Cognitive flexibility in humans and other laboratory animals

Assessing cognitive flexibility in humans and rhesus macaques with visual motion and neutral distractors

Introduction

Cognitive flexibility is the ability of an individual to make behavioral adjustments in response to internal and/or external changes. While it has been reported in a wide variety of species, established paradigms to assess cognitive flexibility vary between humans and non-human animals, making systematic comparisons difficult to interpret.

Methods

We developed a computer-based paradigm to assess cognitive flexibility in humans and non-human primates. Our paradigm (1) uses a classical reversal learning structure in combination with a set-shifting approach (4 stimuli and 3 rules) to assess flexibility at various levels; (2) it employs the use of motion as one of three possible contextual rules; (3) it comprises elements that allow a foraging-like and random interaction, i.e., instances where the animals operate the task without following a strategy, to potentially minimize frustration in favor of a more positive engagement.

Results and Discussion

We show that motion can be used as a feature dimension (in addition to commonly used shape and color) to assess cognitive flexibility. Due to the way motion is processed in the primate brain, we argue that this dimension is an ideal candidate in situations where a non-binary rule set is needed and where participants might not be able to fully grasp other visual information of the stimulus (e.g., quantity in Wisconsin Card Sorting Test). All participants in our experiment flexibly shifted to and from motion-based rules as well as color- and shape-based rules, but did so with different proficiencies. Overall, we believe that with such approach it is possible to better characterize the evolution of cognitive flexibility in primates, as well as to develop more efficient tools to diagnose and treat various executive function deficits.

Repeated eticlopride administration increases dopamine D2 receptor expression and restores behavioral flexibility disrupted by methamphetamine exposure to male rats

Repeated methamphetamine exposure impairs reversal learning in laboratory animals and downregulates dopamine D₂ receptor expression. In the present study, we tested the possibility that repeated exposure to the dopamine D₂ antagonist, eticlopride, would increase D₂ receptor expression, improve behavioral flexibility and restore behavioral flexibility that was disrupted by exposure to methamphetamine in rats. Male Sprague-Dawley rats received repeated daily pretreatment with the dopamine D₂ antagonist, eticlopride (0.0 or 0.3 mg/kg/day, 14 days). Three days after the last treatment, whole brain (minus olfactory bulbs and cerebellum) dopamine D₂ receptor expression was measured using flow cytometry in one group and reversal learning performance was measured in another group. Reversal learning was also measured in other groups prior to and after methamphetamine exposure (0.0 or 2.0 mg/kg, 4 injections, 2 h apart, 1 day) followed by repeated eticlopride (0.0 or 0.3 mg/kg, 14 days) treatment. Eticlopride treatment increased D₂ receptor expression and improved reversal learning performance. Methamphetamine impaired reversal learning performance and eticlopride treatment reversed the deficit. These results suggest that repeated administration of eticlopride can restore behavioral flexibility and that upregulation of D₂ receptors might be an effective adjunct to treatment of methamphetamine misuse.

The Effect of Chronic Alcohol on Cognitive Decline: Do Variations in Methodology Impact Study Outcome? An Overview of Research From the Past 5 Years

Excessive alcohol use is often associated with accelerated cognitive decline, and extensive research using animal models of human alcohol consumption has been conducted into potential mechanisms for this relationship. Within this literature there is considerable variability in the types of models used. For example, alcohol administration style (voluntary/forced), length and schedule of exposure and abstinence period are often substantially different between studies. In this review, we evaluate recent research into alcohol-induced cognitive decline according to methodology of alcohol access, as well as cognitive behavioral task employed. Our aim was to query whether the nature and severity of deficits observed may be impacted by the schedule and type of alcohol administration. We furthermore examined whether there is any apparent relationship between the amount of alcohol consumed and the severity of the deficit, as well as the potential impact of abstinence length, and other factors such as age of administration, and sex of subject. Over the past five years, researchers have overwhelmingly used non-voluntary methods of intake, however deficits are still found where intake is voluntary. Magnitude of intake and type of task seem most closely related to the likelihood of producing a deficit, however even this did not follow a consistent pattern. We highlight the importance of using systematic and clear reporting styles to facilitate consistency across the literature in this regard. We hope that this analysis will provide important insights into how experimental protocols might influence findings, and how different patterns of consumption are more or less likely to produce an addiction-vulnerable cognitive phenotype in animal models.