Symposium Sessions

Session 1: Towards a cumulative science of human brain function

Sunday, April 18, 10:00 am - 12:00 pm, Westmount Ballroom

Session 2: Prefrontal cortex and perceptual decision making

Monday, April 19, 10:00 am - 12:00 pm, Westmount Ballroom

Session 3: Brain oscillations, dynamic synchrony, and cognition

Monday, April 19, 3:00 - 5:00 pm, Westmount Ballroom

Session 4: Dopamine and Adaptive Memory

Tuesday, April 20, 10:00 am - 12:00 pm, Westmount Ballroom

Session 5: What Controls Executive Control? The Influence of 'Control Context'

Tuesday, April 20, 1:00 - 3:00 pm, Westmount Ballroom

Symposium Session 1
Sunday, April 18, 10:00 am - 12:00 pm, Westmount et al Ballroom

Towards a cumulative science of human brain function

Chair: Tal Yarkoni, Columbia University, University of Colorado at Boulder

This symposium is designed to promote development of a cumulative science of human brain function that advances knowledge through formal synthesis of the rapidly growing functional neuroimaging literature. The first speaker (Tal Yarkoni) will motivate the need for a cumulative approach by highlighting several limitations of individual studies that can only be overcome by synthesizing the results of multiple studies. The second speaker (David Van Essen) will discuss the basic tools required in order to support formal synthesis of multiple studies, focusing particular attention on SumsDB, a massive database of functional neuroimaging data that can support sophisticated search and visualization queries. The third and fourth speakers will discuss two different approaches to combining and filtering results from multiple studies. Tor Wager will review state-of-the-art approaches to meta-analysis of fMRI data, providing empirical examples of the power of meta-analysis to both validate and disconfirm widely held views of brain organization. Russell Poldrack will discuss a novel taxonomic approach that uses collaboratively annotated meta-data to develop formal ontologies of brain function. Collectively, these four complementary talks will familiarize the audience with (a) the importance of adopting cumulative approaches to functional neuroimaging data; (b) currently available tools for accessing and retrieving information from multiple studies; and (c) state-of-the-art techniques for synthesizing the results of different functional neuroimaging studies into an integrated whole.

Keyword: fMRI analyses and methodology

Talk 1: Motivating a cumulative cognitive neuroscience

Tal Yarkoni^1,2; ¹Columbia University, ²University of Colorado at Boulder

Thousands of functional neuroimaging studies are published every year. Only a small fraction of these studies explicitly attempt a formal synthesis of previous findings. In this talk, I argue for an increased emphasis on cumulative approaches to the study of brain function that aim to synthesize and distill the results of previous studies. Three different motives for such an approach are discussed, including (a) the need to distinguish real findings from false alarms; (b) the desire to organize both cognitive tasks and brain activations into coherent ontologies; and (c) the high likelihood that many fMRI studies are underpowered and consequently produce distorted results. I focus primarily on the last of these points, using simulations and empirical analyses to demonstrate that the results of many individual fMRI studies are likely to appear considerably stronger and more selective than they actually are. I conclude by arguing that these limitations are difficult or impossible to overcome in individual studies, necessitating a stronger focus on consensus building at the disciplinary level.

Talk 2: Lost in Localization – But Found with Foci!

David Van Essen¹; ¹Washington University in St. Louis

More than 50,000 studies related to functional imaging of the human brain have been published in recent decades. Of these, more than 10,000 report key experimental data (centers of fMRI activation foci, etc.) in tables of stereotaxic coordinates (‘foci’) in one or another standardized atlas space. To aid in mining this extensive literature, we developed the the SumsDB database (http://sumsdb.wustl.edu/sums/), which supports storage, visualization, and searching of many types of neuroimaging data. SumsDB includes a Foci Library that currently contains >40,000 foci from ~1,400 published studies. This includes comprehensive coverage of five major journals and almost 15% of the relevant literature. Foci searches can be based on many criteria (e.g., cortical area or region, spatial coordinates, functional criteria, or disease condition). Search results can be viewed online (WebCaret) or downloaded for offline visualization and analysis using Caret sofware. As the Foci Library continues to expand, through contributions from curators and volunteers alike, it will become increasingly valuable as a way to efficiently access the burgeoning neuroimaging literature.

