Neural dynamics of the impact of font style on lexical decision making in adult dyslexia

Good reading comprehension is indispensable in many situations including contract-based transactions that have become so prevalent in our everyday lives. People with dyslexia often exhibit impairments in this important cognitive process. Although the effects of italics - a commonly used style for highlighting important content in a range of documents - and font in general, have been explored with behavioural measures, their impact on human brain dynamics remains poorly understood. Here, we used electroencephalography (EEG) to investigate the specific effects of italics in a sentence reading lexical decision task in adult dyslexics and an age matched non-dyslexia group. Overall, the performance of dyslexics was worse. Cluster-based event-related potential (ERP) analysis revealed that brain responses within the first 300 ms following the decision stimulus differed in amplitude and spatial distribution between dyslexics and non-dyslexics when processing italicised text. An initial ERP component over occipitotemporal electrode sites started to differ between the groups as early as 167 ms following the onset of short italicised decision words. A subsequent ERP component over centrofrontal electrodes showed differences lasting until about 300 ms post-stimulus onset. Inter-individual amplitude differences in this centrofrontal neural signal were predictive of behavioural performance across participants, further highlighting the role of fast post-sensory linguistic processes in lexical decision making. Crucially, our findings emphasise the importance of choosing font style carefully to optimise word processing and reading comprehension by everyone.