Dyslexia: What can Neuropsychology Tell Us about Spelling and Writing?

The relationship between spelling and writing needs to be clarified, and a good place to begin is with the distinction between spelling and writing in neuropsychology. Why neuropsychology? Neuropsychological bases relate to the functional differences between spelling and writing in different regions of the brain. Therefore, the connection between spelling and writing in the context of neuropsychology becomes quite important.

There is no doubt that spelling and writing are different because the functional organizations of spelling and writing are not only separate but also located in different parts of the brain. To understand the distinction between spelling and writing, let us first begin by thinking of spelling as related to the reading process.

There are at least two different opinions regarding the relationship between spelling and speech. One suggests that there is a separate brain area for motor skills related to writing. This is true. The selective impairment of spelling skills without any impairment of writing skills is now well established. The second opinion is that the disorder of spelling is similar to that of reading. Children can read by sound, which is phonological coding, or by sight, which is reading a word as a whole without sounding it out.

In spelling there are three different ways of conceptualizing the main processes, two of which correspond to the processes used for reading. Spelling by sound corresponds to phonological coding and vocabulary-based spelling corresponds to sight reading or “direct visual access”. These two have been distinguished in neurologically impaired patients as well. Some patients show an inability for spelling-by-sound even as their ability for vocabulary-based spelling is intact, while in others the abilities are reversed.

However, there is a third kind of spelling disorder called spelling assembly, which is the inability to put letters in the right sequence while spelling. Even though the person may be able to spell phonologically and by direct visual access, the sequencing of letters can be especially impaired. The patients make errors in the order of letters and with letter substitution, and these mostly occur in the middle part of the word. This is to be expected as sequencing or successive processing is involved in serial learning. Words in the middle part of the list are the least remembered as compared to those at the beginning or at the end.

Thus, there are three ways of looking at spelling if we consider spelling and writing together. The three different aspects of spelling just described would be reflected differently in writing. As mentioned earlier, we could conceptualize the whole process of spelling as similar to the process of word recognition. Let us go through it step by step: a target word could be spelled from vocabulary or from sound.

Whatever method is used, the spelling has to be assembled, and therein might be a difficulty in writing the letters sequentially. But writing is only one of the output modes. Assembling is, in itself, a cognitive function leading to written output, oral output, or a computer or typing output (for a detailed discussion, see McCarthy and Warrington, 1990).

The Movements in Writing

The motor activity of writing is a specific kind of voluntary movement. Children or adults who have difficulty in fine and gross motor coordination would also have difficulty in writing. However, this does not always happen. A person may not be able to imitate certain kinds of movements, gestures, and so on, but, nevertheless, their writing ability could be intact. The execution part in writing, as discussed before, is transcription. Therefore, it depends on an intact motor pattern for producing letters.

If writing is a reflection of the motor activity, then we could see difficulties in at least two distinct procedures. One is the “letter form” selection, that is, the organization of movements that are necessary to write the letters of the alphabet and connect them in a word. Children who have this kind of difficulty may not be able to take dictation at all, or may have problems in simply converting a word or a sentence written in block capitals to handwriting.

Crowding and spacing are the other problems. Writing is crowded on one side of the page leaving an excessively wide margin, or extra strokes are added while writing such letters as m, n, and u. Spacing errors are best described as leaving big gaps between the letters of a word.

In terms of brain anatomy, writing disorders are very difficult to localize because they could be caused by many different factors as we discussed. Neuropsychologists believe that writing is a specific form of motor activity that can be separated from a general deterioration of voluntary movements found in some people (McCarthy and Warrington, 1990). Many believe that the act of writing may be drawing upon a specific set of motor patterns that are stored in the brain.

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