Talk 3: Consensus-building and brain-based taxonomies using meta-analysis

Tor Wager¹; ¹University of Colorado at Boulder

Much of cognitive and affective neuroscience has centered on identifying particular brain regions or circuits with categories of psychological processes. Properly synthesized, the accumulation of knowledge can aid in this goal. However, without synthesis, more information is not necessarily better, as it may be difficult to separate truly activated brain regions from spurious or idiosyncratic findings. Meta-analysis of neuroimaging data provides a potential solution to this problem. I will present methods and findings from meta-analyses of both cognitive control and emotion. Meta-analyses of cognitive control reveal a consensus on the prefrontal cortical networks involved in cognitive control processes, and a complexity-dependent posterior-anterior hierarchy of prefrontal activity that complements recent findings on prefrontal organization. Conversely, meta-analyses of emotion argue against several long-standing principles of organization of the emotional brain, paving the way for the development of new models. These findings illustrate the utility of meta-analysis in developing taxonomies of psychological processes based on the patterns of brain activity they elicit rather than folk psychological categorization schemes. I will close the talk by presenting a brain-based classification of psychological tasks that suggests that different quadrants of the brain respect different organizational schemes.

Talk 4: Ontologies for cognitive neuroscience

Russell Poldrack¹; ¹University of Texas at Austin

The stated goal of cognitive neuroscience is to understand how mental function is enabled by the brain. An unstated assumption is that we understand the mental processes that are being mapped onto the brain, but in reality there is little agreement on the structure of mental processes and how they are measured. For this reason, most meta-analyses are focused on comparisons of tasks rather than the underlying mental processes. I will argue that the systematic mapping of mental processes onto brain systems will require the development of a formal ontology of mental function. Using databases of neuroimaging data that are annotated according to such an ontology, it is possible to determine which brain systems are associated with particular mental processes, and also to determine which mental processes can be distinguished from one another according to their associated neural activity patterns. I will provide examples of this approach using both whole-brain fMRI data and results from the BrainMap database.

Symposium Session 2
Monday, April 19, 10:00 am - 12:00 pm, Westmount et al Ballroom

Prefrontal cortex and perceptual decision making

Chair: Hakwan Lau, Columbia University

Formal analysis has shown that the prefrontal cortex is anatomically the final converging point of the dorsal and ventral stream of visual processing. However, empirical investigation of visual perception is often focused on posterior areas of the brain. This bias is recently beginning to be rectified, partly due to new data collected with whole-brain methods such as fMRI in human subjects. These new findings call for new ideas regarding what role the prefrontal cortex plays in visual processing. We review the latest work on this issue, and specifically focus on formal models of perceptual decision making (e.g. probabilistic models of evidence accumulation). The speakers will present new ideas that may help to resolve apparent conflicts in recently reported results.

Keyword: Perception

Talk 1: Neural mechanisms of value and evidence based decision making

John Serences¹; ¹University of California San Diego

I will discuss studies examining the neural mechanisms that support decisions that are based on either the quality of sensory evidence or the probability of reward. Formal models are used to reveal the latent variables that govern choice behaviour in order to guide theoretically motivated investigations into the neural mechanisms of decision making. In the first set of studies, I will argue that the subjective value of a stimulus biases the overall magnitude of cortical responses in early sensory areas (e.g. V1). Moreover, the use of high-resolution fMRI and feature selective voxel tuning functions suggests that value also influences the precision of sensory responses so as to enhance the distinctiveness of valuable objects. Next, I will present data that employs accumulator models of perceptual decision making to investigate the higher-order mechanisms that integrate evidence about low-level stimulus features from early areas of sensory cortex. By combining the predictions of these models with simulations of the BOLD response, predictions about the timecourse and amplitude of activation changes reveal both task specific and task general sites of evidence accumulation in human cortex. Together, these findings suggest that top-down factors like subjective value influence the quality of the sensory representations that form the input to the downstream decision mechanisms that ultimately guide motor interactions with objects in the environment.

