Review article
Efficacy of dynamic visuo-attentional interventions for reading in dyslexic and neurotypical children: A systematic review

https://doi.org/10.1016/j.neubiorev.2019.02.015Get rights and content

Highlights

  • Visuo-attentional interventions improve reading outcomes in dyslexic children.

  • Improvements are equal or greater than other options and last at least two months.

  • Visual perceptual trainings can benefit reading fluency and comprehension.

  • Visually-based reading acceleration programs can improve reading accuracy and rate.

  • Action video games can increase reading rate and fluency.

Abstract

Dyslexia is associated with phonological and visuo-attentional deficits. Phonological interventions improve word accuracy and letter-sound knowledge, but not reading fluency. This systematic review evaluated the effectiveness of dynamic computerized visuo-attentional interventions aimed at improving reading for dyslexic and neurotypical children aged 5–15. Literature searches in Medline, PsycINFO, EMBASE, Scopus, ERIC, PubMed, Web of Science, and Cochrane Library identified 1266 unique articles, of which 18 met inclusion criteria (620 participants; 91.40% dyslexic). Three types of visuo-attentional interventions were identified. Results show that visual perceptual training (n = 5) benefited reading fluency and comprehension, visually-based reading acceleration programs (n = 8) improved reading accuracy and rate, and action video games (n = 5) increased rate and fluency. Visuo-attentional interventions are effective options for treating childhood dyslexia, improving reading generally equal to or greater than other strategies. Initial evidence indicates that visuo-attentional interventions may be efficacious in different orthographies, and improve reading for at least two months after intervention. Larger sample interventions on a wider range of reading skills with follow-up assessment are needed to further clarify their effectiveness.

Introduction

Developmental Dyslexia (DD) is a neurodevelopmental disorder characterised by problems in learning to read and affects 10% of the population worldwide (American Psychiatric Association., 2013). Individuals with DD experience deficits in their ability to decode letters and sounds, and show impaired accuracy and word recognition, consequentially resulting in significant educational and occupational disadvantage throughout the lifespan (Lyon et al., 2003) despite adequate intelligence and education.

Substantial research over the last fifty years has demonstrated that deficits in reading are associated with both phonological processing (Snowling, 2001; Vellutino, 1979, 1987; Vellutino et al., 2004; Wagner and Torgesen, 1987; Wagner et al., 1994) and visuo-attentional mechanisms in children and adults with DD (Badcock et al., 2008; Barnard et al., 1996, 1998; Crewther et al., 1999; Facoetti and Molteni, 2001; Gori et al., 2016; Lovegrove et al., 1980; Lovegrove and Brown, 1978; Rutkowski et al., 2003; Stein, 2001, 2003, 2018; Stein et al., 1988; Stein and Walsh, 1997), highlighting that DD is a multifaceted, heterogeneous disorder (Menghini et al., 2010).

Since Vellutino (1979), remediation programs focusing on improving phonological processing, known to be one of the strongest predictors of word reading accuracy (Mann and Wimmer, 2002), have been frequently used. Although recent research indicates that such programs are ineffective in up to one third of children (Whiteley et al., 2007), and when successful, reading outcomes are often in terms of single word and pseudoword reading accuracy and letter-sound knowledge, rather than text reading fluency (i.e., the ability to read text rapidly, accurately, and with prosody) and comprehension (see meta-analyses by Bus, 1999; McArthur et al., 2012). Furthermore, these remediation strategies are resource-demanding, are more beneficial for those learning to read rather than more established readers, and typically reduce the degree of reading difficulty rather than normalize it (Gabrieli, 2009). More recent evidence from children with DD (aged 6–8 years) also shows that around 38–53% do not present with phonological deficits (O’Brien et al., 2012), necessitating investigations into alternate remediation options.

