Processing in The Cochlear Nucleus Alan R. Palmer Medical Research Council Institute of Hearing Research University Park Nottingham NG7 2RD, UK The Auditory Nervous System Cortex Cortex MGB Medial Geniculate Body Excitatory GABAergic IC Inferior Colliculus Glycinergic DNLL Nuclei of the Lateral Lemniscus Lateral Lemniscus Cochlear Nucleus DCN PVCN MSO Lateral Superior Olive AVCN Medial Superior Olive Cochlea MNTB Medial Nucleus of the Trapezoid Body Superior Olive The cochlear nucleus is the site of termination of fibres of the auditory nerve Cochlear Nucleus Auditory Nerve Cochlea 1 Frequency Tonotopicity Basilar membrane Inner hair cell Auditory nerve Fibre To the brain Each auditory-nerve fibre responds only to a narrow range of frequencies Tuning curve Action potential Evans 1975 2 Palmer and Evans 1975 There are many overlapping single-fibre tuning curves in the auditory nerve Audiogram Palmer and Evans 1975 Tonotopic Organisation Lorente - 1933 3 Tonotopic Organisation Base Anterior Cochlea Characteristic Basilar Membrane Frequency Hair Cells Auditory Nerve Apex Cochlear Nucleus Spiral Ganglion Posterior Tonotopic projection of auditory-nerve fibers into the cochlear nucleus Ryugo and Parks, 2003 The cochlear nucleus: the first auditory nucleus in the CNS Best frequency Position along electrode track (mm) Evans 1975 4 stellate (DCN) Inhibitory Synapse Excitatory Synapse DAS to inferior colliculus cartwheel fusiform SUPERIOR OLIVARY giant COMPLEX INFERIOR COLLICULUS granule vertical vertical OCB AANN to CN & IC via TB golgi DORSAL ? COLUMN NUCLEUS ? VESTIBULAR to PPO NERVE to VNLL IAS to IC? to VNLL to MSO to DMPO, PPO MNTB, LNTB from DLPO via TB PRI PRI-N CHOP-S ON-C spherical bushy globular bushy multipolar multipolar octopus via TB to reticular pontine formation and deep SC (perhaps via collaterals to COCHLEAR NUCLEUS root neurone contralateral VNLL) ARP (after Meddis, Shackleton and Hewitt) II I Auditory Nerve Physiological Classification of Cochlear Nucleus Neurones 5 LATERAL INHIBITION IN THE DORSAL COCHLEAR NUCLEUS 120 110 100 90 80 vel (~dB SPL) (~dBvel e 70 Tone L Tone Inhibitory side band 60 50 40 Palmer 1977 Excitation Inhibition Excitation Excitation Inhibition Excitation Excitation Inhibition Stabler 1991 Inhibition Inhibition Inhibition Stabler 1991 6 Sound Level Auditory Nerve minimum thresholds Kiang 1964 7 Saturated rate Dynamic range Threshold Spontaneous rate Galambos and Davis 1943 Low threshold Guinea pig High SR At each frequency, auditory nerve fibres differ in their spontaneous rate, input/output function and dynamic range - High threshold these covary. Low SR Winter and Palmer Cat Sachs and Abbas 1974 8 Cochlear nucleus responses Stabler 1991 Young Timing Peri Stimulus Time Histograms 9 When a novel stimulus occurs within a frequency channel the discharge rate is immediately increased and then falls (adapts) over a few tens of milliseconds Kiang et al. 1965 Winter and Palmer 10 Dorsal Lesion DCN AVCN Lesion PVCN Posterior Anterior 80 Pauser AN 64 Ventral 150 48 120 Pri 32 er bin 90 Fusiform 16 0 60 0 50 100 30 Globular bushy Spikes p Stellate 0 0 50 100 Octopus Spherical bushy Stellate 200 120 Chop-S Chop-T 160 96 120 72 140 230 240 180 80 48 Pri-N On On On 112 184 C 192 L 144 I 40 24 84 Auditory 138 144 108 0 0 Nerve 0 50 100 0 50 100 56 92 96 72 28 46 48 36 0 0 0 0 0 50 100 0 50 100 0 50 100 0 50 100 Time in ms Temporal Responses of the Principal Neurones of the Cochlear Nucleus to pure tones Types of neurones in the cochlear nucleus 11 Osen 1969 PARALLEL PROCESSING OF INFORMATION IN THE COCHLEAR NUCLEUS To medial superior olive: information about sound To inferior colliculus: information about pinna localisation using timing (and possibly time coding of speech) sound transformations To lateral superior olive: information about sound localisation using interaural intensity To medial nucleus of the trapezoid body: information Either commisural or to inferior colliculus about sound localisation using interaural intensity information about sound level and voice pitch To inferior colliculus: information about complex sounds (possibly place coding of speech) Input from cochlear nerve Bushy Cells Lorente de Nó 12 The discharges of cochlear nerve fibres to lowlow-- frequency sounds are not random; they occur at particular times (phase locking). Evans (1975) Alt Tab Enhancement of synchronization in Globular Bushy Cells Joris et al 1994 13 Enhancement of synchronization in Spherical Bushy Cells Joris and Smith 2008 PARALLEL PROCESSING OF INFORMATION IN THE COCHLEAR NUCLEUS To medial superior olive: information about sound To inferior colliculus: information about pinna localisation using timing (and possibly time coding of speech) sound transformations To