Hippocampal amnesia disrupts verbal play and the creative use of language in social interaction

Neural Dynamics During the Generation and Evaluation of Creative and Non-Creative Ideas

What are the neural dynamics that drive creative thinking? Recent studies have provided much insight into the neural mechanisms of creative thought. Specifically, the interaction between the executive control, default mode, and salience brain networks has been shown to be an important marker of individual differences in creative ability. However, how these different brain systems might be recruited dynamically during the two key components of the creative process-generation and evaluation of ideas-remains far from understood. In the current study we applied state-of-the-art network neuroscience methodologies to examine the neural dynamics related to the generation and evaluation of creative and non-creative ideas using a novel within-subjects design. Participants completed two functional magnetic resonance imaging sessions, taking place a week apart. In the first imaging session, participants generated either creative (alternative uses) or non-creative (common characteristics) responses to common objects. In the second imaging session, participants evaluated their own creative and non-creative responses to the same objects. Network neuroscience methods were applied to examine and directly compare reconfiguration, integration, and recruitment of brain networks during these four conditions. We found that generating creative ideas led to significantly higher network reconfiguration than generating non-creative ideas, whereas evaluating creative and non-creative ideas led to similar levels of network integration. Furthermore, we found that these differences were attributable to different dynamic patterns of neural activity across the executive control, default mode, and salience networks. This study is the first to show within-subject differences in neural dynamics related to generating and evaluating creative and non-creative ideas.

Contribution of Working Memory and Inferencing to Narrative Discourse Comprehension and Production in Traumatic Brain Injury

PURPOSE

The goal of this study was to identify some potential key cognitive and communicative processes underlying narrative discourse ability following traumatic brain injury (TBI). Specifically, this study (a) investigated the contribution of working memory (WM) and inferencing to narrative discourse comprehension and production; (b) tested key assumptions posited by the Structure Building Framework (SBF), a discourse model; and (c) evaluated the potential for inferencing to contribute to discourse ability beyond a shared variance with WM.

METHOD

Twenty-one individuals with TBI completed six tasks yielding seven measures: verbal and nonverbal WM updating (WMU-V and WMU-NV, respectively), predictive inferencing, the Discourse Comprehension Test (DCT), a picture story comprehension (PSC) task, and story retelling (story grammar and story completeness). Regression analyses were performed using WM and inferencing as predictors for narrative performance.

RESULTS

WM measures were significant predictors of DCT performance and approached significance as predictors of PSC. Inferencing approached significance as a unique predictor for the DCT and story completeness. WMU-V and WMU-NV were highly collinear, and neither WM measure predicted discourse outcomes over and above the other's contribution.

CONCLUSIONS

WM was more strongly associated with comprehension processes, whereas inferencing may be associated with both comprehension and production outcomes. Findings were interpreted as supporting SBF assumptions of domain generality of cognitive processes and mechanisms involved in discourse while also challenging assumptions that the same cognitive substrates are marshaled for comprehension and production processes.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.23148647.

Effects of social context manipulation on dorsal and ventral hippocampal neuronal responses

The hippocampus is critical for contextual memory and has recently been implicated in various kinds of social memory. Traditionally, studies of hippocampal context coding have manipulated elements of the background environment, such as the shape and color of the apparatus. These manipulations produce large shifts in the spatial firing patterns, a phenomenon known as remapping. These findings suggest that the hippocampus encodes and differentiates contexts by generating unique spatial firing patterns for each environment a subject encounters. However, we do not know whether the hippocampus encodes social contexts defined by the presence of particular conspecifics. We examined this by exposing rats to a series of manipulations of the social context, including the presence of familiar male, unfamiliar male and female conspecifics, in order to determine whether remapping is a plausible mechanism for encoding socially-defined contexts. Because the dorsal and ventral regions of the hippocampus are thought to play different roles in spatial and social cognition, we recorded neurons in both regions. Surprisingly, we found little evidence of remapping in response to manipulation of the social context in either the dorsal or ventral hippocampus, although we saw typical remapping in response to changing the background color. This result suggests that remapping is not the primary mechanism for encoding different social contexts. However, we found that a subset of hippocampal neurons fired selectively near the cages that contained the conspecifics, and these responses were most prevalent in the ventral hippocampus. We also found a striking increase in the spatial information content of ventral hippocampal firing patterns. These results indicate that the ventral hippocampus is sensitive to changes in the social context and neurons that respond selectively near the conspecific cages could play an important, if not fully understood role in encoding the conjunction of conspecifics, their location and the environment.

Evidence of Audience Design in Amnesia: Adaptation in Gesture but Not Speech

Speakers design communication for their audience, providing more information in both speech and gesture when their listener is naïve to the topic. We test whether the hippocampal declarative memory system contributes to multimodal audience design. The hippocampus, while traditionally linked to episodic and relational memory, has also been linked to the ability to imagine the mental states of others and use language flexibly. We examined the speech and gesture use of four patients with hippocampal amnesia when describing how to complete everyday tasks (e.g., how to tie a shoe) to an imagined child listener and an adult listener. Although patients with amnesia did not increase their total number of words and instructional steps for the child listener, they did produce representational gestures at significantly higher rates for the imagined child compared to the adult listener. They also gestured at similar frequencies to neurotypical peers, suggesting that hand gesture can be a meaningful communicative resource, even in the case of severe declarative memory impairment. We discuss the contributions of multiple memory systems to multimodal audience design and the potential of gesture to act as a window into the social cognitive processes of individuals with neurologic disorders.

