Hearing Science Unit 6

Front 1

increase speed, automatic, simultaneous, increase/decrease

Back 1

Subcortical pathways along the auditory nerve pathway contribute to ____________ _________ of the signal, ________________ & _____________ processing, and ________/__________ level of arousal of an organism.

Front 2

spectral (frequency), temporal (timing), interaural differences, localization (spatial coordinates)

Back 2

The CNS (central nervous system) acts to buffer and further process the ___________ and ____________ patterns of signals received from the periphery & acts to process ______________ ______________ which contributes to ______________ of sound.

Front 3

F (does not represent analog signal of sound... encoding process is too complex)

Back 3

T/F: Cochlear mechanics and neurons encode complex binaural stimuli that provides a straightforward representation of the original sound.

Front 4

brainstem, cortex

Back 4

When the auditory nerve signal leaves the organ of corti, it follows subcortical pathways through the ___________ prior to entering the _________ where auditory processing occurs.

Front 5

decompressing, dynamic range, gain, discrimination

Back 5

The brain stem provides an efficient and sophisticated means of _____________________ the peripherally coded signals, presumably for an optimal balance of excellent ____________ ________________, ________ control, and ________________.

Front 6

frequency, pitch, time and space, cues

Back 6

Cortical function is seen to culminate in various processes from lower level functions to provide more than basic signal detection and discrimination. This includes, ultimately, ______________ and __________ perception, percepts of ________ and _______, and cognitive-level use of the various encoded ______ for sound. Cortical processing is essential in audition in all its dimensions.

Front 7

greater diameter, myelin sheath

Back 7

Spike action potentials are propagated along the axon at a rate enhanced by __________ ___________ and a ____________ __________.

Front 8

bipolar, IHC, OHC

Back 8

Primary auditory afferent neurons are largely myelinated ____________ cells whose dendrites and axons form a pathway from the ___________ to the brain stem. Innervation of the _____ is more remarkable for the high density of efferent endings.

Front 9

crossed, 5, variations

Back 9

Although the central auditory pathways are predominantly _____________ and involve nominally neurons of ______ (number) orders among major nuclei on the way to the primary auditory cortex, ___________ are common.

Front 10

trapezoid, higher

Back 10

While the majority of ascending fibers decussate (cross over) at the level of the _________ body, crossovers may occur at ______ levels.

Front 11

bypass

Back 11

The order of neurons is somewhat variable, as some ascending fibers, for example, may _________ a nucleus.

Front 12

Contralateral (cross over centrally), ipsilateral

Back 12

Although the "majority" pathways representing R and L ears are ___________, there are substantial "minority" pathways of neurons whose axons course _________. (NOTE: this is with re: to sides of brain that the pathways are running).

Front 13

ABR, EEG, populations of neurons

Back 13

Noninvasive exploration of auditory function- to distinguish among levels of function, if not localized regions of activity in the brain-may be accomplished using scalp-recorded sound-evoked electrical potentials ( _______ ) and magnetic resonance imagery (______), but such methods yield results representative of _____________________.

Front 14

ongoing (continuous), stimulus-related

Back 14

Delicate (but invasive) recordings may be made of spike action potentials and analyzed in various ways to represent ___________ or ___________ ___________ discharges of individual neurons along the auditory pathways.

Front 15

nonlinear cochlear amplifier, traveling wave

Back 15

Frequency tuning curves reflect events well back in the cochlea, including effects of the _________ ________ __________, on one hand, and the spread of excitation of the _________ ________, on the other.

Front 16

intensity, timing

Back 16

Spike rate reflects both _________ and __________ information.

Front 17

adaptation

Back 17

_____________ and other temporal features provide further nuances that add to the neural code.

Front 18

organ of corti, tonotopic

Back 18

The frequency-to-place transformation effected by traveling waves in the cochlea, together with orderly wiring of the _______________ to nuclei along the ascending auditory pathways (cochleotopic organization) translates into ____________ organization of the auditory pathways.

