Cerebral correlates of alerting, orienting and reorienting of visuospatial attention: an event-related fMRI study

The identification of brain systems contributing to different aspects of visuospatial attention is of both clinical and theoretical interest. Cued target detection tasks provide a simple means to dissociate attentional subcomponents, such as alerting, orienting or reorienting of attention. Event-related functional magnetic resonance imaging (fMRI) was used to study neural correlates of these distinct attentional processes. Volunteers were scanned while performing a centrally cued target detection task. Four different types of trials (no cue, neutral cue, valid cue and invalid cue trials) with targets appearing either in the right or left hemifield were randomly intermixed. Behaviourally, the data provided evidence for alerting, spatial orienting and reorienting of attention. Neurally, the alerting effect was seen in bilaterally increased extrastriatal blood oxygenation level-dependent (BOLD) activity in neutral as compared to no cue trials. Neural correlates of spatial orienting were seen in anterior cingulate cortex, which was more active during valid as compared to neutral cue trials. Neural correlates of reorienting of attention, that is, higher BOLD activity to invalid as compared to validly cued trials were evident in several brain regions including left and right intraparietal sulcus, right temporo-parietal junction and middle frontal gyrus bilaterally. The data suggest that frontal and parietal regions are specifically involved in reorienting rather than orienting attention to a spatial position. Alerting effects were seen in extrastriate regions which suggest that increased phasic alertness results in a top-down modulation of neural activity in visual processing areas.     

Selective attention modulates inferior frontal gyrus activity during action observation

Our ability to recognize the actions of others is subserved by a complex network of brain areas, including the inferior frontal gyrus (IFG), inferior parietal lobe (IPL) and superior temporal sulcus (STS). An unresolved issue is whether the activity within these regions requires top-down control or whether it arises relatively automatically during passive action observation. Here we used fMRI to determine whether cortical activity associated with action observation is modulated by the strategic allocation of selective attention. Participants observed moving and stationary images of reach-to-grasp hand actions, while they performed an attentionally demanding task at the fovea. We first defined regions-of-interest (ROIs) in the IFG, IPL and STS which responded to the perception of these actions. We then probed these ROIs while participants observed the identical, but now task-irrelevant, actions and instead performed an easy (low attentional load) or difficult (high attentional load) visual discrimination task. Our data indicate that the activity of the left IFG was consistently attenuated under conditions of high attentional load, while the remaining action observation areas remained relatively unaffected by attentional manipulations. The suppression of the left IFG was unique to the observation of hand actions, and did not occur during the observation of non-biological control stimuli, in the form of coherent dot motion. We propose that the left IFG is the site at which descending inhibitory processes affect the processing of observed actions, and that the attentional modulation of this region is responsible for filtering task-irrelevant actions during ongoing behavior.     

Genetic variation in nicotinic receptors affects brain networks involved in reorienting attention

Prior evidence suggests that a genetic variation in nicotinic receptors modulates visuospatial attention in humans. Brain areas contributing to this modulation are largely unknown. Here we investigate the influence of the nicotinic receptor gene CHRNA4 (rs 1044396) on brain networks involved in detecting unattended events. Subjects were genotyped and studied with functional magnetic resonance imaging while performing a cued target detection task with valid, neutral and invalid trials. Two brain areas within a core region of the attention network, the right temporoparietal junction, showed a genotype dependent modulation. CHRNA4 C/C homozygotes showed differentially higher neural activity in the right middle temporal gyrus when reorienting attention was required in invalid trials. In contrast, T/T homozygotes had stronger activations within the right superior temporal gyrus. An analysis of functional connectivity further revealed that these temporoparietal regions have a distinct connectivity pattern. The superior temporal gyrus recruited by T/T homozygotes shows stronger connections to temporal and parietal brain regions, which are primarily involved in shifting attention, independent of stimulus frequency. In contrast, the middle temporal gyrus exhibits stronger connections to the caudate nucleus, which is involved in detecting violations of expectations. These findings suggest that, depending on genotype, detection of stimuli outside the focus of attention is more driven by reorienting or by expectation signals.     

