More brain structure and vision Flashcards
what is hemispatial neglect
lack of awareness to one side of space
what side is hemispatial neglect commonly on
lack of attention to left, as right hemisphere is damaged
common cause of hemispatial neglect
stroke
typical symptoms of hemispatial neglect
ignoring things on affected side, not using limbs or being unaware of limb existence on affected side
example of hemispatial neglect
drawing clock with all numbers on one side
only eating from right side of plate
what is capgras delusion
belief that a familiar person or pet has been replaced by an imposter
what conditions can capgras delusion occur in
schizophrenia, dementia, traumatic brain injury
what brain hemisphere is most commonly affected by capgras delusion
right hemisphere
what is fregoli delusion
belief that different people are actually one person who can change appearance
what can cause fregoli delusion
traumatic brain injury, L-DOPA treatment for Parkinson’s
which brain area is linked to fregoli delusion
right frontal and left temporoparietal areas, including the fusiform gyrus
what is alien hand syndrome
a condition where hand acts independently without conscious control
what hand is typically affected in patients with alien hand syndrome
usually the left hand
what can cause alien hand syndrome
damage to frontal lobe, corpus callous, or stroke/tumor
what brain disconnect causes alien hand syndrome
disconnection between premotor and primary motor cortex
what is cotard’s syndrome
the belief that one is dead or does not exist
what is cotard’s syndrome often associated with
psychiatric disorders, neurological symptoms, and right or bilateral hemisphere lesions
what was unusual about the man with no brain
he had hydrocephalus as a baby and lived a functional life with a brain mostly filled with CSF
what’s the first thing the thalamus does in vision
it processes the visual input before it reaches the cortex
what role does the occipital lobe play in vision
recognises what is being seen
what does PFC decide in a visual-motor task
whether or not to act based on visual input
how long does a visual motor task take
250ms
what do rods detect
dim light, night vision
what photosensitive protein do rods contain
rhodopsin
where are rods located
the periphery
what do cones detect
bright light and colour
where are cones concentrated
the fovea
what photosensitive protein do cones contain
photopsin
what does M in M cells stand for
magnocellular
what do M cells in the retina do
detect motion and flicker; large receptive fields
what does P in P cells stand for
parvocellular
are m cells large or small
large
are p cells large or small
small
what do p cells do
carry colour information, distinguish between red and green cones
what is the difference between an On-centre cell and an Off-centre cell
ON - fires more when light hits the centre
OFF - fires more when light hits the surround
what is retinotopic mapping
adjacent ganglion cells map to adjacent LGN and V1 cells, forming a spatial map of the visual field
what happens at the optic chiasm
nasal fibres cross, temporal fibres don’t, leading to lateralisation of visual input
if the left optic nerve is cut, what is the result
blindness in the left eye
if the left optic tract is cut, what is the result
loss of vision in right visual field in both eyes (right homonymous hemianopia)
what is the function of the LGN
it acts as a relay station to the primary visual cortex and may filter information
how many layers in the LGN
six layers
what does each layer process
3 from each eye
2 process M cell input (motion)
4 process P cell input (colour/detail)
what is the primary visual cortex specialised in
responds to edges, orientations, motion
is the V1 retinotopic
yes
