Sequencing Processing And Language Lateralization

Sequence processing is a serial ordering mechanism to combine a finite set of discrete learned phonological units(such as phonemes or syllables)into larger meaningful expressions of words and sentence.Sequence processing plays an important and irreplaceable role in language perception and production.However its origin and mechanism are not yet clear.Here,we asked three questions:(1)does sequence processing cause language lateralization and is the lateralization specific to content(syllables and tones)?(2)How do distinct speech processes(perception,execution,and planning and estimation of sequencing)influence lateralization(3)Whether motor-sensory processing is left dominant or bilateral in language and sequence processing?In this study,we investigated the neural mechanism of sequence processing of syllable,tone,and finger movement sequences using functional MRI.Our results showed that(1)the planning and estimation of sequencing in syllable is left dominant in the superior parietal area,whereas the execution of sequencing in this task is not significantly left lateralized;(2)the sensory-motor(or perception-production)interface during syllable sequencing and tone sequencing are different:bilateral middle temporal gyrus is involved in tone sequencing;while left temporal area in syllable task,there is no enough significant lateralized;(3)execution of sequencing are further examined in three tasks:middle frontal gyrus and tempo-parietal junction are activated in tone sequencing;inferior frontal cortex is involved in motor sequencing when using right hand;left frontal and parietal regions are involved in syllable sequencing,but only in the imagery condition.Our results suggest that processing dynamics,modality and content of tasks modulated the hemispherical lateralization during sequencing in speech and language.