The Brain & Nervous System

History

• Known to relate to thought and behavior for over 3500 years– Edwin Smith Surgical

Papyrus

• Greeks thought the brain– Was the seat of the mind– Was responsible for

intelligence– Cooled the blood

Trepanning

• Practiced since at least 6500 BCE

• Still used in limited cases– Subdural Hematomae– Most recent psychological

use from 2000

• Used for– Mental Illness– Increased “brainpower”

History

• Descartes believed in dualism– Mind was in but not of

the Brain– Interacted at the Pineal

Gland

• Vesalius– Found nerves

transmitted sensation and motion

– Nerves were not hollow

History

• Galvani first discovered that the nervous system used electricity

• Touched a frog leg with a charged scalpel, which caused a leg twitch

Structure

• The nervous system breaks down into two basic parts– Central Nervous System (Brain & Spinal Cord)– Peripheral Nervous System (Everything Else)

• PNS further divides into– Somatic (voluntary) and Autonomic (involuntary)– Autonomic subdivides into sympathetic and

parasympathetic

Peripheral Nervous System

• Somatic System is everything that is voluntary– Arms, Legs, Eyes, etc.

• The one exception is a reflex arc– Bypasses the brain– Reaction at spinal cord– Action is quicker than

nerve impulse to brain

Peripheral Nervous System

• Autonomic subsystem controls automatic/smooth muscles– Heart, Lungs, etc

• Sympathetic promotes “fight or flight” responses– Dilates pupils, increases heart rate, inhibits peristalsis

• Parasympathetic promotes “rest & digest”– Constrict pupils, slow heart rate, constricts bronchi

• Sympathetic & parasympathetic are opponent systems

Neurons

• The brain and all nerves are made up of neurons– The largest is over 3 feet long

• Every neuron is made up of a– Dendrite– Cell Body– Axon– Axon Terminals

Neurons

• Neurons fire electrically– Have an action potential

• Start off polarized– Excess of Na+ & Cl- outside, K+ inside– Resting potential is around -70 mV

• Depolarization occurs when channels open– Ions flow in and out– Firing occurs around -45 mV

• Neural firings occur at a threshold• All or none• Intensity = rate of fire

Neurons

• After firing, neurons enter a refractory period• Absolute refractory period– Impossible to evoke another firing– Na+ channels are inactive

• Relative refractory period– Requires stronger than normal stimulus

Neurons

Neurons

• Some neurons are myelinated– White matter (vs. Gray matter)

• Insulation– Hops from one uninsulated part to another– Nodes of Ranvier

• Demyelinating diseases– MS, transverse myelitis, Guillan-Barre, etc– Vision problems, weakness, odd sensations, loss of

coordination

Neurons

• Neurons don’t touch• Synapse is a gap

through which communication occurs

• Axons release a transmitter

• Dendrites pick it up

Neurotransmitters

• Neurons communicate with neurotransmitters– Acetylcholine (muscle movement, arousal, reward)– Dopamine (motivation, punishment/reward)– Epinephrine/Norepinephrine (adrenaline, allergy)– Serotonin (mood)– Endorphins (opiods)– GABA (mood, anxiety)– More than 40 others (and homologues)

• Lock-and-Key model• Video

Drugs

• Some drugs work by exciting/antagonize production– Nicotine (acetylcholine)– SSRI (seretonin)

• Some drugs are better keys than neurotransmitters– Heroin (Endorphins)– Cocaine (Dopamine)– Alcohol (GABA)

The Brain

• Divided into two hemispheres– Connected by Corpus

Callosum

• Various lobes & structures– Mirrored in each

hemisphere– E.g. “left & right _____”

• Watch

Brain Structures

• Brainstem• Thalamus• Cerebellum• Limbic System• Cerebral Cortex

Brainstem

• Basic life functions• Medulla (pith/marrow)

