Beyond the visual word form area: The orthography–semantics interface in spelling and reading

Abstract

Lexical orthographic information provides the basis for recovering the meanings of words in reading and for generating correct word spellings in writing. Research has provided evidence that an area of the left ventral temporal cortex, a subregion of what is often referred to as the visual word form area (VWFA), plays a significant role specifically in lexical orthographic processing. The current investigation goes beyond this previous work by examining the neurotopography of the interface of lexical orthography with semantics. We apply a novel lesion mapping approach with three individuals with acquired dysgraphia and dyslexia who suffered lesions to left ventral temporal cortex. To map cognitive processes to their neural substrates, this lesion mapping approach applies similar logical constraints to those used in cognitive neuropsychological research. Using this approach, this investigation: (a) identifies a region anterior to the VWFA that is important in the interface of orthographic information with semantics for reading and spelling; (b) determines that, within this orthography–semantics interface region (OSIR), access to orthography from semantics (spelling) is topographically distinct from access to semantics from orthography (reading); (c) provides evidence that, within this region, there is modality-specific access to and from lexical semantics for both spoken and written modalities, in both word production and comprehension. Overall, this study contributes to our understanding of the neural architecture at the lexical orthography–semantic–phonological interface within left ventral temporal cortex.

Keywords:

• Orthography
• Semantics
• Visual word form area
• Reading
• Spelling

We would like to thank D.P.T., D.S.N., and L.H.D. for their dedication and good humour through many hours of testing. We are grateful to Michael McCloskey and Teresa Schubert for providing information and data regarding L.H.D. and to Kyrana Tsapkini for her contributions to data collection and analysis for D.P.T. and control participants.

This research was made possible through the support of the National Institutes of Health (NIH) [grant number DC006740], [grant number 1-P50-DC012283-01A1].

Notes

¹ We use the term “lexical” to modify “semantic system” in the way in which the term “verbal” is sometimes used. We use “lexical” to distinguish the semantic representations of concepts that correspond to specific words of the language from those that do not. In our opinion, the term “lexical” denotes this distinction more precisely than does the term “verbal”.

² A recent study reported on an individual with damage to the left ventral occipitotemporal cortex that extended anterior to the VWFA (y= –88 to –30; Seghier et al., 2012). While lexical orthographic deficits were not specifically reported by the authors, the presence of frequency and regularity effects in reading indicate some degree of lexical deficit in reading (in addition to the clear prelexical impairment), and some of the errors reported in the spelling sample (see Seghier et al., 2012, Supplementary materials) are consistent with some degree of lexical orthographic deficit also in spelling.

³ The work of McCloskey and Schubert (2014) and Schubert and McCloskey (2013) documents that L.H.D.’s reading impairment is based on impairment in prelexical processing of letters, specifically in the mapping between intact representations of letter shapes to abstract letter identities. This conclusion was based, among other things, on three key findings: (a) intact letter form processing as evidenced by intact ability to discriminate between real letters and pseudoletters; (b) impaired access to abstract letter identities from visual input as evidenced by impaired letter naming and impaired identification of lower-case letters with their upper-case counterparts; and (c) intact orthographic LTM processing for reading as evidenced by the ability to recognize words from oral spelling.

⁴ Two points are worth making regarding this task. First, for irregular/exception words, access to orthographic LTM will be as necessary as it is in reading. Second, if we assume two different orthographic LTM stores for reading and spelling, one could imagine (a rather cumbersome strategy) by which one uses a subset of the letter names to generate various candidate spellings from the orthographic LTM used for spelling, which are then checked against the letter names held in phonological working memory. In that case, the orthographic LTM store used to generate candidate spellings would be the one used for spelling. Critically, L.H.D.’s spelling performance (described in the previous section) rules out this interpretation as it indicates that access to orthographic LTM for word spelling is clearly impaired and marked by the production of phonologically plausible errors. In contrast, as the results of recognition of oral spelling task show—she is fully intact in accessing orthographic LTM when she can bypass visual processing of letter shapes.