Sensing the Evnironment Flashcards
What are the types of electric sense?
Passive - Detects external fields. Electroreceptive.
Active - Generates its own electric field and detects changes. Electroreceptive and electronergic.
What are the types of passive electric sense?
Animate - Detection of bioelectricity generated by other organisms.
Inanimate - Detecton of naturally occurring electric fields in the environment.
Give examples of naturally occuring electric fields.
Electrochemical
Geomagnetic
Which organisms exhibit passive electric sense?
Sharks Skates Rays Catfish Electric fish types
What are the types of active electric sense?
Animate - Sensing other members of the species, predators and prey.
Inanimate - sensing anything with an electrical conductivity different to that of water.
Which organisms exhibit active electric sense?
Weakly electric fish Some strongly electric fish: Electric eel Electric ray Electric catfish
What types of vertebrates is electroreception present in?
Jawless fish Cartilaginous fish Bony fish Amphibians Mammals
Which jawless fish use electroreception?
Lampreys
Which cartilaginous fish use electroreception?
Sharks
Skates
Rays
Which bony fish use electroreception?
Sturgeons
Catfish
Which amphibians use electroreception?
Salamanders
Caecilians
Which mammal uses electroreception?
Platypus
Describe the evolutionary history of electroreception.
Evolved by common ancestors of fish
Lost by many bony fish
Re-evolved separately (together with electrogenicity) by mormyriform and gymnotiform fish.
Re-evolved by monotremes - platypus.
What are the 5 groups of electroceptive/genic fish? Give an example.
Mormyriforms - Elephantnose fish Gymnotiform fish - Electric eel. Knifefish Malapteruridae - Electric catfish Uranoscopidae - Stargazers Torpediniformes - Electric ray
What % of fish are electroreceptive?
25%
What % of fish are electrogenic?
0.7%
What are the electrogenic properties of strongly electric fish?
Live mainly above equator.
500-600V discharge.
What are the electrogenic properties of weakly electric fish?
Live mainly below equator.
10V discharge.
What is the discharge of strongly electric fish used for?
Stunning prey
What is the discharge of weakly electric fish used for?
Detection of perturbations in own electric field.
Used for location of prey/obstacles and communication.
What are the 2 types of discharge of weakly electric fish and which fish use them?
Wave - Most american knifefish
Pulse - Most african knifefish
What are electrocytes?
Modified muscle cells of the electric organ of electric fish.
How are electrocytes modified?
Negative on the inside.
Describe the stages of electric organ discharge (EOD).
Impulse arriving along the motor neuron causes release of ACh onto one side of the cell.
ACh binds to ion channels in the membrane.
Channels open causing depolarisation and flow of current.
Electrocytes arranged in battery-like series
Current flows from +ve to -ve side causing a synchronoud discharge.
What does the waveform of the EOD depend on? Give examples.
Innervation of electrocytes:
Monopolar - Strongl electric fish
Bipolar - Weakly electric fish
Why do electrocytes not contract?
Contraction decoupled from excitation.
What are electroplaques?
Stacks of electrocytes
How do fish ensure current flows through water and not bodily fluids?
Insulate body parts from the current.
Compare the location of electroplaques in fish.
WEF - By tail muscles
SEF - By branchial muscles
How is EOD controlled?
Pacemaker nucleus in the brain.
What are the types of electroreceptors?
Ampullary
Tuberous
Compare the evolutionary history of both types of electroreceptors.
Ampullary - evolved in ancestral fish. Now in all electrosensitive fish and elasmobranchs.
Tuberous - Evolved in WEF. Mormyriforms and Gymnotiforms only.
Describe the structure of ampullary receptors.
Pit filled with conductive gel and an exposed sensory neuron at the bottom.
What are the properties of ampullary receptors?
Spontaneously active
Sensitive to weak electric fields of 1V in 2000km of marine water or 10km fresh water.
Detect 0-30Hz
What is the function of ampullary receptors?
Passive electrolocation.
What are the properties of tuberous receptors?
