Dynamic changes in parietal activation during encoding: implications for human learning and memory.

The ventral posterior parietal cortex (vPPC) monitors successful memory retrieval, yet its role during learning remains unclear. Indeed, increased vPPC activation during stimulus encoding is often negatively correlated with subsequent memory performance, suggesting that this region is suppressed during learning. Alternatively, the vPPC may engage in learning-related processes immediately after stimulus encoding thus facilitating retrieval at a later time. To investigate this possibility, we assessed vPPC activity during item presentation and immediately following its offset when a cue to remember was presented. We observed a dynamic change in vPPC response such that activity was negatively correlated with subsequent memory during stimulus presentation but positively correlated immediately following the stimulus during the cue phase. Furthermore, regional differences in this effect suggest a degree of functional heterogeneity within the vPPC. These findings demonstrate that the vPPC is engaged during learning and acts to facilitate post-encoding memory processes that establish long-term cortical representations.

Contextual influences on dynamic facial expressions.

Participants viewed dynamic facial expressions that moved from a neutral expression to varying degrees of angry, happy, or sad or from these emotionally expressive faces to neutral.A contrast effect was observed for expressions that moved to a neutral state. That is, a neutral expression that began as angry was rated as having a mildly positive expression, whereas the same neutral expression was rated as negatively valenced when it began with a smile. In Experiment 2, static expressions presented sequentially elicited contrast effects, but they were weaker than those following dynamic expressions. Experiment 3 assessed a broad range of facial movements across varying degrees of angry and happy expressions. We observed momentum effects for movements that ended at mildly expressive points (25% and 50% expressive). For such movements, affect ratings were higher, as if the perceived expression moved beyond their endpoint. Experiment 4 assessed sad facial expressions and found both contrast and momentum effects for dynamic expressions to and from sad faces. These findings demonstrate new and potent contextual influences on dynamic facial expressions and highlight the importance of facial movements in social-emotional communication.

Neural correlates of metacognitive monitoring during episodic and semantic retrieval.

Activity in the posterior parietal cortex (PPC) has been shown to be a strong correlate of successful recognition performance. We assessed the degree to which the PPC mediates metacognitive judgments by assessing the feeling of knowing (FOK) for recently learned (episodic) and well-learned (semantic) facts (e.g., "The sport that is associated with Wimbledon is . . ."). Activity in ventral regions of the PPC was observed for strong FOKs for both sets of facts, although greater activity was observed for episodic than for semantic facts. Strong semantic FOKs activated anterior temporal regions. Weaker FOK ratings, when contrasted with strong FOKs, activated dorsal parietal regions, a finding that parallels contrasts during explicit tests in which low-confident responses were compared with high-confident responses. These findings demonstrate retrieval-related parietal activity during metacognitive judgments. Furthermore, they show that the ventral PPC is particularly engaged during context-specific, episodic retrieval, as compared to semantic retrieval.

Task relevance modulates successful retrieval effects during explicit and implicit memory tests.

The successful retrieval effect refers to greater activation for items identified as old compared to those identified as new. This effect is particularly apparent in the ventral posterior parietal cortex (vPPC), though its functional properties remain unclear. In two experiments, we assessed the activation for old and new items during explicit and implicit tests of memory. In Experiment 1, significant effects were observed during explicit recognition performance and during an implicit lexical decision task. In both tasks, determining mnemonic status provides relevant information to task goals. Experiment 2 included a second implicit task in which determining mnemonic status was not relevant (color discrimination task). In this case, vPPC activation did not distinguish between old and new items. These findings suggest that automatic or implicit processes can drive retrieval-related activation in the vPPC, though such processes are gated by stimulus relevancy and task goals.

Episodic retrieval and the cortical binding of relational activity.

Retrieval of episodic memories depends on the successful "re-collection" of event features, such as the time, place, people, thoughts, and feelings associated with a past experience.In neuroimaging studies, ventral regions of the posterior parietal cortex (vPPC) are particularly active when episodic memories are successfully retrieved. A review of the neural correlates of episodic retrieval is presented along with a new theory, cortical binding of relational activity (CoBRA). According to CoBRA, the vPPC acts as a convergence zone that binds episodic features stored in disparate neocortical regions. This process works in conjunction with other known mechanisms, such as those associated with the prefrontal cortex and medial temporal lobe.

Hierarchical relational binding in the medial temporal lobe: the strong get stronger.

