A navigational model of spatial reference frames based on neurological and behavioral findings in human and rodents
Timo Oess April 2016
Introduction
Spatial orientation and navigation in environments requires the agent to:
relate the perceptual information to previously stored memory of the same environment
retrieve stored spatial memory and transform it, such that it is useful in the current context
combine the various sensory information to infer its current position and plan a path through space
Involved Brain Regions
What are reference frames?
Reference frames provide a means of representing the locations of entities in space
They describe the orientation and distance from one entity to another and to a fixed reference point in space
These refernce points can change. Transformation between different frames needs to be possible.
➡ A reference frame provides a framework in which entities can be represented
Spatial Navigation (realised in our model)
Source: www.playbuzz.com
Model Architecture
Hippocampus
Retrosplenial Cortex
Posterior Parietal Cortex
Neuron Example
Simulation Experiments
Source: www.playbuzz.com
Random Light Experiment (Wilber et. al 2014)
- Setup
Random Light Experiment (Wilber et. al 2014)
- Results
Random Light Experiment (Wilber et. al 2014)
- Results
Starmaze Experiment (Igloi et. al 2009)
- Setup
Starmaze Experiment (Igloi et. al 2009)
- Results
Starmaze Experiment (Igloi et. al 2009)
- Results
Starmaze Experiment (Igloi et. al 2009)
- Results
Starmaze Experiment (Igloi et. al 2009)
- Results
Starmaze Experiment (Igloi et. al 2009)
- Results
Vistaspace Experiment
- Setup
Evaluating different strategies of the agent
9 vista spaces
several cues located in environment
Vistaspace Experiment
- Results (unblocked environment)
Vistaspace Experiment
- Results (unblocked environment)
Vistaspace Experiment
- Results (blocked environment, uninformed agent)
Vistaspace Experiment
- Results (blocked environment, uninformed agent)
Vistaspace Experiment
- Results (blocked environment, informed agent)
Vistaspace Experiment
- Results (blocked environment, informed agent)
Conclusion
The simulated agent was able to exhibit similar neuronal activity as in rats in Wilber et al.
➡ The system is biologically plausible.
We could explain switches of strategies by means of a confidence system that is continuously updated by the agent, based on the suggested movement of each strategy. Therefore we can also support the argument for simultaneously maintained strategies.
➡ Supports the argument of Iglio et al. of simultaneously maintained navigation strategies.
Conclusion
We could show that the agent’s overall performance increased when using the route-centric strategy between vista spaces. However if a path is blocked the agent can benefit from the ability of applyingother strategies.
It made it flexible to react to sudden changes even without an implemented learning system
➡ It seems reasonable that our agent implicitly used a hierarchical memory system of spaces