Giovanna Marotta

How concepts are encoded in the human brain: A modality independent, category-based cortical organization of semantic knowledge

How conceptual knowledge is represented in the human brain remains to be determined. To address the differential role of low-level sensory-based and high-level abstract features in semantic processing, we combined behavioral studies of linguistic production and brain activity measures by functional magnetic resonance imaging in sighted and congenitally blind individuals while they performed a property-generation task with concrete nouns from eight categories, presented through visual and/or auditory modalities. Patterns of neural activity within a large semantic cortical network that comprised parahippocampal, lateral occipital, temporo-parieto-occipital and inferior parietal cortices correlated with linguistic production and were independent both from the modality of stimulus presentation (either visual or auditory) and the (lack of) visual experience. In contrast, selected modality-dependent differences were observed only when the analysis was limited to the individual regions within the semantic cortical network. We conclude that conceptual knowledge in the human brain relies on a distributed, modality-independent cortical representation that integrates the partial category and modality specific information retained at a regional level.

BLIND: a set of semantic feature norms from the congenitally blind.

Feature-based descriptions of concepts produced by subjects in a property generation task are widely used in cognitive science to develop empirically grounded concept representations and to study systematic trends in such representations. This article introduces BLIND, a collection of parallel semantic norms collected from a group of congenitally blind Italian subjects and comparable sighted subjects. The BLIND norms comprise descriptions of 50 nouns and 20 verbs. All the materials have been semantically annotated and translated into English, to make them easily accessible to the scientific community. The article also presents a preliminary analysis of the BLIND data that highlights both the large degree of overlap between the groups and interesting differences. The complete BLIND norms are freely available and can be downloaded from http://sesia.humnet.unipi.it/blind_data.

Modality-independent encoding of individual concepts in the left parietal cortex

ABSTRACT The organization of semantic information in the brain has been mainly explored through category‐based models, on the assumption that categories broadly reflect the organization of conceptual knowledge. However, the analysis of concepts as individual entities, rather than as items belonging to distinct superordinate categories, may represent a significant advancement in the comprehension of how conceptual knowledge is encoded in the human brain. Here, we studied the individual representation of thirty concrete nouns from six different categories, across different sensory modalities (i.e., auditory and visual) and groups (i.e., sighted and congenitally blind individuals) in a core hub of the semantic network, the left angular gyrus, and in its neighboring regions within the lateral parietal cortex. Four models based on either perceptual or semantic features at different levels of complexity (i.e., low‐ or high‐level) were used to predict fMRI brain activity using representational similarity encoding analysis. When controlling for the superordinate component, high‐level models based on semantic and shape information led to significant encoding accuracies in the intraparietal sulcus only. This region is involved in feature binding and combination of concepts across multiple sensory modalities, suggesting its role in high‐level representation of conceptual knowledge. Moreover, when the information regarding superordinate categories is retained, a large extent of parietal cortex is engaged. This result indicates the need to control for the coarse‐level categorial organization when performing studies on higher‐level processes related to the retrieval of semantic information. HighlightsWe studied the semantic representation of concrete nouns in the left lateral parietal cortex.Four models were used to predict fMRI responses to individual nouns from different categories.Posterior and middle IPS retained high‐level perceptual and semantic information.Information about superordinate categories yielded a different recruitment of parietal regions.

Functional and spatial segregation within the inferior frontal and superior temporal cortices during listening, articulation imagery, and production of vowels

Classical models of language localize speech perception in the left superior temporal and production in the inferior frontal cortex. Nonetheless, neuropsychological, structural and functional studies have questioned such subdivision, suggesting an interwoven organization of the speech function within these cortices. We tested whether sub-regions within frontal and temporal speech-related areas retain specific phonological representations during both perception and production. Using functional magnetic resonance imaging and multivoxel pattern analysis, we showed functional and spatial segregation across the left fronto-temporal cortex during listening, imagery and production of vowels. In accordance with classical models of language and evidence from functional studies, the inferior frontal and superior temporal cortices discriminated among perceived and produced vowels respectively, also engaging in the non-classical, alternative function – i.e. perception in the inferior frontal and production in the superior temporal cortex. Crucially, though, contiguous and non-overlapping sub-regions within these hubs performed either the classical or non-classical function, the latter also representing non-linguistic sounds (i.e., pure tones). Extending previous results and in line with integration theories, our findings not only demonstrate that sensitivity to speech listening exists in production-related regions and vice versa, but they also suggest that the nature of such interwoven organisation is built upon low-level perception.

I. Mani and J. Pustejovsky: Interpreting motion: grounded representations for spatial language

The book under review is the fifth volume of the series Exploration in Language and Space of OUP. It is organized into six chapters: the odd-numbered chapters and part of Chapter 6 are written by Mani, whereas the even-numbered chapters by Pustejovsky. The main aim of the study is to present an integrated perspective on several aspects related to motion: language structure and semantics, concepts of motion, methods for annotating corpora, formal representations needed for computer reasoning about motion. The approach is thus strongly interdisciplinary, with emphasis on formal semantic models and computational reasoning. It is worth underlying that the current reviewer is a linguist, whereas the point of view assumed by the Authors belongs to the framework of computer sciences in general and more specifically to computational linguistics. As a matter of fact, the linguistic research on the topic of space aims at describing and interpreting how space is encoded in the lexicon and in the grammar of natural languages, without disregarding the interaction of concept representations with language and perception (Marotta 2010). On the other hand, this book presents an interdisciplinary perspective in which the semantic structures of language are approached in the perspective of formal representations needed for computer processing of data about motion. Therefore, the semantic model here developed is targeted to computational representation and explicitly conceived as being formally representable. With such a premise, the authors support a compositional and truth-conditional approach, as being suitable in a computational approach. By contrast, embodied cognitive as well as functionalist (e.g., Herkovits 1986; Vandeloise 1991)