Strategic resource allocation in the human brain supports cognitive coordination of object and spatial working memory

Biased competition between action representations

We propose a generalized version of the biased competition account of attention that may be applied to all domains of cognition. Based on our Generalized Biased Competition account, we propose a formal race model of selection of action representations. The model explains how action representations stored in long-term memory are competing for selection based on their match to the current environmental context and their importance weight. We then present results and model fits from three experiments using a recently developed multiple cue paradigm where several attention shifts with different associated reward values are competing. We show that participants were surprisingly efficient at selecting both when the number of cues and the number of possible reward values were increased. Only when we manipulated reward contingencies and knowledge of these, did the participants show suboptimal performance. The new Generalized Biased Competition account can also explain failures of executive control exemplified by goal neglect where instructions fail to influence behavior despite being retrievable. Finally, we argue that our model may provide a unified understanding of intentions, routines, and habits. Specifically, intentions, routines, and habits may be understood as a continuous range of the same fundamental form of action representation but with variation in their strength of long-term memory traces and importance weights.

Takeover and non-driving related task performance in conditional automated driving: EEG and behavior Parameters interaction

In this study, a conditional automated driving scenario is simulated using virtual reality (VR) technology to explore whether office works presented through augmented reality (AR) affect task and takeover performance, and the neural mechanism was revealed. Sixty-four participants were recruited and their electroencephalography (EEG) was used to measure the brain activities. The results indicated that non-driving-related tasks (NDRTs) requiring higher internal attention focus resulted in poorer task and takeover performance. The alpha power decline magnitude in the parietotemporal (PT) was positively correlated with the takeover time; and the greater the alpha power decline in the right centroparietal (CP) hemisphere, the worse is the participants' memory quality for NDRTs. The ventral attention network (VAN) and right parietal cortex, which are active during working memory, are more likely to explain these findings. The results can provide suggestions for the design of AR-ADS and help improve the safety in L3 driving automation systems.

Transcranial Direct Current Stimulation over the Posterior Parietal Cortex Increases Nontarget Retrieval during Visual Working Memory

Visual working memory (VWM) requires precise feature binding. Previous studies have revealed a close relationship between the posterior parietal cortex (PPC) and feature binding during VWM; this study further examined their causal relationship through three transcranial direct current stimulation (tDCS) experiments. In Experiment 1 (N = 57), participants underwent three sessions of tDCS separately, including PPC stimulation, occipital cortex stimulation, and sham stimulation, and completed delayed estimation tasks for orientations before and after stimulation. Results showed that tDCS over PPC selectively prolonged recall response time (RT) and increased the probability of nontarget responses (a.k.a. failure of feature binding, pNT). In Experiment 2 (N = 29), combining metacognition estimation, we further investigated whether the effects of PPC stimulation were attributed to misbinding (i.e., participants self-reported "remembered" in nontarget responses) or informed guessing trials (participants self-reported "forgotten" in nontarget responses). We replicated the main findings in Experiment 1 and observed greater tDCS effects of PPC on RT in informed guessing trials while there are comparable effects on pNT in these two types of trials. In Experiment 3 (N = 28), we then examined whether the tDCS effects over PPC specifically influenced the memory retrieval process by using a change detection task. We found that PPC stimulation did not influence the recognition RT or accuracy. Together, this study provided direct causal evidence supporting the specific involvement of PPC in feature binding during VWM retrieval, from both aspects of speed and response preference, expanding our understanding of the neural basis of feature binding in VWM.

Graph Theory Further Revealed Visual Spatial Working Memory Impairment in Patients with Inflammatory Bowel Disease

Background

Inflammatory Bowel Disease (IBD) patients may experience cognitive impairments in Visuospatial Working Memory (VSWM), significantly impacting their quality of life. However, the mechanisms underlying these impairments remain poorly understood.

