially marginalized populations. Taken together, my dissertation studies addressed critical gaps in science and neuroimaging methods by advancing theoretical perspectives on language processes and how those are influenced by common linguistic experiences within the US, in addition to enriching our ability to research groups that are often underrepresented in neuroscience and neurolinguistics research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]