Left Inferior Frontal Areas Research Articles

Assessing attentional task-related electroencephalogram signal variations by using mobile electroencephalogram technology: An experimental study.

A better understanding of the network responses of cortical activities during rest and cognitive tasks is necessary. Therefore, in this study, we aimed to evaluate cerebral activities during attentional tasks by using mobile electroencephalography, identifying the types of attentional components and brain waves. In this experimental study, we enrolled 12 healthy young adults. The attentional tasks comprised parts A and B of the Trail-Making Test (TMT). Nineteen electroencephalography electrodes were placed over various brain regions. The Wilcoxon signed-rank test was used to examine the differences in power levels between the rest and TMT conditions. During TMT part A, the electroencephalography power level of the delta waves was significantly higher in the right frontal, left central, left occipital, left inferior frontal, right mid-temporal, right posterior temporal, and middle parietal areas (P < .05) than those during the resting state; that of the alpha waves was significantly lower in the left posterior temporal area (P = .006); and that of the high gamma waves was significantly lower in the left parietal (P = .05) and left occipital (P = .002) areas. During TMT part B, the electroencephalography power level of the beta waves was significantly higher in the right frontal area (P = .041) than that during the resting state, and that of the low gamma waves was significantly higher in the left frontal pole, right frontal, and right inferior frontal areas (P < .05). During the focused attentional task, the power level of the delta waves increased and that of the alpha waves decreased, and during the alternating attentional task, those of both the beta and gamma waves increased. The delta waves were related to the whole brain, the alpha and high gamma waves to the left posterior lobe, and the beta and low gamma waves to both frontal lobes. These findings contribute to the basic knowledge necessary to develop new attentional assessment methods for clinical situations.

Classification of autism based on short-term spontaneous hemodynamic fluctuations using an adaptive graph neural network

Background:Short-term spontaneous hemodynamic fluctuations were collected by the functional near-infrared spectroscopy (fNIRS) system to classify children with autism spectrum disorder (ASD) and typical development (TD), and to explore abnormalities in the left inferior frontal gyrus in ASD. Methods:Using the fNIRS data of 25 children with ASD and 22 children with TD, a graph neural network combined with the temporal convolution module and the graph convolution module was used, to extract the spatio-temporal features of the data and achieve accurate classification of ASD. Results:The graph neural network was used to obtain a good classification result in the left inferior frontal gyrus, with an accuracy of 97.1%, precision of 95.1%, and specificity of 93.4%. It was found that the 5th channel (which is located in BA 10) and the 8th channel (which is located in BA 47) in the left inferior frontal gyrus were closely correlated with ASD. Comparison with previously used method(s):Compared with the previous deep learning model using the same input, the accuracy of our model has increased by up to 13%, and the correlation between channels in the left inferior frontal gyrus area with the best classification effect was explored through the graph neural network. Conclusion:The adaptive graph neural network (AGNN) model may be able to mine more valuable information to distinguish ASD from TD and in addition, the left inferior frontal gyrus may have greater investigative value.

Brain Areas Critical for Picture Naming: A Systematic Review and Meta-Analysis of Lesion-Symptom Mapping Studies.

Lesion-symptom mapping (LSM) studies have revealed brain areas critical for naming, typically finding significant associations between damage to left temporal, inferior parietal, and inferior fontal regions and impoverished naming performance. However, specific subregions found in the available literature vary. Hence, the aim of this study was to perform a systematic review and meta-analysis of published lesion-based findings, obtained from studies with unique cohorts investigating brain areas critical for accuracy in naming in stroke patients at least 1 month post-onset. An anatomic likelihood estimation (ALE) meta-analysis of these LSM studies was performed. Ten papers entered the ALE meta-analysis, with similar lesion coverage over left temporal and left inferior frontal areas. This small number is a major limitation of the present study. Clusters were found in left anterior temporal lobe, posterior temporal lobe extending into inferior parietal areas, in line with the arcuate fasciculus, and in pre- and postcentral gyri and middle frontal gyrus. No clusters were found in left inferior frontal gyrus. These results were further substantiated by examining five naming studies that investigated performance beyond global accuracy, corroborating the ALE meta-analysis results. The present review and meta-analysis highlight the involvement of left temporal and inferior parietal cortices in naming, and of mid to posterior portions of the temporal lobe in particular in conceptual-lexical retrieval for speaking.

