![]() timing, amplitude, consistency, and pitch tracking, see Fig. The FFR is a noninvasive means of reliably measuring the fidelity and precision with which the brain encodes sound. Studies using the FFR have played an instrumental role in this evolution of thinking. Over the years, the field has moved away from treating the subcortical auditory system as a bottom-up, hardwired conduit for sound, and is increasingly recognizing the contribution of top-down influences within the context of distributed neural networks. Identified as subcortical in origin, they were viewed as a potential supplement to behavioral audiometry. Human FFRs were first measured in the 1970s 5. for technical details on the MEG-FFR 4 (see Box 1 for key points). ![]() For guidance on collecting FFRs, see Skoe and Kraus for a tutorial in EEG-FFR collection 2, Krizman and Kraus for a tutorial on EEG-FFR analysis 3, and Coffey et al. Traditionally, FFRs have been measured in humans as electrophysiological potentials to sound, recorded from the scalp. Consequently, sound encoding is relevant to the study of many higher-level functions central to human communication, including speech and music.įrequency-following responses (FFRs) are recordings of phase-locked neural activity that is synchronized to periodic and transient aspects of sound. The fidelity of sound encoding in these ascending pathways affects all cognitive processes that use the information-and in turn, these ascending pathways are affected by cognitive processes via the vast efferent system. Neurons in the lemniscal (or “primary/classical”) pathway are thought to be the main bearers of temporally varying information, with synapses in the brainstem (cochlear nucleus and superior olivary complex), midbrain (central nucleus of the inferior colliculus), thalamus (ventral division of the medial geniculate body), and the primary auditory cortex. Auditory information enters the brainstem from the cochlea via the auditory nerve and ascends via both lemniscal and nonlemniscal auditory pathways 1. This task is accomplished by a complex, interconnected, and parallel system. The auditory system must faithfully encode and process rapid variations in acoustic signals and precisely extract important features, such as frequency, amplitude modulation, and sound onsets and offsets.
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