Methods

We studied functional MRI and graph theory analysis to investigate changes in functional connectivity networks during the Mental Rotation Task (MRT) in IBD patients. Twenty IBD patients (13 males, 7 females; mean age = 34.95 ± 13.80 years; mean disease duration = 2.43 ± 2.37 years) participated in the study. Exclusion criteria encompassed recent use of analgesics, 5-Aminosalicylate, corticosteroids, or immunosuppressants within the past three months. Additionally, we recruited 20 age-, gender-, and education-matched healthy controls for comparison.

Results

Compared to a control group, IBD patients exhibited significantly longer reaction times and reduced accuracy during the MRT. Our analysis revealed abnormalities in multiple nodal attributes within the functional connectivity network, particularly in regions such as the bilateral orbitofrontal cortex, right supplementary motor area, bilateral parahippocampal gyrus, and bilateral anterior temporal lobe. We observed that the nodal efficiency in the left temporal pole is negatively correlated with Red Blood Cell Distribution Width (RDW) and positively correlated with response time of MRT.

Conclusion

Our findings revealed notable abnormalities in multiple node attributes among IBD patients during MRT, providing evidence of cognitive impairments in VSWM in IBD patients. This study found RDW maybe can serve as a clinical indicator for predicting early VSWM impairment in patients with IBD.

Top-down modulation of DLPFC in visual search: a study based on fMRI and TMS

Effective visual search is essential for daily life, and attention orientation as well as inhibition of return play a significant role in visual search. Researches have established the involvement of dorsolateral prefrontal cortex in cognitive control during selective attention. However, neural evidence regarding dorsolateral prefrontal cortex modulates inhibition of return in visual search is still insufficient. In this study, we employed event-related functional magnetic resonance imaging and dynamic causal modeling to develop modulation models for two types of visual search tasks. In the region of interest analyses, we found that the right dorsolateral prefrontal cortex and temporoparietal junction were selectively activated in the main effect of search type. Dynamic causal modeling results indicated that temporoparietal junction received sensory inputs and only dorsolateral prefrontal cortex →temporoparietal junction connection was modulated in serial search. Such neural modulation presents a significant positive correlation with behavioral reaction time. Furthermore, theta burst stimulation via transcranial magnetic stimulation was utilized to modulate the dorsolateral prefrontal cortex region, resulting in the disappearance of the inhibition of return effect during serial search after receiving continuous theta burst stimulation. Our findings provide a new line of causal evidence that the top-down modulation by dorsolateral prefrontal cortex influences the inhibition of return effect during serial search possibly through the retention of inhibitory tagging via working memory storage.

How are patterned movements stored in working memory?

Introduction

In this study, the change detection paradigm was used to study the working memory of patterned movements and the relationship of this type of memory with the visuospatial sketchpad in three experiments.

Methods

Experiment 1 measured participants' working memory capacity for patterned movements and explored the influence of stimulus type with indicators such as response time and accuracy rate. Experiments 2 and 3 explored the relationship between patterned movements and the visual and spatial subsystems, respectively.

Results

The results of Experiment 1 indicated that individuals can store 3-4 patterned movements in working memory; however, a change in stimulus format or an increase in memory load may decrease the speed and efficiency of working memory processing. The results of Experiment 2 showed that working memory and visual working memory are independent when processing patterned movements. The results of Experiment 3 showed that the working memory of patterned movements was affected by spatial working memory.

Discussion

Changes in stimulus type and memory load exerted different effects on the working memory capacity of participants. These results provide behavioral evidence that the storage of patterned movement information is independent of the visual subsystem but requires the spatial subsystem of the visuospatial sketchpad.

Cardiovascular risk factors and APOE-ε4 status affect memory functioning in aging via changes to temporal stem diffusion

