Effects of emotional context on impulse control

High risk behaviors such as narcotic use or physical fighting can be caused by impulsive decision making in emotionally-charged situations. Improved neuroscientific understanding of how emotional context interacts with the control of impulsive behaviors may lead to advances in public policy and/or treatment approaches for high risk groups, including some high-risk adolescents or adults with poor impulse control. Inferior frontal gyrus (IFG) is an important contributor to response inhibition (behavioral impulse control). IFG also has a role in processing emotional stimuli and regulating emotional responses. The mechanism(s) whereby response inhibition processes interact with emotion processing in IFG are poorly understood. We used 4.7T fMRI in 20 healthy young adults performing a rapid event-related emotional Go/NoGo task. This task combined the Go/NoGo task, which is a classic means of recruiting response inhibition processes, with emotionally neutral and aversive distractor images. In IFG, both response inhibition in an emotionally neutral context (neutral NoGo trials) and aversive emotional picture processing (aversive Go trials) evoked activation greater than the simple response baseline (neutral Go trials). These results are consistent with the literature. Activation for response inhibition in aversive contexts (aversive NoGo-neutral Go trials) was approximately the sum of response inhibition activation (neutral NoGo-neutral Go) and aversive emotional distractor activation (aversive Go-neutral Go). We conclude that response inhibition and aversive emotional stimulus processing activities combine additively (linearly) in IFG, rather than interfering with each other (sub-linearly) or mutually-enhancing each other (super-linearly). We also found previously undocumented interaction effects between response inhibition (NoGo vs. Go) and emotional context (aversive vs. neutral distractor pictures) in bilateral posterior middle temporal gyrus and angular gyrus, right frontal eye field, and other brain regions. These results may reflect the interaction of attention processes driven by emotional stimuli with conflict resolution processes related to Go/NoGo performance.     

The time-course of single-word reading: evidence from fast behavioral and brain responses

We usually feel that we understand a familiar word "immediately". However, even basic aspects of the time-line of word recognition are still controversial. Different domains of research have still not converged on a coherent account. An integration of multiple sources of information would lead to more strongly constrained theoretical models, and help finding optimal measures when monitoring specific aspects of word recognition impairments in patient groups. In our multimodal approach--combining fast behavioral measures, ERPs and EEG/MEG source estimation--we provide converging evidence for the latencies of earliest lexical and semantic information retrieval in visual word recognition. Participants performed lexical and semantic decisions (LD, SD) in a Go/NoGo paradigm. We introduced eye-blink latencies as a dependent variable, in order to measure behavioral responses that are faster and less variable than traditional button presses. We found that the earliest behavioral responses distinguishing stimulus categories can occur around 310 ms. Ex-Gaussian analysis of behavioral responses did not reveal reliable differences between LD and SD. The earliest ERP differences between Go and NoGo conditions occurred around 160 ms for both LD and SD. Distributed source analysis of combined EEG/MEG data estimated neuronal generators for the lexicality effect around 200 ms in the left anterior middle temporal lobe. Thus, behavior and brain responses provide coherent evidence that the brain starts retrieving lexical and semantic information near-simultaneously within 200 ms of word onset. Our results support models of word recognition that assume a continuous accumulation of task-related information from the stimulus, which might be described by Bayesian principles.     

Two brain pathways for attended and ignored words

The dependency of word processing on spare attentional resources has been debated for several decades. Recent research in the study of selective attention has emphasized the role of task load in determining the fate of ignored information. In parallel to behavioral evidence, neuroimaging data show that the activation generated by unattended stimuli is eliminated in task-relevant brain regions during high attentional load tasks. We conducted an fMRI experiment to explore how word encoding proceeds in a high load situation. Participants saw a rapid series of stimuli consisting of overlapping drawings and letter strings (words or nonwords). In different blocks, task instructions directed attention to either the drawings or the letters, and subjects responded to immediate repetition of items in the attended dimension. To look at the effect of attention on word processing, we compared brain activations for words and nonwords under the two attentional conditions. As compared to nonwords, word stimuli drove responses in left frontal, left temporal and parietal areas when letters were attended. However, although the behavioral measures suggested that ignored words were not analyzed when drawings were attended, a comparison of ignored words to ignored nonwords indicated the involvement of several regions including left insula, right cerebellum and bilateral pulvinar. Interestingly, word-specific activations found when attended and ignored words were compared showed no anatomical overlap, suggesting a change in processing pathways for attended and ignored words presented in a high attentional load task.     

