Supplementary Materials
Acute nicotine increases both impulsive choice and behavioural disinhibition in rats
Kolokotroni, K.Z. *, Rodgers, R.J.and Harrison, A.A.
Behavioural Neuroscience Laboratory
Institute of Psychological Sciences`
University of Leeds
Leeds LS2 9JT
U.K.
*Address all correspondence to: Dr Zoe Kolokotroni, Department of Psychology, Leeds Metropolitan University, D420 Civic Quarter, Calverley Street, Leeds, LS1 3HE, England.
Phone: +44-(0)113-812-4968
Fax: +44-(0)113-343-5749 (non-confidential)
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Supplementary Results
Experiment 3: effect of alterations in primary motivation on performance of the Go/No-go and Delayed Reward tasks.
I. Go/No-go Task
For all descriptive data see Table 5.
Phase 1: decrease in primary motivation
During 1hr prefeeding with normal lab chow, animals consumed 12.58 ± 0.74g of food leading to a weight gain of 15.85 ± 1.83g (increase of 3.62 ± 0.28% versus baseline). During 30 minutes prefeeding on sucrose pellets, animals consumed 12.10 ± 1.03g of food leading to a weight gain of 16.63 ± 2.81g (increase of 3.69 ± 0.60% versus baseline). Food consumption did not differ as a function of food type (t = 0.405 df = 5, N.S), nor did weight gain expressed either as an absolute or percentage increase (all t ≤ -0.301, df = 5, N.S.).
Accuracy of Responding: No significant effect on overall performance was observed following pre-feeding with either normal chow (t = -0.575, df = 6, N.S.) or sucrose pellets (t = -1.525, df = 5, N.S). Analysis of the independent accuracy during Go and No-go trials further mirrored the lack of effect on accuracy of performance in the task (normal chow: all t ≤ -1.393, df = 6, N.S.; sucrose pellets: all t ≤ -1.470, df = 5, N.S.).
Anticipatory Responding: Neither form of prefeeding had any significant effect on the frequency of early responding (normal chow: all t ≤ 0.977, df = 6, N.S.; sucrose pellets: all t ≤ 2.127, df = 5, N.S.), or on inappropriate magazine entries (normal chow: all t ≤ 1.208, df = 6, N.S.; sucrose pellets: all t ≤ 2.004, df = 5, N.S.) during Go and No-go trials.
Speed of Responding: No significant effects of prefeeding were observed on correct or incorrect response latencies in the task (normal chow: all t ≤ -1.427, df = 6, N.S.; sucrose pellets: all t ≤ 0.524, df = 5, N.S.). Although incremental trends were observed for magazine latencies during Go and No-Go trials, these failed to reach significance following either feeding manipulation (normal chow: all t ≤ 1.427, df = 6, N.S.; sucrose pellets: all t ≤ -1.689, df = 5, N.S.).
Omissions: Failure to collect reward during No-go trials was found to increase significantly in response to prefeeding with both normal chow (Z= -1.997, p = 0.046) and sucrose pellets (Z = -2.201, p = 0.028).
Phase 2: increase in primary motivation
Restricting food intake to 50% of the normal ration on the day prior to testing led to a loss of 5.85 ± 1.03g bodyweight (a decrease of 1.30 ± 0.22% relative to baseline).
Accuracy of Responding: Food restriction had no effect on overall performance accuracy in comparison to baseline (t = -0.688, df = 6, N.S.). Independent analysis of Go and No-go trials supported further the lack of influence of food restriction on task performance (t = -0.611, df = 6, N.S.; t = -0.894, df = 6, N.S., respectively).
Anticipatory Responding: Early responding during both Go and No-go trials did not differ from baseline following an increase in hunger motivation (t = 0.405, df = 6, N.S.; t = 0.595, df = 6, N.S., respectively). The frequency of magazine entries during Go and No-go trials also remained unchanged (t = -0.930, df = 6, N.S.; t = 1.066, df = 6, N.S., respectively).