Controversy exists over the functional role of the medial temporal lobe (MTL) in episodic memory. Some have suggested that the hippocampus plays a unique and qualitatively different role than other MTL regions, whereas others suggest that the entire MTL has one functional role, which is to support the consolidation of declarative memories. Hierarchical relational binding theory (hRBT) purports that the functional role of the entire MTL is the binding of features associated with an episodic experience. As the hippocampus sits at the top of this hierarchy, binding at this level is particularly efficient in reinstating event features at the time of retrieval. Thus, this theory offers a unified account of MTL that yields outcomes similar to theories that suggest a special role of the hippocampus. In this way, hRBT captures features of both single- and dual-process models of MTL and reconciles controversies about the nature of episodic recollection.

Activation of right parietal cortex during memory retrieval of nonlinguistic auditory stimuli.

In neuroimaging studies, the left ventral posterior parietal cortex (PPC) is particularly active during memory retrieval. However, most studies have used verbal or verbalizable stimuli. We investigated neural activations associated with the retrieval of short, agrammatical music stimuli (Blackwood, 2004), which have been largely associated with right hemisphere processing. At study, participants listened to music stimuli and rated them on pleasantness. At test, participants made old/new recognition judgments with high/low confidence ratings. Right, but not left, ventral PPC activity was observed during the retrieval of these music stimuli. Thus, rather than indicating a special status of left PPC in retrieval, both right and left ventral PPC participate in memory retrieval, depending on the type of information that is to be remembered.

Superadditive memory strength for item and source recognition: the role of hierarchical relational binding in the medial temporal lobe.

Source memory depends on our ability to recollect contextual information--such as the time, place, feelings, and thoughts associated with a past event. It is acknowledged that the medial temporal lobe (MTL) plays a critical role in binding such episodic features. Yet, controversy exists over the nature of MTL binding--whether it contributes specifically to source recollection or whether it contributes equally to both item familiarity and source recollection. To resolve this issue, the authors propose that the MTL acts to bind contextual features through a process of hierarchical relational binding. That is, by way of multiple levels of associative bindings (i.e., bindings of bindings), the MTL links episodic features in a superadditive manner. To account for this binding feature, the authors develop a recognition model that includes positively skewed distributions of memory strength. Such skewed distributions can account for many empirical findings and regularities of both item familiarity and source recollection.

Mistakes, Too Few to Mention? Impaired Self-conscious Emotional Processing of Errors in the Behavioral Variant of Frontotemporal Dementia.

Anosognosia, or lack of awareness of one's deficits, is a core feature of the behavioral variant of frontotemporal dementia (bvFTD). We hypothesized that this deficit has its origins in failed emotional processing of errors. We studied autonomic and facial emotional reactivity to errors in patients with bvFTD (n = 17), Alzheimer's disease (AD, n = 20), and healthy controls (HC, n = 35) during performance of a timed two-alternative-choice button press task. Performance-related behavioral responses to errors were quantified using rates of error correction and post-error slowing of reaction times. Facial emotional responses were measured by monitoring facial reactivity via video and subsequently coding the type, duration and intensity of all emotional reactions. Skin conductance response (SCR) was measured via noninvasive sensors. SCR and total score for each facial emotion expression were quantified for each trial. Facial emotions were grouped into self-conscious (amusement, embarrassment) and negative (fear, sadness, anger, disgust, contempt) emotions. HCs corrected 99.4% of their errors. BvFTD patients corrected 94% (not statistically different compared with HC) and AD corrected 74.8% of their errors (p < 0.05 compared with HC and bvFTD). All groups showed similar post-error slowing. Errors in HCs were associated with greater facial reactivity and SCRs compared with non-error trials, including both negative and self-conscious emotions. BvFTD patients failed to produce self-conscious emotions or an increase in SCR for errors, although they did produce negative emotional responses to a similar degree as HCs. AD showed no deficit in facial reactivity to errors. Although, SCR was generally reduced in AD during error trials, they showed a preserved increase in SCR for errors relative to correct trials. These results demonstrate a specific deficit in emotional responses to errors in bvFTD, encompassing both physiological response and a specific deficit in self-conscious emotions, despite intact awareness and correction of errors. The findings provide a potential mechanism for anosognosia and possibly other behavioral abnormalities in bvFTD and highlight the importance of studying multiple channels of reactivity to errors, including performance related responses and emotional responses, in order to understand how impaired error processing could influence behavior.

Memory for facial expressions: the power of a smile.

Faces with expressions (happy, surprise, anger, fear) were presented at study. Memory for facial expressions was tested by presenting the same faces with neutral expressions and asking participants to determine the expression that had been displayed at study. In three experiments, happy expressions were remembered better than other expressions. The advantage of a happy face was observed even when faces were inverted (upside down) and even when the salient perceptual feature (broad grin) was controlled across conditions. These findings are couched in terms of source monitoring, in which memory for facial expressions reflects encoding of the dispositional context of a prior event.

