MT 4 Senescence and Hallucinations

inability to see two or more objects presented at the same time, although they can be identified individually

simultagnosia= ____________

Balint syndrome

TRIAD

1. simultagnosia

2. oculomotor ataxia egclumsy eye movements)

3. oculomotor apraxia eg.trouble initiating saccades:

TRIAD

1. simultagnosia

2. oculomotor ataxia eg clumsy eye movements

3. oculomotor apraxia eg.trouble initiating saccades

describe Balint Syndrome

bilateral parietal lobe lesions

what causes balint syndrome?

unable to reach and grab things based on visual stimulus. Therefor, accommodation, convergence, binocular and oculomotor skills can be affected -> will have issues with motion perception

describe oculomotor ataxia in Balint syndrome

problems with fixation, saccade initiation and accuracy and pursuits. -> this causes chaotic eye movements

describe Oculomotor Apraxia in Balint syndrome

neurogenerative diseases eg. Alzheimer disease

most common way to get bilateral damage to the parietal lobe causing Balint syndrome?

Balint syndrome: argued that is bilateral hemispatial visual neglect. neglect both sides of view but they can see a single object, and do not neglect a portion of the object which can occur in unilateral neglect

unilateral neglect: damage to right hemisphere parietal lobe

Balint syndrome vs neglect

Balint patients
Alzheimer dementia patients

both have simultagnosia

which patients fail the cookie theft picture?

lost ability to recognize faces including their own, also called face blindness

what is prosopagnosia?

looking at the 2 eyes, nose then mouth

adults seem to all perform the same facial scan paths

damage to the fusiform gyrus near IT or V4, usually bilateral damage occasionally right hemisphere. recent evidence has shown a reduced volume in the inferior longitudinal fasiculus.

what damage in the brain causes prosopagnosia?

fusiform gyrus

V4 is known as the end of the parvo stream where objects and faces are recognized however they are not in the same location. where are faces recognized?

role in biological motion

what is the role of the superior temporal sulcus (STS)?

superior temporal sulcus (STS)

where does biological motion occur?

Emotion recognition and facial memory

inferior longitudinal fasciculus is thought to connect ________

get face blindness (prosopagnosia) as well as emotion blindness

if there is a lesion in the inferior longitudinal fasciculus what can occur?

they are inverted compared to healthy patients easier to match faces when right side up

prosopagnosia patients actually can identify faces easier if __________

inverted images like healthy patients are

patients with prosopagnosia's are not fooled by ___________

started as a joke saying there is a single neuron that is for your grandmother. now it is thought it might a network of cells that are grandmother cells, these are combination of cells for faces we know really well -> these may overlap in facial processing

describe prosopagnosia and grandmother cells

- patients with Asperger syndrome (AS)

- Williams Syndrome (rare genetic disorder have intellectual disability, overly trusting, star like pattern in iris)

who can get prosopagnosia?

congenital, acquired

________ prosopagnosia is relatively common
_________ prosopagnosia is relatively rare

opposite of prosopagnosia, remember ever face they have ever seen

describe super recognizers

a. dark adaptation

b. colour vision

c. contrast sensitivity

d. stereopsis

e. flicker perception

f. motion perception

A shortage of gaba mediated inhibition in the visual cortex might underlie age- related visual deficits including:

showing worsening dark adaptation as we age starting at 60yo.

describe this graph

under 60yo= 10 seconds
at 60yo= becomes 20 seconds
by 90yo= up to 60 seconds

describe dark adaptation as we age

due to photostress recovery time. not necessarily due to poor acuity due to lack of dark adapation because of lack of gaba in brain

major reason elderly people stop driving?

decrease in pupil size with age, known to decrease by 0.5mm every 10 years

what is senile miosis?