Respond to discharges of electric organs.
What is the function of tuberous receptors?
Encoding information about frequency and amplitude of electric fields.
What are the types of tuberous receptors?
Time markers
Amplitude coders
What is the function of time markers?
Detection of frequency
Passive electrolocation
How do time markers detect frequency?
1-35 receptors per neurone.
Receptors cells fire single AP per EOD
Electrical synapses connect to the neurone for fast transmission.
What is the function of amplitude coders?
Detect change in amplitude
Active electrolocation
How do amplitude coders detect amplitude?
Latency of the 1st spike encodes amplitude
Shorter latency - higher amplitude.
What are the types of amplitude coders?
A
B
What are the components of the octavo-lateral sensory system?
Electroreceptors Hearing receptors Equilibrium receptors Gravity receptors Water current receptors
What is the risk associated with EOD in pulse fish? How is it avoided?
Interference with own EOD.
Corollary discharge inhibition of timing marker.
What is the risk associated with EOD in wave fish? How is it avoided?
Risk of interference from other conspecifics.
Jamming avoidance response.:
Frequencies of the two fish summate to create a wave within the wave.
Fish with higher frequency wave will shift its frequency even higher
Fish with lower frequency will shift its frequency lower.
What monitors the frequency of fish’s EOD?
External receptors
How is own EOD distinguished from others’?
Receptors will distinguish own EOD because the strength of the signal will be equal around the circumference of the fish
EOD of other fish will have different strengths around the circumference and the angle of the signal will be different too.
What is the role of tuberous receptors in electrocommunication?
Collection of information about surrounding EODs.
Why can’t ampullary receptors collect EOD info?
Ampullary receptors tuned to DC which is not in EOD’s range.
Tubular receptors are tuned to AC which is in EOD range.
How do time markers detect self and neighbouring EOD?
Fire action potentials when the amplitude of the incoming EOD goes from +ve to -ve.
Signal is synapsed onto the hindbrain’s somatotopic maps.
Signal summates onto spherical cells.
Frequency info passed onto Laminae of Torus semicircularis.
How do amplitude coders detect self and neighbouring EOD?
Fire action potentials in proportional frequency to the amplitude of the EOD.
Signal synapsed onto somatotopic maps of the hindbrain.
Excitation of basilar pyramidal cells
Inhibition of non-basilar pyramidal cells
Amplitude info passed onto laminae of torus semicircularis.
Describe the signalling pathways from torus semicircularis.
Signal passed onto nucleus electrosensorius.
Stimulatory signal activates PPnG in the prepacemaker nucleus which passes the signal onto pacemaker cells in the pacemaker nucleus.
PAcemaker cells transmit the signal to relay cells which activate the electric organ.
An inhibitory signal inhibits the SPPn in the pre-pacemaker nucleus.
Signal not passed onto relay cells of the pacemaker nucleus.
Relay cells reduce EOD frequency from the electric organ.
Describe the pathway of corollary discharge inhibition.
Motor output creates a copy which is used to inhibit the expected feedback from the action of the electric organ.
This means that the EOD inhibits knollerorganes at the same time its about to hit them.
This way fish do not detect own EOD.
How is the EOD information processed n somatotopic maps?
Electroreceptor location is represented as 4 somatotopic maps in the electrosensory lateral lobe (ELL) in the hindbrain.
1 map contains ampullary receptor projections
3 map contain tuberous receptor projections.
Receptor arrangement also preserved in the midbrain.
Which features are detected by active electrolocation?
Location Conductance Distance Capacitance Electrocommunication
How is location detected via active electrolocation?
Object within the EOD changes the current flow.
Insulators reduce current
Conductors increase current
Area of active receptor picking up the returning signal is detected in the somatotopic map and the relative position of the object can be determined.
How is electrolocation used to sense conductance of an object?
Objects distort the electric field
Conductors increase EOD amplitude
Insulators decrease EOD amplitude.
How is distance of an object determined using electrolocation?
Closer objects cause a greater change in amplitude.
