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Sensory Experience and Cortical Plasticity Michael P. Kilgard University of Texas at Dallas Environmental Enrichment Red Group Enriched Blue Enriched 20 ± 10 vs. 75±20 μ V 81±19 vs. 37±20 μ V 22 rats total A1 Enrichment Effects - after 2 months Enriched Standard

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Sensory experience and cortical plasticity l.jpg

Sensory Experience and Cortical Plasticity

Michael P. Kilgard

University of Texas at Dallas


Slide3 l.jpg

Environmental

Enrichment

RedGroup Enriched

Blue Enriched

20±10 vs. 75±20μV81±19 vs. 37±20 μV

22 rats total


Slide4 l.jpg

A1 Enrichment Effects - after 2 months

Enriched

Standard

  • 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)

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.

N = 16 rats, 820 sites


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High

Low

Cochlea

Cortex


Slide6 l.jpg

High

Low

Cochlea

Cortex

Cortical Map Plasticity



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Best Frequency

Nucleus Basalis Activity Enables Cortical Map Reorganization

M.P. Kilgard, M.M. Merzenich, Science 279(5357): 1714-1718, 1998. download file


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Tone Frequency - kHz

Nucleus Basalis Stimulation Generates Frequency-Specific Map Plasticity

N = 20 rats; 1,060 A1 sites



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Plasticity in Posterior Auditory Field

  • 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

N = 12 rats; 396 PAF sites

Manuscript in preparation





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Plasticity of Temporal

Information Processing

in the Primary Auditory Cortex M.P. Kilgard, M.M. Merzenich

Nature Neuroscience

1(8): 727-731, 1998

download file

N = 15 rats, 720 sites


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Frequency Bandwidth Plasticity

N = 52 rats; 2,616 sites

Stimulus Paired with NB Activation Determines Degree and Direction of Receptive Field Plasticity


Frequency bandwidth is shaped by spatial and temporal stimulus features l.jpg

15% 50 % 100%

Tone Probability

0 5 10 15

Modulation Rate (pps)

Frequency Bandwidth is Shaped by Spatial and Temporal Stimulus Features

Temporal

Modulation

Leads to

Larger RF’s

Spatial

Variability

Leads to

Smaller RF’s

Sensory Input Directs Spatial and Temporal Plasticity in Primary Auditory Cortex

M.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


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How do neural networks learn to represent complex sounds?

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

  • Spectrotemporal Sequences


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Paired w/ NB stimulation

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

}

Unpaired background sounds


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Context-Dependent Facilitation

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

0 100 200 300 400ms

Number of Spikes


Slide22 l.jpg

Context-Dependent Facilitation - Group Data

  • 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)

Noise Burst

Order Sensitive Plasticity in Adult Primary Auditory Cortex

M.P. Kilgard,  M.M. Merzenich

Proceedings of the National Academy of Sciences

99: 3205-3209, 2002. download file

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

N = 13 rats, 261 sites

Schematic

Illustration

100ms

20ms


Slide23 l.jpg

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

Context-Dependent Facilitation - Group Data

  • 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)

Low Tone

(5 kHz)

Order Sensitive Plasticity in Adult Primary Auditory Cortex

M.P. Kilgard,  M.M. Merzenich

Proceedings of the National Academy of Sciences

99: 3205-3209, 2002. download file

N = 13 rats, 261 sites

Schematic

Illustration


Slide24 l.jpg

Context-Dependent Facilitation - Group Data

  • 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.

High Tone

(12 kHz)

Order Sensitive Plasticity in Adult Primary Auditory Cortex

M.P. Kilgard,  M.M. Merzenich

Proceedings of the National Academy of Sciences

99: 3205-3209, 2002. download file

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

N = 13 rats, 261 sites

Schematic

Illustration

100ms

20ms


Slide25 l.jpg

Add first

distractor (CS-1)

Add second distractor

(CS-2)

Add third distractor

(CS-3)

Target stimulus

(CS+)

Task

None

None

None

A) Sequence detection

H L N

None

None

B) Frequency

discrimination

L L L

H H H

C) Triplet distractor-

High first

Map

Auditory Cortex

Frequency (kHz)

H L N

H H H

L L L

N N N

D) Sequence element

discrimination

L

N

H L N

H

E) Triplet distractor-

Noise first

H L N

N N N

L L L

H H H

None

None

F) Reverse Order

N L H

H L N

Time (ms)

Time (months)

Operant Training






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kHz

‘SASH’ Group - Spectrotemporal discharge patterns of A1 neurons to ‘sash’ vocalization (n= 5 rats)


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16kHz @50dB:

35 %  1.9

55 %  5.3

(p<0.0005)


Sensory experience controls l.jpg
Sensory Experience Controls:

  • Response Strength

  • Cortical Topography

  • Receptive Field Size

  • Maximum Following Rate

  • Synchronization

  • Spectrotemporal Selectivity


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Activity from a single A1 neuron recorded in an awake rat

in response to normal and enhanced human speech sounds


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External World

-Sensory Input

Neural

Activity

- Internal

Representation

Behavioral

Relevance

Plasticity Rules

- Educated Guess

Neural

Plasticity

- Learning and

Memory

Behavioral

Change


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Acknowledgements:

Training Experiments - Navzer Engineer Amanda Puckett Crystal Novitski Enrichment Experiments - Navzer Engineer Cherie Percaccio Receptive Field Plasticity - Pritesh Pandya Synchrony Experiments - Jessica VazquezFM Experiments - Raluca Moucha Speech Experiments - Pritesh Pandya

and

and

National Institute for Deafness

and Other Communicative Disorders


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