Showing papers in "Cognitive, Affective, & Behavioral Neuroscience in 2007"
TL;DR: Whereas participation in the MBSR course improved the ability to endogenously orient attention, retreat participation appeared to allow for the development and emergence of receptive attentional skills, which improved exogenous alerting-related process.
Abstract: Mindfulness is defined as paying attention in the present moment. We investigate the hypothesis that mindfulness training may alter or enhance specific aspects of attention. We examined three functionally and neuroanatomically distinct but overlapping attentional subsystems: alerting, orienting, and conflict monitoring. Functioning of each subsystem was indexed by performance on the Attention Network Test (ANT; Fan, McCandliss, Sommer, Raz, & Posner, 2002). Two types of mindfulness training (MT) programs were examined, and behavioral testing was conducted on participants before (Time 1) and after (Time 2) training. One training group consisted of individuals naive to mindfulness techniques who participated in an 8-week mindfulness-based stress reduction (MBSR) course that emphasized the development of concentrative meditation skills. The other training group consisted of individuals experienced in concentrative meditation techniques who participated in a 1-month intensive mindfulness retreat. Performance of these groups was compared with that of control participants who were meditation naive and received no MT. At Time 1, the participants in the retreat group demonstrated improved conflict monitoring performance relative to those in the MBSR and control groups. At Time 2, the participants in the MBSR course demonstrated significantly improved orienting in comparison with the control and retreat participants. In contrast, the participants in the retreat group demonstrated altered performance on the alerting component, with improvements in exogenous stimulus detection in comparison with the control and MBSR participants. The groups did not differ in conflict monitoring performance at Time 2. These results suggest that mindfulness training may improve attention-related behavioral responses by enhancing functioning of specific subcomponents of attention. Whereas participation in the MBSR course improved the ability to endogenously orient attention, retreat participation appeared to allow for the development and emergence of receptive attentional skills, which improved exogenous alerting-related process.
1,402 citations
TL;DR: Juxtaposing the conflict-monitoring and decision-making accounts suggests an extension of the Conflict-Monitoring theory, by which conflict would act as a teaching signal driving a form of avoidance learning, to bias behavioral decision making toward cognitively efficient tasks and strategies.
Abstract: According to one influential account, the anterior cingulate cortex (ACC) serves to monitor for conflicts in information processing. According to another influential account, the ACC monitors action outcomes and guides decision making. Both of these perspectives are supported by an abundance of data, making it untenable to reject one view in favor of the other. Instead, the apparent challenge is to discover how the two perspectives might fit together within a larger account. In the present article, we consider the prospects for such a reconciliation. Juxtaposing the conflict-monitoring and decision-making accounts suggests an extension of the conflict-monitoring theory, by which conflict would act as a teaching signal driving a form of avoidance learning. The effect of this mechanism would be to bias behavioral decision making toward cognitively efficient tasks and strategies. We discuss evidence favoring this proposal and present an initial computational model, which lays the foundation for further development.
1,012 citations
TL;DR: Evidence that trial-to-trial changes in control engagement can be understood as driven by conflict detection and levels of activation of the ACC and the DLPFC in such tasks do indeed reflect conflict and control is reviewed.
Abstract: The dorsal anterior cingulate cortex (ACC) and associated regions of the medial frontal wall have often been hypothesized to play an important role in cognitive control. We have proposed that the ACC's specific role in cognitive control is to detect conflict between simultaneously active, competing representations and to engage the dorsolateral prefrontal cortex (DLPFC) to resolve such conflict. Here we review some of the evidence supporting this theory, from event-related potential (ERP) and fMRI studies. We focus on data obtained from interference tasks, such as the Stroop task, and review the evidence that trial-to-trial changes in control engagement can be understood as driven by conflict detection; the data suggest that levels of activation of the ACC and the DLPFC in such tasks do indeed reflect conflict and control, respectively. We also discuss some discrepant results in the literature that highlight the need for future research.
955 citations
TL;DR: A quantitative meta-analysis was performed on 47 neuroimaging studies involving tasks purported to require the resolution of interference, suggesting that resolution processes acting upon stimulus encoding, response selection, and response execution may recruit different neural regions.
