Dynamics%20and%20Timing%20in%20Birdsong

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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 hdia_at_jacobi.ucsd.edu Leif Gibb,
Gabriel Mindlin, Misha Rabinovich, Sachin
Talathi Conversations with Michael Brainard,
Allison Doupe, David Perkel
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Green Pre-motor Pathway NIf (?)?HVc?RA? Respirat
ion/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
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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)
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Deafen Juvenilesong develops incorrectly Lesion
lMAN in juvenile---song mismatches template
crystallization occurs early. Deafen adultsong
slowly degrades Lesion lMAN in adult--song
stable Deafen adult and lesion lMANsong
stable Lesion HVc or RAno song produced
------------------------- lMAN (and AFP)
important in maintaining song when auditory
feedback worksnot deaf
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Song is group of motifsabout 1 sec
eachcomposed of groups of syllablesabout
100-300 ms. Zebra Finch bout (song) is about
2-3 motifs
(Hahnloser, Kozhevnikov, and Fee 2002)
When bird sings, HVc--gtRA 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.
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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 AFPX,
DLM, lMAN is important Kimpo, Theunissen, Doupe,
2003
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• We will discuss three topics
• 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 wont be discussing
• connectivity of HVc?RA in producing song
  syllables

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A 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.
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Motor Instructions Auditory Feedback
Excitation
HVc
Inhibition
AFP
Area X
DLM
RA
lMAN
Motor Signaling
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HVc?RA Plasticity
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In adult zebra finch HVc signals arrive at
dendritic location with about 11 NMDA to AMPA
receptors. In adult zebra finch lMAN signals
arrive at RA dendritic locations with 101 NMDA
to AMPA. RA projection neurons (PNs) oscillate
at 15-30 Hz at resti.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
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From lMAN
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
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We present bursts of NHVc spikes with fixed
interspike intervals (ISIs) to RA neurons and ?T
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 ?g for AMPA receptors.
NHVc
NlMAN
?T
Time
The idea, following the observations of Yang,
Tang, and Zucker, 1999 is that long term changes
in ?g, LTP and LTD, can be induced by
postsynaptic Ca changes alone. The mechanisms
leading from Ca elevation to changes in ?g are
not fully known.
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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)
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Phenomenological Connection between Ca elevation
and ?g
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Spike Timing Induction Protocol
Time
Action potential arrives at presynaptic terminal
Action potential induced in postsynaptic neuron
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We present bursts of NHVc spikes with fixed
interspike intervals (ISIs) to RA neurons and ?T
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 ?g for AMPA receptors.
NHVc
NlMAN
?T
Time
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Lesion lMAN ?gRA0
Crystallization of song ?gRA0 Stable??
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Dynamics of the Anterior Forebrain Pathway
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AFP HVc? X?DLM?lMAN?X ?RA
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Motor Instructions Auditory Feedback
HVc
AFP
Excitation
Inhibition
Area X
DLM
RA
lMAN
Motor Signaling
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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.
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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
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Burst of spikes arrives from HVc at X at t 4000
ms
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Burst of spikes arrives from HVc at X at t 4000
ms
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Motor Instructions Auditory Feedback
HVc
Now connect in RA?DLM link
Area X
DLM
RA
lMAN
Motor Signaling
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With RA?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)?gRA(0), gRA(2) gRA(1)?gRA(1), .,
gRA(N) gRA(N-1)?gRA(N-1) . This is a
nonlinear map gRA(N) ? gRA(N1). The results for
large N depend on RIE and gRA(0), as ever with
such maps.
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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 RADLM 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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