Lecture 1: Neuroanatomy Flashcards
Anatomical Orientations
Anterior = rostral:** near the front**
Posterior = caudal: further back in position
Superior = dorsal: higher up
Inferior = ventral: lower down
Lateral: towards the side
Medial: towards the midline
Cuts
(different ways to “slice” the brain)
- Sagittal means to cut from left-to-right, or right-to-left
- Coronal means to cut from front-to-back, or back-to-front
- Horizontal/axial means to cut from top-to-bottom, or bottom-to-top
- Mid-sagittal is a sagittal cut whereby you completely separate the two hemispheres
Brain Structure
The brain has two hemispheres. The left and right brain have different functions but are complementary.
Important parts:
- Grey matter
- White matter
- Cerebrospinal Fluid (CSF): protect brain from injuries.
- Cerebellum: associated with motor control
The brain has two components. What are they?
- Grey matter
What makes grey matter grey?
The density of the billions of cell bodies of the neurons
-Neurons, glial cells (support the neurons and their survival)
- In terms of Grey matter, we will be focusing on the cerebral cortex: the seat of higher cognitive processes/ functions (allows us to have human cognition)
- It is a ribbon of tissue that covers/encases the two hemispheres
- About 2 mm thick (not super thick)
- Subcortical structures: more primitive functions (e.g., breathing, heart rate, alertness, etc.).
- They are called subcortical because it is grey matter below the cortex; embedded in white matter as nuclei that have specific functions
- White matter
What makes white matter white?
- Myelin sheath → a fatty substance to enhance the conduction of the electrical signal down the axon terminal
- It is made up of the axons of the neurons
- Allows neurons to connect/communicate with other neurons.
The neuron
- Soma/cell body (grey matter) is where you have your DNA.
- Branches coming from the soma are called dendrites, they receive information from
other neurons and input that info to the cell body - Axon (white matter): long branch with terminal buttons at the end that connect to other neurons
Myeling sheath
→ allows fast conduction (communication)
→ helps neural impulse (jump from one axon to another).
Synapses:
- Where two neurons communicate
- Neurotransmitters
How do neurons communicate?
- The main message the neuron gives and receives are action potentials.
- When we talk about action potential we refer to it as “all or nothing”. If the threshold is reached, action potential is fired.
- The amplitude of the neural impulse does not change. It is the frequency of the neural impulse (series of action potential).
Cerebral cortex
Technically, it is a continuous sheet of tissue, but it is not homogenous (consisting of parts of all the same kind) → it has cytoarchitectonic areas.
- Different types of cells, different layers, different cell densities.
- The cerebral cortex has expanded immensely over evolution.
Why is it folded?
To fit into our skull (skull has to fit into birth canal).
- The human cortex is the most convoluted of any primate brain
- In other words, we have the most folds in our brain.
- The cortex is folded into: sulci, gyri, and fissures.
- We use them as landmarks to navigate the brain.
Sulci
- Are used as landmarks to seperate the brains into subregions.
- They each have a name
- Fissures = deeper
- Sulci = more superficial
People have been trying to map out the sulci and gyri of the brain for decades. Why?
- More than 50% of the cortex is hidden within the sulci.
- Certain sulci and gyri make great functional landmarks.
Athough there is a lot of variability there are certain sulci that we know to be consistent across the brain.
Why do we care about cortical folds?
- Approximately 2/3rds of the cortex is hidden within sulci and fissures!
- Many folds form consistent patterns across individuals (e.g., central sulcus, lateral sulcus,
inferior frontal sulcus, etc.) - Certain sulci/gyri show strong relations to specific functional processes
sulci/ fissures that seperate the lobes
Sylvian fissure/Lateral Sulcus separates the frontal from the temporal lobe and a little bit of the parietal lobe.
