Anxiety-induced cognitive bias in non-human animals

University of Bristol, Bristol, BS40 5DU, UK.
Physiology & Behavior (Impact Factor: 2.98). 07/2009; 98(3):345-50. DOI: 10.1016/j.physbeh.2009.06.012
Source: PubMed


As in humans, 'cognitive biases' in the way in which animals judge ambiguous stimuli may be influenced by emotional state and hence a valuable new indicator of animal emotion. There is increasing evidence that animals experiencing different emotional states following exposure to long-term environmental manipulations show contrasting biases in their judgement of ambiguous stimuli. However, the specific type of induced emotional state is usually unknown. We investigated whether a short-term manipulation of emotional state has a similar effect on cognitive bias, using changes in light intensity; a treatment specifically related to anxiety-induction. Twenty-four male rats were trained to discriminate between two different locations, in either high ('H') or low ('L') light levels. One location was rewarded with palatable food and the other with aversive food. Once the rats had shown spatial discrimination, by running significantly faster to the rewarded location, they were tested with three ambiguous locations intermediate between the rewarded and aversive locations, and their latency to approach each location recorded. Half the rats were tested in the same light levels as during training, the remainder were switched. Rats switched from high to low light levels (putatively the least negative emotional manipulation) ran significantly faster to all three ambiguous probes than those rats switched from low to high light levels (putatively the most negative manipulation). This suggests that the judgement bias technique might be useful as an indicator of short-term changes in anxiety for non-human animals.

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    • "r in which the ambiguous conditions were presented was also balanced across sessions to control for any order effects . Between trials the large compartment combinations were manipulated by removing and replacing the floor covers to transition to the combinations needed for the next trial . The goal pots in the ambiguous conditions were unbaited ( Burman et al . , 2009 ) . In the reward and aversive trials , rats were allowed to eat the available pellets until the conclusion of the trial , at which time the rat was removed from the apparatus . The CPP apparatus was wiped down with a 70% alcohol solution between each trial to remove any olfactory information left behind from the previous trial . Latenc"
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    ABSTRACT: The effect of oxytocin on cognitive bias was investigated in rats in a modified conditioned place preference paradigm. Fifteen male rats were trained to discriminate between two different cue combinations, one paired with palatable foods (reward training), and the other paired with unpalatable food (aversive training). Next, their reactions to two ambiguous cue combinations were evaluated and their latency to contact the goal pot recorded. Rats were injected with either oxytocin (OT) or saline with the prediction that rats administered OT would display a shorter average latency to approach on ambiguous trials. There was no significant difference between latencies to approach on ambiguous trials compared to reward trials, but the rats were significantly slower on the aversive compared to the ambiguous conditions. Oxytocin did not affect approach time; however, it was unclear, after follow-up testing, whether the OT doses tested were sufficient to produce the desired effects on cognitive bias. Future research should consider this possibility.
    Full-text · Article · Oct 2015 · Frontiers in Psychology
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    • "The objective of the present study was to classify pigs individually and to assess the consistency over time of individual CB by using a go or no-go spatial judgment task (Burman et al., 2009; Mendl et al., 2009) in pigs from the same sex and genotype, exposed to the same housing and management conditions. "
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    ABSTRACT: The aim of the study was to ascertain if the cognitive bias (CB) test can be used to assess pigs' emotional state and classify them individually. Moreover, the test was repeated over time to assess its consistency. Thirty-six male pigs were individually trained during 14 training sessions to discriminate between a bucket with (A) or without (NA) access to chopped apples depending on its position (left or right) in a test pen. Once pigs were able to discriminate between both positions, each animal was subjected to 2 A and 2 NA reminder sessions before performing the CB test session, where the bucket was placed on a central position with access to 2 pieces of apple. The trial was repeated after 5 weeks, reducing the number of training sessions to 4. Time to contact the bucket, time to eat (or try to eat in the case of NA sessions), number of vocalizations, number of times pigs were reluctant to move, number of escape attempts, and number of urination and defecation events were recorded. In the first trial, time to contact the bucket and time to eat was significantly lower in A than in NA from session 10 (P < 0.0012), indicating that pigs were able to discriminate between both positions. In the second trial, both variables were significantly lower in A compared to NA from session 2 (P < 0.005) onward, confirming the pigs' capacity to remember the task. Pigs were individually classified as having positive, negative, or neutral CB, according to the time to contact the bucket during the CB test session in comparison with the time taken during the remainder sessions. A large percentage of pigs were classified as positive CB in both trials (84.85% and 94.29%, respectively). However, there was no consistency between the results of both trials, suggesting that during the second CB test session animals were able to remember the content of the bucket of the first CB test session. Alternatively, other factors such as the time of the day that pigs were tested, the age of the animals, or their hunger state could have an effect on the results.
    Full-text · Article · Sep 2015 · Journal of Veterinary Behavior Clinical Applications and Research
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    • "It is becoming increasingly accepted that the capacity for anxiety has evolved as a regulatory mechanism for fear [2] [3] [4] [5] [6] [7]. Greater anxiety causes an individual to be alert to more subtle signs of potential danger, while lowered anxiety causes the individual to respond with fear only to more obvious signs [8]. As unpleasant as the experience of anxiety may be, the capacity for anxiety is beneficial because it allows an individual to modulate fearfulness according to current vulnerability. "
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    ABSTRACT: Normal anxiety is considered an adaptive response to the possible presence of danger, but it appears highly susceptible to dysregulation. Anxiety disorders are prevalent at high frequency in contemporary human societies, yet impose substantial disability upon their sufferers. This raises a puzzle: why has evolution left us vulnerable to anxiety disorders? We develop a signal detection model in which individuals must learn how to calibrate their anxiety responses: they need to learn which cues indicate danger in the environment. We study the optimal strategy for doing so, and find that individuals face an inevitable exploration-exploitation tradeoff between obtaining a better estimate of the level of risk on one hand, and maximizing current payoffs on the other. Because of this tradeoff, a subset of the population becomes trapped in a state of excessive and self-perpetuating anxiety, even when individuals learn optimally. This phenomenon arises because when individuals become too cautious, they stop sampling the environment and fail to correct their misperceptions, whereas when individuals become too careless they continue to sample the environment and soon discover their mistakes. We suggest that this process may be involved in the development of excessive anxiety in humans.
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