Module 5

Modern Myths About the Brain

Myth #1: People only use 10% of their brain

• While not all of the brain is active all at once, functional magnetic resonance images (fMRI) show several brain areas are at work for any given activity, depending on what function is needed.

Myth #2: Alcohol kills brain cells

• A lack of thiamine (vitamin B) causes temporary damage to dendrites the message-relaying neurons.

• This reaction accounts for slurred speech, stumbling, and ill-advised public urination.

• No damage is actually incurred by the brain cells themselves, and the dendrites eventually recover

MYTH #3: Your brain is all grey

It is grey, white, red, and black. •Grey matter is, in fact, mostly grey. •white matter in the form of connective nerve fibers. •black part, called substantia nigra (“black substance”)•And the red? •That’s blood.

MYTH #4: Subliminal messages work on your brain without you knowing it

• 1957, market researcher inserted messages urging moviegoers to purchase soda and popcorn into a film in New Jersey.

• appeared for no longer than 1/300 of a second• reported that Coca Cola and popcorn sales increased to

the tune of 18 percent and 57 percent, respectively?• 1990 Judas Priest trial, in which the suicides of two

teenagers were blamed on subliminal messages in the band’s lyrics,

• all concluded that no scientific evidence

Myth #5: Brain Damage Is Always Permanent

In some instances, the brain can repair itself.

the brain creates new pathways between neurons

the phenomenon of brain plasticitystroke patients, for example, can regain

speech and motor skills through therapy.

Myth #7: Your brain hurts when you have a headache

It's not your brain that's hurting when you get a headache – without pain receptors, your brain can't feel any pain.

History of the Mind

Franz Gall suggested, that the study of bumps on the skull represented mental abilities.

His theory though incorrect, nevertheless proposed different mental abilities were modular.

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Phrenology

Data on the Human Brain

About 3 pounds 78% water Less than 2.5% of

body’s weightUses 20% of body’s

energy

Amazing Brain Numbers

100 billion neurons

1 trillion glial cells

1,000 trillion synaptic connection points

280 quintillion memories

Studying the Brain: Research Methods

1. Electrical brain stimulation 2. Damage studies/lesioning 3. Electroencephalograms (EEG) 4. Transcranial magnetic stimulation (TMS) Brain imaging

1. computerized tomography (CT)2. positron emission tomography (PET)3. magnetic resonance imaging (MRI)4. functional MRI (fMRI)

Electrical stimulation of the brain

• an implantable deep brain stimulation device • delivers carefully controlled electrical pulses to

precisely targeted areas of the brain involved in motor control.

• it can reduce muscle tremors • restore muscle control for those with Parkinson's

Brain lesion experimentally destroys brain tissue to study animal behaviors after such destruction.

“deposits” in the brain bank

Clinical observations help explain a number of brain disorders.

• Alterations in brain changes due to neurological and psychiatric diseases are now being catalogued.

Electroencephalogram (EEG)

An amplified recording of the electrical waves sweeping across the brain’s surface, measured by electrodes placed on the scalp.

Electroencephalogram (EEG)Test hearing in a baby

Electroencephalogram (EEG)

beta

delta

theta

alpha

Brain ImagingCT (computed tomography) Scan

a series of X-ray photographs taken from different angles

combined by computer into a composite representation of a slice through the body

also called CAT scan

• this CAT scan shows extremely severe atrophy.• The black areas should be white (cerebral cortex)

Whose atrophied brain is this??? She died in 2005

Terri Schiavo:

vegetative state 1990 – 2005

heart attack related to bulimia

Positron-Emission Tomography PET Scan

A method for analyzing biochemical activity in the brain, using injections of a glucose-like substance containing a radioactive element

Active areas have increased blood flowSensors detect radioactivity because

active areas consume glucose rapidlyDifferent tasks show distinct activity

patterns

PET Scan

PET scan to identify depression and Alzheimer’s Disease

Brain Scan – to locate tumors

Magnetic Resonance Imaging (MRI)

Method for studying body and brain tissue using magnetic fields and radio frequencies

Magnetic fields alight certain ions/compoundsWhen field is removed, molecules release

energy as radio wavesComputer calculates tissue density from radio

wavesProvides clear 3D image

MRI of the brain – brain injury

Subdural hematoma

MRI

MRI Scan

Top images show ventricular enlargement in a schizophrenic patient.

