Publications

Abstract

Neuronal populations code similar concepts by similar activity patterns across the human brain's semantic networks. However, it is unclear to what extent such meaning-to-symbol mapping reflects distributional statistics, or experiential information grounded in sensorimotor and emotional knowledge. We asked whether integrating distributional and experiential data better distinguished conceptual categories than each method taken separately. We examined the similarity structure of fMRI patterns elicited by visually presented action- and object-related words using representational similarity analysis (RSA). We found that the distributional and experiential/integrative models respectively mapped the high-dimensional semantic space in left inferior frontal, anterior temporal, and in left precentral, posterior inferior/middle temporal cortex. Furthermore, results from model comparisons uncovered category-specific similarity patterns, as both distributional and experiential models matched the similarity patterns for action concepts in left fronto-temporal cortex, whilst the experiential/integrative (but not distributional) models matched the similarity patterns for object concepts in left fusiform and angular gyrus.

Abstract

When preparing to name an object, semantic knowledge about the object and its attributes is activated, including perceptual properties. It is unclear, however, whether semantic attribute activation contributes to lexical access or is a consequence of activating a concept irrespective of whether that concept is to be named or not. In this study, we measured neural responses using fMRI while participants named objects that are typically green or red, presented in black line drawings. Furthermore, participants underwent two other tasks with the same objects, color naming and semantic judgment, to see if the activation pattern we observe during picture naming is (a) similar to that of a task that requires accessing the color attribute and (b) distinct from that of a task that requires accessing the concept but not its name or color. We used representational similarity analysis to detect brain areas that show similar patterns within the same color category, but show different patterns across the two color categories. In all three tasks, activation in the bilateral fusiform gyri (“Human V4”) correlated with a representational model encoding the red–green distinction weighted by the importance of color feature for the different objects. This result suggests that when seeing objects whose color attribute is highly diagnostic, color knowledge about the objects is retrieved irrespective of whether the color or the object itself have to be named.

Abstract

Speaking requires the temporally coordinated planning of core linguistic information, from conceptual meaning to articulation. Recent neurophysiological results suggested that these operations involve a cascade of neural events with subsequent onset times, whilst competing evidence suggests early parallel neural activation. To test these hypotheses, we examined the sources of neuromagnetic activity recorded from 34 participants overtly naming 134 images from 4 object categories (animals, tools, foods and clothes). Within each category, word length and phonological neighbourhood density were co-varied to target phonological/phonetic processes. Multivariate pattern analyses (MVPA) searchlights in source space decoded object categories in occipitotemporal and middle temporal cortex, and phonological/phonetic variables in left inferior frontal (BA 44) and motor cortex early on. The findings suggest early activation of multiple variables due to intercorrelated properties and interactivity of processing, thus raising important questions about the representational properties of target words during the preparatory time enabling overt speaking.

Abstract

This chapter focuses on the issue of motor awareness. It addresses three main questions: What exactly are we aware of when making a movement? What is the contribution of afferent and efferent signals to motor awareness? What are the neural bases of motor awareness? It reviews evidence that the motor system is mainly aware of its intention. As long as the goal is achieved, nothing reaches awareness about the kinematic details of the ongoing movements, even when substantial corrections have to be implemented to attain the intended state. The chapter also shows that motor awareness relies mainly on the central predictive computations carried out within the posterior parietal cortex. The outcome of these computations is contrasted with the peripheral reafferent input to build a veridical motor awareness. Some evidence exists that this process involves the premotor areas.

Abstract

When we talk we communicate our intentions. Although the origin of intentional action is debated in cognitive neuroscience, the question of how the brain generates the intention in speech remains still open. Using magnetoencephalography, we investigated the cortical dynamics engaged when healthy subjects attended to either their intention to speak or their actual speech. We found that activity in the right and left parietal cortex increased before subjects became aware of intending to speak. Within the time window of parietal activation, we also observed a transient left frontal activity in Broca's area, a crucial region for inner speech. During attention to speech, neural activity was detected in left prefrontal and temporal areas and in the temporoparietal junction. In agreement with previous results, our findings suggest that the parietal cortex plays a multimodal role in monitoring intentional mechanisms in both action and language. The coactivation of parietal regions and Broca's area may constitute the cortical circuit specific for controlling intentional processes during speech.