Neuroscience Flashcards
What can the nervous system be split into (2 major systems)?
Central Nervous System
Peripheral Nervous System
What is part of the CNS
The brain and spinal cord
What is part of the PNS
Everything else which isn’t the CNS
What can the peripheral nervous system be split into
Sensory division
Motor division
What can the motor division be split into
Somatic nervous system
Autonomic nervous system
What does the enteric nervous system do
It is part of the autonomic system which is in charge of controlling the muscular contractions of the GI tract
Located in walls of the GI tract, and controls digestive activity (peristalsis and secretion of enzymes)
What can the autonomic nervous system be split into
Sympathetic
Parasympathetic
What is the function of the central nervous system
Various things like processing information and generating thoughts
What is the function of the peripheral nervous system
Sensory input and informational relay, as well as control of bodily movements
What is the function of the sensory division
This division is responsible for relaying sensory information of the body to the brain
Responsible for picking up sensory information
Also meant to detect internal stimuli
What is the function of the motor division
To be able to control aspects of the body’s movement / function
Carries out responses initiated by the CNS - transmits signals to allow for movement
What is the somatic nervous system
This aspect of the nervous system controls the voluntary movements of skeletal muscles
What is the autonomic nervous system
This aspect of the nervous system regulates the involuntary functions of various body parts
What is the sympathetic branch
This is responsible for the body’s ‘fight or flight’ responses - in other words it can stimulate heart rate, dilate pupils and inhibit digestions
What is the parasympathetic branch
This is responsible for the body’s ‘rest and digest’ responses - in other words it can help the body conserve energy and perform maintenance functions –> i.e. decreased heart rate, constricted airways, constricts pupils etc
WHat are the different forms of protection to the CNS
Bone
Meninges
Blood brain barrier
Explain the function of the bone in protecting the CNS
The bone acts as a structural barrier/protection from hard impacts or sharp objects
It is hard, dense bone which resists impact and external forces, which prevents direct trauma to the brain
Not only seen in brain, but also in the spinal cord, where it acts as a shock absorber in the spinal vertebrate to protect the spinal cord
Explain the components of the meninges and a brief outline of what it does
It is a flexible sheet between brain/spinal cord and bone, made from 3 membranes. Its aim is to protect the brain from damage from the skull (i.e. asudden impact causing the brain to jolt and hit the skull –> need some protection there)
There are 3 parts:
Dura mater
Arachnoid mater
Pia mater
Explain the function of the dura mater (what does it do)
This is the outermost and toughest of the 3 menginges, lying just beneath skull and vertebral bones
It is a thick, durable membrane made of dense fibrous tissue. It helps provide the initial guard against trauma
Explain the function of the arachnoid mater (what does it do)
It is the middle layer of the meninges, just under the dura mater. It is a web-like, thin membrane loosely covering brain and spinal cord
it also consists of the subarachnoid mater which is right below that layer of arachnoid, and is filled with cerebrospinal fluid (CSF), which helps cushion the brain and spinal cord
Explain the function of the pia mater (what does it do)
Is the innermost layer, adhering directly to the surface of the brain and spinal cord. It is a delicate membrane
Its function is to support blood vessels that supply the brain and spinal cord and works with other meninges to help protect CNS
Explain the function of the blood-brain barrier
This is a functional barrier rather than a structural barrier. It aims to shield the brain from harmful substances, whilst allowing essential nutrients to pass through
It works as the brain requires a lot of blood –> a lot of blood vessels surrounding it. These blood vessels have special, smaller walls, which restrict the entry of many chemicals into the CNS –> protects brain from chemicals, which is especially important as the brain is sensitive to toxins
The endothelial cells lining blood vessels in brain are packed tightly by tight junctions –. prevents movement of substances between them, thereby acting as a barrier preventing substances entering
What happens at the spinal cord level (in terms of reflex arcs)
Spinal cord is a cable of neural fibres with “roots” brnaching off
Provides an interfae between brain and the PNS
It enables reflexes to occur –> spinal reflex, and thus the reflex arc:
Stimulus –> receptor –> sensory neuron –> integration centre –> motor neuron –> quick response
Ultimately the spinal cord allows for reflexes, and also the executioon of bodily responses, and coordination of complex movements
What are the fluid filled cavities in our brain called
Ventricles
What is the function of the ventricles
Produce cerebrospinal fluid (CSF) which is essential for cushioning the impact that a brain/head might experience
They ultimately cushion and protect the brain, provide buoyancy, maintain chemical stability and distribute nutrients
What does the brainstem do
It is able to link the brain to the spinal cord. It controls the life supporting functions of the body
It is the ‘stalk’ the brain is connected to
Passes down the neck to spinal cord, and is thus responsible for the autonomic nervous system
What can happen to it after a head injury, and why would that be dangerous
After a head injury, it could pose a risk to the brainstem. This could lead to being disabled or even death in extreme cases
Where is the cerebellum located
It is at the back of the brain and is inferior to the occipital and temporal lobes
What does the cerebellum do
It is responsible for controlling movement (voluntary), balance, and motor learning. thus, it receives a lot of the sensory input (auditory and visual input)
It contains 70% of the brains neurons, even though it only takes up 10% of the brains space.