Functional MRI images

This image shows brain regions when a participants lies.

•Anterior Cingulate Cortex:

• active w/conflicting urges

Hindbrain (continuation of the spinal cord) - vital function - medulla; reticular formation; pons; cerebellumMidbrain (above the hindbrain) -small area between hindbrain and forebrain to relay info eyes, ears and skin that controls

certain automatic behaviorsForebrain (front part of the brain) -most highly developed part of brain -responsible for most complex aspects of

behavior – thinking and decision making

Brain Regions and Their Functions

Older Brain StructuresBrainstem the oldest part of the brain, beginning where the spinal cord swells and enters the skull. Responsible for automatic survival functions.

Parts of the Brain StemPonsInvolved in sleeping, waking, dreamingrelay station for the cerebral cortex and the

medullaMedulla

Responsible for certain automatic functions (breathing, heart rate)

Reticular Activating SystemArousal/alertness

• Cerebellum

Cerebellum1. the “little brain” attached to the rear of the brainstem

2. Regulates balance and coordination of movement

3. Plays a part in:analyzing sensory infovoluntary movementsnonverbal learning & memory

Thalamus1. the brain’s sensory switchboard, located on top of the brainstem.

2. Relays incoming sensory messages (except olfactory) to higher areas (cerebral cortex)

3. Slow during sleep/speed up to produce waking consciousness

Thalamus

Limbic System1. a doughnut-shaped system of neural structures at the border of the brainstem and cerebrum

2. associated with emotions such as fear, aggression 3. center for motivationMain Parts of the limbic system

AmygdalaHypothalamusHippocampus

The Limbic System

When the limbic system is manipulated rat will navigate fields or climb up a tree

Brain stimulation to reward for turning right or left!!

The Amygdala 1. two almond-shaped neural clusters linked to emotion of fear and anger.

2. Responsible for:ArousalRegulation of emotion

3. Involved in:Emotional memoryInfluence fear & aggression

4. psychosurgery in humans reduces rage but has devastating after effectsunethical

Stimulate the Amygdala

Hypothalamus & Pituitary GlandHypothalamus (“below” thalamus)

1. Involved in emotions and drives vital to survival (hunger, sex)2. Directs maintenance activities

- hunger, thirst, motivation3. Pituitary Gland

Small endocrine gland which releases hormones and regulates other endocrine glands Governed by hypothalamus

Hypothalamus

Lateral hypothalamus hunger center causes us to eat when stimulated. (“start”) If area destroyed, no hunger; will starve to death unless forced to eat.

Ventromedial Hypothalamus satiety center: causes us to stop eating when

stimulated. (“stop”)If area is destroyed, eat unless we are deprived

of food.

Hypothalamus - Motivation

Rats cross an electrified grid for self-stimulation, when electrodes are placed in the reward (hypothalamus) center

The Hippocampus“Gateway to memory”Responsible for:

Storage of new information in memory

Enabling us to form spatial memories for navigating the environment

Hippocampus

Stop!

Cerebral Cortex

• Cerebral Cortex

• The outermost layer of gray matter making up the superficial aspect of the cerebrum

• The body’s ultimate control and information processing center.

The Cerebral Cortex

• Glial Cells cells in the nervous system that support, nourish, and protect neurons

Front of the Brain Back of the Brain

Cerebral Features:

• Sulci – Small grooves dividing the gyri– Central Sulcus – Divides the Frontal Lobe from the Parietal Lobe

• Fissures – Deep grooves, generally dividing large regions/lobes of the brain

– Longitudinal Fissure – Divides the two Cerebral Hemispheres– Transverse Fissure – Separates the Cerebrum from the Cerebellum– Sylvian/Lateral Fissure – Divides the Temporal Lobe from the Frontal and Parietal Lobes

• Gyri – Elevated ridges “winding” around the brain.

