Name: assessment of stress effects on cognitive flexibility using an operant strategy shifting paradigm
Uploaded: 2020-05-04T15:00:00
Description: Watch this Scientific Journal Video about Assessment of Stress Effects on Cognitive Flexibility using an Operant Strategy Shifting Paradigm at JoVE.com

The authors would like to thank Hannah Zamore, Emily Saks, and Josh Searle for their help in establishing this operant strategy shifting paradigm in the Grafe lab. They would also like to thank Kevin Snyder for his help with the MATLAB code for analysis.

All procedures in this study were approved by the Institutional Animal Care and Use Committee (IACUC) at Bryn Mawr College.&#160;Obtain IACUC or otherwise applicable regulatory approval before ordering laboratory animals and beginning experimentation.
1. Animal preparation
<ol>
	<li>Acquire male and female adult Sprague Dawley rats. 
	NOTE: The rats can be delivered before 65 days of age, but do not begin procedures until after this point to ensure that both males and females are fully ...

The protocol demonstrates how to measure the effects of stress on cognitive function. Specifically, a modified operant strategy shifting paradigm is used in rodents, which measures cognitive flexibility (analogous to the Wisconsin Card Sorting Task in humans)1. Cognitive flexibility denotes the ability to adapt cognitive processing strategies to face new conditions in the environment, and it is crucial for normal daily functioning2. As human studies on cognitive flexibility...

In humans, stressful life events can impair cognitive function (i.e, cognitive flexibility1), which denotes the ability to adapt cognitive processing strategies to face new conditions in the environment2. Impairment in cognition precipitates and exacerbates many psychiatric disorders, such as Post Traumatic Stress Disorder (PTSD) and Major Depressive Disorder (MDD)3,4. These disorders are twice as prevalent in females5,6,7,8, yet the biological basis for this disparity remains unknown. Aspects of executive functioning in humans can be assessed using the Wisconsin Card Sorting Task, a demonstration of cognitive flexibility2. Performance in this task is impaired in patients with PTSD9 and MDD10, but the neural basis of this change can only be examined by brain imaging11.
Advances in understanding how stress affects the brain have been made through the use of animal models, particularly rodents. As cognitive flexibility is affected in stress-related diseases, it is an exceptionally relevant phenotype to examine in rodents. To date, most stress neurobiology literature has used an alternative cognitive flexibility paradigm (sometimes referred to as the digging task)12,13,14,15. While this task has been extensively vetted, it requires more time and effort by the experimenter to train rodents. Adapted and described here is a well-established automated set-shifting protocol16 to assess cognitive flexibility in male and female Sprague Dawley rats using various stress models17,18. The procedure requires minimal oversight by the experimenter and allows multiple rats to be tested simultaneously. In addition, unlike other versions of this automated task19, the adaptation of this paradigm only requires 3 days of training and includes an efficient programmed data analysis.
Whether stress enhances or impairs cognitive function depends on the type, intensity, and duration of the stressor, as well as the timing of the stressor in relation to learning or executing a cognitive task20,21. Thus, the protocol incorporates stress procedures both before and after the operant training. It also examines representative results from stress studies. In addition, the brain regions underlying particular aspects of set-shifting have been well-established2,16,22; thus, the report also describes how to target and assess particular brain regions during or after the stress and strategy shifting procedures.
There has been limited research on directly examining sex differences in cognitive flexibility18,23. &#160;The protocol describes how to 1) incorporate both male and female rats into the experimental paradigm, then 2) track estrous cycles before and during the procedures in freely cycling females. Prior studies have indicated that stress before operant training can lead to sex-specific deficits in cognitive flexibility in rats17. Particularly, female rats exhibit disruptions in cognitive flexibility after stress, whereas cognitive flexibility improves in male rats after stress17. Interestingly, a major hallmark of stress-related psychiatric disorders, which have a sex-biased incidence in humans, is cognitive inflexibility. These results suggest that females may be more vulnerable to this type of cognitive impairment than males. The use of these techniques in animal models will shed light on the effects of stress on the brain and how it impairs cognition in psychiatric disorders in humans.

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			<td height="21" style="height:21px;width:335px;">MatLab</td>
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			<td>Software; code to help analyze set shifting data, available upon request.</td>
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assessment of stress effects on cognitive flexibility using an operant strategy shifting paradigm

Stress affects cognitive function. Whether stress enhances or impairs cognitive function depends on several factors, including the 1) type, intensity, and duration of the stressor; 2) type of cognitive function under study; and 3) timing of the stressor in relation to learning or executing the cognitive task. Furthermore, sex differences among the effects of stress on cognitive function have been widely documented. Described here is an adaptation of an automated operant strategy shifting paradigm to assess how variations in stress affect cognitive flexibility in male and female Sprague Dawley rats. Specifically, restraint stress is used before or after training in this operant-based task to examine how stress affects cognitive performance in both sexes. Particular brain areas associated with each task in this automated paradigm have been well-established (i.e., the medial prefrontal cortex and orbitofrontal cortex). This allows for targeted manipulations during the experiment or the assessment of particular genes and proteins in these regions upon completion of the paradigm. This paradigm also allows for the detection of different types of performance errors that occur after stress, each of which has defined neural substrates. Also identified are distinct sex differences in perseverative errors after a repeated restraint stress paradigm. The use of these techniques in a preclinical model may reveal how stress affects the brain and impairs cognition in psychiatric disorders, such as post-traumatic stress disorder (PTSD) and major depressive disorder (MDD), which display marked sex differences in prevalence.

The adapted automated operant strategy shifting paradigm outlined above was used to determine if repeated restraint stress affects cognition in male and female Sprague Dawley rats. Representative behavioral data are described in Figure 2 below. In short, control and repeatedly restrained rats performed this operant strategy shifting test, which consisted of a series of tasks: side discrimination, side reversal, and light discrimination.
Trials to criterion for eac...

Watch this Scientific Journal Video about Assessment of Stress Effects on Cognitive Flexibility using an Operant Strategy Shifting Paradigm at JoVE.com

Assessment of Stress Effects on Cognitive Flexibility using an Operant Strategy Shifting Paradigm

Stressful life events impair cognitive function, increasing the risk of psychiatric disorders. This protocol illustrates how stress affects cognitive flexibility using an automated operant strategy shifting paradigm in male and female Sprague Dawley rats. Specific brain areas underlying particular behaviors are discussed, and translational relevance of results are explored.

Stress affects cognitive function. Whether stress enhances or impairs cognitive function depends on several factors, including the 1) type, intensity, and ...

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