Timing and localization of movement-related spectral changes in the human peri-Rolandic cortex: intracranial recordings

Event-related spectral power (ERSP) was measured from intracranial EEG and used to characterize the time-course and localization of the Rolandic mu rhythms in 12 patients during the delayed recognition of words or faces (DR) and the discrimination of simple lateralized visual targets (LVD). On each trial, the subject decided whether to make manual response (Go) or not (NoGo). ERSP increased on both Go and NoGo trials in peri-Rolandic regions of all subjects with a peak latency of approximately 330-ms poststimulus and duration of 260 ms during the DR task. The peak of this ERSP increase preceded movement by approximately 300 ms. All subjects produced a subsequent movement specific ERSP decrease of peri-Rolandic mu rhythms (starting approximately 90 ms before the average reaction time) with an peak latency of approximately 800 ms and duration of approximately 520 ms. The LVD task produced bilateral movement-selective readiness potentials and reproduced the movement-specific late ERSP decreases seen in the DR task (strongest from 7-24 Hz). Furthermore, the LVD task demonstrated that the late movement-related ERSP decrease is larger for the contralateral hand. However, the LVD task did not consistently reproduce the early ERSP increase seen in the DR task. Movement-related ERSP decreases were widespread, occurring in pre- and post-Rolandic as well as primary-motor, supplemental motor, and cingulate cortical regions. Other cortical areas including frontal, temporal, and occipital regions did not show movement-related ERSP changes. Peri-Rolandic ERSP decreases in mu rhythms correlate with the generation of a motor command. The early increases in mu may reflect a transient state of motor inhibition just prior to motor execution.     

Cognitive Control in Generalized Anxiety Disorder: Relation of Inhibition Impairments to Worry and Anxiety Severity

Cognitive models of generalized anxiety disorder (GAD) propose that cognitive control, broadly construed, and inhibition specifically, play a role in the maintenance of GAD symptoms. However, few studies have explicitly investigated inhibition, and in particular “cold” (non-emotional) inhibition, and its relation to worry and anxiety severity in GAD. Adults with GAD (n?=?35) and healthy controls (n?=?21) completed computerized Stroop and Go/NoGo tasks, two widely-used tests of inhibition. GAD status predicted significantly worse (slower and less accurate) performance on the Stroop but not the Go/NoGo task. Clinician-rated anxiety severity predicted slower and less accurate Stroop performance over and above the effect of GAD diagnosis but did not predict Go/NoGo performance. Trait worry did not incrementally predict performance on either task. These findings provide qualified support for theoretical models of inhibition impairments in GAD and suggest that inhibition could be a promising target for novel neurocognitive interventions.     

儿童青少年反应抑制能力的发展:基于Go/NoGo任务的功能MRI研究

目的运用功能MRI(functional magnetic resonance imaging,f MRI)技术以及经典实验范式Go/No Go任务,探讨儿童青少年运动反应抑制(motor response inhibition)与错误监测(error processing)能力的发展。材料与方法 42名儿童青少年(8~17岁)在执行Go/No Go任务的同时,进行f MRI数据采集。使用SPSS和SPM8软件进行数据分析,并提取反应抑制关键脑区额下回与年龄作相关分析。结果随着年龄的增长,反应时间缩短,反应正确率提高。fMRI数据表明:对于成功反应抑制,在8~15岁期间,额下回激活强度与年龄呈显著正相关。然而,青春期后期额下回激活强度增加趋于平缓。对于错误监测,右侧额下回激活强度与年龄呈显著正相关。结论这些数据表明,额下回是反应抑制重要脑区之一,其在青春期前期随年龄而逐渐发育,青春期后期发育趋于平缓而逐渐成熟,接近成人水平。     