Missing links: The functional unification of language and memory (L∪M)

The field of neurocognition is currently undergoing a significant change of perspective. Traditional neurocognitive models evolved into an integrative and dynamic vision of cognitive functioning. Dynamic integration assumes an interaction between cognitive domains traditionally considered to be distinct. Language and declarative memory are regarded as separate functions supported by different neural systems. However, they also share anatomical structures (notably, the inferior frontal gyrus, the supplementary motor area, the superior and middle temporal gyrus, and the hippocampal complex) and cognitive processes (such as semantic and working memory) that merge to endorse our quintessential daily lives. We propose a new model, "L∪M" (i.e., Language/union/Memory), that considers these two functions interactively. We fractionated language and declarative memory into three fundamental dimensions or systems ("Receiver-Transmitter", "Controller-Manager" and "Transformer-Associative" Systems), that communicate reciprocally. We formalized their interactions at the brain level with a connectivity-based approach. This new taxonomy overcomes the modular view of cognitive functioning and reconciles functional specialization with plasticity in neurological disorders.

The language of mental images: Characterizing hippocampal contributions to imageable word use during event construction

Accumulating evidence suggests that the hippocampus plays a critical role in the creative and flexible use of language at the sentence or discourse level. Yet it is currently unclear whether the hippocampus also supports language use at the level of single words. A recent study by Hilverman et al. (2017) found that amnesic patients with hippocampal damage use less imageable words when describing autobiographical episodes compared to healthy controls, but this deficit was attributed to patients' deficits in episodic memory rather than impairments in linguistic functions of the hippocampus per se. Yet, in addition to affecting word use by way of its role in memory, the hippocampus could also impact language use more directly. The current study aimed to test this hypothesis by investigating the status of imageable word use in amnesia during two different types of language production tasks. In Experiment 1, participants constructed narratives about events depicted in visually presented pictures (picture narratives). In Experiment 2, participants constructed verbal narratives about remembered events from the past or simulated events in the future (past/future narratives). Across all types of narratives, patients produced words that were rated as having similar levels of imageability compared to controls. Importantly, this was the case both in patients' picture narratives, which did not require generating details from episodic memory and were matched to those of controls with respect to narrative content, and in patients' narratives about past/future events, which required generating details from memory and which were reduced in narrative content compared to those of controls. These results distinguish between the quantity and quality of individual linguistic details produced in amnesia during narrative construction, and suggest that the use of imageable linguistic representations does not depend on intact episodic memory and can be supported by regions outside the hippocampus.

Added sugar and dietary fiber consumption are associated with creativity in preadolescent children

Objectives: Creativity requires the ability to combine existing mental representations in new ways and depends, in part, on the hippocampus. Hippocampal function is, in turn, affected by a number of health factors, including aerobic fitness, excess adiposity, and diet. Specifically, in rodent studies, diets high in saturated fatty acids and sugar - hallmarks of a western diet- have been shown to negatively impact hippocampal function and thereby impair performance on cognitive tasks that require the hippocampus. Yet relatively few studies have examined the relationship between diet and hippocampal-dependent cognition in children. Methods: The current study therefore sought to explore the relationship of several diet quality markers including dietary lipids (saturated fatty acids and omega-3 fatty acids), simple carbohydrates (added sugars), and dietary fiber with creativity in preadolescent children. Participants (N = 57; mean age = 9.1 years) completed the Verbal Form of the Torrance Test of Creative Thinking (TTCT), a standardized test of creativity known to require the hippocampus. Additionally, participants completed a 3-day food intake record with the assistance of a parent, underwent dual energy x-ray absorptiometry (DXA) to assess central adiposity, and VO2max testing to assess aerobic fitness. Results: Added sugar intake was negatively associated, and dietary fiber was positively associated with overall TTCT performance. These relationships were sustained even after controlling for key covariates. Discussion: These findings are among the first to report an association between added sugar consumption and hippocampal-dependent cognition during childhood and, given the key role of the hippocampus in learning and memory, as well as creative thinking, have potential educational and public health implications.

Procedural and declarative memory brain systems in developmental language disorder (DLD)

The aim of the current study was to examine microstructural differences in white matter relevant to procedural and declarative memory between adolescents/young adults with and without Developmental Language Disorder (DLD) using diffusion tensor imaging (DTI). The findings showed atypical age-related changes in white matter structures in the corticostriatal system, in the corticocerebellar system, and in the medial temporal region in individuals with DLD. Results highlight the importance of considering the age factor in research on DLD. Future studies are needed to examine the developmental relationship between long-term memory and individual differences in language development and learning.

Semantic Memory and the Hippocampus: Revisiting, Reaffirming, and Extending the Reach of Their Critical Relationship

Since Tulving proposed a distinction in memory between semantic and episodic memory, considerable effort has been directed towards understanding their similar and unique features. Of particular interest has been the extent to which semantic and episodic memory have a shared dependence on the hippocampus. In contrast to the definitive evidence for the link between hippocampus and episodic memory, the role of the hippocampus in semantic memory has been a topic of considerable debate. This debate stems, in part, from highly variable reports of new semantic memory learning in amnesia ranging from profound impairment to full preservation, and various degrees of deficit and ability in between. More recently, a number of significant advances in experimental methods have occurred, alongside new provocative data on the role of the hippocampus in semantic memory, making this an ideal moment to revisit this debate, to re-evaluate data, methods, and theories, and to synthesize new findings. In line with these advances, this review has two primary goals. First, we provide a historical lens with which to reevaluate and contextualize the literature on semantic memory and the hippocampus. The second goal of this review is to provide a synthesis of new findings on the role of the hippocampus and semantic memory. With the perspective of time and this critical review, we arrive at the interpretation that the hippocampus does indeed make necessary contributions to semantic memory. We argue that semantic memory, like episodic memory, is a highly flexible, (re)constructive, relational and multimodal system, and that there is value in developing methods and materials that fully capture this depth and richness to facilitate comparisons to episodic memory. Such efforts will be critical in addressing questions regarding the cognitive and neural (inter)dependencies among forms of memory, and the role that these forms of memory play in support of cognition more broadly. Such efforts also promise to advance our understanding of how words, concepts, and meaning, as well as episodes and events, are instantiated and maintained in memory and will yield new insights into our two most quintessentially human abilities: memory and language.

