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Basic Anatomy

Chris Rorden– Coordinates– Cortex

Brodmann Areas Common Names Talairach Coordinates

– Best web site: www.anatomy.usyd.edu.au/glossary/

www.mricro.com

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Relative Coordinates

On the globe we talk about North, South, East and West.

Lets explore the coordinates for the brain.

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Multiple Choice

Which arrow points dorsally?A. Red

B. Green

C. Blue

D. Red and Green

E. None of above

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Multiple Choice

Which arrow points dorsally?A. Red

B. Green

C. Blue

D. Red and Green

E. None of above

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Orientation

Human anatomy described as if person is standing

If person is lying down, we would still say the head is superior to feet.

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Orientation - animals

Cranialhead

Rostralbeak Caudal

tail

Dorsalback

Ventralbelly

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Coordinates – Human

Human dorsal/ventral and rostral/caudal differ for brain and spine.– Head/Foot, Superior/Inferior, Anterior/Posterior not ambiguous.

DorsalVentral

Dorsal

Ventral

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Anatomy – Relative Directions

Posterior <> Anterior

Pos

teri

or <

> A

nte

rior

Ven

tral

<>

Dor

sal

lateral < medial > lateral

Anterior/Posterioraka Rostral/Caudal

Ventral/Dorsalaka Inferior/Superioraka Foot/Head

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Coordinates - Anatomy

3 Common Views of Brain:– Coronal (head on)– Sagittal (profile)– Axial (bird’s eye), aka

Transverse. The book calls this ‘Horizontal’ but it is not horizontal when we are lying in a scanner.

sagittalcoronal

axial

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Coronal

Corona: ‘crown’ a coronal plane is parallel to crown that passes from ear to ear– Coronal cut creates anterior, posterior portions

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Sagittal

Sagittal – ‘arrow like’– Sagittal cut divides object into left

and right– sagittal suture looks like an arrow.

top view

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Transverse

Transverse: perpendicular to the long axis– These cuts are also referred to as Axial.

Example: cucumber slices are transverse to long axis.

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Oblique Slices

Slices that are not cut parallel to an orthogonal plane are called ‘oblique’.

The oblique blue slice is neither Coronal nor Axial.

Ax

Cor

Oblique

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Anatomy

Brain Planes Axis of left/right plane easy to defineWhat is the axis for axial plane?

?

?

?

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Bicommissural plane

Axis for axial plane is defined by anterior commissure (AC) and posterior commissure (PC).

Both are small regions that are clear to see on most scans.

AC

PC

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Distance from midline

– Medial – near sagittal midlineOptic chiasm C medial of eyes

– Lateral – far from sag. MidlineEyes are lateral of optic chiasm

– Ipsilateral – same sideDamage to A will cause blindness in ipsilateral eye

– Contralateral –different sideDamage to D will lead to a contralateral field cut.

– Note: after brain injury (lesions) we talk about contralesional and ipsilesionalDamage to visual cortex G leads to problems with contralesional vision.

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Relative positions

Distance From Body– Proximal, Central: near center of body

Think ‘proximity’ Shoulders are proximal parts of arms

– Distal,peripheral: away from body Think distant Fingers are distal parts of the arms

Distance from Surface– Superficial, external: near surface

The bump bruised superficial tissue.

– Profound, deep: far from surface The car crash injured deep organs.

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Neuron: Cell which is responsible for receiving, transmitting and synthesizing information– cell body: contains organelles for metabolism and

a nucleusGlial Cells: Support cells for Neurons

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The cortex

Cortex – ‘Bark’ shell of brain~80% of human brain

~20% of squirrel brain

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The big folds

The folds of your brain are like a fingerprint – there are a few general patterns, with individual variability.

Two main folds– Central Sulcus

Fissure of RolandoRolandic sulcus

– Lateral sulcusSylvian fissure

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Describing cortex location

Brodmann Areas (BAs, 1909)Appearance of cortex under microscopeNot necessarily function

Arbitrary numbers are hard to remember

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Brodmann Areas

Function does not necessarily follow appearance.

Some key areas:44: Broca’s Area

22: Wernicke’s Area

17: V1 Primary Visual

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Brodmann Areas (medial slice)

Note that gray matter is located in the longitudinal fissure (between the two hemispheres)

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Squirrels vs humans

squirrel brain– Surface of human brain

is grooved.– Surface of brain from

many animals is flat.– If we completely flattened

a squirrel brain, it would be the size of a stamp.

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Cortical folding

Cortical folding increases surface area.Ridges are called Gyri (singular = Gyrus)

– Greek gyros = circle, hence a coil of brain cortexValleys are called Sulci (singular = Sulcus).

– Latin = a groove.

Gyri

Sulci

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Anatomy

Surface of human cortex and cerebellum is very folded– Flattened, each hemisphere 1100cm2

– Cerebellum is also 1100cm2

Crumpled shape hides size of cortex– Compare Folded/Unfolded (from Marty Sereno)

HumanChimpanzeeMonkey

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Cortical Names

Much of cortex referred to by combination of coordinate+lobe+gyrus

E.G. Superior Temporal Gyrus (STG)

Middle Temporal Gyrus(MTG)

Lateral Occipital Gyrus (LOG)

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Cortical names

Tip of an object called a ‘pole’Frontal PoleTemporal Pole

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Sulci names

Many of sulci referred to by combination of coordinate+lobe+sulcus– Superior temporal sulcus (STS)– Inferior frontal sulcus (IFS)

– Precentral and postcentral sulciare just anterior and posterior to the central sulcus.

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Brain function

Anatomy is interested with the structure of an organism.

Physiology is interested in the function of the structure.

We are still learning about brain function

Modern maps of brain function are primitive…

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Brain function

Much of the primate cortex devoted to vision.

In some monkeys, up to 50% of neocortex is devoted to vision.

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Brain function

Two striking features of human brain

1. Lots of cortex ‘left over’ (yellow)not devoted to specific task – we are flexible

2. Not much of the cortex is solely devoted to language.

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12

3

4

A B

C D