spacial navigation
How do we find our way in an environment?
Navigation Research Framework
Microscopic Analysis: - How do you keep track of your own location and object locations as you move? ○ Small-scale space ○ Short time scale ○ Perception
Macroscopic analysis
- How do you remember where things are?
- How do you use that memory to guide navigation?
○ Large-scale memory
○ Long time scale
○ Learning and memory
navigational research methods
- In addition to psychology and neuroscience, many other disciplines contribute to navigation research including biology, geography, robotics etc.
Brain regions and location tracking
medio-temporal lobe.
Neural Mechanisms of Location tracking:
- Place cells in the hippocampus fire when you are in specific locations within a given environment.
- Grid cells in the entorhinal cortex fire when you occupy one of the hexagonal grid points within a given environment.
- Many other types of cells have been discovered.
○ Head direction cells
○ Spatial view cells
○ Boundary cells
○ Time cells
○ Speed cells
○ Travel axis cells - These cells, together with place and grid cells, constitute the neural basis of spatial navigation.
- Most of the data on these cells come from animal studies.
location tracking in the human brain
arly evidence suggests that these basic systems of location tracking are shared across species.
- Between species differences are present in the way these core systems are fed with inputs, however
○ For example, humans rely heavily on vision to generate these inputs, but bats primarily use their hearing.
○ Another examples: many species can use the magnetic field of the earth for navigation but humans cant.
spatial updating behaviour
- How do we come to achieve such excellent performance?
- What type of information is most relevant?
○ Actual experience in walking/moving.
○ Mental imagery and top-down control.
○ Observing others walking/moving.
- What type of information is most relevant?
Klatzky’s experiment
Klatzky’s (1998) experiment:
- Actual walking
- Simulated walking (no body movement)
- Simulated walking with physical turning
- Watched someone walking
- Listening to the description of the path.
75% of participants (18 out of 24) were able to find their location in this experiment
participants walked the first and second leg of the journey. in one condition, participants actually physically walked and in the second it was simulated.
spatial behaviour
- For updating your location as you move, bodybased information is useful
- When the body-based information is generated from actively controlled movement, the information is even more effective
- Are these behavioral observations relevant to the neural mechanisms in the MTL?
- Epilepsy patients who surgically removed their MTL (typically only in one hemisphere) tend to walk farther than controls
miscroscopic analysis
- Neurons in the MTL play an important role in keeping track of your location as you move
- There are many different types of neurons, each of which is tuned to a different aspect of location information
- Spatial updating behaviour observed in humans shows characteristics that can be explained by the MTL neurons’ properties
large scale navigation
Ishikawa et al.’s (2008) study
– Participants learned the layout of a residential neighbourhood by walking prescribed paths in three different ways:
- Finding the paths by reading a paper map
- Using a GPS navigation device (just like a map app on your smartphone)
- Being guided along the paths first, and subsequently following remembered paths by themselves – GPS users performed less well
- They walked longer distance and made more stops
- Their memory for the neighbourhood layout was less accurate
GPS is helpful when navigation is challenging, but it does not always offer best navigation experiences.
2 systems of large scale navigation
Place learning
– Identify object locations within a larger environmental framework
– Rapidly acquired, allows flexible behaviour (e.g., short-cut), but requires conscious retrieval and susceptible to forgetting
– Declarative memory based, MTL-dependent system
Response learning
– Perform a specific sequence of action
– Slow to learn, only rigid behaviour is possible, but does not require conscious awareness and much longer-lasting
– Procedural memory based, caudate-dependent system.
memory for geographical information
- Geographical information is represented in a hierarchical structure
- Judgments about spatial relations are biased by higher-order information (e.g., which state a city belongs to)
- Distance estimates are often asymmetrical
summary of macroscopic analysis
- Large-scale navigation ability is still crucial for our wellbeing, even though navigation aids such as GPS are now becoming commonplace
- There are two systems of navigation in the brain
– Place learning for flexible but cognitively demanding navigation
– Response learning for rigid but effective navigation - Memory for geographical information tends to be biased in a variety of ways
– It is not like a real map at all
– These biases affect how people navigate by using their memories for places and locations
- There are two systems of navigation in the brain
regions of the MTL
- hippocampus
- parahippocampal cortex.
- entorhinal cortex.
- peririhinal cortex.
These regions contain neurons that are essential for navigation.
place neurons
fire an action potential when you are in a specific location within an area.
When we move, the original place neurons will stop firing and others will begin to fire.
This carries on as we move and various place neurons begin to fire and stop firing.
research on place cells
typically done on animals.
Elkstrom conceptualised a taxi driver game which saw the participant pick up a passenger and drive them where they needed to go. these patients had electrodes implanted in their brains.
the colours responded to how much the neurons fired. found that place cells fire in response to our location.
place cell location
- majority are found in the hippocampus.
grid cells
- also fire according to your location in place.
- however, grid cells can have multiple firing spots in location.
- thus, when we move location, some of the original grid cells continue firing.
- these cells are capable of tracking the direction of your travel.
other types of cells
- head direction cells (which way your head is pointing).
- spatial view cells (gaze direction).
- boundary cells
- time cells (also in the hippocampus, they fire according to a point in time).
- speed cells
- travel axis cells (encodes the main direction of travel).
location tracking between species
the basic systems of location tracking are consistent across species.
animals have a great sense of the magnetic field. for example, when animals migrate.
Yamamoto & Philbeck
compared the time participants took to imagine walking somewhere and when physcically walking.
Yamamoto (2016)
consistently disoriented blindfolded participants. then let them walk freely within the environment, not touching the walls etc.
found that around 70% of participants were able to find their location in the space without any external stimuli.
epilepsy patients and removal of MTL
lost a lot of place and grid cells and therefore performed location tasks worse than others, they also tend to walk further than others.
