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Dynamics and Timing in Birdsong Henry D. I. Abarbanel Department of Physics and Marine Physical Laboratory (Scripps Institution of Oceanography) Center for Theoretical Biological Physics University of California, San Diego [email protected]

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Dynamics and Timing in Birdsong

Henry D. I. Abarbanel

Department of Physics

and

Marine Physical Laboratory (Scripps Institution of Oceanography)

Center for Theoretical Biological Physics

University of California, San Diego

[email protected]

Leif Gibb, Gabriel Mindlin, Misha Rabinovich, Sachin Talathi

Conversations with Michael Brainard, Allison Doupe, David Perkel


Auditory Feedback

Green:

Pre-motor Pathway

NIf (?)HVcRA

Respiration/Syrinx

Song Production

Red:

Anterior Forebrain Pathway (AFP)

HVcArea DLM

lMANArea X

HVc

Control and Song Maintenance

Songbox

From Brainard and Doupe, 2002


Tutor sings during sensory period. Bird memorizes template

Bird sings own song; learns memorized song matching template-- sensorimotor period.

Song “matches” template and reaches crystallization

(Brainard and Doupe 2002)


Auditory Feedback

Deafen Juvenile—song develops “incorrectly”

Lesion lMAN in juvenile---song mismatches template; crystallization occurs early.

Deafen adult—song slowly degrades

Lesion lMAN in adult--song stable

Deafen adult and lesion lMAN—song stable

Lesion HVc or RA—no song produced -------------------------

lMAN (and AFP) important in maintaining song when auditory feedback works—not deaf


Song is group of motifs—about 1 sec each—composed of groups of syllables—about 100-300 ms.

Zebra Finch bout (song) is about 2-3 motifs

(Hahnloser, Kozhevnikov, and Fee 2002)

When bird sings, HVc-->RA fires sparse bursts of spikes: one burst of 4.5 ± 2 spikes in 6.1 ± 2 ms in each motif. RA neurons fire 13 times more often, suggests one-to-many HVcRA connections

HVc acts as driver of song instructions. RA acts as “junction box” distributing commands to motor processes.


Auditory Feedback groups of syllables—about 100-300 ms.

Time difference in signal from HVcRA and HVcAFPRA is measured to be 50 ±10 ms.

AFP nuclei act as a population

Dynamics of AFP—X, DLM, lMAN is important

Kimpo, Theunissen, Doupe, 2003


We will discuss three topics: groups of syllables—about 100-300 ms.

  • plasticity at HVcRA connections. The alteration of these connections during song learning sets up wiring in song “junction box” (RA).

    This suggests a critical timing of about 40-50 ms.

  • dynamics of AFP and timing of signals from HVcAFPRA: origin of “40 ms”

  • RADLM connection to stabilize synaptic plasticity at HVcRA junction

    We won’t be discussing:

  • connectivity of HVcRA in producing song syllables


A groups of syllables—about 100-300 ms. full theory, which we do not have, would connect HVc sparse bursts with auditory feedback and command signals from brain.

It would trace HVc signals to RA, directly and through AFP, and explain evaluation of produced song through auditory feedback to HVc.

At best we have the beginning of a quantitative picture of the timing issues in the neural part of this loop.


Motor Instructions Auditory Feedback groups of syllables—about 100-300 ms.

Excitation

HVc

Inhibition

AFP

Area X

DLM

RA

lMAN

Motor Signaling


HVc groups of syllables—about 100-300 ms. RA Plasticity


In adult zebra finch HVc signals arrive at dendritic location with about 1:1 NMDA to AMPA receptors.

In adult zebra finch lMAN signals arrive at RA dendritic locations with 10:1 NMDA to AMPA.

RA projection neurons (PNs) oscillate at 15-30 Hz “at rest”—i.e. no song. When singing begins, global inhibition in RA puts these PNs into small subthreshold variations. These are then driven by high frequency (500-600 Hz) HVc signals

We model “whole” RA with oscillations, etc.

Stark and Perkel, 1999


From lMAN location with about 1:1 NMDA to AMPA receptors.

