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Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
Anesthetized Microelectrode Mapping
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Anesthetized Microelectrode Mapping

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  • This is what we’re here to talk about.
    Before we get started, let’s think about what it is like to be a brain.
  • <number>
    FOR MAP FIGURE, EXPORTED MATLAB FIG FILE AS A TIFF (NO COMPRESSION) AND INSERTED PICTURE INTO PPT. THEN CHANGED SCALE TO 80% TO FIT SLIDE.
    Figure 3. Representative map of best frequency (top), peak latency (middle), and bandwidth 30 dB above threshold (bottom) in A1 and PAF from one animal. Each polygon represents one microelectrode penetration. The number within each polygon indicates the value for each respective response parameter. In the top panel, color represents each site’s best frequency in kilohertz. In this example, note the orderly progression of best frequency in A1 while there is a breakdown in the tonotopy in PAF. In the middle panel, color represents the peak latency of each site derived from the tuning curve PSTH. The substantially longer response latency of PAF neurons was one of the criteria used to confirm the A1-PAF border. In the bottom plot, color represents the bandwidth 30 dB above threshold. The considerably wider excitatory receptive field size of PAF sites is an additional criterion that can be used to distinguish A1 from PAF sites. The dark black line bisecting the polygons in all of the tessellated maps indicates the separation between A1 and PAF sites. The line length on the direction marker shows the scale (125 µm).
    ******
    Color Example of Representative TC and PSTH for A1 and PAF
    Figure 1. Representative tuning curves and post stimulus time histograms (PSTH) from a primary auditory cortex (A1) and posterior auditory field (PAF) site. For each tuning curve, the length of each line segment indicates the number of spikes evoked by each tone. Best frequency (BF) is the frequency that elicits a consistent neural response at the lowest intensity level, (i.e. neural threshold). Bandwidth (in octaves) is the range of frequencies the neurons are responsive to at the specified intensity above threshold, expressed in units of octaves. PSTHs for both the A1 and PAF example are shown below each respective tuning curve. The relevant features derived from each PSTH are labeled (onset latency, peak latency, and end of peak latency).
    ******
    Figure 10. The mean repetition rate transfer function for tones and noise in A1 and PAF sites. In the top panel, the number of evoked spikes per tone at each repetition rate (15 rates) is plotted with standard error of the mean. In the bottom panel, the number of evoked spikes per noiseburst at each repetition rate (5 rates) is plotted with standard error of the mean. The maximum cortical following rate evoked by a train of tones reliably fell off at a repetition rate of ~10 Hz for A1 neurons (as in Kilgard & Merzenich, 1999). In A1, this maximum rate is similar for a modulated series of broadband sounds. PAF sites exhibited a larger degree of adaptation to repetitive inputs (both tones and noisebursts). A consequence of this increased adaptation was a lower maximum following rate compared to A1. Only sites with best frequencies between 2 and 16 kHz were used for this analysis. The mean repetition rate transfer function for A1 (n=142 sites) and PAF (n=86) sites was collected from 9 animals.
  • Transcript