Abstract: A quantitative meta-analysis was performed on 47 neuroimaging studies involving tasks purported to require the resolution of interference. The tasks included the Stroop, flanker, go/no-go, stimulus-response compatibility, Simon, and stop signal tasks. Peak density-based analyses of these combined tasks reveal that the anterior cingulate cortex, dorsolateral prefrontal cortex, inferior frontal gyrus, posterior parietal cortex, and anterior insula may be important sites for the detection and/or resolution of interference. Individual task analyses reveal differential patterns of activation among the tasks. We propose that the drawing of distinctions among the processing stages at which interference may be resolved may explain regional activation differences. Our analyses suggest that resolution processes acting upon stimulus encoding, response selection, and response execution may recruit different neural regions.
735 citations
TL;DR: It is argued that both conflict adaptation and feature integration contribute to the congruency sequence effect but that their respective contributions can be isolated experimentally and integrated into current models of cognitive control.
Abstract: Congruency effects in selective attention tasks are subject to sequential modulation: They are smaller following an incongruent stimulus than following a congruent one This congruency sequence effect has been interpreted as reflecting conflict-driven adjustments in cognitive control (conflict adaptation) or, alternatively, episodic memory effects of stimulus-response association (feature integration) The present article critically reviews support for these rival accounts in the experimental literature and discusses the implications thereof for assessing behavioral and neural signatures of cognitive control processes It is argued that both conflict adaptation and feature integration contribute to the congruency sequence effect but that their respective contributions can be isolated experimentally Studies that have pursued this isolation strategy have gained important insights into cognitive control processes Finally, other factors, such as expectancies, may also contribute to the congruency sequence effect, and thus their potential role needs to be carefully examined and, if found significant, integrated into current models of cognitive control
513 citations
TL;DR: The role of the midfrontal cortex in self-regulation allows us to consider both brain networks common to all people and network efficiency underlying individual differences in behavior.
Abstract: The midfrontal cortex, and particularly the anterior cingulate gyrus, appears active in many studies of functional imaging. Various models have competed to explain the functions of the anterior cingulate in relation to its patterns of activation. We believe that the concept of self-regulation is valuable in considering the role of the cingulate. The sensitivity of the cingulate to both reward and pain, and evidence for cingulate coupling to cognitive and emotional areas during task performance, support this identification. Self-regulation is a very broad concept that does not lend itself very well to specific models or tests, but it does provide a framework for examining development. We trace the role of the midfrontal cortex in evolution and infant development. Both genes and environment influence self-regulation. The presence of both genetic and environmental effects raises the issue of their interaction, which we discuss in relation to the dopamine 4 receptor gene and parenting methods. The role of the midfrontal cortex in self-regulation allows us to consider both brain networks common to all people and network efficiency underlying individual differences in behavior.
347 citations
TL;DR: This work proposes an emerging set of operating principles that govern this organization of the cortical systems that underpin complex cognition, characterizing the system as a set of collaborating cortical centers that operate as a large-scale cortical network.
Abstract: Recent findings in brain imaging, particularly in fMRI, are beginning to reveal some of the fundamental properties of the organization of the cortical systems that underpin complex cognition. We propose an emerging set of operating principles that govern this organization, characterizing the system as a set of collaborating cortical centers that operate as a large-scale cortical network. Two of the network's critical features are that it is resource constrained and dynamically configured, with resource constraints and demands dynamically shaping the network topology. The operating principles are embodied in a cognitive neuroarchitecture, 4CAPS, consisting of a number of interacting computational centers that correspond to activating cortical areas. Each 4CAPS center is a hybrid production system, possessing both symbolic and connectionist attributes. We describe 4CAPS models of sentence comprehension, spatial problem solving, and complex multitasking and compare the accounts of these models with brain activation and behavioral results. Finally, we compare 4CAPS with other proposed neuroarchitectures.
184 citations
TL;DR: These findings demonstrate the malleability of perceptual processes as a result of differences in cohort-specific experiences or in cultural exposure over time.