Electrophysiological evidence for the effect of interactive imagery on episodic memory: encouraging familiarity for non-unitized stimuli during associative recognition

Episodic memory depends upon multiple processes, including familiarity and recollection. Although associative recognition tasks are traditionally viewed as requiring recollection, recent research suggests a role for familiarity if to-be-remembered stimuli are perceived as unitized. Here we use event-related potentials (ERPs) to examine the relationship between stimulus properties and encoding strategy on the engagement of familiarity during associative recognition. Participants studied word pairs containing an association (e.g. traffic-jam) or an unassociated semantic relationship (e.g. violin-guitar), using either item or interactive imagery. At test, participants were required to recognize if word pairs were presented in the same pairing as study, were rearranged, or new. We hypothesized that adopting a strategy of interactive imagery during encoding (i.e. encouraging unitization) would enhance familiarity for unassociated word pairs but would have no effect on association pairs because they are already perceived as unitized. As expected, overall recognition performance was better for word pairs encoded with interactive imagery, and for association than semantic word pairs. ERPs recorded at test revealed an interaction between encoding strategy and stimulus properties. Association word pairs elicited similar bilateral frontal (familiarity) and left parietal (recollection) old/new effects following item and interactive imagery. By contrast, for semantic word pairs, the left parietal effect was equivalent across conditions, but the bilateral frontal effect was enhanced for the interactive imagery condition. The ERP results suggest that an encoding strategy of interactive imagery can enhance familiarity during associative recognition, but this effect is ultimately dependent on the properties of the stimuli to-be-remembered and the nature of the representations that underlie them.     

The influence of feedback valence in associative learning

The neural systems engaged by intrinsic positive or negative feedback were defined in an associative learning task. Through trial and error, participants learned the arbitrary assignments of a set of stimuli to one of two response categories. Informative feedback was provided on less than 25% of the trials. During positive feedback blocks, half of the trials were eligible for informative feedback; of these, informative feedback was only provided when the response was correct. A similar procedure was used on negative feedback blocks, but here informative feedback was only provided when the response was incorrect. In this manner, we sought to identify regions that were differentially responsive to positive and negative feedback as well as areas that were responsive to both types of informative feedback. Several regions of interest, including the bilateral nucleus accumbens, caudate nucleus, anterior insula, right cerebellar lobule VI, and left putamen, were sensitive to informative feedback regardless of valence. In contrast, several regions were more selective to positive feedback compared to negative feedback. These included the insula, amygdala, putamen, and supplementary motor area. No regions were more strongly activated by negative feedback compared to positive feedback. These results indicate that the neural areas supporting associative learning vary as a function of how that information is learned. In addition, areas linked to intrinsic reinforcement showed considerable overlap with those identified in studies using extrinsic reinforcers.     

Dissociable recruitment of rostral anterior cingulate and inferior frontal cortex in emotional response inhibition

The integrity of decision-making under emotionally evocative circumstances is critical to navigating complex environments, and dysfunctions in these processes may play an important role in the emergence and maintenance of various psychopathologies. The goal of the present study was to examine the spatial and temporal dynamics of neural responses to emotional stimuli and emotion-modulated response inhibition. High-density event-related brain potentials (ERPs) were measured as participants (N=25) performed an emotional Go/NoGo task that required button presses to words of a "target" emotional valence (i.e., positive, negative, neutral) and response inhibition to words of a different "distractor" valence. Using scalp ERP analyses in conjunction with source-localization techniques, we identified distinct neural responses associated with affective salience and affect-modulated response inhibition, respectively. Both earlier (approximately 300 ms) and later (approximately 700 ms) ERP components were enhanced with successful response inhibition to emotional distractors. Only ERPs to target stimuli differentiated affective from neutral cues. Moreover, source localization analyses revealed right ventral lateral prefrontal cortex (VLPFC) activation in affective response inhibition regardless of emotional valence, whereas rostral anterior cingulate activation (rACC) was potentiated by emotional valence but was not modulated by response inhibition. This dissociation was supported by a significant Region x Trial Type x Emotion interaction, confirming that distinct regional dynamics characterize neural responses to affective valence and affective response-inhibition. The results are discussed in the context of an emerging affective neuroscience literature and implications for understanding psychiatric pathologies characterized by a detrimental susceptibility to emotional cues, with an emphasis on major depressive disorder.     