– Heart– Lungs

• Reticular (net) Formation– Arousal/Alertness– Consciousness– Pain

• Pons (bridge)– Gathering of cranial

nerves

Thalamus

• “Inner Chamber”• Acts as a sensory relay

station• Not as well understood• Implicated in Korsakoff’s

syndrome and Hereditary Familial Insomnia

Cerebellum

• “Little Brain”• Motor Control

– Damage does not cause paralysis

• Active in motor learning– Unconscious/Automatic

actions

• Signals move unidirectionally– Unlike all other parts of

brain

Limbic System

• Amygdala (Almond)– Emotionally significant stimuli (reward/fear)– Stimulation -> Agression; Destruction -> Placid

• Hypothalamus (Under Thalamus)– Body maintenance– Hunger, thirst, sex, temperature– Adjacent to pituitary– Three F’s (Fighting/Fleeing, Feeding, Sex)

Hypothalamus Damage

Limbic System

• Amygdala (Almond)– Emotionally significant stimuli (reward/fear)– Stimulation -> Agression; Destruction -> Placid

• Hypothalamus (Under Thalamus)– Body maintenance– Hunger, thirst, sex, temperature– Adjacent to pituitary

• Hippocampus (Seahorse)– Necessary for long-term memory formation– Think “Memento”

Cerebral Cortex

• Frontal Lobes• Sensorimotor Cortex• Parietal Lobes• Temporal Lobes• Occipital Lobes

Occipital Lobe

• Back of the brain– Above Cerebellum

• Controls visual processing

• Highly specialized Cell groups– Line Angles

• Incredibly basic• “Seeing stars”

Temporal Lobes

• Specific visual processing– Faces

• Hearing– Auditory nerve connects

• Episodic/Declarative memory– “And then, this happened”

• Left side involved in speech/language– Broca’s area = speech

production– Wernicke’s area = speech

comprehension

The Man Who Mistook His Wife for a Hat

• Temporal Lobe damage -> prosopagnosia– Face blindness

• Cannot connect faces to semantic information about people

• May not recognize a person until they speak

• Oliver Sacks

Parietal Lobes

• Integrates sensory information

• Numeracy– What is the relationship

between 8 and 2?

• Where and how of vision– Spatial relations– Action saliency

• Hemispatial neglect– Right lobe usually

Sensorimotor Cortex

• Between parietal & frontal lobes

• Governs movement and sensation

• Areas relate to sensitivity and fine motor control– Not size

• Phantom limb syndrome

Frontal Lobes

• Involved in planning– Consequences– Moral judgment– Response inhibition

• Similarity judgments• Doesn’t mature until

early/mid twenties• Underactive in ADHD

patients

Integrating It All

• Occipital lobe processes shapes

• Temporal lobe tells me it’s a dog– Registers barking

• Parietal lobe tells me it’s angry and running towards me

• Limbic system tells me to run– Engages my sympathetic

nervous system

• Motor cortex works my legs

Lateralization

• Brain divides into left & right hemispheres– Lateralization = specialization of hemispheres

• Left is logical, right is intuitive– Grammar & literal meaning on left, prosody and

intonation on the right• The brain is wired contra-laterally– Left controls right & vice-versa

• Left-handed people are less lateralized– Cause & effect unclear

Lateralization Test

• Mark which of the following you would prefer (not necessarily ability)– A) Major in Logic– B) Write a Letter– C) Fix things at home– D) Major in Art

• Mark which of the following you would prefer (not necessarily ability)– A) Be a movie critic– B) Learn new Words– C) Improve your skills in a game– D) Create a new toy

• Mark which of the following you would prefer (not necessarily ability)– A) Improve your strategy in a game– B) Remember people’s names– C) Engage in sports– D) Play an instrument by ear

• Mark which of the following you would prefer (not necessarily ability)– A) Review a book– B) Write for a magazine– C) Build new shelves at home– D) Draw a landscape or seascape

