Encoding in the Visual Word Form Area: An fMRI Adaptation Study of Words versus Handwriting (original) (raw)
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On the Functional Neuroanatomy of Visual Word Processing: Effects of Case and Letter Deviance
Journal of cognitive …, 2009
This fMRI study contrasted case-deviant and letter-deviant forms with familiar forms of the same phonological words (e.g., TaXi and Taksi vs. Taxi) and found, that both types of deviance led to increased activation in a left occipitotemporal region corresponding to the Visual Word Form Area. Case-deviant items, in addition, led to increased activation in a right occipitotemporal region and in a left occipital and a left posterior occipitotemporal region, possibly reflecting the increased demands on letter form coding. For letter-deviant items, in addition to the increased left occipitotemporal activation, a main finding was increased activation primarily in extended left frontal regions, possibly reflecting sublexically mediated access to word phonology. These findings are consistent with general features of cognitive dual-route models of visual word processing. Furthermore, they add support to the main feature of Dehaene et al.'s (2005) neural model of early stages of visual word processing . However, the increased activation found for case-deviant items in the VWFA cannot be immediately reconciled with the assumption of completely abstract case-independent orthographic word codes in the VWFA.
Language-specific tuning of visual cortex? Functional properties of the Visual Word Form Area
Brain, 2002
The ®rst steps in the process of reading a printed word belong to the domain of visual object perception. They culminate in a representation of letter strings as an ordered set of abstract letter identities, a representation known as the Visual Word Form (VWF). Brain lesions in patients with pure alexia and functional imaging data suggest that the VWF is subtended by a restricted patch of left-hemispheric fusiform cortex, which is reproducibly activated during reading. In order to determine whether the operation of this Visual Word Form Area (VWFA) depends exclusively on the visual features of stimuli, or is in¯uenced by language-dependent parameters, brain activations induced by words, consonant strings and chequerboards were compared in normal subjects using functional MRI (fMRI). Stimuli were presented in the left or right visual hemi®eld. The VWFA was identi®ed in both a blocked-design experiment and an event-related experiment as a left-hemispheric inferotemporal area showing a stronger activation to alphabetic strings than to chequerboards, and invariant for the spatial location of stimuli. In both experiments, stronger activations of the VWFA to words than to strings of consonants were observed. Considering that the VWFA is equally activated by real words and by readable pseudowords, this result demonstrates that the VWFA is initially plastic and becomes attuned to the orthographic regularities that constrain letter combination during the acquisition of literacy. Additionally, the use of split-®eld stimulation shed some light on the cerebral bases of the classical right visual ®eld (RVF) advantage in reading. A left occipital extrastriate area was found to be activated by RVF letter strings more than by chequerboards, while no symmetrical region was observed in the right hemisphere. Moreover, activations in the precuneus and the left thalamus were observed when subjects were reading RVF versus left visual ®eld (LVF) words, and are likely to re¯ect the attentional component of the RVF advantage.
The Neural Basis of Visual Word Form Processing: A Multivariate Investigation
Cerebral Cortex, 2013
Current research on the neurobiological bases of reading points to the privileged role of a ventral cortical network in visual word processing. However, the properties of this network and, in particular, its selectivity for orthographic stimuli such as words and pseudowords remain topics of significant debate. Here, we approached this issue from a novel perspective by applying pattern-based analyses to functional magnetic resonance imaging data. Specifically, we examined whether, where and how, orthographic stimuli elicit distinct patterns of activation in the human cortex. First, at the category level, multivariate mapping found extensive sensitivity throughout the ventral cortex for words relative to false-font strings. Secondly, at the identity level, the multi-voxel pattern classification provided direct evidence that different pseudowords are encoded by distinct neural patterns. Thirdly, a comparison of pseudoword and face identification revealed that both stimulus types exploit common neural resources within the ventral cortical network. These results provide novel evidence regarding the involvement of the left ventral cortex in orthographic stimulus processing and shed light on its selectivity and discriminability profile. In particular, our findings support the existence of sublexical orthographic representations within the left ventral cortex while arguing for the continuity of reading with other visual recognition skills.
The left fusiform area is affected by written frequency of words
Neuropsychologia, 2008
The recent neuroimaging literature gives conflicting evidence about whether the left fusiform gyrus (FG) might recognize words as unitary visual objects. The sensitivity of the left FG to word frequency might provide a neural basis for the orthographic input lexicon theorized by reading models . Surface dyslexia: Cognitive and neuropsychological studies of phonological reading. London: Lawrence Erlbaum]. The goal of this study was to investigate the time course and neural correlates of word processing in right-handed readers engaged in an orthographic decision task. Three hundred and twenty Italian words of high and low written frequency and 320 non-derived legal pseudowords were presented for 250 ms in the central visual field. ERPs were recorded from 128 scalp sites in 10 Italian University students. Behavioural data showed a word superiority effect, with faster RTs to words than pseudo-words. Left occipito/temporal N2 (240 ms) was greater to high-frequency than lowfrequency words and pseudo-words. According to the swLORETA inverse solution, the underlying neural source of this effect was located in the left fusiform gyrus of the occipital lobe (X = −29, Y = −66, Z = −10, BA19) and the right superior temporal gyrus (X = 51, Y = 6, Z = −5, BA22), which are probably involved in word recognition and semantic representation, respectively. Later frontal ERP components, LPN (300-350) and P3 (400-500), also showed strong lexical sensitivity, thus suggesting implicit semantic processes. The results shed some light on the possible neural substrate of visual reading disabilities such as developmental surface dyslexia or pure alexia.
