Michael P. Kilgard
Sensory Experience and Cortical Plasticity
University of Texas at Dallas
20±10 vs. 75±20 μV 81±19 vs. 37±20 μV
0 50 100 150 200 250
Week 1
Am
plit
ud
e (
mV
)
Time (ms)0 50 100 150 200 250
Week 2
Time (ms)0 50 100 150 200 250
Week 5
Time (ms)
0 50 100 150 200 250
Week 12
Time (ms)
.10
.05
0
-.05
-.10
Red Group Enriched Blue Enriched
Environmental Enrichment
22 rats total
• 40% increase in response strength– 1.4 vs. 1.0 spikes per noise burst (p< 0.0001)
• 10% decrease in frequency bandwidth– 2.0 vs. 2.2 octaves at 40dB above threshold (p< 0.05)
• Three decibel decrease in threshold– 17 vs. 20 dB ms (p< 0.001)
1 2 4 8 16 320
20
40
60
80
Frequency (kHz)
Inte
nsity
(dB
SP
L)
A.
1 2 4 8 16 320
20
40
60
80
Frequency (kHz)
Inte
nsity
(dB
SP
L)
B.
0 10 20 30 400
50
100C.
Time (ms)
Spi
kes/
s
1 2 4 8 16 320
20
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Frequency (kHz)
Inte
nsity
(dB
SP
L)
A.
1 2 4 8 16 320
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Frequency (kHz)
Inte
nsity
(dB
SP
L)
B.
0 10 20 30 400
50
100C.
Time (ms)
Spi
kes/
s
Enriched
Standard
A1 Enrichment Effects - after 2 months
N = 16 rats, 820 sites
Stronger, More Selective, and More Sensitive
Environmental Enrichment Improves Response Strength, Threshold, Selectivity, and Latency of Auditory Cortex Neurons Engineer ND, Percaccio CR, Pandya PK, Moucha R, Rathbun DL, Kilgard MP. Journal of Neurophysiology, 2004.
High
Low
Cochlea Cortex
High
Low
Cochlea Cortex
Cortical Map Plasticity
High-density microelectrode mapping technique
Best Frequency
Nucleus Basalis Activity Enables Cortical Map ReorganizationM.P. Kilgard, M.M. Merzenich, Science 279(5357): 1714-1718, 1998. download file
Tone Frequency - kHz
Nucleus Basalis Stimulation Generates Frequency-Specific
Map Plasticity
N = 20 rats; 1,060 A1 sites
Differences between A1 and Posterior Auditory Field – submitted
2 4 8 16 32
10
30
50
70
Controls - Percent of PAF Responding
Inte
nsi
ty (
dB
)
A
0
20
40
60
80
100
2 4 8 16 32
10
30
50
70
19kHz paired - Percent of PAF Responding
Inte
nsi
ty (
dB
)
B
-20
-10
0
10
20
2 4 8 16 32
10
30
50
70
Difference in PAF Percent after 19 kHz Paired
Inte
nsi
ty (
dB
)
Tone Frequency (kHz)
C
• High frequency map expansion , p<0.01
• Decreased bandwidth (30 dB above threshold)
– 3.0 vs. 3.6 octaves, p<0.001
• Shorter time to peak– 56 vs. 73 ms, p<.01
Plasticity in Posterior Auditory Field
N = 12 rats; 396 PAF sites
Manuscript in preparation
Temporal Processing
Typical Response of A1 Neurons to Tone Trains
• After Pairing NB Stimulation with 15 Hz Tone Trains
• After Pairing NB Stimulation with 5 Hz Tone Trains
N = 15 rats, 720 sites
Plasticity of Temporal Information Processing
in the Primary Auditory Cortex M.P. Kilgard, M.M. Merzenich
Nature Neuroscience1(8): 727-731, 1998
download file
Stimulus Paired with NB Activation Determines
Degree and Direction of Receptive Field Plasticity
Frequency Bandwidth Plasticity N = 52 rats; 2,616 sites
Frequency Bandwidth is Shaped by Spatial and Temporal Stimulus Features
Modulation Rate (pps)0 5 10 15
Ton
e P
rob
abil
ity
15%
50 %
10
0%
Spatial Variability
Leads toSmaller RF’s
Temporal Modulation
Leads toLarger RF’s
Sensory Input Directs Spatial and Temporal Plasticity in Primary Auditory CortexM.P. Kilgard, P.K. Pandya, J.L. Vazquez, Gehi, A., C.E. Schreiner, M.M. Merzenich
Journal of Neurophysiology, 86: 339-353, 2001. download file
How do neural networks learn to represent complex sounds?
