Neuroscience and Behavior

Everything psychological is also biological.

The brain is not completely understood.

How does our brain organize and communicate with itself?

How do our heredity and our experiences together wire our brain?

How do memories work in the brain?

Plato correctly located the mind in the spherical head.

Aristotle believed the mind was in the heart, which pumps warmth and vitality to the body.

Early 1800s – Franz Gall (German physician) invented phrenology – a popular but ill-fated theory that claimed bumps

on the skull could reveal our mental abilities and our character traits. Phrenology correctly focused attention on the

idea that various brain regions have particular functions.

In the last century, scientists have discovered that the body is made of cells. Nerve cells conduct electricity to “talk” to

one another by sending chemical messages across a tiny gap that separates them.

Biological psychology – a branch of psychology concerned with the links between biology and behavior.

Neural Communication

We are all biopsychological systems.

o We are each a system composed of subsystems that are in turn composed of even small subsystems

Neurons

Neuron – a nerve cell; the basic building block of the nervous system

o Building blocks of the neural information system

Dendrites – the bushy branching extensions of a neuron that receive messages and conduct impulses toward

the cell body.

Axon – the extension of a neuron, ending in branching terminal fibers, through which messages pass to other

neurons or to muscles or glands.

Axons speak, dendrites listen.

Myelin sheath – a layer of fatty tissue segmentally enhancing the fibers of many neurons; enables vastly

greater transmission speed of neural impulses as the impulse hops from one node to the next.

o protection

o speed

Axon terminal – branches at the end of an axon that send messages to the dendrites of another neuron

A neuron fires an impulse when it receives a signal from sense receptors or by chemical messages from

neighboring neurons.

o Action potential - a neural impulse down the axon

Neurons generate electricity from chemical reactions – involves the exchange of electrically charged atoms

(ions).

o fluid inside an axon = negatively charged ions.

o fluid outside an axon = positively charged ions.

o Positive/outside – negative/inside state is called the resting potential

Steps in chemistry to electricity change…

o Neuron receives chemical message

o Axon admits positively charged sodium ions through the membrane domino effect

o During a resting pause (refractory period) the axons recharge by pushing the positively charged ions back

outside then it can fire again.

Threshold – the level of stimulation required to trigger a neural impulse.

o All-or-nothing; fires or doesn't

How Neurons Communicate

Neurons are separated by gaps less than a millionth of an inch wide.

o Synapse – the junction between the axon tip of the sending neuron and the dendrite or cell body of the

receiving neuron; tiny gap called the synaptic gap or cleft.

Neurons communicate across the synaptic gap by using

neurotransmitters – chemical messengers that traverse the

synaptic gaps between neurons.

o When the action potential reaches the axon’s terminal

buttons, these branches release chemicals/neurotransmitters

that travel across the synaptic gap and bind/connect to

receptor sites on the receiving neuron’s dendrites - lock-

and-key relationship.

o When a neuron receives neurotransmitters the neuron will

fire and the action potential will travel down its axon.

Communication within the neuron - ELECTRICAL

Communication between neurons - CHEMICAL

How Neurotransmitters Influence Us

Different neurotransmitters are found in different parts of the brain.

Neurotransmitters also compel humans to feel and experience certain emotions/behaviors.

SOME NEUROTRANSMITTERS AND THEIR FUNCTIONS

Neurotransmitter Function Examples of Malfunction

Acetylcholine

(ACh)

Enables muscle action,

learning, and memory.

Alzheimer’s disease – ACh producing neurons deteriorate.

Dopamine Influences movement, learning,

attention, and emotion.

Excess dopamine receptor activity is linked to schizophrenia.

Too little dopamine in the brain can lead to Parkinson’s disease

(tremors and decreased mobility).

Serotonin Affects mood, hunger, sleep,

and arousal

Too little serotonin is linked to depression. (Anti-depression

drugs raise serotonin levels)

Norepinephrine Helps control alertness and

arousal

Too little can depress mood

GABA (gamma-

aminobutyric acid)

A major inhibitory

neurotransmitter

Too little can lead to seizures, tremors, and insomnia.

