Investigating Neural Mechanism Of Numerical Cognition Based On Eeg Analysis

Numerical cognition refers to individual's understanding of numerical stimuli and applying it to cognitive processing,such as numerical calculations.Research into brain and cognitive processes involved in numerical cognition mediates development and scientific cultivation of numeracy.Research interests in numerical cognition mainly concern whether numerical representation is abstract,brain and cognitive processes involved in arithmetic,the involvement of language processing in numerical processing,etc.A majority of cognitive neuroimaging research in numerical cognition use ERPs and fMRI techniques.However,EEG signatures in specific frequency bands could provide more detailed and accurate spatiotemporal information with respect to cognitive processed involved in numerical cognition than the corresponding measures based on broadband electrophysiological signals or the blood oxygen level-dependent(BOLD)fMRI signals.Centering on unresolved issues in numerical cognition,based on event-related EEG signals and relevant data analytical methods,the following studies have been conducted,1)The study of differential recruitment of brain networks in single-digit addition and multiplication: Previous neuroimaging research investigating dissociation between single-digit addition and multiplication has suggested that the former placed more reliance on the visuo-spatial processing whereas the latter on the verbal processing.However,there has been little exploration into the disassociation in spatio-temporal dynamics of the oscillatory brain activity in specific frequency bands during the two arithmetic operations.To address this issue,the electroencephalogram(EEG)data were recorded from 19 participants engaged in a delayed verification arithmetic task.By analyzing oscillatory EEG activity in theta(5–7Hz)and lower alpha frequency(9–10 Hz)bands,we found different patterns of oscillatory brain activity between single-digit addition and multiplication during the early processing stage(0–400ms post-operand onset).Experiment results in this study showed a larger phasic increase of theta-band power for addition than for multiplication in the midline and the right frontal and central regions during the operator and operands presentation intervals,which was extended to the right parietal and the right occipito-temporal regions during the interval immediately after the operands presentation.In contrast,during multiplication higher phase-locking in lower alpha band was evident in the centro-parietal regions during the operator presentation,which was extended to the left fronto-central and anterior regions during the operands presentation.Besides,we found stronger theta phase synchrony between the parietal areas and the right occipital areas for single-digit addition than for multiplication during operands encoding.These findings of oscillatory brain activity extend the previous observations on functional dissociation between the two arithmetic operations.2)The study of dynamic reorganization of brain functional network during simple arithmetic.Despite being solved efficiently,simple arithmetic cause functional changes in the oscillatory brain dynamics across distributed brain regions.Our previous electroencephalography(EEG)study suggested that oscillatory brain activity at theta frequency plays a critical role in single-digit addition and multiplication.However,little characterization has been performed on functional interactions between distributed cortical regions during simple arithmetic.To address this issue,using graph properties,we explored and compared the sub-second time-scale reorganization of arithmetic-related brain functional networks at theta frequency band for single-digit addition and multiplication.The results show that event-related topology reorganization of functional network at theta frequency band is rapid and transient.Specifically,in the early stage of arithmetic,cognitive networks in theta frequency band are reorganized towards the optimum organization for efficient information processing,characterized by lower modularity and higher clustering coefficient.The optimum organization dissolved at the late stage,suggesting a decreased demand for cognitive effort which drives the topology reorganization of the theta network.In addition,this study reveals that the brain functional network during addition has less modularity and greater clustering coefficient compared to multiplication in the encoding stage,suggesting greater cognitive effort involved in addition.These results characterized the dynamic changes of connectivity patterns at theta frequency band for single-digit arithmetic and may provide new insights into the dissociable neural mechanisms underlying single-digit addition and multiplication.3)Differential recruitment of language-related networks in multiplication and number Sternberg task.The prevailing model for numerical cognition proposed that simple multiplication is solved by arithmetic fact retrieval and relies on the verbal-phonological code for number representation.Retrieval of multiplication facts is subserved by word associations(e.g.,"?????").This automatic speech production places little demand for semantic processing but more demand for phonological processing.On the other hand,behavioral studies show that when digital naming task and multiplication task mixed in the same block,due to the involvement of verbal-phonological code in multiplication,the semantic route of the digital naming task is suppressed.If execution of the task mixed with multiplication needs access semantic representation of number,according to the theoretical framework of controlled semantic cognition(CSC),the task will pursuit stronger input from semantic control network than multiplication for access to the semantic representation of numbers.Theta frequency band is associated cognitive control.And there are studies suggested"binding"of words and sentences in language is associated with beta frequency band.Accordingly,this study first explored whether different number codes were implicated in multiplication and number Sternberg task during number encoding by using EEG indexes of specific frequency bands suggested in previous research.By analyzing oscillatory EEG activity in theta(5–7Hz)and beta frequency(15–17 Hz)bands,we found different patterns of oscillatory brain activity between multiplication and number Sternberg task.Experiment results showed a larger increase of theta-band power for number Sternberg than multiplication in the left frontal regions.In contrast,multiplication induced a larger increase of These results show that the relationship between phonological and semantic processing and different numerical cognitive tasks can be investigated by analyzing the oscillatory activities in specific frequency bands.Although numerical cognition is generally considered to be a domain-specific cognitive ability,its neural mechanisms can still be investigated based on phonological and semantic processing mechanisms.By exploration of cognitive neural mechanisms subserving normal adults' numerical processing,the results suggested that,even within the small scope of basic arithmetic,involvement of number representation depends on task type,and the cognitive processes implicated in arithmetic could induce dynamic reorganization of brain functional networks in specific frequency bands.In addition,although the numerical capability is considered independent of the general language and semantic ability,the cognitive process in numerical processing can still be explored based on language and semantic processing.These findings could contribute to improvement of the detailed functional model of numerical processing,so that people could understand the nature of numerical processing and its development trajectory more clearly.It also provides neuroimaging evidence for intervention and correction in individuals who struggle with learning of number and arithmetic,such as dyscalculia.