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
16
Q
KNUDSEN (2002)
A
- auditory cue values & locations in space
- precise prey localisation requires both ears
- sound waveform in right ear = delayed & attenuated relative to left ear
- correspondence of interaural timing dif (ITD) & interaural lvl dif (ILD) values w/locations in space for 6kHz sound
- spatial pattern changes for other frequencies
17
Q
OPTIC TECTUM IN BIRDS
A
- located in midbrain
- sensory info conveyed through midbrain to thalamus & further to cerebrum
- auditory midbrain = located on inner side of optic tectum (MLD aka. mesencephalicus lateralis dorsalis)
18
Q
AUDITORY PATHWAY
A
CN: cochlear nucleus
SO: superior olive
LLD: lateral lemniscus/dorsal nucleus
LLI: lateral lemniscus/intermediate nucleus
LLV: lateral lemniscus/ventral nucleus
MLd: dorsal lateral nucleus of mesencephalon
HVC: hgh vocal centre
NCM: caudal medial nidopallium
Nif: interfacial nucleus of nidopallium
RA: robust nucleus of arcopallium
E: entopallium
OB: olfactory bulb
CSt: caudal striatum
19
Q
CARR & KONISHI (1988)
A
- measuring interaural time dif (ITD) in cochlear nucleus (CN)
- axonal delay lines for time measurement in owl’s brainstem
- Jeffress model = sound location computed from difs in delay/intensity between 2 ears
- study confirmed basic premises with work on barn owls
20
Q
PARALLEL PROCESSING OF TIME (ITD) & INTENSITY (ILD)
A
- sensory neurons code both arrival time & intensity of particular sound frequency:
1. coding of sound as spikes in sensory neurons (inner ear)
2. separation of time/intensity data (magnocellular/angular nucleus)
3. map of ITDs (laminar nucleus)
4. map of ILDs (anterior/posterior lateral lemniscus aka. lateral lemniscus/hindbrain)
5. convergency of time/intesity pathways (auditory midbrain)
6. formation of auditory space map (external nucleus of MLD)
21
Q
LOCATION OF SOUND SOURCES
A
- mapped in 2 dimensions on MLD (midbrain & optic tectum)
- spatial reconstruction of auditory space in front of owl (L/R = azimuth degrees; +/- = elevation degrees) from ITD/ILD coding pathways converging in MLD
- inner part of auditory region neurons = organised in tonotopical layers (mapping of interneurons according to frequency tuning); outer part = interneurons tuned to 6-8kHz aka. highest sensitivity range
22
Q
GROTHE, PECKA & MCALPINE (2010)
A
- spatial mapping = projected to cortical areas aka:
1. auditory cortex
2. medial geniculate
3. inferior colliculus
4. cochlear nucleus
5. superior olivary nucleus
6. brainstem
7. cochlea
23
Q
JARVIS (2019)
A
- basic auditory pathway comparison between birds & mammals
BOTH
hair cells -> cochlear ganglion -> cochlea nuclei -> lemniscal nuclei …
BIRDS
… MLd -> ovoidalis -> L2 in caudomedial pallium -> L3/L1 -> NCM & CM -> Ai & CSt
MAMMALS
… interior colliculus -> medial geniculate -> layer 4 cortex in caudolateral pallium -> layers 2/3 -> layers 5/6 & CSt
24
Q
SUMMARY (1)
A
- sensory systems = much in common BUT alos important difs depending on physical nature of sensory info/prevalence/variation/distribution in natural environment
- sensory info has dif sources in environment & spatio-temporal characteristics = integral
- sensory systems evolved to preserve (ie. retina) or enable recovery (ie. cochlea) spatial aspects when info = captured by sensory receptors located either in 1 (ie. elaborate sensory organs)/various body parts; provides brain w/egocentric spatial reference framework anchoring other allocentric frameworks where they might be needed for dif beh execution
25
Q
SUMMARY (2)
A
- we find organised feature/action maps of specialised neurons across sensory organs/dif brain areas
- in sensory systems (where they preserve spatial info as it reaches retina of eye) such organisation = retinotopy
- where mapping = organised along spectral content (wavelength) of sounds = tonotopy
- parallel pathways = frequently found across otherwise sequentially-organised hierarchical pathways/networks in brain
- sensory pathways = well studied & understood aka. good egs for such brain organisation
