Investigation Of Phonological-lexical Representation Transformation In Speech Production And Perception

Speech processing includes two basic processes,speech perception and speech production.Fluent verbal communication requires a close connection between the two processes of speech perception and speech production.It is important to understand the processing mechanisms within and between the two processes of speech perception and speech production.Speech perception and production involves multiple levels of representations and transformation between representations.Taking the phonological and lexical levels as an example,in speech perception,integrating and processing speech sound(the auditory dimension of speech processing)will activate lexical processing for speech comprehension.In speech production,lexical activation in the form of phonology is converted to the motor articulatory system(the motor dimension of speech processing)to output speech.During the dynamics of speech production and perceptual,the motor and auditory dimensions of speech processing interact in a complex manner for efficient monitoring and control.Therefore,at least three representational transformations are in the functional closeloop of speech processing at the phonological-lexical level.Speech perception involves the transformation from the auditory dimension of speech to the lexical level.Speech production involves the transformation from the lexical level to the motor dimension of speech.The transformation between the motor dimension of speech and the auditory dimension of speech effectively links speech production and speech perception.The present study has been conducted to investigate the relationship between speech perception and speech production by exploring the mechanisms of the phonological-lexical functional close-loop in three experiments with noninvasive scalp EEG and intracranial EEG recordings.Study 1 explored the neural mechanisms of lexicalphonological and lexical-semantic representations and phonological-to-lexical transformation in speech perception.Using repetition paradigms at the phonological and lexical-semantic levels with intracranial EEG recordings,we found that lexical-semantic repetition effects were observed in the middle temporal gyrus(m MTG),whereas both phonological repetition effects and lexical-semantic repetition effects were found in the anterior middle temporal gyrus(a MTG).This result supports that the MTG from anterior to posterior may be responsible for processing phonological to lexical transformation in speech perception.Study 2 explored whether exists a direct pathway from the lexical level to the phonological-motor dimension of speech in speech production.Using a Chinese production task with intracranial EEG recordings,we compared the onset latencies in the high-gamma frequency band power among visual,auditory,and motor areas.The results showed that the onset latency of the lexical-orthographic visual cortices involved in the lexical level was significantly earlier than that of the auditory cortices.The onset latency of the articulatory motor area(BA44)was also significantly earlier than that of the auditory cortices.These results preliminarily suggest a direct and fast pathway linking between lexical and the motor dimension of speech in speech production.This fast pathway complements the classical indirect lexical-to-auditory-target-to-phonological-motorencoding pathway for efficient speech production.Motor-speech integration effectively links speech production and speech perception.Study 3 investigated the transformation between the motor dimension of speech and the auditory dimension of speech by examining how distinct ways of speech production affect speech perception.We designed a novel delayed articulation paradigm and used noninvasive scalp electroencephalography(EEG)recordings to investigate the interaction between the motor and perceptual systems during speech preparation and its neural mechanisms.The results showed that distinct articulatory motor preparations had opposite modulation effects on auditory speech processing neural responses.These results reveal the existence of neural signals of different properties in the transformation from the motor dimension of speech to the auditory dimension of speech,which can be integrated with sensory input to modulate perception.In conclusion,this study preliminarily investigated the representational transformation mechanism in the phonological-lexical functional close-loop in speech production and perception.It was found that anterior MTG represented both lexicalphonology and lexical-semantics,potentially subserving the transformation from the auditory dimension of speech to the lexical level via a common neural representation in speech perception.Moreover,a direct pathway in speech production that mediates the transformation from lexical to phonological motor dimensions is supported by the immediate neural response latencies between visual regions of orthographic-lexical processes and motor phonology regions.Furthermore,the efficient integration of speech articulation and auditory processing is accomplished by the different neural signals generated in the motor-to-sensory transformation.This study takes the phonologicallexical transformation as an example to preliminarily reveal the mechanism of representational transformation in speech production and speech perception.