Differential contribution of frontal and temporal cortices to auditory change detection: fMRI and ERP results.

The present study addresses the functional role of the temporal and frontal lobes in auditory change detection. Prior event-related potential (ERP) research suggested that the mismatch negativity (MMN) reflects the involvement of a temporofrontal network subserving auditory change detection processes and the initiation of an involuntary attention switch. In the present study participants were presented with repetitive spectrally rich sounds. Infrequent changes of either small (10% change), medium (30% change), or large (100% change) magnitude were embedded in the stimulus train. ERPs and fMRI measures were obtained in the same subjects in subsequent sessions. Significant hemodynamic activation in the superior temporal gyri (STG) bilaterally and the opercular part of the right inferior frontal gyrus was observed for large and medium deviants only. ERPs showed that small deviants elicited MMN when presented in silence but not when presented with recorded MR background noise, indicating that small deviants were hardly detected under fMRI conditions. The MR signal change in temporal lobe regions was larger for large than for medium deviants. For the right fronto-opercular cortex the opposite pattern was observed. The strength of the temporal activation correlated with the amplitude of the change-related ERP at around 110 ms from stimulus onset while the frontal activation correlated with the change-related ERP at around 150 ms. These results suggest that the right fronto-opercular cortex is part of the neural network generating the MMN. Three alternative explanations of these findings are discussed.     

Functional neuroanatomy of auditory mismatch processing: an event-related fMRI study of duration-deviant oddballs

This study was designed to identify the neural networks underlying automatic auditory deviance detection in 10 healthy subjects using functional magnetic resonance imaging. We measured blood oxygenation level-dependent contrasts derived from the comparison of blocks of stimuli presented as a series of standard tones (50 ms duration) alone versus blocks that contained rare duration-deviant tones (100 ms) that were interspersed among a series of frequent standard tones while subjects were watching a silent movie. Possible effects of scanner noise were assessed by a "no tone" condition. In line with previous positron emission tomography and EEG source modeling studies, we found temporal lobe and prefrontal cortical activation that was associated with auditory duration mismatch processing. Data were also analyzed employing an event-related hemodynamic response model, which confirmed activation in response to duration-deviant tones bilaterally in the superior temporal gyrus and prefrontally in the right inferior and middle frontal gyri. In line with previous electrophysiological reports, mismatch activation of these brain regions was significantly correlated with age. These findings suggest a close relationship of the event-related hemodynamic response pattern with the corresponding electrophysiological activity underlying the event-related "mismatch negativity" potential, a putative measure of auditory sensory memory.     

On the functional role of temporal and frontal cortex activation in passive detection of auditory deviance

The superior temporal cortex (STC) and inferior frontal cortex (IFC) are active during pre-attentive change detection. According to one influential model, the temporal cortex is responsible for memory trace comparison and the frontal cortex for attention switching. However, fMRI studies that used parametric designs revealed frontal cortex activity that is inconsistent with this model. In response, alternative accounts of frontal cortex activity, such as contrast enhancement and response inhibition, have been suggested. In this study, we measured the event related potential (ERP) and event related optical signal (EROS) responses elicited by pitch deviants in a parametric design. The ERP results revealed the typical modulation of mismatch negativity (MMN) amplitude by degree of deviance. The EROS results showed a similar modulation effect in the temporal cortex and a general temporal cortex followed by frontal cortex activation pattern. Interestingly, medium deviants elicited a greater frontal EROS response than did large or small deviants. Moreover, regression analyses showed that the EROS measures, specifically the linear trend in the temporal cortex and the inverse quadratic trend in the frontal cortex, correlated with the linear trend of the ERP MMN response. Taken together, these results indicate that 1) deviance magnitude modulates the brain activity elicited by pitch stimuli in the STC and IFC within the same time range as electrophysiological measures of passive deviance detection, 2) EROS measures of deviance detection are highly correlated with the ERP MMN, and 3) the functional relationship of STC and IFC is consistent with both the contrast enhancement and response inhibition accounts of IFC activity in passive deviance detection.     

