Distinct neural circuits support transient and sustained processes in prospective memory and working memory.

Current theories are divided as to whether prospective memory (PM) involves primarily sustained processes such as strategic monitoring, or transient processes such as the retrieval of intentions from memory when a relevant cue is encountered. The current study examined the neural correlates of PM using a functional magnetic resonance imaging design that allows for the decomposition of brain activity into sustained and transient components. Performance of the PM task was primarily associated with sustained responses in a network including anterior prefrontal cortex (lateral Brodmann area 10), and these responses were dissociable from sustained responses associated with active maintenance in working memory. Additionally, the sustained responses in anterior prefrontal cortex correlated with faster response times for prospective responses. Prospective cues also elicited selective transient activity in a region of interest along the right middle temporal gyrus. The results support the conclusion that both sustained and transient processes contribute to efficient PM and provide novel constraints on the functional role of anterior PFC in higher-order cognition.

Emotional resemblance: Perception of facial emotion in written English.

Written language is comprised of simple line configurations (i.e., letters) that, in theory, elicit affect by virtue of the concepts they symbolize, rather than their physical features. However, we propose that the line configurations that comprise letters vary in their visual resemblance to canonical features of facial emotion and, through such emotional resemblance, influence affective responses to written language. We first describe our data-driven approach to indexing emotional resemblance in each letter according to its visual signature. This approach includes cross-cultural validation and neural-network modeling. Based on the resulting weights, we examine the extent to which emotional resemblance in Latin letters is incidentally processed in a flanker paradigm (Study 1), shapes unintentional affective responses to letters (Study 2), accounts for affective responses to orthographically controlled letter strings (Study 3), and shapes affective responses to real English words (Study 4). Results were supportive of hypotheses. We discuss mechanisms, limitations, and implications. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Segmentation in reading and film comprehension.

When reading a story or watching a film, comprehenders construct a series of representations in order to understand the events depicted. Discourse comprehension theories and a recent theory of perceptual event segmentation both suggest that comprehenders monitor situational features such as characters' goals, to update these representations at natural boundaries in activity. However, the converging predictions of these theories had previously not been tested directly. Two studies provided evidence that changes in situational features such as characters, their locations, their interactions with objects, and their goals are related to the segmentation of events in both narrative texts and films. A 3rd study indicated that clauses with event boundaries are read more slowly than are other clauses and that changes in situational features partially mediate this relation. A final study suggested that the predictability of incoming information influences reading rate and possibly event segmentation. Taken together, these results suggest that processing situational changes during comprehension is an important determinant of how one segments ongoing activity into events and that this segmentation is related to the control of processing during reading.

Reading stories activates neural representations of visual and motor experiences.

To understand and remember stories, readers integrate their knowledge of the world with information in the text. Here we present functional neuroimaging evidence that neural systems track changes in the situation described by a story. Different brain regions track different aspects of a story, such as a character's physical location or current goals. Some of these regions mirror those involved when people perform, imagine, or observe similar real-world activities. These results support the view that readers understand a story by simulating the events in the story world and updating their simulation when features of that world change.

Neural mechanisms of transient and sustained cognitive control during task switching.

A hybrid blocked and event-related functional magnetic resonance imaging (fMRI) study decomposed brain activity during task switching into sustained and transient components. Contrasting task-switching blocks against single-task blocks revealed sustained activation in right anterior prefrontal cortex (PFC). Contrasting task-switch trials against task-repeat and single-task trials revealed activation in left lateral PFC and left superior parietal cortex. In both sets of regions, activation dynamics were strongly modulated by trial-by-trial fluctuations in response speed. In addition, right anterior PFC activity selectively covaried with the magnitude of mixing cost (i.e., task-repeat versus single-task trial performance), and left superior parietal activity selectively covaried with the magnitude of the switching cost (i.e., task-switch versus task-repeat trial performance). These results indicate a functional double dissociation in brain regions supporting different components of cognitive control during task switching and suggest that both sustained and transient control processes mediate the behavioral performance costs of task switching.

Individual differences in amygdala activity predict response speed during working memory.

