Lecture 4 in Stress and animal health

What does brain size and composition reflect?

Processing power.

Why do we use brain size as a proxy for processing power?

Because larger brains are generally associated with greater cognitive abilities.

Domestication Syndrome

A set of traits including larger size, paler coloration, reduced fearfulness, and smaller brains in domesticated animals.

What is brain size often correlated with?

Sentience(Förmågan att känna, uppfatta och att vara medveten).

Spatial learning test

A test used to assess cognition in chickens by having them learn which alley leads to a food reward.

How does stress affect cognitive performance in chickens?

Chickens exposed to an unpredictable light schedule (stressed group) showed impaired cognitive performance compared to those raised under a normal 12:12 light-dark rhythm (control group).
Cognition was tested using a spatial learning test, where birds had to learn which alley led to a food reward.
Stressed chickens required more attempts to solve the task, indicating that stress negatively impacts learning ability.

Direct brain measures

Techniques that provide information about how animals perceive and respond to their environment, often difficult to perform without harm.

Examples of direct brain measures

• Electrodes

• Postmortem brain measures

• MRI.

How do dogs' brains respond to human faces compared to everyday objects?

When dogs were shown pictures of human faces, brain activity increased significantly in several regions.
In contrast, no significant brain activity change occurred when they were shown everyday objects.

Brain lateralization

The specialization of the left and right brain hemispheres for different types of behavior and information processing.

What does the left hemisphere control?

Well-established behaviors in non-stressful situations.

What does the right hemisphere control?

Responses to unexpected stimuli and emergency behaviors.

How do cows respond to novel, fear-inducing stimuli?

They use the left eye, indicating fear.

What does left-eye preference in horses indicate?

Reactivity and coping style/personality.

Brain regression hypothesis

According to this hypothesis, domesticated (and therefore less fearful) animals adaptively reduce the brain size in order to reallocate energy and resources to traits such as reproduction. Believed to reflect the reduced functional needs of domesticated animal’s brains.

Are brain size and body size genetically constrained in chickens?

Brain size and body size are not strickly constrained =

Body size can increase in size without leading to the same increase in brain size

Cerebellum

The most neuron-dense brain region, involved in voluntary tasks and cognitive processing.

What are some welfare concerns and cognitive abilities observed in chickens?

• Chickens are the most widely farmed animal globally and often suffer from poor welfare.

• Despite this, chickens show remarkable cognitive abilities:

  • Can do math and geometry

  • Memorize up to 100 human faces and recognize other chickens

  • Have unique personalities

  • Use logic and complex social tactics

  • Show self-control and can delay gratification

  • Possess an extensive vocal repertoire