The Development of Left Hemisphere Lateralization for Sentence-Level Prosodic Processing.

The fine-tuning of linguistic prosody in later childhood is poorly understood, and its neurological processing is even less well studied. In particular, it is unknown if grammatical processing of prosody is left- or right-lateralized in childhood versus adulthood and how phonological working memory might modulate such lateralization. Furthermore, it is virtually unknown how prosody develops neurologically among children with cochlear implants (CIs). Normal-hearing (NH) children ages 6-12 years and NH adults ages 18-28 years completed a functional near-infrared spectroscopy neuroimaging task, during which they heard sentence pairs and judged whether the sentences did or did not differ in their overall prosody (declarative, question, with or without narrow focus). Children also completed standard measures of expressive and receptive language. Age group differences emerged; children exhibited stronger bilateral temporoparietal activity but reduced left frontal activation. Furthermore, children's performance on a nonword repetition test was significantly associated with activation in the left inferior frontal gyrus-an area that was generally more activated in adults than in children. The prosody-related findings are generally consistent with prior neurodevelopmental works on sentence comprehension, especially those involving syntax and semantics, which have also noted a developmental shift from bilateral temporal to left inferior frontal regions typically associated with increased sensitivity to sentence structure. The findings thus inform theoretical perspectives on brain and language development and have implications for studying the effects of CIs on neurodevelopmental processes for sentence prosody. https://doi.org/10.23641/asha.22255996.

White Matter Microstructural Abnormalities and Cognitive Functions Assessment in First versus Multiple episodes of Euthymic Bipolar Cases

Background: Recently, several studies have detected cognitive impairment and microstructural anomalies of white matter (WM) in bipolar disorder type I (BD-I). It is still unclear if these structural and cognitive anomalies in BD are progressive or static. Subjects and Methods: We investigated Diffusion Tensor Imaging (DTI) derived fractional anisotropy (FA) and cognitive functions in 40 cases with euthymic BD I, who were subdivided into 20 cases with single episode and another 20 cases with multiple episodes, and were further compared with 20 healthy controls. Four tracts bilaterally (cingulum, inferior longitudinal fasciculus, superior longitudinal fasciculus, and uncinate fasciculus) and three areas (left rostral anterior cingulate, right inferior frontal area, and right subgenual anterior cingulate) were studied. The findings were further correlated with cognitive functions (memory, executive functions, and sustained attention), which were assessed using Trail Making Test A and B, Wisconsin Card Sorting Test, Wechsler Memory Scale, and Continuous Performance Test). Results: Cases with BD I either with a single episode or multiple episodes showed deficits than the control group in all the selected regions except right subgenual anterior cingulate in comparison to controls. Also, more deficits were found as regards cognitive functions. On the other hand, cases with many episodes had lower FA than those with a single episode regarding seven regions of interest (left and right inferior longitudinal fasciculus, left and right superior longitudinal fasciculus, left uncinate fasciculus, right cingulum, and right inferior frontal area) as well as more impairment in executive functions and sustained attention which correlated with these white matter abnormalities. Discussion and Conclusion: The present findings indicate that white matter microstructural abnormalities and cognitive functions deficits could serve as state and trait markers in cases with BD I. The detected abnormalities could affect the future in early diagnosis and intervention, thus facilitating functional recovery in cases with BD I.

Neuromodulation of verb-transitivity judgments

This study aimed to further clarify the roles of the temporal and frontal lobes of the brain in the processing of verb argument structure. Left inferior frontal brain areas have long been considered important for sentence processing, but recent research links left posterior temporal cortex to knowledge of verb argument structure. We applied cathodal High-Definition transcranial Direct Current Stimulation to 45 participants in a between-subjects design, with 15 participants each for inferior-frontal-cortex stimulation, posterior-temporal-cortex stimulation, and sham stimulation. Set up as a training task during stimulation, participants made overt judgments on the number of participant roles associated with individual verbs. Stimulation of posterior temporal cortex did not yield results that were different from sham stimulation, speeding up task responses overall. By contrast, stimulation of inferior frontal cortex yielded differential results for intransitive versus transitive verbs, speeding up responses to intransitive verbs and increasing accuracy to transitive verbs, relative to other conditions. The transitivity effect, specific to inferior frontal stimulation, suggests a role for inferior frontal cortex in access to verb-argument-structure information, possibly specific to situations of high cognitive load and in which participant roles have to be established for production, as opposed to comprehension.