Neurobiological substrate of smoking-related attentional bias

Substance-dependent patients automatically and involuntarily allocate their attention to drug cues in the environment, a process referred to as attentional bias. Attentional bias is increased during periods of subjective craving and predictive of treatment outcome and relapse in substance dependence. Despite recent theoretical and clinical advances with regard to attentional bias, the underlying neurobiological mechanisms are largely unknown. The objective of the current study was to investigate the neural substrate of attentional bias and associated subjective craving in smokers. A group of smokers (n=20) and a group of age- and gender-matched nonsmoking controls (n=22) were recruited from the general population and participated in a single session of fMRI scanning while attentional processes were manipulated. Main outcome measures were blood oxygen level-dependent (BOLD) fMRI activation during an attentional bias paradigm and self-reported cigarette craving. Results of the current study show that the dorsal anterior cingulate cortex, the superior parietal gyrus, and the superior temporal gyrus were more strongly activated in smokers, as compared to controls, when they had to pay attention to task-relevant information (line counting) while smoking cues were present as distracters (attentional bias). Subjective craving measures during attentional bias correlated with brain activation in the insula and putamen. To our knowledge, this is the first controlled study that shows the brain regions involved in attentional bias in smokers. The current study demonstrates that brain regions contributing to top-down attentional processing are implicated in attentional bias in smokers, suggesting that smokers have to employ more attentional resources to focus on a standard cognitive task when smoking cues are present.     

Cue validity modulates the neural correlates of covert endogenous orienting of attention in parietal and frontal cortex

Parietal brain regions have been implicated in reorienting of visuospatial attention in location-cueing paradigms when misleading advance information is provided in form of a spatially invalid cue. The difference in reaction times to invalidly and validly cued targets is termed the "validity effect" and used as a behavioral measure for attentional reorienting. Behavioral studies suggest that the magnitude of the validity effect depends on the ratio of validly to invalidly cued targets (termed cue validity), i.e., on the amount of top-down information provided. Using fMRI, we investigated the effects of a cue validity manipulation upon the neural mechanisms underlying attentional reorienting using valid and invalid spatial cues in the context of 90% and 60% cue validity, respectively. We hypothesized that increased parietal activation would be elicited when subjects need to reorient their attention in a context of high cue validity. Behaviorally, subjects showed significantly higher validity effects in the high as compared to the low cue validity condition, indicating slower reorienting. The neuroimaging data revealed higher activation of right inferior parietal and right frontal cortex in the 90% than in the 60% cue validity condition. We conclude that the amount of top-down information provided by predictive cues influences the neural correlates of reorienting of visuospatial attention by modulating activation of a right fronto-parietal attentional network.     

儿童阻塞性睡眠呼吸暂停低通气综合征脑皮质厚度改变MRI研究

目的:利用皮质厚度分析技术探讨阻塞性睡眠呼吸暂停低通气综合征儿童脑皮质厚度异常.方法:收集OSAHS患儿16例,以及与OSAHS组年龄、性别相匹配的正常对照者13例,所有受试者进行头颅的3D T1 MRI扫描,采集数据通过FreeSurfer软件进行分割重建,并计算获得所有受试者各脑区的皮质厚度,以独立样本t检验进行病...     

fMRI reactivity to high-calorie food pictures predicts short- and long-term outcome in a weight-loss program

Behavioral studies have suggested that food cues have stronger motivating effects in obese than in normal-weight individuals, which may be a risk factor underlying obesity. Previous cross-sectional neuroimaging studies have suggested that this difference is mediated by increased reactivity to food cues in parts of the reward system in obese individuals. To date, however, only a few prospective neuroimaging studies have been conducted to examine whether individual differences in brain activation elicited by food cues can predict differences in weight change. We used functional magnetic resonance imaging (fMRI) to investigate activation in reward-system as well as other brain regions in response to viewing high-calorie food vs. control pictures in 25 obese individuals before and after a 12-week psychosocial weight-loss treatment and at 9-mo follow-up. In those obese individuals who were least successful in losing weight during the treatment, we found greater pre-treatment activation to high-calorie food vs. control pictures in brain regions implicated in reward-system processes, such as the nucleus accumbens, anterior cingulate, and insula. We found similar correlations with weight loss in brain regions implicated by other studies in vision and attention, such as superior occipital cortex, inferior and superior parietal lobule, and prefrontal cortex. Furthermore, less successful weight maintenance at 9-mo follow-up was predicted by greater post-treatment activation in such brain regions as insula, ventral tegmental area, putamen, and fusiform gyrus. In summary, we found that greater activation in brain regions mediating motivational and attentional salience of food cues in obese individuals at the start of a weight-loss program was predictive of less success in the program and that such activation following the program predicted poorer weight control over a 9-mo follow-up period.     

