mod 2 Flashcards
rostral
anterior
caudal
posterior
dorsal
superior
ventral
inferior
lateral
toward the side
medial
toward the midline
ipsilateral
on the same side
contralateral
on the opposite side
longitudinal fissure
separates the two hemispheres
lateral sulcus
separates the temporal lobe from the frontal and parietal
central sulcus
separates the frontal and parietal lobes
temporal lobe gyri
superior, middle and inferior
parietal lobe gyri
postcentral gyrus, superior and inferior parietal lobule
frontal lobe gyri
precentral gyrus, superior/middle/inferior frontal gyrus
what separates the superior parietal lobule from the inferior parietal lobule
intraparietal sulcus
main fibre tract connecting the two cerbra
corpus callosum
large structure attached to dorsal aspect of the brain stem
cerebellum
subcortical structures
thalamus, basal ganglia
brainstem
midbrain - pons - medulla
basal ganglia
caudate nucleus + lentiform nucleus (putamen + globus pallidus)
where are superior and inferior colliculi found
midbrain
make up of ventricular system
consists of interconnected cavities filled with CSF
divisions of ventricular system
2 x lateral, third and fourth
what separates the lateral from the third
interventricular foramen
what separates the third from the fourth
cerebral aqueduct
white matter
axons, myelin
grey matte
cell bodies
10% of brain cells
neurons
90% of brain cells
glial cells
myelin
fatty substance that surrounds and insulates nerve fibres
destruction of myelin causes
multiple sclerosis
fMRI
records changes related to metabolic activity in order to produce a functional view of the brain
how many neurons are thought to be involved in representation of a single image
two hundred million neurons
brain lesion analysis
comparing people with brain lesion in region of interest with people whose region is intact
EEG
records brains electrical activity
ERP
a signature of the electrical activity (recorded by EEG) occurring in brain in response to specific event
ERP considers electrical response for three events
latency, amplitude + polarity, scalp topography
ERP temporal and spatial resolution
spatial not accurate, temporal accurate
structural neuroimaging
CT, MRI, DTI
functional neuroimaging
PET and fMRI
uses x-ray technology to produce a series of brain images enabling the structure of the brain to be viewed
CT
produces brain images with higher resolution than CT
MRI
provides view of white matter tracts using MRI scanner
Diffusion tensor imaging
provides image of concentration/distribution of the radioactive substance
PET
which has greater spatial resolution fMRI or PET
fMRI
records changes related to metabolic activity in successive images in order to produce functional view of brain
fMRI
non-invasive method that causes transient disruption of brain activity by emitting a brief magnetic pulse.
Transcranial magnetic stimulation TMS
TMS excitatory or inhbitory
can be either
a prominent fold of cartilage-supported skin, captures sound and focuses it into the auditory canal
pinna
where does auditory canal end
eardrum
outer ear components
pinna and auditory canal
outer ear
sound waves are captured by pinna and focused into auditory canal
middle ear components
ear drum (tympanic membrane) and ossicles
ossicles
incus, stapes, malleus
high pressure region does what to ear drum
pushes it inward
low pressure region does what to eardrum
pushes it outward
how are vibrations caused within ear
constant low and high pressure pushing eardrum in and out
vibrations travel from eardrum to ossicles to
cochlea
cochlea
spiral shaped fluid filled tube
where are hair cells
cochlea
what converts the sound signal to mechanical vibrations
the ossicles from the vibrations
what converts the mechanical signal to an electrical signal
hair cells
where do hair cells synapse
spiral ganglion cells
tinnitus
person hears noises in absence of any sound stimulus
how is tinnitus caused
by disease processes affecting cochlea or auditory nerve or spontaneous activity
inner ear to CNS
spiral ganglion cells –> vestibular nerve - vestibulocochlear nerve.
vestibulocochlear nerve
carries both balance (vestibular nerve) and hearing (auditory nerve) from cochlea to brain stem
auditory signal synapse where in brainstem
cochlea nuclei located at level of lower pons and upper medulla
auditory information from cochlear nuclei to where?