Longitudinal Changes in Structural Connectivity in Young People at High Genetic Risk for Bipolar Disorder.

Recent studies of patients with bipolar disorder or at high genetic risk reveal structural dysconnections among key brain networks supporting cognitive and affective processes. Understanding the longitudinal trajectories of these networks across the peak age range of bipolar disorder onset could inform mechanisms of illness onset or resilience. Longitudinal diffusion-weighted MRI and phenotypic data were acquired at baseline and after 2 years in 183 individuals ages 12-30 years in two cohorts: 97 unaffected individuals with a first-degree relative with bipolar disorder (the high-risk group) and 86 individuals with no family history of mental illness (the control group). Whole-brain structural networks were derived using tractography, and longitudinal changes in these networks were studied using network-based statistics and mixed linear models. Both groups showed widespread longitudinal changes, comprising both increases and decreases in structural connectivity, consistent with a shared neurodevelopmental process. On top of these shared changes, high-risk participants showed weakening of connectivity in a network encompassing the left inferior and middle frontal areas, left striatal and thalamic structures, the left fusiform, and right parietal and occipital regions. Connections among these regions strengthened in the control group, whereas they weakened in the high-risk group, shifting toward a cohort with established bipolar disorder. There was marginal evidence for even greater network weakening in those who had their first manic or hypomanic episode before follow-up. Neurodevelopment from adolescence into early adulthood is associated with a substantial reorganization of structural brain networks. Differences in these maturational processes occur in a multisystem network in individuals at high genetic risk of bipolar disorder. This may represent a novel candidate to understand resilience and predict conversion to bipolar disorder.

Evaluation of a Simple Clinical Language Paradigm With Respect to Sensory Independency, Functional Asymmetry, and Effective Connectivity.

The present study replicates a known visual language paradigm, and extends it to a paradigm that is independent from the sensory modality of the stimuli and, hence, could be administered either visually or aurally, such that both patients with limited sight or hearing could be examined. The stimuli were simple sentences, but required the subject not only to understand the content of the sentence but also to formulate a response that had a semantic relation to the content of the presented sentence. Thereby, this paradigm does not only test perception of the stimuli, but also to some extend sentence and semantic processing, and covert speech production within one task. When the sensory base-line condition was subtracted, both the auditory and visual version of the paradigm demonstrated a broadly overlapping and asymmetric network, comprising distinct areas of the left posterior temporal lobe, left inferior frontal areas, left precentral gyrus, and supplementary motor area. The consistency of activations and their asymmetry was evaluated with a conjunction analysis, probability maps, and intraclass correlation coefficients (ICC). This underlying network was further analyzed with dynamic causal modeling (DCM) to explore whether not only the same brain areas were involved, but also the network structure and information flow were the same between the sensory modalities. In conclusion, the paradigm reliably activated the most central parts of the speech and language network with a great consistency across subjects, and independently of whether the stimuli were administered aurally or visually. However, there was individual variability in the degree of functional asymmetry between the two sensory conditions.

