Representation of Grammatical Categories of Words in the Brain

We report the performance of a patient who, as a consequence of left frontal and temporoparietal strokes, makes far more errors on nouns than on verbs in spoken output tasks, but makes far more errors on verbs than on nouns in written input tasks. This double dissociation within a single patient with respect to grammatical category provides evidence for the hypothesis that phonological and orthographic representations of nouns and verbs are processed by independent neural mechanisms. Furthermore, the opposite dissociation in the verbal output modality, an advantage for nouns over verbs in spoken tasks, by a different patient using the same stimuli has also been reported (Caramazza & Hillis, 1991). This double dissociation across patients on the same task indicates that results cannot be ascribed to "greater difficulty" with one type of stimulus, and provides further evidence for the view that grammatical category information is an important organizational principle of lexical knowledge in the brain.Psycholog

Linking somatic and symbolic representation in semantic memory: the dynamic multilevel reactivation framework

Biological plausibility is an essential constraint for any viable model of semantic memory. Yet, we have only the most rudimentary understanding of how the human brain conducts abstract symbolic transformations that underlie word and object meaning. Neuroscience has evolved a sophisticated arsenal of techniques for elucidating the architecture of conceptual representation. Nevertheless, theoretical convergence remains elusive. Here we describe several contrastive approaches to the organization of semantic knowledge, and in turn we offer our own perspective on two recurring questions in semantic memory research: (1) to what extent are conceptual representations mediated by sensorimotor knowledge (i.e., to what degree is semantic memory embodied)? (2) How might an embodied semantic system represent abstract concepts such as modularity, symbol, or proposition? To address these questions, we review the merits of sensorimotor (i.e., embodied) and amodal (i.e., disembodied) semantic theories and address the neurobiological constraints underlying each. We conclude that the shortcomings of both perspectives in their extreme forms necessitate a hybrid middle ground. We accordingly propose the Dynamic Multilevel Reactivation Framework—an integrative model predicated upon flexible interplay between sensorimotor and amodal symbolic representations mediated by multiple cortical hubs. We discuss applications of the dynamic multilevel reactivation framework to abstract and concrete concept representation and describe how a multidimensional conceptual topography based on emotion, sensation, and magnitude can successfully frame a semantic space containing meanings for both abstract and concrete words. The consideration of ‘abstract conceptual features’ does not diminish the role of logical and/or executive processing in activating, manipulating and using information stored in conceptual representations. Rather, it proposes that the materials upon which these processes operate necessarily combine pure sensorimotor information and higher-order cognitive dimensions involved in symbolic representation

Functional MRI language mapping in pre-surgical epilepsy patients: Findings from a series of patients in the Epilepsy Unit at Mediclinic Constantiaberg

Background. Functional magnetic resonance imaging (fMRI) is commonly applied to study the neural substrates of language in clinical research and for neurosurgical planning. fMRI language mapping is used to assess language lateralisation, or determine hemispheric dominance, and to localise regions of the brain involved in language. Routine fMRI has been introduced in the Epilepsy Unit at Mediclinic Constantiaberg to contribute to the current functional mapping procedures used in pre-surgical planning.Method. In this paper we describe the language paradigms used in these routine studies as well as the results from 22 consecutive epilepsy patients. Multi-subject analyses were performed to assess the reliability of activation patterns generated by two language mapping paradigms, namely a verb generation task and passive listening task. Results from a finger-tapping task are also presented.Results. The paradigms generate reliable and robust signal changes, enabling both the lateralisation of language and localisation of expressive and receptive language cortex.Conclusion. The fMRI results are meaningful at the group and individual level and can be recommended for language mapping in pre-surgical patients.

Conceptual semantics as grounded in personal experience

Semantic memory for an object encompasses multi-modal knowledge gained through personal experience over the lifetime, and coded in grounded sensory-motor brain systems, independently of the level of subjective awareness. Linguistic access to semantic memories in verbal format relies on the functional coupling between perisylvian language regions and the grounded brain systems implied by our lifetime experience with the concept’s referents. Linguistic structure exerts modulatory influences on this functional coupling, as in the case of sentential negation, which reduces the interactions between perisylvian language regions and the grounded brain systems

An analysis of current evidence supporting two alternate learning models: Learning styles and dual coding.

