A Study Of Brain Functional Magnetic Resonance Imaging During Working Memory Tasks In Normal Adults

Working memory (WM) is an important cognitive function belonging to short-term memory. The information processing includes encoding, maintaining and recalling. All of the temporary information during complex cognitive tasks, such as language comprehension, learning, inference and calculation, need to store and process in working memory system. At present, WM is one of the hotspots in learning and memory studies. Functional magnetic resonance imaging (fMRI), being a new noninvasive technique associated with the three elements of function, image and anatomy, provides a new approach in working memory research. Studying human brain noninvasively using fMRI would be the focus in the area of cognitive neuroscience.ObjectiveTo study the feature of brain fMRI during a working memory task in normal adults.MethodsTen normal volunteers underwent fMRI examination while performing working memory tasks. The present experiment design involved in four tasks.The first task is number identify, the second, third and fourth tasks are simple addition of twosingle-digit numbers, according to the degree of difficulty increased gradually, which divided into three level of memory tasks. Each level memory task consists of five groups of addition formula. After topography collection, the data obtained are processed and analyzed by analysis of functional neuro images (AFNI). All of the averaged results obtained from the activated brain areas of the subjects were analyzed.Results1. Behavior resultsAll subjects finished tasks completely on demand. There were no significant differences in reaction time (RT) between male and female (p>0.05). The difference of correct rate between each two tasks has no statistically significant (p>0.05) in the subjects.2. fMRI resultsTwo voxels within 3mm connectivity distance are regarded as those in a same activation cluster. The cluster area must be bigger than 500mm3, or else will be discarded. First taskWhen discern numbers, following brain cortical areas can be found significant activation: inferior parietal lobules, cingulate gyrus, lingua gyrus, superior and middle temporal gyrus, superior and inferior frontal in right hemisphere;and precuneus, postcentral gyrus, precentral gyrus, middle occipital gyrus in left hemisphere. It can be found that bilateral middle frontal gyri were activated. Second taskIn the working memory task of one addition formula, the major brain activated areas below can be found: right anterior cingulate gyrus, left superior and middle temporal gyri, left superior and middle frontal gyri and bilateral middle occipital gyri.Third taskIn the working memory task of two addition formula, it mainly can be found that following cortical areas are activated: left inferior parietal lobe, left frontal gyrus, left precentral gyms, inferior occipital gyrus in both hemisphere. Fourth taskIn the working memory task of three addition formula, we can find that these cortical areas are activated: left middle frontal gyrus, cuneus, precentral gyrus. ConclusionMiddle frontal gyrus is relative with working memory task, parietal lobe take part in working memory too. The role of superior frontal and interior frontal gyri in memory needed to be studied furthermore.By the increasing of memory load, less and less brain cortical areas were activated in normal adults can be observed and the areas were smaller and smaller. The tendency of activation is centralization.