Hemispheric asymmetry in memory for pictorial semantics in normal subjects

Effects of presence versus absence of semantic organization in pictorial scenes were investigated in a memory hemi-field tachistoscopic paradigm in order to assess the hemispheric status of long-term semantic memory (LTSM). Forty normal subjects were asked to remember a series of pictorial scenes which were organized either in common configurations or were unorganized with respect to real-world configurations. Memory for these scenes was measured by hemi-field presentations of detail probes and whole scene probes. The results showed that there were no differences between the two visual fields in accuracy scores. Latency of positive responses showed that memory for the common/organized scenes was better in the left (LVF) than in the right visual field (RVF) and a dissociation between the two types of pictorial organization was present only in the LVF, with the slower latencies for unorganized scenes. The effect of probe-type was also different in the two visual fields: detail and whole scene probes were undifferentiated within the LVF but were differentiated in the RVF, with whole scenes remembered more quickly. The findings are discussed in terms of asymmetries in storage/retrieval of schemata in LTSM.