Abstract: Behavioral differences in the visual processing of objects and backgrounds as a function of cultural group are well documented. Recent neuroimaging evidence also points to cultural differences in neural activation patterns. Compared with East Asians, Westerners’ visual processing is more object focused, and they activate neural structures that reflect this bias for objects. In a recent adaptation study, East Asian older adults showed an absence of an object-processing area but normal adaptation for background areas. In the present study, 75 young and old adults (half East Asian and half Western) were tested in an fMR-adaptation study to examine differences in object and background processing as well as object—background binding. We found equivalent background processing in the parahippocampal gyrus in all four groups, diminished binding processes in the hippocampus in elderly East Asians and Westerners, and diminished object processing in elderly versus young adults in the lateral occipital complex. Moreover, elderly East Asians showed significantly less adaptation response in the object areas than did elderly Westerners. These findings demonstrate the malleability of perceptual processes as a result of differences in cohort-specific experiences or in cultural exposure over time.
157 citations
TL;DR: New fMRI results from an incentive change signal task now replicate the errorlikelihood effect, validate the further predictions of the computational model, and suggest why some segments of the population may fail to show an error- likelihood effect.
Abstract: The recently proposed error-likelihood hypothesis suggests that anterior cingulate cortex (ACC) and surrounding areas will become active in proportion to the perceived likelihood of an error. The hypothesis was originally derived from a computational model prediction. The same computational model now makes a further prediction that ACC will be sensitive not only to predicted error likelihood, but also to the predicted magnitude of the consequences, should an error occur. The product of error likelihood and predicted error consequence magnitude collectively defines the general “expected risk” of a given behavior in a manner analogous but orthogonal to subjective expected utility theory. New fMRI results from an incentive change signal task now replicate the errorlikelihood effect, validate the further predictions of the computational model, and suggest why some segments of the population may fail to show an error-likelihood effect. In particular, error-likelihood effects and expected risk effects in general indicate greater sensitivity to earlier predictors of errors and are seen in risk-averse but not risktolerant individuals. Taken together, the results are consistent with an expected risk model of ACC and suggest that ACC may generally contribute to cognitive control by recruiting brain activity to avoid risk.
155 citations
TL;DR: Functional magnetic resonance imaging was used to investigate the impact of increases in processing demand on selected cortical areas when participants performed a parametrically varied and challenging dual task and shed light on the differential implications of performance on activation patterns.
Abstract: What happens in the brain when we reach or exceed our capacity limits? Are there individual differences for performance at capacity limits? We used functional magnetic resonance imaging (fMRI) to investigate the impact of increases in processing demand on selected cortical areas when participants performed a parametrically varied and challenging dual task. Low-performing participants respond with large and load-dependent activation increases in many cortical areas when exposed to excessive task requirements, accompanied by decreasing performance. It seems that these participants recruit additional attentional and strategy-related resources with increasing difficulty, which are either not relevant or even detrimental to performance. In contrast, the brains of the high-performing participants "keep cool" in terms of activation changes, despite continuous correct performance, reflecting different and more efficient processing. These findings shed light on the differential implications of performance on activation patterns and underline the importance of the interindividual-differences approach in neuroimaging research.
138 citations
TL;DR: The present article reports ACC unit activity of monkeys performing two tasks and shows that the context created by a block design influences the encoding of reward values, even if no decision or choice is required.
Abstract: The anterior cingulate cortex (ACC) participates in evaluating actions and outcomes. Little is known on how action-reward values are processed in ACC and if the context in which actions are performed influences this processing. In the present article, we report ACC unit activity of monkeys performing two tasks. The first task tested whether the encoding of reward values is co ntext dependent-that is, dependent on the size of theother rewards that are available in the current block of trials. The second task tested whether unexpected events signaling a change in reward are represented. We show that the context created by a block design (i.e., the context of possible alternative rewards) influences the encoding of reward values, even if no decision or choice is required. ACC activity encodes the relative and not absolute expected reward values. Moreover, cingulate activitysignals and evaluates when reward expectations are violated by unexpected stimuli, indicating reward gains or losses.
TL;DR: Activity in an anterior rostral region of the medial prefrontal cortex was significantly greater for positive than for negative persons but did not show a valence effect for objects, which suggests that the arMPFC is tuned to social valence.
