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עבוד אותות במערכת החושים סמסטר א' תש"ע http://www.eng.tau.ac.il/~mira/Senses2009 Lecture 12 Auditory Binaural Pathway Neural Auditory pathway • • • • • • • Auditory Nerve Cochlear Nucleus Medial Superior Olive Lateral Superior Olive Lateral lemniscus Inferior Colliculus Medial geniculate nucleus • Primary auditory cortex Schematic Representation of the Brainstem Auditory Pathway Brainstem MRI & fMRI Scans Axial Coronal Sagittal Auditory Pathway and Brainstem Outline Overlapped on fMRI Scans Binaural Stimulation Axial cut (6/12) -SOC Coronal cut (6/11) - AC Coronal cut (2/11) - MGB 0.025 0 Axial cut (2/12) - CN Axial cut (10/12) - LL Auditory Lateralization Cues • Interaural Time delay – The sound reaches the closest ear before the other • Interaural Level delay – The sound at the closest ear is louder LATERALIZATION Perception Stimulus R ILD L 4 3 2 1 5 6 7 8 9 R ITD R ITD=ILD=0 L L Normal Performance Histograms = number of times a subject reported perceiving a position when ITD or ILD presented Abnormal Performance Side --Oriented 9 9 9 9 8 8 8 8 7 7 7 7 6 6 6 6 5 5 5 5 4 4 4 4 3 3 3 3 2 2 2 2 1 -1 1 - 10 1 -1 0 ITD(msec) 1 position position Center-Oriented 0 ILD(dB) 10 0 ITD(msec) 1 1 - 10 0 ILD(dB) 1 0 Lesion Detection Correlation between MRI and Lateralization Normal Lateralization MS10 MS20 MS50 MS52 CVA23 Correlation between MRI and Lateralization Center-Oriented Lateralization Correlation between MRI and Lateralization Side-Oriented Lateralization Correlation between MRI and Lateralization MRI LATERALIZATION NORMAL PERFORMANCE CENTER-ORIENTED SIDE-ORIENTED NO LESIONS MS10 MS20 MS50 MS52 CVA23 TB LESIONS TB&LL LESIONS LL LESIONS CVA25 CVA36 MS3 MS22 CVA29 CVA30 CVA32 MS46 MS48 CVA37 CVA54 CVA44 MS7 MS11 MS15 CVA39 CVA43 Monaural & Binaural Activation in a Right Sagittal Section Left Ear Stimulation Right & Left Ears Stimulation Right Ear Stimulation Monaural & Binaural Activation in a Left Sagittal Section Left ear stimulation Both ears stimulation Right ear stimulation Binaural masking צליל מונוטוני ורעש מושמעים לשתי האוזניים .הרעש ממסך את הצליל. ניתן לגרום לכך ששוב נשמע את הצליל על ידי כך שניצור הפרש פאזה בין הצלילים בשתי האוזניים. צליל מונוטוני והרעש מושמעים לאוזן אחת ,קשה להבדיל את הצליל מהרעש .הרעש ממסך את הצליל. מוסיפים רק רעש לאוזן השניה –ובאורח מוזר ,ניתן שוב לזהות את הצליל על רקע הרעש. Cocktail party effect אם יש כמה מקורות קול מופרדים במרחב, קל להקשיב לקול אם הקול שאנו מעונינים בו נמצא במיקום שונה מקולות הרקע .זה נובע מכך שהצליל והממסך יוצרים קונפיגורציה אינטרנאורלית שונה מזו של הממסך בלבד. Find the minimum ITD/ILD • We will conduct an experiment to measure the minimum ILD/ITD. tRight , LRight tLeft , LLeft Minimal Audible Angle - MAA מהו ההפרש הקטן ביותר בשינוי מיקום הקול המאפשר הבחנה בשינוי זה? היכולת שלנו להבחין בהפרש במיקום מקור הקול היא טובה ביותר כשהקול מגיע מלפנים בחזית הראש .יכולת זו הולכת ופוחתת כשמקור הקול נמצא בצדי הראש או מאחור. שינויים קטנים בכיוון הקול מלפנים יוצרים הבדלים גדולים ב. ITD - Superior Olive Complex Coincidence Detection Cells • Coincidence detection (CD) is one of the common ways to describe the functionality of a single neural cell. • Correlation • There are several type of such cells: – Excitatory Inhibitory (EI) – Excitatory Excitatory (EE) – Cumulative Neural mechanisms – EE Type cells Spikes when inputs coincide. E Input E Input 1 _ I E(1)I (t ) EE (t ) EE Input 2 E E( 2)I (t ) _ I Input E max( , ) 1 r 2 r EE t 1 t t t t dt t t dt 2 t 2 1 t EE Formulation EI t (pE ) tq( I ) or t (pE ) tq( I ) 0; 0 t (pE ) T ,0 tq( I ) T NE NI i 0 j 0 P EI P(nE i ) P(nI j ) P( EI nE i, nI j ) T P(0 t (E) p t (I ) q nE i, nI j ) P(t (pE ) t nE i ) P(t tq( I ) t nI j )dt 0 T P (0 t (E) p t (I ) q t nE i, nI j ) (t ) I* (t ')dt 'dt * E 0 t t T P( EI ) exp E (t ) I (t ')dt 'dt t 0 0 E I Neural mechanisms – EI Type cells Spikes with excitatory input unless inhibited. Input E EI Input I E r t EI t E t 1 I d t EI Formulation P ( EI ) P nE 0 N P n E n 1 M n P nI m P t (pE ) tq( I ) , 0 t (pE ) t q( I ) nE n, nI m mn T P(0 t (E) p t (I ) q nE n, nI m) t * E 0 N P( EI ) e E e E 0 n! n 1 P ( EI ) e E T N n 0 n n! t dt dt * I t I e mn m n ! mn M T 0 t N I e E n 0 e E T 0 T e 0 E I 0 n! n n t E t 1 I t ' dt ' dt 0 t T n Complex Cells Input 1 ... Input 2 E N L Input M Inhibitory input CDE t t 1 j (t ')dt ' l (t ) j (t ')dt ' lI L ' L I L ' jI N jI L ' t t L' j l j IL ' N N L EI Cells Signal Separation Signal separation ability is considered as most important in tasks such as cocktail party, BMLD. Spiking rate [normalized] S+N 300 250 200 EI N |fft(response)| [normalized] 2 4 6 Time [mSec] 8 0.1 0.05 0 200 300 400 500 Frequency [Hz] 600 EE Cells spontaneous rate The spontaneous rate of cells that results from external noise reduced at higher levels ITD Mean Rate From Agmon-Snir et al.(1998), Nature 293,268-272 Model Predictions EE EIL 0.8 0.6 0.4 0.2 EIR 1 1 0.99 0.99 Normalized mean rate VS = 0.64 VS = 0.47 VS = 0.22 Normalized mean rate Normalized mean rate 1 0.98 0.97 0.96 0.95 0.94 0 -180 -90 0 IPD [ ] 90 180 0.93 0.98 0.97 0.96 0.95 0.94 -180 -90 0 IPD [ ] 90 180 0.93 -180 -90 0 IPD [ ] 90 180 ILD Mean Rate EIL EE EIR 1.2 1.2 0.8 0.6 1 Normalized mean rate Normalized mean rate 0.8 0.6 0.4 VS = 0.64 VS = 0.46 VS = 0.22 1 0.8 0.6 0.4 0.4 -10 -5 0 ILD [dB] 5 0.2 -10 10 -5 0 ILD [dB] 5 0.2 -10 10 200 -5 0 ILD [dB] Saturation Rate Tollin&Yin (2004) Data EI ipsi 1 contra 200 sec M 60 M Mean Rate [spikes/sec] Normalized mean rate 1 Theoretical Fit 150 100 50 Spontaneous Rate 0 -30 -20 -10 0 ILD [dB] 10 20 30 5 10 JND(ITD) All Information: Rate & Timing EIL 1.06 1.05 1.04 1.03 1.02 1.01 1 -180 -90 0 IPD [ ] 90 3 Normalized JND (IPD) LB 1.07 EIR 1.025 Normalized JND (IPD) LB Normalized JND (IPD) LB EE VS = 0.64 VS = 0.47 VS = 0.22 1.02 1.015 1.01 1.005 1 180 -180 -90 0 IPD [ ] 90 2.5 2 1.5 1 180 -180 -90 0 IPD [ ] 90 180 90 180 Rate Only EE EIL 10 -180 -90 0 IPD [ ] 90 180 Normalized JND (IPD) LB VS = 0.64 VS = 0.47 VS = 0.22 100 1 EIR 1000 1000 Normalized JND (IPD) LB Normalized JND (IPD) LB 1000 100 10 1 100 10 1 -180 -90 0 IPD [ ] 90 180 -180 -90 0 IPD [ ] Phase Delay in EE Cells Inputs L t S L t , exp B S L t , sin(2 ft L L f ) R t S R t , exp B S R t , sin(2 ft R R f ) 65 60 2.8 2.6 50 2.4 2.2 CRLB [ normalized] Optimal phase [ ] 55 45 40 35 2 1.8 1.6 1.4 1 2 3 4 Sin amplitude 5 6 1.2 1 -100 -50 0 Rel phase [ ] 50 100 Prediction of JND(ITD) from EE Cell N Excitatory Inputs E E N=6 EE N Excitatory Inputs N=20 Binaural EE Normalized JND (IPD) LB 1 0.95 0.9 N=6 0.85 0.8 0.75 VS = 0.64 VS = 0.47 VS = 0.22 0.7 0.65 -180 -90 0 IPD [ ] 90 180 N=20 Prediction of JND(ILD) from EI Cell 6 Mills 1 Excitatory Inputs E Level JND [dB] 5 EI E M Inhibitory Inputs 4 3 M=3 2 0 0 VS = 0.64 VS = 0.46 VS = 0.22 1.15 2 4 6 Frequency [kHz] 8 10 1.1 6 1.05 1 0.95 -10 Hershkowitz and Durlach Hershkowitz and Durlach 5 -5 0 ILD [dB] 5 10 • Rate Coding and All Information Coding provided similar results Level JND [dB] Normalized JND (ILD) LB 1 4 M=3 3 2 1 M=15 0 0 20 40 Level [dB SPL] 60 80