title: Subcortical correlates of auditory perceptual organization in humans.
abstract: To make sense of complex auditory scenes, the auditory system sequentially organizes auditory components into perceptual objects or streams. In the conventional view of this process, the cortex plays a major role in perceptual organization, and subcortical mechanisms merely provide the cortex with acoustical features. Here, we show that the neural activities of the brainstem are linked to perceptual organization, which alternates spontaneously for human listeners without any stimulus change. The stimulus used in the experiment was an unchanging sequence of repeated triplet tones, which can be interpreted as either one or two streams. Listeners were instructed to report the perceptual states whenever they experienced perceptual switching between one and two streams throughout the stimulus presentation. Simultaneously, we recorded event related potentials with scalp electrodes. We measured the frequency-following response (FFR), which is considered to originate from the brainstem. We also assessed thalamo-cortical activity through the middle-latency response (MLR). The results demonstrate that the FFR and MLR varied with the state of auditory stream perception. In addition, we found that the MLR change precedes the FFR change with perceptual switching from a one-stream to a two-stream percept. This suggests that there are top-down influences on brainstem activity from the thalamo-cortical pathway. These findings are consistent with the idea of a distributed, hierarchical neural network for perceptual organization and suggest that the network extends to the brainstem level.
authors.affiliation: Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8503, Japan. Electronic address: yamagishi@u.ip.titech.ac.jp.
authors.forename: Shimpei
authors.initials: S
authors.lastname: Yamagishi
authors.affiliation: NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa, 243-0198, Japan. Electronic address: otsuka.s@lab.ntt.co.jp.
authors.forename: Sho
authors.initials: S
authors.lastname: Otsuka
authors.affiliation: NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa, 243-0198, Japan. Electronic address: furukawa.shigeto@lab.ntt.co.jp.
authors.forename: Shigeto
authors.initials: S
authors.lastname: Furukawa
authors.affiliation: Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Kanagawa, 226-8503, Japan; NTT Communication Science Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa, 243-0198, Japan. Electronic address: kashino.makio@lab.ntt.co.jp.
authors.forename: Makio
authors.initials: M
authors.lastname: Kashino
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods*; D000293:Adolescent; D000328:Adult; D001303:Auditory Cortex / Q000502:physiology*; D001307:Auditory Perception / Q000502:physiology*; D001933:Brain Stem / Q000502:physiology; D005071:Evoked Potentials; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013997:Time Factors; D055815:Young Adult
keywords: Auditory scene analysis; Bistable perception; Frequency following response; Middle latency response