Talk 2: The role of the prefrontal cortex in making subjective ratings of perceptual certainty and visibility

Hakwan Lau^1,2; ¹Columbia University, ²Donders Institute for Brain, Cognition and Behavior, Netherlands

When making perceptual decisions, humans, monkeys, as well as non-primate subjects can give subjective reports such as confidence or visibility ratings. We developed psychophysical paradigms under which the subjective ratings can be dissociated from the objectively measured capacity for perceptual processing (e.g. d' in signal detection theoretic terms) - subjects claimed that they saw more or were more certain of their decisions in some conditions even when the performance was the same. Using fMRI, we showed that when perceptual capacity was matched, activity in the dorsolateral prefrontal cortex reflects the subjective ratings. Transcranial magnetic stimulation (TMS) to this regions impaired subject's ability to report their ratings properly. Formal comparison of computational models suggests that subjective ratings depend on a late stage of information processing in a hierarchy (instead of depending on a separate channel, or the same information that drives the perceptual decision). We argue that the prefrontal cortex supports self-monitoring processes at this late stage.

Talk 3: Neural mechanisms of reward rate optimization in perceptual decision making

Hauke Heekeren¹; ¹Max Planck Institute for Human Development, Germany

Decision makers determine perceptual decisions by collecting evidence until reaching a point of choice. They can either make decisions quickly, thereby risking more errors, or make decisions carefully, thereby risking to have fewer opportunities for being maximally rewarded. Single unit recording studies in monkeys have shown that prefrontal (DLPFC) and striatal brain regions are involved in this Speed Accuracy Tradeoff, however their interaction remains unclear. Computational network models suggest a modulation of the connectivity (synaptic efficiency) between striatal and cortical neurons as the neurobiological mechanism by which decision makers adapt their behavior and thereby optimize their reward rate. We used fMRI to investigate this connectivity hypothesis. Participants performed a motion direction discrimination task, in which rewards emphasized either accuracy, or speed, or both. Hence participants had to trade off speed and accuracy depending on the reward condition to maximize reward. Behaviorally, subjects appear to maximize their overall task reward by adjusting the amount of evidence required before making a decision. In a conjunction analysis over all task conditions our neuroimaging results reveal significant activation in the bilateral dorsolateral prefrontal cortical regions of the brain. We used these DLPFC regions as seeds in a subsequent Psychophysiological Interaction analysis to investigate the connectivity hypothesis. We found a significant modulation of the coupling of the Basal Ganglia System to DLPFC seed regions when comparing the different reward conditions. The results suggest that depending on the prevailing optimal strategy, reward optimization is achieved by way of modulating the coupling between cortical and striatal regions.

Talk 4: The economics of visual categorisation

Christopher Summerfield¹; ¹University of Oxford

Visual category judgements have been successfully described by quantitative models which evisage the decision process as an accumulation of evidence towards a criterial threshold (or ‘bound’). These ‘bounded accumulator’ models are supported by evidence from single-cell recordings in the parietal and prefrontal cortices. However, visual detection and discrimination can be biased by information concerning the relative costs or benefits associated with each categorical alternative, and by estimates of their probability of occurrence. My talk will address how visual category judgements are biased within the framework of the bounded accumulator model. Rewards bias fast decisions more than slow decisions, a phenomenon that can be modelled by a shift in prior estimates of perceptual evidence, and estimates of prior evidence may correlate with fMRI signals in the lateral parietal and orbitofrontal cortices. Secondly, I will discuss how ongoing estimates of the dispersion and volatiliy associated with a visual category influence perceptual decision-making. Although humans may learn optimally about the variance of two visual categories, discrimination decisions are biased towards ‘confirming’ that discriminanda come from the category with least variance. This effect is also associated with brain structures involved in the processing of expectations about reward.

Symposium Session 3
Monday, April 19, 3:00 - 5:00 pm, Westmount et al Ballroom

Brain oscillations, dynamic synchrony, and cognition

Chair: Michael Cohen, University of Amsterdam

Paramount among brain functions is interpreting the sensory world and producing appropriate responses. Because the brain comprises specialized processing areas for sensory decoding, integration, memory, and motor generation, spatially disparate and functionally divergent brain regions need to form functionally unified neural networks. And because the world can change so quickly, interactions among brain regions must be extremely temporally precise (milliseconds to tens of milliseconds). Recording electrophysiological signals such as action potentials and local field potentials provide sub-millisecond-resolution windows into the timing of activity within and across neural networks. Cognitive processes elicit idiosyncratic spatio-temporal profiles of activity, which often have strong oscillatory components, and involve multiple spatial and temporal scales. These interactions may be the basis of neural information coding and transfer schemes. This symposium will highlight recent advances in our understanding of the dynamics of how neural networks form from synchronized electrophysiological activity, and the implications of these dynamics for the functional and cognitive architecture of the brain. Topics will span perception, learning, and decision-making, and from rat, monkey, human, and modeling approaches.