The visual word form area: expertise for reading in the fusiform gyrus
Trends in Cognitive Sciences, 2003
Brain imaging studies reliably localize a region of visual cortex that is especially responsive to visual words. This brain specialization is essential to rapid reading ability because it enhances perception of words by becoming specifically tuned to recurring properties of a writing system. The origin of this specialization poses a challenge for evolutionary accounts involving innate mechanisms for functional brain organization. We propose an alternative account, based on studies of other forms of visual expertise (i.e. bird and car experts) that lead to functional reorganization. We argue that the interplay between the unique demands of word reading and the structural constraints of the visual system lead to the emergence of the Visual Word Form Area.
Word and non-word reading: What role for the Visual Word Form Area
Neuroimage, 2005
The putative role of the so-called Visual Word Form Area (VWFA) during reading remains under debate. For some authors, this region is specifically involved in a pre-lexical processing of words and pseudowords, whereas such specificity is challenged by others given the VWFA involvement during both non-word reading and word listening. Here, we further investigated this issue, measuring BOLD variations and their lateralization with fMRI during word and nonword reading, in order to evaluate the lexicality effect, and during reading and listening of words, in order to evaluate the impact of stimulus delivery modality on word processing networks. Region of interest (ROI) analysis was first performed in three target areas: 1-VWFA as defined by a meta-analysis of the word reading literature, 2-a middle temporal area (T2) found co-activated by both word reading and listening, 3-an inferior occipital area (OI) belonging to the unimodal visual cortex of the inferior occipital gyrus. VWFA activity was found not different between word and non-word reading but was more leftward lateralized during word reading due to a reduction of activity in the VWFA right counterpart. A similar larger leftward lateralization during word reading was also uncovered in the T2 ROI but was related to a larger left side activity. Such a lexicality effect was not observed in the OI ROI. By contrast, BOLD increases during listening were restricted to the left VWFA and T2 ROIs. Voxel-based analysis (SPM99) showed that semantic areas were more active during word than non-word reading and co-activated by both reading and listening, exhibiting a left lateralized activity in all tasks. These results indicate that the left VWFA would be the place where visual and verbal representations bind under the control of left semantic areas. D
Opposite effects of visual and auditory word-likeness on activity in the visual word form area
The present fMRI study investigated the effects of word-likeness of visual and auditory stimuli on activity along the ventral visual stream. In the context of a one-back task, we presented visual and auditory words, pseudowords, and artificial stimuli (i.e., false-fonts and reversed-speech, respectively). Main findings were regionally specific effects of word-likeness on activation in a left ventral occipitotemporal region corresponding to the classic localization of the Visual Word Form Area (VWFA). Specifically, we found an inverse word-likeness effect for the visual stimuli in the form of decreased activation for words compared to pseudowords which, in turn, elicited decreased activation compared to the artificial stimuli. For the auditory stimuli, we found positive word-likeness effects as both words and pseudowords elicited more activation than the artificial stimuli. This resulted from a marked deactivation in response to the artificial stimuli and no such deactivation for words and pseudowords. We suggest that the opposite effects of visual and auditory word-likeness on VWFA activation can be explained by assuming the involvement of visual orthographic memory representations. For the visual stimuli, these representations reduce the coding effort as a function of word-likeness. This results in highest activation to the artificial stimuli and least activation to words for which corresponding representations exist. The positive auditory word-likeness effects may result from activation of orthographic information associated with the auditory words and pseudowords. The view that the VWFA has a primarily visual function is supported by our findings of high activation to the visual artificial stimuli (which have no phonological or semantic associations) and deactivation to the auditory artificial stimuli. According to the phenomenon of cross-modal sensory suppression such deactivations during demanding auditory processing are expected in visual regions.
Neuroimage, 2010
Based on our previous work, we expected the Visual Word Form Area (VWFA) in the left ventral visual pathway to be engaged by both whole-word recognition and by serial sublexical coding of letter strings. To examine this double function, a phonological lexical decision task (i.e., "Does xxx sound like an existing word?") presented short and long letter strings of words, pseudohomophones, and pseudowords (e.g., Taxi, Taksi and Tazi). Main findings were that the length effect for words was limited to occipital regions and absent in the VWFA. In contrast, a marked length effect for pseudowords was found throughout the ventral visual pathway including the VWFA, as well as in regions presumably engaged by visual attention and silentarticulatory processes. The length by lexicality interaction on brain activation corresponds to wellestablished behavioral findings of a length by lexicality interaction on naming latencies and speaks for the engagement of the VWFA by both lexical and sublexical processes.