Oxygenation and blood concentration changes in human subject prefrontal activation by anagram solutions

Continued studies in cognitive function in problem solving of graded difficulties has now proceeded through several thousand tests of high school students in a six-week period last summer (2000). The optical imager used 9 sources and 23 detectors operated in time multiplex to give an image of the prefrontal region in several seconds. Thus, the image can be acquired in the state prior to activation, during and following activation. The images are acquired at two wavelengths, 750 and 850 nm, from which the changes of blood concentration (blood pooling) and relative oxygenation/deoxygenation state (metabolic activity) can be obtained and with suitable calibrations converted into micromolar changes of total Hb concentration and fractional oxygenation, respectively. The imager has a wearable pad applied to the forehead and the electronics now presents the running average of the two quantities mentioned above in the 16 voxels which cover the prefrontal region in 1 sec. Thus the protocol involves a scanning through anagrams of graded difficulty which are known to include the range of maximal activation (>3 solutions in the 30 sec test interval or are too easy (>10), or too difficult. Anagrams are presented in a sequence of three, four, five, etc. letter anagrams to the maximal level of difficulty and then back down again to the starting point. Each anagram is displayed for approximately one minute. Computer scanning of the results gives histograms of the several hundred tests per individual in the "training" interval (for three weeks) and in the post training interval about 400 tests, each for 4 levels of difficulty (3 weeks). Usually two or three complete trials per day were achieved with the result that the group of 7 students produced over 2600 test results in 2000. The histogram displays are under study to determine: a) the most fruitful voxels, b) the fraction of the total tests that appeared in those voxels, and c) the maximum signal level observed in the histogram display in units of micromolar hemoglobin. The product of these two was taken as the Figure of Merit and their displays of the 16 voxels gave patterns for trained and untrained responses. The preliminary conclusions of this study were: a) that the training effect was very large, pretraining exhibited a chaotic voxel distribution for all difficulty levels while trained students gave a higher output and activated only one or two of the 16 voxels. If the tests were too easy, too hard, i.e., an ability/difficulty mismatch, frustration or disattention gave similar chaotic patterns (7); b) a match between difficulty and ability activated only a few voxels in similar locations. Since attention and success measures appear to be of interest in school room studies, a wearable imager with local LCD display can be supplied to the Senior class of the local high school for those individuals who have already had last Summer's training in anagrams. A wearable NIR measurement of metabolic activation and blood flow may be a useful educational aid. In summary, the optical method focuses attention on cognition activated oxygenation of prefrontal cortex.