Effects of Experience and Environment on the Developing and Mature Brain: Implications for Laboratory Animal Housing. ILAR 39(1), 005.
Abstract: This is a review article that deals primarily with the effects of enriched environments on brain development. The main part of the article deals with what the author terms as experience-expectant information storage and experience-dependent information storage.
Experience-expectant information storage is the special sensitivity of the developing nervous system to experience. The author uses the example of visual development. There is a critical or sensitive period when normal visual experience must occur is normal vision is to develop, and this occurs in the visual cortex of the brain. Once this experience has occurred, the system becomes nearly invulnerable to deprivation. During development, the visual cortex overproduces the synaptic connections through which nerve cells communicate and the numbers peak within the sensitive period for experiential organization. As experience "tunes a functional system, a subset of of these connections is strengthened while the remainder is pruned away. This makes a loss of synapses essential to the development of a functional visual system.
Experience-depependent information storage is lifelong information storage in the brain. One mechanism for this is the formation of new synapses in response to experience. Rats from enriched
conditions(EC) outperform those fron non-enriched environments. It was also found that rats reared in EC have larger dendritic fields and more synapses per neuron, as well as lowered body weights, slowed growth of certain organs and bones. The total surface area of astrocytes per neuron is greater and the glia envelop synapses more thoroughly in EC rats and these rats showed that the capillary volume per nerve cell is 80% greater. The immune system function appears to be enhanced in EC rats compared to those housed in standard cages. Thus, the anatomy and physiology of the brain vary with the type of housing and this may produce effets on research. The author also found that the electrical potential from the visual cortex of EC rats was higher than other rats.
The author points out that these findings have also occurred in mice, cats and monkeys, but did not occur in pigs so that different species resond to environmental conditions in different ways.
1. T/F: Rats from enriched environments have more neruons than rats from standard caging.
2. Replicating work between labs can be very difficult if the __________________ are not also replicated.
1. False: They have more synapses.
2. Housing conditions.
Social Experience and Immune System Measures in Laboratory-housed Macaques: Implications for Management and Research. ILAR 39(1), 012.
Abstract: In this study, the author discusses (1) immune system-
related meaures as a useful indicator of an animal's internal
state,(2)social experience of macaques should be viewed more
broadly, (3) research results may suffer when social experience is
not taken into considerations and (4) individular differences with respect to social experience are important to consider.
The author found that previously separated animals had reduced
proliferation to 3 mitogens conpared to controls, and had 40%
higher total leukocyte numbers. Nursery reared(NR) animals
compared to Mother reared(MR)animals between 13-16 mo. of age had
enhanced immunological responses when assessed by mitogen responses
but did not have better health as the NR monkeys had a higher
incidence of gastrointestinal disorders. The author concluded that
the apparently permanent nature of these changes suugests the
important characteristics of the organization of the individual
have been altered by the rearing condition.
Relocation can also have effects on the immune system. 2yr.-old
Rhesus monkeys were removed from their large natal enclosures to
individual housing for 11 weeks and then returned showed
significant elevations in plasma cortisol that persisted for 8weeks, significant reductions in total lymphocyte
numbers(especialy CD4+) through 11 weeks and decreased weight gain
compared to controls. These data suggest that removal from a
social group and the later return to the group have significant
effects on the immune sytem.
The author also performed a retrospective study using records from
300 animals infect with SIV. He found that the number of
relocations in the 90-day period preceding SIV inoculation
significantly predicted survival, with animals having more
relocations showing reduced survival times. Aslo, having a
relocation occur sooner after inoculation, rather than later was
also associated with higher mortality. He also found that social
housing was important for survival: Pair/group housed(not mother-
infant) had a shorter survival time than did individually housed
animals. These pairs/group housing occured shortly before SIV
innoculation and after a period of individual housing, therefore social instability was associated with significantly faster disease
progression and higher mortality.
1. Nursery-reared macaques have an enhanced immune response
compared to mother-reared macaques, but did not have better
2. Name two social factors that have an impact on the immune
system of Rhesus macaques.
2. Rearing conditions, social housing/instability.
Why it is Important to Understand Animal Behaviour. ILAR 39(1), 020.
Abstract: This article provides an overview of the development of behavioral approaches to the study of animal welfare, reasons that behaviors are important to animals and how an understanding of behavior can be useful when designing housing for lab animals.
The Brambell report was the first published report emphasizing the importance of behavior in assessing animal welfare. This report concluded that animals had behavioral needs that must be provided for or else suffering could occur. Some of the methods used to study animal welfare include motivation, abnormal behaviors and stereotypies, preference testing and demand curves.
