Chapter 8 - Sensorimotor integration

Question 1

Major components of the electric system

Answer 1

• Electroreceptors
• Electric organ
• Central structures devoted to the processing of electrosensory information and to the motor control of the electric organ discharge

Question 2

Is any living organism electric?

Answer 2

Yes

Question 3

Hans Werner Lissmann (1909-1995)

Answer 3

First to discover that weakly electric fish produce charges for navigation close-range

Question 4

How do electric fish obtain information about objects in their closer vicinity?

Answer 4

• Through analysis of distortions of the self-generated field surrounding them
  – If their field goes through a highly conductive object it goes straight through
  – If their field goes through a weakly conductive object it gets distorted and avoids it

Question 5

Walter Heiligenberg (1938-1994)

Answer 5

Explored entire neural pathway, including sensory and motor

Question 6

Jamming avoidance response

Answer 6

• Involves a shifting of the fish’s own frequency away from the frequency of the interfering signal
  – The fish with the slightly higher frequency will increase their frequency
  – The fish with the slightly lower frequency will decrease their frequency

Question 7

Frequency difference (Df)

Answer 7

Frequency of the neighbor’s signal minus frequency of the fish’s signal

Question 8

Curare

Answer 8

• Generic name for various types of unstandardized extracts derived mainly from the bark of tropical plants Strychnos and Chondrodendron
• Prepared for use as an extremely potent arrow poison by Indians in South America
• The physiological active ingredient of curare is the alkaloid tubocurarine, which is employed as a relaxant of skeletal muscles during surgery to control convulsions
  – The muscle-relaxant effect is caused by interference of the alkaloid with the action of acetylcholine at the neuromuscular junction
• Can block electric discharge (since electric organ is a modified muscle; however fictive behavior can still occur)

Question 9

Result of mixing the fish’s electric organ discharge and the interfering signal produced by a neighboring fish

Answer 9

Causes modulations of both amplitude and phase of the mixed signal relative to the fish’s signal

Question 10

Plotting in a 2D amplitude-versus-phase plane of the superposed signal produced by mixing the electric organ discharges of the two fish

Answer 10

• A circular trajectory is obtained, which repeats itself at a rate equal to the beat frequency of the mixed signal
• The sense of rotation reflects the sign of Df:
  – Clockwise rotation: S neighbor < S fish
  – Counterclockwise rotation: S neighbor > S fish

Question 11

Tuberous electroreceptors

Answer 11

• Two types
  – P-type receptors encode the amplitude
  – T-type receptors encode the phase (time) of the perceived electric signal

Question 12

In the electrosensory lateral line lobe…

Answer 12

Amplitude and phase information are processed in parallel

Question 13

In the torus semicircularis…

Answer 13

Amplitude and phase information converge

Question 14

Neurons of the nucleus electrosensorius…

Answer 14

• Encode the sign of the frequency difference between the fish’s signal and the discharges of the neighbor’s discharges unambiguously
• Contrast the torus semicircularis

Question 15

The final motor control of the jamming avoidance response is mediated through

Answer 15

Input to the pacemaker nucleus, originating from the ‘G’ portion of the central posterior/prepacemaker nucleus and the sublemniscal prepacemaker nucleus

Question 16

The imperfection of the jamming avoidance response can be explained by…

Answer 16

Its likely evolutionary development