Improvements and important considerations for the 5-choice serial reaction time task-An effective measurement of visual attention in rats

Effects of the cannabinoid receptor 1 positive allosteric modulator GAT211 and acute MK-801 on visual attention and impulsivity in rats assessed using the five-choice serial reaction time task

Altered interactions between endocannabinoid and glutamate signaling may be involved in the pathophysiology of schizophrenia and acute psychosis. As cognitive disturbances are involved in schizophrenia, increased understanding of the roles of these neurotransmitter systems in cognition may lead to the development of novel therapeutics for disorder. In the present study, we examined the effects of a recently synthesized cannabinoid receptor 1 (CB1R) positive allosteric modulator GAT211 in a rodent model of acute psychosis induced by systemic treatment with MK-801. To assess cognitive function, we used the Five-Choice Serial Reaction Time (5CSRT) task, conducted in touchscreen-equipped operant conditioning chambers. Our measures of primary interest were accuracy - indicative of visual attentional capacity - and the number of premature responses - indicative of impulsivity. We also measured latencies, omissions, and perseverative responding during all test sessions. Thirteen adult male Long Evans rats were trained on the 5CSRT and were then tested using a repeated measures design with acute MK-801 (0 or 0.15 mg/kg, i.p.) and GAT211 (0, 3, or 10 mg/kg, i.p.) administration. Acute MK-801 severely impaired accuracy, increased omissions, and increased the number of premature responses. MK-801 also significantly increased correct response latencies, without significant effects on incorrect or reward correction latencies. GAT211 had no significant effects when administered alone, or in combination with acute MK-801. These data confirm the dramatic effects of acute MK-801 treatment on behavioral measures of attention and impulsivity. Continued investigation of CB1R positive allosteric modulators as potential treatments for the cognitive symptoms of schizophrenia and related disorders should be pursued in other rodent models.

Efficient training of mice on the 5-choice serial reaction time task in an automated rodent training system

Experiments aiming to understand sensory-motor systems, cognition and behavior necessitate training animals to perform complex tasks. Traditional training protocols require lab personnel to move the animals between home cages and training chambers, to start and end training sessions, and in some cases, to hand-control each training trial. Human labor not only limits the amount of training per day, but also introduces several sources of variability and may increase animal stress. Here we present an automated training system for the 5-choice serial reaction time task (5CSRTT), a classic rodent task often used to test sensory detection, sustained attention and impulsivity. We found that full automation without human intervention allowed rapid, cost-efficient training, and decreased stress as measured by corticosterone levels. Training breaks introduced only a transient drop in performance, and mice readily generalized across training systems when transferred from automated to manual protocols. We further validated our automated training system with wireless optogenetics and pharmacology experiments, expanding the breadth of experimental needs our system may fulfill. Our automated 5CSRTT system can serve as a prototype for fully automated behavioral training, with methods and principles transferrable to a range of rodent tasks.

Ethanol induces maladaptive impulse control and decreased seeking behaviors in mice

Waiting impulsivity is a risk factor for many psychiatric disorders including alcohol use disorder (AUD). Highly impulsive individuals are vulnerable to alcohol abuse. However, it is not well understood whether chronic alcohol use increases the propensity for impulsive behavior. Here, we establish a novel experimental paradigm demonstrating that continuous binge-like ethanol exposure progressively leads to maladaptive impulsive behavior. To test waiting impulsivity, we employed the 5-choice serial reaction time task (5-CSRTT) in C57BL/6J male mice. We assessed premature responses in the fixed and variable intertrial interval (ITI) 5-CSRTT sessions. We further characterized our ethanol-induced impulsive mice using Open Field, y-maze, two-bottle choice, and an action-outcome task. Our results indicate that continuous binge-like ethanol exposure significantly increased premature responses when mice were tested in variable ITI sessions even during a prolonged abstinent period. Ethanol-induced impulsive mice exhibited anxiety-like behavior during chronic exposures. This behavior was also observed in a separate cohort that was subjected to 20 days of abstinence. Ethanol-treated mice were less motivated for a sucrose reward compared with air-exposed control mice, while also demonstrating reduced responding during action-outcome testing. Overall, ethanol-treated mice demonstrated increased impulsive behavior, but a reduced motivation for a sucrose reward. Although waiting impulsivity has been hypothesized to be a trait or risk factor for AUD, our findings indicate that maladaptive impulse control can also be potentiated or induced by continuous chronic ethanol exposure in mice.

