PSYC211 - module 2 lectures

What does the CNS consist of?

brain - cortex and sub cortex, spinal cord

What is dorsal?

sensory/afferent information coming in

What is ventral?

motor output

Where does sensory information enter and motor information exit?

sensory information enters CNS via dorsal pathway of spinal cord, motor output exits CNS via ventral pathway of spinal cord

What is rostral?

towards beak, anterior

What is caudal?

towards tail, posterior

What are the terms of orientation in reptiles?

mapped on to reptiles, same terms of orientation apply throughout CNS

What is dorsal (orientation)?

superior

What is ventral (orientation)?

inferior

What are the terms of orientation in the CNS in humans?

anterior/rostral, dorsal/superior, posterior/caudal, ventral/inferior

What are the terms of orientation for the brainstem?

rotates 90 degrees, ventral, rostral, dorsal (cerebellum), caudal

What is lateral?

towards the side

What is medial?

toward the midline

What is ipsilateral?

on the same side

What is contralateral?

on the opposite side

What is sagittal?

cut down the middle/midline

What is coronal?

slice from side to side

What is horizontal/transverse?

horizontal slice

What is the cerebral cortex divided into?

4 lobes, frontal lobe, parietal lobe, occipital lobe, temporal lobe, insular cortex hidden inside the lateral sulcus

What is the longitudinal fissure?

separates two hemispheres

What is the lateral sulcus?

separates temporal lobe from frontal and parietal lobes

What is the central sulcus?

separates frontal and parietal lobes

What are the gyri in the frontal sulcus?

3 gyri, superior, middle, inferior, precentral gyrus and precentral sulcus

What are the gyri in the temporal lobe?

superior, middle and inferior gyri

What are the gyri in the parietal lobe?

postcentral gyrus, intraparietal sulcus separates superior and inferior portions of parietal lobe

What are the major gyri in the brain?

superior, middle inferior frontal and temporal gyri, precentral gyrus, postcentral gyrus

What are the major sulci in the brain?

superior and inferior frontal and temporal sulci, precentral sulcus, central sulcus, intraparietal sulcus, postcentral sulcus, lateral sulcus

What are the major sulci in the parietal lobe?

central sulcus, post central sulcus, superior and inferior parietal lobule, intraparietal sulcus

What are the main sulci in the parietal lobe?

postcentral sulcus, intraparietal sulcus

What is the corpus callosum?

C-shaped white matter structure, axons connect two hemispheres, main fibre tract that allows two hemispheres to communicate, need corpus callosum for normal cognition, eg language lateralised to left hemisphere, right hemisphere needs to know what’s going on and send info to language areas, bundle of axons

What is the cerebellum?

hanging off back of brainstem, responsible for balance, planning movements etc

What are the two divisions of the brain?

cortical - at level of cerebral hemispheres, conscious awareness, subcortical structures eg thalamus, unconscious awareness

What is the thalamus?

subcortical structure, one on each side of brain (left and right), quite large

What is the basal ganglia?

subcortical structures

What are the main structures of the basal ganglia?

caudate nucleus, putamen, globus pallidus, subthalamic nucleus, substantia nigra

What is the caudate nucleus?

another C-shaped structure, head body and tail, from frontal lobe to temporal lobe, part of basal ganglia, smaller as we move from thicker head region to body and tail

What are the structures in the brainstem?

midbrain, pons, medulla

What are the structures in the midbrain?

superior colliculus, inferior colliculus

What is the superior colliculus important for?

visual reflexes

What is the inferior colliculus important for?

sense of hearing, auditory reflexes

What is the ventricular system?

system of interconnected cavities/spaces filled with CSF

What are the ventricles?

lateral ventricles, third ventricle, fourth ventricle

What are the lateral ventricles?

C-shaped structures in each hemisphere, from frontal lobe → parietal lobe → occipital lobe → temporal lobe, very large cavities filled with CSF, connected with third ventricle via interventricular foramen

What is the cerebral aqueduct?

connects third ventricle to fourth ventricle

What are the divisions of the lateral ventricles?

anterior horn, body, posterior horn, inferior horn

Where is the anterior horn of the lateral ventricles?

frontal lobe

Where is the posterior horn of the lateral ventricles?

extends into occipital lobe

Where is the inferior horn of lateral ventricles?

in temporal lobe

What is white matter?

axons (myelinated)

What is grey matter?

cell bodies, eg at level of cortical layers or subcortical structures deeper within the brain, grey matter structures of basal ganglia

What is Brodmann’s map of the cerebral cortex?

map of the different areas of the brain, based on idea that different areas represent different microscopic appearances, related to what tissue is made of/structure

What are the differences between left and right on brain scans vs gross anatomy?

when looking at a brain scans, left and right are reversed, left hemisphere appears on the right, right hemisphere appears on left, gross anatomy - left on left and right on right side, not reversed

How many neurons are in the brain?

around 100 billion neurons

What percentage of the cells in the brain are neurons?