Front 19

primary auditory (sprial ganglion), sharpening

Back 19

The ability to discriminate one frequency of sound from another is most likely determined by the tuning functions of the _________ __________ neurons (at least for frequencies above approximately 2 kHz), since increased ___________ in the tuning curves is rarely observed at higher levels of the system.

Front 20

subcortical auditory centers

Back 20

In the case of intensity discrimination, the mechanisms involved are less obvious, and it is not clear yet whether the limits of resolution are essentially set at subcortical levels. Still, intensity differences should be detectable by neurons at __________ _________ ___________, at least for low-level stimuli, by virtue of peripheral intensity encoding alone.

Front 21

multiple, volley, 2000

Back 21

Temporal encoding of frequency is demonstrated robustly by auditory neurons, despite the limited discharge rate of individual neurons, thanks to ___________ afferent neurons innervating each IHC and the __________ principle. Efficient phase locking of neural discharges to stimulus frequency occurs at least to __________ Hz.

Front 22

characteristic

Back 22

As fundamental as the neural code for intensity may appear- the density of neuron discharges- a comprehensive story is still awaited. What is clear is that the brain cannot merely listen to the most sensitive neurons at their ____________ frequencies.

Front 23

periphery, preserve, enrich

Back 23

The demands on the brain for speech processing alone point to the need for processing of the incoming signals from the _________, thanks to overlapping activity in time and space in the cochlea- namely, high-speed multi-line information handling to ________ and _________ features of the sound stimulus.

Front 24

differences, SOC, intensity

Back 24

Precise temporal encoding peripherally also is essential to the processing of interaural _________, first at the level of the _________. The brain stem pathways are engineered to extract efficiently such binaural stimulus features (including interaural _________ differences), the foundation of sound localization.

Front 25

descending, middle-ear-muscle, efferent

Back 25

The central auditory system also has __________ pathways by which to feed back signals to more or less control its own input; this is done to a limited extent via a combination of __________ and ________ reflex arcs mediated at the level of the SOC.

Front 26

percepts, cognitive, integration

Back 26

The primary auditory cortex appears classically as the top of the ascending auditory pathways but also is a portal to the processes at the top of the CNS, which ultimately provides _________, ________ processing, and __________ of auditory information to support behavior in general.

Front 27

columnar

Back 27

Although tonotopic organization is manifested at the top, the 6 major layers of the cortex provide another organizational dimension by which information is sorted for further cortical processing-________ organization.

Front 28

time, frequency, duration, sound space

Back 28

The primary auditory cortex appears to be essential to the processing of ______ and _______ patterns, __________, and _______ _________.

Front 29

cortex, corpus callosum, hemispheric (cerebral)

Back 29

The extensive bilateral processing of auditory information culminates in the _______, where the 2 hemispheres are connected by the _____________. Consequently, it is difficult to imagine that one hemisphere could keep a secret from the other, although _____________ dominance appears to prevail for certain auditory and other functions.

Front 30

dendrites, primary

Back 30

An excitatory post-synaptic potential evoked by a sound stimulus is generated in _____________ of _____________ auditory neurons.

Front 31

propagated, synapses

Back 31

DELAYS in signals getting from the hearing organ to the cortex are most attributable to these facts:

Front 32

interval

Back 32

__________ histograms of spike action potential can tell us something about the level of spontaneous activity of the neuron when quiet (not stimulated).

Front 33

characteristic

Back 33

The "audiogram" of single primary neuron- that is SPL at threshold vs. frequency--shows sharp tuning around one frequency called the __________ frequency.

Front 34

auditory-evoked response (ABR)

Back 34

An electrical signal or analysis that represents the action of many neurons at multiple levels of the central auditory pathways is the ______________.

Front 35

primary, basilar membrane

Back 35

The place code for frequency in the auditory system derives from the origin of innervation of __________ neurons along the _________.

Front 36

identical, onset, onset, rapid adaptation

Back 36

In contrast to primary auditory neurons, the pattern of discharge of neurons in the brain stem (as evidenced by their post-stimulus-time histogram) exhibit: _______ patterns of discharge, responses only to stimulus ________, responses with pulsating level of activity in addition to strong ______ response, & responses at onset with _______ __________, then increased response as stimulus continues.

