Methods Effective functional connectivity of phonological and semantic processing processing during word reading Cheryl M. Capek 1,2, Simandeep Poonian 1 and Joseph T. Devlin 1,2 Cognitive, Perceptual & Brain Sciences, UCL, UK 1, Institute of Cognitive Neuroscience UCL, UK 2 Results Activation in aIFC present for Semantics > Phonology Introduction 32 (14M, 18F) participants Mean age = 24.6 years (s.d. = 5.1) Native English speakers Monolingual Right handed Stimuli: word pairs Phonology task (Do the words rhyme?) Independent of orthography Semantic task (Do the words belong to the same semantic category?) 100 word pairs / condition; matched on: word length, number of letter & syllables, frequency, familiarity, imageability, concreteness Mixed design with jittered ISI (4-10s, mean=7) Two lists; order counterbalanced Scanning: 1.5T Siemens Avanto scanner, GE-EPI, TR =3s, TE =50ms, 3x3x3.5 mm resolution Analysis (SPM5) Second-level random effects: task>fixation & phonology vs. semantics DCM (Friston et al., 2003): Volumes of interest defined for each subject: 1. ventral occipito-temporal cortex (vOTC) 2. supramarginal gyrus (SMG) 3. posterior inferior frontal cortex (pIFC) 4. anterior inferior frontal cortex (aIFC) IFC) Definition based on: Activation in effects-of-interest F-map (p <.001, uncorrected) in all four anatomically constrained regions 26 subjects met the inclusion criteria Discussion Group activations consistent with previous studies showing word reading elicits activation in a widely distributed brain network including our 4 ROIs Our findings show: 1.Very strong evidence favouring the simpler model with pair-wise functional connectivity between: vOTC SMG SMG posterior IFC Posterior anterior IFC vOTC anterior IFC 2.Activity was modulated by task Semantic task increased BOLD signal magnitude in anterior IFC Phonological task increased functional coupling between vOTC and posterior IFC, although it unclear how this is mediated anatomically Discrepancy between location of modulatory effects in the two models suggests it is not vOTC SMG pIFC Fully-connected model suggests another pathway linking vOTC and pIFC, which may correspond to the inferior occipito-frontal fasciculus 3.Results are consistent with two anatomical-functional routes to reading (Plaut et al.,1996; Coltheart et al., 2001) Dorsal route that is dominant for phonological processing (Saur et al., 2008; Mechelli et al, 2005) Ventral route that is dominant for semantic processing (Catani et al., 2003; Binder et al., 2005) No clear evidence for an independent third (i.e. lexical) route Acknowledgements This research was supported by the Wellcome Trust References Binder, J. 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Proc Natl Acad Sci U S A, 105(46), No significant difference on accuracy or RT across the phonology and semantic tasks Phonology > fixationSemantics > fixation Behavioural (n=32) Random Effects (n=32) idea + notion knows + nose Aims of the current study: 1)to determine functional connectivity between the regions of LIFC and the temporal lobes 2)to investigate whether this is significantly modulated by task 3)to determine whether the functional connections correspond to anatomical fronto-temporal connections Anatomically-Constrained Model Fully-Connected model DCMs (n = 26) Lesion and neuroimaging studies reliably show that word reading involves regions of the left hemisphere including: Ventral occipito-temporal cortex (vOTC) Inferior parietal cortex (e.g., SMG) Inferior frontal cortex (IFC) Neuroimaging (Poldrack, 1999; Demonet, 1992, Fiez et al., 1997) and neurostimulation (Gough & Devlin, 2005) studies show evidence of functionally distinct subdivisions in the LIFC: Phonology -posterior IFC Semantics -anterior IFC + + freight plate + sour your time + + wolf drain + + lake sea Semantics > Phonology Phonology > Semantics - n.s. p <.001 (uncorrected) For both models: all intrinsic connections significant at p <.01 Model comparison: Anatomically- constrained model favoured for each subject (Bayes Factors: mean = 24,171 (range: ,000)) Significant modulatory effects for Phonology only Phonology Baseline Semantics + … All 4 ROIs are significantly active for both tasks (at p<0.001 uncorrected) pIFC aIFC SMG vOTC SMG vOTC L R L R L R Activations ( 10 voxels) overlaid on mean T1-weighted image p <.05 (corrected) p <.001 (uncorrected) Significant modulatory effect for Phonology (p <.01) Modulatory effect for Phonology (p =.11) Significant modulatory effect for Phonology (p =.03) Contact: 33sec 33s 15s pIFC aIFC Accuracy RT Phonology Semantics Mean % Correct msec