10%

What percentage of the cells in the brain are glia?

90%

What do glia do?

a number of different functions eg support neurons to function better, what glial cells are doing is really important

What allows cognition?

communication between neurons in the brain allows cognition (behaviours and thoughts), depends on activity of neurons as well as transmission of information between neurons, disruption of neuronal communication via damage, disease or drugs can affect perception, movement and cognition (impacts a variety of functions)

What are neurons?

basic signalling unit, critical to all our thoughts and actions, can look and function differently in terms of what they’re trying to achieve, distinguished by function location and interconnectivity, receive information, process it and transmit output to other neurons, billions of neurons many interconnected allowing for connections in our brain that lead to complex cognitive abilities

What is the function of neurons?

communication via electrical and chemical signals

What is the structure of neurons?

dendrites, soma (cell body), axon, axon terminals

What are dendrites?

extend from cell body, receive inputs from other neurons/lots of neurons

What is the soma?

central part of the neuron, contains metabolic fluid and machinery that supports the neuron, surrounded by the cell membrane, interconnected with axon

What is the axon?

extends from cell body, where electrical activity can be transmitted, functions like a telegraph wire sending electrical impulses to distant sites in the nervous system, vary in length from less than a millimetre to over a metre, some covered in myelin, chemical input converted into electrical signals, shoots down axon, speed of conduction influenced by whether axon is myelinated

What are the features of neurons communicating locally?

short axons

What are the features of neurons communicating over large distances eg movement in toe?

long axon

What are axon collaterals?

branches of the axon, axons often branch, multiple axons in multiple directions, allows for communication with other neurons

What is the function of myelination?

speeds up signal conduction

What is myelin?

fatty substance that surrounds and insulates axons, facilitates conduction of nerve impulses (speeds up signal), appears white, formed by oligodendrocytes, oligodendrocytes wrap themselves around the axons

What happens in multiple sclerosis (MS)?

demyelinating disease, oligodendrocyte processes myelinating axons start coming off, destruction of myelin, impacts are quite serious, insulation comes off nerve fibres/axons, disrupts normal neuronal function, higher prevalence of MS in NZ than some countries - closer to the poles, similar to UK

What are axon terminals?

axons end at axon terminals, where axon comes into contact with another neuron and transmits information to it, point of contact - synapse, electrical signal shoots down to axon terminals, where chemicals (neurotransmitters) are released into synaptic cleft, each neuron receiving information from lots of different neurons, able to send output to lots of neruons with enough input

What is a synapse?

where the axon terminal of one neuron contacts another in order to transmit information, has two sides - presynaptic and postsynaptic, not touching each other (proteins), electrical signal shooting down presynaptic neuron causes synaptic vesicle to mobilise and fuse with membrane releasing neurotransmitter into synaptic cleft, information flows down the axon of presynaptic neuron and received at dendrites of postsynaptic neuron, information flows from presynaptic neuron to postsynaptic

What is the presynaptic neuron?

everything before the synapse, eg axon terminals

What is the postsynaptic neuron?

everything after the synapse, eg dendrites on postsynaptic neuron

What is the synaptic cleft?

space between neurons, axon terminals not touching dendrites communicating with

What happens in communication at the synapse?

electrical signals converted into chemical signals at the axon terminal, combination of electrical and chemical signal conduction causes mobilisation of vesicles and release of neurotransmitter (chemical signal), binds to receptors on postsynaptic neuron usually at dendrites, allows for chemical transmission of information, converted back into electrical signal on postsynaptic membrane

What are the features of neurotransmitters?

stored in and released from synaptic vesicles within axon terminal, different neurotransmitters used by different types of neurons eg dopaminergic neuron communicating via dopamine

What happens in neuronal communication?

synaptic vesicles fuse with membrane and spill contents into synaptic cleft, neurotransmitters bind to postsynaptic neuron

What are the features of glial cells?

account for more than half of the brain’s volume, support neurons, 90% of brain tissue, smaller in size compared to neurons, need more of them, do a lot more than just support

What are the main types of glial cells in the CNS?

astrocytes, oligodendrocytes, microglia

What are the features of astrocytes?