Abstract: The medial prefrontal cortex (MPFC) reliably activates in social cognition and reward tasks. This study locates distinct areas for each. Participants made evaluative (positive/negative) or social (person/not a person) judgments of pictured positive or negative people and objects in a slow event-related design. Activity in an anterior rostral region (arMPFC) was significantly greater for positive than for negative persons but did not show a valence effect for objects, and this was true regardless of the judgment task. This suggests that the arMPFC is tuned to social valence. Interestingly, however, no regions of the MPFC were found to be responsive to social information independently of valence. A region-of-interest analysis of the para-anterior cingulate cortex (pACC), previously implicated in reward processing, demonstrated sensitivity to the valence of all stimuli, whether persons or objects, across tasks. Affective evaluation may be a general function of the MPFC, with some regions being tuned to more specific domains of information (e.g., social) than are others.
TL;DR: This work has investigated the role of different areas in the frontal lobe in executive control expressed by macaque monkeys performing a saccade stop signal task and shows how conflict between gaze-holding and gaze-shifting neurons can be used to adjust performance.
Abstract: Executive control requires controlling the initiation of movements, judging the consequences of actions, and adjusting performance accordingly. We have investigated the role of different areas in the frontal lobe in executive control expressed by macaque monkeys performing a saccade stop signal task. Certain neurons in the frontal eye field respond to visual stimuli, and others control the production of saccadic eye movements. Neurons in the supplementary eye field do not control directly the initiation of saccades but, instead, signal the production of errors, the anticipation and delivery of reinforcement, and the presence of response conflict. Neurons in the anterior cingulate cortex signal the production of errors and the anticipation and delivery of reinforcement, but not the presence of response conflict. Intracranial local field potentials in the anterior cingulate cortex of monkeys indicate that these medial frontal signals can contribute to event-related potentials related to performance monitoring. Electrical stimulation of the supplementary eye field improves performance in the task by elevating saccade latency. An interactive race model shows how interacting units produce behavior that can be described as the outcome of a race between independent processes and how conflict between gaze-holding and gaze-shifting neurons can be used to adjust performance.
TL;DR: This case is made by relating an existing cognitive model of category learning to a learning circuit involving the hippocampus, perirhinal, and prefrontal cortices, and it is argued that the proper targets for localization are well-specified cognitive models.
Abstract: Mental localization efforts tend to stress the where more than the what. We argue that the proper targets for localization are well-specified cognitive models. We make this case by relating an existing cognitive model of category learning to a learning circuit involving the hippocampus, perirhinal, and prefrontal cortices. Results from groups varying in function along this circuit (e.g., infants, amnesics, and older adults) are successfully simulated by reducing the model's ability to form new clusters in response to surprising events, such as an error in supervised learning or an unfamiliar stimulus in unsupervised learning. Clusters in the model are akin to conjunctive codes that are rooted in an episodic experience (the surprising event) yet can develop to resemble abstract codes as they are updated by subsequent experiences. Thus, the model holds that the line separating episodic and semantic information can become blurred. Dissociations (categorization vs. recognition) are explained in terms of cluster recruitment demands.
TL;DR: FMRI findings suggest that the neural substrates of focusing attention are based on SPL and ACC-DLPFC networks, and there were group differences in the focusing effect between high-span and low-span subjects: high- spans showed focusing effects greater than those of low- span subjects.
Abstract: Using fMRI, we investigated neural substrates for focusing attention in working memory. To explore this focusing effect, two kinds of reading span test (RST), focused and nonfocused, were performed. In the focused RST (F-RST), the target word to be maintained was the focus word in the sentence. In the nonfocused RST (NF-RST), the target word was not the focus word in the sentence. In both RST conditions, significant activations were found in three main regions: left dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), and left superior parietal lobule (SPL). In addition, fMRI signal changes increased in the left SPL in the NF-RST condition. These findings suggest that the neural substrates of focusing attention are based on SPL and ACC-DLPFC networks. Furthermore, there were group differences in the focusing effect between high-span and low-span subjects: High-span subjects showed focusing effects (supported by SPL control) greater than those of low-span subjects.
TL;DR: The findings suggest that a relative increase in sympathetic activity with a reciprocal decrease in parasympathetic activity may be necessary to generate frontal activity in autobiographical recall of emotions.