Trimodal processing of complex stimuli in inferior parietal cortex is modality-independent

In humans, multisensory mechanisms facilitate object processing through integration of sensory signals that match in their temporal and spatial occurrence as well as their meaning. The generalizability of such integration processes across different sensory modalities is, however, to date not well understood. As such, it remains unknown whether there are cerebral areas that process object-related signals independently of the specific senses from which they arise, and whether these areas show different response profiles depending on the number of sensory channels that carry information.To address these questions, we presented participants with dynamic stimuli that simultaneously emitted object-related sensory information via one, two, or three channels (sight, sound, smell) in the MR scanner. By comparing neural activation patterns between various integration processes differing in type and number of stimulated senses, we showed that the left inferior frontal gyrus and areas within the left inferior parietal cortex were engaged independently of the number and type of sensory input streams. Activation in these areas was enhanced during bimodal stimulation, compared to the sum of unimodal activations, and increased even further during trimodal stimulation.Taken together, our findings demonstrate that activation of the inferior parietal cortex during processing and integration of meaningful multisensory stimuli is both modality-independent and modulated by the number of available sensory modalities. This suggests that the processing demand placed on the parietal cortex increases with the number of sensory input streams carrying meaningful information, likely due to the increasing complexity of such stimuli.

M14. BDNF IS CORRELATE TO LOW EMOTION RECOGNITION IN UHR WOMEN: RESULTS FROM THE SSAPP POPULATIONAL UHR COHORT

BackgroundSchizophrenia is a disorder with prevalence rates of 1% in the general population. Science turned its efforts towards researching prodromal states, named “Ultra-high Risk” (UHR), in the hopes of impeding conversion to psychosis. Cognitive impairments are recognized among core features of schizophrenia and it is noted that they are already present at early stages of psychosis, such as ultra-high risk for psychosis (UHR). Schizophrenia in women has a more favorable outcome than in men with the disease in part mediated by cognitive performance. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), play crucial roles in the expression of synaptic plasticity underpinning cognitive function, particularly expression of learning and memory. Previous studies showed conflicting results regarding neurotrophin levels in patients with psychosis. We hypothesized that UHR individuals would also show altered BDNF and cognitive performance levels.MethodsA sample of over 2500 individuals aged between 18 and 30 years old, from the city of São Paulo, Brazil, was drawn and screened with the Prodromal Questionnaire (PQ). 236 subjects with high scores (18+ points in the positive PQ subscale) where selected for psychiatric assessment with the SIPS (Structured Interview for Psychosis-Risk Syndromes), and 98 individuals were classified as UHR. Whole blood sample was collected and BDNF levels were analyzed with ELISA kits (Thermo-Fisher). Cognitive performance was measured by the emotion recognition task available via the UPenn Computerized neuropsychological testing (). Data was available for 93 UHR individuals (95%) and for 62 (46%) controls. IBM SPSS Statistics v23 for Mac was used to analyze data.ResultsBDNF levels and performance on emotion recognition task did not differ between control and UHR individuals. Differences were also not found if sample was analyzed according to sex. However, in UHR women (63% of UHR sample), worse performance was significantly associated with a higher BDNF level (Pearson correlation coefficient=-0.288, p=0.031).DiscussionIn our study, we found a correlation of worse emotion recognition task and higher BDNF levels in UHR women. This might be due a compensatory mechanism in which patients more severely impaired at baseline show higher BDNF levels. Estrogen might play a role in this difference as it induces BDNF expression. Several studies with psychotic patients shows higher BDNF levels in affected individuals as well as one study with UHR individual show higher BDNF levels within this group, but none showed differences between sexes. One study showed that treatment with selective estrogen receptor raloxifene increased activation in the right hippocampus and left inferior frontal gyrus areas, which are involved in facial recognition.Overall, literature suggests that women outperform men regarding overall cognitive function, including emotion recognition. Our findings might be related to a before homeostasis state has been reached in which baseline measures for emotion recognition in UHR women could be worse than in men but along time ameliorated via estrogen-induced BDNF expression.

ERP Markers of Valence Coding in Emotional Speech Processing.

SummaryHow is auditory emotional information processed? The study's aim was to compare cerebral responses to emotionally positive or negative spoken phrases matched for structure and content. Twenty participants listened to 198 vocal stimuli while detecting filler phrases containing first names. EEG was recorded from 128 sites. Three event-related potential (ERP) components were quantified and found to be sensitive to emotional valence since 350 ms of latency. P450 and late positivity were enhanced by positive content, whereas anterior negativity was larger to negative content. A similar set of markers (P300, N400, LP) was found previously for the processing of positive versus negative affective vocalizations, prosody, and music, which suggests a common neural mechanism for extracting the emotional content of auditory information. SwLORETA applied to potentials recorded between 350 and 550 ms showed that negative speech activated the right temporo/parietal areas (BA40, BA20/21), whereas positive speech activated the left homologous and inferior frontal areas.

