Figure 1. Sequence task setup. (a) In 2x6 sequence task, a sequence of 12 key presses
is learned by trial and error, two at a time (called a ‘set’) in a series of six sets (called
a ‘hyperset’). The two key presses belonging to a set need to be executed within 3 sec
and after an appropriate delay the subsequent set is displayed. A new trial is started by
resetting the presentation of the hyperset to the beginning either upon an error in any
set or on successful completion of the entire hyperset. The bottom panel indicates the
correct order of key presses for the example shown in the top panel. (b) Normal and
Rotated settings for set 1 of the example are shown. In the normal setting the visual
display and keypad are arranged in the usual upright position and in the rotated
settings the display-to-keypad relationship was altered. In the visual setting, the
keypad was rotated by 180°, while the display remained unaltered. In the motor
setting both the keypad and the display on the screen were rotated by 180°.
Consequently, in the visual setting the sequence of visuo-spatial cues (visuo-spatial
sequence) remained identical, while in the motor setting the sequence of finger
movements (somato-motor sequence) remained the same as that of the normal setting.
Finger movements to be executed for an example are indicated by arrows in all the
settings in the lower panel. Six such sets constituted a hyperset as shown in panel a.
(c) Subjects performed two experiments - visual-normal and motor-normal. Each
experiment consisted of six sessions of which the first two and the last two
represented ' early' and ' late' stages of learning, respectively. We utilized an on-off
(box-car) design for the experiments. In every session, subjects alternated between
sequence learning tasks in the test blocks (N: normal and R: rotated) and followed
random visual cues in the control blocks (F: follow). The duration of the test block
was 36 sec and that of control block was 21 sec. 12 and 7 scans were acquired during
the test and control blocks, respectively. Scans identified in gray shade represent
instruction scans at the beginning and end of a block.