lateral superior olive: information about sound localisation using interaural intensity To medial nucleus of the trapezoid body: information Either commisural or to inferior colliculus about sound localisation using interaural intensity information about sound level and voice pitch To inferior colliculus: information about complex sounds (possibly place coding of speech) Input from cochlear nerve Type T Multipolar Cells Lorente de Nó 14 BF Tones 160 140 120 +50 dB 100 10.0 80 9.0 Spikes/bin 60 8.0 7.0 40 6.0 20 5.0 4.0 0 0 102030405060708090100110 3.0 2.0 Post Stimulus Onset Time (ms) 1.0 160 0.0 140 120 +20 dB 100 80 ikes/bin p S 60 40 20 11.77 kHz Chop-T 0 0 102030405060708090100110 BF Tones Noise Post Stimulus Onset Time (ms) 7 7 7 7 6 6 6 6 5 5 5 5 4 4 4 4 3 3 3 3 Spikes/Stimulus Spikes/Stimulus 2 2 Spikes/Stimulus 2 2 Spikes/Stimulus 1 1 1 1 0 0 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Level (dB) Level (dB) 26810 Transient Chopper Unit BF 11.77 kHz 26810 BF Tones 160 140 120 +50 dB 100 80 Spikes/bin 60 > 10.0 9.0 - 10.0 40 8.0 - 9.0 20 7.0 - 8.0 6.0 - 7.0 0 5.0 - 6.0 0 102030405060708090100110 4.0 - 5.0 Post Stimulus Onset Time (ms) 3.0 - 4.0 2.0 - 3.0 1.0 - 2.0 0.0 - 1.0 120 100 +20 dB 80 60 Spikes/bin 40 BF Tones Noise 20 14 14 12 12 0 0 102030405060708090100110 12 12 10 10 10 10 Post Stimulus Onset Time (ms) 8 8 8 8 6 6 6 6 4 4 Spikes/Stimulus Spikes/Stimulus 4 4 Spikes/Stimulus Spikes/Stimulus 2 2 2 2 Chop-S 19.6 kHz 0 0 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Level (dB) Level (dB) 21201 15 Generation of vowel sounds At low sound levels steady-state vowels are well represented in the mean discharge rate of the population of auditory nerve fibres. Sachs and Young, 1979 At higher sound levels the representation of the formant frequencies becomes less distinct. Sachs, Young and Colleagues 16 Theoretical computations, based on optimally weighting * the different spontaneous * rate popu lations, rev eal that mean rate alone may contain sufficient information even at high sound levels. * Delgutte, 1996 Selective listening Lai, Winslow and Sachs, 1994 Two populations of cochlear nucleus stellate cells retain vooeowel forma atnt information in their discharge rate at high sound levels Blackburn and Sachs, 1990 17 PARALLEL PROCESSING OF INFORMATION IN THE COCHLEAR NUCLEUS To medial superior olive: information about sound To inferior colliculus: information about pinna localisation using timing (and possibly time coding of speech) sound transformations To lateral superior olive: information about sound localisation using interaural intensity To medial nucleus of the trapezoid body: information Either commisural or to inferior colliculus about sound localisation using interaural intensity information about sound level and voice pitch To inferior colliculus: information about complex sounds (possibly place coding of speech) Input from cochlear nerve Type D Multipolar Cells (commisurals) D-stellate cells in the VCN Cant and Gaston - 1982 Oertel’s Group - 1990 Physiological Responses before injection BF Tones Noise 160 100 140 120 +50 dB 80 100 40 dB 60 80 Spikes/bin 60 40 Spikes/bin 10.0 40 20 9.0 20 8.0 0 7.0 0 0 102030405060708090100110 0 102030405060708090100110 6.0 Post Stimulus Onset Time (ms) 5.0 Post Stimulus Onset Time (ms) 4.0 3.0 100 70 2.0 60 1.0 80 0.0 50 20 dB 60 +20 dB 40 pikes/bin 40 pikes/bin 30 S S 20 20 10 0 0 0 102030405060708090100110 0 102030405060708090100110 Post Stimulus Onset Time (ms) Post Stimulus Onset Time (ms) BF Tones Noise 2.5 2.5 5 5 2.0 2.0 4 4 1.5 1.5 3 3 1.0 1.0 2 2 Spikes/Stimulus Spikes/Stimulus Spikes/Stimulus Spikes/Stimulus 0.5 0.5 1 1 0.0 0.0 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Level (dB) Level (dB) Onset-C Unit BF 6.29 kHz 28204 18 Physiological Responses after injection BF Tones 120 Noise 100 100 80 80 +50 dB 40 dB 60 60 Spikes/bin 40 40 Spikes/bin 10.0 20 20 9.0 8.0 0 0 102030405060708090100110 0 7.0 Post Stimulus Onset Time (ms) 0 102030405060708090100110 6.0 Post Stimulus Onset Time (ms) 5.0 4.0 3.0 2.0 160 120 1.0 140 100 0.0 120 20 dB n 80 100 +20 dB 80 60 pikes/bi pikes/bin S 60 S 40 40 20 20 0 0 0 102030405060708090100110 0 102030405060708090100110 Post Stimulus Onset Time (ms) Post Stimulus Onset Time (ms) BF Tones Noise 4 4 5 5 4 4 3 3 3 3 2 2 2 2 Spikes/Stimulus Spikes/Stimulus Spikes/Stimulus Spikes/Stimulus 1 1 1 1 0 0 0 0 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Level (dB) Level (dB) Onset-C Unit BF 6.29 kHz 28204 21208 Onset-C Unit BF 6.29 kHz 28204 19 Onset-C Unit BF 6.29 kHz 28204 Onset unit Chopper unit Primarylike unit Cochlear nerve fibre Kim and Leonard, 1988 Kim and Leonard, 1988 20 Octopus Cells Octopus Cells Oertel et al 2000 Octopus Cells Oertel et al 2000 21 PARALLEL