inferior colliculi to medial geniculate nucleus of thalamus to primary auditory cortex
auditory pathway in brain
cochlear nuclei - inferior colliculi - medial geniculate nucleus - primary auditory cortex
where is primary auditory cortex located
superior temporal lobe
hechls gyri
primary auditory cortex
tonotopic organisation
in primary auditory cortex
interaural time
difference in arrival time of sound at the ear
where is sound localisation not good
vertical plane
what produces the reflections of entering sound
bumps and ridges on outer ear
sound waves are captured by the pinna and focused into the auditory canal
external ear
sound waves strike the ear drum and the vibrations pass through the ossicles to the cochlea
middle ear
hair cells within the cochlea transduce the vibrations into a neural signal, which is sent to spiral ganglion cells, whose axons form the cochlear nerve which carries info to brain stem via vestibulocochlear nerve
inner ear
where is medial geniculate nucleus found
thalamus
the opening that allows light to enter the eye and reach the retina
pupil
a circular muscle that controls the size of the pupil
iris
the transparent surface that covers the pupil and iris
cornea
the white of the eye, continuous with cornea
sclera
helps focus ray of light on the retina
lens
the internal lining of the rear two-thirds of the eye; converts images into electrical impulses, which are sent to the brain
retina
the central area of the retina that is specialised for the central vision
macula
marks the centre of the retina and the centre of the macula
fovea
visual image is the least distorted
fovea
made up of the axons of retinal ganglion cells, carries impulses for vision from the retina toward the brain
optic nerve
wavelength of electromagnetic energy that is visible to the naked human eye
400-700nm
flow of information within the retina
photoreceptors -> bipolar cells -> ganglion cells
photoreceptors
rods and cones
displacement of bipolar and ganglion cells
laterally to allow light to strike foveal photoreceptors directly
rods
scotopic, poor acuity achromatic vision in low light
photopigment in rods
all the same
periphery heavy in rods or cones
rods
cones
photopic, high acuity colour vision
central retina / fovea heavier in cones or rods
cones
photopigment of cones
different cones sensitive to different wavelengths of light
blindspot
where the axons of retinal ganglion cells exit retina, there are no photoreceptors
total amount of space that can be viewed by retina
visual field
half the retina that is closer to the nose
nasal hemiretina
other half of the retina (not close to the nose)
temporal hemiretina
blindspot location
15 degrees eccentric in your temporal hemifield
where is optic disc located in retina
nasal hemiretina
axons in which hemi-retina cross the midline
ganglion cells in the nasal hemi-retina
when visual stimuli in the right hemifield
cells in both retinas project axons into left optic tract
if left optic nerve is cut
vision in left eye will be lost completely
if optic chiasm is transected
peripheral vision will be lost bilaterally
if left optic tract is cut
vision fo right hemifield will be lost bilaterally
axons of ganglion cells pre optic chiasm
optic nerves
axons of cells post optic chiam
optic tract
axons of optic tract project to
superior colliculus and lateral geniculate nucleus in thalamus
subcortical vision
retinotectal pathway
retinotectal pathway
retina, superior colliculus
cortical vision
retinogeniculostriate pathway
retinogeniculostriate pathway
retina, thalamus (LGN), primary visual cortex
superior colliculus in non-mammalian vertebrates
optic tectum
% of ganglion cells in retina that project to superior colliculus
10%
% of ganglion cells that project to the lateral geniculate nucleus
90
what does the right lateral geniculate nucleus receive information about
the left half of the visual field
what does the left LGN receive information about
the right half of the visual field
primary visual cortex location
medial part of occipital lobe buried within the calcarine fissure
visual pathway from primary visual cortex
to striate cortex -> V1 -> broadmanns area 17
what happens when TMS is placed over the occipital cortex
TMS can elicit light sensations (phosphenes) in absence of any visual stimuli
increase in the phosphene threshold reflects..
reduced visual cortex excitability
reduction in phosphene threshold reflects
increased visual cortex excitability
correlation of ecstasy use and phosphene threshold
negatively correlated
phosphene levels in mdma users and control
ecstasy group had lower threshold than control, those who hallucinated within ecstasy group was even lower
where does sensory integration occur
heteromodal regions of cortex
superior colliculus visual or auditory
both! but think visual
what does ventriloquist illusion provide
an example of how visual and auditory information are integrated
how does the ventriloquist illusion occur
sound source being mislocalized towards a synchronous but spatially discrepant visual event. e.g. puppets mouth moving
spontaneous activity can lead to perceived sensation e.g.
