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PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION. Mike Kilgard University of Texas Dallas. PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION. What aspects of experience guide learning and plasticity ?. A1 Enrichment Effects - after 2 months. Enriched. Standard.

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slide1
PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION

Mike KilgardUniversity of Texas Dallas

slide2
PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION

What aspects of experience guide learning and plasticity ?

slide4
A1 Enrichment Effects - after 2 months

Enriched

Standard

  • 55% increase in response strength
    • 1.4 vs. 0.9 spikes per noise burst (p< 0.0001)
  • 22% decrease in frequency bandwidth
    • 1.8 vs. 2.2 octaves at 30dB above threshold (p< 0.0001)
  • One millisecond decrease in latency
    • 15.8 vs. 16.8 ms (p< 0.005)
  • Two decibel decrease in threshold
    • 17 vs. 19 dB ms (p< 0.01)

Stronger, Faster, More Selective,

and More Sensitive

N = 16 rats, 820 sites

Journal of Neurophysiology, 2004

slide5
Open Questions
  • Time Course
  • Role of Exercise
  • Role of Behavioral Context
  • Role of Neuromodulators
  • Cellular Mechanism
  • Role of Attention
slide6
Environmental

Enrichment

RedGroup Enriched

Blue Enriched

20±10 vs. 75±20μV81±19 vs. 37±20 μV

22 rats total

slide7
2X

Plasticity Index

1X

Auditory

Exposure

NB Lesion

Enriched 

Sham

Standard 

NB Lesion

Standard 

Sham

Enriched 

Standard

Social 

Enriched 

Exercise 

12 rats per group

slide8
Open Questions
  • Time Course
  • Role of Exercise
  • Role of Social Interactions
  • Role of Acetylcholine
  • Cellular Mechanism
  • Role of Attention
slide14
Action potentials also adapt more readily

in enriched rats compared with standard rats

slide15
Open Questions
  • Time Course
  • Role of Exercise
  • Role of Behavioral Context
  • Role of Acetylcholine
  • Possible Cellular Mechanism
  • Role of Attention
slide16
Operant Effects - after 2 months of 2 hours/day training
  • 21 % increase in response strength
    • 1.26 vs. 1.04 spikes per noise burst (p< 0.00001)
  • 13 % decrease in frequency bandwidth
    • 1.87 vs. 2.16 octaves at 40dB above threshold (p< 0.0001)
  • 1.8 millisecond decrease in minimum latency
    • 14.84 vs. 16.66 ms (p< 0.01)
  • 4.6 decibel decrease in threshold
    • 15.2 vs. 19.8 dB (p< 0.00001)

Stronger, Faster, More Selective,

and More Sensitive

N = 42 rats, 2,231 sites

slide17
LEARNING

MOTIVATION

slide18
PLASTICITY?

MOTIVATION

slide19
High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

Task Schematic

CS+

CS-’s

CS-’s

CS-’s

CS-’s

Unpaired background sounds

slide20
Sequence

Discrimination

vs. Elements

Sequence

Detection

Frequency

Discrimination

Noise

Low

High

High

Silence

Silence

Silence

HLN (CS+)

Low (CS+)

HLN (CS+)

TRAINING DAYS

TRAINING DAYS

TRAINING DAYS

Sequence

Discrimination

vs. Triplets

- High first

Sequence

Discrimination

vs. Triplets

- Noise first

Sequence Order

Discrimination

NNN

HHH

LLL

LLL

NLH

HHH

NNN

Silence

Silence

Silence

HLN (CS+)

HLN (CS+)

HLN (CS+)

TRAINING DAYS

TRAINING DAYS

TRAINING DAYS

EASY

DIFFICULT

slide21
Frequency

Discrimination

High

Silence

Low (CS+)

TRAINING DAYS

Sequence

Discrimination

vs. Triplets

- High first

Sequence

Discrimination

vs. Triplets

- Noise first

Sequence Order

Discrimination

NNN

HHH

LLL

LLL

NLH

HHH

NNN

Silence

Silence

Silence

HLN (CS+)

HLN (CS+)

HLN (CS+)

TRAINING DAYS

TRAINING DAYS

TRAINING DAYS

EASY

DIFFICULT

slide23
Group #

Frequency

Discrimination

HLN vs.

HHH, LLL, NNN

HLN vs.

H, L, N

HLN vs.

NNN, LLL, HHH

HLN vs.

