Authors:

HAUK O., Kherif, F., DAVIS, M. & PULVERMULLER, F.

Reference:

Year of publication:

2006

CBU number:

6463

Abstract:

Psycholinguistics has documented a range of parameters that influence visual word recognition. These parameters, can be measured objectively (e.g., word frequency, length, n-gram frequency) or obtained from subjective ratings (e.g., familiarity, imageability, action-relatedness), and are often highly intercorrelated. This study aimed at disentangling the effects of these variables using a linear regression analysis of event-related fMRI data. For a set of 250 mono-syllabic words, 23 psycholinguistic variables were obtained, and reduced using Principal Components Analysis to a set of 5 predictor variables: Length&Neighbourhood Size (LN), N-gram frequency (NG), Frequency&Familiarity (FF), Imageability&Visual-relatedness (IV), and Body&Action-relatedness (BA). These were entered as parametric modulators in the general linear model in an SPM analysis of fMRI data (Bruker, 3T scanner, TR = 3secs) from 21 subjects silently reading words on a computer screen (SOA: 2.5s, stimulus duration: 0.1s). Form-related variables (LN, NG) had little effect on brain activation. A variable indexing the overall ease of recognition (FF) modulated activation in left fusiform and inferior frontal gyri, consistent with previous observations. Semantic variables (IV and BA) modulated activation in temporal and frontal lobe regions previously associated with domain-specific semantic content. IV predicted activity in bilateral regions of the fusiform gyrus, whereas BA affected activation in the middle temporal gyrus, pre-central gyrus, and prefrontal areas. Visual word recognition therefore activates a widely distributed frontal and temporal network with subparts specialised for specific types of associated semantic information. The data support a distinction between lexical and category-specific semantic networks.