Research Into Brain Predictions Established By Auditory Negative Afterimage

Predicting the future based on experience is crucial to survival in the world.Predictions can be made exogenously,based on external stimuli,or endogenously,based on internal perceptions or intentions.Although previous research has primarily focused on exogenous predictions,recent work suggests that endogenous predictions may be independent of exogenous predictions.An exogenous prediction template can be exposed by the omission response.That is elicited by an infrequent absence of stimuli(deviant)interspersed in a frequent stimulus sequence(standard).Since there are no physical stimuli involved,this response can only be attributed to the predictions established by prior stimuli.Phantom perceptions,conscious experiences without corresponding external stimuli,can provide a compelling chance to dissociate endogenous predictions from exogenous predictions.However,it is unclear whether phantom perception can establish endogenous predictions.To address this issue,an omission paradigm dependent on phantom sound was designed.The Zwicker tone illusion(ZT)is a phantom tonal perception immediately following notch noise stimulation.As an acute tinnitus model,it is easy to induce in healthy people.Its heterogeneity,most people hear it(called ZT perceivers or ZT(+)),whereas a few people do not(called non-perceivers or ZT(-)),offers a suitable control for exploring whether endogenous predictions exist.The omission paradigm based on ZT illusions was a random stimulus sequence,consisting of frequent inducers(notch noise,NN)and infrequent control noise(positive control:white noise followed by a pure tone,WP;negative control:white noise alone,WN).Thirty-one ZT(+)and twenty ZT(-)were presented with the stimulus sequence in the attended condition and unattended condition.Simultaneously their EEGs were recorded.Despite receiving the same sequence,ZT(+)and ZT(-)formed distinct rules.For ZT(+),a noise followed by a pure-tone-like percept was rarely violated by noise alone(WN).In contrast,for ZT(-),the noise alone was rarely violated by noise followed by a pure tone(WP).The results showed that there are ZT perceivers and nonperceivers in the population,and their proportion is very different,with nonperceivers accounting for only about 10%of the population(27/269).The best induction parameters for ZT illusions in ZT(+)vary by subject,but most subjects are at a center frequency of 4 kHz and a bandwidth of 1.0 octaves.In the attended condition,WN induced significant MMN,P300,and theta enhancement only in the ZT(+)group.Significant differences between groups confirmed the ZT-dependent omission responses.Moreover,the theta power in the left frontal area was significantly trial-by-trial correlated with the local illusory omission rate.This supports that omission responses increase with the confidence of the endogenous prediction.WP produced significant MMN,P300,and theta enhancement in both groups,which confirmed that ZT(-)formed an abstract rule with WP as a deviation and also showed that ZT(+)could identify the difference between ZT illusions and true pure tone.This response observed in ZT(-)was significantly stronger than that in ZT(+),suggesting distinct perceptual roles WP played in both groups.In the unattended condition,the ZT-dependent omission responses still existed but were only manifested by theta enhancement.ROC analysis shows that the enhancement of theta power in the unattended condition can be used to classify the two groups.In addition,the main contributor to theta power enhancement is the non-phase locked component.Finally,the onset response of ZT illusions was observed only in the presence of attention,also expressed as theta power enhancement.Consequently,the findings of ZT-dependent omission responses reveal that phantom sound automatically establishes endogenous predictions and yields prediction errors when violated by its sudden omission.The left frontal area may play a critical role in this predictive processing.This endogenous prediction is independent of the physical stimulus,and thereby confirms and embodies the internal model.The brain operates in a predictive manner,building its internal model to interact with the external world.Furthermore,in the absence of attention,the non-phase-locked component outperformed the phase-locked component.The interaction between phantom perception and cognitive predictions provides the basis for understanding the pathological mechanism of abnormal perception and opens up a possibility for objectively measuring phantom perception.