• Mark which of the following you would prefer (not necessarily ability)– A) Analyze market trends– B) Write a movie script– C) Do carpentry work– D) Imagine a new play

• Mark which of the following you would prefer (not necessarily ability)– A) Analyze management practices– B) Locate words in a dictionary– C) Put jigsaw puzzles together– D) Paint in oil

• Mark which of the following you would prefer (not necessarily ability)– A) Be in charge of computer programming– B) Study word origins and meanings– C) Putter in the yard– D) Invent a new gadget

• Mark which of the following you would prefer (not necessarily ability)– A) Analyze production costs– B) Desscribe a new product in words– C) Sell a new product on the market– D) Draw a picture of a new product

• Mark which of the following you would prefer (not necessarily ability)– A) Explain the logic of a theory– B) Be a copy writer for ads– C) Work with wood and clay– D) Invent a story

• Mark which of the following you would prefer (not necessarily ability)– A) Be a comparison shopper– B) Read about famous men and women– C) Run a traffic control tower– D) Mold with clay and putty

• Mark which of the following you would prefer (not necessarily ability)– A) Analyze your budget– B) Study literature– C) Visualize and re-arrange furniture– D) Be an artist

• Mark which of the following you would prefer (not necessarily ability)– A) Plan a trip– B) Write a novel– C) Build a house/shack– D) Make crafts your hobby

Lateralization Test

• Add up your “a” and “b” responses– This is your left brain score

• Add up your “c” and “d” responses– This is your right brain score

• A difference of more than 3 indicates strong lateralization– Less than 3 is balanced

• My score is 11 left/1 right

Corpus Callosum

• The hemispheres communicate via corpus callosum– Mostly, not exclusively

• Bundle of nerves that serve as a connector

• Highly specialized

Split Brains

• Sometimes, the corpus callosum must be cut– Last resort in epilepsy

• Allows us to look at how the brain lateralizes

• What might you expect to see?

Split Brains

• Gazzaniga would present one word to each visual field

• Only the word in the right field could be read

• Patients could identify left-field word with left hand– Why?

Split Brains

• What will a split brain patient say is the difference

• Which house will a split brain patient prefer?

Plasticity

• Refers in general to the ability to forge connections

• The brain can cover for itself– Rewire & reorganize

• Easier when younger• Whole specializations

will migrate

Concussions

• A bruise on the brain– Newton’s first law– Contracoup

• Physical– Headache, nausea,

dizziness

• Psychological– Confusion, slurred speech,

impaired reasoning

• Axons can be stretched, twisted, or sheared

Neuroimaging

• For a long time, we could only look at the brain after death or when it was damaged– This has obvious limitations

• Now, we have several ways of looking at brain activity– Lesions– Electroencephalograph (EEG)– Positron Emission Tomography (PET)– (functional) Magnetic Resonance Imaging (fMRI)– Event Related Potential (ERP)

LesionsCutting into the brain and looking for change.

Brain tumors also lesion brain tissue.

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Lesions

• Removal or destruction of some part of the brain.

• Frontal Lobotomy

EEG

• Records electrical potential along the scalp– “Brain Waves”

• Cheap and easy– Low-res

• Used for biology– Seizures– Sleep disturbances

PET

• Patient is injected with radioactive glucose

• Scanner picks up metabolism– More metabolism =

more activity• Can find damaged

areas– Changes metabolism

• Absolute

(f)MRI

• Measures blood flow– Strong magnet causes

ions in blood to align

• Good spatial resolution• Has a lag time• Indirect• Works on contrast– Changes in blood flow

between states/tasks/subjects

ERP

• Measures neural firings of small groups of neurons

• Can tell us when, but not where

• Named negative/positive plus time– E.g. “N100”

MRI PET

• ERP net

TMS

• Transcranial Magnetic Stimulation• Small magnetic pulse discharges all action

potentials in a confined area– Effectively “knocks out” a part of the brain

• Generally safe– Small risk of seizures

• Allows for direct brain experimentation