Prior research investigating associations between hypertension, obesity, and apolipoprotein (APOE) genotype status with memory performance among older adults has yielded inconsistent results. This may reflect, in part, a lack of first accounting for the effects these variables have on structural brain changes, that in turn contribute to age-related memory impairment. The current study sought to clarify the relationships between these factors via path modeling. We hypothesized that higher body mass index (BMI), hypertension, and being an APOE-ε4 allele carrier would predict poorer memory scores, with much of these effects accounted for by indirect effects operating via differences in the integrity of temporal stem white matter. Participants included 125 healthy older adults who underwent neuropsychological assessment and diffusion-weighted MRI scanning. Direct effects were found for hypertension and demographic variables including age, sex, and education. Importantly, indirect effects were found for BMI, hypertension, APOE-ε4 status, age, and sex, where these factors predicted memory scores via their impact on temporal stem diffusion measures. There was also a dual effect of sex, with a direct effect indicating that females had better memory performance overall, and an indirect effect indicating that females with greater temporal stem diffusion had poorer memory performance. Results suggest that changes to the integrity of temporal white matter in aging may underpin reduced memory performance. These results highlight that accounting for variables that not only directly impact cognition, but also for those that indirectly impact cognition via structural brain changes, is crucial for understanding the impact of risk factors on cognition.

The role of spatial store and executive strategy in spatial working memory: a comparison between patients with obsessive-compulsive disorder and controls

INTRODUCTION

Patients with obsessive-compulsive disorder (OCD) showed impaired spatial working memory (SWM). We evaluated whether patients and healthy controls (HCs) differed in spatial store capacity, and whether they differed in the relative weight of spatial store capacity and/or executive strategy in SWM.

METHODS

Thirty inpatients with OCD and 31 age- and education-matched HCs underwent the CANTAB SWM, SRM (a measure of spatial store). The severity of OC symptoms was assessed using the Y-BOCS. Statistical significance: α = 0.05.

RESULTS

Patients showed poorer performance than HCs in all neuropsychological outcomes. Both poorer SRM and SWM strategy were significantly associated with poorer SWM in the entire sample. No significant interaction between SRM and Group was found, while a significant interaction between SWM strategy and Group emerged; in patients the magnitude of this association was approximately twofold larger than in HCs. OC symptom severity did not correlate with neuropsychological performance.

CONCLUSIONS

Patients with OCD had poorer spatial store capacity than HCs. However, the weight of poorer executive strategy in SWM was greater in patients than HCs, whereas the weight of spatial store was similar. We provided a direct evidence that an impairment in the executive component might be the crucial factor influencing the poorer SWM of these patients.

Brain Oscillatory Correlates of Altered Executive Functioning in Positive and Negative Symptomatic Schizophrenia Patients and Healthy Controls

Working Memory and executive functioning deficits are core characteristics of patients suffering from schizophrenia. Electrophysiological research indicates that altered patterns of neural oscillatory mechanisms underpinning executive functioning are associated with the psychiatric disorder. Such brain oscillatory changes have been found in local amplitude differences at gamma and theta frequencies in task-specific cortical areas. Moreover, interregional interactions are also disrupted as signified by decreased phase coherence of fronto-posterior theta activity in schizophrenia patients. However, schizophrenia is not a one-dimensional psychiatric disorder but has various forms and expressions. A common distinction is between positive and negative symptomatology but most patients have both negative and positive symptoms to some extent. Here, we examined three groups—healthy controls, predominantly negative, and predominantly positive symptomatic schizophrenia patients—when performing a working memory task with increasing cognitive demand and increasing need for executive control. We analyzed brain oscillatory activity in the three groups separately and investigated how predominant symptomatology might explain differences in brain oscillatory patterns. Our results indicate that differences in task specific fronto-posterior network activity (i.e., executive control network) expressed by interregional phase synchronization are able to account for working memory dysfunctions between groups. Local changes in the theta and gamma frequency range also show differences between patients and healthy controls, and more importantly, between the two patient groups. We conclude that differences in oscillatory brain activation patterns related to executive processing can be an indicator for positive and negative symptomatology in schizophrenia. Furthermore, changes in cognitive and especially executive functioning in patients are expressed by alterations in a task-specific fronto-posterior connectivity even in the absence of behavioral impairment.

