Spatial World Flashcards
To generate a rapid action a system could use:
Feedforward / Open Loop Control: A preprogrammed set of commands.
Feedback / Closed Loop Control: Rapid pick-up and processing of useful information to ensure accuracy.
Feedforward Mechanism:
Reference input–>Controller–Motor Command–>Plant–Motor/Sensory Noise–>Action Output
Define reference input
The reference input is the desired outcome or target of the motor action.
Define Controller
The controller is the decision-making mechanism that compares the reference input (desired action) with the actual state (current action) and generates the necessary signals to bring the system closer to the desired outcome.
Define Plant
The plant refers to the physical system being controlled e.g. body, car
Define Internal Model
The internal model is the brain’s or controller’s representation of the plant and the environment. It is used to predict the outcomes of motor commands and plan actions
What is Sensory Noise?
Sensory noise refers to the random variability or inaccuracies in the sensory signals received by the brain or a control system
How does the feedback (closed loop) mechanism differ from feedforward?
- The system uses sensory feedback (such as visual, auditory, or proprioceptive information) to make corrections during the execution of the action
- potentially slower
2-point control model of steering:
near road: feedback from road edges
far road: prospective (feedforward) info
what is egocentric representation and allocentric representation?
- An egocentric representation is a self-centered view of the environment, where spatial relationships are encoded relative to the individual’s current position and orientation.
- An allocentric representation is a world-centered view of the environment, where spatial relationships between objects are encoded independently of the individual’s position or orientation.
what is unilateral neglect?
a neurological condition in which a person is unable to attend to or recognize stimuli on one side of their body or space, typically the left side, following damage to one hemisphere of the brain
unilateral neglect: what parts of the brain are damaged?
usually lesions involve the supramarginal gyrus in the inferior parietal lobule, at the temporoparietal junction
what were the findings of the milan square experiment (Bisiach & Luzzatt, 1978)
Patients asked to imagine
standing in the square facing
the cathedral (North) could
describe the East side of it.
They could NOT describe the
West side.
But when asked to imagine
facing the other way (away
from the cathedral), they
COULD now describe the
West side but NOT the East.
participants could retrieve information from an allocentric representation of the square
it was the egocentric representation that was impaired
which part of the brain is used for allocentric representations?
hippocampus and parahippocampal regions
what is locomotion
monitoring current direction of motion and altering it to reach a target
Summarise the findings of Wallis et al.’s 2007 steering experiment
The data suggest that vehicle steering control can be characterized as a series of unidirectional, open-loop steering movements, each punctuated by a brief visual update.
what is haptics
relating to the sense of touch
what is proprioception
perception or awareness of the position and movement of the body
why do we need to combine different sensory sources?
- Visual-auditory spatial
localisation (twilight, peripheral
visual field, occlusion, cluttered
scenes)
– Reliable information for control
of locomotion (e.g. decreased
use of optic flow at night: Wilkie
and Wann, 2002)
– Retain coherence of the world:
object unity, perceiving one’s own
presence in space (e.g. cue
conflict = motion sickness)
Ernst & Banks (2002) used a
VR setup to examine grasping
objects…
Conditions could be either:
– a stereo visual display only
– haptic inspection (touch) only
– both sources available
* Task: judge size of objects
(“which stimuli larger?”) in the
presence of various amounts
of visual noise.
* Haptic information had no
noise added.
- the haptic only condition was not affected by visual noise
- the visual only condition was initiallay better than haptic but decreased as visual noiose increased
- the combined condition decreased with increased visual noise, but less than the visual only condition. suggesting that haptics were used with vision
how does our brain know where our body is?
Proprioception
- stretch receptors (muscles and joint ligaments)
- vestibular system (semicircular canals and otolith organs)
Vision
how does the brain know where the body is going, using egocentric cues?
- Retinal Flow
- Optic Expansion
- Visual Direction
- Idiothetic Cues
The _____ rim area of the ant
eye is specialised and hard-
wired for detecting the
_______of polarised light
The dorsal rim area of the ant
eye is specialised and hard-
wired for detecting the
direction of polarised light
The pattern of electric vectors
of light are known as:
e-vectors
what are the steps pf an ants path integration?
- Tracking Distance (Odometry)
- Tracking Direction (Compass Mechanism)
- Vector Summation
- Returning Home
How do ants track distance?
Ants track the distance they travel by essentially “counting their steps.” This process is called odometry. Research suggests that ants measure the distance they walk based on the number of steps they take and the length of their stride.
In experiments where scientists altered the length of ants’ legs (by shortening or lengthening them), the ants would misjudge the distance to their nest, which confirms that they rely on step-counting to estimate distance traveled. (Wittlinger, M., Wehner, R. & Wolf, H. (2006) The Ant
Odometer: Stepping on Stilts &
Stumps, Science)
they also use optical flow (Ronacher &
Wehner, 1995))
how do ants track direction?
While traveling, ants continuously monitor the direction they are moving. To do this, they use the position of the sun and a form of polarized light as a compass. Polarized light is sunlight that scatters in different directions as it passes through the atmosphere, creating patterns that are invisible to humans but detectable by ants’ specialized photoreceptors.
Even on cloudy days, ants can detect polarized light patterns in the sky to maintain their sense of direction. By using this information, ants can keep track of the general bearing they are heading toward (for example, whether they’re moving east, west, etc.).
How does the ant get back home?
As the ant moves along its winding foraging path, it continually updates an internal “vector” that combines information about distance and direction. This vector points back to the nest. The ant essentially performs a continuous calculation of how far it has traveled and in which direction, constantly updating this information to always know the shortest route home.
This process is called vector summation, where each small segment of the ant’s path contributes to an overall directional vector, allowing the ant to compute a straight-line path back to its starting point, even if it wandered in complex patterns while foraging.
what are the 2 potential pitfalls of path integration?
- PI cannot be interrupted during
movement without introducing errors.
– PI is also susceptible to cumulative
errors of navigation (i.e. many small
errors results in a large error in the
return path)
Wehner, R., Michel, B., & Antonsen, P. (1996) Visual
Navigation in insects: coupling of egocentric and geocentric
information, Journal of Experimental Biology, 199, 129-140
define optic flow?
Optic flow is the pattern of apparent motion of objects, surfaces, and edges in a visual scene, caused by the relative motion between the observer and the scene. It provides important cues about speed, direction, and distance of movement, helping organisms navigate through their environment.
summarise duhamel’s experiment
Duhamel’s experiment shows that there are cells with particular properties: they fire when an object is in one location with respect to the head irrespective of where the eyes are pointing. Given the information used to detect the object is visual (from the eye), this shows that eye-movement signals are effectively being integrated (i.e. subtracted) in order to respond in this way.
define alpha nulling and which species uses it
summarise the findings of Land (1971)
