Chapter 1 Origins of Brain and Behavior Flashcards
What are the Origins of Brain and Behavior?
- Neuroscience in the Twenty-First Century
- Perspectives on Brain and Behavior
- Evolution of Brains and Behavior
- Evolution of the Human Brain and Behavior
- Modern Human Brain Size and Intelligence
Neuroscience in the Twenty-First Century
-Why Study Brain and Behavior?
- Many behavioral disorders can be explained and possibly cured by understanding the brain
- The brain is the most complex living organ on Earth
- How the brain produces both behavior and human consciousness are major unanswered scientific questions
This is the Brain: Cerebral Cortex
-Heavily folded outer layer of brain tissue composed of neurons (cortex = “bark”)
~The groves are called SUICI
~The bumps are called GYRI
This is the Brian: Right Hemisphere
-Forebrain
~Prominent in mammals and birds, responsible for most conscious behaviors (where we think)
-Brainstem
~Source of behavior in simpler animals, responsible for most of our unconscious behaviors (Breathing, heartbeat, and other things we do not think about)
Four Lobes of the Brain
-Frontal ~"Executive" functions, decision making -Parietal ~Integrates sensations into body coordinates -Temporal ~Hearing, language, memory, smell, taste -Occipital ~Visual processing
Gross Anatomy of the Nervous System
-The brain and the spinal cord together make up the central nervous system (CNS)
-All nerve processes and neurons outside the CNS connect to
~Sensory receptors
~Muscles
~Internal organs
-Central Nervous System (CNS)
~The brain and spinal cord
-Peripheral Nervous system (PNS)
~Somatic division
*Conveys sensory information to the CNS and motor information from the CNS to the muscles
~Autonomic division
*Enables the CNS to govern the workings of the internal organs (heartbeat, respiration, etc.)
Over all works
-Nervous System ~Central Nervous System (CNS) *Brain *Spinal Cord ~Peripheral Nervous System (PNS) *Somatic Nervous System *Autonomic Nervous System
What is Behavior?
-Irenaus Eibl-Eibesfeldt
~”Behavior consists of patterns in time”
~Examples
*Movement, vocalization, thinking
-Animals produce behavior that
~are inherited ways of responding
~that are learned
-Most behaviors probably consist of a mix of inherited and learned actions
-Relatively Fixed (Innate) Behavior
~Directly of heredity
*Eating, for crossbill birds, is a fixed behavioral pattern that is inherited and does not require much modification through learning
-Relatively Flexible behaviors
~Dependent of learning
*Roof rats can eat pinecones efficiently only if they are taught to do so my experienced parent
-Complexity of behavior varies considerably in different species
~Simple Nervous Systems -> Narrow Range of Behavior
*Nervous System (sea slug)
~Complex Nervous Systems -> Wider Range of Behavior
*Nervous Systems (humans)
Perspectives on Brain and behavior
-Aristotle and Mentalism
-Mentalism
~An explanation of behavior as a function of the nonmaterial mind
-Ancient Greece: Aristotle
~Believed the brain cooled the blood; no role in producing behavior
~Psyche
*Synonym for mind; an entity once proposed to be the source of human behavior
-The mind is a single entity having an autonomous existence
-The mind is completely and wholly separate from the body
-A manifestation of the soul that will survive the body’s death and return to the creator of your choice (Theological origins)
Descartes and Dualism
-Dualism
~both a nonmaterial mind and the material body contribute to behavior
~Mind-Body Problem
*Quandary of explaining a nonmaterial mind in command of a material body
-Rene Descartes
~Mind directs rational behavior
~Body and brain direct all other behavior via mechanical and physical principles
~Example
*Sensation, Movement, and Digestion
~Mind is located in the PINEAL GLAND of the brain, which sits beside ventricles filled with fluid
-Pineal Gland
~Sits in the back of the brain above the brain stem
~The mind regulates the behavior by directing the flow of ventricle fluid to the appropriate muscles
*This is a long time ago before they understood electricity, they did know about fluid dynamics
*The brain is filled with fluid as well as the spinal cord
-Problems with Descartes
~Pineal gland is involved in biological rhythms, but not in intelligence or behavior control
~Fluid is not pumped from the ventricles to control movement
~nonmaterial influences on the body would violate the law of conservation of matter and energy
Darwin and Materialism
-Materialism
~Behavior can be explained as a function of the nervous system without explanator recourse to the mind
~Related to evolutionary theories of Alfred Wallace and Charles Darwin
*Both were struck at the many similarities among species
-Darwin’s Concept of Natural Selection
~Explanation for how new species evolve and existing species change over time
-Different success in the reproduction’s of different characteristics (phenotypes) result from the interaction of organisms with their environment
-Because all animal species are related, so too must be their brains
-Because all species of animals are related, so do must be their behaviors
-Can study and understand human behavior and brain function by comparing the genes, brain, and behaviors of different animals
How are Traits Selected Naturally?