The activation of attentional networks

Alerting, orienting, and executive control are widely thought to be relatively independent aspects of attention that are linked to separable brain regions. However, neuroimaging studies have yet to examine evidence for the anatomical separability of these three aspects of attention in the same subjects performing the same task. The attention network test (ANT) examines the effects of cues and targets within a single reaction time task to provide a means of exploring the efficiency of the alerting, orienting, and executive control networks involved in attention. It also provides an opportunity to examine the brain activity of these three networks as they operate in a single integrated task. We used event-related functional magnetic resonance imaging (fMRI) to explore the brain areas involved in the three attention systems targeted by the ANT. The alerting contrast showed strong thalamic involvement and activation of anterior and posterior cortical sites. As expected, the orienting contrast activated parietal sites and frontal eye fields. The executive control network contrast showed activation of the anterior cingulate along with several other brain areas. With some exceptions, activation patterns of these three networks within this single task are consistent with previous fMRI studies that have been studied in separate tasks. Overall, the fMRI results suggest that the functional contrasts within this single task differentially activate three separable anatomical networks related to the components of attention.     

Neural networks underlying endogenous and exogenous visual-spatial orienting

The orienting of visual-spatial attention is fundamental to most organisms and is controlled through external (exogenous) or internal (endogenous) processes. Exogenous orienting is considered to be reflexive and automatic, whereas endogenous orienting refers to the purposeful allocation of attentional resources to a predetermined location in space. Although behavioral, electrophysiological and lesion research in both primates and humans suggests that separate neural systems control these different modes of orienting, previous human neuroimaging studies have largely reported common neuronal substrates. Therefore, event-related FMRI (ER-FMRI) was used to independently examine different components of the orienting response including endogenous facilitation, exogenous facilitation and inhibition of return (IOR). In contrast to previous studies, endogenous versus exogenous facilitation resulted in widespread cortical activation including bilateral temporoparietal junction, bilateral superior temporal gyrus, right middle temporal gyrus, right frontal eye field and left intraparietal sulcus. Conversely, IOR compared to endogenous facilitation resulted in only a single focus of activation in the left superior temporal gyrus. These findings suggest that endogenous orienting activates a large cortical network to achieve internally generated shifts of attentional resources versus the automatic orienting that occurs with exogenous cues. However, similar networks may mediate endogenous orienting and IOR. The activation of the temporoparietal junction suggests that it is involved in more effortful processes, such as endogenous orienting, as well as in attentional reorienting and locating targets. Current results are discussed in terms of the functional development of the visual-spatial attentional system.     

注意缺陷型和混合型注意缺陷多动障碍儿童在Go/Nogo任务中的脑fMRI

目的 探讨注意缺陷多动障碍(ADHD)注意缺陷型(ADHD-I)、混合型(ADHD-C)以及健康儿童在经典Go/Nogo抑制控制任务中脑功能激活的异同。方法 对19例ADHD-I(ADHD-I组)、21例ADHD-C(ADHD-C组)和25名健康儿童(HC组)进行Go/Nogo任务fMRI,采用SPM8软件处理功能数据,比较3组反应抑制和错误加工激活脑区的差异。结果 3组反应抑制差异的脑区主要位于左侧额下回和右侧额中回,ADHD-C在左侧额下回的脑激活水平高于ADHD-I(P<0.001);3组错误加工差异脑区主要位于右侧额上回,而ADHD-C组与ADHD-I组激活脑区差异无统计学意义(P=1.000)。结论 ADHD儿童在Go/Nogo任务中表现出的抑制控制脑功能受损,且ADHD-I和ADHD-C的反应抑制受损程度不同。     