More recently, research in the area of reading remediation has shifted in emphasis to multiple investigations of non-phonological reading interventions which target visuo-attentional deficits and visuo-attentional mechanisms. Such remediation programs are based on literature showing that spatially and temporally dependent processes, such as dynamic visuo-attention, rapid naming/word recognition, and eye movements, are most predictive of reading rate and fluency (Al Dahhan et al., 2014; Elhassan et al., 2017, 2015; Franceschini et al., 2012; Georgiou et al., 2008; Poulsen et al., 2015). Thus, visuo-attentional interventions may address the limitations of current dyslexia interventions by targeting other reading skills, such as rate and fluency (e.g., Franceschini et al., 2013). Such remediation evidence would provide further validation that visuo-attentional deficits are contributing factors of DD (Facoetti et al., 2003; Franceschini et al., 2012, 2013; Gori et al., 2016). Therefore, a thorough review of the current state of research into these types of visuo-attentional interventions for reading is timely and necessary.

Research into DD has reliably identified impairments across visuo-attentional mechanisms. The orienting and focusing of visuospatial attention, often described as the ‘spotlight of attention’, is impaired in dyslexia and results in inefficiencies in selectively extracting and processing the spatial relationship of visual information from a specific region of space within the visual field (Facoetti et al., 2000b; Treisman, 1988). Such individuals demonstrate a more distributed/diffused mode of attention, and are impaired on tasks of focused spatial attention, visual search and visual (peripheral) cuing (Facoetti et al., 2003, 2000a; Facoetti et al., 2000b; Franceschini et al., 2012; Liu et al., 2018; Pammer et al., 2004; Vidyasagar and Pammer, 2010). Those with DD also demonstrate impairments in the rapid engagement of attention, referred to as ‘sluggish attentional shifting’, which results in abnormal temporal, crowding and lateral masking performances, and can be used to predict poor reading outcomes in young children (Facoetti et al., 2010; Franceschini et al., 2018; Hari and Renvall, 2001). Interestingly, considerable evidence indicates that deficits in temporal processing and attention shifting are not exclusive to the visual modality, but are found for transient auditory and cross-modal information (Auditory timing deficits are beyond the purpose of this review, but see Au and Lovegrove, 2001; Casini et al., 2018; Stein, 2018).

Individuals with DD, including pre-reading children at risk of DD, demonstrate deficits in visual motion perception. This results in reduced proficiency to infer the speed and direction of elements of visual stimuli on tasks such as motion coherence and direction discrimination (Albright and Stoner, 1995; Boets et al., 2011; Cornelissen et al., 1995; Gori and Facoetti, 2014; Gori et al., 2016; Kevan and Pammer, 2009; Mascheretti et al., 2018; Stein, 2014). Similarly, dyslexics show visual temporal processing impairments, displaying higher gap-detection thresholds to visual stimuli presented sequentially and rapidly (Au and Lovegrove, 2001; Martos and Marmolejo, 1993; Wang and Yang, 2018), longer visual persistence to low-spatial-frequency stimuli, such as measured by contrast sensitivity tasks (Slaghuis and Lovegrove, 1985), as well as slower recognition and correct visual sequencing of letters (Ozernov‐Palchik et al., 2017; Stein and Walsh, 1997). Inefficiencies in attentionally-driven eye movements are also often evident in those with DD during both reading and non-reading tasks (Al Dahhan et al., 2014, 2016; Biscaldi et al., 2000; Rayner et al., 2013; Stein and Fowler, 1981). Many dyslexic readers also experience visuoperceptual anomalies - displacing and inverting letters within a word, causing words to appear moving, distorted, crowded, or overlapping (Boets et al., 2007; Facoetti et al., 2003).

What is imperative to all these attentional mechanisms is the dynamic, transient processing of rapidly presented visual information. Unequivocally, when reading text one must sequentially, spatially and temporally select the word to be read; successively and rapidly moving the eye and the attentional spotlight (Laycock and Crewther, 2008). These processes are often linked to the faster subcortical magnocellular (M) stream that is responsive to high temporal and low spatial frequencies and responsible for stabilizing and directing eye movements, multisensory selective attention, and motion processing (Bruce et al., 1985; Stein, 2001, 2003, 2018; Stein and Walsh, 1997). Therefore, the deficits that those with DD show on these tasks are thought to be attributed to an underlying sensitivity weakness of the transient M system, specifically of the dorsal stream (Crewther et al., 1996; Gori and Facoetti, 2014; Laycock et al., 2012; Stein, 2001, 2018; Stein and Walsh, 1997; Vidyasagar and Pammer, 2010). In contrast, those with DD do not show impairments in static visuo-attention (Barnard et al., 1998; Hansen et al., 2001; Lovegrove et al., 1982). Thus not unexpectedly, past interventions that have focussed on static visuo-attention have not been effective (see Kavale, 1984).