Distant objects activate more receptors which means their “shadow” is more spread out.
Shadow of distant objects has less contrast because the change in amplitude that they cause is smaller.
Distance calculated slope-to-amplitude ratio.
How is electrolocation different to stereoscopic vision/auditory perception and echolocation?
Uses a single array of receptors.
No time measurements are taken.
What is capacitance and how does it compare in living organisms and inanimate objects?
Storage of charge
Living organisms have high capacitance
Inanimate objects have low capacitance.
How is capacitance detected by pulse fish?
Mormyrids use amplitude coders (mormyromast receptors) to compare responses of A and B cells to determine capacitance.
Capacitance modifies shape of EOD.
How is capacitance detected by wave fish?
Gymnotids use time markers (T-receptors) to compare timing distortions at different positions on the body.
Capacitance modifies the timing of the field relative to emission.
What is the function of electrocommunication?
Species identification
Gender identification
Courtship
Aggression
How are species identified by electrocommunication?
EOD is species-specific
May be pulse-like or wave-like
EODs of different species have different frequencies.
How is gender identified by electrocommunication?
Males and females have different frequency ranges.
How is courtship performed by electrocommunication?
Males modify their EOD waveform during courtship
Modification modulated by hormones.
How is aggression detected using electrocommunication?
Short, low frequency chirps.
Long, higher frequency chirps indicate submission.
Describe the experiments on prey detection in dogfish sharks.
1: Prey under the surface in an agar chamber
Cues: No visual; No mechanical; Displaced chemical cues via pump.
Effect: Shark attacks agar chamber
2: Inanimate shark bait in an agar chamber under the surface.
Cues: No visual; No mechanical; Displaced chemical.
Effect: Shark attacks chemical cues
3: Prey in an electrically insulated agar chamber.
Cues: No visual; No mechanical; No chemical
Effect: Shark disoriented.
4: Electrodes mimicking bioelectric signal under the surface.
Effect: Shark attacks electrodes
5: Shark bait on surface (Chemical+visual). Electrodes under the surface.
Effect: Shark attacks electrodes
How do elasmobranchs detect prey electrically?
Using passive electroreception
Pick up on faint electric fields produced by living organisms.
What is the function of ampullary receptors?
Navigation
Passive electrolocation
What is birdsong?
Vocalisation of more than one note that is used for communication.
What are the uses of birdsong?
Attracting mates
Defending territory
What are the levels of birdsong?
Phrases
Syllables
Notes
Describe the experiment conducted by Thorpe.
Isolated male chaffinches
Some were played tape recordings of chaffinch song
thers had no tutor songs
Vocalisations recorded from tutored birds showed near-identical songs
Vocalisations recorded from untutored birds showed simplified songs
If chaffinches were tutored by other species, they produce songs similar to that of tutor.
Is bird song learnt or genetically programmed?
Combination of both
What are the learning phases of birdsong in birds?
Sensory
Sensorimotor
Crystalised
Describe the sensory phase of learning birdsong.
Birds listen to tutor song
Learning affected by preference of own species and preference of a live tutor.
Live tutor more important than species.
Describe the sensorimotor stage of learning birdsong.
Subsong: Soft, variable. Rambling syllables
Plastic song: Rehearsal. Phrases become recognisable.
Describe the crystallised stage of learning birdsong.
Song has characteristic volume and duration
Song remains unchanged.
Describe the temporal spread of phases in white crowned sparrows.
Breeding season in spring
Sing in spring to attract mates.
Song of offspring crystallised by following mating season.
Describe the temporal spread of learning phases in zebrafinch.
Breed all year round.
Critical/sensory period closes after 60 days from hatching
Synsory period overlaps with sensorimotor.
Describe the temporal spread of learning phases in the canary.
Breed in spring
Can learn new songs each year.
Sensory overlaps sensorimotor.
Second sensory period starts next year and overlaps with crystalied period of the previous year.
How can the sensory phase be extended by the environment?