20yo = 7mm
70yo= 7*0.5=3.5mm

estimated pupil size at 20yo? 70yo?

narcotics, hallucinogens

what causes extremely small pupils? extremely large pupils?

blue-yellow and red-green can be acquired

after 65yo 10% have colour vision defects

at 90 yo 75% have colour vision defects

issue is lack of gaba causing issues with blobs and inter blobs in cortex

what is the best argument for testing colour vision on all new patients and periodically on established ones?

there is too much noise in the cortex

- either need higher contrast to see it at 20/150 or need larger target eg. 20/300 to see 4 CPD

- contrast threshold now may be with 20/30 instead of 20/20

how does a lack of gaba cause decrease in contrast sensitivity as we age?

3x more contrast to see the same target

someone 3x our age needs __________

at 55yo most people have under 85 local arc seconds stereo

by 66yo down to only 85% have under 85 arc seconds stereo

by 90 only 20% have under 85 arc seconds stereo

this is due to lack of gaba in V2 causing loss in stereo

how does a lack of gaba cause decrease in stereopsis as we age?

20/200 arc seconds stereo

monovision results in __________

use heidelberg edge with flicker defined form but if don't have that run humphrey matrix

how can you test if flicker perception is decreased when aging due to lack of gaba?

intermediate and high spatial frequencies

older adults have reduced CFFs particularly at ______________

have too much neurotransmitters causing you not able to see motion

how can epilepsy cause akinetopsia?

positive spontaneous visual phenomena (PSVP)

hallucination including migraine aura, basically anything that we think is there but is not

hallucination including migraine aura, basically anything that we think is there but is not

visual field loss or AION

describe positive spontaneous visual phenomena (PSVP). what does it not include?

timing is different,

how do hallucinations and real images differ with VEP?

1. Allesthesia

2. Distortions

3. Kinetopsia

4. Palinopsia and polyopia

5. phosphenes and photopsias

6. formed hallucinations

what are the 6 types of positive spontaneous visual phenomena (PSVP)

6 types of positive spontaneous visual phenomena (PSVP)

1. Allesthesia

2. Distortions

3. Kinetopsia

4. Palinopsia and polyopia

5. phosphenes and photopsias

6. formed hallucinations

can be somatosensory, association, visual, auditory

sensory referral eg. a patient touched on the left side feels touch on the right

visual allesthesia: transfer of visual images from one half of visual field to the other. often co- occurs with unilateral neglect so often arises from damage to right parietal lobe

what is Allesthesia?

metamorphopsia
micropsia
macropsia

what are visual distortions (dysmetropsias)?

apparent reduction in size and can lead to teleopsia, the perception that objects are further away

enlargement of objects seen and can lead to pelopsia, perceiving things closer than they are

what is micropsia? what is macropsia?

teleopsia

micropsia can lead to=

pelopsia

macropsia can lead to=

1. Ambien (sleep aid)

2. Seizure disorder eg. epilepsy

3. any viral infection (micro) and viral encephalitis (macro)

what causes micropsia AND macropsia?

1. AMD
2. cerebral infarction (stroke)
3. macular hole
4. migraine HA

what ONLY causes micropsia?

1. celexa (anti-depressant)
2. cocaine use
3. epiretinal membrane and cystoid macular edema
4. hypoglycemia

what ONLY causes macropsia?

kinetopsia

perception of movement when there is none

perception of movement when there is none

what is kinetopsia?

MT/ V5

akinetopsia is caused by lesion in __________

kinetopsia

________ happens with epileptic seizures

excitation of the MT (V5) as well as possibly at the retina

where does kinetopsia occur?

Palinopsia

the recurrent appearance of a visual image after the stimulus has long since disappeared

the recurrent appearance of a visual image after the stimulus has long since disappeared

Palinopsia

cerebral polyopia

seeing the same object multiple times, side by side or in a cirlce

seeing the same object multiple times, side by side or in a circle

describe cerebral polyopia

palinopsia, polyopia

both ________ and _________ can occur together resulting in apparently floating multiple objects

Trazodone an anti-depressant drug

palinopsia and polyopia can be a side effect of ___________

pressure phosphenes, migraine aura

spontaneous phosphenes are NOT __________ eg. ________

structured images, such as geometric figures often recurring in a repetitive pattern

what are photopsias?

trigeminal neuralgia

what causes photopsias?

formed= electrical stimulation of grandmother cells or some such visual association areas

unformed= like phosphenes and photopsias

what are FORMED visual hallucinations? UNFORMED?