Behavior is defined as what animal do to interact with, respond to, and control their environment. The performance of certain behaviors can lead to imporvements in physical health. Ex.: caged hens given raised perches have greater leg-bone and wing-bone strength and better foot health. However, performing certain behaviors can have effects on normal physiological functions. Ex.: Suckling behavior of calves, even from a dry teat production of digestive enzymes and insulin was increased. Behaviors can influence research findings: ex.: housing had a significant effect on monkey survivability following infection with SIV.
Behaviors can reduce stress, illness, fear pain and tension. Ex.: mutual grooming in primates decreases stress and tension among socially interactive primates and is associated with the release of endogenous opiods.
Performing certain behaviors can have long-term effects. ex.: mice housed in partitioned cages had reduced stress and fear responses, greater weight gains, lower adrenal gland weights and lower fear scores. Animal that are able to exercise some behavioral control over their environment show attenuated responses to a stressor. Animals of many species prefer to work for food rather than eat freely available food(contrafreeloading).
Understanding behavior is important in designing effective environmental enrichment programs. ex.: Mongolian gerbils need a tunnel or else they will develop sterotypical digging behavior. It was demonstrated that it is not the digging that needs to be performed, but that providing an artifical tunnel will prevent the stereotypical behavior.
1. The study of animal behavior is called ________.
2. What are 3 reasons why behavior is important in animals?
2. a. Helps to maintain physical/psychological health
b. Helps reduce fear/stress
c. Provides pleasure/comfort/satisfaction
Psychoneuroimmunology. ILAR 39(1), 027.
Abstract: Psychoneuroimmunology is the study of the interactions among the behavioral, neural and endocrine, and immune functions. It emphasizes the study of the functional significance of the relationship between the nervous and immune systems and the significance of these interactions for health and disease.
Nervous-immune system interactions exist a different levels:
a. Primary: thumus, bone marrow
b. Secondary: spleen, lymph nodes, gut-associated lymphoid tissues
Primary & secondary are innervated by the sympathetic nervous system
c. Lymphoid cells: have receptors for hormones & neurotransmitters
There is data documenting an association between stressful life experiences and changes in immunologic reactivity. Bereavement and/or depression are associated with reduced lymphoproliferative responses adn impaired NK cell activity. Less severe stressful experiences result in transient impairments of immune function. Stress can alter the host's defense mechanisms which can precipitate clinical disease from latent organisms. The direction, magnitude and duration of stress-induced alterations of immunity are influenced, among other things, by:
a. quality & quantity of stressful stimulation
b. the capacity of the individual to cope effectively with stressful events
c. quality & quantity of immunogenic stimulation
1. Psychoneuroimmunology is the study of the interactions among what 3 components?
1. Behavior, neural and endocrine functions and immune functions.
Floor Space Needs for Laboratory Mice: C57BL/6 Males in Solid-bottom Cages with Bedding. ILAR 39(1), 030.
Abstract: This article was an attempt to use scientific method to determine the appropriate caging size for mice. The literature on which current recommendations are based were studying the effect of crowding, which confounds the effect of available space.
Measures of performance, mortality, adrenal weights, plasma glucocorticoid concentration, and selected immune measures were collected in an attempt to define space needs of laboratory mice. Six replications of 3 C57BL/6 male mice per cage were examined while housed on bedding at 5, 10, 15, or 20 in2 (32.2, 64.5, 96.8 or 129 cm2) per mouse. Body weights were not influenced by treatment; however, mice in smaller spaces (5 in2 per mouse) consumed or wasted more feed and water than mice given greater space allowances. Mice given the least amount of space (5 in2 per mouse) had greater lymphocyte proliferation in response to the T-cell mitogen PHA than mice given more space. Mice provided 10 in2 per mouse had greater NK cytotoxicity than mice given greater or less space. Mouse mortality was greater as more space was provided. In contrast, adrenal weights and plasma glucocorticoid concentrations were progressively greater with lower space allowances. The NRC 1996 recommendation of 15 in2 per mouse, for this strain and sex of mice, would result in greater mortality and reduced activity of some immune measures. Socially housed male C57BL/6 mice will benefit from less space than recommended by the NRC in 1996
Questions: 1. Which of the following were significantly higher in animals housed in 5 sq. cm. vs. 10 sq. cm. housing?
a. Food and water use
b. Adrenal size
d. NK activity
2. Why do the authors speculate that mortality was higher in the larger cages?
Answers: 1. a, b
2. They speculated that the mice tend to fight more, and that the submissive animals cannot get away.