Brain Source Correlates of Speech Perception and Reading Processes in Children With and Without Reading Difficulties

Abstract

Neural correlates in reading and speech processing have been addressed extensively in the literature. While reading skills and speech perception have been shown to be associated with each other, their relationship remains debatable. In this study, we investigated reading skills, speech perception, reading, and their correlates with brain source activity in auditory and visual modalities. We used high-density event-related potentials (ERPs), fixation-related potentials (FRPs), and the source reconstruction method. The analysis was conducted on 12-13-year-old schoolchildren who had different reading levels. Brain ERP source indices were computed from frequently repeated Finnish speech stimuli presented in an auditory oddball paradigm. Brain FRP source indices were also computed for words within sentences presented in a reading task. The results showed significant correlations between speech ERP sources and reading scores at the P100 (P1) time range in the left hemisphere and the N250 time range in both hemispheres, and a weaker correlation for visual word processing N170 FRP source(s) in the posterior occipital areas, in the vicinity of the visual word form areas (VWFA). Furthermore, significant brain-to-brain correlations were found between the two modalities, where the speech brain sources of the P1 and N250 responses correlated with the reading N170 response. The results suggest that speech processes are linked to reading fluency and that brain activations to speech are linked to visual brain processes of reading. These results indicate that a relationship between language and reading systems is present even after several years of exposure to print.

Keywords: ERPs; FRPs; auditory N250; auditory P1; brain correlates; reading; source reconstruction; visual N170.

Figure 1

(A) (a) Auditory/speech ERPs in the CTRD group (N = 80) grand average. Butterfly plots for the responses to the standard stimulus “suu” over 129 electrodes. The boxes around the peaks indicate P1, P1-2, N250, and N250-2 responses. (b) The corresponding mean topographic maps for the time windows of 70–120 ms (P1), 150–200 ms (P1-2), 230–280 ms (N250), and 360–410 ms (N250-2), respectively. (c) Cortical CLARA reconstruction for each component. (B) (a) Visual/reading FRPs in the CTRD group (N = 80) grand average. Butterfly plots for the responses to word stimuli over 129 electrodes. (b) The topographic map of N170 at 170 ms and (c) its cortical source CLARA reconstruction.

Figure 2

Summary results showing significant correlations between the source activity in speech processing and reading in the brain-to-brain analysis for the P1-2 vs. N170 (A) and N250 vs. N170 (B).