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Important requirements for JAR: Absolute value of the difference in frequency less than 20 Hz 2. Mixing of signals 3. Variation in mixing ratio 4. Modulation of phase and amplitude of the mixed signal.

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  • Important requirements for JAR:

  • Absolute value of the difference in frequency less than 20 Hz

  • 2. Mixing of signals

  • 3. Variation in mixing ratio

  • 4. Modulation of phase and amplitude of the mixed signal


The regularity of the electric organ discharge is determined by an endogenous oscillator in medulla oblongata called the pacemaker nucleus (PN).

100 hz

Electromotoneuron

PN

Natural

EO

100 hz

PN(f) = EOD (f)

Curare

Frequency varible

May or may not be

equal to PN(f)

Sine wave


EOD mimics elicit JAR by an endogenous oscillator in medulla oblongata called the pacemaker nucleus (PN).

sine

EOD replaced by electric sine wave of similar amplitude and frequency

EOD mimic (Sine) of neighbor’s electric field

Result: Correct jamming avoidance behavior

Lowers its pacemaker frequency if DF=(+)ve

Raises its pacemaker frequency if DF=(-)ve

Do not tell much about the behavioral mechanism involved in

determining the sign of DF.


NO INTERNAL REFERENCE by an endogenous oscillator in medulla oblongata called the pacemaker nucleus (PN).Uses the electrical field frequency rather than internal frequency of the pacemaker nucleus

Frequency of the EOD mimic (Sine) was decreased to a frequency 50 Hz below the frequency of the pacemaker nucleus

PN (f) = 300 hz, EOD mimic of self (Sine) = 250hz,

EOD mimic of neighbor (Sine) = 254hz

When confronted with neighbor’s EOD mimic it responded as if this 50 Hz lower frequency was its own frequency.


Fish needs a mixture of its own signal and neighbor’s signal to execute JAR

Electroreceptor

Fish placed in two compartment chamber

Pectoral region sealed

No EOD could be detected by head region

Jamming stimulus presented to the head

www.trilon.com/electricfish/

No JAR

capacitor

JAR elicited when

EOD leaked into head chamber

Jamming signal entered the tail chamber


Variation in mixing ratio
Variation in mixing ratio signal to execute JAR

A

Mimics of two EODs (Sine) were

added and presented.

Electrical fields had different

Frequency, but identical geometry

NO VARIATION IN MIXINGRATIO OVER BODY SURFACE----NO JAR

1:1

Under natural situation

electrical fields vary both in

frequency and geometry

VARIATION IN MIXING RATIO-----JAR

1:0.5


How are the behavioral rules for execution of a correct JAR implemented at the neural level?

ELL: electrosensory lateral line lobe

TS: torus semicircularis

nE: nucleus electrosensorius

PPn: prepacemaker nucleus

Pn: pacemaker nucleus

Electric organ

Extraction of the sine of DF by electrosensory processing of phase and

amplitude information

Translation of the determination of the sign of the DF into change of the motor output,

that is of the pacemaker frequency


Electrosensory processing I: implemented at the neural level?

Electroreceptors

Ampullary receptors:Tuned to DC and low frequency AC signals of both

biological and non biological sources.

Used for ---- Prey detection

Detection of earths magnetic field

Tuberous receptors: Tuned to AC signals with

frequencies in the range of fish’s own EOD

P type: Fire intermittently and increase their rate of firing with rise in stimulus amplitude.

T type: Fire one spike on each cycle of the stimulus.

Firing of T unit

Firing of P unit


Electrosensory processing II: implemented at the neural level?

Electrosensory lateral line lobe

(hind brain)

Tuberous

Ampullary

Lateral

Centrolateral

Centromedial

Medial

Somatotopically ordered

(preserves spatial order)

Parallel processing (Ptype and Ttype information processed seperately)

Inputs from several Ttype receptors are received by one sperical cell via electronic synapse

Ptype receptors form excitatory synapse onto basilar pyramidal cells and inhibitory synapse

onto nonbasilar pyramidal cells (via exciting the granule cells)

Excitation of basilar pyramidal cells reflect rise in stimulus amplitude

Inhibition of non basilar pyramidal cells reflectrise in stimulus amplitude

Excitationof non basilar pyramidalcells reflect fall of stimulus amplitude


Electrosensory processing III: implemented at the neural level?

Torus semicercularis

(midbrain)

Divided into laminae

Sperical cells project onto laminae 6

Encodes phase differences

Basilar and non basilar pyramidal cellsproject ontovarious laminae

Encodes phase and amplitude information

Convergence of amplitude and phase information is achieved by vertical connections between different layers


Electrosensory processing IV: implemented at the neural level?

Nucleus electrosensorius

(Diencephalon)

Receives input from torus semicircularis

Somatotopic arrangement of the toral layers is lost in this area

Cells encode sign of DF

Cells of dorsal part of nE raises the EOD frequency--- nE

Cells of ventral part of nE lowers the

EOD frequency---nE

Lglutamate – stimulate dorsal cluster -- raises EOD frequency

Lglutamate – stimulate ventral cluster -- lowers EOD frequency

Bilateral lesion of these two areas eliminate the frequency shift in the JAR.


Motor Control implemented at the neural level?

nE innervates via excitatory synapses the CP/PPn-G in dorsal thalamus

PPn- prepacemaker nucleus is the dorsolateral portion of central posterior nucleus

CP/PPn-G innervates Pacemaker cells via AMPA type glutamate receptors

Lesion or CNQX application abolishes frequency rise due to –ve DF

CNQX- 6 cyano 7 nitroquinoxaline –2,3- dione


nE innervates via inhibitory synapses (GABA) the implemented at the neural level?SPPn in mesencephalon

SPPn- sublemniscal prepacemaker nucleus

SPPn innervates Relay cells via NMDA type glutamate receptors

Lesion or APV application abolishes lowering of frequency due to +ve DF

APV- 2 amino 5 phosphonovaleric acid

Final motor control achieved in the Pacemaker nucleus


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