DISTURBANCES IN TIME-LIMITED STORAGE OF SENSORY INFORMATION AFTER RIGHT TEMPORAL LOBECTOMY

Our previous study performed on subjects with no brain damage suggeste d that processes involved in the storage of sensory information are la teralized to the right hemisphere. The present research aimed at verif ying this hypothesis by studying the effect of unilateral temporal lob e lesion on performance in a sensory information storage test. Sevente en 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 wi th no brain damage were tested. The subjects were presented with geome trical 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) inter stimulus intervals (ISI). The task of the subjects was to judge whethe r the second stimulus was the same as, smaller or bigger than the firs t one. The first stimulus in each pair was exposed unilaterally, rando mly in the left (LVF) or right (RVF) visual field, and the second one in the centre of the screen. In short ISI condition the RH-damaged gro up performed worse than both the control group and the LH-damaged grou p. In long ISI condition the PH-damaged group did not differ from the controls. On the contrary the LH-damaged group did not differ signific antly from the controls in any ISI condition. The results show that te mporal lobe structures are involved in time Limited storage of sensory information. Moreover, they provide further evidence for the right-he mispheric locus of this storage.