Front 37

slightly above or below

Back 37

Two tone suppression occurs when a second tone is presented at a frequency _______________ the CF of a neuron.

Front 38

rate, density, increased, cortex

Back 38

Intensity is encoded by: discharge _____ of individual neurons, __________ of discharge of groups of neurons, ___________ synchrony of discharges, & neurons in the _______ tuned according to intensity.

Front 39

localization

Back 39

The head, medial superior olive, trapezoid body, and temporal encoding all contribute to sound ________________.

Front 40

SOC

Back 40

The first major center of BINAURAL information processing in the brain stem is the _________.

Front 41

phase, maximal

Back 41

Characteristic delay refers to a binaural effect demonstrated in the laboratory, recording from neurons in the auditory brain-stem pathways wherein a certain _________ difference between ears of stimulation generates a _________ spike rate.

Front 42

OHCs, IHCs

Back 42

The OCB (olivocochlear bundles of neurons) form descending pathways to directly innervate _______ & form pathways terminating on afferent fibers innervating ___________.

Front 43

primary auditory cortices

Back 43

If an individual has difficulty distinguishing duration, frequency, and localization they may have something wrong with their _________ _________ ___________.

Front 44

duration

Back 44

Cortical-level function is MOST needed for discriminating among sounds of different _____________.

Front 45

relative

Back 45

The ___________ refractory period determines the maximum spike rate of a neuron.

Front 46

absolute

Back 46

The __________ refractory period occurs during the major phase of the spike and results in the inability of a cell body to discharge again regardless of the amount of stimulation it receives.

Front 47

relative

Back 47

During the _________ refractory period the neuron can be depolarized again with greater than normal stimulation even through the membrane potential never fully reached it's resting potential following the first firing.

Front 48

axon

Back 48

Action potentials are transmitted (or propagated) within the nervous system by way of what part of the neuron?

Front 49

8th nerve, DVCN (dorsal ventral cochlear nucleus), IC (inferior colliculus), primary auditory cortex

Back 49

Cochleotopic (or tonotopic) organizational schemes are portrayed at the following levels of the auditory pathways system: _____________, ______________, _____________, & _______________________.

Front 50

period histogram

Back 50

That frequency can indeed by encoded in the timing pattern of neural discharges in the auditory system is best demonstrated by which analysis of single unit neural activity at the level of the 8th nerve?

Front 51

narrow band-pass filters

Back 51

Returning to the place code mechanism, we learned that the mechanical events of the cochlea effectively "label" each neuron by frequency. The net result is that, from the CNS looking out into the environment via the hearing organ, it is as if the brain sees the world of sound through a bank of ______________________ tuned to different frequencies along the length of the hearing organ.

Front 52

cell body

Back 52

An important part of the neuron, although important to its well-being and not primarily involved in the excitation and/or transmissions of neural signals is the _____________.

Front 53

terminal bouton

Back 53

This part of the cell contains subcellular mechanisms, which produce and control release of chemical neurotransmitters.

Front 54

low frequency (long wavelength)

Back 54

For relatively long-lasting or essentially continuous tones, the timing-and thus phase synchrony-of neural discharges is very important for certain binaural processing, namely for which type of sounds?

Front 55

duration

Back 55

Going back to the single neuron and the threshold concept at the cellular level: 1 parameter of the stimulus that is critical for the effective stimulation of an action potential is the stimulus magnitude (intensity). The other critical parameter is the ____________ of the stimulus. The 2 together have affects reflecting the overall energy of the stimulus.

Front 56

CN 2nd order, SOC 3rd order, IC 4th order

Back 56

Primary (1st order) neurons of the ascending auditory pathway, by convention, are those of the 8th nerve, namely the sensory or 1st neuron along this "chain of command" of the pathway. What are the other levels of the pathway and "order" of neurons associated with each?

Front 57

PST

Back 57

The ______________ histogram reveals the relationship between the discharge pattern and the onset/offset of the stimulus and time course of activity between.