Abstract
Selecting pertinent events in the cacophony of sounds that impinge on our ears every day is regulated by the acoustic salience of sounds in the scene as well as their behavioral relevance as dictated by top-down task-dependent demands. The current study aims to explore the neural signature of both facets of attention, as well as their possible interactions in the context of auditory scenes. Using a paradigm with dynamic auditory streams with occasional salient events, we recorded neurophysiological responses of human listeners using EEG while manipulating the subjects' attentional state as well as the presence or absence of a competing auditory stream. Our results showed that salient events caused an increase in the auditory steady-state response (ASSR) irrespective of attentional state or complexity of the scene. Such increase supplemented ASSR increases due to task-driven attention. Salient events also evoked a strong N1 peak in the ERP response when listeners were attending to the target sound stream, accompanied by an MMN-like component in some cases and changes in the P1 and P300 components under all listening conditions. Overall, bottom-up attention induced by a salient change in the auditory stream appears to mostly modulate the amplitude of the steady-state response and certain event-related potentials to salient sound events; though this modulation is affected by top-down attentional processes and the prominence of these events in the auditory scene as well.
Highlights
Selecting relevant information from an auditory scene is guided either by the salience of the acoustic events or by behavioral goals
The current study focuses on how bottom-up, stimulus-driven salient changes in a dynamic scene modulate the neural representation of an auditory stream under different states of top-down attentional focus and with different complexities of the acoustic scene
Given the complex nature of saliency changes in the current paradigm, the observed auditory steady-state response (ASSR) changes likely reflect neural generators operating across larger neuronal groups or different neural centers (Escera et al, 2014); rather than mechanisms operating at the single neuron level such as stimulusspecific adaptation (SSA) which modulates the neural response to rare, unexpected or prominent events but is gated by the tuning properties of each neuron (Nelken, 2014)
Summary
Selecting relevant information from an auditory scene is guided either by the salience of the acoustic events (bottom-up driven) or by behavioral goals (top-down driven). Saliency-driven attentional mechanisms are greatly reflected in the stimulus representation at the level of sensory cortex as well as the propagation of information to frontal areas, all while modulating key markers of the neural response as reflected in event-related components such as Mismatch Negativity (MMN) (Näätänen and Michie, 1979; Näätänen et al, 2007; Kim, 2014) Such changes are often accompanied by further modulation due to task-demands and guided by top-down attention which affects sensory and frontal cortical networks (Picton and Hillyard, 1974b; Luck et al, 2000; Fritz et al, 2007a; Kiefer, 2007; Elhilali et al, 2009; Müller et al, 2009; Xiang et al, 2010). While there is an indirect association between these two components, they are not directly mapped from one to the other (Capilla et al, 2011; Zhang et al, 2013) and provide complementary views into the effect of stimulus and attentional manipulations on the neural response
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