Mapping of the Underlying Neural Mechanisms of Maintenance and Manipulation in Visuo-Spatial Working Memory Using An n-back Mental Rotation Task: A Functional Magnetic Resonance Imaging Study

Mapping of the underlying neural mechanisms of visuo-spatial working memory (WM) has been shown to consistently elicit activity in right hemisphere dominant fronto-parietal networks. However to date, the bulk of neuroimaging literature has focused largely on the maintenance aspect of visuo-spatial WM, with a scarcity of research into the aspects of WM involving manipulation of information. Thus, this study aimed to compare maintenance-only with maintenance and manipulation of visuo-spatial stimuli (3D cube shapes) utilizing a 1-back task while functional magnetic resonance imaging (fMRI) scans were acquired. Sixteen healthy participants (9 women, M = 23.94 years, SD = 2.49) were required to perform the 1-back task with or without mentally rotating the shapes 90° on a vertical axis. When no rotation was required (maintenance-only condition), a right hemispheric lateralization was revealed across fronto-parietal areas. However, when the task involved maintaining and manipulating the same stimuli through 90° rotation, activation was primarily seen in the bilateral parietal lobe and left fusiform gyrus. The findings confirm that the well-established right lateralized fronto-parietal networks are likely to underlie simple maintenance of visuo-spatial stimuli. The results also suggest that the added demand of manipulation of information maintained online appears to require further neural recruitment of functionally related areas. In particular mental rotation of visuospatial stimuli required bilateral parietal areas, and the left fusiform gyrus potentially to maintain a categorical or object representation. It can be concluded that WM is a complex neural process involving the interaction of an increasingly large network.

Functional and anatomical dissociation between the orthographic lexicon and the orthographic buffer revealed in reading and writing Chinese characters by fMRI

The contribution of orthographic representations to reading and writing has been intensively investigated in the literature. However, the distinction between neuronal correlates of the orthographic lexicon and the orthographic (graphemic) buffer has rarely been examined in alphabetic languages and never been explored in non-alphabetic languages. To determine whether the neural networks associated with the orthographic lexicon and buffer of logographic materials are comparable to those reported in the literature, the present fMRI experiment manipulated frequency and the stroke number of Chinese characters in the tasks of form judgment and stroke judgment, which emphasized the processing of character recognition and writing, respectively. It was found that the left fusiform gyrus exhibited higher activation when encountering low-frequency than high-frequency characters in both tasks, which suggested this region to be the locus of the orthographic lexicon that represents the knowledge of character forms. On the other hand, the activations in the posterior part of the left middle frontal gyrus and in the left angular gyrus were parametrically modulated by the stroke number of target characters only in the stroke judgment task, which suggested these regions to be the locus of the orthographic buffer that represents the processing of stroke sequence in writing. These results provide the first evidence for the functional and anatomical dissociation between the orthographic lexicon and buffer in reading and writing Chinese characters. They also demonstrate the critical roles of the left fusiform area and the frontoparietal network to the long-term and short-term representations of orthographic knowledge, respectively, across different orthographies.

RAB2A Polymorphism impacts prefrontal morphology, functional connectivity, and working memory

Calbindin-containing γ-aminobutyric acid (GABA)ergic interneurons in the prefrontal cortex (PFC) have been found to play an important role in working memory (WM) and their malfunctions have been linked to psychiatric disorders. A recent genome-wide association and expression-SNP study indicated that the RAB2A gene was associated with the density of prefrontal calbindin-positive neurons, suggesting this gene may have a broader influence on prefrontal structure and function. Using multimodal MRI and behavioral tasks, the current study investigated the effect of RAB2A on prefrontal morphology, resting-state functional connectivity, and WM performance in a large sample of healthy Han Chinese subjects. Results showed that the RAB2A AGCAAA haplotype was associated with improved WM accuracy, increased cortical thickness in the left inferior frontal gyrus, and decreased functional connectivity between the left inferior frontal gyrus and the left dorsolateral PFC. Our findings provide consistent evidence supporting the effect of RAB2A on the structure and function of the PFC and related cognitive functions. These results should provide new insights into the neural mechanisms underlying the GABAergic genes' role in WM as well as its dysfunction.

Effects of functional tasks exercise on older adults with cognitive impairment at risk of Alzheimer's disease: a randomised controlled trial

OBJECTIVE

the aim of this study was to compare the effects of a functional tasks exercise programme to a cognitive training programme in older adults with mild cognitive impairment.

