W. Kyle Simmons

Grounding conceptual knowledge in modality-specific systems.

The human conceptual system contains knowledge that supports all cognitive activities, including perception, memory, language and thought. According to most current theories, states in modality-specific systems for perception, action and emotion do not represent knowledge - rather, redescriptions of these states in amodal representational languages do. Increasingly, however, researchers report that re-enactments of states in modality-specific systems underlie conceptual processing. In behavioral experiments, perceptual and motor variables consistently produce effects in conceptual tasks. In brain imaging experiments, conceptual processing consistently activates modality-specific brain areas. Theoretical research shows how modality-specific re-enactments could produce basic conceptual functions, such as the type-token distinction, categorical inference, productivity, propositions and abstract concepts. Together these empirical results and theoretical analyses implicate modality-specific systems in the representation and use of conceptual knowledge.

THE SIMILARITY-IN-TOPOGRAPHY PRINCIPLE: RECONCILING THEORIES OF CONCEPTUAL DEFICITS

Three theories currently compete to explain the conceptual deficits that result from brain damage: sensory-functional theory, domain-specific theory, and conceptual structure theory. We argue that all three theories capture important aspects of conceptual deficits, and offer different insights into their origins. Conceptual topography theory (CTT) integrates these insights, beginning with A. R. Damasios (1989) convergence zone theory and elaborating it with the similarity-in-topography (SIT) principle. According to CTT, feature maps in sensory-motor systems represent the features of a categorys exemplars. A hierarchical system of convergence zones then conjoins these features to form both property and category representations. According to the SIT principle, the proximity of two conjunctive neurons in a convergence zone increases with the similarity of the features they conjoin. As a result, conjunctive neurons become topographically organised into local regions that represent properties and categories. Depending on the level and location of a lesion in this system, a wide variety of deficits is possible. Consistent with the literature, these deficits range from the loss of a single category to the loss of multiple categories that share sensory-motor properties.

Interoceptive predictions in the brain

Intuition suggests that perception follows sensation and therefore bodily feelings originate in the body. However, recent evidence goes against this logic: interoceptive experience may largely reflect limbic predictions about the expected state of the body that are constrained by ascending visceral sensations. In this Opinion article, we introduce the Embodied Predictive Interoception Coding model, which integrates an anatomical model of corticocortical connections with Bayesian active inference principles, to propose that agranular visceromotor cortices contribute to interoception by issuing interoceptive predictions. We then discuss how disruptions in interoceptive predictions could function as a common vulnerability for mental and physical illness.

A common neural substrate for perceiving and knowing about color.

Functional neuroimaging research has demonstrated that retrieving information about object-associated colors activates the left fusiform gyrus in posterior temporal cortex. Although regions near the fusiform have previously been implicated in color perception, it remains unclear whether color knowledge retrieval actually activates the color perception system. Evidence to this effect would be particularly strong if color perception cortex was activated by color knowledge retrieval triggered strictly with linguistic stimuli. To address this question, subjects performed two tasks while undergoing fMRI. First, subjects performed a property verification task using only words to assess conceptual knowledge. On each trial, subjects verified whether a named color or motor property was true of a named object (e.g., TAXI-yellow, HAIR-combed). Next, subjects performed a color perception task. A region of the left fusiform gyrus that was highly responsive during color perception also showed greater activity for retrieving color than motor property knowledge. These data provide the first evidence for a direct overlap in the neural bases of color perception and stored information about object-associated color, and they significantly add to accumulating evidence that conceptual knowledge is grounded in the brains modality-specific systems.

Fractionation of social brain circuits in autism spectrum disorders

Autism spectrum disorders are developmental disorders characterized by impairments in social and communication abilities and repetitive behaviours. Converging neuroscientific evidence has suggested that the neuropathology of autism spectrum disorders is widely distributed, involving impaired connectivity throughout the brain. Here, we evaluate the hypothesis that decreased connectivity in high-functioning adolescents with an autism spectrum disorder relative to typically developing adolescents is concentrated within domain-specific circuits that are specialized for social processing. Using a novel whole-brain connectivity approach in functional magnetic resonance imaging, we found that not only are decreases in connectivity most pronounced between regions of the social brain but also they are selective to connections between limbic-related brain regions involved in affective aspects of social processing from other parts of the social brain that support language and sensorimotor processes. This selective pattern was independently obtained for correlations with measures of social symptom severity, implying a fractionation of the social brain in autism spectrum disorders at the level of whole circuits.