Enriching Communicative Environments: Leveraging Advances in Neuroplasticity for Improving Outcomes in Neurogenic Communication Disorders

Purpose Research manipulating the complexity of housing environments for healthy and brain-damaged animals has offered strong, well-replicated evidence for the positive impacts in animal models of enriched environments on neuroplasticity and behavioral outcomes across the lifespan. This article reviews foundational work on environmental enrichment from the animal literature and considers how it relates to a line of research examining rich communicative environments among adults with aphasia, amnesia, and related cognitive-communication disorders. Method Drawing on the authors' own research and the broader literature, this article first presents a critical review of environmental complexity from the animal literature. Building on that animal research, the second section begins by defining rich communicative environments for humans (highlighting the combined effects of complexity, voluntariness, and experiential quality). It then introduces key frameworks for analyzing and designing rich communicative environments: distributed communication and functional systems along with sociocultural theories of learning and development in humans that support them. The final section provides an overview of Hengst's and Duff's basic and translational research, which has been designed to exploit the insights of sociocultural theories and research on environmental complexity. In particular, this research has aimed to enrich communicative interactions in clinical settings, to trace specific communicative resources that characterize such interactions, and to marshal rich communicative environments for therapeutic goals for individuals with aphasia and amnesia. Conclusions This article concludes by arguing that enriching and optimizing environments and experiences offers a very promising approach to rehabilitation efforts designed to enhance the reorganization of cognitive-communicative abilities after brain injury. Such interventions would require clinicians to use the principles outlined here to enrich communicative environments and to target distributed communication in functional systems (not the isolated language of individuals).

The nature of recollection across months and years and after medial temporal lobe damage

We studied the narrative recollections of memory-impaired patients with medial temporal lobe (MTL) damage who took a 25-min guided walk during which 11 planned events occurred. The recollections of the patients, recorded directly after the walk, were compared with the recollections of controls tested directly after the walk (C1), after one month (C2), or after 2.6 years (C3). With respect to memory for the walk, the narrative recollections of the patients were impoverished compared with C1 but resembled the recollections of volunteers tested after long delays (C2 and C3). In addition, how language was used by the patients in their recollections resembled how language was used by groups C2 and C3 (higher-frequency words, less concrete words, fewer nouns, more adverbs, more pronouns, and more indefinite articles). These findings appear to reflect how individuals, either memory-impaired patients or controls, typically speak about the past when memory is weak and lacks detail and need not have special implications about language use and MTL function beyond the domain of memory. A notable exception to the similarity between patient narratives and the narratives of C2 and C3 was that the control groups reported the events of the walk in correct chronological order, whereas the order in which patients reported events bore no relationship to the order in which events occurred. We suggest that the MTL is especially important for accessing global information about events and the relationships among their elements.

Social communication assessment after TBI: a narrative review of innovations in pragmatic and discourse assessment methods

BACKGROUND

Social communication assessment after traumatic brain injury (TBI) remains a challenging area within speech-language pathology (SLP) clinical practice. Difficulties include the lack of TBI-specific standardized assessment instruments and limited knowledge and uptake of discourse assessment methods clinically. The aim of this paper was to review recent research literature reporting on innovative social communication and discourse assessment measures and methods, to guide evidence-based SLP practice and inform future research.

MAIN CONTRIBUTION

This review describes novel standardized and non-standardized assessment tools for SLP use reported in TBI research literature from the past 15 years. Measures include published assessment batteries and pragmatic rating scales designed for use with adults with TBI, and novel discourse tasks and protocols.

CONCLUSION

This paper delineates social communication assessment measures and discourse analyses described in research literature that may be practical for SLPs to use with adults with TBI. The clinical implications and utility of these measures are discussed. This should assist SLPs in decision-making on social communication assessment for adults with TBI. Further research is needed to investigate translation of research knowledge on discourse assessment methods to SLP practice.

Unraveling the linguistic nature of specific autobiographical memories using a computerized classification algorithm

In the present study, we explored the linguistic nature of specific memories generated with the Autobiographical Memory Test (AMT) by developing a computerized classifier that distinguishes between specific and nonspecific memories. The AMT is regarded as one of the most important assessment tools to study memory dysfunctions (e.g., difficulty recalling the specific details of memories) in psychopathology. In Study 1, we utilized the Japanese corpus data of 12,400 cue-recalled memories tagged with observer-rated specificity. We extracted linguistic features of particular relevance to memory specificity, such as past tense, negation, and adverbial words and phrases pertaining to time and location. On the basis of these features, a support vector machine (SVM) was trained to classify the memories into specific and nonspecific categories, which achieved an area under the curve (AUC) of .92 in a performance test. In Study 2, the trained SVM was tested in terms of its robustness in classifying novel memories (n = 8,478) that were retrieved in response to cue words that were different from those used in Study 1. The SVM showed an AUC of .89 in classifying the new memories. In Study 3, we extended the binary SVM to a five-class classification of the AMT, which achieved 64%-65% classification accuracy, against the chance level (20%) in the performance tests. Our data suggest that memory specificity can be identified with a relatively small number of words, capturing the universal linguistic features of memory specificity across memories in diverse contents.

The hippocampus facilitates integration within a symbolic field

This paper attempts to elaborate a fundamental brain mechanism involved in the creation and maintenance of symbolic fields of thought. It will integrate theories of psychic spaces as explored by Donald Winnicott and Wilfred Bion with the neuroscientific examinations of those with bilateral hippocampal injury to show how evidence from both disciplines sheds important light on this aspect of mind. Possibly originating as a way of maintaining an oriented, first person psychic map, this capacity allows individuals a dynamic narrative access to a realm of layered elements and their connections. If the proposed hypothesis is correct, the hippocampus facilitates the integration of this symbolic field of mind, where narrative forms of thinking, creativity, memory, and dreaming are intertwined. Without the hippocampus, there is an inability to engage many typical forms of thought itself. Also, noting the ways these individuals are not impaired supports theories about other faculties of mind, providing insight into their possible roles within human thought. The evidence of different systems working in conjunction with the symbolic field provides tantalizing clues about these fundamental mechanisms of brain and mind that are normally seamlessly integrated, and hints at future areas of clinical and laboratory research, both within neuroscience and psychoanalysis.

