Evidence for predictions established by phantom sound.

Predictions, the bridge between the internal and external worlds, are established by prior experience and updated by sensory stimuli. Responses to omitted but unexpected stimuli, known as omission responses, can break the one-to-one mapping of stimulus-response and can expose predictions established by the preceding stimulus built up. While research into exogenous predictions (driven by external stimuli) is often reported, that into endogenous predictions (driven by internal percepts) is rarely available in the literature. Here, we report evidence for endogenous predictions established by the Zwicker tone illusion, a phantom pure-tone-like auditory percept following notch noises. We found that MMN, P300, and theta oscillations could be recorded using an omission paradigm in subjects who can perceive Zwicker tone illusions, but could not in those who cannot. The MMN and P300 responses relied on attention, but theta oscillations did not. In-depth analysis shows that an increase in single-trial theta power, including total and induced theta, with the endogenous prediction, is lateralized to the left frontal brain areas. Our study depicts that the brain automatically analyzes internal perception, progressively establishes predictions and yields prediction errors in the left frontal region when a violation occurs.

Deficient sensory and cognitive processing in children with cochlear implants: An event-related potential study.

Compared with children having normal hearing (NH), those with cochlear implants (CIs) perform poorly in spoken language comprehension which involves both low-level acoustic encoding and higher-level cognitive processing. Here, we performed an electroencephalography study to portray this brain dynamics of speech perception in CI children. We presented a Mandarin Chinese monosyllable or four-syllable idiom to CI and NH children, and infrequently varied its lexical tone to form a novel monosyllable or pseudo-idiom in an oddball paradigm. The tone contrast embedded in the monosyllables evoked similar mismatch negativities (MMNs) in CI and NH children at an early stage (~200 ms). However, the amplitude of the MMN evoked by the tone contrast in the idiom context was significantly lower in CI children than in NH children. Furthermore, robust late discriminative negativity (LDN) at a late stage (~500 ms) was found only in NH children, but not in CI children. The MMN and LDN findings indicate deficits of low-level acoustic encoding in a complex context (such as an idiom) and higher-level cognitive processing in CI children, respectively. Both deficient sensory and cognitive processing may contribute to the speech perception difficulties in CI children.