What structures sit at the centre of the brain and on top of the brainstem
Thalamus and hypothalamus
What is the function of the thalamus
It is responsible for some sensory processing / sensory relay to cortex and also control of sleep
What is the function of the hypothalamus
Hypothalamus is responsible for maintaining homeostasis, and thus initiates the release of hormones in the body
What parts of the brain make up the limbic system
Cingulate cortex
Hippocampus
Olfactory Bulb
Amygdala
What is the function of the limbic system
Emotional processing, memory and motivation
What is the function of the cingulate cortex
This is related to emotions and also pain regulation/response (?!)
WHat is the function of the olfactory bulb
It receives the signals associated with smell and provides a short way for it to link to the amygdala (smell bypasses the thalamus and goes straight to amygdala)
What is the function of the amygdala
Function is for fear response and emotion
What is the function of the hippocampus
Assists with being able to translate information in the short-term memory to long-term memory
What is the function of the basal ganglia
Action and thought
It helps with motor control, cognitive/emotional processes, and helps regulate motor movement and helps inhibit unnecessary or unwanted movements. Also helps with motor learning
Formation of habits as well
What are the components of the basal ganglia
Caudate, putamen and ganglia
What is the function of the caudate
Learning and memory
What is the function of the putamen
Works with caudate to regulate movement and influence learning
What is the function of the globus pallidus
Regulation of voluntary movement and motor learning
What is the neocortex
The convoluted folds on the top of the brain
Why is the neocortex wrinkled
To increase the surface area of the brain, and allow for different functions Otherwise, it is too big to fit on the top of our head
What are the lobes of the neocortex
Temporal
Frontal
Parietal
Occipital
What is the function of the frontal lobe
This is responsible for higher order processes, such as decision making, information processing
Also responsible for planning and executive functions
Motor control, language production and emotional regulation happening here as well
What is the function of the parietal lobe
Cruciail for processing sensory info, spatial awareness, and integration of sensory info
What is the function of the temporal lobe
In charge of auditory processing, memory and language
Also language comprehension here
What is the function of the occipital lobe
Responsible for visual processing
it interprets and integrates visual information, allowing for recognition of objects, perception of colours and depth
What connects your two hemispheres of the brain
Corpus Callosum - alows for communication between two sides of the brain
What happens as the nervous system becomes more complex
As nervous system becomes more complex, the complexity of the organism increases - they have more complex behaviours
What is the difference between vertebrates (w/ a bone) and non-vertebrates in terms of the nervous system
Vertebrates have a separation between PNS and CNS. Meanwhile. non-vertebrates don’t have this separation between PNS and CNS
How has the brain changed over the course of evolution
Over time:
Increase in size of forebrain for vetebrates
Frontal love has become bigger and more complex in humans
Temporal lobe has expanded
Increased myelinatin, allows for increased cognitive processing and reaction times
More neuroplasticity
What is the primary job of the neuron
To transmit information through nervous system via electrical impulses
WHat sort of signals does a neuron send
Since they are binary, they send either on/off signals
What is the resting state of a neuron - what charge does it have? Why?
What happens when a neuron becomes depolarised (how does it become depolarised)
Explain the process of repolarisation and its importance
How many states can a neuron have? What does this tell us about the sort of signalling they are capable of?
What is myelin? What does it do?