hallucinations and tinnitus
maunsell and van essen
single cell recording in macaque monkeys
results from maunsell and van essen
neurons in area MT are selective for the direction and speed of motion
what was subtracted during the PET activation during visual stimulation to identify colour
activity elicited by the abstract scene shown in colour - activity elicited by abstract scene shown in greyscale
what was subtracted during PET activation during visual stimulation to identify motor perception
activity elicited when moving - activity elicited when stationary
two projection routes from primary visual cortex (V1) to extrastriate visual cortex
dorsal and ventral stream
stream that codes motion and location
dorsal
stream processes detailed stimulus features and object identity
ventral stream
what does each visual areas topographical represent
contralateral hemifield
what marks the boundaries between anatomically adjacent visual areas
topographic discontinuities
V4
respond to combinations of colour and form
what extrastriate cortex is ventral stream associated with
V4
V5
selective for direction and speed of motion
extrastriate cortex that the dorsal stream is associated with
V5
where are the neurons that receive information from the retinal ganglion cells located within the superior colliculi
superficial layers
superior colliculus experiment
monkey press bar to turn on light, monkey fixated on ligh which projected another stimulus onto the screen in order to determine receptive field of study
when do the monkeys receive a drop of water during the superior colliculus experiment
when they press the bar while the light was dim
conclusions about the superior colliculus (3)
superficial layers contain retinotopic maps of visual field
left superior colliculus represents the right hemifield
map is distorted with more neurons devoted to analysis of central portion of the visual field
sprague effect
visual orienting responses can be restored in the cortically blind hemifield by removing the contralesional superior colliculus
experiment visual cortex vs. superior colliculus damage
looks at effect of disrupting cortical vs subcortical vision using localization and discrimination tasks and making lesions of bilateral removal of visual cortex or transection of input fibres to both superior colliculi
localisation task
turn head toward a sunflower seed held in experimenters hand
discrimination task
run down a two-arm maze and enter the door behind which a sunflower seed was hidden
how did those with lesions in visual cortex perform
performed normal in localization task but showed impaired performance in the discrimination
how did those with altered superior colliculi perform
performed normal in discrimination but in localisation, made no attempt to orient towards the seed
when in humans can the contribution of subcortical pathways be assessed in absence of cortical pathways
after a stroke involving the primary visual cortex
cortical blindness
damage of V1
perimetry test
present a small spot of light at random locations across the visual field while patient fixates on a central stimulus
what happens when light falls outside the scotoma during a perimetry test
detection is immediate
what happens when light falls within the scotoma during a perimetry test
fail to detect the light however rods and cons are still transmitting information to the lateral geniculate nucleus
weiskrantz
residual vision without primary visual cortex - tone sounds, move your eyes to location of light
what is the dependent variable of weiskrantz test of residual vision without PVC
eye position and how far they moved after tone sounded
in rafal findings what was the latency with which his eyes moved towards the light that appeared in the intact hemifield?
slower when the distractor appeared in the cortically blind hemifield than when no distractor appeared, despite not being able to see
effect of unilateral damage to primary auditory cortex
minro due to auditory information being transmitted ipsilaterally and contralaterally.
movement fields -where found/what are they
neurons in deep layers of SC have movement field. movement fields are large and fire most intensely before saccades in one optimal direction
where are the smallest saccades represented in the SC?
in the rostral SC
where are the largest saccades represented in the SC
in the caudal SC
when do neurons in deep layer increase their discharge rate
before an eye movement
what proved visuomotor abilities within the SC
the fact that the cell still responded to the light on the receptive field even though no movement occurred
SC superficial layers
recieve info from retinal ganglion cells and contain a retinotopic map
SC deep layers
have either visuomotor or pure motor capabilities and contain a motor map
exogenous saccades =
reflexive saccades
what is the activity of fixation cells in the SC modulated by
an external visual stimulus at fixation
whats activated when a when a stimulus is present at fixation
cells in the rostral portion of the superior colliculus
what structure is important for the fixation reflex
SC
fixation offset effect paradigm
fixate on central dot, look at star in periphery when it appears
fixation offset condition in effect paradigm
fixation stimulus disappears when target appears
fixation overlap condition
fixation stimulus remains present when target appears
fixation offset effect paradigm independent variables
fixation overlap condition and fixation offset condition
what does fixation offset paradigm conclude
strong fixation reflex with a large FOE and weak for a small one
endogenous eye movements
voluntary eye movements
experiment: effects of TMS over cortex on saccadic eye movements, endogenous task
move eyes to left or right in response to a central arrowhead
experiment: effects of TMS over cortex on saccadic eye movements, exogenous task
move your eyes to a peripheral asterisk
did TMS have an effect over the superior prefrontal cortex or the superior parietal lobule of endogenous saccade task