Frontal cortical tissue composition in abstinent cocaine abusers: a magnetic resonance imaging study

Cocaine abusers exhibit impairment of executive cognitive functions that are mediated by the frontal cortex. This work tested for structural (i.e., tissue composition) abnormalities that may underlie such performance deficits. Research participants were cocaine abusers (n = 14) abstinent for 20 days and a non-drug-using comparison group (n = 11), who underwent magnetic resonance imaging (T1-weighted scans of the brain). Gray matter and white matter tissue densities were determined using voxel-based morphometry with small volume correction based on a priori hypotheses derived from functional imaging of the same subjects. Cocaine abusers had significantly lower gray matter tissue density than did the non drug users in 10 of 13 small volumes analyzed in the frontal cortex [bilateral anterior cingulate gyrus (infragenual and perigenual regions) and medial orbitofrontal cortex and the lateral orbitofrontal cortex and middle/dorsal cingulate gyrus in the right hemisphere]. No group differences were found in white matter density of the frontal cortex. These results extend our previous findings of defective frontal cortical activation (indexed by cerebral blood flow) in cocaine abusers to include abnormalities in gray matter tissue density in the same frontal cortical regions.     

Brain localization of attentional control in different age groups by combining functional and structural MRI

The present study used functional and structural MRI to investigate differences in neuronal substrates underlying shifts of attention in young and old subjects, studied with dichotic listening. Two different consonant-vowel syllables were presented and the subjects were instructed to attend to and report from either the left or right ear stimulus. Typically, a right-ear advantage is observed when attending to the right-ear stimulus, and a left-ear advantage when attending to the left-ear stimulus. The behavioral results showed that the old group had difficulties with attentional modulation of the right-ear advantage in the attend left condition. This is interpreted as a failure of an important aspect of attentional control; the top-down biasing of attention for selection of task-relevant stimulus. The fMRI results showed that an area in the left middle frontal gyrus was more activated in the young group compared to the old group in the attend left condition. The structural MRI data showed reduced gray matter density of the same area in the old group. Based on these converging findings, we suggest that the left middle frontal gyrus plays an important role in top-down biasing of selecting task-relevant stimuli, and to inhibit processing of task-irrelevant stimuli. To our knowledge, this is one of the first studies addressing the question on how age-related changes in attentional processing is reflected in both functional and structural differences in the brain.     

弱视儿童的MRI全脑皮层厚度分析

目的 利用皮层厚度分析技术探讨弱视患儿脑灰质发育的异常.方法 对11例弱视患儿和10名视力正常儿童行3D T1WI扫描,数据应用Freesurfer软件进行后处理,以双样本独立t检验进行病例组和对照组的全脑皮层厚度比较,将具有统计学意义(P<0.05)的像素在标准脑模板上生成伪彩图.选取像素阈值为500个相邻像素,分析弱视患者皮层厚度改变的区域.结果 弱视组在双侧中央前回、左侧距状回前部、左侧颞上回和右侧额中回、额上回皮层厚度大于对照组;而在双侧舌回、枕颞外侧回、顶上小叶的区域,对照组皮层厚度大于弱视组.结论 皮层厚度分析研究能够发现弱视患儿与视觉相关的大脑区域的灰质皮层发育异常,从而为探讨弱视相关的神经结构发育异常提供有用信息.     