阅读半规则汉字时的脑激活模式:声调的作用

目的引入声调因素,运用功能磁共振成像技术进一步研究汉字规则性效应的脑激活模式.方法13名被试在磁共振扫描过程中执行视觉方式呈现的汉字出声阅读任务,根据形声字声旁与整字间读音及声调相同与否,将刺激材料细分为同音同调字、同音异调字、异音同调字和异音异调字,每类20字.结果四种条件均激活双侧额中回、额下回、前运动区及辅助运动区、左侧顶下小叶、双侧颞上回、双侧岛叶和右侧小脑,同时还各自激活了梭状回、颞中回、左内侧额叶等区域.另外,本实验还观察到这四种条件在右侧颞上回、双侧额下回等区域激活模式的特征性变化.结论存在汉字加工的半规则效应,声调的作用不应忽略.     

Prefrontal cortex involvement in preattentive auditory deviance detection: neuroimaging and electrophysiological evidence

Previous electrophysiological and neuroimaging studies suggest that the mismatch negativity (MMN) is generated by a temporofrontal network subserving preattentive auditory change detection. In two experiments we employed event-related brain potentials (ERP) and event-related functional magnetic resonance imaging (fMRI) to examine neural and hemodynamic activity related to deviance processing, using three types of deviant tones (small, medium, and large) in both a pitch and a space condition. In the pitch condition, hemodynamic activity in the right superior temporal gyrus (STG) increased as a function of deviance. Comparisons between small and medium and between small and large deviants revealed right prefrontal activation in the inferior frontal gyrus (IFG; BA 44/45) and middle frontal gyrus (MFG; BA 46), whereas large relative to medium deviants led to left and right IFG (BA 44/45) activation. In the ERP experiment the amplitude of the early MMN (90-120 ms) increased as a function of deviance, by this paralleling the right STG activation in the fMRI experiment. A U-shaped relationship between MMN amplitude and the degree of deviance was observed in a late time window (140-170 ms) resembling the right IFG activation pattern. In a subsequent source analysis constrained by fMRI activation foci, early and late MMN activity could be modeled by dipoles placed in the STG and IFG, respectively. In the spatial condition no reliable hemodynamic activation could be observed. The MMN amplitude was substantially smaller than in the pitch condition for all three spatial deviants in the ERP experiment. In contrast to the pitch condition it increased as a function of deviance in the early and in the late time window. We argue that the right IFG mediates auditory deviance detection in case of low discriminability between a sensory memory trace and auditory input. This prefrontal mechanism might be part of top-down modulation of the deviance detection system in the STG.     

The functional anatomy of inspection time: an event-related fMRI study

Twenty healthy young adults underwent functional magnetic resonance imaging (fMRI) of the brain while performing a visual inspection time task. Inspection time is a forced-choice, two-alternative visual backward-masking task in which the subject is briefly shown two parallel vertical lines of markedly different lengths and must decide which is longer. As stimulus duration decreases, performance declines to chance levels. Individual differences in inspection time correlate with higher cognitive functions. An event-related design was used. The hemodynamic (blood oxygenation level-dependent; BOLD) response was computed as both a function of the eight levels of stimulus duration, from 6 ms (where performance is almost at chance) to 150 ms (where performance is nearly perfect), and a function of the behavioral responses. Random effects analysis showed that the difficulty of the visual discrimination was related to bilateral activation in the inferior fronto-opercular cortex, superior/medial frontal gyrus, and anterior cingulate gyrus, and bilateral deactivation in the posterior cingulate gyrus and precuneus. Examination of the time courses of BOLD responses showed that activation was related specifically to the more difficult, briefer stimuli and that deactivation was found across most stimulus levels. Functional connectivity suggested the existence of two networks. One comprised the fronto-opercular area, intrasylvian area, medial frontal gyrus, and the anterior cingulate cortex (ACC), possibly associated with processing of visually degraded percepts. A posterior network of sensory-related and associative regions might subserve processing of a visual discrimination task that has high processing demands and combines several fundamental cognitive domains. fMRI can thus reveal information about the neural correlates of mental events which occur over very short durations.     