Costal living in crowned sparrows
Isolation from tutor in zebrafinch
Presence of a live tutor in crowned sparrow.
What are the percentages of closeness of learnt birdsong?
32% identical to tutor
18% variations
50% invented.
What happens to birdsong of birds exposed to two tutors?
Combination of the two songs in a 50/50 manner.
Why do birds overproduce syllables in plastic phase?
To segregate correct sounds
Test sounds on other birds
How are birdsongs recognised?
By differences in grammar (order of syllables), sound of notes, size of repertoire.
Describe the experiments conducted by Marler and Peters in 1977 relative to bird song recognition.
Birds reared in isolation.
2-60 day old fledglings exposed to taped song of both species.
Swamp sparrows preferred song of conspecifics.
Song sparrows copied features of foreign song 20% of the time.
Tutor audio mashed up and played back,
Swamp sparrows: recognise syllables but not syntax
Song sparrows: recognise syllables, syntax, tempo and learn foreign syllables if they’re in species-specific tempo/syntax
Describe the experiment carried out by Marler and Peters in 1977 about song of isolated birds.
Isolated birds developed simple songs with some conserved characteristics: Duration Tonality Frequency range Size of repertoire
Syllables lose complexity.
Ability to retain characteristics suggests innate template presence.
Describe the findings of Marler and Peters in deaflend birds’ song.
Cannot perform song
Means auditory feedback is needed to learn to sing.
Auditory feedback is used to match own song to template
Template is part innate/part learnt
What are the components involved in learning and production of song in zebrafinch?
Higher Vocal Centre - HVC
Robust nucleus of the Archistriatum - RA
Tracheosyringeal portion of the Hypoglossal nucleus - nXIIts
Respiratory control
Medial portion of the dorsolateral thalamus - DLM
Area X
Lateral portion of the Magnocellular nucleus of the anterior neostriatum - LMAN
What is the song production pathway?
HVc => RA => Respiratory control and nXIIts
What is the anterior forebrain pathway?
HVc => Area X => DLM => LMAN => RA
Learning pathway.
What is the syrinx?
Vocal organ of birds located at the base of the trachea.
How is sound poduced in birds?
Air comes from sacs, not lungs.
Body wall muscle expels air from sacs.
Air movement causes vibration of typeniform membranes, creating sound waves.
Internal and external syringeal muscles alter tension of the membrane which alters the frequency of vibration.
What is hypoglossal dominance in birds?
One side of the brain has more control than the other over bird song production/learning.
Lesion of the left hypoglossal nerve impairs song in most birds.
How do some birds recover from sectioning of the left hypoglossal nerve? Give examples.
Canaries and chaffinches transfer the song control to the other half of the syrinx.
Describe the lateralisation of the song-production pathway.
Lesion of the left HVc impairs singing in canaries causing them to re-learn songs in the right HVc
Deafening or lesion of both HVc prevents recovery.
How can it be proved that RA is involved in song production?
Lesion of both RA impairs song production therefore RA must be involved.
What is the function of HVc projections onto RA and Area X?
Recognition of song.
What is the function of the LMAN neuron?
Responds to own song and conspecific song.
When are RA and HVc active?
Just before and during singing.
What is the effect of artificial stimulation of HVc during singing?What does this imply?
Causes phrase advance. This implies that HVc is involved in central pattern generation.
When does the song-production pathway become functional? What are the implications of this?
During the sensorimotor phase in zebrafinch.
Suggests that it’s used for song production and not formation of a template.
When is the anterior-forebrain pathway active? What does this imply?
Active during the sensory phase which suggests that it performs a role in learning templates.
Using lesions, how can the function of the anterior-forebrain pathway be confirmed?
Lesioning LMAN in juvenile and adult birds.
Impairs singing in juveniles
No effect on adults.
Suggests that LMAN has no effect on song production but on formation.
How does the amount of singing vary in birds?
Birds of different genders and different species perform different amounts of singing.
Singing varies from season to season.
Singing amount is linked to testosterone and size of song nuclei.
What are the song nuclei?
