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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

Sensory Experience and Cortical Plasticity

Michael P. Kilgard

University of Texas at Dallas

slide3

Environmental

Enrichment

RedGroup Enriched

Blue Enriched

20±10 vs. 75±20μV81±19 vs. 37±20 μV

22 rats total

slide4

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

slide5

High

Low

Cochlea

Cortex

slide6

High

Low

Cochlea

Cortex

Cortical Map Plasticity

slide9

Best Frequency

Nucleus Basalis Activity Enables Cortical Map Reorganization

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

slide10

Tone Frequency - kHz

Nucleus Basalis Stimulation Generates Frequency-Specific Map Plasticity

N = 20 rats; 1,060 A1 sites

slide12

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

slide16

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

slide17

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

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

slide19

How do neural networks learn to represent complex sounds?

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

  • Spectrotemporal Sequences
slide20

Paired w/ NB stimulation

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

}

Unpaired background sounds

slide21

Context-Dependent Facilitation

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

0 100 200 300 400ms

Number of Spikes

slide22

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

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

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

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

slide31

kHz

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

slide32

16kHz @50dB:

35 %  1.9

55 %  5.3

(p<0.0005)

sensory experience controls
Sensory Experience Controls:
  • Response Strength
  • Cortical Topography
  • Receptive Field Size
  • Maximum Following Rate
  • Synchronization
  • Spectrotemporal Selectivity
slide34

Activity from a single A1 neuron recorded in an awake rat

in response to normal and enhanced human speech sounds

slide35

External World

-Sensory Input

Neural

Activity

- Internal

Representation

Behavioral

Relevance

Plasticity Rules

- Educated Guess

Neural

Plasticity

- Learning and

Memory

Behavioral

Change

slide36

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