The human amygdala has classically been viewed as a brain structure primarily related to emotions and dissociated from higher cognition. We report here findings suggesting that the human amygdala also has a role in supporting working memory (WM), a canonical higher cognitive function. In a first functional magnetic resonance imaging (fMRI) study (n = 53), individual differences in amygdala activity predicted behavioral performance in a 3-back WM task. Specifically, higher event-related amygdala amplitude predicted faster response time (RT; r = -0.64), with no loss of accuracy. This relationship was not contingent on mood state, task content, or personality variables. In a second fMRI study (n = 21), we replicated the key finding (r = -0.47) and further showed that the correlation between the amygdala and faster RT was specific to a high working memory load condition (3-back) compared with a low working memory load condition (1-back). These results support models of amygdala function that can account for its involvement not only in emotion but also higher cognition.

Event perception: a mind-brain perspective.

People perceive and conceive of activity in terms of discrete events. Here the authors propose a theory according to which the perception of boundaries between events arises from ongoing perceptual processing and regulates attention and memory. Perceptual systems continuously make predictions about what will happen next. When transient errors in predictions arise, an event boundary is perceived. According to the theory, the perception of events depends on both sensory cues and knowledge structures that represent previously learned information about event parts and inferences about actors' goals and plans. Neurological and neurophysiological data suggest that representations of events may be implemented by structures in the lateral prefrontal cortex and that perceptual prediction error is calculated and evaluated by a processing pathway, including the anterior cingulate cortex and subcortical neuromodulatory systems.

A computational model of event segmentation from perceptual prediction.

People tend to perceive ongoing continuous activity as series of discrete events. This partitioning of continuous activity may occur, in part, because events correspond to dynamic patterns that have recurred across different contexts. Recurring patterns may lead to reliable sequential dependencies in observers' experiences, which then can be used to guide perception. The current set of simulations investigated whether this statistical structure within events can be used 1) to develop stable internal representations that facilitate perception and 2) to learn when to update such representations in a self-organizing manner. These simulations demonstrate that experience with recurring patterns enables a system to accurately predict upcoming stimuli within an event, to identify boundaries between such events based on transient increases in prediction error, and to use such boundaries to improve prediction about subsequent activities.

Multi-task connectivity reveals flexible hubs for adaptive task control.

Extensive evidence suggests that the human ability to adaptively implement a wide variety of tasks is preferentially a result of the operation of a fronto-parietal brain network (FPN). We hypothesized that this network's adaptability is made possible by flexible hubs: brain regions that rapidly update their pattern of global functional connectivity according to task demands. Using recent advances in characterizing brain network organization and dynamics, we identified mechanisms consistent with the flexible hub theory. We found that the FPN's brain-wide functional connectivity pattern shifted more than those of other networks across a variety of task states and that these connectivity patterns could be used to identify the current task. Furthermore, these patterns were consistent across practiced and novel tasks, suggesting that reuse of flexible hub connectivity patterns facilitates adaptive (novel) task performance. Together, these findings support a central role for fronto-parietal flexible hubs in cognitive control and adaptive implementation of task demands.

The function and organization of lateral prefrontal cortex: a test of competing hypotheses.

The present experiment tested three hypotheses regarding the function and organization of lateral prefrontal cortex (PFC). The first account (the information cascade hypothesis) suggests that the anterior-posterior organization of lateral PFC is based on the timing with which cue stimuli reduce uncertainty in the action selection process. The second account (the levels-of-abstraction hypothesis) suggests that the anterior-posterior organization of lateral PFC is based on the degree of abstraction of the task goals. The current study began by investigating these two hypotheses, and identified several areas of lateral PFC that were predicted to be active by both the information cascade and levels-of-abstraction accounts. However, the pattern of activation across experimental conditions was inconsistent with both theoretical accounts. Specifically, an anterior area of mid-dorsolateral PFC exhibited sensitivity to experimental conditions that, according to both accounts, should have selectively engaged only posterior areas of PFC. We therefore investigated a third possible account (the adaptive context maintenance hypothesis) that postulates that both posterior and anterior regions of PFC are reliably engaged in task conditions requiring active maintenance of contextual information, with the temporal dynamics of activity in these regions flexibly tracking the duration of maintenance demands. Activity patterns in lateral PFC were consistent with this third hypothesis: regions across lateral PFC exhibited transient activation when contextual information had to be updated and maintained in a trial-by-trial manner, but sustained activation when contextual information had to be maintained over a series of trials. These findings prompt a reconceptualization of current views regarding the anterior-posterior organization of lateral PFC, but do support other findings regarding the active maintenance role of lateral PFC in sequential working memory paradigms.