• Spectrotemporal Sequences
100ms 20ms
High Tone(12 kHz)
Low Tone(5 kHz)
Noise Burst
Paired w/ NB stimulation
100ms 20ms
High Tone(12 kHz)
Low Tone(5 kHz)
Noise Burst
Unpaired background
sounds}
Context-Dependent Facilitation
100ms 20ms
High Tone(12 kHz)
Low Tone(5 kHz)
Noise Burst
Num
ber
of S
pike
s0 100 200 300 400ms
• 58% of sites respond with more spikes to the noise when preceded by the high and low tones, compared to 35% in naïve animals. (p< 0.01)
Context-Dependent Facilitation - Group Data
100ms 20ms
Low Tone(5 kHz)
Noise Burst
Noise Burst
High Tone(12 kHz)
N = 13 rats, 261 sites
Order Sensitive Plasticity in Adult Primary Auditory CortexM.P. Kilgard, M.M. Merzenich
Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file
SchematicIllustration
• 25% of sites respond with more spikes to the low tone when preceded by the high tone, compared to 5% of sites in naïve animals. (p< 0.005)
Context-Dependent Facilitation - Group Data
Low Tone(5 kHz)
100ms 20ms
High Tone(12 kHz)
Low Tone(5 kHz)
Noise Burst
N = 13 rats, 261 sites
Order Sensitive Plasticity in Adult Primary Auditory CortexM.P. Kilgard, M.M. Merzenich
Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file
SchematicIllustration
• 10% of sites respond with more spikes to the high tone when preceded by the low tone, compared to 13% of sites in naïve animals.
Context-Dependent Facilitation - Group Data
100ms 20ms
Noise Burst
High Tone(12 kHz)
High Tone(12 kHz)
N = 13 rats, 261 sites
Low Tone(5 kHz)
Order Sensitive Plasticity in Adult Primary Auditory CortexM.P. Kilgard, M.M. Merzenich
Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file
SchematicIllustration
Target stimulus (CS+)
Add first distractor
(CS-1)
Add second distractor
(CS-2)
Add third distractor
(CS-3)
Task
A) Sequence detection
B) Frequency discrimination
C) Triplet distractor- High first
D) Sequence element discrimination
E) Triplet distractor- Noise first
F) Reverse Order
Fre
quen
cy (
kHz)
Time (ms)
H L N
H L N
L L L H H H
H H H
H H H
L L L
L L L
N N N
N N N
NL
N L H
H
H L N
H L N
H L N
None
None
None None
None
None None
Map Auditory Cortex
Time (months)
Operant Training
Discrimination Performance
Differential Plasticity Effects
How do cortical neurons learn to represent speech sounds?
Sash
‘SASH’ Group - Spectrotemporal discharge patterns of A1 neurons to ‘sash’ vocalization (n= 5 rats)
kHz
16kHz @50dB:
35 % 1.9
55 % 5.3
(p<0.0005)
Sensory Experience Controls:
• Response Strength
• Cortical Topography
• Receptive Field Size
• Maximum Following Rate
• Synchronization
• Spectrotemporal Selectivity
050
100150
Spi
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Rat
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z)
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Rat
e (H
z)
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Rat
e (H
z)F
requ
ency
(kH
z)
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quen
cy (
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quen
cy (
kHz)
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5 102025
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A) 'back' E) 'back' - modified
B) 'pack' F) 'pack' - modified
C) 'sash' G) 'sash' - modified
50 100 150 200 250 300 350
50
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Time (ms)
Spi
ke
Rat
e (H
z)
pack
backa sh
D) Neural responses to normal speech
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50
100
150
Time (ms)
ba
p as a
ck
cksh
H) Neural responses to modified speech
Activity from a single A1 neuron recorded in an awake rat
in response to normal and enhanced human speech sounds
Behavioral Relevance
Neural Activity
- Internal Representation
External World-Sensory Input
Neural Plasticity- Learning and
Memory
Plasticity Rules- Educated Guess
BehavioralChange
Training Experiments - Navzer Engineer
Amanda Puckett
Crystal Novitski
Enrichment Experiments - Navzer Engineer
Cherie Percaccio
Receptive Field Plasticity - Pritesh Pandya
Synchrony Experiments - Jessica Vazquez
FM Experiments - Raluca Moucha
Speech Experiments - Pritesh Pandya
and
Acknowledgements:
and