Term Definition
Lecture 10
Sound Physically, variations in air pressure through time.
Stridulation The act of producing sound by rubbing together certain body parts. (Wings in Crickets
and Legs/Wing in Grasshoppers)
CPG Neural network responsible for the production oforganized, rhythmically correct
(Central Pattern Generator) patterns of activity without any reference to the external environment
Ex: Cricket signing, mammalian breathing, mollusc swimming.
Fixed Action Patterns CPG output.
Command Neuron Neuron that can turn on the CPG, may be group of neurons.
Phonotaxis Locomotion (of a receiver) towards or away from a sound source.
Scolopidium Basic multicellular structure for hearing, one component is a sensory neuron.
Fundamental basis for all insect ears.
Sensory Neuron Neuron responsible for converting various external stimuli that come from the
environment into corresponding internal stimuli.
Interneuron Forms connections between other neurons.
AN1 Responds to cricket sounds (Lower frequencies), come closer!
AN2 Bat detecting neuron in crickets (Higher frequencies), run away!
ON1 – Omega Neuron 1 Responsible for inhibition of ANs in other ear, allows the cricket to better track direction
of sound.
Binaural contrast The difference in the activity of the two sides ofthe nervous system.
Contralateral inhibition Process by which some neurons inhibit contralateral neurons to enhance binaural
contrast. Used as a tool for localization of soundamong other processes.
Contralateral Belonging to or occurring on opposite sides of the body.
Ipsilateral Belonging to or occurring on the same side of the body.
Binaural Cues Cues for sound localization:
Interaural Intensity Difference (IID)
Interaural Time Difference (ITD)
Spiracles Openings on the surface of some animals that usuallylead to respiratory systems.
Lecture 11
Parasitic fly ear Eardrums: Prosternal tympanal membraneand Cuticular intertympanal bridge
Scolopidia are attached to eardrums.
Air-filled cavity lies behind tympanal membrane.
Bulla acoustica: Sensory neurons and scollopidia which detect ear drum vibrations
Tuning curves Depict the threshold of a given frequency requiredto excite neurons. The threshold is
the minimum sound needed.
Phase difference Sound starts at a different time
Amplitude difference Sound at a different loudness
Response latency Time between arrival of sound and response of neuron. Latency changes with stimulus
intensity. Neurons in different ears will fire at different latencies since they experience
different intensities.
Temporal pattern Rhythm of song.
Chordotonal Organ Stretch/Vibration receptor. Present in hearing andnon-hearing flies.
Satellite Behavior Flatwing (non-signing) male crickets stay close to signing malesto intercept females. Lecture 12
Amplitude Modulation Rate of amplitude change,rate at which song is produced, follows a sinusoidal wave
pattern.
Frog auditory system - Hair cells detect sound.
- Auditory afferents transmit information from haircells to CNS through auditory nerve.
- Torus semicircularis in CNS computes sound. (Analog of inferior colliculus in lower vertebrates)
AM tuning Neurons in semicircularis respond selectively to different AM rates
Frogs will have a larger number of neurons tuned totheir species AM frequency
AM reject Respond to wide variety of AM frequencies EXCEPT some
AM high pass Respond only to high AM frequencies
AM low pass Respond only to low AM frequencies
Counting Neurons Neurons in Torus semicircularis that require a minimum number of pulses at the correct
AM rate to fire.
Synaptic EPSP summation Successive EPSPs will sum until they reach a threshold for action potential
Synaptic facilitation The amplitude of successive synaptic potentials will increase.
Arises due to increased presynaptic Ca2+ concentration leading to a greater release of
neurotransmitter-containing synaptic vesicles.
Helps overcome inhibition.
Rate dependent, depends on timing of successive synaptic potentials. Pulses too rapid
may produce anti-facilitation.
Rate dependent selectivity Some neurons are selective for a specific pulse rate (AM frequency).
Pulse rate too high: Lack of facilitation. Too low:EPSPs will not summate.
AN4 neuron Selects against one-legged grasshoppers.
Song gaps produce IPSPs which inhibit EPSPs as wellas prevent facilitation. No firing,
females respond less to gap songs.
Lecture 13
Sensory maps Stimulated location in the brain is related to thelocation in space where the stimuli can
be found.
Somatotopic map Mechanoreceptors located in specific regionsof the skin will activate neurons in specific
regions of the brain
Retinotopic map Pattern of light on the retina is reflected in theactivity of neurons in the visual cortex
Place code Place in the brain will code for the place of the stimuli (Labelled line coding)
Topographic map for sound High Frequency Sounds activate hair cells at the base of cochlea, relay to posterior cells.
frequency Low Frequency Sounds activate hair cells at the apex of cochlea, relay to anterior cells.
Azimuth Left/Right
Elevation Up/Down
Facial Rough Acts as external ear in owls to collect channel sound into the ear canals.
Inferior Colliculus (ICx) In CNS, processes sound.
Auditory Fovea Allows for increased sound localization resolutionin front of the owl.
Nucleus magnocellularis Sound timing
Nucleus angularis Sound intensity
Nucleus laminaris Part of timing pathway, coincidence detector that uses delay lines to amplify interaural
time difference Lecture 14
Computational Sensory Location in space is computed via interaural time difference and interaural intensity
Map difference.
Somatosensory Map Maps a place on the sensory surface to a place on the brain.
ICC Inferior Colliculus Central Nucleus. Time and intensity combined into sound frequency
bands.
ICX Inferior Colliculus External Nucleus. Frequency channels mapped to a place map.
Optic Tectum/Superior Optic Tectum (birds) or Superior colliculus (mammals) receives visual imput from retina
colliculus
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