Touch Healing (TH) therapies, defined here as treatments whose primary route of administration is tactile contact and/or active guiding of somatic attention, are ubiquitous across cultures. Despite increasing integration of TH into mainstream medicine through therapies such as Reiki, Therapeutic Touch,TM and somatically focused meditation practices such as Mindfulness-Based Stress Reduction, relatively little is known about potential underlying mechanisms. Here, we present a neuroscientific explanation for the prevalence and effectiveness of TH therapies for relieving chronic pain. We begin with a cross-cultural review of several different types of TH treatments and identify common characteristics, including: light tactile contact and/or a somatosensory attention directed toward the body, a behaviorally relevant context, a relaxed context and repeated treatment sessions. These cardinal features are also key elements of established mechanisms of neural plasticity in somatosensory cortical maps, suggesting that sensory reorganization is a mechanism for the healing observed. Consideration of the potential health benefits of meditation practice specifically suggests that these practices provide training in the regulation of neural and perceptual dynamics that provide ongoing resistance to the development of maladaptive somatic representations. This model provides several direct predictions for investigating ways that TH may induce cortical plasticity and dynamics in pain remediation.

SummaryObjectives
To investigate neural representation evoked by acupuncture from human somatosensory cortices, especially from primary (SI) and secondary (SII) somatosensory areas.
Design and setting
Neuroimaging study – Blood-oxygenation-level-dependent (BOLD) functional MRI was performed during acupuncture on LI4 (n = 12 healthy participants). Sham acupuncture and innocuous tactile stimulation were also applied on the same acupuncture site as control comparisons.
Outcome measures
Responsive neural substrates were visualized and identified based on both individual and group-level surface activation maps.
Results
Discrete regions within the precentral gyrus (area 4) and the fundus of the central sulcus (area 3a) were selectively activated during the real acupuncture stimulation. In SII, the activation was extended in a postero-inferior direction to the fundus of the lateral sulcus.
Conclusion
This specific pattern of acupuncture-related activation indicates that deep tissue stimulation (as seen in area 3a activation) and concurrent processing of sensory stimulation (as seen in activation in SII) may mediate neural responses to manual acupuncture.

Few complementary and alternative medicine (CAM) institutions require their students to undergo substantive training in research literacy and conduct, and well-developed programs to train CAM institution faculty in research are virtually non-existent. As part of a National Center for Complementary and Alternative Medicine (NCCAM) initiative to increase research capacity at CAM institutions, the New England School of Acupuncture (NESA), in collaboration with the Harvard Medical School (HMS) Osher Institute, was awarded a Developmental Center for Research on Complementary and Alternative Medicine (DCRC) grant. This article discusses a number of initiatives that we designed and implemented to train NESA students, faculty members, and alumni in the foundations of clinical research and to stimulate interest in both participating in research and receiving additional research training. Specific initiatives included a 30-hour faculty "Foundations of Research" course; a year-long course entitled, "How to Write a Publishable Case Report"; institution of a monthly research seminar series; revision of an already required student research course; and the addition of 2 new student-mentored independent research electives. We discuss successes and challenges encountered in developing and administering these initiatives and the overall impact they have had on research culture and productivity at NESA.

A successful clinical trial is dependent on recruitment. Between December 2003 and February 2006, our team successfully enrolled 289 participants in a large, single-center, randomized placebo-controlled trial (RCT) studying the impact of the patient-doctor relationship and acupuncture on irritable bowel syndrome (IBS) patients. This paper reports on the effectiveness of standard recruitment methods such as physician referral, newspaper advertisements, fliers, audio and video media (radio and television commercials) as well as relatively new methods not previously extensively reported on such as internet ads, ads in mass-transit vehicles and movie theater previews. We also report the fraction of cost each method consumed and fraction of recruitment each method generated. Our cost per call from potential participants varied from $3–$103 and cost per enrollment participant varied from $12–$584. Using a novel metric, the efficacy index, we found that physician referrals and flyers were the most effective recruitment method in our trial. Despite some methods being more efficient than others, all methods contributed to the successful recruitment. The iterative use of the efficacy index during a recruitment campaign may be helpful to calibrate and focus on the most effective recruitment methods.