Anorexia nervosa and obesity are associated with opposite brain reward response.

Anorexia nervosa (AN) is a severe psychiatric disorder associated with food avoidance and malnutrition. In this study, we wanted to test whether we would find brain reward alterations in AN, compared with individuals with normal or increased body weight. We studied 21 underweight, restricting-type AN (age M 22.5, SD 5.8 years), 19 obese (age M 27.1, SD 6.7 years), and 23 healthy control women (age M 24.8, SD 5.6 years), using blood oxygen level-dependent functional magnetic resonance brain imaging together with a reward-conditioning task. This paradigm involves learning the association between conditioned visual stimuli and unconditioned taste stimuli, as well as the unexpected violation of those learned associations. The task has been associated with activation of brain dopamine reward circuits, and it allows the comparison of actual brain response with expected brain activation based on established neuronal models. A group-by-task condition analysis (family-wise-error-corrected P<0.05) indicated that the orbitofrontal cortex differentiated all three groups. The dopamine model reward-learning signal distinguished groups in the anteroventral striatum, insula, and prefrontal cortex (P<0.001, 25 voxel cluster threshold), with brain responses that were greater in the AN group, but lesser in the obese group, compared with controls. These results suggest that brain reward circuits are more responsive to food stimuli in AN, but less responsive in obese women. The mechanism for this association is uncertain, but these brain reward response patterns could be biomarkers for the respective weight state.

Altered temporal difference learning in bulimia nervosa.

BACKGROUND: The neurobiology of bulimia nervosa (BN) is poorly understood. Recent animal literature suggests that binge eating is associated with altered brain dopamine (DA) reward function. In this study, we wanted to investigate DA-related brain reward learning in BN. METHODS: Ill BN (n = 20, age: mean = 25.2, SD = 5.3 years) and healthy control women (CW) (n = 23, age: mean = 27.2, SD = 6.4 years) underwent functional magnetic resonance brain imaging together with application of a DA-related reward learning paradigm, the temporal difference (TD) model. That task involves association learning between conditioned visual and unconditioned taste stimuli, as well as unexpected violation of those learned associations. Study participants also completed the Sensitivity to Reward and Punishment Questionnaire. RESULTS: Bulimia nervosa individuals showed reduced brain response compared with CW for unexpected receipt and omission of taste stimuli, as well as reduced brain regression response to the TD computer model generated reward values, in insula, ventral putamen, amygdala, and orbitofrontal cortex. Those results were qualitatively similar in BN individuals who were nondepressed and unmedicated. Binge/purge frequency in BN inversely predicted reduced TD model response. Bulimia nervosa individuals showed significantly higher Sensitivity to Reward and Punishment compared with CW. CONCLUSIONS: This is the first study that relates reduced brain DA responses in BN to the altered learning of associations between arbitrary visual stimuli and taste rewards. This attenuated response is related to frequency of binge/purge episodes in BN. The brain DA neurotransmitter system could be an important treatment target for BN.

Developing PFC representations using reinforcement learning.

From both functional and biological considerations, it is widely believed that action production, planning, and goal-oriented behaviors supported by the frontal cortex are organized hierarchically [Fuster (1991); Koechlin, E., Ody, C., & Kouneiher, F. (2003). Neuroscience: The architecture of cognitive control in the human prefrontal cortex. Science, 424, 1181-1184; Miller, G. A., Galanter, E., & Pribram, K. H. (1960). Plans and the structure of behavior. New York: Holt]. However, the nature of the different levels of the hierarchy remains unclear, and little attention has been paid to the origins of such a hierarchy. We address these issues through biologically-inspired computational models that develop representations through reinforcement learning. We explore several different factors in these models that might plausibly give rise to a hierarchical organization of representations within the PFC, including an initial connectivity hierarchy within PFC, a hierarchical set of connections between PFC and subcortical structures controlling it, and differential synaptic plasticity schedules. Simulation results indicate that architectural constraints contribute to the segregation of different types of representations, and that this segregation facilitates learning. These findings are consistent with the idea that there is a functional hierarchy in PFC, as captured in our earlier computational models of PFC function and a growing body of empirical data.