Brain and behavioral indices of retrieval mode

In recent event-related potential (ERP) studies of episodic retrieval, ERPs have been acquired in tasks where participants have been cued trial-by-trial to prepare either to make episodic or semantic retrieval judgments. ERPs elicited during this preparatory cue period and separated according to retrieval task have diverged at right frontal scalp electrodes, with a relatively greater positivity associated with preparation for episodic rather than for semantic retrieval. Importantly, this pattern of differences has been observed only on 'stay' trials: those trials where the participant was cued to prepare for the same retrieval task on the previous trial. These findings have provided the basis for the proposal that the ERP modulations index processes that support the adoption or configuration of retrieval mode - a tonic process that can be sustained while recovery of episodic information is required and which facilitates the retrieval process. In these studies, however, the preparatory period on each trial was no more than 2000 ms, raising the possibility that, with more time available, neural correlates of these preparatory processes would not be restricted to stay trials. In this experiment, participants were cued trial-by-trial to complete either an episodic or a semantic retrieval task, and the preparatory period was greater than 4000 ms on the majority of trials. In keeping with previous findings, the ERPs elicited by these two cue types diverged principally on stay trials at right frontal electrode locations, suggesting that time to prepare is not the primary determinant of the onset of task-specific preparatory retrieval processing. In an important addition to previous findings, moreover, the accuracy of episodic memory judgments increased with the number of successive trials of the same task that participants completed, a finding consistent with the view that adopting a retrieval mode successfully can influence the accuracy of episodic memory judgments.     

Encoding activity in anterior medial temporal lobe supports subsequent associative recognition

The ability to bind information together, such as linking a name with a face or a car with a parking space, is a vital process in human episodic memory. To identify the neural bases for this binding process, we measured brain activity during a verbal associative encoding task using event-related functional MRI (fMRI), followed by an associative recognition test for the studied word pairs. Analysis of the encoding data sorted by the associative recognition accuracy allowed us to isolate regions involved in successfully creating associations. We found that encoding activity in bilateral anterior medial temporal lobe (MTL) regions was greater for successfully bound pairs, that is, those later recognized as intact, than for all other pairs. These findings provide evidence that the anterior medial temporal lobes support the successful binding of information in memory.     

Cortical lateralization during verb generation: a combined ERP and fMRI study

Lateralization of scalp-recorded event-related potentials (ERPs) and functional MRI (fMRI) activation was investigated using a verb generation task in 10 healthy right-handed adults. ERPs showed an early transient positivity in the left inferior temporal region (500-1250 ms) following auditory presentation of the stimulus noun. A sustained slow cortical negativity of later onset (1250-3000 ms) was then recorded, most pronounced over left inferior frontal regions. fMRI data were in agreement with both ERP effects, showing left lateralized activation in inferior and superior temporal as well as inferior frontal cortices. Lateralized ERP effects occurred during the verb generation task but not during passive word listening or during word- and nonword repetition. Thus, ERPs and fMRI provided convergent evidence regarding language lateralization, with ERPs revealing the temporal sequence of posterior to anterior cortical activation during semantic retrieval.     

Learning arbitrary visuomotor associations: temporal dynamic of brain activity.