膝骨性关节炎患者脑结构和功能变化的多模态MRI

目的  联合基于体素的形态学测量（VBM）技术和静息态功能磁共振成像（rs-fMRI）技术探究膝骨性关节炎（KOA）患者静息状态下脑灰质体积、脑神经元活动强度及基于种子点的功能连接强度改变,综合分析KOA相关异常脑网络。方法  前瞻性收集30例KOA患者（KOA组）及30例健康人（HC组）的3D高分辨率T1WI像和rs-fMRI图像,采用VBM、低频振幅、功能连接3种方法分析两组间脑灰质结构和功能数据差异。结果  与HC组相比,KOA组双侧梭状回、右侧颞中回低频振幅值增高,右侧楔前叶、右侧内侧前额叶皮质、左侧额中回低频振幅值减低（体素水平P<0.005,团块水平P<0.05）;右侧楔前叶、右侧顶下小叶、右侧初级视觉皮层、左侧颞中回、左侧中央后回灰质体积减小（体素水平P<0.002,团块水平P<0.05）;以右侧楔前叶为种子点,与右侧颞中回的功能连接增强,与左侧前扣带回、左侧背外侧前额叶皮质的功能连接降低（体素水平P<0.005,团块水平P<0.05）。结论  KOA患者感知皮层系统及联合皮层系统阵营均存在血氧水平依赖信号及灰质微结构的改变且有重叠,主要涉及视觉网络、感觉运动网络、默认状态网络、执行控制网络内及默认状态网络、执行控制网络、突显网络的部分脑区间,这可能提示KOA患者不仅处于慢性疼痛的病理状态,还伴有信息整合、注意力控制、情绪反应、情感解读等功能活动的异常。     

Towards a fronto-temporal neural network for the decoding of angry vocal expressions

Vocal expressions commonly elicit activity in superior temporal and inferior frontal cortices, indicating a distributed network to decode vocally expressed emotions. We examined the involvement of this fronto-temporal network for the decoding of angry voices during attention towards (explicit attention) or away from emotional cues in voices (implicit attention) based on a reanalysis of previous data (Frühholz, S., Ceravolo, L., Grandjean, D., 2012. Cerebral Cortex 22, 1107-1117). The general network revealed high interconnectivity of bilateral inferior frontal gyrus (IFG) to different bilateral voice-sensitive regions in mid and posterior superior temporal gyri. Right superior temporal gyrus (STG) regions showed connectivity to the left primary auditory cortex and secondary auditory cortex (AC) as well as to high-level auditory regions. This general network revealed differences in connectivity depending on the attentional focus. Explicit attention to angry voices revealed a specific right-left STG network connecting higher-level AC. During attention to a nonemotional vocal feature we also found a left-right STG network implicitly elicited by angry voices that also included low-level left AC. Furthermore, only during this implicit processing there was widespread interconnectivity between bilateral IFG and bilateral STG. This indicates that while implicit attention to angry voices recruits extended bilateral STG and IFG networks for the sensory and evaluative decoding of voices, explicit attention to angry voices solely involves a network of bilateral STG regions probably for the integrative recognition of emotional cues from voices.     

A hedonically complex odor mixture produces an attentional capture effect in the brain

A counter-intuitive property of many pleasant and attractive stimuli is that they are hedonically complex, containing both pleasant and unpleasant components. A striking example is the floral scent of natural jasmine, which may contain more than 6% of indole, a pure chemical which is usually rated as unpleasant. Using fMRI we investigate the hypothesis that the interaction between the pleasant and unpleasant components in the hedonically complex natural jasmine produces an attentional capture effect in the brain. First, to localize brain areas involved in selective attention to odor, we compared neural activity in response to jasmine without indole when participants explicitly and selectively attended to either its pleasantness or intensity, with neural activity when no selective attention was required. We then show that the superior frontal gyrus has increased activity both when selective attention is being paid to jasmine without indole, and also when no selective attention is required but an unpleasant component is added to it to produce a hedonically complex mixture. The attentional capture effect in the superior frontal gyrus by the mixture was related to the hedonic complexity of the mixture across subjects; could not be explained by salience, intensity, or pleasantness; and was specific to the superior frontal gyrus in that it was not found in other prefrontal areas activated by selective attention. The investigation supports the new hypothesis that the affective potency of stimuli with mixed pleasant and unpleasant components is related at least in part to the recruitment of mechanisms in the brain involved in attentional capture and enhancement.     

Practice-induced changes of brain function during visual attention: a parametric fMRI study at 4 Tesla

A parametric functional MRI (fMRI) study with three levels of task difficulty was performed to determine the effect of practice and attentional load on brain activation during visual attention tasks. Brief practice during repeat fMRI scanning (20 min) did not change performance accuracy or reaction times (RT), but decreased activation bilaterally in the inferior, middle, and superior frontal gyri, superior temporal gyrus, thalamus, and cerebellum. Increased attentional load decreased performance accuracy but not RT, and increased activation bilaterally in the inferior, posterior, and superior parietal cortices, thalamus, cerebellum, and frontal gyri. These changes suggest that practice decreases dependency on thalamus, cerebellum, and the frontal cortices for controlled task processing possibly due to increased efficiency of the attentional network. Since short-term practice-effects in the prefrontal cortex may be similar to attentional load-effects, studies of attentional load need to take practice effects into account.     