Human brain activity time-locked to narrative event boundaries.

Readers structure narrative text into a series of events in order to understand and remember the text. In this study, subjects read brief narratives describing everyday activities while brain activity was recorded with functional magnetic resonance imaging. Subjects later read the stories again to divide them into large and small events. During the initial reading, points later identified as boundaries between events were associated with transient increases in activity in a number of brain regions whose activity was mediated by changes in the narrated situation, such as changes in characters' goals. These results indicate that the segmentation of narrated activities into events is a spontaneous part of reading, and that this process of segmentation is likely dependent on neural responses to changes in the narrated situation.

A computational model of fractionated conflict-control mechanisms in task-switching.

A feature of human cognition is the ability to monitor and adjust one's own behavior under changing circumstances. A dynamic balance between controlled and rapid responding is needed to adapt to a fluctuating environment. We suggest that cognitive control may include, among other things, two distinct processes. Incongruent stimuli may drive top-down facilitation of task-relevant responses to bias performance toward exploitation vs. exploration. Task or response switches may generally slow responses to bias toward accuracy vs. speed and exploration vs. exploitation. Behavioral results from a task switching study demonstrate these two distinct processes as revealed by higher-order sequential effects. A computational model implements the two conflict-control mechanisms, which allow it to capture many complex and novel sequential effects. Lesion studies with the model demonstrate that the model is unable to capture these effects without the conflict-control loops and show how each monitoring component modulates cognitive control. The results suggest numerous testable predictions regarding the neural substrates of cognitive control.

A direct comparison of anterior prefrontal cortex involvement in episodic retrieval and integration.

Retrieval of information from episodic memory reliably engages regions within the anterior prefrontal cortex (aPFC). This observation has led researchers to suggest that these regions may subserve processes intimately tied to episodic retrieval. However, the aPFC is also recruited by other complex tasks not requiring episodic retrieval. One hypothesis concerning these results is that episodic retrieval recruits a general cognitive process that is subserved by the aPFC. The current study tested a specific version of this hypothesis--namely, that the integration of internally represented information is this process. Event-related fMRI was employed in a 2 (memory task: encoding versus retrieval) x 2 (level of integration: low versus high) factorial within-subjects design. A functional dissociation was observed, with one aPFC subregion uniquely sensitive to level of integration and another jointly sensitive to level of integration and memory task. Analysis of event-related activation latencies indicated that level of integration and memory task effects occurred with significantly different timing. The results provide the first direct evidence regarding the functional specialization within lateral aPFC and the nature of its recruitment during complex cognitive tasks. Moreover, the study highlights the benefits of activation latency analysis for understanding functional contributions and dissociations between closely linked brain regions.

Item- and task-level processes in the left inferior prefrontal cortex: positive and negative correlates of encoding.

Activity in the left inferior prefrontal cortex (LIPC) is often thought to reflect processes that support episodic encoding. Functional magnetic resonance imaging (fMRI) was used to test whether processes subserved by LIPC could be negatively related to subsequent memory performance. Specifically, the current experiment explicitly tested the hypothesis that LIPC processing would positively impact encoding when primarily focused towards specific target items (item-level processing), whereas it would negatively impact encoding when primarily focused on the retrieval and instantiation of current task instructions (task-level processing). Two methods were used to identify regions that were sensitive to the two types of processes: a block-level manipulation of encoding task that influenced subsequent memory, and a back-sort procedure. LIPC was sensitive to item- and task-level processing, but not in a way that always facilitates encoding. LIPC was more active for subsequently remembered words than subsequently forgotten words, but it was also more active in a task that emphasized task-level processing relative to a task that emphasized item-level processing, although this former condition led to poorer subsequent memory performance. This pattern indicates that processes subserved by LIPC are not always positively correlated with episodic encoding. Rather, LIPC processes can support both the controlled semantic processing of items and the controlled retrieval of relevant semantic task context. When devoted to the latter, the diversion of LIPC processes to the task level can have a negative consequence for item-level analysis and encoding.