After all, printed text is a static image. One might ask what motion discrimination has to do with reading. Examining measurements of individual subjects, rather than the average measurements of groups of subjects, reveals that not all people with dyslexia present this impairment in “motion discrimination,” but many do show a pronounced and robust difficulty with this task. Neural responses in this region of cortex show reduced sensitivity to moving stimuli in some children and adults with dyslexia (Demb, Boynton, & Heeger, 1997 Eden et al., 1996). This effect is also apparent in brain measurements of a particular region of the visual system that is involved in the perception of motion.

When the speed of motion in the two displays is similar, children and adults with dyslexia experience more difficulty identifying the faster moving visual stimulus than do children and adults with typical reading skills. This effect can be observed in behavioral measurements that ask observers to compare the speed of motion between two different, sequentially presented computer displays. One of the most extensively replicated findings is that, on average, children and adults with dyslexia show a decreased sensitivity to visual motion (Ben-Shachar, Dougherty, Deutsch, & Wandell, 2007 Demb, Boynton, Best, & Heeger, 1998 Stein & Walsh, 1997). Motion Processing-Disregarding the debate about causality for the moment, several observations have been made about the visual system in children and adults with dyslexia. The following sections are intended to, first, give a few examples of visual functions that people with dyslexia tend to struggle with and, second, clarify the implications of these findings for treating dyslexia.Ī Few Observations about the Visual System in People with Dyslexia This debate is unlikely to be resolved anytime soon: Complex, developmental disorders like dyslexia are rarely explained by a single causal factor. Whether these visual system impairments are typically the underlying cause of reading difficulties, or the downstream result of other non-visual impairments, has been fiercely debated for decades. However, an array of scientific evidence supports the view that many children and adults with dyslexia can have difficulties with a range of visual functions, ranging from the ability to perceive a moving stimulus to the ability to ignore distracting information and attend to pertinent information in a visual scene. The importance of phonemic awareness for learning to read, the central role of phonemic awareness impairments in developmental dyslexia, and the success of interventions targeting phonemic awareness skills, have prompted many scientists to minimize the role of the visual system in reading and the role of visual impairments in dyslexia. Impaired phonemic awareness is the most common precursor to dyslexia, and interventions that target phonemic awareness skills have been shown to be the most effective treatment for the average child with dyslexia (Vellutino, Fletcher, Snowling, & Scanlon, 2004). A comprehensive understanding of reading should build on an understanding of the visual system, which represents one potential bottleneck: If the visual system fails to rapidly and accurately recognize small printed symbols (i.e., letters) then any effort to teach reading skills with conventional approaches will have limited success.Ī major achievement in the scientific study of reading has been to demonstrate the central role of phonemic awareness, or the ability to attend to and manipulate speech sounds (phonemes), in the development of skilled reading (Bradley & Bryant, 1983 Wagner & Torgesen, 1987).

An impairment in any one of these systems, or the bundles of wires (axons) that connect them, could cause reading difficulty (Wandell, Rauschecker, & Yeatman, 2011). Indeed, reading might start in the retina and the visual cortex, but successful decoding of even a single written word requires the participation of multiple brain systems including regions of the brain that are specialized for processing language, spatial attention, programming eye movements, and more.įrom a neuroscience perspective, reading requires signals to be rapidly communicated between regions of the cortex that are specialized for processing visual, auditory, and language information. The fact that reading depends on the integrity of the visual system does not imply that visual impairments are a common cause of reading difficulties.

Aural music training for dyslexics