The scientific discovery of novel training paradigms has yielded better understanding of basic mechanisms underlying cortical plasticity, learning and development. This study is a first step in evaluating Tai Chi (TC), the Chinese slow-motion meditative exercise, as a training paradigm that, while not engaging in direct tactile stimulus training, elicits enhanced tactile acuity in long-term practitioners. The rationale for this study comes from the fact that, unlike previously studied direct-touch tactile training paradigms, TC practitioners focus specific mental attention on the body’s extremities including the fingertips and hands as they perform their slow routine. To determine whether TC is associated with enhanced tactile acuity, experienced adult TC practitioners were recruited and compared to age–gender matched controls. A blinded assessor used a validated method (Van Boven et al. in Neurology 54(12): 2230–2236, 2000) to compare TC practitioners’ and controls’ ability to discriminate between two different orientations (parallel and horizontal) across different grating widths at the fingertip. Study results showed that TC practitioners’ tactile spatial acuity was superior to that of the matched controls (P < 0.04). There was a trend showing TC may have an enhanced effect on older practitioners (P < 0.066), suggesting that TC may slow age related decline in this measure. To the best of our knowledge, this is the first study to evaluate a long-term attentional practice’s effects on a perceptual measure. Longitudinal studies are needed to examine whether TC initiates or is merely correlated with perceptual changes and whether it elicits long-term plasticity in primary sensory cortical maps. Further studies should also assess whether related somatosensory attentional practices (such as Yoga, mindfulness meditation and Qigong) achieve similar effects.

Study Objective
To assess feasibility, and collect preliminary data for a subsequent randomized, sham-controlled trial to evaluate Japanese-style acupuncture for reducing chronic pelvic pain and improving health-related quality of life (HRQOL) in adolescents with endometriosis.
Design
Randomized, sham-controlled trial.
Settings
Tertiary-referral hospital.
Participants
Eighteen young women (13–22y) with laparoscopically-diagnosed endometriosis-related chronic pelvic pain.
Interventions
A Japanese style of acupuncture and a sham acupuncture control. Sixteen treatments were administered over 8 weeks.
Main Outcome Measures
Protocol feasibility, recruitment numbers, pain not associated with menses or intercourse, and multiple HRQOL instruments including Endometriosis Health Profile, Pediatric Quality of Life, Perceived Stress, and Activity Limitation.
Results
Fourteen participants (out of 18 randomized) completed the study per protocol. Participants in the active acupuncture group (n = 9) experienced an average 4.8 (SD = 2.4) point reduction on a 11 point scale (62%) in pain after 4 weeks, which differed significantly from the control group's (n = 5) average reduction of 1.4 (SD = 2.1) points (P = 0.004). Reduction in pain in the active group persisted through a 6-month assessment; however, after 4 weeks, differences between the active and control group decreased and were not statistically significant. All HRQOL measures indicated greater improvements in the active acupuncture group compared to the control; however, the majority of these trends were not statistically significant. No serious adverse events were reported.
Conclusion
Preliminary estimates indicate that Japanese-style acupuncture may be an effective, safe, and well-tolerated adjunct therapy for endometriosis-related pelvic pain in adolescents. A more definitive trial evaluating Japanese-style acupuncture in this population is both feasible and warranted.