颞叶躯体感觉中枢——脑磁源成像研究

目的利用脑磁源成像观察正常人在躯体感觉刺激时中枢的兴奋情况。方法研究包括10名正常志愿者。通过专用电刺激仪刺激手部皮肤,固定电流脉冲0.3ms,刺激间期0.5s,叠加1000次。用等电流偶极描述局灶性皮质活动,受试者的头部空间形态用球形模型化。结果体感刺激明显激活位于对侧中央前、后回的第一躯体感觉皮层和颞上回。颞叶ECD的潜伏期比第一躯体感觉中枢的长,ECD的强度较低。结论体感刺激激活对侧第一躯体感觉皮层,颞叶参与处理体感刺激。     

Neural mechanisms associated with attention to temporal synchrony versus spatial orientation: an fMRI study

Previous neuropsychological and functional imaging studies have suggested that the right hemisphere is crucially involved in spatial cognition. By contrast, much less is known about the putative left hemisphere specialization for aspects of temporal cognition. Accordingly, we studied with functional magnetic resonance imaging the neural mechanisms underlying attention to stimulus onset synchrony or orientational congruence with identical pairs of geometric figures. In each trial, two rhombuses were presented, each 4 degrees peripheral to a central fixation cross, in the left and right visual hemifields. In half of the trials, subjects were asked to judge and indicate via button presses whether the rhombuses appeared simultaneously. In the other half of the trials, subjects indicated whether the orientation of the rhombuses was the same (Factor 1, task, temporal synchrony, orientation). In half of the trials, subjects responded with their right hand and in the other half with their left hand (Factor 2, hand, right, left). Data were analyzed using SPM99 and a random-effects model. Attention to orientation differentially activated right temporo-occipital cortex. Attention to stimulus onset synchrony activated left anterior superior temporal gyrus, left inferior parietal cortex, left medial frontal gyrus, and right operculum. Activation of right temporo-occipital cortex for attention to stimulus orientation is in good agreement with previous functional neuroimaging studies of stimulus orientation. More importantly, activation of a predominantly left-hemispheric network with attention to stimulus onset synchrony extends the results of previous functional imaging, psychophysical, and neuropsychological studies of temporal processing.     

Spatiotemporal dynamics of audiovisual speech processing

The cortical processing of auditory-alone, visual-alone, and audiovisual speech information is temporally and spatially distributed, and functional magnetic resonance imaging (fMRI) cannot adequately resolve its temporal dynamics. In order to investigate a hypothesized spatiotemporal organization for audiovisual speech processing circuits, event-related potentials (ERPs) were recorded using electroencephalography (EEG). Stimuli were congruent audiovisual/ba/, incongruent auditory/ba/synchronized with visual/ga/, auditory-only/ba/, and visual-only/ba/and/ga/. Current density reconstructions (CDRs) of the ERP data were computed across the latency interval of 50-250 ms. The CDRs demonstrated complex spatiotemporal activation patterns that differed across stimulus conditions. The hypothesized circuit that was investigated here comprised initial integration of audiovisual speech by the middle superior temporal sulcus (STS), followed by recruitment of the intraparietal sulcus (IPS), followed by activation of Broca's area [Miller, L.M., d'Esposito, M., 2005. Perceptual fusion and stimulus coincidence in the cross-modal integration of speech. Journal of Neuroscience 25, 5884-5893]. The importance of spatiotemporally sensitive measures in evaluating processing pathways was demonstrated. Results showed, strikingly, early (<100 ms) and simultaneous activations in areas of the supramarginal and angular gyrus (SMG/AG), the IPS, the inferior frontal gyrus, and the dorsolateral prefrontal cortex. Also, emergent left hemisphere SMG/AG activation, not predicted based on the unisensory stimulus conditions was observed at approximately 160 to 220 ms. The STS was neither the earliest nor most prominent activation site, although it is frequently considered the sine qua non of audiovisual speech integration. As discussed here, the relatively late activity of the SMG/AG solely under audiovisual conditions is a possible candidate audiovisual speech integration response.     