These of bundles of fatty, insulating substance that surrounds the axons of many neurons, and is essential for efficient communication between neuronsy conduction, which means that it allows for the electrical impulse to jump from one node of ranvier to the rest –> increasing speed of signal
Ultimatelyy reduces energy required for neuron to maintain its function
Look at the example of the importance of myelin in the two types of pain fibres
A - delta fibres (quickest pain fibres) are very myelinated, allowing for quick transmission of a pain response
C - fibres are unmyelinated –> slower signals –> dull aching –> “second pain”
How do neurons communicate with one another
Through the transfer of neurotransmitters with one another across a synapse
WHat is the synapse
These are small gaps or junctions between axons, and are where there is a transfer of neurotransmitters
The synaptic cleft is like 10-20 nm wide –> transmission is fast
What are the two types of neurotransmitters
Excitatory or inhibitory
Give an example of an excitatory neurotransmitter and how it works
Glutamate.
When Glutmate binds to the neurotransmitter receptor, it stimulates Na+ to enter the neuron. This depolarises a neuron, making it more likely to reach the potential threshold to trigger it to have an action potential
Give an example of an inhibitory neurotransmitter and how it works
GABA.
WHen GABA binds to the neurotransmitter receptor, it stimulates Cl- to enter the neuron. This further polarises a neuron by making it more negative, thus reducing its potential for a depolarising action
Why is it important to stop the effects of a neurotransmitter in the synapse
The effects of a neurotransmitter must be brief. If it is left in the synapse, there is a continual effect –> cant send new messages
How can the neurotransmitter in a synapse be stopped / end the effect associated with a neurotransmitter
It can be ended by enzymes in the synapse which destroy neurotransmitters, and others end it by reuptaking the neurotransmitters
Where/how do most psychoactive drugs work in the nervous system
They affect the functioning of neurons
They normally work by imitating or blocking neurotransmitters –> ultimately influences the release, uptake, enzymatic destruction or receptor binding of neurotransmitters
They normally work by interacting with neurotransmitters in synapse, where they can increase or decrease NT release, block or enhance NT reuptake or degradation. Mimic or block NTs at receptors. Influence ion channels to modulate neuronal firing
How can drugs interact with neurotransmission (recreational)
Opiates (heroin, morphine) mimic brains opioids NTs
Cocaine, amphetamines and ecstasy provide transission of dopamine, noradrenaline and serotonin
Nicotine - stimulates acetylcholine receptors
Caffeine - blocks adenosine receptors –> buildup of adenosine makes us sleepy –> we aren’t sleepy
How can drugs interact with neurotransmission (medicinal/therapeutic )
Benzodiazepines (eg valium) enhance inhibitory effects of GABA (as do barbiturates and alcohol)
Most anti-schizophrenic drugs block dopamine
Antidepressant drugs enhance serotonin and noradrenaline transmission (e.g. by blocking reuptake)
What are receptor activations and blockages called
Activation - agonist, blockage = antagonist
What is functional mapping
The mapping of the functions of the brain
What are some ways we could study the role of a specific part of the brain on our bodily functions
Lesion studies
Split Brain studies
TMS
Functional imaging (fMRI)
How can lesion studies identify the functions of different parts of the brain
Lesions are damage or removal of specific brain areas. This enables us to determine the role and its particular function. These could be natural lesions or animal studies (experimental)
Basically, after this we can see whether the removal has impacted a specific bodily function
How can transcranial magnetic stimulation (TMS) identify the functions of different parts of the brain
It basically involves sending an electrical impulse to a certain part of the brain. This stimulates a depolarisation in a part’s neurons. This should result in an involuntary action –> allows us to determine what part of the brain controls what actionn (briefly interfering with the functioning of a part of the brain)
What is electroencephalography (EEG)?
EEG involves placing electrode plates against the scalp and recording the electrical fields from the brain. This can help reveal patterns of brain activity during various mental states
What is the strength of EEG
It has high temporal resolution (i.e. it is good for tracking the timing of neuronal activity) - lag of ~20ms
What is temporal resolution
temporal resolution describes its ability to tell you exactly when the activation happened.
What is spatial resolution
spatial resolution refers to the capacity a technique has to tell you exactly which area of the brain is active
What is the weakness of EEG
It has poor spatial resolution - has difficulty pinpointing exact location of neural activity, because it detects signals from large populations of neurons –> blurred electrical signals so its hard to localise activity
What does fMRI measure? How?
