Brain and Behavior: An Introduction

An Introduction to Brain and Behaviour

• The cerebral cortex is the heavily folded outer layer of brain tissue
• This area is composed of neurons and it is also known as the "bark" of the brain
• The forebrain, prominent in mammals and birds, is responsible for most conscious behaviors
• The brainstem, a source of behavior in simpler animals, is responsible for most of our unconscious behaviors

Defining Behaviour

• Behaviour encompasses actions and mannerisms by individuals, organisms, systems, or artificial entities concerning themselves or their environment
• It includes other systems, organisms, and the physical environment
• Irenäus Eibl-Eibesfeldt defined behavior as patterns in time, which can include movements, vocalizations, changes in appearance, and thinking
• Innate behaviors are relatively fixed and invariant ways of responding
• Learned behaviors are flexible ways of responding

Perspectives on Brain and Behaviour: Mentalism

• Mentalism explains behavior as a function of the nonmaterial mind
• Aristotle believed the brain cooled the blood and had no role in producing behavior
• He proposed the Psyche, a synonym for mind, as the source of human behavior

Perspectives on Brain and Behaviour: Dualism and Criticism

• Dualism, as proposed by Descartes, suggests that a nonmaterial mind and the material body both contribute to behavior
• The mind-body problem questions how a nonmaterial mind can command a material body
• Dualism posits the mind directs rational behavior, while the body and brain direct other behavior via mechanical and physical principles
• Thought, and mind is located in the pineal gland in the brain, situated beside ventricles filled with fluid
• The mind regulates behaviour by directing the flow of ventricular fluid to the correct muscles
• Descartes' duelism faced problems as the pineal gland is involved in biological rhythms, not intelligence or behavioral control
• The theory also fails to account for the pineal gland's role in intelligence/behaviour, the lack of fluid pumping from ventricles, and also, fails to account for known physical laws
• Phineas Gage's case provided insight into the brain's role in behavior and personality

Perspectives on Brain and Behaviour: Materialism

• Materialism explains behavior as a function of the nervous system without resorting to the mind
• This view is supported by the evolutionary theories of Alfred Wallace and Charles Darwin
• Both Wallace and Darwin noted the similarities among different species
• Darwin's concept of natural selection explains how new and existing species change over time
• Differential reproductive success based on characteristics (phenotypes) interacting with the environment
• All animal species are related, so their neurons and brains share similarities
• This provides the rationale for studying simple animals to understand humans
• Animal species are related, and the same applies to behavior, including emotional expressions
• Brain and behavior evolved gradually in animals, leading to greater complexity as seen in humans

Donald Hebb's Correlation of Behavior and Neural Function

• Donald Hebb stated that behavior and neural function are perfectly correlated and causally linked
• He rejected the idea of a separate soul or life force influencing brain activity

Evolution of Brain Cells and Brains

• Brain cells and brains are relatively recent adaptations
• The first forms of life emerged 3.5 billion years ago
• The first brain cells appeared 700 million years ago
• The first brain developed 250 million years ago
• The first human-like brain emerged 3-4 million years ago
• Modern brains appeared between 100,000 to 200,000 years ago

Evolution of Nervous Systems

• Nerve nets consist of sensory and motor neurons
• Segmented nerve trunks have bilateral symmetry
• Ganglia are collections of nerve cells functioning like a brain
• Chordates are animals with a brain and spinal cord, where the notochord is replaced by the vertebral spinal column at birth.
• Behavioural complexity in chordates correlates with the evolution of cerebral hemispheres and the cerebellum
• Cerebellum: Located in the hindbrain, involved in coordinating motor and mental processes
• The increased size and folding allows more tissue into the skull

Features Common to Primates

• Excellent color vision and eyes in front of the face for enhanced depth perception
• Females typically have one infant per pregnancy
• Larger brains

Human Evolution: Hominids and Ancestors

• Hominids include all forms of humans, living and extinct, that walk upright
• Australopithecus, which means "southern ape", is a distant ancestor
  • Gave rise to the genus Homo, or human
  • Existed 4 million years ago in Africa and had brains that were 1/3 the size of ours
• Homo habilis, or "handy human", lived 2 million years ago in Africa and made simple stone tools
• The homo sapiens, or in other words, "wise human", evolved 200,000 years ago in Africa and Asia.
  • Evolved in Europe 100,000 years ago with a larger brain that H. erectus
  • Coexisted with hominids like H. neanderthalensis who had even larger brains than H. sapiens
• There is controversy over the H. floresiensis

Jerison (1973) and the Principle of Proper Mass

• Species with more complex behaviors will have relatively larger brains
• The Encephalization Quotient (EQ) measures brain size by comparing actual size to expected size based on body size
• Formula: EQ=w(brain)/Ew(brain), Ew(brain)=0.12w(body)2/3
• H. sapiens have the largest EQ

Primate Lifestyle and Brain Enlargement

• The foraging behavior of primates is complex
• Need good sensory, spatial, and memory skills

Changes in Hominid Physiology

• Radiator Hypothesis (Falk, 1990): The more active the brain, the more heat it generates
• This led to improved brain cooling, enabling increased hominid brain size
• Stedman and colleagues (2004) found that genetic mutations resulted in smaller facial muscles and bones
• The changing diets resulted in increased Brain size

Neoteny

• Rate of maturation is slowed, allowing for more brain cells to be produced
• Adults retain infant characteristics
• Newly evolved species look more like the young of their common ancestors
• Human heads resemble the heads of juvenile chimpanzees more than adult chimpanzees

Brain Size and Intelligence

• Brain size and intelligence do not seem to be particularly related
• People such as Einstein still had an average size brain
• Women’s brains weigh about 10% less than men, but the two sexes do not differ in average intelligence
• Culture: Learned behaviors are passed from one generation to the next through teaching and learning
• The Brain is flexible, using programming computers illustrates how brains perform new functions selected for evolutionary success