An event-related potential study of the relationship between N170 lateralization and phonological awareness in developing readers

Abstract

As reading development progresses, the visual processing of word forms becomes increasingly left-lateralized. This is visible, among other ways, as increased left-lateralization of the N170 ERP component. A primary explanation of this effect, the phonological mapping hypothesis, proposes that the left-lateralization of visual word form processing that accompanies reading development is the result of calling upon left hemisphere auditory language regions to perform the linking of orthography with phonology (phonological mapping). A key, but untested, prediction of the phonological mapping hypothesis is thus that individuals with greater phonological awareness should exhibit more left lateralized visual processing of word forms than individuals with poorer phonological awareness. We set out to test this hypothesis here. We accomplished this by collecting ERPs while children grades 5-6 viewed words, objects, and word/object ambiguous items (e.g., "SMILE" shaped like a smile - hereafter referred to as wobjects). Results revealed that, consistent with the phonological mapping hypothesis, individual phonological awareness (but not other measures of reading development) predicted left-lateralization of the N170 component elicited in response to words (but not item types that were not word-like).

The N170 ERP component differs in laterality, distribution, and association with continuous reading measures for deaf and hearing readers

“…For both groups of readers, individuals with poorer phonological awareness exhibited a larger N170 over occipital electrode sites (left for hearing and right for deaf readers). This pattern differs somewhat from the Sacchi and Laszlo (2016) results with hearing children. For children, better phonological awareness was associated with a larger left-lateralized N170 (also over occipital sites).…”

“…Such a result would point to deaf-specific adaptations of the reading circuit. As noted above, we will also assess whether better phonological awareness skill is associated with greater left-lateralization of ERPs in the N170 epoch for hearing adults, paralleling the Sacchi and Laszlo (2016) results with children, and whether this pattern also holds for deaf adults who have much weaker phonological awareness ability. Finally, we hypothesize that orthographic sensitivity may play a larger role in learning to read for deaf compared to hearing readers because deaf readers may rely more on direct orthographic-to-semantic mappings due to weaker phonological skills.…”

“…Recently, Sacchi and Laszlo (2016) explicitly tested the hypothesis that the N170 becomes increasingly left lateralized because phonological mapping processes drive early reading mechanisms towards the left hemisphere. They argued that an important prediction of the phonological mapping hypothesis is that greater phonological awareness should go along with more left lateralized visual word processing.…”

Time will tell: A longitudinal investigation of brain‐behavior relationships during reading development

“…The N400 was measured from 475–575 ms poststimulus onset. Each of these windows is later than would be expected in adults; however, it is not uncommon for these components to peak later in children than in adults (e.g., Khalifian et al, ; Sacchi & Laszlo, ).…”

“…Though the functional locus of the N1 is relatively low‐level—representing the extraction of orthographic features from print—N1 effects have nevertheless been associated with behavioral measures of higher level processing in children. In particular, N1 effect magnitude has been shown to associate with phonological awareness, vocabulary (Sacchi & Laszlo, ), and even report card score (Khalifian, Stites, & Laszlo, ). These results are consistent with the less specific finding that children with overall reading impairment elicit reduced N1 effects (e.g., Araújo et al, ).…”