Proefschrift_Holstein

Chapter 6

TRIAL 1

TRIAL 2 task switch

TRIAL 3 task repeat

TRIAL 4 task switch

task cue

target

le lever right lever

le lever right lever

le lever right lever

le lever right lever

response

low reward block high reward block feedback

Figure 6.1 Cued task-switching paradigm with reward manipulation On test, animals were presented with response-incongruent combinations of the auditory and visual stimuli (e.g. tone and house light), inducing a response conflict. Resolving this conflict correctly required the use of the task cue. For example, when a tone and flashing panel lights (associated with a left and right lever press, respectively) were preceded by a task cue signalling the auditory task (e.g. white noise), a left lever press would lead to a reward. However, when the same combination of stimuli was preceded by the presentation of the house light, a discrimination based on the visual stimulus was required (i.e. a right lever press was correct). Crucially, this paradigm allowed the trial-by-trial manipulation of a repetition or switch of the task set, allowing a direct comparison of performance on repeat (i.e. auditory -> auditory and visual -> visual) and switch (auditory -> visual and visual -> auditory) trials. In addition, animals were trained and tested in two distinct reward contexts, allowing the assessment of task-switching under different reward circumstances.

Table 6.2 Experimental design: test Task cue Compound stimuli

Correct lever

Reward context

Low [RC-A]

High [RC-B]

4 x A1-V2

Lever 1

1 pellet

3 pellets

8 x AUD

4 x A2-V1

Lever 2

1 pellet

3 pellets

4 x A1-V2

Lever 2

1 pellet

3 pellets

8 x VIS

4 x A2-V1 3 pellets Task cues (noise and house light): AUD (auditory) and VIS (visual) signal the relevant modality; compound stimuli are composed of one of two auditory stimuli (A1 or A2; clicker and tone) and one of two visual stimuli (V2 or V1; flashing or steady panel lights), creating a response incongruent compound; In case of AUD  A1-V2 a left lever press is rewarded, whereas in case of VIS  A1-A2 a right lever press is rewarded with 1 or 3 pellets depending on the reward context (RC). Lever 1 1 pellet

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