Lateralisation of language functioning by the Wada procedure and divided visual field presentation of a verbal task

In cases of intractable epilepsy, language and memory functioning in the hemisphere contralateral to the lesion is determined prior to unilateral temporal surgery. Patients with unilateral temporal lobe lesions were assessed using the intracarotid sodium amytal (Wada) procedure to determine the lateralisation of language and memory functioning. They also performed a divided visual field task in which letters were presented in pairs for brief durations on a computer screen in a phonemic matching task. The results showed only moderate agreement between the two methods with regard to identification of the speech-dominant hemisphere, indicating the divided visual field matching paradigm to be unsuitable as a basis for surgical decision-making.