Hemispheric Dominance for Language and Side Effects in Mapping the Inferior Frontal Junction Area with Transcranial Magnetic Stimulation.

Language mapping by navigated transcranial magnetic stimulation (TMS) is commonly applied over the left language-dominant hemisphere to indicate the language-related cortex. Detailed language mapping of Broca's region including stimulation targets in the immediate vicinity to the premotor cortex may raise concern about confounding unspecific motor effects. We performed interhemispheric comparisons to delineate such possible unspecific effects from true TMS-induced language inhibition. Fifteen healthy German speakers named object pictures during navigated TMS over a left- and right-hemispheric target array covering the left inferior frontal junction area. Six mapping repetitions were conducted per hemisphere. Order of stimulation side was randomized between participants. Self-rating of discomfort was assessed after each stimulation; language errors and motor side effects were evaluated offline. Naming errors were observed significantly more frequently during left- than right-hemispheric stimulation. The same pattern was found for the most frequent error category of performance errors. Hierarchical cluster analyses of normalized ratings of error severity revealed a clear focus of TMS susceptibility for language inhibition in object naming at the dorsoposterior target sites only in the left hemisphere. We found no statistical difference in discomfort ratings between both hemispheres and also no interhemispheric difference in motor side effects, but we observed significantly stronger muscle contractions of the eyes as compared with the mouth. Our results of (1) unspecific pre-/motor effects similarly induced in both hemispheres, and (2) a specific focus of TMS susceptibility in the language-dominant hemisphere render any substantial contribution of nonlanguage-specific effects in TMS language mapping of the inferior frontal junction area highly unlikely.

Characterization of brain network supporting episodic memory in the absence of one medial temporal lobe.

How the brain supports normal episodic memory function without medial temporal lobe (MTL) structures has not been well characterized, which could provide clues for new therapeutic targets for people with MTL dysfunction‐related memory impairment. To characterize brain network supporting effective episodic memory function in the absence of unilateral MTL, we investigated the whole‐brain cortical interactions during functional magnetic resonance imaging memory encoding paradigms of words and figures in patients who showed a normal range of memory capacity following unilateral MTL resection and healthy controls (HC). Compared to the HC, the patients showed less activation in the left inferior frontal areas and right thalamus together with greater activation in the many cortical areas including the medial prefrontal cortex (mPFC). Task‐based functional connectivity (FC) analysis revealed that the mPFC showed stronger interactions with widespread brain areas in both patient groups, including the hippocampus contralateral to the resection. Moreover, the strength of the mPFC FC predicts the individual memory capacity of the patients. Our data suggest that hyperconnectivity of distributed brain areas, especially the mPFC, is a neural mechanism for memory function in the absence of one MTL.

Relationships between [¹⁸F]-THK5351 Retention and Language Functions in Primary Progressive Aphasia.

Background and PurposeThere are three distinct subtypes of primary progressive aphasia (PPA): the nonfluent/agrammatic variant (nfvPPA), the semantic variant (svPPA), and the logopenic variant (lvPPA). We sought to characterize the pattern of [18F]-THK5351 retention across all three subtypes and determine the topography of [18F]-THK5351 retention correlated with each neurolinguistic score.MethodsWe enrolled 50 participants, comprising 13 PPA patients (3 nfvPPA, 5 svPPA, and 5 lvPPA) and 37 subjects with normal cognition (NC) who underwent 3.0-tesla magnetic resonance imaging, [18F]-THK5351 positron-emission tomography scans, and detailed neuropsychological tests. The PPA patients additionally participated in extensive neurolinguistic tests. Voxel-wise and region-of-interest-based analyses were performed to analyze [18F]-THK5351 retention.ResultsThe nfvPPA patients exhibited higher [18F]-THK5351 retention in the the left inferior frontal and precentral gyri. In svPPA patients, [18F]-THK5351 retention was elevated in the anteroinferior and lateral temporal cortices compared to the NC group (left>right). The lvPPA patients exhibited predominant [18F]-THK5351 retention in the inferior parietal, lateral temporal, and dorsolateral prefrontal cortices, and the precuneus (left>right). [18F]-THK5351 retention in the left inferior frontal area was associated with lower fluency scores. Comprehension was correlated with [18F]-THK5351 retention in the left temporal cortices. Repetition was associated with [18F]-THK5351 retention in the left inferior parietal and posterior temporal areas, while naming difficulty was correlated with retention in the left fusiform and temporal cortices.ConclusionsThe pattern of [18F]-THK5351 retention was well matched with clinical and radiological findings for each PPA subtype, in agreement with the anatomical and functional location of each language domain.

