Documentation

The Cognitive Bias Apparatus is used in the assessment of emotional/cognitive states of rodents based on their cognitive bias. In simple terms, cognitive bias may be considered a deviation from the norm; judgment and decision-making by individuals are influenced by their own experiences and preferences rather than rationality. Cognitive biases in humans are influenced by a range of factors, including memory and affective states. Thus, exploring cognitive biases provides insights into the relationship between emotional state and cognitive processing.

The Cognitive Bias Apparatus uses association-based learning to investigate the influence of cognitive bias on decision making. The apparatus consists of a two-chamber set-up with a tunnel connecting the chambers. One of the chambers acts as the start box, while the other as the goal box. The goal box consists of two foraging bowls, that have distinct color and odors (scented sand), placed in either corner of the back wall. The task relies on the subject learning the association between the grade of sandpaper placed in the connecting tunnel with the high reward foraging bowl. The subjects which approached the task rationally are observed to opt for the bowl that was previously highly rewarded when tested using an ambiguous stimulus in the tunnel.

Understanding cognitive biases are helpful in developing therapeutic treatments for diseases and disorders that affect the emotional states of individuals to improve the quality of living. Additionally, the Cognitive Bias Apparatus may also be used in the evaluation of learning and memory impairments using rodent models. The apparatus can further be applied in studies of animal welfare research.

Other sensory system-based apparatuses include the Gap Cross Test, the Angle Entrance Task, and the Odor Span Test. Association learning-based assays include the Fear Conditioning Chamber, the Conditioned Place Preference Chamber, and the Five Choice Serial Reaction Time Task Chamber.

The Cognitive Bias Apparatus is composed of two, 61 cm x 43.5 cm x 21.5 cm, Perspex boxes that serve as the start box and the goal box. A 10 cm diameter tunnel having a length of 80 cm connects the two boxes. The tunnel can be lined with the stimulus of choice. Two foraging bowls (9 cm diameter, 5 cm height) of different colors are placed at the left and right ends of the goal box.

Clean the apparatus before and after every trial to prevent the influence of any odor cues from previous trials. Appropriately light the apparatus. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.

Habituation

Prior to the habituation session, familiarize the subjects with the food rewards to be used in the task for 10 minutes daily for 5 days.

Once the reward familiarization is completed, begin apparatus habituation. Pair a bowl color with specific scented sand and location for each subject. Place the foraging bowls at the left and right ends of the goal box. Maintain the pairings and locations throughout the experiment. Line the inside of the tunnel with sandpaper different from the ones used in the experiment. Place the subject in the start box and allow the subject to explore the apparatus for 5 mins a day for 5 days.

Pre-training

Pair rewards with their corresponding sandpaper grade and bowl. Maintain the pairing throughout the session.

Begin trials by placing the reward above the scented sand in its associated bowl. Place no reward in the other bowl. Line the tunnel with the reward associated sandpaper. Place the subject in the start box and allow it to explore the maze and eat the reward. Gradually bury the rewards into the sand as trials progress until the rewards reach the bottom of the bowl. Conduct 4 trials per day, two trials with one reward, and two with the other. Conduct pre-training sessions for 5 days.

Cognitive Bias Maze Task

Perform trials in the same manner and combination as the pre-training with rewards buried at the bottom of the bowl. For one randomly selected trial per day, do not place any rewards in the foraging bowl. Conduct trials until the subject meets the criterion for 5 consecutive days.

Cognitive Bias Probe Trials

Perform trials in the same manner as normal training. However, for the randomly selected unrewarded trial line, the tunnel with ambiguous grade sandpaper different from those previously used. Conduct trials for 5 consecutive days

Investigation of the effects of chemotherapy-induced intestinal mucositis on the affective state of rats

George et al. (2018) investigated the affective state of male Sprague Dawley rats with chemotherapy-induced intestinal mucositis using the Cognitive Bias Apparatus. Sixty rats were divided into three treatment groups:  saline (n=20), 5-fluorouracil (5-FU) (n= 19), and 5-FU + buprenorphine (n=19). On day 0, rats in saline and 5-FU groups were injected intraperitoneally with 5-FU (150 mg/kg) or saline, while rats in 5-FU + buprenorphine treatment group were injected subcutaneously with 0.05 mg/kg buprenorphine. Buprenorphine was administered at 12-hour intervals for the duration of the study. Judgment bias was measured 24 hours prior to 5-FU and saline injection (day 0), 72 hours post-injection (day 3), and 120 hours post-injection (day 5).  Each rat received a random combination of sandpaper, reward, and bowl, which was maintained throughout the study. Sandpaper grades coarse (P80) and fine (P1200) were used for the association, while intermediate (P180) grade sandpaper was used as the ambiguous stimulus for probe trials. Foraging bowls were blue, and brown color and coriander and cinnamon-scented sand were used during the experiment. Chocolate and Cheerios were used as high-positive and low-positive rewards, respectively. Results indicated that the rats administered 5-FU and buprenorphine exhibited significantly fewer optimistic decisions compared to those that were administered with saline alone. No differences between optimistic decisions were observed prior to the administration of the three treatments. Significant differences were observed 72 hours post-injection with 5-FU-injected rats exhibiting decreased optimistic decisions as compared to the other two treatment groups. No significant differences were observed in the number of optimistic decisions made between the three treatment groups at 120 hours post-injection.