Mindfulness-based stress reduction (MBSR) is an 8-week training that is designed to teach participants mindful awareness of the present moment. In randomized clinical trials (RCTs), MBSR has demonstrated efficacy in various conditions including reducing chronic pain-related distress and improving quality of life in healthy individuals. There have, however, been no qualitative studies investigating participants' descriptions of changes experienced over multiple time points during the course of the programme. This qualitative study of an MBSR cohort (N = 8 healthy individuals) in a larger RCT examined participants' daily diary descriptions of their home-practice experiences. The study used a two-part method, combining grounded theory with a close-ended coding approach. The grounded theory analysis revealed that during the trial, all participants, to varying degrees, described moments of distress related to practice; at the end of the course, all participants who completed the training demonstrated greater detail and clarity in their descriptions, improved affect, and the emergence of an observing self. The closed-ended coding schema, carried out to shed light on the development of an observing self, revealed that the emergence of an observing self was not related to the valence of participants' experiential descriptions: even participants whose diaries contained predominantly negative characterizations of their experience throughout the trial were able, by the end of the trial, to demonstrate an observing, witnessing attitude towards their own distress. Progress in MBSR may rely less on the valence of participants' experiences and more on the way participants describe and relate to their own inner experience. Copyright © 2010 John Wiley & Sons, Ltd. Key Practitioner Message: This article • Analyses the ways in which participants in a mindfulness-based stress reduction (MBSR) clinical trial describe their experiences with mindfulness practice. • Carries out qualitative analysis of the ways in which participants' descriptions of home-based meditation practice contained in their practice diaries change over the course of an 8-week MBSR trial. • Demonstrates that the participants who successfully completed the 8-week course show a common developmental trajectory, as each participant used less reactive, judgemental language to describe their home meditative practice-based experiences by the end of the trial, even when, in the case of some participants, that experience was perceived as negative or distressing. • Suggests that progress in MBSR may rely less on the valence of participants' experience and more on the way participants describe and relate to their own inner experience.

Background
Behavioral paradigms applied during human recordings in electro- and magneto- encephalography (EEG and MEG) typically require 1–2 hours of data collection. Over this time scale, the natural fluctuations in brain state or rapid learning effects could impact measured signals, but are seldom analyzed.

Methods and Findings
We investigated within-session dynamics of neocortical alpha (7–14 Hz) rhythms and their allocation with cued-attention using MEG recorded from primary somatosensory neocortex (SI) in humans. We found that there were significant and systematic changes across a single ∼1 hour recording session in several dimensions, including increased alpha power, increased differentiation in attention-induced alpha allocation, increased distinction in immediate time-locked post-cue evoked responses in SI to different visual cues, and enhanced power in the immediate cue-locked alpha band frequency response. Further, comparison of two commonly used baseline methods showed that conclusions on the evolution of alpha dynamics across a session were dependent on the normalization method used.

Conclusions
These findings are important not only as they relate to studies of oscillations in SI, they also provide a robust example of the type of dynamic changes in brain measures within a single session that are overlooked in most human brain imaging/recording studies.

Using a common set of mindfulness exercises, mindfulness based stress reduction (MBSR) and mindfulness based cognitive therapy (MBCT) have been shown to reduce distress in chronic pain and decrease risk of depression relapse. These standardized mindfulness (ST-Mindfulness) practices predominantly require attending to breath and body sensations. Here, we offer a novel view of ST-Mindfulness's somatic focus as a form of training for optimizing attentional modulation of 7–14 Hz alpha rhythms that play a key role in filtering inputs to primary sensory neocortex and organizing the flow of sensory information in the brain. In support of the framework, we describe our previous finding that ST-Mindfulness enhanced attentional regulation of alpha in primary somatosensory cortex (SI). The framework allows us to make several predictions. In chronic pain, we predict somatic attention in ST-Mindfulness “de-biases” alpha in SI, freeing up pain-focused attentional resources. In depression relapse, we predict ST-Mindfulness's somatic attention competes with internally focused rumination, as internally focused cognitive processes (including working memory) rely on alpha filtering of sensory input. Our computational model predicts ST-Mindfulness enhances top-down modulation of alpha by facilitating precise alterations in timing and efficacy of SI thalamocortical inputs. We conclude by considering how the framework aligns with Buddhist teachings that mindfulness starts with “mindfulness of the body.” Translating this theory into neurophysiology, we hypothesize that with its somatic focus, mindfulness' top-down alpha rhythm modulation in SI enhances gain control which, in turn, sensitizes practitioners to better detect and regulate when the mind wanders from its somatic focus. This enhanced regulation of somatic mind-wandering may be an important early stage of mindfulness training that leads to enhanced cognitive regulation and metacognition.

