Grant: Discovery Grants Program - Individual

When listening conditions are challenging, such as when speech is presented in high background noise, listeners need to expend additional effort to understand the message. The available neurocognitive evidence suggests that effortful listening is underpinned by increased activation of domain-general areas in the prefrontal cortex (e.g., dorsolateral prefrontal cortex), which supplements the activation in domain-specific areas (e.g., auditory cortex). From the perspective of electroencephalography (EEG), the increased prefrontal activation has been measured using changes in power in the alpha band (8-12 Hz). While most EEG studies have found that effortful listening is associated with power increases in the alpha band, some have paradoxically found decreases, which raises the possibility of separate inhibitory and excitatory activations. The limited spatial resolvability of EEG restricts the extent to which researchers have been able to reconcile these conflicting findings. From the perspective of functional magnetic resonance imaging (fMRI) or functional near infrared spectroscopy (fNIRS), research has consistently revealed increases in activation under effortful listening conditions. However, these methods provide no insight regarding whether the activations are predominantly inhibitory or excitatory, and they provide little insight regarding temporal dynamics. The proposed program of research will use concurrent fNIRS-EEG to develop a more comprehensive neurocognitive understanding of listening effort. This will be accomplished in 8 experiments and 1 methods study that are distributed across three themes. The first theme will investigate listening effort using concurrent fNIRS-EEG with speech stimuli. The second theme will investigate listening effort using concurrent fNIRS-EEG with music stimuli. The use of music provides an opportunity to examine listening effort outside of the canonical paradigm of speech listening. The third theme incorporates neurostimulation techniques to alter endogenous oscillatory activity in a manner that is expected to manipulate listening effort. This program of research offers a unique opportunity for knowledge generation and training. By combining observations from fNIRS and EEG, and by leveraging the causal inferences available through neurostimulation, we expect to develop a more comprehensive understanding of speech and music processing under challenging listening conditions. This program of research will also help to reconcile uncertainty in the literature arising from conflicting findings about how oscillatory power may be related to listening effort. Finally, in the process of conducting the proposed experiments we expect to refine the nascent methodological and analysis frameworks for fNIRS-EEG that may be of broad use to researchers working in cognitive neuroscience.