the superior prefrontal cortex, endogenous saccades to contralateral hemifield were delayed
did TMS have an effect over the superior prefrontal cortex or the superior parietal lobule of endogenous saccade task
neither were affected
what was the theorised conclusion for disruptions of superior prefrontal cortex in endogenous movements
normal operation of the frontal eye field was disrupted
henik: effects of a lesion involving the frontal eye field on voluntary saccades task
move eyes to left or right in response to a central arrowhead
heniks conclusion
the delay in contralateral endogenous saccades associated with damage to the FEF indicate that the FEF is normally involved in generating voluntary saccades
reflexive eye movements are associated with which structure
the subcortical
voluntary eye movements are associated with which structure
the cortical
what is the frontal eye field important for
generating voluntary eye movements
anti-saccade task
fixate on centre, when stimulus appears in the periphery, move your eyes in the opposite direction then return eyes to centre
what does the anti-saccade task require
inhibition of a reflexive saccade, followed by execution of a voluntary saccade
who had most errors in anti-saccade test
children 5-8
machado et al: effects of a lesion involving the frontal eye field on anti-saccades supported what hypothesis
that the FEF normally imposes inhibitory control over the ipsilesional oculomotor circuitry that generates reflex saccades
subcortical cells in oculomotor system
mediate more primitive reflex oculomotor responses
phylogenetically newer cortical cells in oculomotor system
impose control over primitive reflexes via projections to subcortical cells, facilitating when advantageous and inhibiting when disadvantageous
what behaviour re-emerges in older adults due to ageing degenerative processes
uncontrolled reflexive behaviour due to disrupted strategic visual orienting
higher proportion of cortical or subcortical neurons?
humans higher cortical but frogs higher subcortical
overt attention
attention involved with movement of eyes
covert attention
attention in absence of eye movement
findings of the experiment looking at covert attention in occipital lobe
stronger neural signal occurred in response to the stimulus when attention was directed at the location of the stimulus
attention elicited by an external stimulus
exogenous shift - reflexive - superior colliculus
attention elicited by an internal stimulus
endogenous shift - voluntarily - cortical
faciliation
latency to respond to target is reduced when target appears at location of attention compared to different location.
what does inhibition of return provide an example of
a reflexive mechanism of attention
inhibition of return
when attention is directed toward a location, then there is a long delay before a target appears, latency to respond to target increases when target appears at attended location compared to different location
is latency decreased when target appears at same location in inhibition of return or facilitation
facilitation
flanker tast purpose
used to assess the efficacy of strategic control over attention (how easily distractible someone is)
flanker effect
reaction times on incongruent trials - reaction times on congruent trials
flanker task
when stimulus appears at centre indicate identity by pressing appropriate button as quickly as you can
3 steps of brain development
- cell division, 2. cell migration, 3. cell differentiation
plasticity
refers to the neurons system ability to change. decreases with age, adults brain more rigid
formation of ocular dominance columns in primary visual cortex
at birth inputs from LGN of the two eyes intermingle with striate cortex V1. inputs from two eyes over development segregate into these columns.
ferret study: rewiring brain in newborns what is it testing
plasticity in terms of visual and auditory systems
ferret study: rewiring brain in newborns what was removed
the superior and inferior colliculus - so axons of retinal ganglion cells intended for SC went to MGN
ferret study: rewiring brain in newborns findings
by adults, neurons in auditory cortex behaved like visual neurons responding to visual stimuli
effects of stimulating visual cortex in adults with impaired vision
self-reported phosphenes elicited by TMS over visual cortex
experiment: effects of stimulating visual cortex in adults with impaired vision findings
those with some residual vision = 100%
those with poor residual vision = 60%
those with no residual vision = 20%
experiment = mental imagery in sighted and congenitally blind adults task
produce mental images from animal names versus passive listening to abstract words
what was used to measure mental imagery in sighted and congenitally blind adults and how
fMRI (brain activity during mental imagery task - brain activity during passive listening to abstract words
results from mental imagery experiment
production of mental images were associated with activation of visual cortex for blind people too implying they were imagining things just maybe not the same thing as we would, seeing as they would have never visually seen one
training and plasticity A1
training monkeys to discriminate different tone frequencies
what did trained frequencies lead to
enlarged cortical regions and functional plasticity within A1
training and plasticity M1
finger to thumb tapping sequences
what and how was measured in M1 for training and plasticity
fMRI used to measure activity related changes in blood flow in primary motor cortex. (left practised movements - right untrained sequential movements)
results for M1 training and plasticity
3 weeks + 8 weeks = greater changes in blood flow in contralateral motor cortex for trained (left) compared to untrained (right)
age can decline memory function which can be seen by a reduced
hippocampus
what can increase size of hippocampus
exercise