Reverse

HLN Detection

slide26
Influences on Cortical Plasticity
  • Time Course ~ Weeks
  • Role of Exercise Insignificant
  • Role of Social Contact Insignificant
  • Role of Behavioral Context Important
  • Role of Acetylcholine Not Required
  • Cellular Mechanism Long-Term Potentiation?
  • Role of Task Difficulty Important
slide27
External World

-Sensory Input

Neural

Activity

- Internal

Representation

Behavioral

Relevance

Neural

Plasticity

- Learning and

Memory

slide28
Acknowledgements:

Enrichment A1 Experiments - Navzer EngineerEnrichment Evoked Potentials - Cherie Percaccio Behavioral Training - Navzer Engineer Crystal Novitski

and

National Institute for Deafness

and Other Communicative Disorders

slide29
External World

-Sensory Input

Neural

Activity

- Internal

Representation

Behavioral

Relevance

Plasticity Rules

- Educated Guess

Neural

Plasticity

- Learning and

Memory

Behavioral

Change

slide30
Best Frequency

Science, 1998

slide31
Tone Frequency - kHz

Frequency-Specific Map Plasticity

N = 20 rats; 1,060 A1 sites

slide32
N = 15 rats, 720 sites

Nature Neuroscience, 1998

slide33
Temporal Plasticity is Influenced by Carrier Frequency

N = 13 rats, 687 sites

Journal of Neurophysiology, 2001

slide34
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

Journal of Neurophysiology, 2001

slide36
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

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

N = 13 rats, 261 sites

Proceedings of the National Academy of Sciences, 2002

100ms

20ms

slide37
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)

N = 13 rats, 261 sites

Proceedings of the National Academy of Sciences, 2002

slide38
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)

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

N = 13 rats, 261 sites

Proceedings of the National Academy of Sciences, 2002

100ms

20ms

slide39
Tone Frequency (kHz)

*

40

**

* = p< 0.05

** = p< 0.01

*

**

30

Percent of Cortex Responding to 21 kHz at 40 dB

20

10

0

Naïve Control

1 Day Post

10 Day Post

20 Day Post

All Groups

*

slide40
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

slide42
kHz

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

slide44
Tone Frequency (kHz)

16kHz @50dB:

35 %  1.9

55 %  5.3

(p<0.0005)

slide46
Example Speech Stream

Frequency 

Time 

slide48
Spectrotemporal Sequences

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

Frequency 

Time 

methods
METHODS

Location of reference points used to record EEG activity prior, during and after each stimulation. This information was used to confirm the efficacy of NB activation

Stimulating Electrode Location from Bregma: 3.3 mm Lateral 2.3 mm Posterior 7.0 mm Ventral

nucleus basalis activation
NUCLEUS BASALIS ACTIVATION

EEG Desynchronization Caused by NB Stimulation

19 kHz tone @ 50dB

250 msec duration

EEG VOLTAGE (mV)

The stimulation currents levels (70-150 μAmps) were individually established to be the minimum necessary to briefly desyncronize the EEG during slow wave sleep. The stimulation consisted of a train of twenty biphasic pulses (100 Hz, 0.1 msec pulse width)

TIME (msec)

slide52
External World

-Sensory Input

NB stimulation

Neural

Activity

- Internal

Representation

Behavioral

Relevance

Neural

Plasticity

- Learning and

Memory

slide53
Paired w/ NB stimulationfor a month

High Tone

(12 kHz)

Low Tone

(5 kHz)

Noise Burst

100ms

20ms

}

Unpaired background sounds

slide54
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)
  • 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.
  • 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)

N = 13 rats, 261 sites

Proceedings of the National Academy of Sciences, 2002

slide55
N = 15 rats, 720 sites

Nature Neuroscience, 1998

fm sweep paired with nb stimulation 8 to 4 khz in 160 ms
FM Sweep paired with NB stimulation(8 to 4 kHz in 160 ms)
  • No map expansion
  • No preference for downward vs. upward FM sweeps
  • Decreased threshold by 3 dB and latency by 2 ms,and increased RF size by 0.2 octaves only in the region of the frequency map activated by sweep (p<0.01)

32

16

8

4

2

1

Frequency

NB

Stim.

Time

slide58
FM Sweeps paired with NB stimulationFive downward sweeps of one octave in 160 ms
  • No significant plasticity

32

16

8

4

2

1

Frequency

NB

Stim.

Time

slide59
Does acoustic context influence plasticity?Five downward sweeps of one octave in 160 ms plusunpaired upward (160 ms) and downward (40 or 640 ms) sweeps
  • Decreased threshold by 4dB and latency by 2ms,and increased RF size by 0.2 octaves all across map (p<0.01)
  • No preference for downward vs. upward FM sweeps
  • Preference for 160 ms long sweeps (p<0.001)

32

16

8

4

2

1

Frequency

NB

Stim.

Time

slide60
2X

Plasticity Index

1X

12 rats per group

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