Dynamic Hippocampal and Prefrontal Contributions to Memory Processes and Representations Blur the Boundaries of Traditional Cognitive Domains

The hippocampus has long been known to be a critical component of the memory system involved in the formation and use of long-term declarative memory. However, recent findings have revealed that the reach of hippocampal contributions extends to a variety of domains and tasks that require the flexible use of cognitive and social behavior, including domains traditionally linked to prefrontal cortex (PFC), such as decision-making. In addition, the prefrontal cortex (PFC) has gained traction as a necessary part of the memory system. These findings challenge the conventional characterizations of hippocampus and PFC as being circumscribed to traditional cognitive domains. Here, we emphasize that the ability to parsimoniously account for the breadth of hippocampal and PFC contributions to behavior, in terms of memory function and beyond, requires theoretical advances in our understanding of their characteristic processing features and mental representations. Notably, several literatures exist that touch upon this issue, but have remained disjointed because of methodological differences that necessarily limit the scope of inquiry, as well as the somewhat artificial boundaries that have been historically imposed between domains of cognition. In particular, this article focuses on the contribution of relational memory theory as an example of a framework that describes both the representations and processes supported by the hippocampus, and further elucidates the role of the hippocampal–PFC network to a variety of behaviors.

Hippocampal declarative memory supports gesture production: Evidence from amnesia

Spontaneous co-speech hand gestures provide a visuospatial representation of what is being communicated in spoken language. Although it is clear that gestures emerge from representations in memory for what is being communicated (De Ruiter, 1998; Wesp, Hesse, Keutmann, & Wheaton, 2001), the mechanism supporting the relationship between gesture and memory is unknown. Current theories of gesture production posit that action - supported by motor areas of the brain - is key in determining whether gestures are produced. We propose that when and how gestures are produced is determined in part by hippocampally-mediated declarative memory. We examined the speech and gesture of healthy older adults and of memory-impaired patients with hippocampal amnesia during four discourse tasks that required accessing episodes and information from the remote past. Consistent with previous reports of impoverished spoken language in patients with hippocampal amnesia, we predicted that these patients, who have difficulty generating multifaceted declarative memory representations, may in turn have impoverished gesture production. We found that patients gestured less overall relative to healthy comparison participants, and that this was particularly evident in tasks that may rely more heavily on declarative memory. Thus, gestures do not just emerge from the motor representation activated for speaking, but are also sensitive to the representation available in hippocampal declarative memory, suggesting a direct link between memory and gesture production.

What relates newspaper, definite, and clothing? An article describing deficits in convergent problem solving and creativity following hippocampal damage

Creativity relies on a diverse set of cognitive processes associated with distinct neural correlates, and one important aspect of creativity, divergent thinking, has been associated with the hippocampus. However, hippocampal contributions to another important aspect of creativity, convergent problem solving, have not been investigated. We tested the necessity of hippocampus for convergent problem solving using a neuropsychological method. Participants with amnesia due to hippocampal damage (N = 5) and healthy normal comparison participants (N = 5) were tested using a task that promoted solutions based on existing knowledge (Bowden and Jung-Beeman, 2003). During each trial, participants were given a list of three words (e.g., fly, man, place) and asked to respond with a word that could be combined with each of the three words (e.g., fire). The amnesic group produced significantly fewer correct responses than the healthy comparison group. These findings indicate that the hippocampus is necessary for normal convergent problem solving and that changes in the status of the hippocampus should affect convergent problem solving in the context of creative problem-solving across short intervals. This proposed contribution of the hippocampus to convergent problem solving is consistent with an expanded perspective on hippocampal function that acknowledges its role in cognitive processes beyond declarative memory. © 2016 Wiley Periodicals, Inc.

Neuropsychological Assessment of Hippocampal Integrity

Finding methods to describe subcortical processes assisting cognition is an important concern for clinical neuropsychological practice. In this study, we reviewed the literature concerning the relationship between a neuropsychological instrument and the underlying neural substructure. We examined evidence indicating that one of the oldest neuropsychological tests still in use, the Rey Auditory Verbal Learning Test (RAVLT), includes reliable indicators of hippocampal integrity. We reviewed studies investigating the neural structures underlying seven tasks generated by the RAVLT, from the perspective of whether the performance of these tasks is dependent on the hippocampus. We found support for our hypothesis in five cases: learning capacity, proactive interference, immediate recall, delayed recall, and delayed recognition. No support for our hypothesis was found with regard to short-term memory and retroactive interference. The RAVLT appears to be a reliable tool for assessing the integrity of the hippocampus and for the early detection of dysfunction. There is a need for such assessments, due to the crucial role of the hippocampus in cognition, for instance, in terms of predicting future outcomes.

Creativity, Comprehension, Conversation and the Hippocampal Region: New Data and Theory

Present findings indicate that hippocampal region (HR) damage impairs aspects of everyday language comprehension and production that require creativity ^___ defined as the ability to form new internal representations that satisfy relevant constraints for being useful or valuable in the real world. In two studies, seventeen people participated in extensive face-to-face interviews: sixteen normal individuals and H.M., an amnesic with cerebellar and HR damage but virtually no neocortical damage. Study 1 demonstrated deficits in H.M.'s comprehension of creative but not routine aspects of the interviews ^___ extending to the real world twelve prior demonstrations that H.M. understands routine but not novel aspects of experimentally constructed sentences, deficits that reflected his HR damage, but not his cerebellar damage, his explicit or declarative memory problems, inability to comprehend or recall the instructions, forgetting, poor visual acuity, motoric slowing, time pressure, deficits in visual scanning or attentional allocation, lack of motivation, and excessive memory load in the tasks. Study 2 demonstrated similar deficits in H.M.'s ability to produce creative but not routine aspects of conversational discourse, extending findings in five prior sentence production experiments to real-world creativity. We discuss conceptual frameworks for explaining relations between new-and-useful creativity and the HR.

