Neuroscience and Behavior

Chapter 2

Introduction Biological psychology: scientific

study of biological bases of beh and mental processes AKA biopsychology, psychobiology Part of neuroscience (scientific study of

nervous system What we will study

Neuron Nervous System and its divisions

Next major subtopic Neurons – we will study…

Parts of the neuron Communication of neural impulse within neuron Communication of neural impulse between

neurons

Neurons—Introduction Neuron: highly specialized cell that

communicates info in electrical & chemical form

Types Sensory neurons: convey info about

environment from sense organs TO brain Motor neurons: convey info TO muscles

and glands Interneurons: communicate btn

neurons

Neurons—Parts Dendrites: fibers extending from cell body that

receive information Cell body (soma): processes nutrients and provides

cell with energy Axon: long, fluid-filled tubes that carry neuron’s

message to other cells Vary in length Myelin sheath: white, fatty covering of axon that aids

speed of impulse Multiple Sclerosis results in damage to myelin faulty neural

communication Video clip:

http://www.youtube.com/watch?v=i-NgGKSNiNw&NR=1&feature=fvwp

Neurons—Parts

Neurons—Communication WITHIN NeuronWhat happens?

Neuron fires and sends electrical impulse from the dendrite through the cell body to axon

After it fires, there is brief resting period during which neuron cannot re-fire

Neurons—Communication WITHIN Neuron (cont’d) Terms:

Action potential: neural impulse; brief electrical impulse that is transmitted along axon

Stimulus threshold: minimum level of stimulation required to activate neuron/action potential

All-or-none law: principle that neuron is sufficiently stimulated or not (neuron fires same each time)

Refractory period: period after action potential when neuron cannot fire again

Neurons—Communication BETWEEN neurons Synapse: connection btn axon of sending

neuron and dendrite of receiving neuron Synaptic gap/cleft: fluid-filled space btn axon

terminal of one neuron and dendrite of another neuron

Neurons—Communication BETWEEN neurons (cont’d) Communication across neurons occurs chemically (most

often) Presynaptic neuron creates chemical that crosses synaptic gap to

postsynaptic neuron Neurotransmitter: chemical that transmits message across

synaptic gap 100 different compounds Lock and key – there are receptor sites on dendrites Video: Zoloft commercial

Reuptake: process by which neuron’s axon terminal reabsorbs neurotransmitter

Types of messages: Excitatory and inhibitory messages (of neurotransmitter) Excitatory message: increases likelihood that postsynaptic neuron will

activate Inhibitory message: decreases likelihood that postsynaptic neuron will

activate

Neurons—Communication BETWEEN neurons (cont’d) Neurotransmitters

Acetylcholine Stimulates muscles to contract Also involved in memory, learning, and intellectual

functioning For those with Alzheimer’s Disease severe deficit in

acetylcholine Dopamine

Involved in movement, attn, learning, and pleasurable/rewarding sensations

Parkinson’s Disease too little; Schizophrenia too much

Neurons—Communication BETWEEN neurons (cont’d) Neurotransmitters (cont’d)

Serotonin and norepinephrine Serotonin sleep, mood and

emotion Norepinephrine activation of

neurons in brain, learning and memory

Endorphins Regulate pain reception

Drugs and neurotransmitters May increase/decrease amt of

neurotransmitter Affect length of time

neurotransmitter spends in synapse

Mimic neurotransmitter Block affect of

neurotransmitter

Next major topic: Nervous system We will study…

The major divisions of the nervous system (CNS and peripheral nervous system)

The brain, the lobes of the brain, and hemispheric specialization

New Major Topic—Nervous SystemNervous system divided into two parts—Central Nervous System and Peripheral Nervous System Central Nervous System: brain

and spinal cord Peripheral Nervous System: all

nerves outside of CNS

Nervous System—Peripheral Nervous System Peripheral Nervous System: all neurons outside of CNS

Two components: Somatic Nervous System

Voluntary movement Skeletal muscles

Autonomic Nervous System involuntary movement Think automatic Includes blood pressure, heart rate, breathing and digestion Two branches—Sympathetic and Parasympathetic

Sympathetic Nervous System: increases energy – arousal Body’s emergency system Fight-or-flight response HR increases, digestion stops, breathing

increases Parasympathetic Nervous System: conserves energy – calming

Returns body to resting state

Nervous System—Peripheral Nervous System Autonomic Nervous

System (cont’d) Two branches—

Sympathetic and Parasympathetic Sympathetic Nervous

System: increases energy – arousal Body’s emergency system Fight-or-flight response HR

increases, digestion stops, breathing increases

Parasympathetic Nervous System: conserves energy calming Returns body to resting state

Nervous System—Central Nervous System CNS = Brain and spinal cord Spinal cord: connects Peripheral

Nervous System to brain Spinal reflex: simple automatic beh

processed in spinal cordExample withdrawal reflex from heat,

pain, etc.Single sensory neuron and single motor

neuron

Nervous System—Central Nervous System (cont’d) Brain

Development—highlights Neural tube lined with neural stem cells These develop into 3 structures – hindbrain, midbrain, and

forebrain As neural tube expands, it develops cavities called

ventricles that are found at core of developed brain New neurons developed at rate of 250,000 per minute at

peak periods of development Fetal brain continues to dev as many as 2 million

synaptic connections per second At birth, brain is about one-fourth size of adult brain Fully matured brain weights about 3 lbs Recent research indicates brain cont’s to grow into early

adulthood (frontal lobe)

