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= Attention in Dyslexia =

Dyslexia
Dyslexia is a literacy disorder described as a ‘specific reading disability with a neurological origin’. It has cognitive causes characterised by difficulties in reading fluency, poor spelling, difficulties in accurate word definition and poor decoding and encoding words. decoding and encoding words. Other cognitive abilities are otherwise normal including motivation, sensory abilities, intelligence, and instruction.

Attention
Attention is the behavioural and cognitive process of concentrating and selecting specific environmental information whilst filtering out other unwanted stimuli. It concerns sustaining, managing, and shifting attention.

Co-morbidity
The co-morbidity of dyslexia and attention-deficit/hyperactivity disorder (ADHD) is frequently observed in the same individual. These disorders co-occur more often than would be expected by chance. This provides evidence that attentional mechanisms are necessary for reading alongside studies emphasising ADHD and dyslexia co-morbidity.

Individuals with dyslexia and ADHD have difficulty paying attention due to the demanding nature of reading limiting their concentration span. Both have difficulties writing including spelling, grammar, proofreading, handwriting and organisation. They are also both dysfluent readers with dyslexics having poor accuracy and misreading words. People with ADHD tend to skip over punctuation, leave of endings and loose their place.

Neurobiology
No specific area of the brain is universally accepted as responsible for reading or attention. However, shared biological processes underlying ADHD and dyslexia have been shown which may explain the high co-morbidity of the disorders. There is evidence for a risk of deficits in processing speed, executive functioning, inhibition, and sustained attention at a neuropsychological level in both dyslexia and ADHD. Structurally, abnormalities of brain function have been seen in dyslexics and ADHD including the basal ganglia, parietal cortex, parieto-temporal regions, prefrontal-cingulate cortex, and the corpus collosum. Prefrontal and posterior parietal cortices are important brain structures for attention. The posterior parietal cortices may play a role in spatial selection which is used for orienting attention in auditory and visual processing. Also, they have close connection with the cerebellum suggesting the cerebellum is involved in attention. A Cerebro-cellular circuit deficit has been seen in ADHD.

Attention in Reading
There is an increased consideration in the overlap between literacy/reading skills and attention. Reading is a complex skill where the journey of transforming written patterns into meaning involves several stages of processing. Recent studies suggest attentional mechanisms play a causal role in dyslexia/reading difficulties. For example, difficulties have been shown in maintaining attentional focus, orienting attention  and shifting attention.

Theory of Automatic Information Processing
LaBerge and Samuels’ theory of automatic information processing has been used for decades to explain reading. It has been highly influential and one of the most dominant theories of reading because it explains how reading fluency develops. Their theory suggests two main components of reading fluency: accurate word decoding and automaticity in word recognition. Automatic reading is achieved by processing through stages: (a) the inaccurate stage where recognising words is difficult; (b) the accuracy stage where words are recognised but attention is required to progress to the final stage; (c) the automatic stage where words are recognised without attention.

Attention is central to processing the information at each stage because of the presumption that the working memory has limited attention for cognitive tasks, including reading. As the working memory capacity is limited, successfully acquiring these components allows reading fluency as well as freeing memory and attention for higher subskills such as semantics and comprehension of text.

Peterson and Posner's Networks of Visual Attention
Visual attention is the process of selecting a target stimulus amongst competing stimuli. This is a basic, essential skill for reading acquisition allowing for atomicity of reading. Literature suggests a deficit in visual attention plays an important role in dyslexics reading difficulties. Deficits have been seen in visual temporal processing, perception, and attentional engagement. Visual attention abilities are predictive of reading abilities in the pre-reading stage. Evidence for a visuospatial attention impairment in dyslexics has been shown in visual exploration tasks.

In order to assess visual attentional processes, Posner proposed three independent but related networks of visual attention that attention depends on:

1) Orienting system is the ability to select sensory information by shifting and reducing attentional focus

2) Alerting system is preparing and maintaining readiness to detect a stimulus

3) Executive system is the ability to decide a stimulus relevance to task requirements and to suppress conflicting or irrelevant information.

It is unclear if dyslexics have an overall attention impairment or if it is a more specific deficit. Many studies suggest specific attentional deficits in dyslexia, however there is debate to where it is specific to. Buchholz and Davies suggest dyslexics perform poorly on executive and orienting systems, but not the alerting. Marzocchi et al found dyslexics perform poorly on executive attention but not alerting or orienting. Also, Buchholz and Davies found deficits in orienting and executive attention but nor alerting. Orienting attention deficit appears to have the most supporting evidence and alerting the least.

Executive attention
Gooch, Hulme, Nash and Snowing have found difficulties of executive functions co-occur with language impairments affecting reading acquisition. Executive attention is a crucial cognitive function for selecting relevant and ignoring irrelevant inhibiting distractors. Studies have shown that dyslexics are poor at this.

This is often studied using the Stroop experimental paradigm. This requires participants to view a list of words that do not match its meaning e.g. the word yellow in the colour green (see figure below) and read it as accurately and quickly as possible. This task presents participants with conflicting information (e.g. the colour of the word does not match the word they are reading) requiring the participant to select the desired stimuli as quickly and accurately as possible whilst filtering out unwanted stimuli. Studies have found that dyslexics have a slower response time than controls; this is due to the interference of conflicting stimuli and dyslexics struggling with the automaticity of reading. Dyslexics struggle to select the relevant stimulus to the task and struggle to ignore the conflicting information. This suggests dyslexics experience greater interference than non-dyslexics thus, suggesting a deficit in executive attention function.



Orienting Attention
Visual attention is sustained by the orienting network. The orienting network consists of the dorsal attention and ventral attention networks allowing for attention shifting and prioritising the most important sensory information.

Orienting attention deficit is typically investigated using aspatial cueing experiments consistently finding an orienting attention deficit in dyslexic readers. For example, Facoetti et al measured automatic orienting of spatial attention of both auditory and visual attention in dyslexics and non-dyslexic children using an aspatial cueing task. Participants were required to focus their visual attention on a cross in the centre of the screen. Eye movement was monitored to measure covert orienting (shifting attention without eye or head movement). A stimulus appeared on the screen (spatial cue); followed by a target stimulus. The target stimuli appeared either in the same place as the spatial cue (a valid trial) or in a different place (an invalid cue). Valid cues require attentional facilitation whereas invalid cues involve attention inhibition. Participants were instructed to respond as quickly as possible to the target stimuli by pressing the space key. Reaction time and accuracy was measured.

Findings show dyslexics had significantly longer reaction times than normal readers in invalid and valid cues. Auditory deficits may be due to an inability to rapidly shift auditory attention to properly discriminate sound features. Dyslexics showed a deficit in the ability to inhibit irrelevant information. Therefore, automatic orienting of auditory and visual attention is defective in dyslexics with both attentional facilitation and inhibition being impaired. Due to attention being important for selecting competing information by facilitating spatial selection, these findings can suggest children with dyslexia have a spatial deficit in orienting of auditory and visual information. Reading difficulties may be due to sluggish orienting of attention.