Glutamate A major excitatory

neurotransmitter – involved in

memory

Too much can overstimulate the brain – producing migraines or

seizures

A study in 1973 (on animals) showed that morphine (an opiate drug used to decrease pain and elevate mood)

bound to the same receptor sites in areas linked with mood and pain sensations why would the brain have

“opiate receptors” if it did not naturally produce opiate-like neurotransmitters?

o Endorphins – natural, opiate-like neurotransmitters linked to pain control and pleasure.

How Drugs and Other Chemicals Alter Neurotransmission

When the brain is flooded by certain neurotransmitters in the form of medication or drugs (cocaine, heroin,

morphine), it may naturally stop producing similar transmitters. When the medication or drug is withdrawn, the

brain may be deprived of any form of opiates until the brain can naturally start producing its own

neurotransmitters again.

o Explains the uncomfortable withdrawal period when a drug addict ceases using the drug.

Various drugs and substances can effect communication at the synapse, by exciting or inhibiting a neuron to fire.

o Agonist – molecules that are similar to neurotransmitters and can mimic their effects.

Eg: the venom of a black widow spider floods the brain with agonists similar to ACh which

results in muscle contractions, convulsions, and even death.

o Antagonist – a molecule that inhibits a neurotransmitter’s release

INTERACTIVE NEURON

Eg: Botulin (a poison in improperly canned food), causes paralysis by blocking the release of

ACh from the sending neuron.

The Nervous System

Nervous system – the body’s speedy electrochemical communication network, consisting of all the nerve cells

of the peripheral and central nervous systems. o Central nervous system (CNS) – the brain and spinal cord

o Peripheral nervous system (PNS) – the sensory and motor neurons that connect the CNS to the rest of

the body.

Nerves – part of the PNS; neural “cables” containing many axons; connect the CNS with muscles, glands, and

sense organs.

o Eg: the optic nerve is a bundle of millions of axon fibers that carry information from each eye to the

brain.

Information travels though the nervous system in 3 types of neurons.

o Sensory neurons – carry incoming information from the sense receptors to the CNS

o Interneurons – CNS neurons that internally communicate and intervene between the sensory inputs and

motor outputs

o Motor neurons – carry outgoing information from the CNS to the muscles and glands

The Peripheral Nervous System

Somatic nervous system – controls the body’s skeletal muscles

o Eg: Running, dancing, movement

Autonomic nervous system – controls the glands and the muscles of the internal organs; divided into the

sympathetic and parasympathetic nervous systems

o Eg: heartbeat, digestion, sweating

o Sympathetic nervous system – arouses the body

o Parasympathetic nervous system – calms the body

The Central Nervous System

The Spinal Cord and Reflexes

The CNS is the highway/connector between the brain and the PNS.

Sometimes, the body can react without the message having to travel all the way to the brain.

o Reflex – simple, autonomic, inborn response to a sensory stimulus, such as the knee-jerk response.

o Reflex pathway = 1 sensory neuron + 1 communication interneuron + 1 motor neuron

If the spinal cord were to be severed, no sensations could reach the brain and the brain could not send out any

information.

o Simple reflexes like the knee-jerk would occur, but without the feeling of the tap. Simple pain reflexes

would not occur. Pain would also not reach the brain. However, other simple reflexes, like sexual arousal,

may still occur. Each spinal injury is unique to its affected reflexes and senations.

Neurons, in the brain, cluster to work in groups to produce shorter, faster connections. Neurons can receive and

send information from and to many neurons at the same time.

o Neural networks – interconnected neural cells; with experience, networks can learn and strengthen

o Experience causes neural networks to grow and strengthen eg: practicing the piano builds neural

connections that help this behavior.

The Endocrine System

Endocrine System – the body’s “slow” chemical communication system; a set of glands that secrete hormones

into the bloodstream.

Hormones – chemical messengers, mostly those manufactured by the endocrine glands that are produced in

one tissue and affect another.

o Travel slowly through the bloodstream between tissues

o When hormones act on the brain, they can trigger interest in sex, food, and aggression.

Neurotransmitters : nervous system :: hormones : endocrine system.

The endocrine system tries to keep a balance in the body while we respond to feelings of stress, anger, fear,

exertion, etc.