HVc
RA
LMAN
Describe the effect of testosterone on song development.
Plasma level proportional to number of syllables.
Male canaries castrated if unable to perform song.
Describe the effect of testosterone injection on singing in female canaries and castrated swamp sparrow males.
Females sing
Castrated swamp sparrows sing.
What is the relationship between repertoir and song nuclei?
Size of repertoire proportional to size of HVc.
What is the seasonal difference of nuclei size in male canaries?
HVc 99% larger and RA 76% larger in spring compared to autumn.
What is the increase of HVc caused by?
Increase in the number of synapses.
Increase in the number of neurones being formed e.g.: neurones linking HVc and Area X during the peak of sensory phase.
When and where is the birdsong learning/forming system most plastic?
During the sensory phase, particularly in the anterior forebrain pathway.
What order do bats belong to?
Name 2 sub-orders and give an example of a bat from each.
Chiroptera.
Megachiroptera - Egyptian fruit bat
Microchiroptera - Parnell’s moustached bat
What is the bisonar?
A biological sonar.
An image forming system that uses reflected sound to form a map-like image of the surroundings in the brain.
Describe how the active sense of the bisonar works.
Animal emits pulse of sound
Sound distorted by surroundings
Sound bounces back producing an echo
Echo detected and interpreted
What is the bisonar used for?
Foraging
Navigation
Describe the discovery of Lazzarro Spallanzani and Charles Jurine regarding echolocation. Which year has the discovery been made in?
Blinded bats avoided obstacles
Bats with candlewax-clogged ears crashed into obstacles.
1794.
Describe the discovery of Donald Griffin and G.W. Pierce regarding echolocation. Which year has the discovery been made in?
Used an instrument which detected high frequency signals.
Plugging ears and taping the mouth prevented navigation
Ultrasound weakened rapidly in the atmosphere which meant it could be used for navigation and prey detection.
1938,
Describe the accuracy of echolocation in bats.
Fit through a 14cm mesh of 80 micrometer thick wire.
How is distance information perceived by bats?
By the time-delay of the echo.
How is the angular size information perceived by bats?
Amplitude/loudness of the echo.
How is the absolute size of an object perceived by bats.
By a combination of time delay and amplitude i.e. small amplitude + short delay = smaller object
small amplitude + long delay = larger object.
What are the two components of direction?
Azimuth
Elevation
How do bats detect the azimuth of an object?
Possibly intensity difference within a 60 degree cone in front.
How do bats detect the elevation of an object?
Move ears independently
Compare echo amplitude like owls
Tragus provide additional information info through complex reflections.
How do bats determine the velocity of an object e.g.: prey?
Use doppler shift analysis of echoes.
What are the two types of bat calls?
Frequency Modulated pulse
Constant Frequency pulse
What are the properties of the FM pulse?
Broadband - Sweeps high to low over a range of frequencies
Short - <5ms
Degrades quickly
What is the function of the FM pulse?
Measurement of target distance
Each frequency provides a point at which pulse-echo determnation can be carried out.
What are the properties of the CF pulse?
Long - 5-30ms
Propagates further - Energy concentrated into a single frequency.
What is the function of the CF pulse?
Measurement of object velocity
Detects insect flutter/wing beat via doppler shift analysis.
Describe the doppler shift analysis of measuring object velocity.
Speed of the object advancing towards the source of sound increases the pitch of the echo
Speed of the object retreating from the source of sound decreases the pitch of the echo.
Wing beats produce small doppler shifts as they move back and forth.
Bats can detect the presence of an insect since there are doppler shifts within the doppler shift of the moving insect itself.
Why are CF pulses used for velocity analysis?
Long - sensitive analysis within a single frequency
More energy - pulses have a greater range.
What is the acoustic fovea?
Narrow range of frequencies around the CF component of emitted call to which bats are extremely sensitive.
What is the problem of the acoustic fovea? How is it overcome?
If the object is moving away too quickly or advancing too slowly, the echo will fall outside of the fovea which means the bat will no longer be able to analyse the echo.