This paper examines the research evidence behind two alternate and mutually exclusive learning models- learning styles and dual coding. The most common incarnation of each model is based on learning modalities, and each makes predictions about how learners process auditory and visual stimuli. Learning styles have found wide acceptance in public perception and throughout education at all levels, yet the majority of empirical research suggests that the model is not accurate and that learning styles instruction has no effect on student learning. Dual coding is more strongly supported by empirical research yet less well known and less commonly used in practice. The analysis examines evidence from a wide variety of sources, including experimental studies, correlational research, teacher-education texts, and neuroimaging studies. The findings reveal that dual coding is likely to be the more accurate model and that it offers more potential for both research and in practical application

Brain correlates of action word memory revealed by fMRI

Understanding language semantically related to actions activates the motor cortex. This activation is sensitive to semantic information such as the body part used to perform the action (e.g. arm-/leg-related action words). Additionally, motor movements of the hands/feet can have a causal effect on memory maintenance of action words, suggesting that the involvement of motor systems extends to working memory. This study examined brain correlates of verbal memory load for action-related words using event-related fMRI. Seventeen participants saw either four identical or four different words from the same category (arm-/leg-related action words) then performed a nonmatching-to-sample task. Results show that verbal memory maintenance in the high-load condition produced greater activation in left premotor and supplementary motor cortex, along with posterior-parietal areas, indicating that verbal memory circuits for action-related words include the cortical action system. Somatotopic memory load effects of arm- and leg-related words were observed, but only at more anterior cortical regions than was found in earlier studies employing passive reading tasks. These findings support a neurocomputational model of distributed action-perception circuits (APCs), according to which language understanding is manifest as full ignition of APCs, whereas working memory is realized as reverberant activity receding to multimodal prefrontal and lateral temporal areas

Die Verarbeitung von Eigennamen im Mandarin-Chinesischen : eine Verhaltens- und Neuroimaging-Studie

Yen H-L. Processing of proper names in Mandarin Chinese : a behavioral and neuroimaging study. Bielefeld (Germany): Bielefeld University; 2006.Proper names have been considered as a universal language class (Bright, 2003; Müller 2004). The distinction between proper names and common nouns has been postulated since several thousand years in ancient Greek and in Chinese philosophy of language (e.g., Kripke, 1972; Wu, 1997). Furthermore, this dissociation has been supported by experimental data (e.g., Müller & Kutas, 1996) and case studies (e.g., Lyons, 2002). This dissertation explores the processing of proper names in Mandarin Chinese in which the morphology of proper names and the tradition of name giving differ greatly from Indo-European languages such as German and English. It aims to figure out whether the theoretically based dissociation has a neurocognitive reality. Besides a behavior study (category decision task), we carried out an auditory and a visual functional magnetic resonance imaging (fMRI) experiment. Forty native speakers of Mandarin Chinese took part in the behavior study whereas twelve different participants participated the fMRI study. For both modalities, forty personal names, forty geographical names and forty common nouns were used as experimental stimuli. Different words were applied in the auditory and the visual experiment. The behavior study tested 20 brand names in addition. In general, Mandarin Chinese speakers of the present study were able to recognize proper names as type (here: personal names and geographical names) significantly faster than common nouns in both auditory and visual modality. In contrast, brand names did not exhibit the faster reaction time than common nouns. The reaction time of brand names was significantly longer than personal names and geographical names. In our fMRI study, processing of proper names and processing of common nouns revealed partially different brain activation patterns. Contrasts between personal names and common nouns as well as contrasts between geographical names and common nouns revealed significant activation. In auditory modality, proper names revealed more activation in bilateral anterior temporal cortices, premotor area and anterior precuneus. In visual modality, proper names evoked significant activation in the frontal lobe including frontal eye fields and premotor area. Despite of modality, common nouns yielded significant activation in the left posterior temporal cortex. Further characteristic of processing of common nouns was activation in occipital area and temporo-parietal junction. Our fMRI findings support the view that processing of proper names and common nouns involve different brain areas. This may due to the difference between general semantic processing and identity-specific semantic processing. Moreover, the corresponding cognitive mechanism of proper name processing may differ from common nouns. The present finding in Mandarin Chinese is also supported by previous research of Indo-European languages. Corresponding to the hypothesis which has been discussed in the philosophy of language over two thousand years, the special status of proper names can be supported by our neurocognitive evidence

The anatomical substrates of feature integration during object processing.

Objects can be identified from a number of perceptual attributes, including visual, auditory and tactile sensory input. The integration of these perceptual attributes constitutes our semantic knowledge of an object representation. This research uses functional neuroimaging to investigate the brain areas that integrate perceptual features into an object representation, and how these regions are modulated by stimulus- and task-specific features. A series of experiments are reported that utilise different types of perceptual integration, both within and across sensory modalities. These include 1) the integration of visual form with colour, 2) the integration of visual and auditory object features, and 3) the integration of visual and tactile abstract shapes. Across these experiments I have also manipulated additional factors, including the meaning of the perceptual information (meaningful objects versus meaningless shapes), the verbal or non-verbal nature of the perceptual inputs (e.g. spoken words versus environmental sounds) and the congruency of crossmodal inputs. These experiments have identified a network of brain regions both common to, and selective for, different types of object feature integration. For instance, I have identified a common bilateral network involved in the integration and association of crossmodal audiovisual objects and intra-modal auditory or visual object pairs. However, I have also determined that activation in response to the same concepts can be modulated by the type of stimulus input (verbal versus nonverbal), the timing of those inputs (simultaneous versus sequential presentation), and the congruency of stimulus pairs (congruent versus incongruent). Taken together, the results from these experiments demonstrate modulations of neuronal activation by different object attributes at multiple different levels of the object processing hierarchy, from early sensory processing through to stored object representations. Critically, these differential effects have even been observed with the same conceptual stimuli. Together these findings highlight the need for a model of object feature processing that can account for the functional demands that elicit these anatomical differences