DESIGN

a single-blind randomised control trial with the intervention group compared with an active control group.

SETTING

out-patient clinic.

PARTICIPANTS

older adults with mild cognitive impairment (n = 83) aged 60 and older living in the community.

METHODS

participants were randomised to either a functional task exercise group (n = 43) or an active cognitive training group (n = 40) for 10 weeks. All outcome measures were undertaken at baseline, post-intervention and 6-month follow-up using Neurobehavioral Cognitive Status Examination, Trail Making Test, Chinese Version Verbal Learning Test, Category Verbal Learning Test, Lawton Instrumental Activities of Daily Living Scale and Problems in Everyday Living Test.

RESULTS

the functional task exercise group showed significant between-group differences in general cognitive functions, memory, executive function, functional status and everyday problem solving ability. The improvements were sustained over time at 6-month follow-up.

CONCLUSION

a functional tasks exercise programme is feasible for improving cognitive functions and functional status of older adults with mild cognitive impairment. This may serve as a cost-effective adjunct to the existing interventions for populations with mild cognitive impairment.

TRIAL REGISTRATION NUMBER

ACTRN12610001025022.

Merging clinical neuropsychology and functional neuroimaging to evaluate the construct validity and neural network engagement of the n-back task

The n-back task is a widely used neuroimaging paradigm for studying the neural basis of working memory (WM); however, its neuropsychometric properties have received little empirical investigation. The present study merged clinical neuropsychology and functional magnetic resonance imaging (fMRI) to explore the construct validity of the letter variant of the n-back task (LNB) and to further identify the task-evoked networks involved in WM. Construct validity of the LNB task was investigated using a bootstrapping approach to correlate LNB task performance across clinically validated neuropsychological measures of WM to establish convergent validity, as well as measures of related but distinct cognitive constructs (i.e., attention and short-term memory) to establish discriminant validity. Independent component analysis (ICA) identified brain networks active during the LNB task in 34 healthy control participants, and general linear modeling determined task-relatedness of these networks. Bootstrap correlation analyses revealed moderate to high correlations among measures expected to converge with LNB (|ρ|≥ 0.37) and weak correlations among measures expected to discriminate (|ρ|≤ 0.29), controlling for age and education. ICA identified 35 independent networks, 17 of which demonstrated engagement significantly related to task condition, controlling for reaction time variability. Of these, the bilateral frontoparietal networks, bilateral dorsolateral prefrontal cortices, bilateral superior parietal lobules including precuneus, and frontoinsular network were preferentially recruited by the 2-back condition compared to 0-back control condition, indicating WM involvement. These results support the use of the LNB as a measure of WM and confirm its use in probing the network-level neural correlates of WM processing.

Functional connectivity supporting the selective maintenance of feature-location binding in visual working memory

Information on an object's features bound to its location is very important for maintaining object representations in visual working memory. Interactions with dynamic multi-dimensional objects in an external environment require complex cognitive control, including the selective maintenance of feature-location binding. Here, we used event-related functional magnetic resonance imaging to investigate brain activity and functional connectivity related to the maintenance of complex feature-location binding. Participants were required to detect task-relevant changes in feature-location binding between objects defined by color, orientation, and location. We compared a complex binding task requiring complex feature-location binding (color-orientation-location) with a simple binding task in which simple feature-location binding, such as color-location, was task-relevant and the other feature was task-irrelevant. Univariate analyses showed that the dorsolateral prefrontal cortex (DLPFC), hippocampus, and frontoparietal network were activated during the maintenance of complex feature-location binding. Functional connectivity analyses indicated cooperation between the inferior precentral sulcus (infPreCS), DLPFC, and hippocampus during the maintenance of complex feature-location binding. In contrast, the connectivity for the spatial updating of simple feature-location binding determined by reanalyzing the data from Takahama et al. (2010) demonstrated that the superior parietal lobule (SPL) cooperated with the DLPFC and hippocampus. These results suggest that the connectivity for complex feature-location binding does not simply reflect general memory load and that the DLPFC and hippocampus flexibly modulate the dorsal frontoparietal network, depending on the task requirements, with the infPreCS involved in the maintenance of complex feature-location binding and the SPL involved in the spatial updating of simple feature-location binding.

