L3- Simple Locomotor Control

Question 1

What is alpha nulling?

Answer 1

-Alpha is the angle between current heading (facing) direction and target direction
-Want alpha as close to 0

Question 2

How do jumping spiders change direction? Describe Land’s (1971) findings

Answer 2

-Jump straight to target direction
-Open loop (no feedback) yet turned appropriately
-Produced big turns when stimulus in visual periphery and small turns in principle eyes

Question 3

What is a constant alpha navigation strategy?

Answer 3

Constantly turning as you move means alpha doesnt change (constant), producing curved path towards target

Question 4

Why do raptors use constant alpha strategy

Answer 4

Line of sight (LOS) in eyes at 45 degrees for deep fovea (area with highest visual acuity)
-Flies in curve to keep target on deep fovea
-Doesnt turn head, to maintain aerodynamics, so flies curved
-Takes straight final dive at the end

Question 5

What locomotor trajectories do humans use?

Answer 5

Inbetween alpha nulling and constant alpha

Question 6

What strategy do bats use for locomotion?

Answer 6

Echolocation
-Perform complex and rapid flight trajectories

Question 7

Describe Ghose & Moss’ (2006) results

Answer 7

-Observed intermittent pulses of directed ultrasound
3 main phases of flight:
1). Search/approach
2). Tracking
3). Attack
-Each phase identified by Pulse Production Rate (PPR), which increases when target was found.
-Flight path starts to line up with beam axis
-Direct linear relationship observed between acoustic gaze and rate of change of flight direction
-Gaze angle provides direct input for steering control

Question 8

Describe the phases for lag and gain within flight for bats?

Answer 8

-Lag between gaze and steering reduces as bat starts attack phase
-The gain couples gaze and locomotion more tightly as bat progresses towards target
(gain of 1 = gaze angle matches flight angle)