Navigating life

The discoveries of "place cells" in the hippocampus and "grid cells" in the entorhinal cortex are landmark achievements in relating behavior to neural activity, permitting analysis of a powerful system for spatial representation in the brain. The contributions of this work include not only the empirical findings but also the approach this work pioneered of examining neural activity in complex behaviors with real ecological validity in freely moving animals, and of attempting to place the findings in the larger context of how the neural representations of space are used in service of real-world behavior, namely what the Nobel committee described as permitting us to "navigate our way through a complex environment." These discoveries and approaches have had far-ranging impact on and implications for work in human cognitive neuroscience, where we see (1) confirmation in humans that the hippocampus and overlying MTL cortex are critically engaged in supporting a relational representation of space, and that it can be used for flexible spatial navigation and (2) evidence that these regions are also critically involved in aspects of relational memory not limited to space, and in the flexible use of hippocampal memory extending beyond spatial navigation. Recent work, using tasks that emphasize the requirement for the active use of memory in online processing, just as spatial navigation has long placed such a requirement on rodents, suggests that the hippocampus and related MTL cortex can support the navigating of environments even more complex than what is needed in spatial navigation. It allows us to use memory in guiding upcoming actions and choices to act optimally in and on the world, permitting us to navigate life in all its beautiful complexity.

Can we reconcile the declarative memory and spatial navigation views on hippocampal function?

Some argue that hippocampus supports declarative memory, our capacity to recall facts and events, whereas others view the hippocampus as part of a system dedicated to calculating routes through space, and these two contrasting views are pursued largely independently in current research. Here we offer a perspective on where these views can and cannot be reconciled and update a bridging framework that will improve our understanding of hippocampal function.

The role of the hippocampus in flexible cognition and social behavior

Successful behavior requires actively acquiring and representing information about the environment and people, and manipulating and using those acquired representations flexibly to optimally act in and on the world. The frontal lobes have figured prominently in most accounts of flexible or goal-directed behavior, as evidenced by often-reported behavioral inflexibility in individuals with frontal lobe dysfunction. Here, we propose that the hippocampus also plays a critical role by forming and reconstructing relational memory representations that underlie flexible cognition and social behavior. There is mounting evidence that damage to the hippocampus can produce inflexible and maladaptive behavior when such behavior places high demands on the generation, recombination, and flexible use of information. This is seen in abilities as diverse as memory, navigation, exploration, imagination, creativity, decision-making, character judgments, establishing and maintaining social bonds, empathy, social discourse, and language use. Thus, the hippocampus, together with its extensive interconnections with other neural systems, supports the flexible use of information in general. Further, we suggest that this understanding has important clinical implications. Hippocampal abnormalities can produce profound deficits in real-world situations, which typically place high demands on the flexible use of information, but are not always obvious on diagnostic tools tuned to frontal lobe function. This review documents the role of the hippocampus in supporting flexible representations and aims to expand our understanding of the dynamic networks that operate as we move through and create meaning of our world.

Learning in Alzheimer's disease is facilitated by social interaction

Seminal work in Gary Van Hoesen's laboratory at Iowa in the early 1980s established that the hallmark neuropathology of Alzheimer's disease (AD; neurofibrillary tangles) had its first foothold in specific parts of the hippocampal formation and entorhinal cortex, effectively isolating the hippocampus from much of its input and output and causing the distinctive impairment of new learning that is the leading early characteristic of the disease (Hyman et al., 1984). The boundaries and conditions of the anterograde memory defect in patients with AD have been a topic of intense research interest ever since (e.g., Graham and Hodges, 1977; Nestor et al., 2006). For example, it has been shown that patients with AD may acquire some new semantic information through methods such as errorless learning, but learning under these conditions is typically slow and inefficient. Drawing on a learning paradigm (a collaborative referencing task) that was previously shown to induce robust and enduring learning in patients with hippocampal amnesia, we investigated whether this task would be effective in promoting new learning in patients with AD. We studied five women with early-stage AD and 10 demographically matched healthy comparison participants, each interacting with a familiar communication partner. AD pairs displayed significant and enduring learning across trials, with increased accuracy and decreased time to complete trials, in a manner indistinguishable from healthy comparison pairs, resulting in efficient and economical communication. The observed learning here most likely draws on neural resources outside the medial temporal lobes. These interactive communication sessions provide a potent learning environment with significant implications for memory intervention.

Older adults catch up to younger adults on a learning and memory task that involves collaborative social interaction

Learning and memory abilities tend to decline as people age. The current study examines the question of whether a learning situation that emphasises collaborative social interaction might help older persons overcome age-related learning and memory changes and thus perform similarly to younger persons. Younger and Older participants (n = 34 in each group) completed the Barrier Task (BT), a game-like social interaction where partners work together to develop labels for a set of abstract tangrams. Participants were also administered standard clinical neuropsychological measures of memory, on which the Older group showed expected inferiority to the Younger group. On the BT, the Older group performed less well than the Younger group early on, but as the task progressed, the performance of the Older group caught up and became statistically indistinguishable from that of the Younger group. These results can be taken to suggest that a learning milieu characterised by collaborative social interaction can attenuate some of the typical memory disadvantages associated with being older.

