Performance on test conditions
In a preliminary analysis ‘Cohort’ was included as a second between-subject factor to establish if there were any differences regarding the two cohorts. The only main effect of cohort was for the Dark condition (p<0.05), and no other main effects or interactions involving this factor were observed (all Fs< 4.00; all ps > 0.06). Therefore, the cohort data were pooled and analysed together for each separate condition, though the Dark condition data received extra scrutiny.
In the following analyses, ‘Drug’ refers to saline or clozapine (within subject) while Group refers to iDREADDs or GFP infusions (between subject).
Standard T-maze: There was a significant main effect of Drug:F 1,20 = 7.01, p = 0.015,ηp2 = 0.25, but not a main effect of Group or Drug × Group interaction: Fs< 0.85, ps > 0.37,ηps2 < 0.04 (Figure 6). This set of results showed that clozapine did not exert a greater effect in the active viral group when compared with the control viral group.
Start T-maze: There was a main effect of Drug:F 1,20 = 5.76, p = 0.03,ηp2 = 0.22, but no main effect of Group or Drug × Group interaction: Fs< 3.48, ps > 0.08,ηps2 < 0.15 (Figure 6). This pattern of results corresponded to that seen for the Standard condition.
Rotation T-maze: There was a significant main effect of Drug:F 1,20 = 12.02, p = 0.002,ηp2 = 0.37 but also a Drug × Group interaction: F 1,20 = 6.8, p = 0.016,ηp2 = 0.25. Simple main effects analyses revealed a significant decline in performance following clozapine infusions within the iDREADDs group that was not seen in the GFP control group: F 1,13 = 25.36,p< 0.0001 (Figure 6). All other tests were non-significant: Fs < 2.75,ps > 0.11.
Opposite arm T-maze: As in the Rotation condition, there was a significant main effect of Drug: F 1,20 = 7.7,p = 0.01, ηp2 = 0.278 and a Drug × Group interaction: F 1,20 = 4.55,p = 0.045, ηp2 = 0.18. Again, there was decline in performance following clozapine infusions in the iDREADDs group that was not seen in the GFP control group:F 1,13 = 16.6, p <0.001 (Figure 6). All other tests were non-significant: Fs< 0.89, ps > 0.35.
Dark T-maze: The behavioural analyses revealed a significant Drug × Group interaction: F 1,20 = 7.8, p = 0.011, ηp2 = 0.28, however, there was no main effect of Drug or Group: Fs< 0.036, ps > 0.85. Follow-up simple main effects analyses showed that again iDREADDs animals’ performance declined following the clozapine infusions relative to saline: F 1,13 = 5.8, p = 0.025. All other tests were non-significant: Fs < 2.84, ps > 0.10 (Figure 6). For this one condition, there was a significant main effect of Cohort (F 1,18 = 10.6, p = 0.004). Overall, Cohort 1 had lower scores, possibly reflecting the absence of an additional saline trial. Nevertheless, the key intervention comparisons were within-subject (saline vs clozapine), being effective across both Cohorts.