Document Type : Original Articles

Authors

• Mostafa Daemi ¹
• Bijan Shafiei ²
• Mohammad Saadat Nia ³

¹ MSc, Student of Speech and Language Pathology, Speech Therapy, Department of Rehabilitation, School of Isfahan University of Medical Sciences, Isfahan, Iran

² MSc in Speech and Language Pathology, Member of Speech Therapy Department of Rehabilitation, School of Isfahan University of Medical Sciences, Isfahan, Iran

³ Neurologist, Isfahan Medical University, Affiliated Hospital of Alzahra, Isfahan, Iran

Abstract

Introduction: Dyslexia can be defined as a reading and writing disorder without any intellectual, educational or emotional problems. Despite of its detrimental effects on various aspects of dyslexics’ individual and social living, no well-defined etiology or biologic diagnosis has been found to date. The purpose of this study was to compare amplitudes and latencies of P100 component of VEP results between dyslexics and non-dyslexic through various visual stimuli to evaluate its diagnostic value.Materials and Methods: It was a cross-sectional analytic study. 20 dyslexics and 20 non-dyslexic schoolaged children were randomly recruited. All of them were first tested by VEP and then the amplitudes and latencies of P100 component obtained through low and high contrast visual stimulation were recorded and analyzed.Results: Reduction of stimulation contrast resulted in a significant increasing of P100 latency in both groups. Although reduced stimulation contrast resulted in decreased and increased amplitudes in nondyslexics and dyslexics respectively, none of these changes were significant when two groups were compared.Conclusion: Resulted changes in P100 amplitude and latency by reduced stimulation contras through VEP recording is not a suitable indicator for dyslexia diagnosis. This research did not support mangocellular deficit hypothesis in dyslexia.Keywords: Dyslexia, VEP, magnocellular