Appetitive conditioning task in a shuttle box and its comparison with the active avoidance paradigm

The main features of the Shuttle Box Active Avoidance paradigm (e.g., the use of simple locomotor response as an operant and electrical current as a primary reinforcer) make this task easily automated. However, learning in this paradigm cannot be easily separated from the specificity of fear motivation. Punishment and negative reinforcement highly affect behavior in this task and complicate learning. In the present study, we describe a novel computer-controlled appetitive task in a shuttle box and compare it with active avoidance. The appetitive task was performed in the same shuttle box apparatus, additionally equipped with food dispensers in each compartment, and using a similar protocol. The reinforced reaction included the transition to the feeder in the opposite compartment in response to a stimulus. Animals mastered the appetitive task faster than the active avoidance task in the shuttle box. Other major differences between the models were the number and dynamics of intertrial responses (ITRs). Whereas in active avoidance the number of ITRs was low during learning, in the appetitive task rates were higher and they persisted throughout learning. Overall, the findings demonstrate some benefits of the appetitive task as a control condition to active avoidance: the use of a similar reaction and apparatus, no prior habituation, and fast acquisition.

Exploratory relationships between cognitive improvements and training induced plasticity in hippocampus and cingulum in a rat model of mild traumatic brain injury: a diffusion MRI study

Traumatic brain injury (TBI) is a major cause of long-term cognitive deficits, even in mild TBI patients. Computerized cognitive training can help alleviate complaints and improve daily life functioning of TBI patients. However, the underlying biological mechanisms of cognitive training in TBI are not fully understood. In the present study, we utilised for the first time a touchscreen cognitive training system in a rat model of mild TBI. Moreover, we wanted to examine whether the beneficial effects of a cognitive training are task-dependent and selective in their target. Specifically, we examined the effect of two training tasks, i.e. the Paired Associate Learning (PAL) task targeting spatial memory functioning and 5-Choice Continuous Performance (5-CCP) task loading on attention and inhibition control, on the microstructural organization of the hippocampus and cingulum, respectively, using diffusion tensor imaging (DTI). Our findings revealed that the two training protocols induced similar effects on the diffusion MRI metrics. Further, in the TBI groups who received training microstructural organization in the hippocampus and cingulum improved (as denoted by increases in fractional anisotropy), while a worsening (i.e., increases in mean diffusivity and radial diffusivity) was found in the TBI control group. In addition, these alterations in diffusion MRI metrics coincided with improved performance on the training tasks in the TBI groups who received training. Our findings show the potential of DTI metrics as reliable measure to evaluate cognitive training in TBI patients and to facilitate future research investigating further improvement of cognitive training targeting deficits in spatial memory and attention.

Age, but not severity of injury, mediates decline in executive function: Validation of the rodent touchscreen paradigm for preclinical models of traumatic brain injury

Increasingly, it is being recognised that traumatic brain injury (TBI) is not just an acute event but instead results in ongoing neuronal injury that may lead to chronic impairments in multiple cognitive domains. Of these, deficits in executive function are one of the more common changes reported following TBI, and are a major predictor of well-being, social function and quality of life in individuals with a history of TBI. In order to fully understand the relationship between TBI and executive dysfunction, including brain mechanisms that may account for this, experimental models are clearly needed. However, to date, there have been a lack of preclinical studies systematically comparing the effect of injury severity on executive function, particularly at long-term timepoints post-injury. Furthermore, many previous studies have not used behavioural measures that are sensitive to the full range of executive function impairments that may manifest after injury, particularly in models of diffuse axonal injury (Lv et al.). The current study aimed to investigate the temporal profile, up to 12 months post-injury, of the evolution of executive dysfunction following different severities of injury in an experimental model of DAI. In order to do so, we utilised a rodent touchscreen paradigm to administer the 5 Choice- Continuous Performance Task (5C-CPT), an extension of the 5-choice serial reaction time task (5CSRT). Interestingly, there were no differences in learning, motivation, attention, response time or impulsivity at 1 month, 6 months or 12 months post-injury in any of the TBI groups compared to sham, regardless of the initial severity of the injury. Instead, most of the effects on executive function seen at the 12 month timepoint appeared to be a result of ageing, not injury. As even the 12-month timepoint represents middle age in the rat, future studies will be needed to further probe these effects, in order to determine whether DAI may influence the presentation of executive dysfunction in older age.

