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BBio 351: Principles of Anatomy & Physiology I
Winter 2016
Study Guide for Daniela Vallentin et al. (2016)
Note: This is not a study guide in the sense of “here are some questions to prepare you for the
test.” It is a study guide in the sense of “here is some background information to help you read
the paper.”
Reference: Daniella Vallentin et al. (2016), “Inhibition protects acquired song segments during
vocal training in zebra finches,” Science 351: 267-71.
Table of contents
1. The bottom line
2. GABA GABA GABA
3. Songbird brain anatomy
4. Temporal coding versus rate coding
5. Graph-reading tips
6. Figure titles show the article’s flow
7. Homework assignment
1. The bottom line
The overall conclusion of this paper is
depicted in Figure S10 (at right, with the
caption shown below; from the online
supplementary information). Thus, our bigpicture goal is to understand how the
experiments performed and data collected led
to this conclusion. Even more generally, we
want to understand how changing inhibitory
inputs into a neural circuit might affect the
function of that circuit, with the HVC of the
zebra finch simply serving as a convenient
example.
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Fig. S10. Model for neural mechanisms underlying
sensorimotor integration during HVC circuit
development. (A) In initial stages of learning, auditory
inputs are capable of driving HVC activity directly. Filled
circles indicate that neurons are firing in response to
the tutor song. (B) Once the bird has learned specific
song elements (e.g. syllable ‘A’), HVC premotor neurons
are selectively inhibited when observing that aspect of
the tutor song. (C) After the song has been learned
completely, inhibition shields HVC premotor neurons
from the impact of the tutor song.
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BBio 351: Principles of Anatomy & Physiology I
Winter 2016
2. GABA GABA GABA
Recall the following information about gamma-aminobutyric acid (GABA)…. It is a
neurotransmitter that can open Cl- channels or open K+ channels. Because of these ions’
electrochemical gradients, Cl- enters the cell at most normal membrane potentials, while K+
exits the cell at most normal membrane potentials. Either way, GABA causes IPSPs in postsynaptic cells and thus makes these cells less likely to reach threshold and fire action potentials.
In this paper, the premotor neurons of the HVC are inhibited by GABA-producing interneurons.
GABA’s effects were reversed with the GABA antagonist gabazine.
3. Songbird brain anatomy
The first sentence of the paper’s abstract states, “Vocal imitation involves incorporating
instructive auditory information into relevant motor circuits.” In songbirds such as zebra
finches, this task is accomplished partly by an area known as HVC. The diagram below shows
that HVC influences singing (controlled by RA) according to the auditory information that it
receives.
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BBio 351: Principles of Anatomy & Physiology I
Winter 2016
Among HVC neurons, we can distinguish between interneurons within the HVC and premotor
neurons that project from the HVC to the RA. The interneurons release GABA and, in doing so,
inhibit the premotor neurons.
4. Rate coding versus temporal coding
Introductory neurophysiology courses tend to emphasize that stimulus intensity is often
encoded in the frequency of action potentials (in Hertz), with higher frequencies often
indicating stronger stimuli. But sometimes this “rate coding” does not tell the whole story. In
contrast to rate coding, temporal coding provides information not in the overall firing rates but
in the specific temporal patterns of the firing. If a neuron fires at a consistent, very specific time
in response to a given stimulus, and/or fires in close synchrony with other neurons, this may be
evidence of temporal coding.
In this paper, the synchrony of neuron firing is reported as spike precision. The calculations are
explained in the paper’s online supplementary information; for our purposes, it’s enough to
know that this was a measure of how closely the spikes from different trials aligned with each
other. For example, Figures 1C and 1I show that spiking precision was higher during a tutor’s
song than during silence.
5. Graph-reading tips
This paper includes several types of figures that may be challenging to understand.
 Sonograms (with black backgrounds) are included in Figures 1A, 1D, 1G, 2A, 2B, 2E, 2F,
4B, and 4D. They are too small to be very useful, but they provide a record of sound
frequencies (pitches) over time. Here they are used as a record of singing by tutors and
pupils.
 Voltage traces can show either action potentials (e.g., Figure 1A and 1G) or postsynaptic potentials (PSPs; e.g., Figure 2E). Note that deflections in the positive direction
may represent IPSPs; check labels and legends carefully.
 To show lots of action potential data in a small space, this paper uses spike raster plots.
In these plots, each trial (e.g., each time the same tutor song is played) is represented in
a separate horizontal row, and each vertical line within the row represents an action
potential. For example, Figure 1A shows 7 different trials of the same premotor neuron
reacting to a tutor’s song. We can see from the raster plot that, during most trials, this
neuron fired an action potential about 1/3 of the way through the tutor’s song and
another action potential just before the end of the song. A similar pattern is seen in
Figure 1G.
6. Figure titles show the article’s flow
When you get lost in the details of the article, try to return to the bigger picture by referring to
the titles of the figures, which concisely summarize the overall progression of the study.
 Fig. 1. Responses of HVC premotor neurons are developmentally suppressed.
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BBio 351: Principles of Anatomy & Physiology I
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Winter 2016
Fig. 2. Tutor song-evoked inhibition strengthens and sharpens with improved song
performance.
Fig. 3. Learning is associated with synchronous network inhibition.
Fig. 4. Inhibition accurately targets learned portions of the tutor song.
7. Homework assignment
Consult Canvas for the homework assignment that is due Monday, March 7th by the start of
class.
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