audition_2011 - Bi 150 Nov. 4, 2011 Ralph Adolphs Auditory...

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Unformatted text preview: Bi 150 Nov. 4, 2011 Ralph Adolphs Auditory System 1 Anatomy of the auditory system -peripheral -central Language Model systems 2 Extensive processing BEFORE cortex Processing streams Topographic maps Distortion/magnification Perception is inferential Perception makes comparisons 3 4 4 WHAT IS HEARING? “To know what is where by listening” 5 Human listeners can: --accurately judge the location of a sound and can tell the difference between sounds separated by a few degrees --discriminate between two frequencies separated by 1-2 Hz over a range of nearly 10 Octaves --discriminate between sounds with intensity differences of 1-2 dB over a range of 10^8 6 7 8 Peripheral auditory system: --external and middle ears and auditory nerve Central auditory system: brainstem, midbrain, and forebrain levels 9 10 11 12 13 14 The Traveling Wave Based on the properties of the basilar membrane, high frequency sounds localize to the cochlea base and low frequency sounds to the cochlea apex. 15 16 Fibers in the 8th Nerve - 95% from inner hair cells -~5% from outer hair cells - Olivocochlear bundle 17 18 19 20 21 22 23 RA VA Apical surface CA I RS C S VB Apical RB LB C Basolateral surface CB Basolateral D Sum We ana fluorescen cence sign stimulatio electrical Both resp C). In th labeled ce higher fre from both played res The sp striking e pixels tha random p pixels fea frequency delineated plitude, w voltage os low signal 24 the spars 0.20 0.24 20 60 100 Frequency (Hz) 20 140 60 100 Frequency (Hz) B 140 % 0.3 0.2 Peak ∆ F/F 0.1 0.0 −0.1 −0.2 C 25 Hz 50 Hz 75 Hz 100 Hz 150 Hz 3 2 Phase (rad) 1 0 −1 −2 −3 spatial distribution of resonance-related fluorescence signals. (A) A fluorescence image shows hair cells stained with a voltage-sensit ar macula. The cells are most clearly distinguished as hair cells by their brightly stained mechanosensory hair bundles. (Scale bar resented with the same field of view.) (B) Images of the peak relative fluorescence changes (ΔF/F ) for the indicated stimulus fre cells. The scale bar is shown at the right. (C ) Hair cells are readily apparent in images showing the phase of the fluorescence respon es fit. The pixels with phases between −π/8 and π/8 are colored dark blue to visually threshold the images; the color axis wraps aroun requency of stimulation, the phase information was used to generate an image that displays, for every pixel, the SD of the phase v ighboring pixels. The fraction of pixels with a spatial variance of less than π/5 is plotted with the SEM as a function of stimulus frequ 100 nM iberiotoxin shifted the relation between stimulus frequency and pixel conglomeration to lower frequencies. requencies. To identify the portions of the macula d by these populations, we created binary images in ls were assigned a value of 1 if their phase lay within range. Highlighting pixels that had phases between −0.5 rad clearly delineated hair cells (Fig. 3B). Furthese highlighted regions appeared to be confined to the difference between the log-likelihoods of bimodal odal models was plotted as a function of stimulus a bimodal model was highly 108:1651 Fisher et al., PNAS (2011)preferable at 25 and 50 Hz At higher frequencies the log-likelihood difference de matically, falling below 3 in some experiments. This a fectively captured the evolution of bimodality (Fig.25 A 3 26 27 28 29 30 31 Neural code: -Rate -Timing -Place 32 33 34 MNTB – Medial Nucleus of the Trapezoid Body - Inhibitory projections to the LSO 35 36 37 Primary Auditory Cortex BA 41, 42 Insula (not part of Temporal Lobe) 38 The Auditory Cortex 39 40 argeting the Anterior FMRI Voice Cluster for Electrophysiological Recordings l structural magnetic resonance imaging (MRI) of the liquid-filled recording chamber (white bar above brain, with vertical white atemporal plane [STP] below the lateral sulcus [LS]). Brainsight and stereotaxic coordinates guided electrode placement to the ante ) voxels (red) with a strong preference for MVocs. ice from (A), including the separately localized auditory fields (black outlines); see [7, 43]. Anteroposterior (AP) and mediolateral (M for the fMRI (left) and the electrophysiological recording sites (right). The stereotaxic coordinates used the Frankfurt-zero stand fined as the midpoint of the interaural line and the infraorbital plane. Perrodin et al., Current Biol (2011) 21: 1408 lary voice cell (SUA) and multiunit activity (MUA) exhibiting preferential responses to MVocs, including voice-selectivity index (VS tal Procedures; Figure 3). 41 42 43 3 Model systems 44 45 46 47 48 49 50 51 52 53 54 ...
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This note was uploaded on 01/03/2012 for the course BI 150 taught by Professor Kennedy,m during the Fall '08 term at Caltech.

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