Resting state functional connectivity and neural correlates of face-name encoding in patients with ischemic vascular lesions with and without the involvement of the left inferior frontal gyrus

Face-name association is a relevant ability for social interactions and involves the ventral and dorsolateral prefrontal cortices, particularly in the left hemisphere, bilateral hippocampal, fusiform gyrus and occipital regions. Previous studies demonstrated the primary role of the hippocampus for this ability in healthy subjects. However, no study has examined the participation of the left inferior frontal area, specially the left inferior frontal gyrus (LIFG) in patients with ischemic vascular lesions. In the present study we addressed this issue and investigated the neural correlates and resting state functional connectivity of face-name memory encoding in ischemic patients with LIFG or without lesions in the left IFG (nLIFG) and healthy controls (HC) using fMRI. The main results showed that the nLIFG group demonstrated efficient compensation related to encoding and performance on face-name learning and recognition memory task, in addition to similar brain areas activated during task performance compared to healthy controls. Some of these areas were more activated in nLIFG group, indicating a compensation mechanism. In contrast, the LIFG group showed worse behavior performance, and no signs of an efficient compensation mechanism. Functional connectivity analysis suggested that the left IFG region seems to be important for maintaining the connectivity of the right fusiform gyrus or, perhaps, lesion in this area is associated to maladaptive reorganization. Our findings highlight the relevant role of the left IFG in face-name learning and encoding, possibly as a primary region in addition to the bilateral hippocampal formation and fusiform gyrus.

Frequency and Chunking in Derived Words: A Parametric fMRI Study.

In usage-based linguistic theories, the assumption that high-frequency language strings are mentally represented as unitary chunks has been invoked to account for a wide range of phenomena. However, neurocognitive evidence in support of this assumption is still lacking. In line with Gestalt psychological assumptions, we propose that a language string qualifies as a chunk if the following two conditions are simultaneously satisfied: The perception of the whole string does not involve strong activation of its individual component parts, but the component parts in isolation strongly evoke the whole. Against this background, we explore the relationship between different frequency metrics and the chunk status of derived words (e.g., "government," "worthless") in a masked visual priming experiment with two conditions of interest. One condition investigates "whole-to-part" priming (worthless-WORTH), whereas the other one analyzes "part-to-whole" priming (tear-TEARLESS). Both conditions combine mixed-effects regression analyses of lexical decision RTs with a parametric fMRI design. Relative frequency (the frequency of the whole word relative to that of its onset-embedded part) emerges as the only frequency metric to correlate with chunk status in behavioral terms. The fMRI results show that relative frequency modulates activity in regions that have been related to morphological (de)composition or general task performance difficulty (notably left inferior frontal areas) and in regions associated with competition between whole, undecomposed words (right inferior frontal areas). We conclude that relative frequency affects early stages of processing, thereby supporting the usage-based concept of frequency-induced chunks.

Domain-specific and Domain-general Processing in Left Perisylvian Cortex: Evidence from Russian.