Patient–physician interactions significantly contribute to placebo effects and clinical outcomes. While the neural correlates of placebo responses have been studied in patients, the neurobiology of the clinician during treatment is unknown. This study investigated physicians’ brain activations during patient–physician interaction while the patient was experiencing pain, including a ‘treatment‘, ‘no-treatment’ and ‘control’ condition. Here, we demonstrate that physicians activated brain regions previously implicated in expectancy for pain–relief and increased attention during treatment of patients, including the right ventrolateral and dorsolateral prefrontal cortices. The physician’s ability to take the patients’ perspective correlated with increased brain activations in the rostral anterior cingulate cortex, a region that has been associated with processing of reward and subjective value. We suggest that physician treatment involves neural representations of treatment expectation, reward processing and empathy, paired with increased activation in attention-related structures. Our findings further the understanding of the neural representations associated with reciprocal interactions between clinicians and patients; a hallmark for successful treatment outcomes.

OBJECTIVES: Adequate relief (AR) of irritable bowel syndrome (IBS) symptoms (IBS-AR) has been used as a primary end point in many randomized controlled trials of IBS and is considered by the Rome III committee to be an acceptable primary end point. However, controversy exists on whether baseline severity confounds the effect of the treatment outcome. The aim (1) is to compare a subjective report of IBS-AR with global assessment of improvement (IBS-GAI), change in IBS symptom severity scale (IBS-SSS), and IBS quality of life (IBS-QOL); (2) to explore whether initial IBS symptom severity influences the ability of these outcome measures to detect differences post treatment; and (3) to determine whether psychological symptoms influence the sensitivity of these measures, in a randomized controlled treatment trial.
METHODS: A total of 289 adult IBS patients were recruited to a treatment trial. Baseline IBS-SSS scores were used to classify IBS severity as mild (<175), moderate (175–300), or severe (>300). Questionnaires were completed at baseline and after 3 weeks of treatment with sham acupuncture or wait-list control.
RESULTS: IBS baseline severity (IBS-SSS) significantly affected the proportion of patients who reported IBS-AR at 3 weeks (mild, 70%; moderate, 49.7%; severe, 38.8%) (P<0.05). However, once the patients who reported IBS-AR at baseline (28.0%) were excluded from the analysis, baseline severity no longer affected the proportion of patients reporting IBS-AR. Baseline severity did not have a significant effect on patients reporting moderate or significant improvement on the IBS-GAI (mild, 30%; moderate, 25.3%; severe, 18.8%) (P=NS). Psychological symptoms had no significant correlations with responders after adjusting for baseline severity.
CONCLUSIONS: These data suggest that IBS-AR as an end point is inversely related to baseline symptom severity. However, if patients who report AR at screening were excluded from study participation, baseline symptom severity was no longer confounded with a report of AR at the study end point.

