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Chapter 7
Finally, assessment of the three-way interaction betweenReward, Task switching andResponse
switching revealed that aPFC stimulation decreased signaling in the putamen (
figure 7.5 –
blue coloring
) (aPFCSTIM-BASE x Reward x Task switch x Response switch: PSVC_ FWE
= 0.020, t = 3.96, z = 3.86, peak x, y, z = -28, -8, 8). This putamen effect was greater for aPFC
stimulation than for dlPFC or PMC stimulation ([aPFCSTIM-BASE > dlPFC STIM-BASE =
PMC STIM-BASE] x Reward x Task switch x Response switch: PSVC_FWE = 0.023, t = 3.92,
z = 3.83, peak x, y, z = -26, -8, 12).
There were no Reward-related, Reward x Task switching-related, or Reward x Task switching
x Response switching-related
increases
in neural signal after stimulation of the aPFC.
In summary, stimulation of the aPFC modulated processing in the anterior portion of the
caudate nucleus as a function of Reward, while it modulated activity in the putamen as a
function of the interaction between Reward, Task- and Response switching. Visualization
of below-threshold effects (
figure 7.5a
) reveals an anterior to posterior and medial to lateral
gradient in the striatum as a function of task demands. In addition, the coronal slices in
figure
7.5b
at a higher threshold illustrate the anterior to posterior (y = 16 vs. y = -8), ventral to
dorsal (z = 2 vs. z = 8) and medial to lateral (x = 6 vs. x = -28) gradient.
Assessment of the main effect of task switching did not reveal decreased neural signaling after
dlPFC stimulation.
Analysis of the main effect of Task switching (task switch versus task repeat) and of the
two-way interaction between Task switching and Response switching did not reveal any
regions in which dlPFC stimulation changed neural signaling.
Assessment of the main effect of response switching did not reveal decreased neural signaling
after PMC stimulation.
Analysis of the main effect of Response switching (response switch versus response repeat)
did not reveal any regions in which PMC stimulation changed neural signaling.
Behavior
Main effects of Reward anticipation, Task switching and Response switching
Across sessions, participants responded faster on high reward trials compared with low reward
trials (Reward: F(1,26) = 39.114, p < 0.001). There was no main effect of reward in terms of
error rates (Reward: F(1,26) < 1). In terms of task-switching performance, participants made
more errors on switch trials compared with repeat trials (Task switching: F(1,26) = 27.825,
p < 0.001), but showed no main effect of task switching in terms of response times (Task
switching: F(1,26) < 1). Finally, participants responded more slowly and made more errors
when the same response had to be repeated compared with trials on which the response
switched (Response switching in terms of response times: F(1,26) = 11.998, p = 0.002), and
error rates F(1,26) = 31.989, p < 0.001).