The processing of words containing inflectional affixes triggers morphophonological parsing and affix-related grammatical information processing. Increased perceptual complexity related to stem-affix parsing is hypothesized to create predominantly domain-general processing demands, whereas grammatical processing primarily implicates domain-specific linguistic demands. Exploiting the properties of Russian morphology and syntax, we designed an fMRI experiment to separate out the neural systems supporting these two demand types, contrasting inflectional complexity, syntactic (phrasal) complexity, and derivational complexity in three comparisons: (a) increase in parsing demands while controlling for grammatical complexity (inflections vs. phrases), (b) increase in grammatical processing demands, and (c) combined demands of morphophonological parsing and grammatical processing (inflections and phrases vs. derivations). Left inferior frontal and bilateral temporal areas are most active when the two demand types are combined, with inflectional and phrasal complexity contrasting strongly with derivational complexity (which generated only bilateral temporal activity). Increased stem-affix parsing demands alone did not produce unique activations, whereas grammatical structure processing activated bilateral superior and middle temporal areas. Selective left frontotemporal language system engagement for short phrases and inflections seems to be driven by simultaneous and interdependent domain-general and domain-specific processing demands.

Cortical dynamics during simple calculation processes: A magnetoencephalography study

ObjectiveWe elucidated active cortical areas and their time courses during simple calculation by using whole-scalp magnetoencephalography. MethodsTwelve healthy volunteers were asked to view meaningless figures (figure viewing) or digits (digit viewing) and add single digits (calculation). The magnetic signals of the brain were measured using a helmet-shaped 122-channel neuromagnetometer during the three tasks. ResultsThe occipital, inferior posterior temporal, and middle temporal areas of each hemisphere and the left superior temporal area (STA) were activated during all tasks (approximately 250ms after the stimulus onset). The calculation-related sources were located in the left inferior parietal area (IPA) in 8 subjects, right IPA in 5, left STA in 3, right STA in 5, right inferior frontal area in 2, and left inferior frontal area in 1. The IPA and STA of the left hemisphere were activated more strongly and significantly earlier than those of the right hemisphere: the left IPA was activated first (mean activation timing: 301ms), followed by activations of the left STA (369ms), right IPA (419ms), and right STA (483ms). ConclusionsSimple digit addition is executed mainly in the left IPA and left STA, followed by the recognition processes of results in the right IPA and right STA. SignificanceThis study clarified the cortical process during simple calculation, with excellent temporal and spatial resolution; the IPA and STA of the left hemisphere were activated more strongly and earlier than the corresponding areas of the right hemisphere.

Brain Signal Variability Differentially Affects Cognitive Flexibility and Cognitive Stability.

Recent neuroscientific research showed that the human brain signal is intrinsically variable and suggested that this variability improves performance. Computational models of prefrontal neural networks predict differential effects of variability for different behavioral situations requiring either cognitive flexibility or stability. However, this hypothesis has so far not been put to an empirical test. In this study, we assessed cognitive flexibility and cognitive stability, and, besides a generally positive effect of neural variability on accuracy measures, we show that neural variability in a prefrontal brain area at the inferior frontal junction is differentially associated with performance: higher levels of variability are beneficial for the effectiveness of task switching (cognitive flexibility) but detrimental for the efficiency of distractor inhibition (cognitive stability).

Neural mechanisms underlying word- and phrase-level morphological parsing

Abstract How is morphological and morphosyntactic information processed during sentence reading? Are the neural mechanisms underlying word- and phrase-level combinatorial processing overlapping or distinct? Here, electroencephalography (EEG) and magnetoencephalography (MEG) responses were recorded simultaneously during silent reading of Finnish sentences. The experimental conditions included 1) well-formed grammatical sentences (correct condition), 2) sentences containing morphosyntactic violations (adjective–noun number agreement violations), 3) morphological violations (incorrect stem allomorph and inflectional suffix combination), and 4) combined violations, containing both morphosyntactic and morphological violations. Signal space and source modeling results showed that morphosyntactic violations elicited a left anterior negativity effect, generated particularly in the left inferior frontal area. Morphological violations elicited a widespread negativity, resembling the N400. The neural sources of this negativity were localized most prominently to the right temporal cortical networks. Furthermore, all violations elicited P600 effects with similar widespread bilateral fronto-temporal neural generators that did not differ between morphosyntactic and morphological conditions. Our findings suggest at least partially distinct subnetworks in the fronto-temporal cortices for morphological and morphosyntactic parsing during the earlier stages of processes (∼400 ms post stimulus onset) and shared neural generators for the later processing stages.