Patients in the placebo arms of randomized controlled trials (RCT) often experience positive changes from baseline. While multiple theories concerning such “placebo effects” exist, peculiarly, none has been informed by actual interviews of patients undergoing placebo treatment. Here, we report on a qualitative study (n = 27) embedded within a RCT (n = 262) in patients with irritable bowel syndrome. Besides identical placebo acupuncture treatment in the RCT, the qualitative study patients also received an additional set of interviews at the beginning, midpoint, and end of the trial. Interviews of the 12 qualitative subjects who underwent and completed placebo treatment were transcribed. We found that patients (1) were persistently concerned with whether they were receiving placebo or genuine treatment; (2) almost never endorsed “expectation” of improvement but spoke of “hope” instead and frequently reported despair; (3) almost all reported improvement ranging from dramatic psychosocial changes to unambiguous, progressive symptom improvement to tentative impressions of benefit; and (4) often worried whether their improvement was due to normal fluctuations or placebo effects. The placebo treatment was a problematic perturbation that provided an opportunity to reconstruct the experiences of the fluctuations of their illness and how it disrupted their everyday life. Immersion in this RCT was a co-mingling of enactment, embodiment and interpretation involving ritual performance and evocative symbols, shifts in bodily sensations, symptoms, mood, daily life behaviors, and social interactions, all accompanied by self-scrutiny and re-appraisal. The placebo effect involved a spectrum of factors and any single theory of placebo—e.g. expectancy, hope, conditioning, anxiety reduction, report bias, symbolic work, narrative and embodiment—provides an inadequate model to explain its salubrious benefits.

Simulations of human cognitive processes often employ discrimination nets to model the access of permanent memory. We consider two types of discrimination nets—EPAM and positive-proper-only nets—and argue that they have insufficient psychological validity. Their deficiencies arise from negative properties, insufficient sensitivity to the discriminativeness of properties, extreme sensitivity to missing or incorrect properties, inefficiency in representing multiple knowledge domains, and seriality. We argue that these deficiencies stem from a high degree of test contingency in utilizing property information during acquisition and memory search. Discrimination nets are compared to other models that have less or no test contingency (e.g., PANDEMONIUM) and that thereby avoid the problems of discrimination nets. We propose that understanding test contingency and discovering psychologically valid ways to implement it will be central to understanding and simulating memory indexing in human cognition.

Theories of memory organisation propose that activity knowledge organises autobiographical memory globally. According to these views, memories that share a participant, location, or time are only organised together if they also share an activity. If they do not, they are nested within their respective activity organisations locally rather than being organised together globally. Two experiments that assessed people's clustering of laboratory events consistently obtained findings that contradict this view. Both experiments found that people organise event memories globally in non-activity clusters, cross-classify events into multiple organisations, and pivot between activity and non-activity clusters. Consistent with studies of naturalistic events, these studies of laboratory events indicate that people cross-classify event memories simultaneously into multiple global organisations.

Three experiments demonstrated that situational information contributes to the categorization of functional object categories, as well as to inferences about these categories. When an object was presented in the context of setting and event information, categorization was more accurate than when the object was presented in isolation. Inferences about the object similarly became more accurate as the amount of situational information present during categorization increased. The benefits of situational information were higher when both setting and event information were available than when only setting information was available. These findings indicate that situational information about settings and events is stored with functional object categories in memory. Categorization and inference become increasingly accurate as the information available during categorization matches situational information stored with the category.

People construct ad hoc categories to achieve goals. For example, constructing the category of “things to sell at a garage sale” can be instrumental to achieving the goal of selling unwanted possessions. These categories differ from common categories (e.g., “fruit,” “furniture”) in that ad hoc categories violate the correlational structure of the environment and are not well established in memory. Regarding the latter property, the category concepts, concept-to-instance associations, and instance-to-concept associations structuring ad hoc categories are shown to be much less established in memory than those of common categories. Regardless of these differences, however, ad hoc categories possess graded structures (i.e., typicality gradients) as salient as those structuring common categories. This appears to be the result of a similarity comparison process that imposes graded structure on any category regardless of type.

Three experiments demonstrated that situational information contributes to the categorization of functional object categories, as well as to inferences about these categories. When an object was presented in the context of setting and event information, categorization was more accurate than when the object was presented in isolation. Inferences about the object similarly became more accurate as the amount of situational information present during categorization increased. The benefits of situational information were higher when both setting and event information were available than when only setting information was available. These findings indicate that situational information about settings and events is stored with functional object categories in memory. Categorization and inference become increasingly accurate as the information available during categorization matches situational information stored with the category.