Infants' object location and identity processing in spatial scenes: an ERP study

BACKGROUND

Fast detection and identification of objects in an environment is important for using objects as landmarks during navigation. While adults rapidly process objects within an environment and use landmarks during navigation, infants do not routinely use distal landmarks below the age of 18 months. In the current event-related potential (ERP) study we adopted an oddball paradigm to examine whether infants are capable of processing objects in environments, which is a prerequisite for using objects as landmarks.

METHODS

We measured the electrophysiological correlates and time courses related to the processing of changes in object location, object identity, and a switch of two objects.

RESULTS

Twelve-month-old infants showed an Nc (negative central) effect reflecting increased attention likely caused by initial change detection within 300 msec for all three manipulations. In addition, they showed conscious processing of an object change and a location change as evidenced by a positive slow wave (PSW).

CONCLUSION

This study is the first to show that infants are capable of rapidly detecting changes in single objects when these are presented in an environment, but lack conscious detection of a switch. These results indicate that 12-month-old infants as yet lack the ability to rapidly bind the identity and location of multiple objects within an environment.

Cortical thickness of superior frontal cortex predicts impulsiveness and perceptual reasoning in adolescence

Impulsiveness is a pivotal personality trait representing a core domain in all major personality inventories. Recently, impulsiveness has been identified as an important modulator of cognitive processing, particularly in tasks that require the processing of large amounts of information. Although brain imaging studies have implicated the prefrontal cortex to be a common underlying representation of impulsiveness and related cognitive functioning, to date a fine-grain and detailed morphometric analysis has not been carried out. On the basis of ahigh-resolution magnetic resonance scans acquired in 1620 healthy adolescents (IMAGEN), the individual cortical thickness (CT) was estimated. Correlations between Cloninger's impulsiveness and CT were studied in an entire cortex analysis. The cluster identified was tested for associations with performance in perceptual reasoning tasks of the Wechsler Intelligence Scale for Children (WISC IV). We observed a significant inverse correlation between trait impulsiveness and CT of the left superior frontal cortex (SFC; Monte Carlo Simulation P<0.01). CT within this cluster correlated with perceptual reasoning scores (Bonferroni corrected) of the WISC IV. On the basis of a large sample of adolescents, we identified an extended area in the SFC as a correlate of impulsiveness, which appears to be in line with the trait character of this prominent personality facet. The association of SFC thickness with perceptual reasoning argues for a common neurobiological basis of personality and specific cognitive domains comprising attention, spatial reasoning and response selection. The results may facilitate the understanding of the role of impulsiveness in several psychiatric disorders associated with prefrontal dysfunctions and cognitive deficits.

Electrophysiological correlates of object location and object identity processing in spatial scenes

The ability to quickly detect changes in our surroundings has been crucial to human adaption and survival. In everyday life we often need to identify whether an object is new and if an object has changed its location. In the current event-related potential (ERP) study we investigated the electrophysiological correlates and the time course in detecting different types of changes of an objecṫs location and identity. In a delayed match-to-sample task participants had to indicate whether two consecutive scenes containing a road, a house, and two objects, were either the same or different. In six randomly intermixed conditions the second scene was identical, one of the objects had changed its identity, one of the objects had changed its location, or the objects had switched locations. The results reveal different time courses for the processing of identity and location changes in spatial scenes. Whereas location changes elicited a posterior N2 effect, indicating early mismatch detection, followed by a P3 effect reflecting post-perceptual processing, identity changes elicited an anterior N3 effect, which was delayed and functionally distinct from the N2 effect found for the location changes. The condition in which two objects switched position elicited a late ERP effect, reflected by a P3 effect similar to that obtained for the location changes. In sum, this study is the first to cohesively show different time courses for the processing of location changes, identity changes, and object switches in spatial scenes, which manifest themselves in different electrophysiological correlates.

