Oxygen responses within the nucleus accumbens are associated with individual differences in effort exertion in rats

Figures

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  Figure 1. Reconstructions of carbon paste electrodes (CPE) placements within: (a) the nucleus accumbens (NAc) and (b) the orbitofrontal cortex (OFC). The location of CPE tips are marked by the black circles. Coronal slices are adapted from (Paxinos & Watson, 2009)

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  Figure 2. Overview of behavioural performance (a,b) and stratification of behavioural measures by trial type and response groups (c,e). (a) The group level mean breakpoint across the 10 PR sessions. (b) Division of high and low responders based upon a split of subjects’ mean breakpoint. (c) The mean number of lever presses made were greater in late trials, and in high responding rats. (d) The mean delay‐to‐reward was significantly greater in late trials, but did not differ between groups. (e) The mean rate of lever pressing was reduced in late trials, but did not differ between groups. Error bars represent ±1 SEM

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  Figure 3. Tissue O2 responses within the nucleus accumbens (NAc) and orbitofrontal cortex (OFC) during progressive ratio (PR) performance. (a) Mean O2 reward responses within the NAc following the first half (“early”) and second half (“late”) of PR trials across all subjects. The solid grey line represents a significant increase in O2 levels in early trials, compared to 0 s. The dashed grey line shows all time points that are significantly lower than 0 s, in early trials. The solid black line shows all time points within late trials with significantly higher O2 levels compared to the 0 s time point. (b) The peak NAc O2 reward response was significantly greater in late relative to early trials. (c) The area under the curve (AUC) of the NAc response was significantly elevated in late trials relative to the early PR trials. (d) The mean OFC O2 reward response following the early and late PR trials across all subjects. (e) The peak value of the mean OFC response was significantly greater in late relative to early trials. (f) The AUC of the mean OFC reward response did not differ between early and late trials. * p < 0.05; ** p < 0.01; *** p < 0.001. Error bars represent ±1SEM

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  Figure 4. Associations between behavioural performance and nucleus accumbens (NAc) O2 responses during progressive ratio (PR) performance. (a) The significant positive correlation between each rats’ breakpoint and peak value of their respective O2 response. (b) The significant positive correlation between breakpoint and the area under the curve (AUC) of the NAc O2 response. (c) The mean NAc O2 reward responses in low and high performing rats. The dashed grey line shows all time points that had significantly lower O2 levels relative to 0 s, in low responding rats. The solid black line shows all time points with significantly higher O2 levels compared to the 0 s time point, within the high responding group. (d) The peak NAc O2 response was significantly greater in high performing rats. (e) The AUC of the O2 response was significantly greater in high performers. (f) The mean O2 response for high and low performing rats from the first five trials of each session. The solid black line shows all time points with significantly higher O2 levels compared to the 0 s time point, within the high responding group only. (g) High performing rats had a significantly higher peak NAc O2 response in the…

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  Figure 5. Tissue O2 changes following uncued rewards within the nucleus accumbens (NAc) and orbitofrontal cortex (OFC). (a) The mean O2 responses to 1 (“small”) and 3 pellet (“large”) rewards within the NAC. (b) The peak NAc O2 response of the responses to single and three pellet rewards for both low and high responding animals. (c) NAc O2 responses to early and late single pellet reward trials. (d) The mean OFC O2 responses to 1 and 3 pellet rewards. (e) The area under the curve (AUC) of the OFC O2 response to small and large rewards for both low and high responding rats. (f) OFC O2 responses to early and late single pellet reward trials. Error bars represent ±1 SEM