Nervous System—Central Nervous System (cont’d) Brain

Neuroimaging Techniques Electroencephalogram (EEG): amplified reading of

electrical activity of brain PET scan (Positron Emission Tomography): displays

activity of various brain areas MRI (Magnetic Resonance Imaging): uses magnetic

fields and radio waves to produce computer-generated images of brain tissue

fMRI (Functional MRI): reveals blood flow and therefore brain activity

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Brainstem – Hindbrain and Midbrain Hindbrain

Connects spinal cord to brain Sensory and motor neurons cross one side of body to

opp side of brain why left side of body is controlled by right side of brain (called contralateral organization)

Structures of hindbrain – medulla, pons, and cerebellum Medulla: controls breathing, HR, digestion (vital

functions) Pons: bridge btn cerebellum and rest of brain Cerebellum: balance, muscle tone, coordinated

movements, motor skills Reticular formation (aka reticular activating

system): network of neurons that regulates attn, arousal, and sleep

Midbrain: relay station for processing auditory and visual information

Nervous System—Central Nervous System (cont’d)

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Forebrain—cerebrum 90% of brain Cerebral cortex:

Thin layer of interconnected neurons

Divided into two hemispheres and four lobes Temporal Lobe Occipital Lobe Parietal Lobe Frontal Lobe

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Lobes Temporal lobe

Located near temple Auditory information

Occipital Lobe Back of brain Visual information

Parietal Lobe Bodily or somatosensory info (touch, pressure, info from muscles) Body parts are represented on somatosensory cortex but not equally

distributed (in proportion to sensitivity to stimulation, so hands and face are largest)

Frontal Lobe Planning, initiating, and executing voluntary movement Also contains primary motor cortex which controls body parts (similar to

somatosensory cortex above) Brain anatomy – http://www.pbs.org/wnet/brain/3d/index.html

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Association areas of cortex In all four lobes Combine sensory and motor information Coordinate interaction among diff brain areas

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Limbic system Other forebrain structures beneath cortex Form border around brainstem Involved in emotion, motivation, learning, and memory Structures

Hippocampus: involved in learning and memories Thalamus: brain’s relay station (sorts imp info); involved in

sensory information (except smell) Hypothalamus:

Regulates survival behavior such as eating, drinking, and sexual activity

Regulates autonomic nervous system heart rate, blood pressure

Amygdala: involved in emotions (fear, anger, disgust), integrating senses, and memories

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Hemispheres Left and right hemispheres divided by corpus callosum

(thick bundle of axons that acts as communication link btn hemispheres)

Diffs in function roughly symmetrical in that same functions location in same place in each hemisphere

Analogy one side does word processor, other does graphic design

Nervous System—Central Nervous System (cont’d)

Brain (cont’d) Hemispheres (cont’d)

Language and Left Hemisphere Paul Broca

French physician who treated several pts who had difficulty speaking but could comprehend written or spoken lang

Autopsies showed damage to area in lower left frontal lobe of brain

Broca’s area: plays crucial role in speech production

Karl Wernicke German neurologist who discovered

another area in left hemisphere that when damaged produced lang disturbance

Pts had difficulty understanding spoken or written communications. They could speak but often made no sense.

Autopsies revealed damage to same area in left temporal lobe

Aphasia: partial or complete inability to articulate or understand spoken or written lang b/c of brain injury/damage

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Hemispheres (cont’d) Split brain research

Roger Sperry Operation used to stop recurring seizures in severe cases of

epilepsy—involves cutting corpus callosum Research

Asked Ss to focus on point in middle of screen Would flash word or picture to left or right of midpoint

Visual info to right of midpoint goes to left hemisphere and visual info to left goes to right hemisphere

Objects were also behind the screen hidden from view but reachable Projected image of object (hammer) to left of midpoint (goes to right

hemi) S asked to say what object was could not say hammer When asked to use left hand to reach under partition to find object

shown, could do this

Nervous System—Central Nervous System (cont’d)

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Hemispheric specialization Lateralization of function:

idea that specific psychological functions are processed by one side of brain

Left hemisphere Language abilities, speech,

reading, and writing Right hemisphere

Nonverbal emotional expression and visual-spatial tasks

Musical appreciation (not necessarily ability)

Keep in mind Diffs are relative, not absolute Both hemispheres involved

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Handedness Stats: 90% are right-handed; 10% are left-handed (we’re unique!) Is handedness inherited?

Ultrasound show that more than 9 in 10 fetuses suck right thumb If both parents right-handed, 1 in 10 chance child will be lefty (if one

parent lefty and other righty, then 1 in 5 chance of having lefty) Research when infant lies down, which direction is head turned

Head-right usually had preference for right hand Head-left usually had preference for left hand

Left-handed inds Reading disabilities, allergies, and migraine headaches more common More common among musicians, mathematicians, and artists Brain research left-handed inds still use left hemisphere for lang Will show pattern of using both hands

Nervous System—Central Nervous System (cont’d) Brain (cont’d)

Plasticity of the brain Plasticity: brain’s ability to change (esp during

childhood) function and structure to adapt to damage Functional plasticity: brain’s ability to shift functions

from damaged area to undamaged area Structural plasticity: brain’s ability to change

physical structure in response to learning, active practice, and environmental influence

Examples If blind ind uses one finger to read Braille, brain area

dedicated to that finger expands sense of touch Loss of finger – sensory cortex will begin to receive info

from adjacent fingers http://www.youtube.com/watch?v=TSu9HGnlMV0