-Appearance of New Trait ~Via mutation -Trait Increases Reproductive Success -Increases Change of Survival -Trait Passed on to Offspring
Epigenetics
- Study of differences in gene expression related to environment and experience
- Epigenetic factors do not change your genes express the traits you’ve inherited from your parents
- Epigenetic changes can persist throughout a lifetime, and the cumulative effects can make dramatic differences in how your genes work
Evolution of Brains and Behavior
-Common Ancestor
-A forbearer which two or more lineages or family groups arise
-Example
~Humans and apes are thought to share a common ancestor
-Can trace out lineage by comparing the genes, brains, and behaviors of different animals
Evolution of Brain and of Behavior
-Origin of Brain Calles and Brains
-Despite the age of the Earth (4.5 billion years), brain cells and brains are quite recent adaptations
~First form of life: 3.5 billion years old
~First brain cell: 70 million years ago
~First human-like brain: 6 million years ago
~Modern human brain: 200,000 years ago
Taxonomy of Modern Humans
-The evolution of brain cells and the brain
~Only Animalia, contains species with muscles and nervous systems
~Muscles and nervous systems evolved together to underlie the forms of movement (behavior) that distinguish members of the animal kingdom
*Study where humans fit in taxonomy
Evolution of Brain and Behavior
-Evolution of Animals Having Nervous Systems
-Five different Kingdoms ~Monera *Bacterial ~Protist *Single Cells ~Plantae *Plants ~Fungi *Fungi ~Animalia *Animals -Animals are closer related to fungi than any other kingdom -Only Animals have nervous systems ~Other kingdoms can react to their environment, but do NOT have a brain or nervous system
Evolution of Animals Having Nervous Systems
-Among the various animal phyla, the nervous system has evolved considerably
-Nerve Net
~Simple nervous system with sensory and motor neurons
-Segmented nerve trunk
~Bilaterally symmetrical (the same on both sides of the body)
~Segmented (divided into a number of parts)
-Ganglia
~Structure that resemble and function somewhat like a brain
-Brain
~The chordate phylum display the greatest degree of encephalization: they have a true brain
~Of all the chordates, humans have the largest brain relative to body size
Chordate Nervous System
-Nervous systems vary widely among chordates, but all are/have
~Bilaterally symmetrical and segmented
~Brain and spinal cord incased in cartilage/bone
~”Crossed” organization: Each hemisphere receives information from and controls the opposite side of the body
-Emergence of complex behavior^ in chordates is l related to the evolution of the cerebrum and cerebellum
^ New forms of locomotion on land, complex movements of the mouth and hands for eating, improved learning ability, and highly organized social behavior
Humans: Members of the Primate Order
-Features common to primates
~Excellent color vision
~Eyes in front of face enhance depth perception
~Females: Usually only one infant per pregnancy; infants require more care
~Large brains for skilled movements and social behavior
-Humans and chimpanzees share a common ancestor 5-10 million years ago
-Hominids
~Evolved 5 million years ago
-Primates that walk upright; includes all forms of humans, living and extinct
Australopithecus: Our Distant Ancestor
-Early hominids were among the first primates to show distinctly human characteristics, including walking upright and using tools
~Its brain was the size of that of a modern ape, about one-third the size of the modern human brain
First Humans
-Homo habilis (“handy human”)