Multiple Memory Systems and Their Support of Language

There is a long history of research linking the various forms of memory to different aspects of language. Clinically, we see this memory-language connection in the prevalence of language and communication deficits in populations that have concomitant impairments in memory and learning. In this article, we provide an overview of how the demands of language use and processing are supported by multiple memory systems in the brain, including working memory, declarative memory and nondeclarative memory, and how disruptions in different forms of memory may affect language. While not an exhaustive review of the literature, special attention is paid to populations who speech-language pathologists (SLPs) routinely serve. The goal of this review is to provide a resource for clinicians working with clients with disorders in memory and learning in helping to understand and anticipate the range of disruptions in language and communication that can arise as a consequence of memory impairment. We also hope this is a catalyst for more research on the contribution of multiple memory systems to language and communication.

Verbal play as a discourse resource in the social interactions of older and younger communication pairs

Verbal play, or the playful manipulation of elements of language, is a pervasive component of social interaction, serving important interpersonal functions. We analyzed verbal play in the interactional discourse of ten healthy younger pairs and ten healthy older pairs as they completed a collaborative referencing task. A total of 1,893 verbal play episodes were coded. While there were no group differences in verbal play frequency, age-related differences in the quality and function of these episodes emerged. While older participants engaged in more complex, extended, and reciprocal episodes that supported the social nature of communicative interactions (e.g., teasing), younger participants were more likely to engage in verbal play episodes for the purpose of successful task completion. Despite these age-related variations in the deployment of verbal play, verbal play is a robust interactional discourse resource in healthy aging, highlighting an element of human cognition that does not appear to decline with age.

Hippocampal amnesia disrupts creative thinking

Creativity requires the rapid combination and recombination of existing mental representations to create novel ideas and ways of thinking. The hippocampal system, through its interaction with neocortical storage sites, provides a relational database necessary for the creation, updating, maintenance, and juxtaposition of mental representations used in service of declarative memory. Given this functionality, we hypothesized that hippocampus would play a critical role in creative thinking. We examined creative thinking, as measured by verbal and figural forms of the torrance tests of creative thinking (TTCT), in a group of participants with hippocampal damage and severe declarative memory impairment as well as in a group of demographically matched healthy comparison participants. The patients with bilateral hippocampal damage performed significantly worse than comparison participants on both the verbal and figural portions of the TTCT. These findings suggest that hippocampus plays a role critical in creative thinking, adding to a growing body of work pointing to the diverse ways the hallmark processing features of hippocampus serve a variety of behaviors that require flexible cognition.

Memory as social glue: close interpersonal relationships in amnesic patients

Memory may be crucial for establishing and/or maintaining social bonds. Using the National Social life, Health, and Aging Project questionnaire, we examined close interpersonal relationships in three amnesic people: K.C. and D.A. (who are adult-onset cases) and H.C. (who has developmental amnesia). All three patients were less involved than demographically matched controls with neighbors and religious and community groups. A higher-than-normal percentage of the adult-onset (K.C. and D.A.) cases’ close relationships were with family members, and they had made few new close friends in the decades since the onset of their amnesia. On the other hand, the patient with developmental amnesia (H.C.) had forged a couple of close relationships, including one with her fiancé. Social networks appear to be winnowed, but not obliterated, by amnesia. The obvious explanation for the patients’ reduced social functioning stems from their memory impairment, but we discuss other potentially important factors for future study.

Impaired social decision making in patients with major depressive disorder

Research on how depression influences social decision making has been scarce. This study investigated how people with depression make decisions in an interpersonal trust-reciprocity game. Fifty female patients diagnosed with major depressive disorders (MDDs) and 49 healthy women participated in this study. The experiment was conducted on a one-to-one basis. Participants were asked to play the role of a trustee responsible for investing money given to them by an anonymous female investor playing on another computer station. In each trial, the investor would send to a participant (the trustee) a request for a certain percentage of the appreciated investment (repayment proportion). Since only the participant knew the exact amount of the appreciated investment, she could decide to pay more (altruistic act), the same, or less (deceptive act) than the requested amount. The participant's money acquired in the trial would be confiscated if her deceptive act was caught. The frequency of deceptive or altruistic decisions and relative monetary gain in each decision choice were examined. People with depression made fewer deceptive and fewer altruistic responses than healthy controls in all conditions. Moreover, the specific behavioral pattern presented by people with depression was modulated by the task factors, including the risk of deception detection and others' intentions (benevolence vs. malevolence). Findings of this study contribute to furthering our understanding of the specific pattern of social behavioral changes associated with depression.

Hippocampal temporal-parietal junction interaction in the production of psychotic symptoms: a framework for understanding the schizophrenic syndrome

A framework is described for understanding the schizophrenic syndrome at the brain systems level. It is hypothesized that over-activation of dynamic gesture and social perceptual processes in the temporal-parietal occipital junction (TPJ), posterior superior temporal sulcus (PSTS) and surrounding regions produce the syndrome (including positive and negative symptoms, their prevalence, prodromal signs, and cognitive deficits). Hippocampal system hyper-activity and atrophy have been consistently found in schizophrenia. Hippocampal activity is highly correlated with activity in the TPJ and may be a source of over-excitation of the TPJ and surrounding regions. Strong evidence for this comes from in-vivo recordings in humans during psychotic episodes. Many positive symptoms of schizophrenia can be reframed as the erroneous sense of a presence or other who is observing, acting, speaking, or controlling; these qualia are similar to those evoked during abnormal activation of the TPJ. The TPJ and PSTS play a key role in the perception (and production) of dynamic social, emotional, and attentional gestures for the self and others (e.g., body/face/eye gestures, audiovisual speech and prosody, and social attentional gestures such as eye gaze). The single cell representation of dynamic gestures is multimodal (auditory, visual, tactile), matching the predominant hallucinatory categories in schizophrenia. Inherent in the single cell perceptual signal of dynamic gesture representations is a computation of intention, agency, and anticipation or expectancy (for the self and others). Stimulation of the TPJ resulting in activation of the self representation has been shown to result a feeling of a presence or multiple presences (due to heautoscopy) and also bizarre tactile experiences. Neurons in the TPJ are also tuned, or biased to detect threat related emotions. Abnormal over-activation in this system could produce the conscious hallucination of a voice (audiovisual speech), a person or a touch. Over-activation could interfere with attentional/emotional gesture perception and production (negative symptoms). It could produce the unconscious feeling of being watched, followed, or of a social situation unfolding along with accompanying abnormal perception of intent and agency (delusions). Abnormal activity in the TPJ would also be predicted to create several cognitive disturbances that are characteristic of schizophrenia, including abnormalities in attention, predictive social processing, working memory, and a bias to erroneously perceive threat.