An automated home-cage-based 5-choice serial reaction time task for rapid assessment of attention and impulsivity in rats

RATIONALE

The 5-choice serial reaction time task (5-CSRTT) is a widely used operant task for measuring attention and motor impulsivity in rodents. Training animals in this task requires an extensive period of daily operant sessions. Recently, a self-paced, automated version of this task has been developed for mice, which substantially reduces training time. Whether a similar approach is effective for rats is currently unknown.

OBJECTIVE

Here, we tested whether attention and impulsivity can be assessed in rats with a self-paced version of the 5-CSRTT.

METHODS

Operant boxes were connected to home-cages with tunnels. Two groups of rats self-paced their training by means of an automated script. The first group of animals was allowed unlimited access (UA) to start trials in the task; for the second group, trial availability was restricted to the first 2.5 h of the dark cycle (TR). Task parameter manipulations, such as variable inter-trial intervals and stimulus durations as well as pharmacological challenges with scopolamine, were tested to validate the task.

RESULTS

Self-paced training took less than 1 week. Animals in the UA group showed higher levels of omissions compared with the TR group. In both protocols, variable inter-trial intervals increased impulsivity, and variable stimulus durations decreased attentional performance. Scopolamine affected cognitive performance in the TR group only.

CONCLUSIONS

Home-cage-based training of the 5-CSRTT in rats, especially the TR protocol, presents a valid and fast alternative for measuring attention and impulsivity.

Housing and testing in mixed-sex rooms increases motivation and accuracy during operant testing in both male and female mice

Operant behavior tasks are widely used in neuroscience research, but little is known about how variables such as housing and testing conditions affect rodent operant performance. We have previously observed differences in operant performance in male and female mice depending on whether mice were housed and tested in rooms containing only one sex versus rooms containing both sexes. Here, male and female mice in either single-sex or mixed sex housing rooms were trained on fixed ratio 1 (FR1) and progressive ratio (PR) tasks. For both sexes, animals in the mixed sex room had more accurate performance in FR1 and were more motivated in the PR task. We then moved the single sex housed animals to the mixed sex room and vice versa. Animals that started in mixed sex housing had no change to PR, but both sexes who started in single sex housing were more motivated after the switch. Additionally, the females that moved into single-sex housing performed less accurately in FR1. We conclude that housing and testing conditions can affect performance on FR1 and PR tasks. As these tasks are commonly used as training steps to more complex tasks, housing and testing conditions should be carefully considered during experiment design and reported in publications.

Touchscreen Sustained Attention Task (SAT) for Rats

Sustained attention is the ability to monitor intermittent and unpredictable events over a prolonged period of time. This attentional process subserves other aspects of cognition and is disrupted in certain neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. Thus, it is clinically important to identify mechanisms that impair and improve sustained attention. Such mechanisms are often first discovered using rodent models. Therefore, several behavior procedures for testing aspects of sustained attention have been developed for rodents. One, first described by McGaughy and Sarter (1995), called the sustained attention task (SAT), trains rats to distinguish between signal (i.e., brief light presentation) and non-signal trials. The signals are short and thus require careful attention to be perceived. Attentional demands can be increased further by introducing a distractor (e.g., flashing houselight). We have modified this task for touchscreen operant chambers, which are configured with a touchscreen on one wall that can present stimuli and record responses. Here we detail our protocol for SAT in touchscreen chambers. Additionally, we present standard measures of performance in male and female Sprague-Dawley rats. Comparable performance on this task in both sexes highlights its use for attention studies, especially as more researchers are including female rodents in their experimental design. Moreover, the easy implementation of SAT for the increasingly popular touchscreen chambers increases its utility.