- Fissure is just another word for VERY deep sulcus in which you have a lot of cortex hidden within in (you cannot see it from the lateral view)
The Central Sulcus separates the frontal lobe from the parietal lobe
- The real sulcus is NOT straight like in that diagram – it has lots of twists and turns
Parieto-occipital fissure is mainly a medial sulcus and it is really deep
- However it does come out onto the lateral surface so we can use it to separate the parietal lobe from the occipital lobe in this splice.
Pre-occipital notch (in front of the occipital lobe)
- Notch means indentation
- If you connect this notch to the parieto-occipital fissure you can separate the occipital lobe
Temporal lobe
At the base of the brain; right by temporal bones
1) Resonsible for Auditory processing
→ Primary auditory (BA 41, 42)
→ Secondary auditory area (22): allows you to undertand speech and process info
2) Wernicke’s area for language/speech comprehension
→Posterior temporal
3) Ventral stream of vision – “what” pathway
- allows us to recognize objects, faces
- comparison between something we know and something we are seing.
- Smell processing (medial side)
- Memory consolidation (medial side)
4) Hippocampus
- memory
The parahippocampal gyrus (in temporal lobe)
all around the hippocampus (important in memory). The different functional areas within the PHG are:
- Posterior part = Parahippocampal cortex
- Anterior part = Rhinal cortex
→entorhical cortex
→perirhinal cortex (hidden within the sulci)
- Piriform cortex = sense of smell
Amygdala
- Found in front of the hippocampus
- Associated with memory, emotions, fear processing, response to stress.
- Subcortical structure in the temporal lobe.
Smell
The fact that the amygdala, piriform cortex and hippocampus are anatomically close together explains why smell allows us to retrieve memories (smell associated with memories). All three of these are connected together.
Sense of smell → Memory → Emotions
Temporal lobe Sulci and Gyri
Lobes of the brain
What is the importance of the sulci?
Cortex is not just at the surface of the brain. There is a lot of cortex within the sulci.
How are the two hemispheres connected?
- Left and right part of cortex does not touch each other (grey matter does no touch)
- The two hemispheres are connected by bundle of axons.
- Short range connection and long range connectuon between the 2 hemispheres.
Frontal lobe
- Very large, complex functions (language, executive function, decision making, planning)
- Frontal lobe of humans is much more developed than other species.
Primary functions:
- Voluntary motor control: has the motor cortex.
-primary motor cortex M1(area 4)
-premotor cortex(area 6) = motor output of speech
- Working memory functions (monitoring/tracking information, selective attention, active memory retrieval)
- Broca’s area for speech production in the left hemisphere.
- The frontal lobe is also important in reasoning and emotional processsing, impulse control.
→ Frontal lobe is the last to develop. This is why children are not good att decision making, impulse control (even teens).
→ Prefrontal cortex does not stop developing until 25.
Frontal lobe Sulci and Gyri
Sulcus or fissure is the valley and the walls of the valley are all cortex, whereas the gyrus is the bump of tissue.
- SFG = superior frontal gyrus (everything that is dorsal to the superior frontal sulcus)
- IFG = inferior frontal gyrus is ventral to the inferior frontal sulcus
- MFG = middle frontal gyrus (difficult to place it because there are so much sulci and gyri
in this region)
- This is how we can break the frontal lobe down more so we can see how the sulci and gyri are related to each other.
Breaking down the inferior frontal gyrus
Anterior ascending ramus of the lateral fissure is what separates the pars triangularis and the pars opercularis
- Pars = part
- Pars orbitalis is called that because it sits above the orbito-frontal cortex
- Horizontal ramus of the lateral fissure is what separates the pars triangularis and the pars orbitalis
Regions in the parietal lobe
- Somatosensory cortex: area 3 (basic sensory information), area 1 (vibration/texture, touch sensation) and area 2 (size/shape of objects)
- Spatial functions - posterior to the somatosensory cortex (posterior part of parietal lobe) Important in spatial function (where you are in space, where things are in space).
- Language (left): reading and writing, phonological and semantics.
