Similarities & Differences Between Senses Flashcards
1
Q
SCHNUPP & CARR (2009); LADICH & SCHULZ-MIRBACH (2016)
A
- tympanic ears evolved eat least 5 times in vertebrate line
- bony fish ears contain sensory maculae that respond to underwater sound in directional fashion; during transition from water-land, tympanic middle ears capable of receiving airborne sound evolved separately
2
Q
MAMMALIAN EAR STRUCTURE
A
- sound arrives at tympanum; amplified in middle ear
- cochlea (inner ear) contains auditory receptor cells
1. external ear (pinna)
2. middle ear = ossicles; tympanic membrane (eardrum)
3. inner ear = oval window; round window; vestibulocochlear nerve (VIII)
4. cochlea = scala vestibuli (vestibular canal); scala media (middle canal); scala tympani (tympanic canal); oval/round window; VIII
3
Q
TONOPIC ARRANGEMENT OF HAIR CELLS
A
- aka. unrolling of cochlea
- relative amplitude of movement
- high frequencies displace basilar membrane in cochlea base
- low frequencies displace basilar membrane in apex of cochlea
4
Q
BASILAR MEMBRANE
A
- location defines which hair cells (auditory receptor cells) respond to dif sound frequencies
- cross section of Organ of Corti (aka. inner ear) = ca 20k hair cells along basilar membrane
- inner hair cells = 95% of afferent projections
- tallest stereocilia in contact w/tectorial membrane
5
Q
FETTIPLACE & HACKNEY (2006)
A
- stereocilia displaced; K+ channels stretch open; influx of K+ into hair cell
- depolarisation = receptor potential
- opening of Ca2+ channels
- influx of Ca2+ triggers neurotransmitter release to first-order auditory interneuron
6
Q
MANLEY (2000)
A
- highly schematic representation of amniote phylogenetic tree over 400 million years to illustrate approximate time of origin of particular features of auditory systems
- mammals = IHC/OHC (inner/outer hair cells); lizards = high/low frequency hair cells; birds/crocs = THC/SHC (tall/short hair cells)
THC/SHC & IHC/OHC PARALLELS - THCs/IHCs less specialised; receive strong afferent innervation
- OHC innervated by relatively few efferent fibers (=5%); SHC receive no afferent innervation at all
7
Q
WHY/HOW DO VISION VS HEARING DIFFER?
A
PHOTORECEPTORS
- axon terminals
- axon
- accessory structure = light-sensitive receptor molecules in membrane
INNER HAIR CELLS
- accessory structure = stereocilia w/ion-channels in membrane
- no axon/axon terminals
BOTH
- cell body w/nucleus (w/DNA)
8
Q
KONISHI (1973)
A
- sound = movement of air particles set in motion by vibrating structure
- wave characteristics of sound = alternate waves of compression/rarefaction of air; molecules move back & forth from regions of high pressure to low
- measures of sound = frequency (reciprocal of wavelength)/amplitude
- most birds hear up to 5-6kHz; barn owl = exceptional high-frequency hearing w/characteristic frequencies of 9-10kHz
- more than half of auditory neurons = sensitive in 5-10kHz range
9
Q
HEFFNER & HEFFNER (2007)
A
- audiograms = measured behaviourally; threshold for tone when correctly selected = >50%
- SPL = sound pressure level (set at 0 for 1kHz)
10
Q
DENT (2017)
A
- psychoacoustics = psychophysics subfield
- audiograms = most common assessment of animal hearing
- measurement of detection thresholds = stimuli varied in frequency/intensity played back to animal; if it responds in majority of trials correctly, stimulus = above threshold
- ie. budgies learn to peck key to start variable waiting interval; trained w/rewards/range of loud signals to respond correctly; during testing, other signal variations = interspersed; hearing = right key; if not = withhold
11
Q
MANN ET AL. (2007)
A
- electrophysiology = AEP measurements as non-invasive method for studying hearing functions
- AEP = auditory evoked potentials to determine sensitivity threshold for dif sound frequencies
- faster; no need to train animal to auditory stimuli; audiograms generated from AEPs instead of ratios of correct beh responses
- hearing in 8 Canadian freshwater fish = best in fish w/connection between inner ear/swim bladder
- dif impacts of anthropogenic noise pollution
12
Q
SUMMARY
A
- light/sound propagate as waves that differ in frequency/intensity; light = absorbed by photoreceptors as quanta; sound vibrates internal structures of ear
- spatial relations of simuli in outer world = coded through retinotopic mapping in visual pathways; spatial relations in hearing pathways = largely lost; to use sound for accurate sound source location, these need to be reconstructed in brain
- audiograms demonstrate tuning & sensitivity ranges; allow comparisons between species to determine how hearing can be adapted to dif tasks/needs
13
Q
RESEARCH IN BIRDS: INTRO
A
- research in birds contributed to fundamental demonstration of neural mechanisms relevant to human hearing
- auditory pathways have parallel/serial connections similar to vision; tonotopic maps result from arrangements of sensory interneurons in cochlea aka. important binaural comparisons & reconstruction of spatial locations relative to body
14
Q
HILL ET AL. (2010)
A
- owl moves its head to face visual/sound target
- movement in space can be represented by angular deviation in 2 directions:
1. AZIMUTH (horizontal)
2. ELEVATION (vertical)
15
Q
KNUDSEN, BLASDEL & KONISHI (1979)
A
- how do owls localise sound sources?
- search coil on top of owl’s head lies at intersection of horizontal/vertical magnetic fields; movememnt induces current in search coil
- first viewing direction = fixated w/sound from zeroing speaker
- head movement towards sound from target speaker = measured; accuracy determined
- head flick delay = 100ms BUT sounds of 75ms also elicit flick (open-loop condition)
- localisation accuracy = function of position of target speaker
- target speaker in front = error < 2 degrees