    • 1. Michael P. Kilgard Sensory Experience and Cortical Plasticity University of Texas at Dallas
    • 2. 20±10 vs. 75±20 μV 81±19 vs. 37±20 μV 0 50 100 150 200 250 Week 1 Amplitude(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
    • 3. • 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 32 0 20 40 60 80 Frequency (kHz) Intensity(dBSPL) A. 1 2 4 8 16 32 0 20 40 60 80 Frequency (kHz) Intensity(dBSPL) B. 0 10 20 30 40 0 50 100 C. Time (ms) Spikes/s 1 2 4 8 16 32 0 20 40 60 80 Frequency (kHz) Intensity(dBSPL) A. 1 2 4 8 16 32 0 20 40 60 80 Frequency (kHz) Intensity(dBSPL) B. 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.
    • 4. High Low Cochlea Cortex
    • 5. High Low Cochlea Cortex Cortical Map Plasticity
    • 6. High-density microelectrode mapping technique
    • 7. Best Frequency Nucleus Basalis Activity Enables Cortical Map Reorganization M.P. Kilgard, M.M. Merzenich, Science 279(5357): 1714-1718, 1998. download file
    • 8. Tone Frequency - kHz Nucleus Basalis Stimulation Generates Frequency-Specific Map Plasticity N = 20 rats; 1,060 A1 sites
    • 9. Differences between A1 and Posterior Auditory Field – submitted
    • 10. 0 20 40 2 4 8 16 32 10 30 50 70 Intensity(dB) -20 -10 0 10 20 2 4 8 16 32 10 30 50 70 Difference in PAF Percent after 19 kHz Paired Intensity(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
    • 11. Temporal Processing Typical Response of A1 Neurons to Tone Trains
    • 12. • After Pairing NB Stimulation with 15 Hz Tone Trains
    • 13. • After Pairing NB Stimulation with 5 Hz Tone Trains
    • 14. N = 15 rats, 720 sites 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
    • 15. Stimulus Paired with NB Activation Determines Degree and Direction of Receptive Field Plasticity Frequency Bandwidth Plasticity N = 52 rats; 2,616 sites
    • 16. Frequency Bandwidth is Shaped by Spatial and Temporal Stimulus Features Modulation Rate (pps) 0 5 10 15 ToneProbability 15%50%100% Spatial Variability Leads to Smaller RF’s Temporal Modulation Leads to Larger 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
    • 17. How do neural networks learn to represent complex sounds? • Spectrotemporal Sequences 100ms 20ms High Tone (12 kHz) Low Tone (5 kHz) Noise Burst
    • 18. Paired w/ NB stimulation 100ms 20ms High Tone (12 kHz) Low Tone (5 kHz) Noise Burst Unpaired background sounds }
    • 19. Context-Dependent Facilitation 100ms 20ms High Tone (12 kHz) Low Tone (5 kHz) Noise Burst NumberofSpikes 0 100 200 300 400ms
    • 20. • 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 Cortex M.P. Kilgard, M.M. Merzenich Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file Schematic Illustration
    • 21. • 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 Cortex M.P. Kilgard, M.M. Merzenich Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file Schematic Illustration
    • 22. • 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 Cortex M.P. Kilgard, M.M. Merzenich Proceedings of the National Academy of Sciences 99: 3205-3209, 2002. download file Schematic Illustration
    • 23. 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 Frequency(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
    • 24. Discrimination Performance
    • 25. Differential Plasticity Effects
    • 26. How do cortical neurons learn to represent speech sounds?
    • 27. Sash
    • 28. ‘SASH’ Group - Spectrotemporal discharge patterns of A1 neurons to ‘sash’ vocalization (n= 5 rats) kHz
    • 29. 16kHz @50dB: 35 % ± 1.9 55 % ± 5.3 (p<0.0005)
    • 30. Sensory Experience Controls: • Response Strength • Cortical Topography • Receptive Field Size • Maximum Following Rate • Synchronization • Spectrotemporal Selectivity
    • 31. 0 50 100 150 Spike Rate(Hz) 0 50 100 150 Spike Rate(Hz) 0 50 100 150 Spike Rate(Hz) Frequency (kHz) 5 10 20 25 Frequency (kHz) 5 10 20 25 Frequency (kHz) 5 10 20 25 0 50 100 150 0 50 100 150 0 50 100 150 5 10 20 25 5 10 20 25 5 10 20 25 A) 'back' E) 'back' - modified B) 'pack' F) 'pack' - modified C) 'sash' G) 'sash' - modified 50 100 150 200 250 300 350 50 100 150 Time (ms) Spike Rate(Hz) pack back a sh D) Neural responses to normal speech 50 100 150 200 250 300 350 50 100 150 Time (ms) ba p a s a ck ck sh 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
    • 32. Behavioral Relevance Neural Activity - Internal Representation External World -Sensory Input Neural Plasticity - Learning and Memory Plasticity Rules - Educated Guess Behavioral Change
    • 33. 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

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