Disturbances in time limited storage sensory information after right temporal lobectomy

Our previous study performed on subjects with no brain damage suggested that processes involved in the storage of sensory information are lateralized to the right hemisphere. The present research aimed at verifying this hypothesis by studying the effect of unilateral temporal lobe lesion on performance in a sensory information storage test. Seventeen patients who had undergone a unilateral temporal lobectomy for the relief of intractable epilepsy (8 subjects--left hemisphere damage, 9 subjects--right hemisphere damage) and 11 normal control subjects with no brain damage were tested. The subjects were presented with geometrical Vanderplas type figures exposed in pairs, each for 100 ms, one after another, with short (50 ms and 500 ms) and long (3,000 ms) interstimulus intervals (ISI). The task of the subjects was to judge whether the second stimulus was the same as, smaller or bigger than the first one. The first stimulus in each pair was exposed unilaterally, randomly in the left (LVF) or right (RVF) visual field, and the second one in the centre of the screen. In short ISI conditions the RH-damaged group performed worse than both the control group and the LH-damaged group. In long ISI conditions the RH-damaged group did not differ from the controls. On the contrary the LH-damaged group did not differ significantly from the controls in any ISI condition. The results show that temporal lobe structures are involved in time limited storage of sensory information. Moreover, they provide further evidence for the right-hemispheric locus of this storage.