Functional Transcranial Doppler Ultrasound for High Temporal Resolution Measurement of Lateralization in Visual Memory and Visual Search Cognitive Tasks

摘要

Functional transcranial Doppler ultrasound (fTCD) is a noninvasive sensing modality that measures blood flow velocities in cerebral arteries (CBFV) with high temporal resolution. Few studies have examined the relationship of CBFV change during visual search and visual memory cognitive tasks. Here a protocol to compare lateralization between these two similar tasks using fTCD is demonstrated. Thirteen healthy volunteers were shown visual scenes on a computer and performed visual search and visual memory tasks while CBFV in the bilateral middle cerebral arteries was monitored with fTCD. Each subject completed 40 trials, consisting of baseline, calibration, instruction, and task periods. Lateralization was computed for each trial by subtracting the percent increase in CBFV on the right side from that on the left side. Results showed significant lateralization of both tasks, with memory reaching left lateralization of 1.3 percent, and search reaching right lateralization of 0.5 percent, agreeing with the hypothesis that memory is more left lateralized and search is more right lateralized. The protocol is straightforward and the equipment inexpensive, introducing a low-cost, high temporal resolution technique to further study lateralization of the brain.