Adrenal glands – a pair of endocrine glands above the kidneys; secrete the hormones epinephrine (adrenaline)

and norepinephrine (noradrenaline) which help to arouse the body in times of stress.

o Increase heart rate, blood pressure, and blood sugar that provide a surge of energy.

o Hormones and the feelings they produce can linger after the event which caused the release of the

hormone.

Pituitary gland – the endocrine system’s most influential gland; under the influence of the hypothalamus, it

regulates growth and controls other glands

o Pea-sized, in the core of the brain

o Controlled by the hypothalamus

o “master gland”

o Brain pituitary gland other glands hormones brain

The Brain

Tools of Discovery

Lesion – tissue destruction; can be naturally caused (accident, birth defect) or can be experimental

o what areas perform what function

Clinical observation – observing the effects of specific brain diseases and injuries

o Can provide clues to how the brain functions in “normal” people

Manipulating the brain – do not have to wait for brain injuries; can electrically, chemically, or magnetically

stimulate the brain and note the effects.

Recording the brain’s electrical activity

o Electrical activity in the brain’s billions of neurons occur in regular waves across the its surface

o Electroencephalogram (EEG) – an amplified recording of the waves of electrical activity that sweep

across the brain’s surface; measured by electrodes placed on the scalp

Works by presenting a stimulus repeatedly and having a computer filter out brain activity

unrelated to the stimulus, thus identifying the wave evoke provoked by the stimulus

Neuroimaging techniques

o PET (positron emission tomography) scan – a visual display of brain activity that detects where a

radioactive form of glucose goes while the brain performs a given task.

Active neurons use glucose. When the radioactive neurons are in the brain, the PET scan can pick

up their location, thus allowing us to see what areas of the brain perform certain tasks.

“hot spots” = activity

o MRI (magnetic resonance imaging) – a technique that uses magnetic fields and radio waves to

produce computer-generated images that distinguish among different types of soft tissue, allowing us

to see structures within the brain.

The head is put in a strong magnetic field which aligns the spinning atoms. Then a brief pulse of

radio waves disorients the atoms. When they begin to spin again, they release signals that provide

images of their concentrations, resulting in an image of the brain’s tissues.

o fMRI (functional MRI) – a technique for revealing blood flow and therefore, brain activity by

comparing successive MRI scans.

MRI scans show brain anatomy while fMRI scans show brain function.

Older Brain Structures

A species’ brain size does not necessarily dictate intelligence, however the brain’s structure and complexity does

indicate intelligence and functioning.

The Brainstem – the oldest part and central core of the brain, beginning where the spinal cord swells as it enters the

skull; the brainstem is responsible for automatic survival functions

Medulla – the base of the brainstem; controls heartbeat and breathing

Pons – helps coordinate movement

The brainstem is also the crossover point, where many nerves from each side of the brain connect.

Reticular formation – a nerve network in the brainstem that plays an important role in controlling arousal

o In the brainstem, between the ears

o Extends from the spinal cord to the thalamus

o When stimulated, the reticular formation arouses you into alertness. If severed, you could enter a coma

and be unresponsive.

Thalamus – the brain’s sensory switchboard, located on top of the brainstem; it directs messages to the sensory

receiving areas in the cortex and transmits replies to the cerebellum and medulla

Joined pair of egg-like structures

Receives information from all senses (except smell) and routes it to the brain regions that deal with seeing,

hearing, tasting, and touching.

Like the “brain’s train station” that receives routes and redirects them to their destination.

Cerebellum – the “little brain” attached to the rear of the brainstem; its functions include processing sensory input

and coordinating movement output and balance.

Baseball-sized, two wrinkled halves

People with injured cerebellums have difficulty walking and keeping balance; movements are jerky and

exaggerated.

*** These “older” brain functions all occur without any conscious effort – our brain processes information outside

of our awareness. ***

The Limbic System – a doughnut-shaped system of neural structures at the border of the brainstem and cerebral

hemispheres; associated with EMOTIONS such as fear and aggression and drives such as those for food and sex;

includes the hippocampus, amygdala, and hypothalamus.

