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PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION

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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PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION

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  1. PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION Mike KilgardUniversity of Texas Dallas

  2. PERCEPTUAL LEARNING AND CORTICAL SELF-ORGANIZATION What aspects of experience guide learning and plasticity ?

  3. 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

  4. Open Questions • Time Course • Role of Exercise • Role of Behavioral Context • Role of Neuromodulators • Cellular Mechanism • Role of Attention

  5. Environmental Enrichment RedGroup Enriched Blue Enriched 20±10 vs. 75±20μV81±19 vs. 37±20 μV 22 rats total

  6. 2X Plasticity Index 1X Auditory Exposure NB Lesion Enriched  Sham Standard  NB Lesion Standard  Sham Enriched  Standard Social  Enriched  Exercise  12 rats per group

  7. Open Questions • Time Course • Role of Exercise • Role of Social Interactions • Role of Acetylcholine • Cellular Mechanism • Role of Attention

  8. Action potentials also adapt more readily in enriched rats compared with standard rats

  9. Open Questions • Time Course • Role of Exercise • Role of Behavioral Context • Role of Acetylcholine • Possible Cellular Mechanism • Role of Attention

  10. 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

  11. LEARNING MOTIVATION

  12. PLASTICITY? MOTIVATION

  13. 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

  14. 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

  15. 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

  16. Project Summary

  17. Group # Frequency Discrimination HLN vs. HHH, LLL, NNN HLN vs. H, L, N HLN vs. NNN, LLL, HHH HLN vs. Reverse HLN Detection

  18. 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

  19. External World -Sensory Input Neural Activity - Internal Representation Behavioral Relevance Neural Plasticity - Learning and Memory

  20. 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

  21. External World -Sensory Input Neural Activity - Internal Representation Behavioral Relevance Plasticity Rules - Educated Guess Neural Plasticity - Learning and Memory Behavioral Change

  22. Best Frequency Science, 1998

  23. Tone Frequency - kHz Frequency-Specific Map Plasticity N = 20 rats; 1,060 A1 sites

  24. N = 15 rats, 720 sites Nature Neuroscience, 1998

  25. Temporal Plasticity is Influenced by Carrier Frequency N = 13 rats, 687 sites Journal of Neurophysiology, 2001

  26. Frequency Bandwidth Plasticity N = 52 rats; 2,616 sites Stimulus Paired with NB Activation Determines Degree and Direction of Receptive Field Plasticity

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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 *

  32. 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

  33. Sash

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

  35. Sash

  36. Tone Frequency (kHz) 16kHz @50dB: 35 %  1.9 55 %  5.3 (p<0.0005)

  37. Example Speech Stream Frequency  Time 

  38. Sash

  39. Spectrotemporal Sequences High Tone (12 kHz) Low Tone (5 kHz) Noise Burst 100ms 20ms Frequency  Time 

  40. 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

  41. 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)

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