Keyword: Hot new topics

Talk 1: Synchronized neural oscillations support cognitive control and reinforcement learning

Michael Cohen¹; ¹Dept of psychology, University of Amsterdam

The medial prefrontal cortex (MFC) is critical for our ability to flexibly adapt our behavior according to rules that we’ve learned or have been told. But the MFC cannot act alone; rapidly and flexibly assessing and responding to the environment requires the MFC to interact with multiple sensory and motor systems with millisecond temporal precision. I will review recent evidence that the human MFC uses long-range oscillatory synchrony (1) to receive information from sensory and motor systems (“bottom-up”) about possible conflicts or errors, and (2) to direct sensory, motor, and motivation systems (“top-down”) to improve current and future performance. MFC-centric, spatially disparate, but functionally linked neural networks are activated during conflicts or errors, predict performance adjustments, and occur independent of conscious awareness. Further, the dynamics of these rapid inter-regional communications are often not mirrored in the amplitude of activity of any isolated brain region, demonstrating that precise timing within and among brain networks provides novel insights into brain function. Evidence will be presented from healthy students, patients with simultaneous nucleus accumbens-MFC recordings, and healthy ageing.

Talk 2: Neural dynamics, decisions and actions

Bijan Pesaran¹; ¹New York University

Cerebral cortex contains a mosaic of brain areas that are connected to form distributed networks. Before each movement we decide to make, multiple areas contain specific patterns of neural activity which can be used to predict what we will do. This talk will present our investigations into dynamics of neuronal activity that seek to understand how interactions between brain areas guide sensory-motor behavior. We have been focusing on parietal area LIP which guides saccadic eye movements together with the Parietal Reach Region (PRR) and dorsal premotor cortex (PMd) which guide arm movements. I will present studies in the monkey that examine how neural dynamics are reflected in the activity of single cells and field potentials, how these dynamics exhibit functional specializations across different cortical areas, and how neural coherence between cortical areas is involved in behaviors such as making a decision and coordination. These studies illustrate how investigations of neural dynamics can help us understand the relationship between the activity of distributed cortical networks and behavior.

Talk 3: Rhythms, cell assemblies and binding in the nervous system: From physiology to function

Nancy Kopell¹; ¹Boston University

It has been known for a long time that the brain can produce rhythmic patterns of electrical activity, and that these can be associated with cognitive activity. However, it remains controversial whether these rhythms participate in cognition, or simply reflect processes that happen during cognition. To make the case that rhythms are functionally important, it is necessary to understand the mechanisms by which the rhythms alter processing in the nervous system. This line of research is still in its infancy, but there is enough to see how such arguments might work. This talk focuses on the gamma (35 -90 Hz) and beta (12-30 Hz) frequency bands, using models to show how the differences in physiology underlying at least some versions of those brain rhythms have different and complementary properties with respect to the creation and interaction of cell assemblies, providing a framework for understanding a variety of data, including some on decision-making.

Talk 4: Keep it in mind: Reactivation in the Ventral Tegmental Area of the rodent

Jean-Marc Fellous¹; ¹University of Arizona

In a rest period immediately after a learning task, neurons in hippocampus, neocortex and striatum become active in spatiotemporal patterns resembling those during the task. This reactivation consists in a precise, millisecond-scale replay of bouts of neural activity and has been proposed as a neurophysiological substrate for memory consolidation. It is still unknown why some memory items are consolidated and others are not. We provide evidence that rodent Ventral Tegmental Area (VTA) neurons are selective for different types of rewards and that reward sensitive neurons strongly reactivate during the rest period following a task that involved rewards. Non-reward sensitive neurons exhibited significant reactivation only if the task involved a substantial motor component. The VTA is a pivotal structure involved in the coding of reward and stimulus salience, and is a key neuromodulatory system involved in synaptic plasticity. The reactivation of this neural population in the rat suggest a new way in which memory consolidation in cognitive structures such as the hippocampus and cortex can be modulated by the affective significance of the items to remember.