In order for interventions to adequately remediate the dynamic visuo-attention impairments found in DD, maximal loading of spatial and/or temporal processing of visual information, appropriate to the ability of the individual, would be necessary. This would only be feasible through computerised delivery. In fact, there have been several recent reports on improving reading through the use of computerized visual programs that heavily engage spatial and/or temporal attention, including action video games and direction discrimination training, and these have demonstrated success (Franceschini et al., 2013; Lawton, 2004). Importantly, they are examples of active interventions (as opposed to passive interventions) that aim to achieve ongoing cognitive improvement. While existing visuo-attentional intervention studies appear to vary widely in terms of population age (i.e., pre-readers through to adults), the majority have focused on primary school aged children up to age 14 or 15 years (e.g., Facoetti et al., 2003; Gori et al., 2016; Lorusso et al., 2011). This age range is when intervention is potentially of greatest benefit as children are undergoing rapid neural and developmental periods and attention networks are still maturing (Crewther et al., 1996; Klaver et al., 2011; Kolb, 2009; Langrová et al., 2006; McIntosh et al., 2006). While a number of papers have reported on the usefulness of similar types of interventions for reading in unselected populations or other clinical populations (e.g., Dodick et al., 2017; Kirk et al., 2017), this review is specific to studies of dyslexic children compared to typically developing readers. This criterion was set to establish the role of visuo-attention and efficacy of its intervention in DD.

Thus, the objective of this systematic review is to evaluate the efficacy of active, computerized visuo-attentional interventions that do not include any direct phonological input on the reading of typical and dyslexic children aged 5–15 years. Five years is the age when formal education usually begins and when reading can start to be typically assessed and so it is appropriate to start there. Reporting of the systematic review followed PRISMA guidelines (see supplementary document Table S1 for PRISMA checklist; Moher et al., 2009). Table 1 provides a list of abbreviations used throughout the text of the review; those used in a specific table are identified below the table.

Section snippets

Search strategy

Prior to performing the review, a complete protocol was pre-specified and registered at PROSPERO (registration number CRD42017060282; Initial registration dated 27/03/2017; Peters et al., 2017).

Studies were identified through electronic database searching in Medline (Ovid, 1946 to present), PsycINFO (Ovid, 1806 to present), EMBASE (Ovid), and adapted for Scopus (Elsevier), ERIC (Proquest), PubMed, Web of Science (ISI), and Cochrane Library, for all available years. The final database search was

Risk of bias within studies

Risk of bias assessments for the non-randomised (ROBINS-I) and randomised (Cochrane Risk of Bias Assessment) interventions were conducted to ascertain if the studies satisfied the final inclusion criteria (exclusion reason 8) and determine the study quality in relation to the objective of the current review (see Table 2, Table 3). Two non-randomised studies displayed critical risk of bias in each of the ‘classification of interventions’, ‘deviations from intended interventions’ and ‘reported

Discussion

Out of 2288 records, 18 studies met the inclusion and risk of bias criteria for this review. The studies, while written in English, investigated reading outcomes across five languages, and included a heterogeneity of intervention durations, intervention intensity, comparison treatment groups and control groups, and reading outcomes. Quality of the included studies was generally fair, with non-randomised studies all assigned an overall moderate risk of bias (i.e., sound for a non-randomised

Conclusions

The results of this review show that visuo-attentional interventions for dyslexia, though brief, are able to produce significant reading gains, without the need for explicit phonological or orthographic instruction, and for VPT and AVGs, also without any reading component. The patterns of evidence show that VPT programs provide most benefit for reading fluency and comprehension, visually-based RAPs appear to improve reading accuracy and rate, while AVGS result in gains to reading rate and

Conflicts of interest

None.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Acknowledgements

The authors thank Mr Steven Chang for his assistance during the development of the search strategy and database searches, Dr Zena Elhassan and Ms Deena Ebaid for their insights and suggestions on an earlier draft of this manuscript, and Dr Melanie Murphy for her help with aspects of data extraction.

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