Gyri (ridge)

Fissure

(deep groove)

Sulci (groove)

Longitudinal Fissure

Transverse Fissure

Specific Sulci/Fissures:

The Cerebrum1. Largest brain structure

2. Two cerebral hemispheres connected by the corpus callosum

3. Surrounded by cerebral cortex (thin layers of cells – gray matter)

4. Responsible for higher forms of thinking

5. 2 cerebral hemispheres separated by longitudinal fissure (L/R hemispheres)

The Cerebrum - Two Hemispheres

Cerebral Hemispheres –corpus collosum separates the hemispheresLeft hemisphere – verbal processing: language, speech, reading, writing

Right hemisphere – nonverbal processing: spatial, musical, visual recognition

Frontal

Parietal

Temporal

Occipital

Lobes of the Brain - Frontal located at the top front part of the skull

• It plays an integral role in the following functions/actions:

- Decision Making/Reasoning

- Personality

- involved in speaking; muscle movement motor cortex (Broca’s area)

- Association area: cerebral cortex NOT devoted to sensory or motor function

Frontal Lobe

• Broca’s Area – controls facial neurons, speech, and language comprehension. •located in left frontal lobe.

– Aphasia: impairment of expression or comprehension of language–Broca’s Aphasia – Results in the ability to comprehend speech, but the decreased motor ability (or inability) to speak and form words.

Lobes of the Brain - Parietal Lobe

The parietal lobe of the brain is located behind the frontal lobe

• plays major role in following functions/action:

- Spatial awareness and perception- Proprioception - Awareness of body/ body parts in space and in relation to each other

Pleasure, pain, touch, temperature include the sensory cortex

Lobes of the Brain – Occipital Lobe

•located at the back of the brain

•Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.

Occipital Lobe – Cortical RegionsPrimary Visual Cortex – This is the primary

area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc.

• Visual Association Area – Interprets information acquired through the primary visual cortex.

Visual Function

Functional MRI scan shows the visual cortex activated as the subject looks at faces

Lobes of the Brain – Temporal Lobe

The temporal lobes are located on the sides of the brain

• play an integral role in the following functions:

- hearing- organization and comprehension of language

Temporal Lobe – Cortical Regions

Primary Auditory Cortex – Responsible for hearing

• Wernicke’s Area – language comprehension. located on the left temporal lobe.

- Wernicke’s Aphasia – Language comprehensionis inhibited.

-Words and sentences not clearly understood, andsentence formation inhibited or non-sensical.

74Functions & locations in the brain

Functions of the CortexMotor Cortex: area at the rear of the frontal lobes controls voluntary movements. Sensory Cortex: (parietal lobe) receives information from skin surface and sense organs.

The cerebral cortex in humans

Stimulation of Motor CortexCaused movement when applied to an arch-shaped region in back of frontal lobe

Parts in the left or right hemisphere, specific body parts moved on the opposite side of the body

William Penfield creates a brain map

NO pain receptors in the brain!!

The Cerebral Cortex

1. brain area receives info from skin senses and from movement of body parts

2. located at the front of the parietal lobe

3. the more sensitive the areathe greater sensory cortex area

Where are incoming messages received in the cortex?

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Auditory FunctionFunctional MRI scan shows the auditory cortex is activate in patients who hallucinate.

Association AreasMore intelligent animals have increased “uncommitted” or association areas of the cortex

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Specialization & IntegrationBrain activity when hearing, seeing, and speaking words – association areas

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Phineas Gage

Gage was a railroad construction foremanAn 1848 explosion forced a steel tamping rod through his head

Others said he was “no longer Gage” – previously mild-mannered/friendly and became ill-tempered and undependable

Lost his job, worked as a sideshow exhibitLearned frontal lobe effects personality

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Brain Reorganization

Plasticity the brain’s capacity for modification, as evident in brain reorganization following damage

especially in children other brain areas learn to control functions

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Our Divided Brain

1. our brain is divided into two hemisphere

2. left hemisphere processes reading, writing, speaking, mathematical, comprehension skills