The hippocampus and the flexible use and processing of language

Fundamental to all human languages is an unlimited expressive capacity and creative flexibility that allow speakers to rapidly generate novel and complex utterances. In turn, listeners interpret language “on-line,” incrementally integrating multiple sources of information as words unfold over time. A challenge for theories of language processing has been to understand how speakers and listeners generate, gather, integrate, and maintain representations in service of language processing. We propose that many of the processes by which we use language place high demands on and receive contributions from the hippocampal declarative memory system. The hippocampal declarative memory system is long known to support relational binding and representational flexibility. Recent findings demonstrate that these same functions are engaged during the real-time processes that support behavior in-the-moment. Such findings point to the hippocampus as a potentially key contributor to cognitive functions that require on-line integration of multiple sources of information, such as on-line language processing. Evidence supporting this view comes from findings that individuals with hippocampal amnesia show deficits in the use of language flexibly and on-line. We conclude that the relational binding and representational flexibility afforded by the hippocampal declarative memory system positions the hippocampus as a key contributor to language use and processing.

Verbal Play as an Interactional Discourse Resource in Early Stage Alzheimer's Disease

BACKGROUND: Verbal play, the creative and playful use of language to make puns, rhyme words, and tease, is a pervasive and enjoyable component of social communication and serves important interpersonal functions. The current study examines the use of verbal play in the communicative interactions of individuals with Alzheimer's disease as part of a broader program of research on language-and-memory-in-use. AIMS: To document the frequency of verbal play in the communicative interactions of individuals with very mild Alzheimer's disease (AD) and their familiar communication partners. To characterize the interactional forms, resources, and functions of playful episodes. METHODS: Using quantitative group comparisons and detailed discourse analysis, we analyzed verbal play in the interactional discourse of five participants with very mild AD and five healthy (demographically matched) comparison participants. Each participant interacted with a familiar partner while completing a collaborative referencing task, and with a researcher between task trials. RESULTS: A total of 1,098 verbal play episodes were coded. Despite being in the early stages of AD, all the AD participants used verbal play. There were no significant group differences in the frequency of verbal play episodes or in the interactional forms, resources, or functions of those playful episodes between AD and healthy comparison pair sessions. CONCLUSIONS: The successful use of verbal play in the interactions of individuals with very mild AD and their partners highlights an area of preserved social communication. These findings represent an important step, both clinically and for research, in documenting the rich ways that individuals with early stage AD orchestrate interactionally meaningful communication with their partners through the use of interactional discourse resources like verbal play. This work also offers a promising clinical tool for tracking and targeting verbal play across disease progression.

Ventromedial prefrontal cortex damage does not impair the development and use of common ground in social interaction: implications for cognitive theory of mind

During conversation, interactants draw on their shared communicative context and history ("common ground") to help decide what to say next, tailoring utterances based on their knowledge of what the listener knows. The use of common ground draws on an understanding of the thoughts and feelings of others to create and update a model of what is known by the other person, employing cognitive processes such as theory of mind. We tested the hypothesis that the ventromedial prefrontal cortex (vmPFC), a neural region involved in processing and interpreting social and emotional information, would be critical for the development and use of common ground. We studied seven patients with bilateral vmPFC damage and seven age-, sex-, and education-matched healthy comparison participants, each interacting with a familiar partner. Across 24 trials, participants verbally directed their partners how to arrange a set of 12 abstract tangram cards. Our hypothesis was not supported: the vmPFC and healthy comparison groups showed similar development and use of common ground, evident in reduction in time and words used to describe the cards, similar increases in the use of definite references (e.g., the horse), and comparable use of verbal play (playful language) in their interactions. These results argue against the idea that the vmPFC is critical for the development and use of common ground in social interaction. We propose that a cognitive and neuroanatomical bifurcation in theory of mind processes may explain this outcome. The vmPFC may be important for affective theory of mind (the ability to understand another's feelings); however, the development and use of common ground in social interaction may place higher demands on the ability to understand another's knowledge, or cognitive theory of mind, which may not require the vmPFC.

Teasing apart tangrams: testing hippocampal pattern separation with a collaborative referencing paradigm

The hippocampus and the medial temporal lobe cortex [medial temporal lobe cortices (MTLC)] both contribute to long-term memory. Although their contributions are thought to be dissociable, the nature of the representations that each region supports remains unclear. The Complementary Learning Systems (CLS) modeling approach suggests that hippocampus represents overlapping information in a sparser and therefore more separated fashion than MTLC. We tested this prediction using a collaborative referencing paradigm whereby hippocampal amnesic patients and a partner work together to develop and use unique labels for a set of abstract visual stimuli (tangrams) across extended interactions. Previously, we reported that amnesic patients demonstrate intact learning when the tangrams are conceptually dissimilar. Here, we manipulated the degree of visual similarity; half of the stimuli were dissimilar to one another (e.g., camel and giraffe), and half were similar (e.g., birds). We hypothesized that while patients would have little difficulty with the dissimiliar tangrams (quickly arriving at unique and concise labels), they would be unable to rapidly form distinct representations of highly similar visual patterns. Consistent with this prediction, patients and both healthy and brain-damaged comparison participants showed similar rates of learning for dissimilar tangrams, but the similar tangrams proved more difficult for hippocampal patients as reflected in the greater number of words they used to describe each similar card. This result supports the CLS model's central claim of hippocampal specialization for pattern separation and suggests that our collaborative referencing paradigm may be a useful tool for observing extended encoding of complex representations.