Involves bombarding the head with high frequency radio waves, while inside a strong magnetic field, to measure orientations of protons (in water)
It measures changes in O2 in blood (due to differences in magnetic properties of O2 rich and O2 depleted blood) –> used to infer areas of activity in brain
“BOLD” response
(black = areas of water, white = lack of water)
WHat are the disadvantages of fMRI
Has low temporal resolution, as the “BOLD” response lags behind actual brain activity –> significantly lower temporal resolution than EEG
Reflects changes in blood flow, which have a lag of 1-5 seconds –> hard to capture changes in activity
What were the advantages of fMRI
Has good spatial resolution, as the process allows for a good visualisation to the structure of the brain, especially when combined with high quality anatomical MRI
What is magnetoencephalography (MEG)?
Similar to EEG, but measures magnetic fields from brain, isntead of electricity. Thus, it isn’t distorted by brainwaves, whereas electric fields are disturbed by them
Provides a 3D reconstruction of electrical activity to create a functional map of brain response
What are the benefits of MEG
High spatial and temporal resolutions
It is also completely non-invasive
What are the drawbacks associated with MEG
Extremely expensive
Equipment is really sensitive to any source of electromagnetic interference (e.g. from electrical devices) –> do a lot to magnetically isolate all devices from the MEG
WHat are the four regions of the hypothalamus which are involved in feeding
Lateral Hypothalamus (LH)
Ventromedial Hypothalamus (VMH)
Paraventricular nucleus (PVN)
Arcuate nucleus (Arc)
What is the function of the lateral hypothalamus in feeding
It is responsible for the initiation of eating behaviour. This is because destruction of LH causes rats to decrease eating dramatically
Also minor role in reward processing and motivation
What is the function of the ventromedial hypothalamus in feeding
Destruction of VMH makes rats overeat BUT not lack satiety. Meals are eaten in a normal size, but more frequent eating times –> overeating in a day
This could suggest that it is in charge of a ‘long term satiety’ i.e. satiety throughout a day
What is the function of the paraventricular nucleus in feeding
Meanwhile damage to PVN tends to cause rats to eat bigger meals. This is supposed to also address satiety, but might be considered ‘short term satiety’ - i.e. satisfaction after a meal, rather than in a day –> which is why it causes eating of bigger meals
PVN influences the HPA axis –. regulation of stress hormones. Destruction would lead to excessive eating
What is the function of the arcuate nucleus in feeding
The Arc contains two types of neurons. One type links to the Lateral Hypothalamus, which thus functions to control the initiation of eating.
Meanwhile, the other one links to the ventromedial hypothalamus and paraventricular nucleus, and thus functions to control the feelings of satiety and to stop eating
The arc has a ‘leaking’ blood brain barrier and neurons have receptors for hormones from gut (ghrelin, insulin), and fat (leptin) –> allows for control of eating behaviours
How can single cell recording/electrical stimulation work
Optogenetics and fibre - photometry (Ca++ imaging), microinjection into specifc region of brain to see what parts of brain is involved in certain activations
Can correlations between brain activity (EEG, fMRI, MEG) and psychological function prove causal links?
No. TMS can however (as it involves direct stimulation –> behaviour)
Do all animals sleep
Yes (even worms and jellyfish)
What influences how long animals sleep
it IS NOT size
Many factors such as:
Diet
habitat (comfortable habitat = more sleep)
Prey/predator status (predator = more sleep)
Social network (more complex = more sleep)
Metabolic rate
brain complexity (greater complexity = greater sleep)
Why is sleep considered an opportunity cost
Because its time not spent doing something, and it is also a period of time where they are vulnerable
What is sleep important for
Many brain functions like attention, speed, mood, memory etc
What are some of the known impacts of sleep deprivation
Greater chance of overeating (and also likely to become obese)
Increased activity in sympathetic nervous system (greater heart rate, worsened heart health, more heart attacks)
Cognitive impairment (decreased attention, memory, decision making/problem solving)
Emotional and mental health impacts (Mood disturbances, increased anxiety and depression, emotional regulation)
Physical health (decreased immune system, increased risk of CVD, weight gain)
What part of the brain is responsible for keeping us awake? What are the neurotransmitters involved
Acetylcholine neurons (pons)
Noradrenaline neurons (Locus Coernuleus)
Serotonin neurons (Raphe nuclei)
These neurons are active when we are awake, but are quiet when we sleep. Electrical stimulation of these neurons can wake a sleeping animal
What system controls our circadian cycle?
