UC San Diego

Language production requires rapid and dynamic coordination. Efficient communication is proposed to rely on cognitive control processes that support lexical retrieval by resolving interference between lexical representations. According to the Dual Mechanisms of Cognitive Control Framework, cognitive control comprises two complementary processes: proactive control which maintains task-driven goals in anticipation of conflict, and reactive control, which is recruited after conflict detection to prevent errors. These control processes have been associated with overlapping neural substrates, including the dorsomedial (dmPFC) and lateral prefrontal cortex, when overcoming linguistic and nonlinguistic conflict. Across three studies, this dissertation examines the nature of cognitive control mechanisms during word retrieval by characterizing the differential involvement of proactive and reactive control. We employ a combination of behavioral paradigms, along with invasive and non-invasive electrophysiological recordings across multiple populations with different language experiences and neurological impairments. Behavioral results in neurotypical participants show that these processes are dynamically engaged in resolving semantic interference, with proactive control recruited following high conflict situations triggering higher demands of top-down control, while reactive control arises once interference is detected spontaneously. Intracranial data recordings from individuals with intractable epilepsy reveal significant increases in aperiodic-adjusted theta band oscillations during semantic conflict relative to baseline in the dmPFC, while no significant activity is observed in no-conflict situations. Furthermore, the difference in aperiodic-adjusted theta power between high-conflict and no-conflict trials within the dmPFC is modulated by the level of conflict in the preceding trial, suggesting a role of this region in both proactive and reactive control in lexical interference resolution during language production. Finally, our investigations into between-language conflict resolution in Spanish-English bilinguals with and without stroke-induced aphasia reveal that dmPFC-mediated reactive control is also recruited to resolve crosslinguistic interference. This mechanism appears to be disrupted during word retrieval following stroke-induced lesions in core language regions, but may be preserved to resolve nonlinguistic interference. The results of these studies advance our understanding of the behavioral and brain dynamics underlying cognitive control processes in word retrieval, suggesting that the dmPFC supports both proactive and reactive control mechanisms involved in resolving within and between-language conflict.