Bilateral amygdala damage impairs the acquisition and use of common ground in social interaction

OBJECTIVE

The development of "common ground," or mutual knowledge of shared information, is believed to require the ability to update a mental representation of another person's thoughts and knowledge based on verbal information and nonverbal social and emotional signals, to facilitate economical communication. As in other forms of everyday social communication, the development of common ground likely requires the orchestration of multiple cognitive processes supported by various neural systems. Here, we investigate the contribution of the amygdala to these processes.

METHOD

SM, a patient with complete, focal, bilateral amygdala damage, and deficits in social and emotional processing, and five healthy comparison participants, each interacted with a familiar partner. We investigated the participants' ability to develop and use referential labels across 24 dynamic, collaborative interactions. Participants verbally directed their partner how to arrange a set of 12 abstract tangrams while separated by a low barrier, allowing them to see each other but hiding their tangrams.

RESULTS

In contrast to comparison participants, SM exhibited an impaired rate of learning across trials and did not show the typical simplification in the labels generated during the interactions. Detailed analyses of SM's interactional discourse and social behavior suggested that she has impaired perspective-taking or what can be interpreted as deficient "theory of mind," manifested in abnormal "language-in-use."

CONCLUSIONS

These results support the conclusion that the amygdala, a structure critical for social and emotional processing, plays an important role in the acquisition and use of common ground and in social communication more broadly.

Distributed impact of cognitive-communication impairment: Disruptions in the use of definite references when speaking to individuals with amnesia

BACKGROUND: Definite references signal a speaker's belief that a listener can uniquely identify the referent (e.g., the dog, as the only dog among a group of animals). Clark's (1992) collaborative referencing model provides a way to examine the speaker's display of confidence that his/her reference will be understood by the listener without further clarification. We previously found that amnesia participants, as directors in a barrier task with a familiar partner, used referencing forms that displayed less confidence than forms used by comparison participants. If this is an interactional consequence of managing the memory impairment (as opposed to a language deficit), we should also expect a decrease in definite referencing by their partners. AIMS: To examine the use of definite references by healthy non-brain-damaged participants when speaking to their memory-impaired partner during repeated trials of a barrier task. METHODS #ENTITYSTARTX00026; PROCEDURES: We replicated our previous work with 11 of the same participant pairs-6 individuals with hippocampal amnesia and 5 comparison participants-each of whom was paired with a familiar partner of their choosing. Focusing on the productions of the partners (i.e., partners became directors) we (1) coded referential expressions as definite or indefinite; (2) tracked changes in the use of indefinite and definite references across trials; and (3) compared data to previous analyses (when amnesia participants were directors). OUTCOMES #ENTITYSTARTX00026; RESULTS: The productions of comparison pairs were overwhelming definite (95%, 1359). In sharp contrast, partners of the amnesia participants used a definite initiating reference less than half the time (48%, 825), when speaking to their memory-impaired partner and used definite references that signalled a lack of confidence more often and across more trials. CONCLUSIONS: These findings support the assumption that disruptions in language-and-memory-in-use are not limited to the productions of the individuals with amnesia, but rather extend to the discourse of their communication partners. Observing disruptions in the use of definite references of individuals with intact language and declarative memory, when communicating with their partner with amnesia, points to the complex interaction of memory and language. Even when attention is paid to grammatical forms, the decisions are never linguistic alone.

The use of definite references signals declarative memory: evidence from patients with hippocampal amnesia

Language function in patients with impaired declarative memory presents a compelling opportunity to investigate the inter-dependence of memory and language in referential communication. We examined amnesic patients' use of definite references during a referential communication task. Discursively, definite references can be used to mark a referent as situationally unique (e.g., "the game," as in the case of a recently publicized game) or as shared information (e.g., "the game," as in one discussed previously). We found that despite showing normal collaborative learning after repeated referring-as indexed by consistent and increasingly efficient descriptive labels for previously unfamiliar tangram figures-amnesic patients did not consistently use definite references in referring to those figures. The use of definite references seems to be critically dependent on declarative memory, and the engagement of such memory is signaled by language.

Cohesion, coherence, and declarative memory: Discourse patterns in individuals with hippocampal amnesia

BACKGROUND: Discourse cohesion and coherence gives our communication continuity. Deficits in cohesion and coherence have been reported in patients with cognitive-communication disorders (e.g., TBI, dementia). However, the diffuse nature of pathology and widespread cognitive deficits of these disorders have made identification of specific neural substrates and cognitive systems critical for cohesion and coherence challenging. AIMS: Taking advantage of a rare patient group with selective and severe declarative memory impairments, the current study attempts to isolate the contribution of declarative memory to the successful use of cohesion and coherence in discourse. METHODS #ENTITYSTARTX00026; PROCEDURES: Cohesion and coherence were examined in the discourse of six participants with hippocampal amnesia and six demographically matched comparison participants. Specifically, this study (1) documents the frequency, type, and completeness of cohesive ties; (2) evaluates discourse for local and global coherence; and (3) compares use of cohesive ties and coherence ratings in amnesia and healthy participants. OUTCOMES #ENTITYSTARTX00026; RESULTS: Overall, amnesia participants produced fewer cohesive ties per T-unit, the adequacy of their ties were more often judged to be incomplete, and the ratings of their local coherence were consistently lower than comparison participants. CONCLUSIONS: These findings suggest that declarative memory may contribute to the discursive use of cohesion and coherence. Broader notions of cohesion, or interactional cohesion, i.e., cohesion across speakers (two or more people), time (days, weeks), and communicative resources (gesture), warrant further study as the experimental tasks used in the literature, and here, may actually underestimate or overestimate the extent of impairment.