Our superchiasmatic nucleus controls the release of the hormone melatonin from pineal glands. This in turn has an effect on our circadian cycle/rhythm
Explain our circadian cycle/rhythm and how its influenced by melatonin and the SCN
Melatonin basically signals night-time to the whole body. This thus controls our circadian rhythm as its low in the day and increases during the night
SCN receives direct input from our eyes, particularly in response to light –> increased light entering inhibits production of melatonin
Also, just a bit of light entering allows for determination of internal clock, if not it is slightly over 24 hrs –> we need sunlight to fix our clock
WHat is jet lag caused by
When the circadian rhythm is synchronised to a previous time zone, and has to adjust to new environment’s day-night cycle.
As circadian rhythm isn’t adjusted, when it’s day, it could be night elsewhere –. release of melatonin –> sleepy time
What sends us to sleep?
Preoptic area (anterior hypothalamus). Destruction of this area can result in insomnia
Neurons in pre-optic area contains GABA which inhibits ACh, 5HT and NA arousal systems in brainstem –> turns off alertness, which helps us fall asleep
What causes ‘sleep pressure’? Explain the role of adenosine
Basically adenosine is a byproduct of neuronal activity, and builds up in the brain while we are awake. Being awake for too long –> increases amount of adenosine in the body. This increased adenosine increases sleepiness (“sleep pressure”) by inhibiting alertness centres (esp ACh in pons) and stimulating sleep centres (pre optic area)
Sleeping allows for the adenosine to be cleared up. Caffeine blocks adenosine receptors. When adenosine buildsup and binds to adenosine receptors, it causes sleepiness
What happens if we skip a night of sleep
increased adenosine and thus an increased sleep pressure
What happens to the EEG activity when we are awake
The elctrical activity in our brain is high frequency and “noisy”
What happens to the EEG activity when we are asleep
There is a slow rhythmic pattern of electrical activity in brain –> slow wave sleep
Deeper the sleep, the slower the activity.
This happens due to role of reciprocal connections between thalamus and cortex in orchestrating neuronal activity –> large and slow pattern of waves
During REM sleep, our brain waves become descynrhconised
What happens during REM sleep? What is it caused by?
Multiple times through the night, the brain waves become desynchronised, like when we are awake. During this period, eyes dart back and fourth –> REM
If woken up during REM, we report we are dreaming
REM sleep caused by neurons in Pons that contain acetylcholine and stimulate neurons in thalamus, which then project to visual cortex (which was previously inhibited) –> causes visual cortex to receive neuronal input –> illusion of dreams
During REM, various areas become very active; visual regions at back of brain, motor regions, and limbic system
During REM, there is a suppression of regions of frontal lobe which is important for logical reasoning -> explains why we have bizarre dreams but then think it to be real
ACh neurons in pons stimulate neurons in medulla –> inhibits motor neurons in spinal cord to cause paralysis except for eyes
Explain how amount of REM changes within a night
REM increases during the night
Explainn how amount of REM changes across the lifespan
Decreases across lifespan. Foetus has a lot of REM, 50% for newborns, and 20% for adults
Explain the concept of a reward
Acts as a motivation to engage in a particular behaviour to achieve a reward
Animals (including humans) act in order to receive rewards
Explain the neuronal mechanism of reward (Olds and milner experiment)
They accidentally implemented electrode in medial forebrain bundle (mfb) which is a bundle of noradrenaline and dopamine fibres travelling from brainstem to forebrain
This caused a rat to keep returning to the palce where it received the stimulation. They showed that rats with electrodes in mfb readily learn to perform many acts to receive that electrical stimulation (if allowed, they would do nothing else but press a bar which provides electrical stimulation in mfb)
What makes mfb so effective in rewards?
There are dopamine axons in mfb and they make the greatest contribution to rewarding effect of electrical stimulation
Basically, the rewarding effects of drugs rely on doapmine effect from the ventral tegmental area (VTA) which is in the midbrain and serves as dopamistic neural projections
Drugs like amphethamines and cocaine directly boost release of dopamine in mfb, and other drugs like heroin and nicotine indirectly increase dopamine
WHat does it mean by the control of the body being controlled by two cerebral hemispheres
Right hemisphere receives sensory input from left and controls motor response on left side of body
Left hemisphere receives sensory input from right and controls motor response on right side of body
Vision is a bit more complicated, with retina being split in each eye –> half goes to right and left hemispheres
What is lateralisation
Tendency for certain cognitive processes to be more dominant in one hemisphere than the other (i.e. a more dominant side)
I.e. hand preference indicates superiority of one hemisphere for manual control (skewed 90/10 for humans, but 50/50 for animals)
What is the most lateralised function? Proof?
