Psyc 112 Lecture 03 Cockroach escape mechanism

Cockroach

Knows where toad tongue is in total darkness and it's already turning and dodges

-not visual

-16ms before tongue is visible the cockroach is already turning

-wind?

What stimuli do cockroaches use to escape

-Vision X

-Smell X

-Sound X

-Wind Turbulence !!!

Cerci *Experiment

Extentions of an insects abdomen used to give an insect a sense of touch at the back of the body.

Tiny hairs are found here.

Glue Experiment (Camhi) :When the Cerci are glued only 8% instead of 55%

Escape response drops

controlled lab *Experiment

Using wind puffs Camhi found

-Critical Stimulus values

Min Velocity: 12mm/sec

Min acceleration = 600mm/sec^2

Note:Toad lunge causes the S to occur 4-msec before escape R and cockroach initated a turn 16msec before tongue is seen

Variables:

T=tongue is visible (last)

R=cockroach escape goes

S:stimulus begins escape (happens before R)

-Main cue is acceleration not velocity

Critical Stimulus Values

min velocity of 12mm/sec

min acceleration of 600mm/sec^2

-causes cockroach escape response

ex: although cockroach runs fast it's acceleration is low so it does not trigger its own response

-around 40-80msec the cockroach has detected the response, occurs in 16ms after that

How does the cockroach know which way to turn

Abdominal Ganglia

Thoracic ganglia

head/Sub

7 pairs of giant interneurons found in terminal ganglia (on each side)-GI 1-7

Cerci structure

19 segments

220 hairs

9 hairs per segment

arranged in functional columns (hair b is found in the same column of another segment downwards and upwards)

-kinda look like arrows and therefore have preferred directions of movement

-one direction depolarizers and the other hyperpolarizes

Direction selectivity slide

Explains the direction angle the wind is coming

each vertical cal line is an action potential

in the slide there was a lot of AP in the 30 degree left side but less from right side

polar directional plot (direction and length shows how many AP and the whole graph is for one GI)

G2 mainly back

G1 Left and back

GI4 non directional

Underlying mechanism of GI direction selectivity

Convergence

+/- balance

synaptic weights

ex: GI1

: Selective for back left

-Why?

GI1 gets input from only four of those hairs on the segment

a h i m (convergence)

m and I are super strong in synaptic weight compared to a and h (synaptic weight)

GI3 gets different inputs that hyperpolairze or depolarize

(convergence, weights are the same, and +-)

Lesion experiment

If there is only one (right) GI on the other side and the wind comes from the left

2. If the brain asks which side is more active then it will turn towards the wind bc right is greater than the nonexistent left *

-turns the opposite direction for whatever direction has the HIGHEST response

Ex: Right is higher bc left is deleted so it turns left

Control and sham control

Left alone

Stabbed with needle

Reflex Circuit

IPAD