Hippocampus – processes memories

Amygdala – two lima bean-sized neural clusters that are linked to emotion

o A monkey’s amygdala is lesioned a normally ill-tempered monkey would turn very mellow despite

instigation.

o Normally calm, domestic animals (cat) would cower in fear of mouse if the amygdala was stimulated or

manipulated with electricity.

Hypothalamus – a neural structure lying below the thalamus; directs some maintenance activities (eating,

drinking, body temperature), helps govern the endocrine system via the pituitary gland, and is linked to

emotion.

o Eg: thinking about sex can stimulate your hypothalamus to secrete hormones, which tell the pituitary

gland to influence the hormone release from other glands

The Cerebral Cortex – the intricate fabric of interconnected neural cells that covers the cerebral hemispheres; the

body’s ultimate control and information-processing center

Like bark on a tree – a thin surface layer on the cerebral (brain) hemispheres

Contains 20-23 billion nerve cells supported by nine times as many glial cells

o Glial cells – “glue cells;” cells in the nervous system that support, nourish, and protect neurons

Lobes – geographical subdivisions of the cerebral cortex separated by prominent fissures (folds) in the

brain.

LOBES OF THE BRAIN AND THEIR FUNCTIONS (FPOT)

Lobe Where in Cerebral Cortex? Function

Frontal Behind the forehead Involved in speaking, muscle movements, and making plans/judgments

Parietal At the top of the head,

towards the rear

Receives sensory input for touch and body position

Occipital At the back of the head Includes the visual areas, which receive visual information from the

opposite visual field

Temporal Roughly above the ears Includes auditory areas, each of which receive auditory information

primarily from the opposite ear

Each lobe carries out many functions and many functions require the interplay of several lobes.

Motor functions

motor cortex - an area at the rear of the frontal lobes that control voluntary movements.

o sends outgoing movements

o stimulation will cause different parts of the body to move

Sensory functions

sensory cortex - the area at the front of the parietal lobes that registers and processes body touch and

movement sensations.

o parallel to the motor cortex, behind it at the front of the parietal lobe

o stimulation to the sensory cortex will make the patient feel like they are being touched depending on what

section of the sensory cortex is stimulated.

The more sensitive a body region, the larger the area in the sensory cortex. (eg: lips are more sensitive, therefore

their corresponding area in the sensory cortex is larger than other regions)

Sight is processed in the occipital lobe in the visual cortex.

Sounds heard are processed in the temporal lobe in the auditory cortex.

Association Areas - areas of the cerebral cortex that are not involved in primary motor or sensory functions; rather,

they are involved in higher mental functions such as learning, remembering, thinking, and speaking.

any area of the cerebral cortex that is not the motor cortex, sensory cortex, visual cortex, or auditory cortex.

found in all four lobes

o frontal lobe association areas

judgment, plans, processing new memories; damage to the frontal

lobe can hinder these activities and also change personality by

removing a person's inhibitions (eg: Phineas Gage had a metal rod

enter is head and pass through the frontal lobe in 1847. He survived

but his once calm and polite nature was gone, replaced with

irritability and dishonesty - loss of moral compass)

o parietal lobe association areas

math and spatial reasoning (large and unusually shaped in Einstein's brain)

o temporal lobe association areas

face recognition

Language

aphasia - impairment of language, usually caused by left hemisphere damage either to Broca's area (speech) or

Wernicke's area (understanding)

o people suffering from aphasia may be able to read but not write, write but not read, read but not speak,

speak but not read, read numbers but not letters… it depends on what part of the brain is damaged.

Broca's area - part of the cerebral cortex that controls language expression; in the frontal lobe, usually in the

left hemisphere, that directs the muscle movement involved in speech.

Wernicke's area - part of the cerebral cortex that controls language reception; involved in language

comprehension and expression; usually in the left temporal lobe.

How we use language… when you read aloud, 1) the words register in the visual area, 2) are relayed to a second

brain area, the angular gyrus, which transforms the words into an auditory code that is 3) received and understood

by the Wernicke's area, and 4) sent to Broca's area, which 5) controls the motor cortex as it creates the

pronounced word.

o The type of aphasia depends on which chain in the series is damaged

*** The brain uses specialization and integration to function.***

The Brain's Plasticity

the brain is sculpted by our genes but also by our experiences.