Investigation of differences in cognitive bias between male and female rats following psychological stress

Barker, Bobrovskaya, Howarth, and Whittaker (2017) investigated sex-based cognitive bias differences following housing changes. Thirty male and 30 female Sprague Dawley rats were used in the experiment. Initially, animals were housed in open-top cages lined with paper-based bedding and furnished with cardboard boxes and PVC pipes as enrichment. During the final testing phase in the Cognitive Bias Apparatus, half of the subjects (15 each of male and female) were moved to metabolic cages with a metal grid and no shelter. Sandpaper grades coarse (P80) and fine (P1200) were used for the association, while intermediate (P180) grade sandpaper was used as the ambiguous stimulus for probe trials. Foraging bowls were blue and brown color, and coriander and cinnamon-scented sand were used during the experiment. Milk chocolate baking chips and Cheerios were used as high-positive and low-positive rewards, respectively. Each subject was randomly assigned an association between the reward items and reward locations, which were counterbalanced between sex and treatment. The results indicated that there was a significant interaction between sex and housing on the number of days for optimistic responses. Female rats in standard housing showed a reduced number of optimistic responses as compared to males in standard housing across training. However, no differences in the number of optimistic responses were observed between the two sexes when housed in metabolic cages. A significant difference was seen between the two housing conditions, with both male and female rats having a greater number of optimistic decisions in standard housing.

Investigation of the effects of metabolic cage housing on the cognitive bias of rats

Barker, Howarth, and Whittaker (2016) investigated whether rehousing rats into a metabolic cage would have an impact on their affective state. Twelve male and 12 female Sprague Dawley rats were tested on the Cognitive Bias Apparatus. The inner surface of the tunnel was lined with either coarse (P80) or fine (P1200) sandpaper based on association pairing, and with intermediate (P180) sandpaper during probe trials. A blue or brown bowl containing cinnamon or coriander scented sand was placed in the goal box. Milk chocolate baking chips and cheerios were used as high-positive and low-positive rewards, respectively. Each subject was randomly assigned an association between the reward item, bowl color, and location of the bowl, which was counterbalanced between sexes and treatment groups. All of the rats were housed in same-sex groups of 3 in open-top cages lined with paper bedding and furnished with a chewing object. During the last stage of training, the subjects were equally divided into two treatment groups (control and metabolic cage) and retested on the apparatus. The control group was housed in the same standard housing while the other group was housed in metabolic cages with a metal grid and no shelter. Results indicated that the males that remained in standard housing displayed more optimistic behaviors as compared to the males that were moved to metabolic cages. No significant differences were observed in optimistic behaviors between females from the two treatment conditions, and between males and females from the standard housing condition. However, significant differences were seen between males and females from the metabolic treatment condition. During probe trials, male rats from the metabolic cage treatment took a significantly greater time to initiate foraging behavior compared to females. However, no significant differences were observed between male and female rats from the standard housing condition. Foraging behavior was also affected by rewards, with the subjects taking the most amount of time to initiate foraging behavior for the cheerios reward. Overall results indicated that the males housed in the metabolic cages had a significantly greater number of pessimistic responses as compared to the males from the standard housing treatment. In contrast, females were not affected by treatment and showed similar results in both housing conditions.

Investigation of the effects of juvenile stress on cognitive bias in adulthood

Brydges et al. (2012) investigated whether stress experienced in juvenile rats affected cognitive bias into adulthood. Twenty-four male and female Lister Hooded rats were used in the study. The subjects were equally divided into two treatment groups: control and juvenile stress groups. The juvenile stress rats were exposed to a variety of short-term stressors at the juvenile phase that consisted of swim stress (see Forced Swim Test), restraint stress (for restrainers click here), and mild electric foot shocks, on post-natal days 25, 26 and 27. The subjects’ performances were evaluated on the Cognitive Bias Apparatus (aged approximately 99 days) and the Elevated Plus Maze (aged approximately 83 days). In the Cognitive Bias Apparatus, white chocolate drops (high-value) or Honey Nut Cheerios (low-value) were placed in black or white foraging bowls containing cinnamon or coriander scented sand. Half of the rats from each treatment group were trained using coarse (P60) sandpaper along with the chocolate rewards, while the other half were trained using fine (P1200) sandpaper with the Cheerios reward. During the probe trials, the tunnel was lined with an intermediate texture (P180). The juvenile stressed group was observed to make more optimistic choices than the control group. Additionally, the stressed group was faster in taking the decision in both regular and probe trials in comparison to the controls. It was also observed that females learned the task faster than males and mostly made correct choices. However, in comparison to the performances of males in the ambiguous probe and regular trials, females were slower in the ambiguous trials. Based on the performances in the Elevated Plus Maze, juvenile stressed animals displayed higher anxiety levels as observed by the significantly less time spent on the open arms.