From HVc

RAPN

RAPN

RA

RAIN

To DLMIN

Excitation

At “rest” (no song) RA PN

oscillates at 15-30 Hz; RA IN is silent

Inhibition


We present bursts of N location with about 1:1 NMDA to AMPA receptors. HVc spikes with fixed interspike intervals (ISIs) to RA neurons and ΔT later present NlMAN spikes. We determine VRA(t) from HH equations. Then using a calcium flux equation we determine from which, using a phenomenological connection between elevation over equilibrium intracellular Ca, we determine Δg for AMPA receptors.

NHVc

ΔT

NlMAN

Time

The idea, following the observations of Yang, Tang, and Zucker, 1999 is that long term changes in Δg, LTP and LTD, can be induced by postsynaptic Ca changes alone. The mechanisms leading from Ca elevation to changes in Δg are not fully known.


From HVc or lMAN location with about 1:1 NMDA to AMPA receptors.

Presynaptic Membrane

Vpre(t) action potential leads to release of neurotransmitter--glutamate

Mg2+

Postsynaptic Membrane

NMDA Receptor

AMPA Receptor

RA Neuron PN

Voltage Gated Calcium Channel

[Ca2+](t) = Ca(t)

Vpost(t)


Phenomenological Connection between Ca elevation and location with about 1:1 NMDA to AMPA receptors. Δg


Spike Timing Induction Protocol location with about 1:1 NMDA to AMPA receptors.

Time

Action potential arrives at presynaptic terminal

Action potential induced in postsynaptic neuron


We present bursts of N location with about 1:1 NMDA to AMPA receptors. HVc spikes with fixed interspike intervals (ISIs) to RA neurons and ΔT later present NlMAN spikes. Using a simple voltage equation for RA membrane voltage, we determine VRA(t). Then using a calcium flux equation we determine from which, using a phenomenological connection between elevation over equilibrium intracellular Ca, we determine Δg for AMPA receptors.

NHVc

ΔT

NlMAN

Time


Lesion lMAN location with about 1:1 NMDA to AMPA receptors. ΔgRA=0

Crystallization of song ΔgRA=0

Stable??


Dynamics of the location with about 1:1 NMDA to AMPA receptors. Anterior Forebrain Pathway


Auditory Feedback location with about 1:1 NMDA to AMPA receptors.

AFP:

HVc

XDLMlMANX

RA


Motor Instructions Auditory Feedback location with about 1:1 NMDA to AMPA receptors.

HVc

Excitation

AFP

Inhibition

Area X

DLM

RA

lMAN

Motor Signaling


Signal from HVc activates SN which inhibits AF allowing DLM to fire.

With no input SN cells are at rest;

AF cells fire periodically at 15-30 Hz.


Timing for signals to traverse the AFP depends on distribution of inhibition and excitation. In a coarse grained sense, the ratio RIE = gI/gE determines time delay


R distribution of inhibition and excitation. In a coarse grained sense, the ratio IE = 4

Burst of spikes arrives from HVc at X at t = 4000 ms


Burst of spikes arrives from HVc at X at t = 4000 ms distribution of inhibition and excitation. In a coarse grained sense, the ratio


Motor Instructions Auditory Feedback distribution of inhibition and excitation. In a coarse grained sense, the ratio

Now connect in RADLM link

HVc

Area X

DLM

RA

lMAN

Motor Signaling


With RA distribution of inhibition and excitation. In a coarse grained sense, the ratio DLM connection in we present N = 1,2 , … bursts from HVc to RA and to Area X. Each burst is 5 spikes with ISI = 2 ms.

Before spiking we have the HVcRA AMPA strength set at the initial condition gRA(0), then we compute gRA(1) = gRA(0)+ΔgRA(0), gRA(2) = gRA(1)+ΔgRA(1), .…, gRA(N) = gRA(N-1)+ΔgRA(N-1) .

This is a nonlinear map gRA(N)  gRA(N+1). The results for large N depend on RIE and gRA(0), as ever with such maps.


Auditory Feedback distribution of inhibition and excitation. In a coarse grained sense, the ratio

Can we change AFP time delay with neuromodulators??

Can we block GABA or decrease inhibition in AFP? or excitation?

Dopamine is known to modulate excitation in Area X.

Tests of properties of RA—DLM connection.

Plasticity not yet found at HVcRA PNs !!!

Where is tutor template?

How does auditory feedback work?

What are the dynamics of HVc? WLC???


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