Brain plasticity - the brain's capacity for modification, as evident in brain reorganization following damage

(especially in children) and in experiments on the effects of experience on brain development.

most neurons will never regenerate if damaged or killed, and many brain functions are preassigned to certain areas

that if damaged will affect the person's ability for the rest of their life… but some neural tissue can reorganize

after damage as the brain repairs itself after damage.

o eg: if you lose a finger, the sensory cortex reorganizes and receives information from the other fingers

which all in turn become more sensitive.

Blindness

o when reading Braille, the brain area dedicated to that finger expands as the sense of touch invades the

visual cortex, which normally helps people see

Deafness

o the auditory cortex receives no information from sound, so it expands to new functions like visual tasks,

which is why deaf people have been found to have enhanced peripheral vision.

Our Divided Brain

the brain's two hemispheres have different functions

o Left hemisphere - "dominate" or "major" hemisphere, controls reading, writing, speaking, mathematic

reasoning, and understanding

o Right hemisphere - "subordinate" or "minor" hemisphere, controls insight, imagination

corpus callosum - the large band of neural fibers connecting the two brain hemispheres and carrying

information between them.

o when severed, patients can function like before the damage (can eliminate seizures) but the two

hemispheres could not communicate

split brain - a condition in which the two hemispheres of the brain are isolated by cutting the connecting fibers

(mainly the corpus callosum) between them

Gazzaniga's experiment to study split brains…

o ****The information seen by the right eye is processed in the left occipital lobe, while information seen

by the left eye is processed in the right occipital lobe.

o split brain patient stares at a dot on a screen while the image "HE°ART" flashes on the screen.

o HE appeared in the left visual field which is processed in the right hemisphere, while…

o ART appeared in the right visual field which is processed in the left hemisphere

o Patient then asked what word they had seen.. the patients said they had seen ART (because HE was

processed in the right hemisphere which isn't verbal… can't respond)

o When asked to point to the word on a poster with their left hand (controlled by the right brain), they

pointed to HE.

o Given the opportunity to express itself, each hemisphere reported only what is had seen. The right brain

(controlling the left hand) had not seen HE and could only report to have seen ART.

Split brains can comprehend and complete completely different tasks simultaneously.

o left brain is more active when deliberating over decisions

o right brain more active with short, quick responses and intuition, also identifies faces and facial

expressions

Studying Hemispheric Differences in the Intact Brain

right brain – perceptual tasks

left brain – speaking, calculating

Lateralization – the brain’s two hemispheres are not exactly alike

o Eg: left brain largely responsible for speech (Broca’s area), if the left brain is sedated, the ability to speak

is lost, along with the ability to move the right side of the body. If the right side of the brain is sedated,

the ability to control the left side of the body is lost, along with various abilities such as the ability to

recognize one’s face in a photograph

o Eg: People with right brain damage (stroke, etc) have difficulties recognizing subtleties in words but can

understand the meaning of the word. So presented with the words pie, belly, and luck, right brain

damaged patients can understand each word separately, but cannot see why they are related ( with the

word pot).

Brain Organization and Handedness

~10% of people are left-handed (more males than females)

Research has shown that most humans (across cultures) and intelligent primates are right-handed. Also, research

into fetus development has found that 9 of 10 babies suck their right thumb in the fetus. Therefore, there is a

relationship between genes/prenatal factors and right-handedness.

A Scientific Mystery: The Case of the Disappearing Southpaws

Researchers have found that prevalence of left-handers declines with age.

o Could it be that left-handers switch to right-handers over the lifespan?

o Decades ago, left-handedness was “corrected” in school, therefore more old people are right-handed.

Could it be that society and education are more accepting of left-handedness?

o Do left-handers die young?

Accidents with equipment that is universally made for right-handers.

Left-handers experience more birth stress, alcohol/tobacco use, knee-joint issues, and immune

system problems.

These differences are huge, but early researchers concluded that right-handers live 8-9 years

longer than their counterparts. These numbers dwindle after children are excluded. Further

research has found that there is no difference in life expectancy based on handedness.