introduction to brain anatomy
DESCRIPTION
Introduction to brain anatomy. The brain. The brain in FSLview. sagittal. coronal. ACPC. axial. Terminology. Dorsal/superior. Right?. Rostral /anterior. Left?. caudal/posterior. Ventral/inferior. Superior/Dorsal surface. Inferior/Ventral surface. Anterior. Anterior. Rostral. - PowerPoint PPT PresentationTRANSCRIPT
Introduction to brain anatomy
The brain
The brain in FSLview
coronal sagittal
axial
ACPC
Rostral/anterior
caudal/posterior
Dorsal/superior
Ventral/inferior
Left?
Right?
Terminology
Left Right Right Left
Posterior PosteriorCaudalCaudal
Superior/Dorsal surface Inferior/Ventral surface
Rostral RostralAnterior Anterior
The brain is full of neurons. These are organised into two types of “tissues”: - Grey Matter - White Matter
Grey Matter
White Matter
MRIPost-Mortem
Neurons
Constituent Tissues
Parts of the Brain
The human brain is big and most of it is cortex
Cerebral cortexCerebral cortex
• Makes up the bulk of the brain in humans• Newest part of the brain (in evolutionary terms)• Does thinking• Also most adaptable and variable part of brain
Two major modulatory systems
cerebellum basal ganglia
Principle of organization:The cortex has sub-regions with different functions
Lateral surface Medial surface
Central sulcus
Sylvian fissure
frontal .
The cortex can be divided into 4 lobes
parietalparietal
occipitaltemporal
occipital
frontal
You should memorize these!
Lateral surface Medial surface
Central sulcus
Sylvian fissure
The cortex can be divided into 4 lobes
parietalparietal
occipitaltemporal
occipital
frontal
You should memorize these!
frontal
Brodmann’s areas –(1909) • Divides cortex into 52 areas
• Based on cytoarchitecture (which types of cells are present?)
• Largely symmetrical (across two cerebral hemispheres)
Don’t try to memorize these!
Modern cytoarchitectonics – Jülich atlas
• Based on 10 brains• Registered into MNI space (affine)• Available in FSLview (atlas tools)
• Disadvantage – subjects have to be dead
Gross anatomical features(sulci and gyri)
e.g. Harvard-Oxford atlas in FSLview
Problem – gyri do not correspond to functional regions
Even if we could work out correspondence in one person,gyrification differs between individuals
Principle of organization:Function and connectivity are linked
Function and connectivity are linked
Johansen-Berg et al (2004) PNAS 101(36):13335-40
• SMA and pre SMA
• No obvious anatomical boundary
• Different functional regions (top row) – for finger tapping and counting backwards in 3’s
• Connectivity (DTI) based parcellation (bottom row)
• Structure and function same dividing line between SMA and pre SMA
Naming brain regionsA number of different systems are in use, most are arcaneMany areas will have a number of roughly-corresponding names
1. Brodmann areas (but only some of these are in common use)2. Descriptive anatomical names e.g. dlPFC
Decoding: dl PF C
… but beware, some of these anatomical descriptions relate to the monkey brain!!!
3. Descriptive names (often in Latin, e.g. cingulate)4. Functional names, e.g. visual cortex
d=dorsal, v=ventrall=lateral, m=medial
prefrontal
cortex
Monkey brain areas may have homologues in the human brain
Not quite that simple…
Humans ≠ monkeys
Principle of organization:The brain contains maps of the outside world
Sereno et al 1995
• Size of representation proportional to sensory/motor acuity• Adjacent parts of body are generally adjacent
The brain contains maps of the outside world1. Somatotopy
The brain contains maps of the outside world2. Retinotopy
Dougherty et al (2003), Journal of Vision 3(10):586-598
What about sub-cortical brain areas?
What about the sub-cortical brain structures?Some software only shows the cortex
Freesurfer Caret
Advantage: can do cortical flattening,easier to compare
cortical surface
Disadvantage: gets rid of sub-cortical systems
Two major modulatory systems• Both interact heavily with cortex• Not just involved in motor system
cerebellum basal ganglia
Basal ganglia Pharmacological diversity
Many neurotransmitters and neuromodulators
Imbalance linked to psychiatric disorders
Two antagonistic pathwaysDirect and indirect
Imbalance leads to disorders of movement and cognition
Parkinson’s diseaseHuntington’s disease
CerebellumExtremely regular micro circuitryContains 50% of brain’s neuronsImportant for motor coordination but not only that
Principle of organization:Parallel circuits between cortex
& subcortical structures
Subcortical-cortical loops1. Thalamus
• Correspondence between cortical regions and thalamic nuclei• They have reciprocal connections (thalamo-cortical and cortico-thalamic)• Thalamus also relays information from senses, basal ganglia and cerebellum to cortex
Behrens et al (2003). Nat Neurosci. 6(7):750-7.
Subcortical-cortical loops2. Basal ganglia
Draganski et al (2008) J Neurosci. 28(28):7143-52
Subcortical-cortical loops3. Cerebellum
Lobules of the cerebellum connect to different cortical regions
Dum and Strick (2003) J. Neurophysiology
Principle of organization:Loops between cortex & subcortical structures
• Each subcortical structure has a different contribution to information processing
• This information processing function may be applied to many cortical areas
• We can see many of the same principles of organization (functional localization, somatotopy) in subcortical structures
• The corresponding bits of cortex & subcortical structures are interconnected in parallel & integrative loops
Top tips for finding your wayaround the brain
How to identify brain structures:1. Use a brain atlas
How to identify brain structures:
2. Use the atlas toolbars in FSLview
How to identify brain structures:
3. Use a neuroscientist
Using a brain atlas
These generally have axial, sagittal and coronal views
Some structures are easier to identify in one view than another
There are specialized atlases for some structures e.g. cerebellum and brainstem
Central sulcus
Find the central sulcus in the axial view
Find the intra- parietal sulcus in the coronal view
The end!
The brain