Speed of Responding:Restricting food intake resulted in a significant decrease in the latency to incorrectly respond during No-go trials (t = 3.526, df = 6, p = 0.012). In contrast, correct response latency did not differ in comparison to baseline (t = -0.380, df = 6, N.S.) nor did the speed with which reward was collected following either a correct Go or No-go trial (t = 0.516, df = 6, N.S.; t = -1.655, df = 6, N.S., respectively).
Omissions: There was no effect of food restriction on the frequency of failure to collect reward during No-go trials (Z = -0.211, N.S.)
II. Systematic Delayed Reward task
For all descriptive data see Table 6.
Phase 1: Decrease in primary motivation
During 1 hr prefeeding on normal chow, animals consumed 11.72 ± 0.50g of food leading to a weight gain of 12.88 ± 0.71g (increase of 2.54 ± 0.14 % relative to baseline). Similarly, during 30min free access to sucrose pellets, animals consumed 12.49 ± 0.84g food leading to a weight gain of 12.32 ± 1.03g (increase of 2.38 ± 0.21% relative to baseline). Food consumption did not differ as a function of food type (t = -1.100 df = 9, N.S) nor did weight gain expressed either as an absolute or percentage increase (t = 0.550, df = 9, N.S.; t = 0.766, df = 9, N.S., respectively).
Choice Behaviour: Prefeeding on chow or sucrose had no significant effects on overall percentage choice of delayed reward in comparison to baseline (normal chow: t = 1.527, df = 9, N.S; sucrose pellets: t = 2.231, df = 9, N.S.). Analysis of choice by delay also failed to reveal any significant main effects of level of motivation on choice of delayed reward (normal chow: F(1,9) = 0.577, N.S.; sucrose pellets: F(1,9) = 2.289, N.S.). A highly significant main effect of delay was however found following both feeding manipulations (normal chow: F(4,36) = 41.652, p < 0.001; sucrose pellets: F(4,36) = 35.766, p < 0.001), post hoc analysis confirming a reduction in choice of delayed reward at 20, 40 and 60 seconds relative to 0 second delay trials (all p<0.01). No significant motivation x delay interactions were observed (normal chow: F(4,36) = 0.661, N.S.; sucrose pellets: F(4,36) = 0.791, N.S.).
Speed of Responding: Relative to baseline, prefeeding on normal chow significantly increased trial initiation latency (t= -4.471, df = 9, p=0.001) and reduced the speed with which the immediate reward was selected (t =-2.326, df = 9, p= 0.045). However, no changes were observed in delayed response latency (t = -1.892, df = 9, N.S.), or in magazine latencies following either immediate (t = -1.170, df = 9, N.S.) or delayed choices (t = 1.325, df = 9, N.S.). In contrast, while prefeeding with sucrose pellets also significantly increased trial initiation latency (t = -2.998, df = 9, p = 0.015), no significant changes were evident on either immediate and delayed response latencies (t =-1.589, df = 9, N.S.; t = 1.476, df = 9, N.S., respectively). Decreasing the motivation for sucrose pellets did however increase significantly delayed reward magazine latency (t = -3.229, df = 9, p = 0.009), whilst leaving unchanged magazine latency following an immediate choice (t = 0.565, df = 9, N.S.).
Omissions: Prefeeding with either normal chow or sucrose pellets had no significant effects on the failure to initiate trials (normal chow: Z=-1.389, N = 10; N.S.; sucrose pellets: Z = -1.219; N=10, N.S.) or to collect reward following a delayed reward choice (normal chow: Z = -1.122, N = 10; N.S.; sucrose pellets: Z = -1.130, N= 10; N.S.).
Phase 2: increase in primary motivation
The reduction of food allowance by 50% on the day prior to testing led to a loss of an average of 4.52 ± 0.72gof bodyweight (a decrease of 1.01 ± 0.002% relative to baseline).