Symposium Session 4
Tuesday, April 20, 10:00 am - 12:00 pm, Westmount et al Ballroom

Dopamine and Adaptive Memory

Chair: Daphna Shohamy, Columbia University
Co-Chair: Alison Adcock, Duke University

The aim of this symposium is to highlight recent advances in understanding the role of episodic memory in decision making and adaptive behavior, with a focus on how dopamine and the hippocampus support these processes. It is widely recognized that dopamine contributes to a specialized system for gradual, feedback-based learning in the striatum. However, emerging evidence suggests that dopamine plays a much broader role in learning and memory. In particular, it is now clear that dopamine also contributes to hippocampal function and is a critical determinant of successful memory formation. The talks in this symposium bring together converging evidence from multiple levels of analysis, including human neuroimaging, computational models and patient research. Together, these different perspectives argue for a framework in which dopamine helps create enriched mnemonic representations of the environment to support adaptive behavior in novel situations.

Keyword: Hot new topics

Talk 1: Novelty-related Motivation of Anticipation and exploration by Dopamine

Emrah Duzel¹; ¹University College London

Studies in humans and animals show that dopaminergic neuromodulation originating from the substantia nigra/ventral tegmental area (SN/VTA) of the midbrain enhances hippocampal synaptic plasticity for novel events and has a motivationally energizing effect on actions through striatal mechanisms. In this talk, I will discuss how these mechanisms of dopaminergic neuromodulation connect to the behavioural and functional consequences that age-related structural degeneration of the SN/VTA exerts on declarative memory. A framework model called ‘NOvelty-related Motivation of Anticipation and exploration by Dopamine’ (NOMAD) is proposed which merges existing links between novelty, dopamine, long-term memory, plasticity, energization and their relation to aging. The model captures how maintaining mobility and exploration of novel environments could be useful to slow age-related decline of memory. Furthermore, components of the model have potential relevance for optimizing memory strategies in both healthy and memory-impaired individuals.

Talk 2: Memory in service of goals: Affective neuromodulation and mnemonic salience maps

Alison Adcock¹; ¹Duke University

A little information has the potential to radically change behavior. Information that we encode and remember - declarative memory - is built from autobiographical episodes into narratives and multi-dimensional representations of relationships that define the environment. These narratives, the lessons we derive from them, and the environments that evoke them can alter behavior immediately and persistently. For better and worse, such memories are not veridical records of reality, but rather over-represent information that matters to us. I will discuss emerging fMRI data suggesting that dopaminergic neuromodulation allows motivation and expectation to influence memory encoding for upcoming events, and behavioral data suggesting that motivational states influence both what is encoded and how it is represented in memory. In this framework, approach motivation engages a predictive neuromodulatory system centered around mesolimbic dopamine projections. This system primes the medial temporal lobe memory system to record memories of upcoming events and contexts, creating mnemonic ‘salience maps’. Recent evidence from my laboratory, together with other findings, suggests that dopaminergic modulation promotes processing and plasticity in the hippocampus, resulting in detailed, specific representations well-suited to supporting flexible navigation required for acquisition. This effect differs from modulation during avoidance motivation, which appears to promote predominant processing and plasticity in medial temporal cortex, resulting in unitized representations well-suited to eliciting stereotyped behaviors like freezing. Our data suggest that dopamine tailors both the content and the form of declarative mnemonic representations to support future adaptive behavioral responses consistent with the motivational state at the time of encoding.

