Proefschrift_Holstein

Reward modulation of cognitive function: aging

TRIAL 1 (discarded)

TRIAL 2 low reward task switch

TRIAL 3 low reward task repeat

TRIAL 4 high reward task switch

reward cue

15 cent

1 cent

1 cent

15 cent

RC interval

task cue

word

arrow

arrow

word

CT interval

target

le

right

le

le

response

correct! 15 cent le

incorrect! 0 cent right

le

right

le

right correct! 1 cent

le

right

correct! 1 cent

incorrect! 0 cent

incorrect! 0 cent

correct! 15 cent

incorrect! 0 cent

feedback

Figure 5.1 Task-switching paradigm with reward manipulation Participants had to respond to incongruent arrow-word combinations, either by responding to the direction of the arrow (i.e. <- or ->) or to the direction indicated by the word (“left” or “right”) with a left or right button press. A task cue preceding the target indicated according to which task (arrow or word) the participant had to respond on the current trial. The task performed on a particular trial either changed unpredictably compared with the preceding trial (i.e. switch trial; arrow - word or word - arrow) or remained the same (i.e. repeat trial; arrow-arrow, word-word). In addition we manipulated the value of each trial on a trial-by-trial basis by means of a reward anticipation cue (i.e. 1 vs. 10 or 15 cents; table 1) (see also (Aarts et al., 2010; Aarts et al., 2015). Reward could be earned with a correct and sufficiently quick response. Immediately following the response, feedback was given (e.g., “correct! 15 cents”). The cues and feedback were shown for 600 msec. RC interval: reward cue - task cue interval; CT interval: task cue - target interval ( table 5.1 ).

approved by the local ethics committee (CMO Arnhem-Nijmegen CMO 2001/095; 2007/153; 2008/159; 2009/058; 2010/402) and were in accordance with the Declaration of Helsinki.

Paradigm All participants performed a task-switching paradigm with a reward manipulation (figure 5.1) (Aarts et al., 2010; van Holstein et al., 2011). The task was programmed and presented using the Presentation® software (Neurobehavioral Systems, Inc.; http://www.neurobs.com). The test was preceded by 3 practice blocks. The first practice block (24 trials) contained the task cue and target, followed by feedback (“correct”, “incorrect”); in the second practice block (24 trials), reward cues were added. Finally, to account for inter-individual differences in response speed and subsequent task difficulty, we used the correct responses during the third practice block (32 trials), without reward or feedback, to determine each individual’s response deadline for 4 trials-types (Arrow/Word x Switch/Repeat). Participants were instructed to

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