Abstract: The present study combined measures of regional cerebral blood flow (rCBF) using positron emission tomography (PET) with measures of the autonomic nervous system using skin conductance (SC), heart rate (HR), and the high frequency band of heart rate variability (HRV) in ten healthy participants who were exposed to autobiographical scripts of memories for three target emotions: anger, happiness, and sadness. According to the results, anger was the only emotion to show a significant increase in sympathetic activity, accompanied by a significant decrease in HRV when compared with a neutral script. Anger was also the only emotion to show significant changes in rCBF in the prefrontal cortex. By contrast, the results for the happy and sad conditions showed no significant increase in sympathetic activity and no changes in rCBF in the prefrontal cortex in comparison with the neutral script. The findings suggest that a relative increase in sympathetic activity with a reciprocal decrease in parasympathetic activity may be necessary to generate frontal activity in autobiographical recall of emotions.
TL;DR: The data support the notion that emotionally arousing stimuli transmodally attract resources, leading to optimized processing of the affective stimuli at the cost of the processing of concurrent stimuli.
Abstract: The P3 component of the event-related potential (ERP) to an acoustic startle probe is modulated during picture viewing, with reduced P3 amplitude when participants view either pleasant or unpleasant, as opposed to neutral, pictures. We have interpreted this as reflecting capture of attentional resources by affective pictures, with fewer resources available for processing the secondary startle probe. In the present study, we tested this resource allocation hypothesis by presenting either pictures or sounds as foreground stimuli, with the prediction that P3 amplitude in response to secondary startle probes would be reduced for affectively engaging foregrounds regardless of modality. Using dense-array electroencephalography and a source estimation procedure, we observed that P3 amplitude was indeed smaller when startle probes were presented during emotional, as opposed to neutral, stimuli for both sound and picture foregrounds. Source modeling indicated a common frontocentral maximum of P3 modulation by affect. The data support the notion that emotionally arousing stimuli transmodally attract resources, leading to optimized processing of the affective stimuli at the cost of the processing of concurrent stimuli.
TL;DR: Findings suggest that, within the vmPFC, the PACC subserves primarily an affective function, whereas in other regions social context can modulate affective responses.
Abstract: In recent studies, various regions of the ventral medial prefrontal cortex (vmPFC) have been implicated in at least two potentially different mental functions: reasoning about the minds of other people (social cognition) and processing reward related information (affective evaluation). In this study, we test whether the activation in a specific area of the vmPFC, the para-anterior cingulate cortex (PACC), correlates with the reward value of stimuli in general or is specifically associated with social cognition. Participants performed a time estimation task with trial-to-trial feedback in which reward and socialcontext were manipulated separately. Reward was manipulated by giving either positive or negative feedback in the form of small squirts of fluid delivered orally. Social context was manipulated by instructing participants that positive and negative feedback was determined by another person or a computer. The data demonstrate a main effect of feedback, but not social context, in the PACC, suggesting that this area of the vmPFC serves a general function in evaluating and/or representing reward value. In addition, activity in a more anterior subregion of the vmPFC demonstrated reward-related sensitivity only in the social context. Another area that showed a similar interaction was the subgenual cingulate, but this region was only sensitive to negative feedback in the social condition. These findings suggest that, within the vmPFC, the PACC subserves primarily an affective function, whereas in other regions social context can modulate affective responses.
TL;DR: It was found that negative learners, as assessed via probabilistic learning, had larger ERNs in the recognition memory task, suggestive of a common underlying enhanced error-processing mechanism, and a role for the Pe and frontal monoamines in error awareness.
Abstract: The error-related negativity (ERN) and error positivity (Pe) are electrophysiological markers of error processing thought to originate in the medial frontal cortex. Previous studies using probabilistic reinforcement showed that individuals who learn more from negative than from positive feedback (negative learners) had larger ERNs than did positive learners. These findings support the dopamine (DA) reinforcement-learning hypothesis of the ERN and associated computational models. However, it remains unclear (1) to what extent these effects generalize to tasks outside the restricted probabilistic reinforcement-learning domain and (2) whether there is a dopaminergic source of these effects. To address these issues, we tested subjects’ reinforcement-learning biases behaviorally and recorded EEG during an unrelated recognition memory experiment. Initial recognition responses were speeded, but the subjects were subsequently allowed to self-correct their responses. We found that negative learners, as assessed via probabilistic learning, had larger ERNs in the recognition memory task, suggestive of a common underlying enhanced error-processing mechanism. Negative learners also had enhanced Pes when selfcorrecting errors than did positive learners. Moreover, the ERN and Pe components contributed independently to negative learning. We also tested for a dopaminergic genetic basis of these ERP components. We analyzed the COMT val/met polymorphism, which has been linked to frontal DA levels. The COMT genotype affected Pe (but not ERN) magnitude; met/met homozygotes showed enhanced Pes to self-corrected errors, as compared with val carriers. These results are consistent with a role for the Pe and frontal monoamines in error awareness.
