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Abstract
The frequency-following response (FFR) offers a powerful window into how attention and domain-specific expertise shape early auditory encoding. Yet, despite decades of research, the cognitive role of the FFR remains underdefined. Existing studies of attention often report mixed or null results, suggesting that its influence on early auditory encoding may be weak or contingent on individual factors such as expertise. Conversely, studies of expertise consistently show enhanced FFR amplitudes in musicians and other experts (e.g., Wong et al., 2007; Parbery-Clark et al., 2009; Strait et al., 2013), but these have largely been conducted under passive listening conditions, without explicit attentional demands. As a result, the literature defaults to the assumption that larger FFR amplitudes signify superior encoding, yet this assumption lacks strong theoretical grounding. To address this gap, the present dissertation examines the joint effects of attention and expertise across active and passive listening conditions, drawing on competing predictions from gain modulation models (e.g., Hillyard et al., 1998; Zatorre et al., 1999, 2012) and dynamic tuning accounts (Fritz et al., 2003; Fritz et al., 2007; Elhilali et al., 2007). Across four experiments, the findings reveal that expertise sharpens FFR responses in a non–context-specific manner, consistent with dynamic tuning models that emphasize selective suppression of irrelevant neural activity. However, under more challenging tasks, effort in experts was associated with global increases in FFR amplitude, suggesting the flexible recruitment of gain-modulation mechanisms to strengthen performance. Passive listening, by contrast, consistently elicited broadly elevated FFR amplitudes, indicating a diffuse, non-selective form of auditory engagement. Taken together, these results suggest that early auditory encoding flexibly engages mechanisms of both selectivity and gain, depending on task difficulty, effort, and expertise. The findings contribute toward a more comprehensive model of auditory attention in which dynamic tuning enhances encoding efficiency under favorable conditions, while gain modulation amplifies responses to meet the demands of effortful listening.