Figure 5.

Design and results of an fMRI study of working memory for faces (61). (Upper) Design of the task. For each series of fMRI scans, subjects performed 3½ baseline-activation task cycles, each consisting of two sensorimotor control trials followed by two working memory trials. During the memory task, subjects saw a picture of a face, a delay, and then another picture of a face. Subjects were asked to hold an image of the first face in mind during the delay and to respond with a left or right button press to indicate whether the second face matched the first. During the control task, subjects simply looked at the scrambled pictures and then pressed both buttons when the second scrambled picture appeared. Three time series are shown that represent the different cognitive components of the task: a transient, nonselective response to visual stimuli; a transient, selective response to faces; and sustained activity during memory delays. These time series (smoothed and delayed by convolution with a model of the hemodynamic response) were used as regressors in a multiple regression analysis of the time course of activation in each area. (Lower) Results from a single subject overlaid onto that subject’s anatomical images. Activations are color-coded according to the relative sizes of the three regression coefficients described above. Areas that responded transiently and nonselectively to any visual stimulus, such as posterior occipital cortex (a), are shown in green. Areas that responded transiently and showed a selective response to faces over scrambled faces, such as fusiform gyrus (b), are shown in blue. Areas that showed sustained activation during the memory delay after the stimulus was removed from view, such as inferior frontal cortex (c), are shown in red. Areas that showed a combination of these types of responses are shown in a blend of colors. (From ref. 87.)