Neurobiology of … Introduction

UCHC-INCYL-USAL 2019 David Pérez González Hearing . Far-range sense: like vision . Omnidirectional

Essential for communication of animal and men Sound: quick variations of pressure

Compressed air

Rarefied air pressure Air

One Distance cycle Sound and Sound propagation

Wavelength

Sound Amplitude pressure

Wavelength λ C = λ * ν (~ 330m/s) ν = Frequency = number of cycles/s (Hz) Properties of a sine wave

• Frequency: Cycles per second, or Hertz (Hz). • Phase: angle (degrees). • Amplitude: decibels (dB) Sound frequency and intensity

Low frequency High frequency Air Air pressure

Low intensity High intensity Air Air pressure

Distance Distance Sound pressure level

200,000,000 • The difference in amplitudes between the quietest and loudest sounds we can hear is massive • Normal air pressure: 100k Pascals. • We can hear a .000000001% change in pressure. 20 Sound pressure level 140 • The decibel scale: the logarithm of a ratio (relative to 20µPa):

20log 10(p/ 20µPa)

20µPa 0dB SPL 200µPa 20dB SPL 2000 µPa 40dB SPL etc. 0 Decibel Scale

• Relative • Logarithmic  I   p  dB SPL = log10 10  = log20 10   I0   p0 

-5 • Reference pressure p0 = 2x10 Pa (hearing threshold 1kHz) Auditory thresholds in humans

(dB) Threshold of pain

Speech Sound intensity

Absolute threshold

Sound frequency (kHz) Mammalian audiograms Pure tones and complex sounds

aaa Zeit The auditory information arriving at the is a mixture of all the sounds in the environment. The individual sound waves are combined into a single, complex sound wave. The peripheral Function of the Middle

Transformation:

Pressure p Area: Al : As = 17 : 1

Lever deflexion d : lm : li = 1,3 : 1 combined: d / p = 22 : 1

p / d = z * ω = Impedance * Frequency The (Bony Labyrinth)

Vestibular Nerve

Sacculus Travelling wave in the Cochlea Travelling wave in the Cochlea

Low Frequency Travelling wave in the Cochlea

High Frequency Frequency Analysis in the Cochlea Pelicula cochlea The cochlea

30 Detail of the organ of Corti:

IHC OHC Hair cells: transduction

QUIETSOUND depolarization Hair cell depolarization

• The movement of the cilia produces changes on the membrane potential Inner and outer hair cells

Inner hair cell Outer hair cells

Stimulus propagation Amplification Effect of sound on a outer hair cell ¿What is the role of outer hair cells? Hearing loss Hair cell innervation The human auditory brain

Kiang and Peake (1988)

The is the first step into the central auditory system

Cochlear nuclei

Auditory nerve

Cochlea

Cytoarchitecture of the cochlear nuclei. Golgi staining Cytoarchitecture of the cochlear nuclei. Golgi staining The cochlear nuclei: parallel processing pathways Mechanisms for in the horizontal plane (azimuth) Time and intensity differences for localizing a sound source Interaural time differences (ITDs) Interaural level differences (ILDs) Mechanisms for sound localization in the vertical plane (elevation) Structure of DC the CN • Central nucleus (CN) LC • Dorsal cortex (DC) • Lateral cortex (LC) FUNCTIONAL PROPERTIES OF THE INFERIOR COLLICULUS FUNCTIONAL PROPERTIES OF THE INFERIOR COLLICULUS Inputs to the Inferior Colliculus Inputs from Cochlear Nucleus

INFERIOR IC COLLICULUS

DLL DLL

VLL VLL

Monaural inputs to IC DCN DCN Monaural inputs to SOC and IC VCN VCN

LSO MSO MSO LSO CONTRA IPSI Inputs from SOC

INFERIOR IC COLLICULUS

DLL DLL

VLL VLL ITD ONLYITD DCN ILD DCN - ITD

VCN ILD-ITD VCN

LSO MSO MSO LSO CONTRA IPSI Inputs from

INFERIOR IC COLLICULUS

DLL ILD-ITD DLL

VLL VLL Monaural

DCN DCN

VCN VCN

LSO MSO MSO LSO CONTRA IPSI CONTRA Frequency Band Lamina IPSI INFERIOR COLLICULUS

DLL

VLL

Monaural DCN

VCN

LSO MSO Binaural MSO LSO

Inputs Create Functional From Loftus et al (2010) J Neurosci • Zones in the IC 30(40):13396 –13408 The organisation and function of the auditory From Bear Connors and Paradiso: Neuroscience, Exploring the brain The human auditory system

Auditory cortex

Medial geniculate body (Thalamus) Inferior Dorsal cochlear colliculus nucleus Lateral lemniscus

(Adapted from Bear et al) Cochlea Superior olive Spiral Medial geniculate body

D Thalamic reticular nucleus M L

V

MGD IC (dorsal cortex) IC (external cortex) MGM VNLL MGV Po DNLL Cochlear nucleus IC (central) Circuits for auditory fear conditioning

Auditory cortex

Amygdala

Central MGM MGV Lateral

Defence responses

Behaviour Hypothalamus / pituitary

Autonomic nervous Conditioned stimulus -tone system The auditory cortex Location of auditory cortex in

Planum Temporale

Primary auditory cortex: Heschl’s gyrus and layers of rat auditory cortex Neurons and layers of rat auditory cortex The auditory cortex in mouse and cat

Multiple tonotopic maps in the cortex

Rostral Caudal Petkov et al 2006 Plasticity in the auditory cortex Plasticity in auditory cortex following stimulation of nucleus basalis in rat Reorganisation of the frequency map in rat A1 following nucleus basalis stimulation

Kilgard et al 1997 Science 279 1715