The human temporal lobe integrates facial form and motion: evidence from fMRI and ERP studies

Physiological studies in humans and monkeys indicate that the posterior temporal cortex is active when viewing the movements of others. Here we tested the premise that this region integrates form and motion information by presenting both natural and line-drawn displays of moving faces and motion controls where motion was continuously presented in the same part of the visual field. The cortex in and near the STS and on the fusiform gyrus (FG) responded to both types of face stimuli, but not to the controls, in a functional magnetic resonance imaging study in 10 normal subjects. The response in the STS to both types of facial motion was equal in magnitude, whereas in the FG the natural image of the face produced a significantly greater response than that of the line-drawn face. In a subsequent recording session, the electrical activity of the brain was recorded in the same subjects to the same activation task. Significantly larger event-related potentials (ERPs) to both types of moving faces were observed over the posterior temporal scalp compared to the motion controls at around 200 ms postmotion onset. Taken together, these data suggest that regions of temporal cortex actively integrate form and motion information-a process largely independent of low-level visual processes such as changes in local luminance and contrast.     

Cerebral pathways in processing of affective prosody: a dynamic causal modeling study

This study was conducted to investigate the connectivity architecture of neural structures involved in processing of emotional speech melody (prosody). 24 subjects underwent event-related functional magnetic resonance imaging (fMRI) while rating the emotional valence of either prosody or semantics of binaurally presented adjectives. Conventional analysis of fMRI data revealed activation within the right posterior middle temporal gyrus and bilateral inferior frontal cortex during evaluation of affective prosody and left temporal pole, orbitofrontal, and medial superior frontal cortex during judgment of affective semantics. Dynamic causal modeling (DCM) in combination with Bayes factors was used to compare competing neurophysiological models with different intrinsic connectivity structures and input regions within the network of brain regions underlying comprehension of affective prosody. Comparison on group level revealed superiority of a model in which the right temporal cortex serves as input region as compared to models in which one of the frontal areas is assumed to receive external inputs. Moreover, models with parallel information conductance from the right temporal cortex were superior to models in which the two frontal lobes accomplish serial processing steps. In conclusion, connectivity analysis supports the view that evaluation of affective prosody requires prior analysis of acoustic features within the temporal and that transfer of information from the temporal cortex to the frontal lobes occurs via parallel pathways.     

多系统萎缩患者轻度认知功能障碍的静息态低频振幅研究

目的采用静息态功能磁共振成像(resting state functional MRI,rs-fMRI)低频振幅(amplitude of low-frequency fluctuation,ALFF)方法探究多系统萎缩(multiple system atrophy,MSA)患者认知相关的自发脑活动改变。材料与方法对29例认知功能正常的MSA患者(MSA-normal cognition,MSA-NC)、33例伴轻度认知功能障碍的MSA患者(MSA-mild cognitive impairment,MSA-MCI)与33名健康对照者(healthy control,HC)进行rs-fMRI扫描。应用ALFF方法比较各组间自发脑活动改变,并对患者组间存在差异脑区的ALFF值与认知评分进行相关性分析。结果与HC相比,MSA-NC在左侧角回及右侧颞中回出现ALFF增强;与HC相比,MSA-MCI在双侧背外侧前额叶、内侧前额叶、前扣带回、中扣带回出现ALFF减低,而在双侧颞下回、角回、左侧枕中回、右侧颞中回、楔前叶及右侧小脑、小脑蚓出现ALFF增强。与MSA-NC相比,MSA-MCI在右侧额叶皮层出现ALFF减低,并与蒙特利尔认知评估量表(montreal cognitive assessment scale,MoCA)评分呈正相关(r=0.531,P<0.05);在右侧小脑出现ALFF增强,并与MoCA评分呈负相关(r=-0.499,P<0.05)。结论MSA特异的轻度认知功能障碍是由小脑与额叶皮层损伤共同介导,其中小脑起到代偿作用。     