Choice Behaviour: Food restriction led to a significant increase in overall percentage choice of the delayed larger reward (t = -2.507, df = 9, p = 0.033): overall choice of delayed reward: baseline = 70.06 ± 7.18%; following reduction of daily food intake = 73.06 ± 8.07%. Analysis of choice by delay further supported the increased preference for the delayed reward (F(4,36) = 8.253, p = 0.018). A main effect of delay was also revealed (F(4,36) = 32.826, p < 0.001), again confirming that the choice of the delayed larger reward decreased with increasing delays, reaching significance at the 40 and 60 second delays relative to the 0 second delay condition (all p<0.001). The effect of hunger on choice behaviour was delay-dependent, as indicated by the significant motivation x delay interaction (F(4,36) = 5.688, p = 0.001). To examine this interaction further, a series of repeated measures t-tests compared choice behaviour at each delay. While hunger significantly increased the choice of the delayed reward during the 10 second delay condition versus baseline (t = -5.577, df = 9, p < 0.001) (see Fig. 3), choice of delayed reward across all remaining delay conditions remained comparable to baseline (all t ≥ 0.210, df = 9, N.S.).
Speed of Responding:Food restriction had no significant effect on the latency to initiate trials (t = -1.327, df = 9, N.S.), or the speed with which animals selected an immediate or delayed reward (t = -0.260, df = 9, N.S., t = -0.740, df = 9, N.S., respectively). Although magazine latency following an immediate reward choice furthermore did not differ from baseline (t = -1.189, df = 9, N.S.), the speed with which reward was collected following a delayed reward choice became significantly faster (t = 1.905, df = 9, p = 0.045)
Omissions: Food restriction significantly decreased the frequency of failures to initiate trials during the task (Z = -2.060, N = 10, p= 0.039), whereas magazine omissions following a delayed reward choice did not differ significantly from baseline (Z = 0.001, N= 10, N.S.)
Table 1: Experiment 1-The effect of acute mecamylamine on performance in the Symmetrically Reinforced Go/No-go task
BehaviouralMeasure / Mecamylamine Dose (mg/kg)
Saline
(control) / 0.1 / 0.3 / 1.0
Percentage Total Correct trials
Percentage Correct Go trials
Percentage Correct No-go trials
Go trials with EarlyResponses
No-go trials with Early Responses
Go trials Magazine Entries
No-Go trials Magazine Entries
Correct ResponseLatency (s)
Incorrect Response Latency (s)
Go magazineLatency (s)
No-go Magazine Latency (s) / 91.02 ± 1.02
97.95 ± 0.81
84.09 ± 1.69
15.91 ± 2.66
5.55 ± 1.57
0.82 ± 0.46
9.91 ± 2.32
0.83 ± 0.13
2.02 ± 0.32
0.39 ± 0.09
0.70 ± 0.13 / 92.5 ± 1.57
98.64 ± 0.91
86.36 ± 3.00
17.09 ± 1.94
4.82 ± 1.48
0.64 ± 0.24
6.18 ± 1.29
0.87 ± 0.12
0.95 ± 0.17§†
0.32 ± 0.05
0.66 ± 0.10 / 90.57 ± 1.27
98.64 ± 0.70
82.5 ± 2.48
16.55 ± 1.74
5.91 ± 1.34
1.09 ± 0.44
8.55 ± 2.16
0.75 ± 0.13
2.17 ± 0.40
0.33 ± 0.06
0.68 ± 0.14 / 91.82 ± 1.03
99.32 ± 0.35
84.32 ± 1.87
16.73 ± 2.31
6.45 ± 1.51
0.91 ± 0.31
7.73 ± 1.55
0.70 ± 0.09
1.71 ± 0.28
0.35 ± 0.05
0.66 ± 0.10
Each value represents the mean ± SEM §, p<0.05versus 0.3mg/kg mecamylamine. †, p<0.05versus1.0mg/kg mecamylamine
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