Language is the most strongly lateralised , with the left hemisphere controlling speech and being better at comprehension
Proof is that brain imaging has it as the most active area when speeching, and a stroke in left hemisphere causes language impairments
What is the dichotic listening task?
Participants given headphones and they hear a different voice in each ear
What were the findings of the dichotic listening task and what does it show about lateralisation of language
Participants are more efficient at understanding language from right ear than left ear –> suggests that language is lateralised in the left hemisphereW
What is aphasia
This is a language disroder that affects people’s ability to communicate or understand –> often impacts speech production, comprheension but not intellectual capabilities
Typical causes are strokes, brain tumors, neurodegenerative diseases etc
There are normally two types; broca’s aphasia and Wernicke’s aphasia
What is Broca’s aphasia
Damage to Broca’s area causes difficutly with speech production, but they can still understand language pretty well
They can understand but cant speak properly
It isn’t a motor problem
Normally patients are aware of the problem
What is Wernicke’s aphasia
Damage to Wernicke’s area causes problems with comprehension of speech. Can produce fluent but meaningless speech.
typically unaware of the problem
What has happened to a split brain patient
Caused by a cut in the corpus callosum. Normally causes a difference in what the left and right hands might do (i.e. one hand reaches for one thing whilst the other reachs for another –> no communication between the sides of the brain)
What did Roger Sperry find with a split brain patient
Found that patient could name an object put in their right hand, but not if the object is in the left hand. This is because the right tactile senses –> left hemisphere which is in charge for communication. But, because right hemisphere couldn’t do speech, the object in left hand couldn’t be vocalised
Thus, they did an experiment, where there was a barrier between two eyes, and displayed a different word on each side (i.e. ‘apple’ and ‘banana’), and then told to tell experimenter what was the left word, but they couldn’t as it went to right hemisphere which can;;t communicate, but the right word went to left hemisphere and could communicate it
However, when patient is shown the objects and has to pick which one was on the right and which on the left, they could do it, because both hemispheres received info but were just limited in their communication of it
WHat can the right hemisphere do
Right can comprehend simple language (not as good as left), but also it contributes more to non-verbal aspects, epecially by adding and interpreting emotional content in speech (e.g. sarcasm), i.e. tone or speech
Where is the hippocampus
It is in the temporal lobe, and is in a seahorse shaped structure
What can damage to hippocampus do
Anterograde amnesia (can remember old things, but can’t learn anything new)
Who was HM
He had brain surgery to treat epilepsy but accidentall removed hippocampus
However, this led to him not be able to learn and remember new information (dense amnesia) (anterograde amnesia)
What did Brenda Milner show about functions of hippocampus from studies on HM
Ultimately concluded that hippocampus was important for creating new neurons not storing memories
The hippocampal amnesia seems to be a deficit specific to declarative learning and memory –> patients like HM show normal procedural learning, but they can’t recall ever learning it (i.e. drawing something from a mirror)
What is Wernicke-Korsakoff’s syndrome? What causes it?
Disorder caused by severe deficiency of vitamin B1 (typically in chronic alcoholics), triggerring wernicke Encephalopathy (confusion, disordered gait and eye movement)
Untreated, WE leads to Korsakoff’s psychosis, which is chracterised by profound anterograde amnesia (inability to form memories) and retrograde amnesia (loss of memories before amnesia), and confabulation (talking about memories which aren’t real)
What neurological changes accompany Alzheimer’s disease
It is a progressive degenerative disease characterised by a loss of newly learned information, followed by loss of distant memories, factual knowledge, and finally procedural skills
It describes widespread neuro-degeneration in brain which typically begins in the temporal lobe
Brain actually shrinks (Sulci and ventricles enlarge)
Could be attributed to abnormal neural tissue present in brain (espeically in cortex and hippocampus) –. senile plaques (beta amyloids) and neuron fibrill tangles (tao protein) –> leads to neuronal death
