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Language and Arithmetic
(2018)
We examined cross-domain semantic priming effects between arithmetic and language. We paired subtractions with their linguistic equivalent, exception phrases (EPs) with positive quantifiers (e.g., “everybody except John”) while pairing additions with their own linguistic equivalent, EPs with negative quantifiers (e.g., “nobody except John”; Moltmann, 1995). We hypothesized that EPs with positive quantifiers prime subtractions and inhibit additions while EPs with negative quantifiers prime additions and inhibit subtractions. Furthermore, we expected similar priming and inhibition effects from arithmetic into semantics. Our design allowed for a bidirectional analysis by using one trial's target as the prime for the next trial. Two experiments failed to show significant priming effects in either direction. Implications and possible shortcomings are explored in the general discussion.
Language and Arithmetic
(2018)
We examined cross-domain semantic priming effects between arithmetic and language. We paired subtractions with their linguistic equivalent, exception phrases (EPs) with positive quantifiers (e.g., “everybody except John”) while pairing additions with their own linguistic equivalent, EPs with negative quantifiers (e.g., “nobody except John”; Moltmann, 1995). We hypothesized that EPs with positive quantifiers prime subtractions and inhibit additions while EPs with negative quantifiers prime additions and inhibit subtractions. Furthermore, we expected similar priming and inhibition effects from arithmetic into semantics. Our design allowed for a bidirectional analysis by using one trial's target as the prime for the next trial. Two experiments failed to show significant priming effects in either direction. Implications and possible shortcomings are explored in the general discussion.
Conceptual knowledge about objects, people and events in the world is central to human cognition, underlying core cognitive abilities such as object recognition and use, and word comprehension. Previous research indicates that concepts consist of perceptual and motor features represented in modality-specific perceptual-motor brain regions. In addition, cross-modal convergence zones integrate modality-specific features into more abstract conceptual representations.
However, several questions remain open: First, to what extent does the retrieval of perceptual-motor features depend on the concurrent task? Second, how do modality-specific and cross-modal regions interact during conceptual knowledge retrieval? Third, which brain regions are causally relevant for conceptually-guided behavior? This thesis addresses these three key issues using functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) in the healthy human brain.
Study 1 - an fMRI activation study - tested to what extent the retrieval of sound and action features of concepts, and the resulting engagement of auditory and somatomotor brain regions depend on the concurrent task. 40 healthy human participants performed three different tasks - lexical decision, sound judgment, and action judgment - on words with a high or low association to sounds and actions. We found that modality-specific regions selectively respond to task-relevant features: Auditory regions selectively responded to sound features during sound judgments, and somatomotor regions selectively responded to action features during action judgments. Unexpectedly, several regions (e.g. the left posterior parietal cortex; PPC) exhibited a task-dependent response to both sound and action features. We propose these regions to be "multimodal", and not "amodal", convergence zones which retain modality-specific information.
Study 2 - an fMRI connectivity study - investigated the functional interaction between modality-specific and multimodal areas during conceptual knowledge retrieval. Using the above fMRI data, we asked (1) whether modality-specific and multimodal regions are functionally coupled during sound and action feature retrieval, (2) whether their coupling depends on the task, (3) whether information flows bottom-up, top-down, or bidirectionally, and (4) whether their coupling is behaviorally relevant. We found that functional coupling between multimodal and modality-specific areas is task-dependent, bidirectional, and relevant for conceptually-guided behavior. Left PPC acted as a connectivity "switchboard" that flexibly adapted its coupling to task-relevant modality-specific nodes.
Hence, neuroimaging studies 1 and 2 suggested a key role of left PPC as a multimodal convergence zone for conceptual knowledge. However, as neuroimaging is correlational, it remained unknown whether left PPC plays a causal role as a multimodal conceptual hub. Therefore, study 3 - a TMS study - tested the causal relevance of left PPC for sound and action feature retrieval. We found that TMS over left PPC selectively impaired action judgments on low sound-low action words, as compared to sham stimulation. Computational simulations of the TMS-induced electrical field revealed that stronger stimulation of left PPC was associated with worse performance on action, but not sound, judgments. These results indicate that left PPC causally supports conceptual processing when action knowledge is task-relevant and cannot be compensated by sound knowledge. Our findings suggest that left PPC is specialized for action knowledge, challenging the view of left PPC as a multimodal conceptual hub.
Overall, our studies support "hybrid theories" which posit that conceptual processing involves both modality-specific perceptual-motor regions and cross-modal convergence zones. In our new model of the conceptual system, we propose conceptual processing to rely on a representational hierarchy from modality-specific to multimodal up to amodal brain regions. Crucially, this hierarchical system is flexible, with different regions and connections being engaged in a task-dependent fashion. Our model not only reconciles the seemingly opposing grounded cognition and amodal theories, it also incorporates task dependency of conceptually-related brain activity and connectivity, thereby resolving several current issues on the neural basis of conceptual knowledge retrieval.
Meaning-making in the brain has become one of the most intensely discussed topics in cognitive science. Traditional theories on cognition that emphasize abstract symbol manipulations often face a dead end: The symbol grounding problem. The embodiment idea tries to overcome this barrier by assuming that the mind is grounded in sensorimotor experiences. A recent surge in behavioral and brain-imaging studies has therefore focused on the role of the motor cortex in language processing. Concrete, action-related words have received convincing evidence to rely on sensorimotor activation. Abstract concepts, however, still pose a distinct challenge for embodied theories on cognition. Fully embodied abstraction mechanisms were formulated but sensorimotor activation alone seems unlikely to close the explanatory gap. In this respect, the idea of integration areas, such as convergence zones or the ‘hub and spoke’ model, do not only appear like the most promising candidates to account for the discrepancies between concrete and abstract concepts but could also help to unite the field of cognitive science again. The current review identifies milestones in cognitive science research and recent achievements that highlight fundamental challenges, key questions and directions for future research.
Meaning-making in the brain has become one of the most intensely discussed topics in cognitive science. Traditional theories on cognition that emphasize abstract symbol manipulations often face a dead end: The symbol grounding problem. The embodiment idea tries to overcome this barrier by assuming that the mind is grounded in sensorimotor experiences. A recent surge in behavioral and brain-imaging studies has therefore focused on the role of the motor cortex in language processing. Concrete, action-related words have received convincing evidence to rely on sensorimotor activation. Abstract concepts, however, still pose a distinct challenge for embodied theories on cognition. Fully embodied abstraction mechanisms were formulated but sensorimotor activation alone seems unlikely to close the explanatory gap. In this respect, the idea of integration areas, such as convergence zones or the ‘hub and spoke’ model, do not only appear like the most promising candidates to account for the discrepancies between concrete and abstract concepts but could also help to unite the field of cognitive science again. The current review identifies milestones in cognitive science research and recent achievements that highlight fundamental challenges, key questions and directions for future research.