This problem is fixed using a doppler shift compensation mechanism which keeps echo within acoustic fovea by either lowering or heightening the call frequency.
What are the call patterns observed when the bat is approaching an object?
Decreased call duration
Increased call repetition
What are call harmonics?
Integer multiples of the fundamental frequency of the bat call. Perceived as quality of sound rather than separate notes.
Most of the call is in the 2nd/3rd harmonic.
What are harmonics used for?
Prey detection
How are CF and FM calls used in foraging?
FM used to pick prey out of the surface/clutter and in pursuit.
CF used for foraging in open space and search for wing beat.
Describe 3 peripheral mechanisms and specialisations used by bats in echolocation.
Flap-like structures within pinnae provide additional elevation info.
Enlarged ears enable detection of faint echoes
Elaborate nose enables funnelling of sound in species which call through nostrils.
Describe the directionality and funnelling during emission of a bat call.
Sound propagates as a sphere.
Funnelled into a cone by either the mouth or the nostrils depending on the species.
Width of the sound beam depends on the position of the nose leaf.
Which species use nostrils for funnelling and which use the mouth?
Mouth - Moustached bat
Nostrils - Horseshoe bat
How are vocal patterns of bat call controlled?
Motor control of breathing muscles and larynx.
What is the function of pinnae in receiving the echo?
Provide directional selectivity of frequencies of the echo.
Provide amplification of the echo.
How is the incoming echo filtered in the ear?
Outer ear - Pinnae collect and funnel the echo. Design of the pinnae dictates which frequencies are received. Eardrum vibrates at the frequency of the sound wave
Middle ear - Sound wave transmitted via ossicles from the ear drum to the inner ear.
Inner ear - Sound wave travels through an oval window to the cochlea where it acts on the hair cells which transmit the sound as electrical signals to the brain.
What are the steps of the neural pathway of echolocation?
Ear => Cochlear nucleus => Midbrain inferior colliculus => Forebrain auditory cortex
Describe the neural mechanisms involved in the transmission of sound from the ear to the cochlear nucleus.
Basilar membrane vibrates with the ear drum.
Stimulation of hair cells causes excitation of primary auditory neurons.
Signal is transduced to the CNS
What is the function of primary auditory neurons?
Encoding all aspects of sound.
How is the frequency of the sound encoded by primary auditory neurons?
Frequency is coded by the place of the neuron along the basilar membrane.
The further the hair cell, synapsed onto the neuron, is along the basilar membrane, the lower the frequency encoded by that hair cell’s neuron.
Describe the unique properties of the basilar membrane of CF bats.
Basilar membrane of CF bats is longer and thicker at the frequency of their CF call.
Describe the neural mechanisms involved in sound transmission from cochlear nucleus to the midbrain inferior colliculus?
Interneurons sensitive to specific cell-echo delays
Acoustic fovea maintained and expanded via a disproportionate number of neurons
Describe the neural mechanisms of relaying sound information from the midbrain inferior colliculus to forebrain auditory cortex.
Overrepresentation of neurones dedicated to acoustic fovea carrying the signal.
What are the three areas in the forebrain auditory cortex that are responsible for encoding echo information?
FM-FM
CF-CF
DSCF
What is the function of the FM-FM area?
Distance coding
What is the function of the CF-CF area?
Encode velocity information by representing precise doppler shifts.
What is the function of the DSCF area?
Mapping of frequency amplitude and doppler shift.
How are the parameters of sound waves mapped in the DSCF area?
Frequency encoded radially
Amplitude encoded in columns
How do bats avoud cross-interference?
Fundamental harmonics are too low to be heard by other bats
Transmitted to the inner ear of the emitting bat via skull tissue.
Why is the fundamental frequency necessary?
Necessary for comparison with echoes.
How do bas avoid self deafening?
Reduce auditory sensitivity.
How do FM species avoid self-deafening?
Contract inner ear muscles
Reduce further at the nucleus of the lateral imniscus.