Change detection in children with autism: an auditory event-related fMRI study

Autism involves impairments in communication and social interaction, as well as high levels of repetitive, stereotypic, and ritualistic behaviours, and extreme resistance to change. This latter dimension, whilst required for a diagnosis, has received less research attention. We hypothesise that this extreme resistance to change in autism is rooted in atypical processing of unexpected stimuli. We tested this using auditory event-related fMRI to determine regional brain activity associated with passive detection of infrequently occurring frequency-deviant and complex novel sounds in a no-task condition. Participants were twelve 10- to 15-year-old children with autism and a group of 12 age- and sex-matched healthy controls. During deviance detection, significant activation common to both groups was located in the superior temporal and inferior frontal gyri. During 'novelty detection', both groups showed activity in the superior temporal gyrus, the temporo-parietal junction, the superior and inferior frontal gyri, and the cingulate gyrus. Children with autism showed reduced activation of the left anterior cingulate cortex during both deviance and novelty detection. During novelty detection, children with autism also showed reduced activation in the bilateral temporo-parietal region and in the right inferior and middle frontal areas. This study confirms previous evidence from ERP studies of atypical brain function related to automatic change detection in autism. Abnormalities involved a cortical network known to have a role in attention switching and attentional resource distribution. These results throw light on the neurophysiological processes underlying autistic 'resistance to change'.     

Spatiotemporal imaging of electrical activity related to attention to somatosensory stimulation

The aim of the present study was to localize the effects of spatial attention on somatosensory stimulation in EEG. Median and tibial nerve were stimulated at all four limbs in a random order. Subjects were instructed to count the events on either the right median or the right tibial nerve. Attention-induced changes in the somatosensory evoked potentials (SEP) were revealed by subtracting the median nerve SEPs recorded while subjects attended to stimuli applied to the tibial nerve from those obtained during attention to the stimulated hand. In a current density reconstruction approach source maxima in the time range from 30 to 260 ms after median nerve stimulation were localized and the time courses of activation were elaborated by dipole modeling. Six regions were identified which contribute significant source activity related to selective spatial attention: contralateral postcentral gyrus (Brodman area (BA) 3), contralateral mesial frontal gyrus (BA 6), right posterior parietal cortex (BA 7), anterior cingulate gyrus (BA 32), and bilateral middle temporal gyrus (BA 21). Activation started at the right posterior parietal cortex, followed by the contralateral middle temporal gyrus, probably representing SII activity, and the middle frontal and anterior cingulate gyrus. Similar regions of source activation were revealed by tibial nerve SEP, but the effect was less pronounced and restricted almost entirely to activation of the contralateral postcentral gyrus (BA 3), anterior cingulate gyrus (BA 32), and ipsilateral middle temporal gyrus (BA 21). Our data provide evidence for a spatially separated frontal generator within the anterior cingulum, dependent on selective attention in the somatosensory modality.     

Transient brain responses predict the temporal dynamics of sound detection in humans

The neural events leading up to the conscious experience of stimulus events have remained elusive. Here we describe stimulation conditions under which activation in human auditory cortex can be used to predict the temporal dynamics of behavioral sound detection. Subjects were presented with auditory stimuli whose energy smoothly increased from a silent to a clearly audible level over either 1, 1.5, or 2 s. Magnetoencephalographic (MEG) recordings were carried out in the passive and active recording conditions. In the active condition, the subjects were instructed to attend to the auditory stimuli and to press a response key when these became audible. In both conditions, the stimuli elicited a prominent transient response whose emergence is unexplainable by changes in stimulus intensity alone. This transient response was larger in amplitude over the right hemisphere and in the active condition. Importantly, behavioral sound detection followed this brain activation with a constant delay of 180 ms, and further the latency variations of the brain response were directly carried over to behavioral reaction times. Thus, noninvasively measured transient events in the human auditory cortex can be used to predict accurately the temporal course of sound detection and may therefore turn out to be useful in clinical settings.     