In a recent neuroimaging study of macaque monkeys, Gil-da-Costa and colleagues reported that a distributed circuit of modality-specific properties represents macaques' conceptual knowledge of social situations. The circuit identified shows striking similarities to analogous circuits in humans that represent conceptual knowledge. This parallel suggests that a common architecture underlies the conceptual systems of different species, although with additional systems extending human conceptual abilities significantly.

Theories of knowledge such as feature lists, semantic networks, and localist neural nets typically use a single global symbol to represent a property that occurs in multiple concepts. Thus, a global symbol represents mane across HORSE, PONY, and LION. Alternatively, perceptual theories of knowledge, as well as distributed representational systems, assume that properties take different local forms in different concepts. Thus, different local forms of mane exist for HORSE, PONY, and LION, each capturing the specific form that mane takes in its respective concept. Three experiments used the property verification task to assess whether properties are represented globally or locally (e.g., Does a PONY have mane?). If a single global form represents a property, then verifying it in any concept should increase its accessibility and speed its verification later in any other concept. Verifying mane for PONY should benefit as much from having verified mane for LION earlier as from verifying mane for HORSE. If properties are represented locally, however, verifying a property should only benefit from verifying a similar form earlier. Verifying mane for PONY should only benefit from verifying mane for HORSE, not from verifying mane for LION. Findings from three experiments strongly supported local property representation and ruled out the interpretation that object similarity was responsible (e.g., the greater overall similarity between HORSE and PONY than between LION and PONY). The findings further suggest that property representation and verification are complicated phenomena, grounded in sensory-motor simulations.

Previous research has shown that na_ve participants display a high level of agreement when asked to choose or drawschematic representations, or image schemas, of concrete and abstract verbs [Proceedings of the 23rd Annual Meeting of the Cognitive Science Society, 2001, Erlbaum, Mawhah, NJ, p. 873]. For example, participants tended to ascribe a horizontal image schema to push, and a vertical image schema to respect. This consistency in offline data is preliminary evidence that language invokes spatial forms of representation. It also provided norms that were used in the present research to investigate the activation of spatial image schemas during online language comprehension. We predicted that if comprehending a verb activates a spatial representation that is extended along a particular horizontal or vertical axis, it will affect other forms of spatial processing along that axis. Participants listened to short sentences while engaged in a visual discrimination task (Experiment 1) and a picture memory task (Experiment 2). In both cases, reaction times showed an interaction between the horizontal/vertical nature of the verb's image schema, and the horizontal/vertical position of the visual stimuli. We argue that such spatial effects of verb comprehension provide evidence for the perceptual–motor character of linguistic representations.

According to the perceptual symbols theory (Barsalou, 1999), sensorimotor simulations underlie the representation of concepts. Simulations are componential in the sense that they vary with the context in which the concept is presented. In the present study, we investigated whether representations are affected by recent experiences with a concept. Concept names (e.g., APPLE) were presented twice in a property verification task with a different property on each occasion. The two properties were either from the same perceptual modality (e.g.,green, shiny) or from different modalities (e.g.,tart, shiny). All stimuli were words. There was a lag of several intervening trials between the first and second presentation. Verification times and error rates for the second presentation of the concept were higher if the properties were from different modalities than if they were from the same modality.

Many objects typically occur in particular locations, and object words encode these spatial associations. We tested whether such object words (e.g., head, foot) orient attention toward the location where the denoted object typically occurs (i.e., up, down). Because object words elicit perceptual simulations of the denoted objects (i.e., the representations acquired during actual perception are reactivated), we predicted that an object word would interfere with identification of an unrelated visual target subsequently presented in the object's typical location. Consistent with this prediction, three experiments demonstrated that words denoting objects that typically occur high in the visual field hindered identification of targets appearing at the top of the display, whereas words denoting low objects hindered target identification at the bottom of the display. Thus, object words oriented attention to and activated perceptual simulations in the objects' typical locations. These results shed new light on how language affects perception.