Talk 3: Learning to predict outcomes: Evidence from neuropsychology and neuroimaging in humans

Daphna Shohamy¹; ¹Columbia University

Rewards powerfully affect learning. This can be adaptive, allowing organisms to learn to obtain food, money and other important rewards. Rewards that are too powerful, however, can be maladaptive, creating strong habits that are hard to break. Recent research on reward and learning has focused on the role of the striatum and midbrain dopamine regions in habitual learning of stimulus-reward associations. However, emerging evidence suggests that the hippocampus – widely known for its role in episodic or relational learning – is also modulated by reward and is substantially innervated by dopamine. This raises important questions regarding the role of the hippocampus in learning, the unique contributions of the hippocampus and the striatum to learning, and the nature of the relationship between them. I will talk about recent studies that address these questions using functional imaging (fMRI) and patient studies in humans. Converging data from these two approaches suggests that both the striatum and the hippocampus contribute to learning, with distinct implications for how learned information is used. In particular, I will present data suggesting that the striatum guides behavior when choice options are repeated, while the hippocampus builds flexible memories that support transfer of learned knowledge to novel situations. I will discuss the implications of these results for understanding how multiple brain systems contribute to adaptive learning processes.

Talk 4: Reinforcement learning: Beyond reinforcement

Nathaniel Daw¹; ¹New York University

The spiking of dopamine neurons in animals, and apparently analogous BOLD signals at dopaminergic targets in humans, appear to report predictions of future reward. Although prominent computational theories of reinforcement learning suggest that these responses support and reflect learning about decisions based on simple associations with past rewards, it has long been known, behaviorally, that beyond this Thorndikian principle of reinforcement, animals and humans can make decisions drawing on other sorts of knowledge about task structure and contingencies. I first discuss how these additional influences – e.g., simulation or “mental time travel” based on cognitive maps or declarative knowledge – can be incorporated in the framework of reinforcement learning theories, via algorithms for “model-based” learning. These considerations extend learned decision making beyond its home territory in striatum, suggesting interactions with regions involved in declarative and episodic learning. Next, I discuss experiments designed to characterize these influences on decision behavior and associated neural signals. By fitting computational models to human decision behavior and BOLD signals, we demonstrate that neither choices nor putatively dopaminergic signals in striatum can be explained by past reinforcement alone, but instead that both reflect additional declarative learning about task structure and contingencies. Further analyses and experiments seeking trial-by-trial correlates of this structural learning point to regions in the medial temporal lobe and prefrontal cortex. I consider the ramifications of these results for the interactions between procedural and declarative memory systems.

Symposium Session 5
Tuesday, April 20, 1:00 - 3:00 pm, Westmount et al Ballroom

What Controls Executive Control? The Influence of 'Control Context'

Chair: Amishi Jha, University of Pennsylvania

Executive control functions (EF) refer to a family of processes needed to successfully perform complex tasks, particularly in rapidly-changing or demanding situations. Yet, very little is known about the reciprocal influence that situational demands, themselves, may have on executive control. Rather than implicating a homunculus, who sits patiently deciding if control should be up- or down-regulated, a comprehensive account of EF must clarify which factors influence the dynamic engagement or withdrawal of specific control functions. Past studies using response conflict tasks find that when prior control demands are high, subsequent performance improves relative to when prior demands were low. Are these patterns exclusive to conflict tasks, or are they observable across a variety of EF contexts? In studies investigating cognitive fatigue, continued use of specific control processes leads to subsequent performance failures on EF tasks engaging those processes. How might fatigue effects differ for management of ‘cold’ vs 'hot' demands? We investigate these questions across several EF tasks. Our behavioral, fMRI, and ERP results collectively suggest that the ‘control context’, which we characterize as the type, level, and duration of prior demands on executive control, significantly influences subsequent deployment of EF across a variety of task contexts.

Keyword: Hot new topics

Talk 1: Conflict-specific Adaptation Processes in the Human Brain

Tobias Egner¹; ¹Duke University

Cognitive control describes the ability to flexibly configure, maintain, and adjust sets of processing strategies (task-sets) in the pursuit of internal goals. This ability has traditionally been ascribed to a central executive resource that can orchestrate mnemonic, attentive, sensory, and motor processes in line with task demands. More recently, researchers have begun to fractionate this monolithic entity, to replace this quasi-homunculus with a collection of explicitly defined component processes or mechanisms that, in collaboration, may give rise to behavioral flexibility. One such component is a conflict-driven regulatory mechanism for task-set maintenance (conflict adaptation) that employs processing conflicts as a signal for reinforcing the top-down biasing processes that comprise a current task-set. I will discuss the cognitive and neuroanatomical architecture of conflict adaptation in human subjects. I will present evidence that, rather than being a single, domain-general mechanism, conflict adaptation represents a collection of multiple independent conflict-control loops that resolve different types of conflict.