The interference of operant task performance by emotional distracters: an antagonistic relationship between the amygdala and frontoparietal cortices

This fMRI study investigates neural activity associated with the interfering effects of emotional distracters. While in the scanner, participants made simple motor responses to target stimuli that were preceded and followed by positive, negative, or neutral images. Despite instructions to disregard the pictorial images, participants were slower to respond in the presence of positive or negative relative to neutral distracters, and significantly slower for negative relative to positive distracters. Enhanced activity in the amygdala and visual cortex was evident during trials that included positive and negative distracters. In contrast, increased activity in inferior frontal gyrus (BA 47) was only observed during trials that involved negative distracters. Connectivity analysis showed that activity in right amygdala correlated with activity in cingulate gyrus, posterior cingulate, middle temporal cortex, and was negatively correlated with activity in lateral superior frontal gyrus, middle frontal/orbital gyrus, and parietal cortex. The pattern of neural activity observed was interpreted within the framework of current cognitive models of attention. During a task demonstrating behavioural interference in the context of emotional distracters, increased activity in neural regions implicated in emotional processing (the amygdala) was associated with reduced activity in regions thought to be involved in exerting attentional control over task-relevant sensory representations (a frontoparietal network).     

儿童注意缺陷多动障碍脑功能及功能连接研究

目的使用静息态功能磁共振成像技术研究注意缺陷多动障碍(attention deficit hyperactivity disorder,ADHD)儿童的大脑局域自发功能活动及功能连接。材料与方法对10例ADHD患儿及10例正常对照组儿童进行全脑扫描,获取静息态功能图像。计算得到每个被试的低频振幅(amplitude of low-frequence fluctuation,ALFF)参数图,进行基于体素的组间比较。选取ALFF与对照组有显著差异的脑区做种子点,得到该区域与其他脑区之间的功能连接强度参数图,采用相同的方法比较两组被试之间的差别。结果与正常对照组相比,ADHD患儿在前扣带回、前额叶、尾状核等脑区存在显著的ALFF升高,提示自发功能活动更加活跃。与对照组相比,以前扣带为种子点,ADHD儿童在双侧丘脑、岛叶及后扣带区域功能连接显著升高;以右侧前额叶的脑区为种子点,ADHD的右侧中央前回和颞上回的功能连接下降;以尾状核为种子点,ADHD在双侧的额中回功能连接下降。结论 ADHD儿童局域脑区自发功能活动及其功能连接异常,揭示ADHD症状与认知注意网络的发育延迟或缺损有关。     

fMRI of thermal pain: effects of stimulus laterality and attention.

Brain activity was studied by fMRI in 18 healthy subjects during stimulation of the thenar eminence of the hand with either warm (non-painful, 40 degrees C) or hot (painful, 46-49 degrees C) stimuli using a contact thermode. Experiments were performed on the right and left hand independently and with two attentional contexts: subjects either attended to pain or attended to a visual global motion discrimination task (to distract them from pain). Group analysis demonstrated that attended warm stimulation of the right hand did not produce any significantly activated clusters. Painful thermal stimulation of either hand elicited significant activity over a large network of brain regions, including insula, inferior frontal gyrus, cingulate gyrus, secondary somatosensory cortex, cerebellum, and medial frontal gyrus (corrected P < 0.05). Insula activity was distributed along its anterior-posterior axis and depended on the hand stimulated and attentional context. In particular, activity within the posterior insula was contralateral to the site of stimulation, tested using regions of interest (ROI) analysis: significant side x site interaction (P = 0.001). With attention diverted from the painful stimulus bilateral anterior insula activity moved posteriorly to midinsula and decreased in extent (ROI analysis: significant main effect of attention (P = 0.03)). The role of the insula in thermosensation and attention is discussed.