There is a dedicated brain area for acquiring oral language but not for written language (i.e. reading). The reading circuit consists of neural systems that support every level of language and includes visual and orthographic processes, working memory, attention, motor movements and higher-level comprehension and cognition. Each component works smoothly with accuracy and speed as reading develops automaticity (i.e. making reading more automatic).

Fluency (i.e. fluent comprehension) refers to a manner of reading in which all sublexical units, words and connected text and all the perceptual, linguistic and cognitive processes involved in each level are processed accurately and automatically so that sufficient time and resources can be allocated to comprehension and deeper thought. This means that reading needs to be both accurate and automatic.

Rapid automatized naming (RAN) refers to a mini-circuit of the later-developing reading circuitry. RAN tasks include naming a series of familiar items as quickly as possible and this requires the reading circuit and can thus be used to assess reading fluency. RAN tasks depend on automaticity within and across each individual component in the naming circuit. It is a universal process that predict the young child’s later ability to connect and automize whole sequences of letters and words with their linguistic information regardless of writing system. RAN may be predictive of later reading because it includes the ability to automate both the individual linguistic and perceptual components and the connections among them in visually presented serial tasks. RAN latencies are related to how automized the naming process is.

Reading difficulties can be developmental (e.g. dyslexia) and acquired (e.g. alexia). The core deficit in alexia includes a disconnection between the visual and verbal processes in the brain.

Phonological awareness refers to the explicit ability to identify and manipulate the sound units that comprise words. Deficits in phonological awareness is a core deficit in dyslexia. Reading development depends on the explicit awareness of the sounds of the language and young readers need to learn to match the phonemes of speech with the graphemes that represent them in print. However, a deficit in phonological awareness is not the sole cause of dyslexia and children with intact phonological awareness may be identified less often as having dyslexia. They will also be less likely to benefit from instruction focused on improving phonological awareness.

The double deficits hypothesis (DDH) states that children can be characterized in subgroups according on their performances on each set of processes (e.g. phonological awareness; RAN).RAN deficits indicate weakness in underlying fluency-related processes. Children with a double deficit (i.e. phonological awareness and RAN) are the most impaired readers. There should be a multidimensional approach to dyslexia and reading difficulties as there is not one underlying cause.

A task can be characterized as a RAN task if it involves timed naming of familiar stimuli presented repeatedly in random order. The time taken to name items is believed to be key. The tasks typically involve naming of objects, colours, numbers and letters. The rapid automized naming-rapid alternating stimulus (RAN-RAS) and comprehensive test of phonological processing (CTOPP) are two often used RAN tasks. The RAN-RAS treats rapid naming as a cognitive ability that includes phonology and other processes. The CTOPP holds that rapid naming is a subcomponent of phonological awareness.

There are seven processes involved in rapid naming:

1. Attentional processes to the stimulus.
2. Bi-hemispheric visual processes responsible for initial feature detection (1), visual discrimination (2) and pattern identification (3).
3. Integration of visual features and pattern information with stored orthographic representations.
4. Integration of visual and orthographic information with stored phonological representations.
5. Access and retrieval of phonological labels.
6. Activation and integration of semantic and conceptual information with all other input.
7. Motoric activation leading to articulation.

Pause and articulation times are predictive of reading performance in later life rather than articulation time. A RAN task is different from single-item naming as serial naming has more cognitive demands. It is similar to a Stroop task but the RAN task is more predictive of later reading performance as it takes away the extra executive function demands of the Stroop task. General processing speed does not account for the relationship between performance on the RAN task and reading.

RAN may be part of a larger phonological construct as rapid naming tasks depend on the retrieval of phonological codes. However, that a RAN task makes use of phonology does not mean that it is part of it. RAN and phonological processing are not strongly related (1), they both account for unique variance in reading ability (2) and there are different biological and genetic bases for RAN and PA abilities (3).

Five and six year olds name colour and object stimuli more quickly than letters and numbers as they are still learning this. RAN-reading relationships are stronger in poor than in typical readers.

Predicting dyslexia in kindergarteners is inadequate and measures lack specificity and sensitivity. However, RAN is still one of the best predictors of later reading abilities. Second-grade RAN scores predict eight-grade reading and spelling scores and the predictive value is higher for poor readers compared to typical readers. The relationship between RAN and reading is strong and lasting but only for poor readers. RAN appears to predict reading ability in later life (e.g. adolescence) as well although this relationship is debated.

Alphabetic languages can be considered as falling along a continuum based on the complexity of the mapping between phonology and orthography. There is an opaque orthography when the correspondence between phonemes to graphemes are not consistent. A transparent orthography have a high correspondence between phonemes (i.e. sounds) to graphemes (i.e. letters). A transparent orthography allows for more straightforward learning of sound-to-letter correspondence and decoding. PA is important early in reading acquisition but when children reach their max in their ability to decode words accurately, the relationship between RAN and reading becomes stronger. The orthographic depth of the language dictates when this shift from reliance on phonology to fluency-related skills occur. The relationship between PA and reading ability depends on orthographic complexity but the relationship between RAN and reading ability are consistent across languages.

Phonological encoding plays a more minor role in reading in non-alphabetic languages as phonemes and graphemes are essentially unrelated in these languages. In these languages, deficits in phonological awareness are a poor predictor of reading difficulties but RAN is a good predictor.

Brain activation for reading-related tasks are found in the inferior frontal gyrus (1), temporoparietal area (2) and the occipitotemporal area (3). These are association areas which are responsible for the integration of information across visual and auditory modalities. The occipitotemporal area is associated with orthographic processing.

In people with dyslexia, there typically is hypoactivation of left temporoparietal and left occipitotemporal areas. This deficit is associated with dyslexia and not with absolute reading ability. Right frontal and temporal lobes show greater activation in people with dyslexia compared to controls and this may be a compensatory mechanism (i.e. effortful processing). When the automaticity of normal reading is disrupted, activation in reading-related regions changes. Readers with dyslexia employ a more distributed network that may represent compensatory mechanisms for performing RAN tasks.

People with dyslexia show later peak responses (i.e. ERP) for different components of reading performance. The peak of each of the ERP components involved in rapid naming is delayed in people with dyslexia. The mismatch negativity response (MMN) is a preattentive response to a difference within a series of auditory stimuli. This is a predictor of reading outcomes. This response is associated with RAN but not with PA. MMN may reflect processes important for the rapid processing of stimuli necessary for fluent reading.

People with dyslexia have smaller volumes of the pars triangularis area of the IFG bilaterally and an area of the right cerebellum. Extreme asymmetry of the planum temporale in either direction may induce risk for dyslexia. The extent and quality of white matter pathways may be important for RAN. Heritability of dyslexia is between 0.3 and 0.7.

RAN tasks can be used as a part of clinical assessment to identify risk for reading and learning difficulties and as a measure of the development and efficiency of processes related to word retrieval and reading fluency. RAN appears to be untrainable. However, fluency can be improved by using repeated reading (i.e. reading a passage multiple times with increasing speed). A multi-componential intervention may be most effective .