TL;DR: The results suggest that unconscious analysis of threat is intensified in those prone to anxiety, as is a later stage of threat processing subject to dynamic interactions between automatic and strategic influences.
Abstract: Analysis of threat is thought to involve a “quick and dirty” stage in conjunction with slower processing that is more complete. We investigated both types of threat analysis by recording brain potentials in response to threat and neutral words. Personality testing was used to identify participants who were either high or low in trait anxiety (TA). An observed enhancement of occipital P1 potentials to threat words during an emotional Stroop task was interpreted as a signal of unconscious processing, since it was early, independent of whether word exposure was subliminal or supraliminal, and more prominent the higher the level of TA. Later positive potentials were also enhanced for threat versus neutral words, but the amplitude enhancement increased with higher TA only in the subliminal condition. These results suggest that unconscious analysis of threat is intensified in those prone to anxiety, as is a later stage of threat processing subject to dynamic interactions between automatic and strategic influences.
TL;DR: It is found that emotion reduced item recognition accuracy but did not reliably affect relational memory, and fMRI analyses revealed that neutral and emotional words elicited distinct activation patterns within MTL regions predictive of subsequent memory.
Abstract: Recent neuroimaging results suggest that distinct regions within the medial temporal lobe (MTL) may differentially support the episodic encoding of item and relational information for nonemotional stimuli (for a review, see Davachi, 2006). The present study was designed to assess whether these findings generalize to emotional stimuli. Behaviorally, we found that emotion reduced item recognition accuracy but did not reliably affect relational memory. fMRI analyses revealed that neutral and emotional words elicited distinct activation patterns within MTL regions predictive of subsequent memory. Consistent with previous findings for neutral words, hippocampal activation predicted later relational memory, whereas activation in the perirhinal cortex predicted successful item recognition. However, for emotional words, activation in the amygdala, hippocampus, and posterior parahippocampal cortex predicted item recognition only. These data suggest that MTL regions differentially support encoding of neutral and emotional stimuli.
TL;DR: The findings suggest that the construct of self-reported EQ in adolescents is inversely related to the efficiency of neural processing within the somatic marker circuitry during emotional provocation.
Abstract: The somatic marker hypothesis posits a key role for the ventromedial prefrontal cortex, amygdala, and insula in the ability to utilize emotions to guide decision making and behavior. However, the relationship between activity in these brain regions and emotional intelligence (EQ) during adolescence, a time of particular importance for emotional and social development, has not been studied. Using functional magnetic resonance imaging (fMRI), we correlated scores from the Bar-On Emotional Quotient Inventory, Youth Version (EQ-i:YV) with brain activity during perception of fearful faces in 16 healthy children and adolescents. Consistent with the neural efficiency hypothesis, higher EQ correlated negatively with activity in the somatic marker circuitry and other paralimbic regions. Positive correlations were observed between EQ and activity in the cerebellum and visual association cortex. The findings suggest that the construct of self-reported EQ in adolescents is inversely related to the efficiency of neural processing within the somatic marker circuitry during emotional provocation.
TL;DR: The present experiment indicates that the detection of execution errors in observation does not rely on the error processing mechanism responsible for generating the ERN, and the increased P300 amplitudes suggest a more general monitoring process that signals that the occurrence of unexpected events is involved in the detectionof execution errors.
