FMRI Brain Functional Imaging In Study Of Superior Memory

In earlier behavior studies on superior memorists, known as having the capability to memorize digit sequences in a rather short time or to recite a very large amount of digits after extensive practice, we acquired the knowledge that most of them have the mnemonics of not only converting randomized digits into codes with meaning for themselves but also used the various retrieval cues (i.e., Method of Loci) for later recall, as exemplified in the skilled memory theory and the framework of Long-Term Working Memory. To get more knowledge about the correlates of these mnemonics, some fMRI studies were manipulated to describe the distinctive neural areas for individuals who were found to report the application of various mnemonics or were trained on them.To locate the neural correlate of a specific mnemonic applied by superior memorists, the experimental condition aiming to induce only one mnemonic need to be deliberately designed. However, the difficulty would be existed to extract the effect of one mnemonic from the combination of memory strategies used by superior memorist on memorizing lists of items. The former study on one memorist, namely Chao Lu who is the current holder ofGuiness World Record for reciting67,890decimals of pi, found that he, after years of practice on memorizing digit sequences, use the mnemonic of imaging, namely automatically converting each of two-digit groups from00to99into an image. Excitingly, his normal performance on digit span task, in which Chao Lu reported he couldn’t use other mnemonics than imaging, provides an ideal opportunity to locate the neural correlates of this mnemonic.The objective of this research is to explore mechanisms differences of Chao Lv and control subjects in encoding and recall processes of memory via examination of functional MRI (fMRI), and to provide evidence for further understanding of the underlying neural mechanism related to superior memory. Chao Lv and thirteen female participated in and event-related design was adapted. Three kinds of materials, i.e.2-digits,1-digit, letters were used in this study. The fMRI scanning was performed while subjects conducted memory tasks. SPM2and SPSS13.0statistical software were used, respectively.The imaging data showed that right superior frontal gyrus (BA8), left middle frontal gyrus (BA6,11,46), bilateral inferior frontal gyrus (BA45,46,47), left superior temporal gyrus (BA22), bilateral middle temporal gyrus (BA21,39), left superior parietal lobule (BA7), bilateral precuneus (BA7,10) activity was associated with encoding phases in2-digit task; right superior frontal gyrus (BA10), bilateral middle frontal gyrus (BA9,10,11), right inferior frontal gyrus (BA45,47), right superior temporal gyrus (BA22,38), left inferior temporal gyrus (BA20), right precuneus (BA19)with recall phases in2-digit task; left superior frontal gyrus (BA8,10), bilateral middle frontal gyrus (BA6,9,10), right inferior frontal gyrus (BA10), left insula (BA13), right precuneus (BA19) with recall phases in1-digit task; right superior frontal gyrus (BA8), right middle frontal gyrus (BA10), left inferior frontal gyrus (BA45), right inferior parietal lobule (BA40) with recall phases in letter task.The present study demonstrated the changes in brain activation pattern associated with the use of the imaging method. Right superior frontal gyrus, left middle frontal gyrus, right inferior frontal gyras and right precuneus activities were associated with both the encoding and recall phases in2-digit task. These findings suggest that brain networks mediating encoding and retrieval vary with whether use of imaging method or not.