The VWFA Controversy

There has been a controversy on whether the visual word form area (VWFA) is specialized for processing visual word processing. Proponents of the majority view suggested that the VWFA is specialized for processing visual words and word-like stimuli independent of language. The supporters of the minority view have “questioned whether visual word processing is localized to the VWFA and whether this region selectively processes visually presented words” (Slotnick). In class, we discussed eight studies that had mixed views.

For example, Dehaene et al. (2001), Glezer et al. (2009), Pegado et al. (2011), and Reich et al. (2011) are all proponents of the majority view. Dehaene et al. (2001) argue that unseen masked words activate extrastriate, fusiform and precentral regions but do not elicit a significant activation when the same words are consciously perceived. For example, Figure 2 reveals fMRI activations to visible and masked words in the first experiment. Activation at the left fusiform gyrus showed a twelvefold increase in activation on visible trials compared to masked trials. Dehaene et al. (2001) concluded that VWFA mediates beyond conscious processing because masked words produced a small magnitude of activity in the VWFA. The study said, “in the left fusiform cortex, the activation to maksed words was reduced to 8.6% of that found to conscious words” (p. 753). Glezer et al. (2009) suggest that the VWFA operates at the lexical level rather than the orthographic level. To test the lexical hypothesis, the study conducted three sets of fMRI experiments. Words were presented in prime/target paris and the study examined the “same” condition, the “1L” condition, and the “different” condition. The study found a “significant adaptation in the VWFA ROIs for the same [condition] when compared with different and 1L [conditions]. The response levels did not differ significantly between the 1L and different conditions” (p. 201). 

Pegado et al. (2011) investigated whether the VWFA discriminated letters from their mirror images in expert readers. First, their analysis focused on the critical mirror priming effects repetition suppression for mirror-reversed pairs. When both pictures and “letters were collapsed, [they] found a main effect of mirror priming exactly at the VWFA coordinates” (p. 744). Second, pictures showed greater mirror repetition suppression than letters in the left occipito-temporal region when they lowered the voxel-level threshold (Fig 4A). Third, the restricted area in the left occipitotemporal cortex revealed greater mirror image discrimination for letters than for pictures. Reich et al. (2011) investigated which brain area plays the role of the VWFA in blind people and found that the VWFA is a reading area that develops specialization for reading regardless of visual experience. Also, they found that the activation for Braille words versus nonsense Braille was significantly higher than for verb generation (VG) versus verb generation control (VGc) (Figure 2). This suggested that the “VWFA is specific to reading and that its activation during Braille reading cannot be reduced to modality-independent general language processing” (363).   

Szwed et al. (2011), Woodhead et al. (2011) , Chen et al. (2019), and Strappini et al. (2017) are proponents of the minority view. Szwed et al. (2011) argue that the VWFA is involved in both word and object processing. When they conducted a contrast analysis, they found that words versus scrambled words produced a significant activity in the VWFA relative to the objects versus scrambled objects. However, when they conducted a region of interest analysis, they found that the ROI at MNI y = -51 was the only region that did not show a significant activation relative to baseline for words than objects (Figure 4). Woodhead et al. (2011) found that the left occipitotemporal cortex is more activated by high than low spatial frequency (SF), whereas the right occipitotemporal cortex responds more to low than high spatial frequencies. A paired t-test comparing “average phase angle in the left and right hemispheres showed that the left hemisphere preferred significantly higher spatial frequencies than the right hemisphere” (p. 4). Figure 4 shows a greater activation for low than high SF in the right fusiform gyrus. Woodhead et al. (2011) concluded that the VWFA responds to any stimulus that has high frequency components, such as words or objects.  

Chen et al. (2019) concluded that VWFA has a role in visual function beyond reading and is linked to fronto-parietal attention systems. Also, the study argued that VWFA has a moderate-strong-connectivity “with nodes of the brain’s language network, particularly STS regions associated with phonological processing, as well as fronto-parietal attentional systems, particularly the IPS” (p. 7). Strappini et al. (2017) found that crowding increased BOLD activity in a network of several areas, including VWFA and concluded that visual crowding is a mid-level visual phenomenon. For example, Figure 4A shows that in both V4/V8 and VWFA areas, the mean signal change was stronger in the attended than in the unattended condition. 

Taking all these articles together, I cannot ignore the significant findings of the Dehaene et al. (2001) and Reich et al. (2011), and I am siding with the proponents of the majority view. I would propose a study on undergraduate students and stimulate their left ventral occipito- temporal cortex. I would present words in prime/target pairs and examine the same, 1L, and different conditions (Glezer et al. 2009). Then, I would use fMRI and a functional connectivity map to determine which region is highly connected to VWFA (Chen et al. 2019). After that, I would measure the modulations in the VWFA before and after the application of TMS, which would require combining fMRI-TMS protocol. I predict to see no adaptation in the VWFA ROIs for the “same” condition when compared with “different” and “1L” conditions.  

Works cited

Chen, L., Wassermann, D., Abrams, D. A., Kochalka, J., Gallardo-Diez, G., & Menon, V. (2019). The visual word form area (VWFA) is part of both language and attention circuitry. Nature Communications, 10(1). doi: 10.1038/s41467-019-13634-z

Dehaene, S., Naccache, L., Cohen, L., Bihan, D. L., Mangin, J.-F., Poline, J.-B., & Rivière, D. (2001). Cerebral mechanisms of word masking and unconscious repetition priming. Nature Neuroscience, 4(7), 752–758. doi: 10.1038/89551

Glezer, L. S., Jiang, X., & Riesenhuber, M. (2009). Evidence for Highly Selective Neuronal Tuning to Whole Words in the “Visual Word Form Area.” Neuron, 62(2), 199–204. doi: 10.1016/j.neuron.2009.03.017

Pegado, F., Nakamura, K., Cohen, L., & Dehaene, S. (2011). Breaking the symmetry: Mirror discrimination for single letters but not for pictures in the Visual Word Form Area. NeuroImage, 55(2), 742–749. doi: 10.1016/j.neuroimage.2010.11.043

Reich, L., Szwed, M., Cohen, L., & Amedi, A. (2011). A Ventral Visual Stream Reading Center Independent of Visual Experience. Current Biology, 21(5), 363–368. doi: 10.1016/j.cub.2011.01.040

Slotnick, S. (2013). Controversies in Cognitive Neuroscience. doi: 10.1007/978-1-137-27236-2

Strappini, F., Galati, G., Martelli, M., Pace, E. D., & Pitzalis, S. (2017). Perceptual integration and attention in human extrastriate cortex. Scientific Reports, 7(1). doi: 10.1038/s41598-017-13921-z

Szwed, M., Dehaene, S., Kleinschmidt, A., Eger, E., Valabrègue, R., Amadon, A., & Cohen, L. (2011). Specialization for written words over objects in the visual cortex. NeuroImage, 56(1), 330–344. doi: 10.1016/j.neuroimage.2011.01.073

Woodhead, Z. V. J., Wise, R. J. S., Sereno, M., & Leech, R. (2011). Dissociation of Sensitivity to Spatial Frequency in Word and Face Preferential Areas of the Fusiform Gyrus. Cerebral Cortex, 21(10), 2307–2312. doi: 10.1093/cercor/bhr008

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