1. Dementia

2. Epilepsy and narcolepsy

3. illicit drugs

4. Parkinson disease

5. sleep deprivation

6. psychosis

7. syndromes

what are the 7 causes of FORMED visual hallucinations?

causes of FORMED visual hallucinations

1. Dementia

2. Epilepsy and narcolepsy

3. illicit drugs

4. Parkinson disease

5. sleep deprivation

6. psychosis

7. syndromes

Alzeimer disease

most common type of dementia induced visual hallucinations is due to _______

hypnagogic hallucinations (when falling asleep) and hypnopompic hallucinations (when waking up)

narcolepsy or spontaneous sleeping cause induced hallucinations such as ________ which are seizure induced

1. alcohol
2. cannabis
3. methamphetamine

not just hallucinogen drugs can induce hallucinations ____________ can as well

get intermittent strabismus as well as convergence insufficiency which leads to stereopsis illusions when looking at patterns or flowers

also get audio hallucinations -> women laughing sounds like neighing horse

describe parkinson induced hallucinations

need to replenish neurotransmitters which our brain needs to operate. a lack of sleep can lead to hallucinations and paranoia

why do we sleep?

most scary kind, due to EXCESS neurotransmitter like dopamine or excess blood flow flow to cortex

describe psychotic hallucinations

schizophrenia

example of psychotic hallucinations

higher rates in left-handedness as well as cannabis use before age 30 raises the risk considerably

describe schizophrenia

left superior temporal GYRUS (biological motion occurs in superior temporal sulcus)

the ________ has been suggested to play a key role in auditory and verbal hallucinations in patients with schizophrenia

phantom eye syndrome

for patients with an enucleated eye, visual sensations may still seem to occur in missing eye. probably occur at the terminal end of the optic nerve due to EXCESS neurotransmiter

for patients with an enucleated eye, visual sensations may still seem to occur in missing eye. probably occur at the terminal end of the optic nerve due to EXCESS neurotransmiter

describe phantom eye syndrome

charles bonnet syndrome

syndrome is when visual hallucinations experienced by blind patients

syndrome is when visual hallucinations experienced by blind patients: usually vivid complex visual hallucinations occurring in mentally healthy people

describe charles bonnet syndrome

12-15% of visually impaired patients yet often goes undiagnosed

charles bonnet syndrome affects __________

- have visual impairments due to old age, damage to the eyes or optic pathways
- usually occur during the morning or evening but worse in low lighting

causes of charles bonnet syndrome

retina no longer sends incoming visual sensory impulses back to the brain, but the cortex still sends 80% of the input to the LGN

what is occurring in CBS

- anti-epileptic meds (tegretol)
- blinking rapdily
- vision restoring surgery

treatment of CBS

1. macular diseases
2. retinal diseases
3. optic nerve disease
4. CRAO
5. CRVO

what are 5 things that can cause charles bonnet syndrome?

1. spontaneous nystagmus
2. hallucinations
3. macropsia
4. kinetopsia

ALL caused by depletion in dopamine

parkinsons, sleep induced, and methamphetamine hallucinations

depletion in dopamine can cause __________

- schizophrenia
- phantom eye syndrome
- epilepsy

All take place in right parietal lobe!!

akinetopsia= cannot see motion, destruction in MT/ V5
kinetopsia= can see motion when there is none, excitation of MT/ V5

aura before migraine

zero

what is the numerical value of the expected VEP for a stimulus at the patient's threshold?

visual acuity

what is NOT reduced when we age?

object seems further away
object seems closer

telopsia=
pelopsia=

dementia induced hallucinations and caffeine induced

what hallucinations are due to lack of blood flow?

reduction in dopamine leading to hallucinations, the exact same hallucinations parkinsons can induce

methamphetamine abuse can cause ________ which are _______

80-85yo

at what age will 50% of population fail Ishihara colour vision test?

80yo

at what age will 50% not have 85 arc seconds local stereo?