A Neurobiologically Constrained Model

Understanding the meaning of words and its relationship with the outside world involves higher cognitive processes unique of the human brain. Despite many decades of research on the neural substrates of semantic processing, a consensus about the functions and components of the semantic system has not been reached among cognitive neuroscientists. This issue is mainly influenced by two sets of neurocognitive empirical findings that have shown (i) the existence of several regions acting as ’semantic hubs’, where the meaning of all types of words is processed and (ii) the presence of other cortical regions specialised for the processing of specific semantic word categories, such as animals, tools, or actions. Further evidence on semantic meaning processing comes from neuroimaging and transcranial magnetic stimulation studies in visually deprived population that acquires semantic knowledge through non-sensory modalities. These studies have documented massive neural changes in the visual system that is in turn recruited for linguistic and semantic processing. On this basis, this dissertation investigates the neurobiological mechanism that enables humans to acquire, store and processes linguistics meaning by means of a neurobiologically constrained neural network and offers an answer to the following hotly debated questions: Why both semantic hubs and modality-specific regions are involved in semantic meaning processing in the brain? Which biological principles are critical for the emergence of semantics at the microstructural neural level and how is the semantic system implemented under deprived conditions, in particular in congenitally blind people? First, a neural network model closely replicating the anatomical and physiological features of the human cortex was designed. At the micro level, the network was composed of 15,000 artificial neurons; at the large-scale level, there were 12 areas representing the frontal, temporal, and occipital lobes relevant for linguistic and semantic processing. The connectivity structure linking the different cortical areas was purely based on neuroanatomical evidence. Two models were used, each simulating the same set of cortical regions but at different level of details: one adopted a simple connectivity structure with a mean-field approach (i.e. graded-response neurons), and the other used a fully connected model with adaptation-based spiking cells. Second, the networks were used to simulate the process of learning semantic relationships between word-forms, specific object perceptions, and motor movements of the own body in deprived and undeprived visual condition. As a result of Hebbian correlated learning, distributed word-related cell assembly circuits spontaneously emerged across the different cortical semantic areas exhibiting different topographical distribution. Third, the network was reactivated with the learned auditory patterns (simulating word recognition processes) to investigate the temporal dynamics of cortical semantic activation and compare them with real brain responses. In summary, the findings of the present work demonstrate that meaningful linguistic units are represented in the brain in the form of cell assemblies that are distributed over both semantic hubs and category-specific regions spontaneously emerged through the mutual interaction of a single set of biological mechanisms acting within specific neuroanatomical structures. These biological principles acting together also offer an explanation of the mechanisms underlying massive neural changes in the visual cortex for language processing caused by blindness. The present work is a first step in better understanding the building blocks of language and semantic processing in sighted and blind populations by translating biological principles that govern human cognition into precise mathematical neural networks of the human brain.Um die Bedeutung von Wörtern und ihre Beziehung zur Außenwelt zu verstehen, müssen die kognitiven Prozesse betrachtet werden, die einzigartig für das menschliche Gehirn sind. Trotz jahrzehntelanger Forschungen an den neuronalen Substraten der semantischen Verarbeitung im menschlichen Gehirn wurde bisher kein Konsens über die Funktionen und Komponenten des semantischen Systems in den kognitiven Neurowissenschaftlern erreicht. Dieses Problem gründet darin, dass neurokognitive empirische Studien zumeist zu zwei Endergebnissen kamen: (i) der Existenz von mehrere Regionen, die als ‘semantische Hubs’ fungieren, in denen die Bedeutung aller Wortarten verarbeitet wird, und (ii) dem Vorhandensein weiterer kortikaler Regionen, die auf die Verarbeitung spezifischer semantischer Kategorien wie Tiere, Werkzeuge oder Aktionswörtern spezialisiert sind. Ein weiterer Beweis für die Verarbeitung semantischer Bedeutungen lässt sich aus Bildgebungsstudien und Studien mit transkranialer Magnetstimulation an visuell benachteiligten Probanden entnehmen, die die linguistische Bedeutung nicht