Abstract: Recent experiments have demonstrated that error-related negativity (ERN) is not only elicited when people commit errors, but also when they observe others committing errors. The present study investigates whether this observed ERN is also present when participants observe execution errors in an everyday context. Participants observed short sequences of pictures showing steps of everyday actions ending either erroneously or correctly. Participants were instructed to indicate by a delayed response whether the observed action was correctly executed or not. The results showed a large P300 for execution errors compared with the observation of correct sequences, but no ERN activity was found. The present experiment indicates that the detection of execution errors in observation does not rely on the error processing mechanism responsible for generating the ERN. The increased P300 amplitudes suggest a more general monitoring process that signals that the occurrence of unexpected events is involved in the detection of execution errors.
TL;DR: The hypothesis that extensive practice can abolish switch costs in humans is tested and it is found that four human subjects each performed 23,000 trials in a task-switching paradigm does not abolition switch costs.
Abstract: Numerous human task-switching studies have shown that decision making that follows a task switch is slower and less accurate than that which follows a task repetition. Stoet and Snyder (2003a) tested humans and rhesus monkeys on a task-switching paradigm, but found, surprisingly, no switch costs in the monkeys. We hypothesized that the exceptional monkey behavior may have been due to the more extensive practice the monkeys received in comparison with human subjects. In the present study, we tested the hypothesis that extensive practice can abolish switch costs in humans. Four human subjects each performed 23,000 trials in a task-switching paradigm. We found that this amount of practice does not abolish switch costs.
TL;DR: The present article presents a brief introduction, overview, and road map to the field and to the special issue devoted to MFC function.
Abstract: The growing attention being given to medial frontal cortex (MFC) in cognitive neuroscience studies has fostered a number of theoretical and paradigmatic perspectives that diverge in important ways. This has led to a great deal of research fractionation, with investigators studying domains and issues in MFC function that sometimes bear (at least at the surface) little relation to the questions addressed by others studying the same brain region. The present issue of Cognitive, Affective, & Behavioral Neuroscience presents articles inspired by a conference bringing together views from across this diversity of research, highlighting both the richness and vibrancy of the field and the challenges to be faced in terms of integration, synthesis, and precision among the theoretical accounts. The present article presents a brief introduction, overview, and road map to the field and to the special issue devoted to MFC function.
TL;DR: The sensitivity of the MFC to disrupted processing elsewhere in the brain suggests complications in interpreting evidence of disturbed MFC function, and the prediction that stimulus degradation should likewise reduce error-related activity in the M FC.
Abstract: Scalp electroencephalogram (EEG) recordings indicate that regions in the medial frontal cortex (MFC) are active following errors. Alcohol consumption reduces this error-related activity, perhaps suggesting that alcohol disrupts the operation of an error-monitoring system in the MFC. However, it could also be that alcohol consumption affects the MFC only indirectly, by impairing stimulus processing and thus making errors harder to detect. This interpretation leads to the prediction that stimulus degradation should likewise reduce error-related activity in the MFC. To test this hypothesis, behavioral and EEG data were collected as participants performed a speeded response task with either bright or very dim stimuli. The results using dim stimuli replicated the observed effects of alcohol consumption-with slowed responses accompanied by reduced error-related MFC activity. The sensitivity of the MFC to disrupted processing elsewhere in the brain suggests complications in interpreting evidence of disturbed MFC function.
TL;DR: Slow potentials were found to be more negative over the parietal and occipital cortex for objects and over the left frontal cortex for letter strings during WM maintenance, which is strongly consistent with the ideas that WM maintenance contributes to LTM formation and that this may occur through strengthening of stimulus-specific cortical memory traces.
Abstract: Behavioral research has led to conflicting views regarding the relationship between working memory (WM) maintenance and long-term memory (LTM) formation. We used slow event-related brain potentials to investigate the degree to which neural activity during WM maintenance is associated with successful LTM formation. Participants performed a WM task with objects and letter strings, followed by a surprise LTM test. Slow potentials were found to be more negative over the parietal and occipital cortex for objects and over the left frontal cortex for letter strings during WM maintenance. Within each category, they were enhanced for items that were subsequently successfully remembered. These effects were topographically distinct, with maximum effects at those electrodes that showed the maximum negativity during WM maintenance in general. Together, these results are strongly consistent with the ideas that WM maintenance contributes to LTM formation and that this may occur through strengthening of stimulus-specific cortical memory traces.