3. right hemisphere is typically responsible for spatial relationships and analyses

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Functions Left Brain Right Brain

Logic

Words

Parts and specifics

Analysis (breaking apart)

Sequential thinking

Tends to be time-bound

Governs right side of your body

Emotions

Pictures

Wholes/relationships among parts

Synthesis (putting together)

Simultaneous and holistic thinking

Tends to be time free

Governs left side of your body

Higher levels of norepinephrine Higher levels of dopamine

Prove it to me! Anything is possible!

•A number of brain scan studies have shown normal individuals engage their right brain when they engage in a perceptual task, (see it)•and •left brain when carrying out a linguistic task (say it)

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Q: Assuming this comical situation was factually accurate, what Cortical Region of the brain would these doctors be stimulating?

Copyright: Gary Larson

Split Brain ProcedureThe two hemispheres of the brain are isolated by cutting the connecting fibers between them.

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Divided Brain – Split brain

Lateralization of Function1. Damage to the corpus callosum interferes

with the exchange of information between right and left hemispheres.

2. Epilepsy is a condition characterized by repeated episodes of excessive synchronized neural activity.3. Mainly due to decreased release of the inhibitory neurotransmitter GABA.4. Physicians once cut the corpus callosum to

prevent seizures35

Lateralization of Vision

1.The left half of each retina connects to the left hemisphere (right visual field)

2. The right half of each retina connects to the right hemisphere (left visual field)

3. Half of the axons from each eye cross to the opposite side of the brain at the optic chiasm.

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Left visual field

Visual input with split-brain – Roger Sperry and others

Split-Brain Experiment

1. Subjects were presented information to one or the other side of their brains

- (right: hammer/left: cow)

2. Patients identified verbally the pictures to the right visual field (hammer)

3. When patients were asked to point to the image seen on left, patients point to the picture on left w/left hand (cow)

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What should this person be able to do?

With the corpus callosum severed

objects (apple) presented in the right visual field can be named.

Objects (pencil) in the left visual field cannot

But left hand can touch it!!

Split Brain

Split-Brain Experiment

Results Sperry Experiments on Split Brain1. Roger Sperry (1974) revealed subtle behavioral differences for split brain people.

2. Because the left side of the brain is dominant for language in most people, most split brain people:

3. Have difficulty naming objects briefly viewed in the left visual field.

3. But yet can touch the object w/ left hand!!38

Try drawing two shapes with both of your hands simultaneously.

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What happens when we confuse our brains????

LOOK at the chart on the right say the word from left to rt. (make many mistakes?)Now say the color…(make many now???)The left brain will try to say the color while the right brain will read the word!

If the woman appears to be rotating clockwise you tend to be right brain dominant.

If the woman appears to be rotating counter-clockwise you tend to be left brain dominant.

If the woman seems to change the direction of her rotation back and forth you are one of those rare individuals who use both side of their brain equally.

We all, of course, what hand we are…when we hold a pen, but how far does this bias extend throughout your body?

Are you left-eared? Left eyed? Let’s have some fun...For a change!!!

Imagine the centre of your back is itching. Which hand do you scratch it with?

Interlock your fingers. Which thumb is uppermost?

Imagine you are applauding. Start clapping your hands. Which hand is uppermost?

Wink at an imaginary friend straight in front of you. Which eye does the winking?

Fixate a small distant object with your eyes and point directly at it with your forefinger. Now close one eye. Now close other eye.

Which eye was open when the fingertip remained in line with the small object?

(When the other eye, the non-dominant one, is open and the dominant eye is closed, the finger will appear to move to one side of the object.)

Phantom Limb Syndromehttp://www.youtube.com/w

atch?v=8AcDXnzmsMchttp://nobelprize.org/educ

ational/medicine/split-brain/index.html

http://www.youtube.com/watch?v=MZnyQewsB_Y

What happens when lobes of the brain are injured?

Brain Structures and their Functions