Abstract:

Priming for new associations, also called associative priming, refers to the implicit memory for newly formed associations between different stimuli or the features. By now, there are still many unsolved issues on associative priming. This dissertation used cognitive neuroscience approach that combines the study of cognitive psychology, near-infrared spectroscopy (NIRS) and neuropsychology to investigate associative priming effects and its brain mechanisms systematically. The priming tasks used in this dissertation were process dissociation paradigm, perceptual identification task and speeded naming task. The experiments on normal subjects showed both level of processing and unitization affected associative priming effects, which was different from other kinds of implicit memory (such as item priming, supported by perceptual representation system). However, when the associative strength was strong enough, subjects could manifest associative priming effects even under shallow encoding conditions. NIRS study showed the activation of both sides of prefrontal lobe under deep encoding conditions was stronger than under shallow condition when subjects encoded unrelated word pairs. It suggested prefrontal lobe participate in memory for new associations. Furthermore, medial temporal lobe (MTL) and frontal lobe lesioned patients were tested using methods of perceptual identification task and speeded naming task. Both brain regions participated in associative priming. MTL mediated unitization between unrelated items. Frontal lobe contributed to priming for new associations by elaborative processing, inhibiting irrelevant information and selective attending to tasks. In addition, normal subjects needed to be aware of the relationship between study and test to form associative priming and densely memory deficit patients could not form memory for new associations. In conclusion, this dissertation demonstrated that associative priming needs the interaction between perceptual representation system and other memory systems. Both MTL and frontal lobe played important roles in priming for new associations, but with different mechanisms; and there were some relations between associative priming and conscious retrieval processing.

Key words: priming, new associations, memory, medial temporal lobe, frontal lobe