Primates can give behavioral responses on the basis of arbitrary, context-dependent rules. When sensory instructions and behavioral responses are associated by arbitrary rules, these rules need to be learned. This study investigates the temporal dynamics of functional segregation at the basis of visuomotor associative learning in humans, isolating specific learning-related changes in neurovascular activity across the whole brain. We have used fMRI to measure human brain activity during performance of two tasks requiring the association of visual patterns with motor responses. Both tasks were learned by trial and error, either before (visuomotor control) or during (visuomotor learning) the scanning session. Epochs of tasks performance ( approximately 30 s) were alternated with a baseline period over the whole scanning session ( approximately 50 min). We have assessed both linear and nonlinear modulations in the differential signal between tasks, independently from overall task differences. The performance indices of the visuomotor learning task smoothly converged onto the values of a steady-state control condition, according to nonlinear timecourses. Specific visuomotor learning-related activity has been found over a distributed cortical network, centred on a temporo-prefrontal circuit. These cortical time-modulated activities were supported early in learning by the hippocampal/parahippocampal complex, and late in learning by the basal ganglia system. These findings suggest the inferior temporal and the ventral prefrontal cortex are critical neural nodes for integrating perceptual information with executive processes.     

Reduced P300 amplitude in a visual recognition task in patients with schizophrenia

We studied top-down visual processes in schizophrenia by analyzing visual event-related potentials (ERPs) during a gestalt recognition task, after subjects (patients with schizophrenia, n = 10; controls, n = 14) were trained to perceive three different geometrical shapes. Recognition performance of patients was poorer under both the figure and the nonfigure conditions then that of normal controls. ERPs analysis indicated that P300 amplitudes of the patients were significantly smaller than those of controls during correct figure detection trials. Moreover, topographical analysis of the differences in ERPs during the figure vs the nonfigure condition showed an earlier, more positive and more widely distributed P300 in controls than in patients with schizophrenia. Our study supports the misconnection hypothesis of schizophrenia and highlights the difficulty of the patients to refer to previous experience in order to filter incoming information. In a visual recognition task, this misconnection syndrome might induce a failure to integrate information stored in the frontal and prefrontal sites with incoming stimuli.     

不同言语加工水平受损的汉语失语症患者的事件相关电位

目的:本研究采用事件相关电位(ERPs)技术考察了汉语失语症患者言语产生过程中语义和语音的编码情况.方法:根据“汉语失语症心理语言评价(PACA)”得分结果将14例失语症患者分为词汇语义损伤、词汇通达障碍、词汇语音损伤3组不同言语加工水平损伤组,采用ERPs作为技术手段,实验任务为延迟命名,观察患者的脑电情况,记录15名健康人的脑电图作为对照.结果:词汇语义损伤为主的患者异常波幅出现在400ms以前,词汇通达障碍为主的患者异常波幅出现在介于400ms前后的时间窗,而词汇语音损伤为主的患者异常波幅出现在400ms以后的时间窗,每种类型其异常波幅出现的时间窗有较大的重叠.结论:ERPs可作为探讨汉语失语症病态内部语言的过程,以及辅助失语症评价的重要工具.     

Extracting a stimulus-unlocked component from EEG during NoGo trials of a Go/NoGo task

Like electroencephalographic (EEG) activity during reaction time tasks, EEG activity during tasks without overt responses may also consist of two components: stimulus-locked and -unlocked components. The extraction of such stimulus-unlocked components has been difficult owing to the unknown delays. Here, we propose a novel method to extract both of the two components from single-channel EEG epochs. In this method, we initially set random values for the delays and extract uncontaminated stimulus-locked and -unlocked components using the preset delays and a discrete Fourier transform. Then, we reconstruct the EEG by overlapping the extracted components with the preset delays, and calculate the residual errors between the reconstructed and original EEG. This procedure is repeated by updating the delays until the residual errors become adequately small. After verifying the performance of this method by two kinds of simulations with artificial and EEG data, we apply the method to EEG during NoGo trials of a Go/NoGo task, and obtain the stimulus-unlocked components, the magnitudes of which are comparable with those of the stimulus-locked components. By applying this method, it is possible to study internal and subjective brain activity, which occurs with variable delays.     