Talk 2: Working Memory Demands Trigger Dynamic Adjustments in Executive Control

Amishi Jha¹, Anastasia Kiyonaga¹; ¹University of Pennsylvania

Dynamic adjustments in executive control are well-documented in ‘conflict’ tasks, wherein competition from irrelevant stimulus attributes intensifies selection demands and leads to subsequent performance benefits. We investigated if mnemonic demands, in a working memory (WM) task, could similarly drive online control modifications. Demand levels (High vs. Low) of WM maintenance (memory load of 2 items vs. 1) and delay-spanning distractor interference (confusable vs. not confusable with memoranda) were manipulated using a factorial design during a WM delayed-recognition task. In young adults, performance was best subsequent to trials in which both maintenance and distractor interference demands were high, followed by trials with high demand in either one of these two control domains, and worst following trials with low demand in both domains. FMRI results revealed that activity within subregions of prefrontal cortex (PFC) was sensitive to demand levels for both the previous and current trial. Since age-related changes in PFC are well-documented, we investigated if performance patterns vary over the lifespan. Indeed, demand-triggered benefits in task performance became more robust from late adolescence into young adulthood, and degraded with advancing age. In adolescents, greater context-sensitive adjustments corresponded with better academic achievement. Thus, behavioral and neural measures, as well as real-world performance outcomes, suggest that dynamic adjustments in executive control may be a potent mechanism by which the WM system configures itself for successful task performance.

Talk 3: Training and Depletion of Executive Functions: The Case of Interference Control

Jonas Perrson¹, Patricia Reuter-Lorenz²; ¹Stockholm University, ²University of Michigan

Brain imaging reveals overlapping sites of prefrontal activation for different cognitive tasks suggesting they may share core executive processes. We tested this hypothesis by measuring behavioral interactions between memory tasks presumed to require interference control - a putative executive process that mediates selection from competing representations. Behavioral data show that different training regimens produce either negative or positive transfer from working memory to semantic and episodic memory task performance. We show that eight days of training on high interference versions of three different working memory tasks increased the efficiency of interference control on the training tasks and on untrained tasks in new memory domains. In contrast we have also demonstrated negative transfer and process-specific “fatigue” effects indicating that control efficiency in a second task is diminished by high control demands in a prior task immediately preceding it in time. This suggests that interference control is a finite resource that can be temporarily depleted. Functional magnetic resonance imaging (fMRI) was used to elucidate the mechanisms associated with decreasing efficiency or resource depletion of the interference control process. Along with reduced performance, fMRI indicates negative transfer is associated with reduced process-specific activation, and increased homologous activation that may be compensatory. In sum, this suggests that interference control is an executive function that is both resource limited and plastic making it possible for training to alter its efficiency.

Talk 4: Regulatory Fatigue: Neurophysiological evidence that fatigue affects executive control and emotional responding

Michael Inzlicht¹, Jennifer Gutsell¹; ¹University of Toronto

Past research indicates cognitive control is limited, depleting quickly after initial exertions. Here, we examine the why and how of fatigue by examining its neurocognitive and emotional/motivational sequelae. In Study 1, participants watched an emotional movie while instructed to either suppress their emotions or watch normally, and then completed an ostensibly unrelated Stroop task while EEG was recorded. Results indicate that emotional suppression impaired Stroop reaction-time performance, an effect mediated by a lower error-related negativity (ERN)—a neural waveform generated by the anterior cingulate cortex and thought to index aspects of the conflict monitoring system. In Study 2, participants watched a video of a person being interviewed while distracting words appeared at the bottom of the screen; participants were instructed to ignore the words or to watch normally. They then viewed positive, negative, and neutral IAPS images within which were embedded 50 ms startle auditory probes while their startle-blink response was measured with EMG. Results suggest that cognitive suppression dampened both the strength of subsequent emotional reactions and emotional differentiation due to valence. Taken together, the results of both studies offer a neural mechanism for cognitive fatigue and suggest an important place for emotion in executive control.