Joanna Golebiowska

Effects of optimism on motivation in rats

In humans, optimism is a cognitive construct related to motivation; optimists exert effort, whereas pessimists disengage from effort. In this study, using a recently developed ambiguous-cue interpretation (ACI) paradigm we took the unique opportunity to investigate whether “optimism” as a trait is correlated with motivation in rodents. In a series of ACI tests (cognitive bias screening, CBS), we identified rats displaying “pessimistic” and “optimistic” traits. Subsequently, we investigated the trait differences in the motivation of these rats to gain reward and to avoid punishment using a progressive ratio (PR) schedule of reinforcement paradigm. Although “optimistic” and “pessimistic” animals did not differ in their motivation to avoid punishment, the “optimistic” rats were significantly more motivated to gain reward than their “pessimistic” conspecifics. For the first time, we showed an association between cognitive judgment bias and motivation in an animal model. Because both investigated processes are closely related to mental health and wellbeing, our results may be valuable for preclinical modeling of many psychiatric disorders.

A Novel Dopamine Transporter Inhibitor CE-123 Improves Cognitive Flexibility and Maintains Impulsivity in Healthy Male Rats

Reduced cognitive abilities are often characterized by an impairment of flexibility, i.e., the ability to switch from learned rules or categories that were important in certain contexts to different new modalities that rule the task. Drugs targeting the dopamine transporter (DAT) are widely used for their potential to enhance cognitive abilities. However, commercially available drugs are of limited specificity for DAT, blocking also noradrenaline and serotonine transporters, that can lead to unwanted side effects in healthy subjects. Therefore, we tested a newly synthetized compound (CE-123) with higher specificity for DAT in male rats in an attentional set-shifting task (ASST), that proves for cognitive flexibility and a 5-choice serial-reaction time task (5-CSRTT) assessing visuospatial attention and impulsivity. Treated rats at a dose of 0.3 and 1.0 but not 0.1 mg/kg bodyweight showed reduced extra-dimensional shifts in the ASST compared to controls indicating increased cognitive flexibility. Rats treated with R-Modafinil, a commercially available DAT inhibitor at a dose of 10 mg/kg bodyweight showed increased premature responses, an indicator of increased impulsivity, during a 10 s but not a 2.5, 5, or 7.5 s intertrial interval when compared to vehicle-treated rats in the 5-CSRTT. This was not found in rats treated with CE-123 at the same dose as for R-Modafinil. Visuospatial attention, except premature responses, did not differ between R-Modafinil and CE-123-treated rats and their respective controls. Thus, CE-123 increased cognitive flexibility with diminished impulsivity.

Lesions of the Orbitofrontal but Not Medial Prefrontal Cortex Affect Cognitive Judgment Bias in Rats

Neuroimaging studies in humans have recently shown that the prefrontal cortex (PFC) and orbitofrontal cortex (OFC) mediate bias in the judgment of forthcoming events. In the present study, we sought to determine whether cognitive judgment bias (CJB) is also dependent on these prefrontal regions in non-human animals. For this, we trained a cohort of rats in the ambiguous-cue interpretation (ACI) paradigm, subjected them to excitotoxic lesions in the medial PFC (mPFC) and OFC, and tested the effects of neuronal loss within these regions on CJB. Comparison of the lesions’ behavioral effects in the ACI paradigm revealed that neuronal loss within the OFC but not within the mPFC influences the interpretation of ambiguous cues by animals. Our findings demonstrate the specific involvement of the OFC in CJB in rats.

Effects of acute dopaminergic and serotonergic manipulations in the ACI paradigm depend on the basal valence of cognitive judgement bias in rats

Abstract Recent findings have revealed that pharmacological enhancement of dopaminergic (DA) function by the administration of a DA precursor (dihydroxy‐l‐phenylalanine; L‐DOPA), but not the selective serotonin reuptake inhibitor (SSRI) citalopram, increases an optimism bias in humans. To test whether dopamine might play a similar role in non‐human animals, in the present study, we evaluated the effects of acute injections of L‐DOPA, the D2 receptor antagonist haloperidol, and the SSRI escitalopram on cognitive judgement bias of rats in the ambiguous‐cue interpretation (ACI) paradigm. Three different doses of each drug were administered in a fully randomised Latin‐square design, along with saline treatment as a control, 30 min before the ACI tests. Initial analysis revealed that only animals treated with L‐DOPA were more ‘pessimistic’ than the saline‐treated controls. Neither haloperidol nor escitalopram significantly affected the cognitive judgement bias of rats. However, further analysis revealed that the effects of the tested compounds might depend on the basal cognitive judgement bias of the tested animals. When we divided the rats into ‘optimistic’ and ‘pessimistic’ groups based on their cognitive judgement bias in the drug‐free state, it turned out that acute administration of L‐DOPA caused a ‘pessimistic’ shift in ‘optimistic’ animals while showing no significant effects on ‘pessimists’. Acute administration of haloperidol caused a ‘pessimistic’ shift in ‘optimistic’ animals and an ‘optimistic’ shift in ‘pessimists’. Acute administration of escitalopram caused a ‘pessimistic’ shift in ‘optimistic’ animals and had no significant effects on ‘pessimists’, except that the middle tested dose rendered the rats more ‘optimistic’.