~2 million years ago; Africa
~Made simple stone tools
-Homo erectus (“upright human”)
~1.6 million years ago; in Europe and Asia
~More sophisticated tools than homo habilis
-Homo sapiens
~Appeared within the last 200,000 years
~Until 30,000 years ago in Europe and 18,000 years ago in Asia, coexisted with other hominid species
~Example
*Neanderthals in Europe, who had comparable or even larger brains than Homo Sapiens
~Exact reason why we replaced Neanderthals is unknown
Hominid Brain Size
-The brain of Australopithecus was about the same size as that of living nonhuman apes, but succeeding members of the human lineage display a steady increase in brain size
Relating Brain Size and Behavior
-Jerison (1973)
~Principle of Proper Mass:
*Species exhibiting are complex behaviors will possess relatively larger brains
~Jerison developed an index of brain size to allow comparisons among different species
*Used body size to predict brain size
-Encephalization Quotient (EQ)
~Measure of brain size obtained from the ratio of actual brain size to the expected brain size for an animal of a particular body size
*Homo sapiens have the largest EQ
Enlarging Hominid Brain
-Relative size of the hominid brain has increased nearly threefold
~Australopithecus afarensis (smallest brain size)
~Homo erectus (larger brain size)
~Modern Homo sapiens (largest brain size)
Climate and the Enlarging Hominid Brain
-Evidence suggests each new hominid species appeared after new environments appeared due to climate changes
-Example
~Spreading grasslands and fewer trees increased the adaptiveness of an upright posture and tool-building skills
Why the Hominid Brain Enlarged
-The Primate Lifestyle
~The foraging behavior of primates is more complex than that of other animals
*Finding fruit is more difficult than eating grass or other vegetation on the ground
**Need good sensory, spatial, and memory skills
*Fruit eaters have larger brain
-Changes in Hominid Physiology
~Radiator Hypothesis (Falk, 1990)
*The more active the brain is, the more heat it generates
*Homo species’ skills had more widely disappeared blood flow, which allowed for increased brain size
**Increased Blood Circulation -> Improved Brain Cooling -> Enabled Size of Hominid Brains to Increase
*The brain uses about 70% of the bodies blood glucose supply
**Over 2/3 of the bodies sugar gets consumed by the brain and the other 1/3 is used by the rest of the body
* The brain uses about 25% of the bodies O2
-Changes in Hominid Physiology
~Stedman and Colleagues (2004)
* Genetic Mutation -> Smaller Facial Muscles and Bones -> Change in Diet -> Increase Brain Size
-Neoteny
~Rate of maturation is slowed
*Allows more brain cells to be produced
~Adults retain some infant characteristics
~Newly evolved species resemble the young of their common ancestors
*Adult human heads look more like the heads of juvenile chimpanzees than adult chimpanzees
Modern Human Brain Size and Intelligence
-Evolutionary Approach
~Make brain-behavior comparisons between different species
-CAUTION
~Difficult to make brain-behavior comparisons between members within the same species
~Example
*Brain size and intelligence
-Are people with larger brains more intelligent?
~Problems with answering this question:
*Control for skull thickness
*Volume versus weight
*Control for body weight
**Can fluctuate within an individual over time
*Effect of age, physical health, brain damage?
-Problem of Causality
~Large Brain Size -> Greater Intelligence
~Greater Intelligence -> Large Brain Size
~Other Variables -> Large Brain Size
~Other Variables -> Greater Intelligence`