Influences of emotion on context memory while viewing film clips.

Participants listened to words while viewing film clips (audio off). Film clips were classified as neutral, positively valenced, negatively valenced, and arousing. Memory was assessed in three ways: recall of film content, recall of words, and context recognition. In the context recognition test, participants were presented a word and determined which film clip was showing when the word was originally presented. In two experiments, context memory performance was disrupted when words were presented during negatively valenced film clips, whereas it was enhanced when words were presented during arousing film clips. Free recall of words presented during the negatively valenced films was also disrupted. These findings suggest multiple influences of emotion on memory performance.

Evidence for intact semantic representations in patients with frontal lobe lesions.

Patients with frontal lobe lesions and control participants were assessed on 2 tests of semantic knowledge. In the triadic comparison task, participants were shown all possible triplets of 12 animal names and judged which 2 of each triplet were most alike. In the ordered similarity task, participants rank ordered animals in terms of their similarity to a target animal. For both tasks, semantic structure--derived from multidimensional scaling techniques--revealed similar representations in patients with frontal lobe lesions and control participants. Additional pathfinder analyses also produced networks that did not differ between groups. These patients exhibited intact semantic knowledge despite deficits on tests of free recall and verbal fluency that involved the same semantic category and exemplars. Thus, intact representation of semantic knowledge in frontal patients stands in contrast to their marked deficits in strategic retrieval of semantic knowledge.

Is it bigger than a breadbox? Performance of patients with prefrontal lesions on a new executive function test.

Executive deficits of problem solving and concept formation have been associated with frontal lobe dysfunction. Here we describe a new clinical test of concept formation based on the parlor game, Twenty Questions. The Twenty Questions Test requires examinees to ask the fewest number of yes/no questions possible in order to identify a target item from an array of 30 line drawings. The items belong to a number of categories and subcategories that exist in a hierarchical, semantic structure. Patients with focal prefrontal lesions asked significantly more questions than controls in their attempt to guess the target items and sometimes exhausted the 20-question limit. Qualitative analyses revealed that patients tended to use ineffective categorization strategies, for example, relying exclusively on questions that referred to single items. Taken together with previous findings, we conclude that prefrontal cortex supports the on-line organization and conceptualization of category exemplars in concept-formation tasks.

Improved control of exogenous attention in action video game players.

Action video game players (VGPs) have demonstrated a number of attentional advantages over non-players. Here, we propose that many of those benefits might be underpinned by improved control over exogenous (i.e., stimulus-driven) attention. To test this we used an anti-cueing task, in which a sudden-onset cue indicated that the target would likely appear in a separate location on the opposite side of the fixation point. When the time between the cue onset and the target onset was short (40 ms), non-players (nVGPs) showed a typical exogenous attention effect. Their response times were faster to targets presented at the cued (but less probable) location compared with the opposite (more probable) location. VGPs, however, were less likely to have their attention drawn to the location of the cue. When the onset asynchrony was long (600 ms), VGPs and nVGPs were equally able to endogenously shift their attention to the likely (opposite) target location. In order to rule out processing-speed differences as an explanation for this result, we also tested VGPs and nVGPs on an attentional blink (AB) task. In a version of the AB task that minimized demands on task switching and iconic memory, VGPs and nVGPs did not differ in second target identification performance (i.e., VGPs had the same magnitude of AB as nVGPs), suggesting that the anti-cueing results were due to flexible control over exogenous attention rather than to more general speed-of-processing differences.

Metacognition in the behavioral variant of frontotemporal dementia and Alzheimer's disease.

OBJECTIVE: Impaired self-awareness is characteristic of nearly all dementias, including Alzheimer's disease (AD), but the deficit is most severe in the behavioral variant of frontotemporal dementia (bvFTD). The prominence of frontal pathology in bvFTD suggests that failure of online monitoring, the process by which individuals monitor their own cognitive processing in real time, is an important contributor. Metacognitive research offers several approaches to measure self-assessment, some more and others less sensitive to online monitoring. The goal of this study was to assess metacognition in bvFTD using several approaches, and to compare the results with those in AD. METHOD: We examined metacognition in 12 patients with bvFTD, 14 with AD, and 35 healthy controls using feeling of knowing (FOK), ease of learning (EOL), judgment of learning (JOL), and retrospective confidence rating (CR) tasks, as well as response to feedback about performance. RESULTS: BvFTD and AD were both impaired at FOK compared with controls, although AD showed some sparing. Both groups were similarly impaired at CR and neither group was impaired at JOL after accounting for memory performance. Most striking, bvFTD patients failed to appropriately adjust their predictions about future memory performance even after receiving explicit feedback that they had performed worse than they expected. CONCLUSIONS: Both bvFTD and AD show deficits in online monitoring, although the deficit appears more severe in bvFTD. The insensitivity of bvFTD patients to overt feedback may point to unique mechanisms, possibly frontally mediated, that add to their severe lack of self-awareness.

