a Model of the Avian Superior Olivary Nucleus

a Model of the Avian Superior Olivary Nucleus

Raúl Rodríguez EstebanMaster Thesis Defense

August 1, 2002

Computational

Sensorimotor

Systems

Lab


August 1st, 2002

How does the owl hunt in total darkness ?

Comparing the sound cues of its earsRaúl Rodríguez EstebanMaster Thesis Defense

August 1st, 2002


August 1st, 2002

Objectives of the model

• In particular, its influence in the coincidence detection process

• Study the role of the Superior Olivary Nucleus (SON) in the auditory system of the avians


August 1st, 2002

Auditory circuitry

NM NA

Section of a chicken brainstem

SON

NL


August 1st, 2002

Sound localization in avians

ITD:Azimuth(longitude)

Interaural Time Difference (ITD)

ILD: Elevation (latitude)

Interaural Level Difference (ILD)


August 1st, 2002

Two pathways for two coordinates

Sullivan and Konishi (1984)

NANA

ILD pathway

NMNM

ITD pathway


August 1st, 2002

Nucleus Angularis (NA)

NANMNMNA


August 1st, 2002Soares et al. (2001)

Features: - Tonotopic organization- Anatomically, 4 kinds of cells

Features: - Tonotopic organization- Anatomically, 4 kinds of cells


August 1st, 2002

NMNM

Features: - Physiologically, 5 kinds of cells

Features: - Physiologically, 5 kinds of cells

Nucleus Angularis (NA)

NANA


August 1st, 2002

dampedtonic I tonic III

tonic II

one-spike

Soares et al. (2002)


August 1st, 2002

Nucleus Magnocellularis (NM)

NANMNMNA


August 1st, 2002

Features: - Tonotopic organization- Spherical soma with few dendrites

Features: - Tonotopic organization- Spherical soma with few dendrites

Phase locking


August 1st, 2002

The ITD pathway

NMNM

NL

Parks and Rubel (1975)


August 1st, 2002

Features: - Tonotopic organization- Bilateral dendrites with a length that depends on the frequency- Inputs that follow the Jeffress model

Features: - Tonotopic organization- Bilateral dendrites with a length that depends on the frequency- Inputs that follow the Jeffress model

Nucleus Laminaris (NL)

NMNM


August 1st, 2002

NMNM

NL

Coincidence Detection

‘AND gate’


August 1st, 2002


NMNM


August 1st, 2002

NMNM

NL

Problems

Bilateral summation


August 1st, 2002


NMNM


August 1st, 2002

NMNM

NL

Problems

Timing errors


August 1st, 2002

The Superior Olivary Nucleus (SON)

NM

NL

NA

SON

Yang et al. (1999)

Excitatory

Inhibitory


August 1st, 2002

Model proposal

Banks and Sachs (1991)Yang et al. (1999)


August 1st, 2002

Electrical behavior of neurons

Passive(Rall)

Active(Hodgkin & Huxley)

• Every part of the cell can be approximated as a piece of cable (compartment)

• Branched areas can be simplified as much as we need

• The soma and the axon have gates that are opened at certain voltages

• These gates can be described mathematically


August 1st, 2002

Passive behavior

-0.12

-0.08

-0.04

0

-0.12

-0.08

-0.04

0

Data recorded by Katrina MacleodBall-and-stick model (Rall 1959, 1960)


August 1st, 2002

Active behavior

-0.08

-0.04

0

0.04

-0.08

-0.04

0

0.04

Hodgkin and Huxley (1952)

Data recorded by Katrina Macleod


August 1st, 2002

Model proposal

lden=120mdden=4.8m

laxon=40mdaxon=4.8m

dsoma=18m


August 1st, 2002

The SON model connected

SONConnections not modeled

NA

Components modeled and unknown

NL

NM

Model by Jonathan Z. Simon

Sound

Simon et al. (2001)

Connections alreadystudied

Funabiki et al. (1998)Yang et al. (1999)


August 1st, 2002

Results: improvement of the coincidence detection in NL

• Reducing high frequency mistakes due to bilateral summation

• Increasing the discrimination ratio by reducing ‘good’ and mistaken spikes evenly

0

800

0 30 60SON spike rate (Hz)

NL spike rate (Hz)

0

4

8

12

Discrimination

In phase

Out of phase

Discrimination

0

800


NL spike rate (Hz)

0

4

8

12

Discrimination

In phase

Out of phase

Discrimination

• These improvements occur only in certain cases

0

400


NL spike rate (Hz)

0

2

Discrimination

In phase

Out of phase

In phase, one SON

Out of phase, one SON

Discrimination

0

400


NL spike rate (Hz)

0

2

Discrimination

In phase

Out of phase

In phase, one SON

Out of phase, one SON

Discrimination


August 1st, 2002

Results: hypothesis about the heterogeneity of the SON

• Three studies talk about the anatomical and physiological heterogeneity of the SON cells

(Takahashi and Konishi, 1988; Carr et al., 1989; Lachica et al., 1994)

• However, the most recent study declares homogeneity, although using a small

sample (n=23)(Yang et al., 1999)

• Our model suggests that there is some kind of physiological or anatomical

adaptation for different types of inputs


August 1st, 2002

Future work

• Assess the relationship between the NA and the SON

• Simulate heterogeneity in the SON cells

• Link the NM to the SON


August 1st, 2002

Acknowledgements

• Jonathan Simon• Katrina Macleod• Catherine Carr• Daphne Soares

• Sridhar Kalluri• Michael Burger• Nichola O’Hara

• Hisham Abdalla• Matt Cheely• Timothy Horiuchi• Rock Shi

• Jonathan Fritz• Mounya El Hilali• Nikolaos KanlisAnd the rest of the NS Lab


August 1st, 2002

Results: the parameters of the model

a Model of the Avian Superior Olivary Nucleus

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