durch sensorische Modalitäten erwerben. Diese Studien konnten massive neuronale Veränderungen im visuellen System dokumentieren, die wiederum für die sprachliche und semantische Verarbeitung verwendet werden. Die vorliegende Dissertation untersucht mittels eines biologischen neuronalen Netzwerkes jene kognitiven Prozesse, die es Menschen ermöglichen, linguistische Bedeutungen in der täglichen Kommunikation zu erfassen, zu speichern und zu verarbeiten. Sie schlägt Antworten auf die folgenden neurowissenschaftlich heiß diskutierten Fragen vor: Warum sind sowohl semantische Hubs als auch modalitätsspezifische Regionen relevant für die sprachliche und semantische Informationsverarbeitung im Gehirn? Welche biologischen Prinzipien sind von entscheidender Bedeutung für die Entstehung von Semantik auf mikrostruktureller neuronaler Ebene? Und Wie ist das semantische System unter benachteiligten Bedingungen repräsentiert? Zunächst wurde ein neuronales Netzwerkmodell implementiert, das die anatomischen und physiologischen Merkmale des menschlichen Kortex präzise widerspiegelt. Auf der Mikroebene besteht das Netzwerkmodel aus 15.000 künstlichen Neuronen, auf der Großebene aus 12 Arealen der Frontal-, Temporal- und Okzipitallappen, die für die sprachliche und semantische Verarbeitung relevant sind. Die Verbindungsstruktur zwischen den verschiedenen kortikalen Arealen wurde rein auf Grundlage von neuroanatomischen Befunden implementiert. Zwei Modelle wurden verwendet, die jeweils die gleichen kortikalen Regionen simulierten, allerdings in verschiedenen Varianten: Das erste Modell ging von einer einfachen Konnektivitätsstruktur mit einem Mean-field Ansatz (graded-response neurons) aus, während das zweite einen vollständig verbundenen Aufbau mit adaptionsbasierten Spiking-Zellen (Aktionspotential) verwendete. Anschließend dienten die neuronalen Netzwerke dazu, den Lernprozess der semantischen Verlinkung zwischen Wortformen, bestimmten Objektwahrnehmungen und motorischen Bewegungen des eigenen Körpers zu simulieren, sowohl in gesundem als auch in benachteiligtem Sehzustand. Als Ergebnis des Hebbschen Korrelationslernens traten spontan verteilte Neuronenverbindungen (cell assemblies) in den verschiedenen kortikalen semantischen Bereichen auf, die unterschiedliche topografische Verteilungen zeigten. Zuletzt wurde das Netzwerkmodell mit den erlernten auditorischen Mustern reaktiviert (Worterkennungsprozesse), um die zeitliche Dynamik kortikaler semantischer Aktivierung zu untersuchen und sie mit realen Gehirnantworten zu vergleichen. Die vorliegende Arbeit kam zu folgenden Ergebnissen: Die neuronale Repräsentation linguistischer Bedeutung wird im Gehirn in Form von cell assemblies dargestellt, welche über semantische Hubs und modalitätsspezifische Regionen verteilt sind. Diese entstehen spontan durch die Interaktion einer Reihe von biologischen Mechanismen, die innerhalb spezifischer neuroanatomischer Strukturen wirken. Das Zusammenwirken dieser biologischen Prinzipien bietet zusätzlich eine Erklärung für jene Faktoren, die für die massiven neuronalen Veränderungen in der sprachlichen und semantischen Netzwerke bei Blindheit verantwortlich sind. Die in dieser Dissertation dokumentierten Studien sind ein erster Schritt in Richtung eines besseren Verständnisses der sprachlichen und semantischen Informationsverarbeitung bei sehenden und blinden Menschen, basierend auf einer Übersetzung der biologischen Prinzipien der menschlichen Kognition in präzise mathematische neuronale Netzwerke des menschlichen Gehirns

Brain Signatures of Embodied Semantics and Language: A Consensus Paper

According to embodied theories (including embodied, embedded, extended, enacted, situated, and grounded approaches to cognition), language representation is intrinsically linked to our interactions with the world around us, which is reflected in specific brain signatures during language processing and learning. Moving on from the original rivalry of embodied vs. amodal theories, this consensus paper addresses a series of carefully selected questions that aim at determining when and how rather than whether motor and perceptual processes are involved in language processes. We cover a wide range of research areas, from the neurophysiological signatures of embodied semantics, e.g., event-related potentials and fields as well as neural oscillations, to semantic processing and semantic priming effects on concrete and abstract words, to first and second language learning and, finally, the use of virtual reality for examining embodied semantics. Our common aim is to better understand the role of motor and perceptual processes in language representation as indexed by language comprehension and learning. We come to the consensus that, based on seminal research conducted in the field, future directions now call for enhancing the external validity of findings by acknowledging the multimodality, multidimensionality, flexibility and idiosyncrasy of embodied and situated language and semantic processes