Neural correlates of emotional regulation while viewing films.

Negative and arousal-inducing film clips were used to assess the neural correlates of emotional expression and suppression. Compared to viewing neutral clips, both negative (disgusting) and arousal (action) clips activated primarily posterior regions in the parietal and occipital cortex when participants were instructed to express their emotions. When instructed to suppress their emotions while viewing negative clips, a broad frontoparietal network was activated that included lateral, medial, and orbital regions in the prefrontal cortex as well as lateral and medial regions of the posterior parietal cortex. The suppression of arousal clips also activated prefrontal and parietal regions, though not to the same extent as the suppression of negative clips. The findings demonstrate the potency of using movies to engage emotional processes and highlight a broad frontoparietal network that is engaged during the suppression of negative film clips.

The generation effect: activating broad neural circuits during memory encoding.

The generation effect is a robust memory phenomenon in which actively producing material during encoding acts to improve later memory performance. In a functional magnetic resonance imaging (fMRI) analysis, we explored the neural basis of this effect. During encoding, participants generated synonyms from word-fragment cues (e.g., GARBAGE-W_ST_) or read other synonym pairs (e.g., GARBAGE-WASTE). Compared to simply reading target words, generating target words significantly improved later recognition memory performance. During encoding, this benefit was associated with a broad neural network that involved both prefrontal (inferior frontal gyrus, middle frontal gyrus) and posterior cortex (inferior temporal gyrus, lateral occipital cortex, parahippocampal gyrus, ventral posterior parietal cortex). These findings define the prefrontal-posterior cortical dynamics associated with the mnemonic benefits underlying the generation effect.

Dissociable parietal regions facilitate successful retrieval of recently learned and personally familiar information.

In fMRI analyses, the posterior parietal cortex (PPC) is particularly active during the successful retrieval of episodic memory. To delineate the neural correlates of episodic retrieval more succinctly, we compared retrieval of recently learned spatial locations (photographs of buildings) with retrieval of previously familiar locations (photographs of familiar campus buildings). Episodic retrieval of recently learned locations activated a circumscribed region within the ventral PPC (anterior angular gyrus and adjacent regions in the supramarginal gyrus) as well as medial PPC regions (posterior cingulated gyrus and posterior precuneus). Retrieval of familiar locations activated more posterior regions in the ventral PPC (posterior angular gyrus, LOC) and more anterior regions in the medial PPC (anterior precuneus and retrosplenial cortex). These dissociable effects define more precisely PPC regions involved in the retrieval of recent, contextually bound information as opposed to regions involved in other processes, such as visual imagery, scene reconstruction, and self-referential processing.

Emotions in context: pictorial influences on affective attributions.

The visual illusion Terror Subterra, by Roger Shepard (1990), depicts a seemingly large creature chasing another in a tunnel, yet both creatures are physically identical. In addition to this visual illusion, the two creatures also appear to exhibit different emotions, as the background creature (the pursuer) appears angry whereas the foreground creature (the pursued) appears fearful. We explored this context effect by first establishing the magnitude of the emotional bias effect. We then modified the original drawing in various ways, such as equating for perceived size, removing one creature from the scene, and removing the pictorial context altogether. Findings suggest that the emotional bias is due to the pictorial setting and to the perceived social-emotional relationship between the two creatures. These results highlight the importance of both perceptual and social-emotional influences in driving affective attributions.

Action video game experience reduces the cost of switching tasks.

Video game expertise has been shown to have beneficial effects for visual attention processes, but the effects of action video game playing on executive functions, such as task switching and filtering out distracting information, are less well understood. In the main experiment presented here, video game players (VGPs) and nonplayers (nVGPs) switched between two tasks of unequal familiarity: a familiar task of responding in the direction indicated by an arrow, and a novel task of responding in the opposite direction. nVGPs had large response time costs for switching from the novel task to the familiar task, and small costs for switching from the familiar task to the novel task, replicating prior findings. However, as compared to the nVGPs, VGPs were more facile in switching between tasks, producing overall smaller and more symmetric switching costs, suggesting that experience with action video games produces improvements in executive functioning. In contrast, VGPs and nVGPs did not differ in filtering out the irrelevant flanking stimuli or in remembering details of aurally presented stories. The lack of global differences between the groups suggests that the improved task-switching performance seen in VGPs was not due to differences in global factors, such as VGPs being more motivated than nVGPs.