Grounding Emotion in Situated Conceptualization

According to the Conceptual Act Theory of Emotion, the situated conceptualization used to construe a situation determines the emotion experienced. A neuroimaging experiment tested two core hypotheses of this theory: (1) different situated conceptualizations produce different forms of the same emotion in different situations, (2) the composition of a situated conceptualization emerges from shared multimodal circuitry distributed across the brain that produces emotional states generally. To test these hypotheses, the situation in which participants experienced an emotion was manipulated. On each trial, participants immersed themselves in a physical danger or social evaluation situation and then experienced fear or anger. According to Hypothesis 1, the brain activations for the same emotion should differ as a function of the preceding situation (after removing activations that arose while constructing the situation). According to Hypothesis 2, the critical activations should reflect conceptual processing relevant to the emotion in the current situation, drawn from shared multimodal circuitry underlying emotion. The results supported these predictions and demonstrated the compositional process that produces situated conceptualizations dynamically.

The Selectivity and Functional Connectivity of the Anterior Temporal Lobes

One influential account asserts that the anterior temporal lobe (ATL) is a domain-general hub for semantic memory. Other evidence indicates it is part of a domain-specific social cognition system. Arbitrating these accounts using functional magnetic resonance imaging has previously been difficult because of magnetic susceptibility artifacts in the region. The present study used parameters optimized for imaging the ATL, and had subjects encode facts about unfamiliar people, buildings, and hammers. Using both conjunction and region of interest analyses, person-selective responses were observed in both the left and right ATL. Neither building-selective, hammer-selective nor domain-general responses were observed in the ATLs, although they were observed in other brain regions. These findings were supported by “resting-state” functional connectivity analyses using independent datasets from the same subjects. Person-selective ATL clusters were functionally connected with the brains wider social cognition network. Rather than serving as a domain-general semantic hub, the ATLs work in unison with the social cognition system to support learning facts about others.

Self-Regulation of Amygdala Activation Using Real-Time fMRI Neurofeedback

Real-time functional magnetic resonance imaging (rtfMRI) with neurofeedback allows investigation of human brain neuroplastic changes that arise as subjects learn to modulate neurophysiological function using real-time feedback regarding their own hemodynamic responses to stimuli. We investigated the feasibility of training healthy humans to self-regulate the hemodynamic activity of the amygdala, which plays major roles in emotional processing. Participants in the experimental group were provided with ongoing information about the blood oxygen level dependent (BOLD) activity in the left amygdala (LA) and were instructed to raise the BOLD rtfMRI signal by contemplating positive autobiographical memories. A control group was assigned the same task but was instead provided with sham feedback from the left horizontal segment of the intraparietal sulcus (HIPS) region. In the LA, we found a significant BOLD signal increase due to rtfMRI neurofeedback training in the experimental group versus the control group. This effect persisted during the Transfer run without neurofeedback. For the individual subjects in the experimental group the training effect on the LA BOLD activity correlated inversely with scores on the Difficulty Identifying Feelings subscale of the Toronto Alexithymia Scale. The whole brain data analysis revealed significant differences for Happy Memories versus Rest condition between the experimental and control groups. Functional connectivity analysis of the amygdala network revealed significant widespread correlations in a fronto-temporo-limbic network. Additionally, we identified six regions — right medial frontal polar cortex, bilateral dorsomedial prefrontal cortex, left anterior cingulate cortex, and bilateral superior frontal gyrus — where the functional connectivity with the LA increased significantly across the rtfMRI neurofeedback runs and the Transfer run. The findings demonstrate that healthy subjects can learn to regulate their amygdala activation using rtfMRI neurofeedback, suggesting possible applications of rtfMRI neurofeedback training in the treatment of patients with neuropsychiatric disorders.

Keeping the body in mind: Insula functional organization and functional connectivity integrate interoceptive, exteroceptive, and emotional awareness

Relatively discrete experimental literatures have grown to support the insulas role in the domains of interoception, focal exteroceptive attention and cognitive control, and the experience of anxiety, even as theoretical accounts have asserted that the insula is a critical zone for integrating across these domains. Here we provide the first experimental demonstration that there exists a functional topography across the insula, with distinct regions in the same participants responding in a highly selective fashion for interoceptive, exteroceptive, and affective processing. Although each insular region is associated with areas of differential resting state functional connectivity relative to the other regions, overall their functional connectivity profiles are quite similar, thereby providing a map of how interoceptive, exteroceptive, and emotional awareness are integrated within the insular cortex. Hum Brain Mapp 34:2944–2958, 2013.

fMRI evidence for word association and situated simulation in conceptual processing

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.