TL;DR: The influence of a native language on learning new speech sounds in adulthood is addressed using a network model in which speech categories are attractors implemented through interactive activation and Hebbian learning.
Abstract: The influence of a native language on learning new speech sounds in adulthood is addressed using a network model in which speech categories are attractors implemented through interactive activation and Hebbian learning. The network has a representation layer that receives topographic projections from an input layer and has reciprocal excitatory connections with deeper layers. When applied to an experiment in which Japanese adults were trained to distinguish the English /r/-/l/ contrast (McCandliss, Fiez, Protopapas, Conway, & McClelland, 2002), the model can account for many aspects of the experimental results, such as the time course and outcome of the learning, how it varies as a function of feedback, the relative efficacy of adaptive and initially easy training stimuli versus nonadaptive and difficult stimuli, and the development of a discrimination peak at the acquired category boundary. The model is also able to capture some aspects of the individual differences in learning. nt]mis|This research was supported by NIMH Grant MH64445 and Training Grant 5T32-MH019983-07. The authors thank Susan G. Guion for generously providing the recordings from her experiment and Mary L. Conway for her assistance with data analysis. Correspondence concerning this article should be addressed to J. L. McClelland, Department of Psychology, 450 Serra Mall, Jordan Hall, Bldg. 420, Stanford, CA 94305
TL;DR: A relationship between pMFC/PFC activity and adaptive posterror behavior change is supported and the discrepancy between these findings and those of previous studies—in the present study, this relationship was detected during the posterror period rather than during commission of the error itself—may have resulted from the requirements of the present task.
Abstract: The magnitude of posterior medial frontal cortex (pMFC) activity during commission of an error has been shown to relate to adaptive posterror changes in response behavior on the trial immediately following. In the present article, we examined neural activity during and after error commission to identify its relationship to sustained posterror behavior changes that led to performance improvements several trials into the future. The standard task required participants to inhibit a prepotent motor response during infrequent lure trials, which were randomly interspersed among numerous go trials. Posterror behavior was manipulated by introducing a dynamic condition, in which an error on a lure trial ensured that the next lure would appear within two to seven go trials. Behavioral data indicated significantly higher levels of posterror slowing and accuracy during the dynamic condition, as well as fewer consecutive lure errors. Bilateral prefrontal cortex (PFC) and pMFC activity during the posterror period, but not during commission of the error itself, was associated with increased posterror slowing. Activity within two of these regions (right PFC and pMFC) also predicted success on the next lure trial. The findings support a relationship between pMFC/PFC activity and adaptive posterror behavior change, and the discrepancy between these findings and those of previous studies—in the present study, this relationship was detected during the posterror period rather than during commission of the error itself—may have resulted from the requirements of the present task. Implications of this discrepancy for the flexibility of cognitive control are discussed.
TL;DR: Face-selective inferotemporal cortex, lateral prefrontal cortex, and dorsal striatum are more responsive to faces near the category boundary, which are most difficult to categorize, and dissociable effects suggest that there are several distinct neural mechanisms involved in categorization.
Abstract: The ways in which visual categories are learned, and in which well-established categories are represented and retrieved, are fundamental issues of cognitive neuroscience. Researchers have typically studied these issues separately, and the transition from the initial phase of category learning to expertise is poorly characterized. The acquisition of novel categories has been shown to depend on the striatum, hippocampus, and prefrontal cortex, whereas visual category expertise has been shown to involve changes in inferior temporal cortex. The goal of the present experiment is to understand the respective roles of these brain regions in the transition from initial learning to expertise when category judgments are being made. Subjects were explicitly trained, over 2 days, to classify realistic faces. Subjects then performed the categorization task during fMRI scanning, as well as a perceptual matching task, in order to characterize how brain regions respond to these faces when not explicitly categorizing them. We found that, during face categorization, face-selective inferotemporal cortex, lateral prefrontal cortex, and dorsal striatum are more responsive to faces near the category boundary, which are most difficult to categorize. In contrast, the hippocampus and left superior frontal sulcus responded most to faces farthest from the category boundary. These dissociable effects suggest that there are several distinct neural mechanisms involved in categorization, and provide a framework for understanding the contribution of each of these brain regions in categorization.