The LASS theory proposes that Language and Situated Simulation both play central roles in conceptual processing. Depending on stimuli and task conditions, different mixtures of language and simulation occur. When a word is processed in a conceptual task, it first activates other linguistic forms, such as word associates. More slowly, the word activates a situated simulation to represent its meaning in neural systems for perception, action, and mental states. An fMRI experiment tested the LASS account. In a first scanning session, participants performed the property generation task to provide a measure of conceptual processing. In a second scanning session a week later, participants performed two localizer tasks measuring word association and situated simulation. Conjunction analyses supported predictions of the LASS theory. Activations early in conceptual processing overlapped with activations for word association. Activations late in conceptual processing overlapped with activations for situation generation. These results, along with others in the literature, indicate that conceptual processing uses multiple representations, not one. Furthermore, researchers must be careful drawing conclusions about conceptual processing, given that different paradigms are likely to produce different mixtures of language and simulation. Whereas some paradigms produce high levels of linguistic processing and low levels of simulation, other paradigms produce the opposite pattern.

Work in philosophy and psychology has argued for a dissociation between perceptually-based similarity and higher-level rules in conceptual thought. Although such a dissociation may be justified at times, our goal is to illustrate ways in which conceptual processing is grounded in perception, both for perceptual similarity and abstract rules. We discuss the advantages, power and influences of perceptually-based representations. First, many of the properties associated with amodal symbol systems can be achieved with perceptually-based systems as well (e.g. productivity). Second, relatively raw perceptual representations are powerful because they can implicitly represent properties in an analog fashion. Third, perception naturally provides impressions of overall similarity, exactly the type of similarity useful for establishing many common categories. Fourth, perceptual similarity is not static but becomes tuned over time to conceptual demands. Fifth, the original motivation or basis for sophisticated cognition is often less sophisticated perceptual similarity. Sixth, perceptual simulation occurs even in conceptual tasks that have no explicit perceptual demands. Parallels between perceptual and conceptual processes suggest that many mechanisms typically associated with abstract thought are also present in perception, and that perceptual processes provide useful mechanisms that may be co-opted by abstract thought.

After reviewing six senses of abstraction, this article focuses on abstractions that take the form of summary representations. Three central properties of these abstractions are established: ( i ) type-token interpretation; (ii) structured representation; and (iii) dynamic realization. Traditional theories of representation handle interpretation and structure well but are not sufficiently dynamical. Conversely, connectionist theories are exquisitely dynamic but have problems with structure. Perceptual symbol systems offer an approach that implements all three properties naturally. Within this framework, a loose collection of property and relation simulators develops to represent abstractions. Type-token interpretation results from binding a property simulator to a region of a perceived or simulated category member. Structured representation results from binding a configuration of property and relation simulators to multiple regions in an integrated manner. Dynamic realization results from applying different subsets of property and relation simulators to category members on different occasions. From this standpoint, there are no permanent or complete abstractions of a category in memory. Instead, abstraction is the skill to construct temporary online interpretations of a category's members. Although an infinite number of abstractions are possible, attractors develop for habitual approaches to interpretation. This approach provides new ways of thinking about abstraction phenomena in categorization, inference, background knowledge and learning.

The conceptual system contains categorical knowledge about experience that supports the spectrum of cognitive processes. Cognitive science theories assume that categorical knowledge resides in a modular and amodal semantic memory, whereas neuroscience theories assume that categorical knowledge is grounded in the brain's modal systems for perception, action, and affect. Neuroscience has influenced theories of the conceptual system by stressing principles of neural processing in neural networks and by motivating grounded theories of cognition, which propose that simulations of experience represent knowledge. Cognitive science has influenced theories of the conceptual system by documenting conceptual phenomena and symbolic operations that must be grounded in the brain. Significant progress in understanding the conceptual system is most likely to occur if cognitive and neural approaches achieve successful integration.