Frontal and parietal theta burst TMS impairs working memory for visual-spatial conjunctions

In tasks that selectively probe visual or spatial working memory (WM) frontal and posterior cortical areas show a segregation, with dorsal areas preferentially involved in spatial (e.g. location) WM and ventral areas in visual (e.g. object identity) WM. In a previous fMRI study [1], we showed that right parietal cortex (PC) was more active during WM for orientation, whereas left inferior frontal gyrus (IFG) was more active during colour WM. During WM for colour-orientation conjunctions, activity in these areas was intermediate to the level of activity for the single task preferred and non-preferred information. To examine whether these specialised areas play a critical role in coordinating visual and spatial WM to perform a conjunction task, we used theta burst transcranial magnetic stimulation (TMS) to induce a functional deficit. Compared to sham stimulation, TMS to right PC or left IFG selectively impaired WM for conjunctions but not single features. This is consistent with findings from visual search paradigms, in which frontal and parietal TMS selectively affects search for conjunctions compared to single features, and with combined TMS and functional imaging work suggesting that parietal and frontal regions are functionally coupled in tasks requiring integration of visual and spatial information. Our results thus elucidate mechanisms by which the brain coordinates spatially segregated processing streams and have implications beyond the field of working memory.

Mapping brain activation and information during category-specific visual working memory

How is working memory for different visual categories supported in the brain? Do the same principles of cortical specialization that govern the initial processing and encoding of visual stimuli also apply to their short-term maintenance? We investigated these questions with a delayed discrimination paradigm for faces, bodies, flowers, and scenes and applied both univariate and multivariate analyses to functional magnetic resonance imaging (fMRI) data. Activity during encoding followed the well-known specialization in posterior areas. During the delay interval, activity shifted to frontal and parietal regions but was not specialized for category. Conversely, activity in visual areas returned to baseline during that interval but showed some evidence of category specialization on multivariate pattern analysis (MVPA). We conclude that principles of cortical activation differ between encoding and maintenance of visual material. Whereas perceptual processes rely on specialized regions in occipitotemporal cortex, maintenance involves the activation of a frontoparietal network that seems to require little specialization at the category level. We also confirm previous findings that MVPA can extract information from fMRI signals in the absence of suprathreshold activation and that such signals from visual areas can reflect the material stored in memory.

Feature integration in visual working memory: parietal gamma activity is related to cognitive coordination

The mechanism by which distinct subprocesses in the brain are coordinated is a central conundrum of systems neuroscience. The parietal lobe is thought to play a key role in visual feature integration, and oscillatory activity in the gamma frequency range has been associated with perception of coherent objects and other tasks requiring neural coordination. Here, we examined the neural correlates of integrating mental representations in working memory and hypothesized that parietal gamma activity would be related to the success of cognitive coordination. Working memory is a classic example of a cognitive operation that requires the coordinated processing of different types of information and the contribution of multiple cognitive domains. Using magnetoencephalography (MEG), we report parietal activity in the high gamma (80–100 Hz) range during manipulation of visual and spatial information (colors and angles) in working memory. This parietal gamma activity was significantly higher during manipulation of visual-spatial conjunctions compared with single features. Furthermore, gamma activity correlated with successful performance during the conjunction task but not during the component tasks. Cortical gamma activity in parietal cortex may therefore play a role in cognitive coordination.

A unified framework for inhibitory control

Inhibiting unwanted thoughts, actions and emotions figures centrally in daily life, and the prefrontal cortex (PFC) is widely viewed as a source of this inhibitory control. We argue that the function of the PFC is best understood in terms of representing and actively maintaining abstract information, such as goals, which produces two types of inhibitory effects on other brain regions. Inhibition of some subcortical regions takes a directed global form, with prefrontal regions providing contextual information relevant to when to inhibit all processing in a region. Inhibition within neocortical (and some subcortical) regions takes an indirect competitive form, with prefrontal regions providing excitation of goal-relevant options. These distinctions are crucial for understanding the mechanisms of inhibition and how they can be impaired or improved.