- Dorsal stream of vision (where pathway - where things are in space). Starts in occipital and goes to parietal lobe.
- Multisensory integration: information from the senses - Parietal lobe is well located, right in the middle of the somatosensory auditory in the temporal lobe and visual areas of the cortex. This part of the cortex can integrate everything (use visual, auditory cues to orient yourself).
- Guide Motor Actions
Parietal lobe Sulci and Gyri (lateral)
- If you follow the lateral sulcus into the parietal lobe, that will be a very important landmark (supramarginal gyrus)
- If you follow the superior temporal sulcus it actually ends up in the parietal lobe, the cortex surrounding that sulcus is called the angular gyrus
- When it comes to reading, writing and spatial processes these areas become super important
- Intraparietal sulcus helps to subdivide what we call the inferior parietal lobule and the superior parietal lobule
Occipital lobe
- Primary visual area (V1: BA 17)
- where you process all the visual information. Information from the eyes goes to the occipital lobe, mainly V1 (V1 is at the very tip of the occipital pole).
- V1 processes the very basic visual informattion and transfers the information to the other secondary visual area.
- Secondary visual area ( V2: BA 18)
-
Associative visual areas (V3, V4, V5 (MT): BA 19).
- V2,V3,V4, ect receive the information to have a more fine grained analysis/ more complex analysis of the visual area.
- Processing of visual information
- Main Broadmann area of the occipital cortex is V1 (BA 17)
- hard to see lateral surface, look from medial part.
Limbic Cortex
- Group of regions that were identified by broca’s in 1878 and he identified those regions as important for emotion processing.
→ the “emotional brain” - Involved in behavioral and emotional; response, survival.
- Cingulate cortex
- Parahippocampal gyrus/ Hippocampus
- Amygdala: emotions, response to stress.
- The thalamus (sends output to the cingulate)
- Broca in 1878: the great limbic lobe inclused the cingulate and the importamnce for emotion processing → Papez circuit.
- These areas are close to the midbrain. In terms of evolution, they are old brain region.
Operculum
- Part of the cortex that covers the insula.
- Frontal Operculum
- Parietal Operculum
- Temporal Operculum
The basal ganglia
subcortical structure
A group of subcortical nuclei:
- Striatum → involved in initiation and regulation of movements: muscle tone, posture, involuntary movemnets, motor learning (swimming, tennis, ect). Motor learning.
- a part affected in Parkinson’s disease
Includes:
- Putamen and Caudate Nucleus
- Globus Pallidus (“pale globe”)
- Amygdala → part of basal ganglia:
memory, emotions, fear.
- Nucleus accumbens → pleasure, reward system, motor functions.
Cerebellum
subcortical structure
- Involved in production of movement (adjustments, speed,initiation, precision, modulation)
- Balance, posture, coordination
- Motor learning
Lateral surface view of the brain, label this image.
A = pars triangularis
B = central sulcus
C = post-central sulcus
D = inferior frontal sulcus
E = occipital Lobe
F = cerebellum “little brain”
G = middle temporal gyrus
H = lateral sulcus (aka Sylvian fissure)
I = pre-central gyrus
J = supramarginal gyrus
Medial surface view of the brain, label this image
A = corpus callosum
B = parieto-occipital fissure
C = calcarine sulcus (in that sulcus is V1)
D = lingual gyrus
E = parahippocampal gyrus
F = cingulate sulcus
G = cingulate gyrus
H = collateral sulcus
What is the peri-central region
Spans the frontal and temporal lobe
- Importance of this area stems from the work of Dr. Penfield
- Dr. Penfield mapped these regions and helped us understand how this cortex is
organized
Parieto-occipital fissure
Parieto-occipital fissure has a lot of cortex hidden within it
- Gives us an area of cortex that kind of looks like a wedge, that wedge is called the cuneus
- The region anterior to the cuneus is called the pre-cuneus
- Ventral to the calcarine sulcus is the lingual gyrus
