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Poster P3

Friday stream 1-4 Session 16.10 - 17.25 Length 25 minutes

Hemispheric stimulation by computer for pupils with Dyslexia

Jean Robertson and Mike Johnson

Institute of Education, Manchester Metropolitan University J.Robertson@mmu.ac.uk

Abstract

This paper describes a small-scale computer mediated intervention with secondary school pupils who had been assessed as being dyslexic. The intervention was based on the framework of the neuropsychological theory and intervention developed by Bakker (1990, 1994 & 1998) to address the literacy needs of dyslexic subjects. The background to the work is the Balance Model of reading (Bakker 1990) which suggests that initial reading is primarily mediated by the right hemisphere (specialist for visual spatial function) and advanced reading by the left hemisphere (usually specialist for language). This normal developmental process was demonstrated by ERP studies (Bakker et al 1980). The balance of hemispheric activity transfers from the right to the left hemisphere when alphabetic symbols become familiar. If this process is interrupted two subtypes of dyslexia result: the P-type (perceptual) and the L-type (linguistic). The former is arrested at the visual perceptual stage and the latter has transferred prematurely to the linguistic stage. Differentiated intervention (Hemisphere Specific Stimulation {HSS}) can aid both subtypes. Intervention was delivered by a specially adapted computer programme (HEMSTIM) which uses a central fixation point and flashes words either to the left visual field to stimulate the right cerebral hemisphere or the right visual field to stimulate the left cerebral hemisphere. The experiment delivered both types of intervention to 18 pupils over 20 weeks. Whilst somewhat variable the results suggested confirmation of the theory and that stimulation of each cerebral hemisphere has differential effects on reading performance.

THEORETICAL BACKGROUND

The background to the research rests on the assumption that the brain responds directly to stimulation. Specific intervention can lead to measurable changes in brain functioning.
The Balance Model of reading describes one model of reading development linked to knowledge of the respective functions of the two cerebral hemispheres. Early reading is mediated mainly by the right hemisphere, which is specialist for form and direction. When perceptual differences are consolidated the balance of brain activity can transfer to the left cerebral hemisphere, as reading is a linguistic activity. If this normal process does not occur two sub-types of dyslexia can result.

THE SUB-TYPES

The P-type (perceptual) uses right hemisphere strategies inappropriately.

The L-Type (linguistic) uses left hemisphere strategies inappropriately.

READING BEHAVIOUR

The P-type pupil remains sensitive to the perceptual features of the text. Reading is slow with much hesitation and evidence of excessive reliance on explicit grapheme-phoneme decoding. Errors impact on time and fluency (fragmentation errors). In contrast the L-type pupil reads quickly and ignores the surface features of the text. Many reading errors (substantive errors) are produced and there is inappropriate use of linguistic strategies.

SAMPLE SELECTION

All subjects in the sample:

• Had been assessed by an educational psychologist as dyslexic
• Had English as a first language and were right handed
• Were in receipt of individual specialist support lessons
• Attended a mainstream secondary school

CLASSIFICATION PROCEDURE

Following administration of the Neale Analysis of Reading Ability (NARA) errors were categorised according to the Bakker categories as substantive (real errors) or fragmentation (fluency). Pupils were then assigned to sub-type categories.

SAMPLE BREAKDOWN

Sample by gender, year and Bakker 'Sub-type'

DESIGN OF THE EXPERIMENT

Pupil sub-type category was not revealed to either the researchers or the teachers. Each pupil was allocated a number and the key retained by the tester. Testing took place three times, pre intervention for baseline data and after both the first and the second experimental periods. Pupils were split into two experimental groups by the researchers and each group was treated with either P-type or L-type stimulus material twice a week for five weeks. The stimulus material was then reversed. Thus each pupil received both theoretically "appropriate" and theoretically "inappropriate" stimulation from an assistant researcher.

INTERVENTION

Hemisphere Specific Stimulation (HSS) was delivered by computer using the visual half-fields. This is via a specially designed program (HEMSTIM) and can deliver stimulation directly to either the right cerebral hemisphere for L-types or the left cerebral hemisphere for P-types. Following fixation at a central point on the computer screen words are flashed for less than 300 milliseconds either in the left visual field (L-types) or the right visual field (P-types). All words were at the independent reading level of the pupil.

RESULTS

Results by Type of Stimulation

P-type = Perceptual -sub-type

L-type = Linguistic sub-type

Comp. = NARA comprehension

Results varied across individuals and variables but educationally significant results were found for certain pupils. In terms of the intervention the pupils received the following results were found: L-type materials for the first five week phase resulted in gains in reading accuracy (range 1 year 3 months to 4 years 2 months). Gains in comprehension ranged from 2 years to 3 years 4 months. Results for rate of reading were inconsistent.

• P-type materials for the first five week phase resulted in gains in accuracy from 1 year 2 months to 2 years. Gains in comprehension ranged from 9 months to 2 years 3 month. Reading rate changes for this group were consistent as all gained in speed of reading.

Results for the second intervention period revealed a different pattern to the first and were less consistent across the three variables.

DISCUSSION

The literature supports the hypothesis that L-type materials impact on reading accuracy and P-type materials on fluency.

CONCLUSIONS

• Results did not support the classification but did support the differentiated outcomes obtained from the L- and P-type materials over a short period of time (10 weeks in total).
• Pupils treated with the L-type materials made greater gains in reading accuracy when receiving stimulation of the right cerebral hemisphere. Reading speed decreased which may indicate increased perceptual care.
• Pupils treated with the P-type materials showed more consistent increases in rate of reading. Explicit decoding became less of a feature of reading style. The speed of delivery of material may have increased their ability to respond directly to text.
• The results overall did support the use of hemisphere specific stimulation as a suitable intervention method for some dyslexic pupils with entrenched reading difficulties.
• Further research is required to refine classification methods and to allow more detailed pupil/material interactions to be revealed.