NEUR1020 Module 4

what did HM help us find

that memory is not one thing but different components mediated by diff parts of the brain

how is FTD diagnosed

Neuropsychology assessment: measure cognition

• Assess areas incl attention, executive functions, language

• Form cognitive profile to look for pattern and see which type

  • Executive functions crucial in this bit

what do they look for when diagnosing FTD

stopping/starting behaviour

• Can be tested by saying a sentence with last word left off

  • Does PT finish sentence meaningfully (initiation)

• Ask PT to complete sentence with word that doesn't make sense

  • Does PT not say automatic response (inhibition)

  • Does PT respond with a meaningless response (strategy)

• Ppl with behavioural variant struggle with inhibition and strategy

semantic variant (affected area)

temporal lobes (left and right). Most atrophy on anterior (pole) of temporal lobe

history of frontal leucotomy (lobotomy)

egas moniz introduced prefrontal leucotomy for relief of psychiatric disorders

first performed in 1935

based on effects observed in chimpanzees following frontal lobe lesions (they became ‘calmer’)

used mainly for severe psychosis for which there was not a whole bunch of treatment

stopped after antipsychotics were introduced in 1950s

who was walter freeman

introduced transorbital lobotomy in 1946 which was done by going through the eye socket and could be done ‘by the bedside’

what are the language variants of FTD

non-fluent primary progressive aphasia:

Logopenic progressive aphasia:

semantic dementia:  

semantic dementia

speech sounds fluent and articulate but content is empty and doesn't necessarily convey meaning

Lack of knowledge abt world

logopenic progressive aphasia

words come out properly w grammar and stuff but it is effortful and often with long pauses

has comprehension and understanding of world

non-fluent primary progressive aphasia

speech is effortful and hard to get out, somewhat telegraphic

has comprehension and understanding of world

what is one of the things the frontal lobe is responsible for

executive functioning

-reasoning, planning problem-solving

-inhibitory control

-WM

hemispheres…

• can function independently

• left can tell what it has seen but right can only show (through left hand)

what is ‘split brain’

severed corpus callosum.

was done as a last resort surgical treatment for v severe epilepsy to stop spread of seizure activity

studied by Sperry and Gazzangia in 1960s

led to lots of knowledge abt lateralisation

what is interhemispheric communication

whether or not the information needs to cross hemispheres to achieve the goal.

e.g. if ur asked to say what you see on the left side of visual space, the info needs to go from your right hemishere (contralateral) to left hemisphere (speech production)

but if ur just asked to point, then info doesn’t need to cross bc right hemisphere is responsible for movement and vision

relationship between language and hand dominance

no overall ‘dominant hemisphere’ but;

95% of right-handed people have language in left hemisphere and;

70% of left-handed people have language in left hemisphere

population who is left handed

10%

where is the most common area for onset of seizure activity (epilepsy)

medial parts of temporal lobe around hippocampus

what is epilepsy

involves abnormal discharges in electrical activity of brain. Can affect the whole brain or certain areas

why is controlling seizures important

bc seizures can cause neuron loss so its to make sure that seizure activity doesnt damage hippocampus

what are the two types of seizures

generalised seizures- affect whole brain and usual present as convulsions

specific symptoms- when only specific parts of brain are affected. manifests w/ specific symptoms e.g. absent seizures, hallucinations

why do seizures originate in temporal lobe

bc epilepsy piggbyacks on mechanisms which allow memory to occur and memory is encoded in the temporal lobe.

what increases seizure frequency

 If region of brain abnorrmally fires in this region, these connections can be strengthened and occur more frequently.

physiological changes that can occur as a result of seizures

• Appearance of glutamate- neurotransmitter in region

• Cellular depolarisation

• Loss of neurons in region

• Hippocampus will shrivel up through neuron loss (atrophied)

main neuropsychological effect of seizures

memory deficits

main treatments for epilepsy

• medication- first and most common avenue

• surgical options- operating on brain and removing the bit of the brain producing seizures

what are some risks if the seizure-producing area is near medial temporal lobe

memory dysfunction, amnesia etc

what do neuropsychologists do to assess risk level of surgical options for epilepsy

test verbal memory (thought to be related to left temporal region) and visual memory (right temporal region) to identify potential memory dysfunction. If deficit is present then more risky bc the other hippocampus has to compensate (cognitive reserve). If BOTH display deficit this means hippocampus is damaged and very risky

what is the wada test and why is it used

To determine risk of cognitive dysfunction after surgery: Anesthetise one hemispheren and retest cog function. If person's left hemisphere is anesthetised and they lose ability to speak, we know that broca's area is in left hemisphere. If complete loss of memory function (under anesthesia) then no surgery

what do neuropsychologists do to help patients with epilepsy

• Ensure seizures are limited (appropriate meds)