静息态脑功能磁共振成像在急性轻型脑外伤中的应用

目的 分析静息态脑功能磁共振成像在急性轻型脑外伤临床中的应用效果。 方法 选取北京博爱医院2019年5月至2021年5月收治的急性轻型脑外伤患者47例为观察组,同期行常规体检的健康人50例为对照组,采用静息态脑功能磁共振成像采集低频震荡幅度(ALFF),采用简易精神状态检查(MMSE)、蒙特利尔认知评定(MoCA)、Rivermead行为记忆功能测试(RBMT)进行评定。 结果 与对照组相比,观察组MMSE、MocA、RBMT评分均显著降低(t > 18.138, P < 0.001);观察组ALFF降低的脑区包括小脑后叶、小脑扁桃体、下半月小叶、右侧颞上回、右侧颞中回、右侧顶叶和右侧中央后回等,ALFF升高的脑区包括边缘叶、扣带回、楔前叶、左侧小脑、右侧颞上回、右侧颞中回、右侧额上回、右侧额中回和右侧额下回等。 结论 急性轻型脑外伤患者存在多个脑区异常改变,可能与认知障碍有关。     

Neuronal chronometry of target detection: fusion of hemodynamic and event-related potential data

Event-related potential (ERP) studies of the brain's response to infrequent, target (oddball) stimuli elicit a sequence of physiological events, the most prominent and well studied being a complex, the P300 (or P3) peaking approximately 300 ms post-stimulus for simple stimuli and slightly later for more complex stimuli. Localization of the neural generators of the human oddball response remains challenging due to the lack of a single imaging technique with good spatial and temporal resolution. Here, we use independent component analyses to fuse ERP and fMRI modalities in order to examine the dynamics of the auditory oddball response with high spatiotemporal resolution across the entire brain. Initial activations in auditory and motor planning regions are followed by auditory association cortex and motor execution regions. The P3 response is associated with brainstem, temporal lobe, and medial frontal activity and finally a late temporal lobe "evaluative" response. We show that fusing imaging modalities with different advantages can provide new information about the brain.     

Zoomed functional imaging in the human brain at 7 Tesla with simultaneous high spatial and high temporal resolution

Functional neuroimaging in the human brain using noninvasive magnetic resonance methods has the potential of providing highly resolved maps of neuronal activation. Decreasing the voxel size and obtaining simultaneously high temporal resolution is a major challenge and is mainly limited by sensitivity. Here, signal-to-noise gains at high magnetic fields (7 Tesla) and an optimized surface coil setup are combined with a novel approach for zoomed functional imaging in the visual cortex. For echoplanar imaging, the acquisition time and segmentation was shortened fourfold by using a reduced field-of-view. An adiabatic outer-volume suppression method, BISTRO, was used to obliterate signal outside the area-of-interest achieving effective suppression even for inhomogeneous B1-fields. A single-shot acquisition was performed at submillimeter resolution in the human brain, while simultaneously maintaining a high temporal resolution of 125 ms. Functional studies with and without field-of-view reduction were performed. Activation and percent change maps were compared with respect to spatial extent, t values and percentage changes of the BOLD contrast. The detection of functional activation was found to be equal within the inter-series variability for the two acquisition schemes. Thus, single-trial BOLD responses were detected for the first time robustly at a 500 x 500 microm2 in plane and 250 ms temporal resolution, significantly expanding the possibilities of event-related functional imaging in the human brain. The magnetization transfer effect induced by the outer-volume suppression pulses was investigated and found to be increased during neuronal activity.     

Trend detection via temporal difference model predicts inferior prefrontal cortex activation during acquisition of advantageous action selection

The process of accurately predicting which actions are associated with advantageous versus disadvantageous outcomes is an important function of daily life. An integral part of this process is being able to detect when the association between an action and an outcome changes. This investigation examined the hypothesis that the inferior prefrontal cortex is critical for the detection of trends and that a trend process derived from the temporal difference model accomplishes this detection. Nineteen normal right-handed volunteers completed 120 4-s trials of a Rock Paper Scissors (RPS) task during functional magnetic resonance imaging. Subjects acquired the selection of advantageous actions during the RPS task. Activations in the medial frontal gyrus (BA 10), left ventrolateral frontal gyrus (BA 11/47), and left pallidum were significantly higher during trials in which subjects acquired the advantageous action. The time course of individually derived trend detection functions was found to be time-locked to the hemodynamic changes in the inferior frontal gyrus. These findings are consistent with the hypothesis that the inferior prefrontal cortex computes a trend from previously experienced action-outcome sequences based on a value function derived from the temporal difference model.