Brain Mapping (Week 3) Flashcards
receptive field
part of sensory world which a neuron responds to
big receptor field pros and cons
pros: covers larger area (no position variance problem)
cons: non specific
small receptor fields pros and cons
pros: differentiates between specific information
cons: only covers small area, position variance
position variance
being able to identify an object anywhere in space
somatosensory receptive fields
areas of bodies surface that respond to sensory stimuli
where are the smallest somatosensory RF
fingertips
where are the largest somatosensory RF
thigh/calf
what dictates where on the body there are small vs large RF
sensitivity of that area (ex. lots of dexterity needed in fingers -> higher sensitivity -> smaller more specific RF)
visual receptor field
area of visual space that processes visual stimuli
degrees of visual angle
measurement for visual receptive field; how large an object appears to be in your field of view.
olfactory receptive field
mapped along dimension of # of carbons in a chain or size of molecules (small scale)
numerical receptive fields
mapped along dimension of numerosity (respond to magnitude of things)
where are numerical receptive fields often found
parietal and prefrontal neurons
how does brain optimize receptive fields
many smaller adjacent RF send action potentials all to one larger RF
- communicate to each other via feedforward and feedback pathways
topographic map
orderly representation of sensory space in the brain
how are neurons arranged in topographic maps of the brain
disproportionately representative of world which allows greater sensitivity to parts that occupy more space
(ex. Fovea- part of the retina with high spatial resolution)
what places in the brain have the most neurons
high sensitivity places
Retinotopic Map
orderly representation of visual space/ hemifield; shows how light maps onto the back of the eye
what part of the brain shows complete representation of visual hemifield
V1 (primary visual cortex)
what happens to the complete representation of the hemifield as you move forward in the brain
more localized specialization
tonotopic map
ordly representation of sound/tone frequency; respond to different frequency sound waves
somatotopic map
ordlery representation of body surface for specific area of the brain
fine-grained maps
large number of neurons; small receptive fields
coarse grained maps
small number of neurons; large receptive fields
how does the brain group neurons effiecently
neurons processing nearby sensory space group together bc they interact more often and that reduces wiring
reference frame
a coordinate system used to represent the position of an object
how do you specify a position in a reference frame
with regards to the position of a reference point
2 classes of reference frames
egocentric and allocentric reference frames
subclasses of egocentric reference frames
- eye centered/ retinoscopic: eye is origin of coordinate system
- head centered: head is origin of coordinate system
-body centered: body or part of body is origin of coordinate system (ex. motor system)
subclasses of allocentric reference frames
-object centered
- world centered (street map)
how can you test what reference field a neuron has
move stimulus and see how the receptive field moves
what type of reference frame does the hippocampus have
allocentric
what type of reference frame does the parietal cortex have
egocentric
how is information transformed between allocentric and egocentric between hippocampus and parial lobes
PCC (posterior cingulate cortex) and RSC (retrosplenial cortex) which is a brain hub
how does the RSC help with allocentric-egocentric transformations
has both allocentric cells and egocentric cells- consistent with the role in spatial transformations
head direction cells
cells that respond to our directional heading in the horizontal plane (which way we are facing): needed for allosteric/ egocentric transformation
how do signals from head direction cells work
certain neurons fire when head is facing a certain angle/ direct but not at other times
why is there a connection between hippocampus and parietal cortex
transforms between egocentric and allocentric during navigation; connects self to our surroundings/ place yourself in your allosteric view of the setting
what pathway do sensory motor transformations go along
“How” pathway at the top of the brain; how to use an object and where it is
what helps transform egocentric information from the occipital love to egocentric information in the primary motor cortex
parietal lobe
process of transmitting info from sight/ other senses to motor cortex
sensorimotor transformation
sensorimotor transformation steps
1) receive info about location of visual target in eye centered coordinates
2)target location remapped into joint coordinates so you can move arm to corresponding location
* 1 or more transformation steps
mathematical way brain finds hand centered position of the target
subtract eye centered hand position from eye centered target position
what i the PPC function in tranformation
translator for different reference frames across brain
2 main important transformations
eye centered - body centered (both egocentric)
egocentric - allocentric