• Identifying potential deficits

• Aid in surgery

  • if deficits are created as a result, then giving tools to deal with that e.g. neurorehabilitation, coping etc

• Offer options for rehab

what are the 2 types of long-term memory

declarative and procedural

what is declarative memory

conscious recollection (things u can declare). comprised of episodic and semantic memory

what is episodic memory

memory of past events ‘episodes’. things youve seen and done e.g. what u did for ur bday

what is semantic memory

facts and basic knowledge u can recall. e.g. paris is capital of france

Laterised functions

Some brains functions rely more on one side of the brain that the other

what is working memory

keeping things in ur immediate awareness while u solve a problem

HM could still mentally rehearse to remember things for a few seconds

where is the hippocampus located

medial temporal lobe

Left Hemisphere

Used for language/speech. (most ppls brocas area is here)

Right Hemisphere

Uses for tone of voice/prosody, face perception, perceptual grouping. basically being able to put individual items together to make a pattern

Crossed (Contralateral) functions

Movement, sensation and vision.

Left hemisphere is responsive for processing and executing right body movement, sensation vision.

Also vice versa with right hemisphere and left body

Contralateral

Opposite side of the body

Ipsilatral

Same side of the body

Vision

Each side of the visuals space is mapped to a contralateral visual cortex

input to each retina is split in half which allows the left visual space from BOTH left and right eyes to be mapped to the right hemisphere

Corpus Callosum

Connect left/right hemispheres

the axons of neurons crossing to opposite hemisphere

allows transfer of info between two hemispheres

Split Brain Experiment

If picture flashed on left side and broca's area is in left hemisphere, pt will report seeing nothing. This happens because left hemisphere is responsible for speech production and doesn't have access to info from right hemisphere (which is where the picture went). So the left hemisphere received no information and communicated seeing nothing. Whatever right hemisphere info was consumed can't be reported on bc there is no/limited speech production in this area

Hippocampus

Plays a crucial role in memory, particularly in forming new episodic memories. damage causes memory loss. memories are not stored here.

Place Cells

Gives us our ability for spatial navigation

Short-Term Memory

Limited-capacity memory which lasts for a few seconds e.g. remembering phone number long enough to put it in phone

Long-Term memory (declarative)

Has relations to conscious recollection

Episodic Memories

Memories of past events or "episodes." Things you've seen and done

Procedural

Not for conscious recall (skills you've learnt)

Encoding

Laying down new memories for long-term storage and maintaining memories

Retrieval

Retrieving memories for conscious recall

Bottom up-Processes

Driven by external stimuli or unconscious states

Top-Down Processes

Cognitive control or volitional control; modulation by prior knowledge and experiences

Parietal Lobe (Attention)

Directs attention (eye-movements) to explore visual worlds

Spatial Awareness

Represent spatial location of objects around us for guiding actions

Spatial Neglect

Having a deficit in attention to one side of space

Selectivity

Select and prioritse stimuli based on location or feature

Brain capacity is limited. As such...

We use attention to filter and prioritise sensory information

"Conscious" Controlled (Top-Down)

Selecting/prioritising according to task or goal

"Automatic" attention (Bottom-Up)

Attention captured involuntarily by highly salient stimuli

Simultagnosia

Inability to perceive more than one object at a time

Disorders associated with impaired inhibitory control

ADHD, OCD, reward addiction

Fronto-Temporal Dementia (FTD)

Degeneration (loss of neuron) in frontal/temporal lobe.

2nd most common dementia (after Alzheimers)

Symptoms of Fronto-Temporal Dementia (FTD)

Disinhibition (more inappropriate actions), apathy, loss of empathy, deficit in executive functions (using neuropsychological testing), speech and motor language deficit

Behavioural Variant (Fronto-Temporal Dementia)

Problems with behaving properly in the world

Behavioural Variant (Affected Area)

Left/Right brain (frontal atrophy)

Non Fluent Frontotemporal Dementia (Affected Area)

posterior Left Frontal Lobe

Logopenic Progressive Aphasia (Affected Area)

left hemisphere. more frontal-parietal ito temporal

Posterior (cortical region)

who was patient HM

some guy who underwent surgery for epilepsy and had both hippocampi removed in 1953

what happened to HM

he could never form new memories and had no recollection of anything that happened since the day of the surgery