Proactive inhibitory control of movement assessed by event-related fMRI

Many neuronal processes play a role in the overall performance of inhibition tasks, often making it difficult to associate particular behavioral results to specific processes and structures. Indeed, in classical Go/NoGo, Stop or subliminal masked-prime tasks, inhibition is usually triggered at the same time as the sensorimotor processes involved in movement selection and conflict monitoring. To account for motor inhibition, many conflicting candidate structures, which depend on specific task requirements, have been proposed. In the present paper, first we used a simple reaction (RT) time task and, second, we took advantage of the fact that volitional inhibition is usually implemented before any stimulus occurs when subjects are aware that a warning signal will be presented before a target. This proactive inhibition would be intended to prevent anticipated responses and would be lifted as soon as the warning signal has been identified. In other words, we postulate that the same event does not trigger both inhibition and target processing, and that, indeed, these mechanisms can be separated in time. Event-related fMRI revealed that the medial prefrontal cortex and the inferior parietal cortex may be responsible for proactive inhibition, and that the primary motor cortex, the supplementary motor cortex and the putamen are the likely targeted sites of this inhibition. We conclude that executive control in these tasks may consist of switching from controlled inhibition (suppression of the neuronal processes underlying movement initiation) to automatic sensorimotor processing. The possible contribution of the medial prefrontal cortex to the tonic inhibition state adds new perspectives to possible meanings of a “default mode of brain function”.     

Dorsolateral prefrontal cortex involvement in memory post-retrieval monitoring revealed in both item and associative recognition tests

Post-retrieval monitoring is a process that contributes to episodic memory retrieval by allowing people to evaluate the relevance of retrieved information in relation to the task requirements. Previous studies have suggested that post-retrieval monitoring is supported by the dorsolateral prefrontal cortex (DLPFC). In this study, we used functional magnetic resonance imaging (fMRI) to evaluate involvement of the DLPFC in post-retrieval monitoring in two different recognition tests (item recognition and associative recognition). The item recognition memory test required subjects to make old/new judgments and the associative recognition memory test required them to make intact/rearranged judgments. Because the post-retrieval monitoring demand increases during old (hits) relative to new (correct rejections) item recognition trials, and also during rearranged (correct rejections) relative to intact (hits) associative recognition trials, we evaluated the brain activation associated with the interaction of Memory test (item versus associative) by Recognition trial (hit versus correct rejection). As expected, the DLPFC was activated in this interaction as well as for both old relative to new item recognition trials and rearranged relative to intact associative recognition trials. This study provides strong evidence that DLPFC activation supports post-retrieval monitoring across different types of recognition tasks.     

Quantifying additive evoked contributions to the event-related potential

Event-related potentials (ERPs) are widely used in basic neuroscience and in clinical diagnostic procedures. In contrast, neurophysiological insights from ERPs have been limited, as several different mechanisms lead to ERPs. Apart from stereotypically repeated responses (additive evoked responses), these mechanisms are asymmetric amplitude modulations and phase-resetting of ongoing oscillatory activity. Therefore, a method is needed that differentiates between these mechanisms and moreover quantifies the stability of a response. We propose a constrained subspace independent component analysis that exploits the multivariate information present in the all-to-all relationship of recordings over trials. Our method identifies additive evoked activity and quantifies its stability over trials. We evaluate identification performance for biologically plausible simulation data and two neurophysiological test cases: Local field potential (LFP) recordings from a visuo-motor-integration task in the awake behaving macaque and magnetoencephalography (MEG) recordings of steady-state visual evoked fields (SSVEFs). In the LFPs we find additive evoked response contributions in visual areas V2/4 but not in primary motor cortex A4, although visually triggered ERPs were also observed in area A4. MEG-SSVEFs were mainly created by additive evoked response contributions. Our results demonstrate that the identification of additive evoked response contributions is possible both in invasive and in non-invasive electrophysiological recordings.