important in the blood brain barrier - protects CNS from some molecules in bloodstream, want it to work properly to keep molecules that can harm the brain out, protect brain tissue from molecules that may be in blood that should not cross BBB, some molecules can cross eg drugs that can influence brain can cross BBB - recreational drugs, drugs to help with brain diseases

What are the features of oligodendrocytes?

myelinated axons, form myelin by wrapping cell membranes around axon during development, important in MS for proper neuronal function, speeds up conduction, each oligodendrocyte myelinated multiple axons/bunch of axons, each axon myelinated by lots of oligodendrocytes, some axons may be really long and may need lots of oligodendrocytes to myelinate them

What does the myelination of one axon require?

many oligodendrocytes, each oligodendrocyte myelinating more than one axons

What is the function of microglia?

devour and remove debris left by dead or degenerating brain cells, important following damage to brain tissue, come in and engulf dead tissue to clean up the area, eventually end up with fluid filled hole in head

What is synaptic transmission?

neuronal communication, transmission of information at the synapse

What happens in synaptic transmission?

each neuron can receive input from many different neurons and can send output to many different neurons, may be neurons in different areas of the brain - allows for complexity of processing of neurons, when an individual neuron receives input can fire an AP - trigger synaptic transmission, chemical transmission of the signal from the presynaptic neuron leads to continuation of the signal, eg see something that requires action, interconnected with motor areas, capability of responding to visual information due to interconnectivity, visual information can make its way to motor cortex, causes muscles to move etc

What are neuronal circuits?

lots of neurons interacting and going through synaptic transmission

What is an action potential?

rapid change in voltage of cell’s membrane, neuron said to have fired when an AP occurs eg at a rate of 10 spikes/second (10 APs per second), can be elicited artificially

How can action potentials be elicited artificially?

can inject current into neurons and say how fast they fire in response to injected current, recording change in voltage, one electrode stimulating neuron with electrical current, other electrode recording voltage of neuron, when electrical current injected into neuron (top trace) neuron fires an AP (bottom trace)

What normally causes action potentials?

start firing in response to external stimulation or in response to internal thoughts, sufficient input triggers an action potential (eg above threshold), eg moving a whisker on a rat caused a neuron in somatosensory cortex to fire 100 APs per second

What is single cell recording?

recording action potentials from an individual neuron

What happens in single cells recording?

can measure activity of an individual neuron while different stimuli are viewed, might pick up activity from multiple neurons, recording from a single neuron or mostly from a single neuron - may be one or two nearby that are picked up, eg electrode impaling neuron in visual cortex

What is a receptive field?

region of space in which visually sensitive cells/neurons in visual cortex respond to stimuli, each neuron sensitive to a particular region of space in visual cortex

What are the features of a receptive field?

key is to work out where visual neuron receptive field is, each neuron in visual cortex only responsive to a small part of visual field, moving eyes/body - visual field shifts, which part of visual field is particular neuron responsive to

What is critical in single cells recording?

critical that visual field doesn’t change in this type of research (static visual field)

What happens in single cell recording eg with monkeys?

goal is to record from a single neuron, monkey required to maintain fixation and stimuli presented at various positions in visual field, stimulus position that causes the neuron to fire fastest defines neurons receptive field, see how the neuron responded when there was a rectangle of light in a particular region, less response when white bar was near space/partially overlapping, neuron may fire at a rate anyway without stimulus present

What is neural cell representation?

lots of neurons within a region of the brain, activity in populations of neurons

What are maps of neural activity?

while viewing stimulus on left monkey was injected with a radioactive agent to stain neurons that started firing and where they were, monkey looked at image, metabolically active cells/cells that fired APs in response to image in primary visual cortex absorbed the agent revealing that the organisation of the cells in V1 represents visual field/similar to what monkey was looking at, invasive experiment that involved killing the monkey - not legal in NZ, population of neural activity in visual cortex, can look at activity patterns across lots of neurons

What can fMRI be used for?

to understand how many neurons are responding when looking at an image, allow detection of the entire neuronal population responding to each stimulus, fMRI records changes in metabolic activity in order to produce a functional view of the brain, signal proportional to neuronal activity - can be used to estimate number of neurons involved in specific cognitive process

What did the fMRI experiment that looked at the number of neurons involved in representation of a single image show?

scanned visual cortex while the participant viewed an image of a house, face, or grading, around 200 million neurons responded when each of the people viewed these types of stimuli, each individual neuron may not be that important, large amounts of neurons important, huge amount in cortex involved with visual processing/representation of an image

Where is the primary auditory cortex?

hidden within superior temporal gyrus within central sulcus