spatial navigation Flashcards
cognitive maps
tolman: proposed the idea of a cognitive map in the 1940’s
rats: rapidly switch to alternative path if previous path is blocked
- implied that animals must have spatial knowledge about environment
spatial knowledge:
- like that on a map
grid cells, head direction cells and border cells complete a cognitive map
- grid cells fire in a regular hexagonal lattice of locations tiling the floor of the environment
- head direction cell fire on the basis of the direction the head is facing
- border cells fire when the animal is at set distances from navigational boundaries facing in specific direction.
If the rodent spatial positioning network a good model of human navigation
- similiar anatomical structures; hippocampal formation, papez circuit
but there are differences across species; - damage to human equivalent navigation areas causes memory broader memory deficits
difficulty translating to humannavigation studies
- navigation is an inherently mobile task, participants in fmri experiments must remain stationary in the scanner
- memory and planning systems are engages and visual inputs are often present
scene perception in the brain
- Epsten and K provided evidence for a region in the visual cortex that preferentially processes scenes
- anatomically, PPA lies along the parahippocampal gyrus and collateral sulcus.
the PPA responds to scenes, but not faces or other objects
- scenes include a wide variety of images
- ppa is sensitive to a global spatial geometry/ configuration of scenes.
the PPA responds less to scrambles scenes
- PPA’s response is highest to scenes that depict a realist spatial layout
- PPA’s response is lower if the position of the objects in the scene are scrambled
Is the PpA responsible for the spatial representation of scenes?
- spatial layout hypothesis: the PPA encodes the global spatial layout of a scene
- the lateral occipital complex (LOC) and fusiform gyrus encode information about the local individual objects in the scene
- consists with consequences of damage to the PPA
- the overall organisation of the scene is lost.
distance coding from fMRI adaptation
- 220 color photographs of 10 prominent landmarks from the uni of pen
- ‘subjective’ distances between landmarks were determined for each participants
- Task: subjects identified each landmarks and made a button press once they had done.
fMRI in hippocampus like border cells
- fMRI activity in the in the hippocampus scales with the distance between that building and the building shown on the immediately preceeding trial
recording from individual cells in human medial temporal and frontal lobes
- presurgical epilepsy paients: each patient had 6 to 14 depth electrodes implanted.
recording from place cells in human hippocampus
- evidence for a neural code of human spatial navigation based on cells that respond.
- place-responsive cells were clustered in the huppocampus and compared with amygdala, parahippocampal region and frontal lobes
viewpoint-independent direction coding in humans
- previous human studies had found evidence from place-like and grid-like representations but not exclusively to percieved heading
- used fMRI adaptation to distinctive landmarks with one of four facing directions
- participants had to indicated whether the position represented by the static image of the landmark was on the left or the right of the centre point of the maze
- paired images were in the same heading direction or head different headings
representation of allocentric heading in the retrosplenial complex
- single brain region in the medial pariatal cortex was modulated by learned heading.
- the representation of allocentric heading acheieved in the RSC
using cognitive maps to navigate: fMRI results
- subject learned an unfamiliar layout of the city, fMRI shows hippocampal activity correlates with path distances
- subjects watched 10 movies of layout, and data showed hippocampal activity