Investigation of the effects of environmental enrichment on cognitive bias in rats

Brydges, Leach, Nicol, Wright, and Bateson (2011) investigated whether rats would display a positive cognitive bias after environmental enrichment using the Cognitive Bias Apparatus. Twelve male Sprague Dawley rats of approximately 6 months of age were used in the experiment. The inner surface of the apparatus tunnel was lined with either coarse (P60) or fine (P1200) sandpaper based on the association pairing. The foraging bowls were either white or black in color and contained coriander or cinnamon-scented sand. White chocolate and Honey Nut Cheerios were used as high value and low-value rewards, respectively. Each subject was randomly assigned an association between a reward, a particular bowl color, scented sand, and location of the bowl in the goal box. After probe trials involving intermediate (P180) sandpaper, the rats were divided into enriched and unenriched treatment groups. The enriched group was moved into a larger, plastic-based metal cage lined with wood shavings and contained enrichment while the unenriched group was moved to a cage that was identical to their old one but contained no environmental enrichment. The subjects were retested using the Cognitive Bias Apparatus after a week. During pretreatment, there was no significant difference between optimistic choices between the two treatment groups. However, it was observed that the enriched group displayed significantly greater optimistic responses post-treatment as compared to the un-enriched group.

The following can be observed using the Cognitive Bias Apparatus:

• Time taken to choose a bowl during regular trials
• Time taken to choose a bowl during ambiguous trials
• Number of times subject choose the high-value reward bowl
• Number of times subject choose the low-value reward bowl
• Time spent in the tunnel

Strengths

The Cognitive Bias Apparatus is useful in the investigation of the effects of emotional states on decision making and cognitive processing. The apparatus uses a simple two-choice set-up that utilizes the sensory cues in assessing cognitive bias. The two boxes in the apparatus, start and goal box, are connected with a tunnel which provides the opportunity to place different tactile stimulus as the inner lining. The task, in addition to the tactile stimulus, also allows the use of olfactory cues by the placement of scented sand in the different colored foraging bowls. Together, these cues allow the creation of different combinations of stimuli pairings for association-based learning. Simple modifications such as using opaque or clear boxes make the apparatus versatile for different investigations. The Cognitive Bias Apparatus assay can be used as a translational tool for diseases and disorders in humans and may be used to provide novel therapeutics.

Limitations

Training of the subjects in the Cognitive Bias Apparatus takes a substantial amount of time. Since the task uses food rewards, changes in the reward quality or quantity, as well as the motivation of the subjects, can affect performances. The task relies on sensory perception; thus sensory impairments will impact performances. Factors such as age, gender, and strain of the subjects may affect task performance. Exploratory behavior of the subjects may affect task performance. Unintentional stimuli may interfere with the way the subject performs the task.

• The Cognitive Bias Apparatus can be used in the assessment of emotional/cognitive states based on cognitive biases.
• The Cognitive Bias Apparatus consists of a start box that is connected to a goal box via a tunnel. The goal box consists of two differently colored foraging bowls.
• The lining of the tunnel, the colors of the bowls, and the scented sand used allow different association combinations for the task.
• Changes in the reward quality and quantity may affect performances.
• The cognitive bias task relies on sensory cues; thus, it is not suitable for animals with sensory defects or impairments.

1. Barker, T. H., Bobrovskaya, L., Howarth, G. S., & Whittaker, A. L. (2017). Female rats display fewer optimistic responses in a judgment bias test in the absence of a physiological stress response.Physiology & behavior, 173, 124-131. doi:10.1016/j.physbeh.2017.02.006
2. Barker, T. H., Howarth, G. S., & Whittaker, A. L. (2016). The effects of metabolic cage housing and sex on cognitive bias expression in rats. Applied Animal Behaviour Science, 177, 70-76. http://dx.doi.org/10.1016/j.applanim.2016.01.018
3. Brydges, N. M., Hall, L., Nicolson, R., Holmes, M. C., & Hall, J. (2012). The effects of juvenile stress on anxiety, cognitive bias and decision making in adulthood: a rat model. PLoS One, 7(10), e48143. doi:10.1371/journal.pone.0048143
4. Brydges, N. M., Leach, M., Nicol, K., Wright, R., & Bateson, M. (2011). Environmental enrichment induces optimistic cognitive bias in rats. Animal Behaviour, 81(1), 169-175. doi:10.1016/j.anbehav.2010.09.030
5. George, R. P., Barker, T. H., Lymn, K. A., Bigatton, D. A., Howarth, G. S., & Whittaker, A. L. (2018). A judgement bias test to assess affective state and potential therapeutics in a rat model of chemotherapy-induced mucositis. Scientific reports, 8(1), 8193. DOI:10.1038/s41598-018-26403-7