Research Method in Hearing Science and Audiology Flashcards
What are the General Considerations for using animal models? (5)
- In life science, most knowledge from animal models because human research is limited by ethics
- Similar anatomy means similar physiology, Those similarities are the basis of translations (for example monkeys and humans similar)
- Similar functions are reported among species with similar anatomy/genetics
- Limitations exist: for example difficult speech research in animals
- Difficult for human-specified functions (e.g., Speech Language)
What are two types of classification of methods in neuroscience?
Anatomic/morphological methods
Functional methods
What are the characteristics of Anatomic/morphological methods?
Focus on structures from gross to fine, to molecules
What are part of Functional methods? (2)
- Behavior methods (subjective)
- Objective methods
What are studies in Behavior Methods (subjective)? (2)
observation (passive, not interference, natural, lack of control)
empirical study (stimuli-responses, designed condition)
What are studies in Objective Methods? (2)
- Evoked response (Electrophysiology/optical/magnetic responses)
- Functional imaging
What are 5 General definitions of Methods for Anatomy and Structures?
- Gross anatomy: gross structure
- Microstructures (to evaluate to macrostructures): dissection, staining, microscopy technologies
- Staining to show special materials: Histochemical staining
Immunohistochemical (IHC): against proteins w/ antibodies - 3D reconstruction
*Many different methods for structures of biomolecules (DNA, proteins, and lipids)
Which method is this?
- Dissection, staining and microscopy observation
- Golgi staining with silver nitrate
Which method is this?
Method: Tracer to track pathway
It is not easy to track the pathway if the fibers are not distributed in a laminated manner.
This tracer won’t go passed the synapse
Shows the whole structure of the particular cell
What is this method?
Study from a Dal researcher. Drosophila:
Tracer goes across the synapse in this case
Pathway tracking across synapse
What method is this?
3D reconstruction of the structure from multiple slices
What is Caplain?
Calpain is a proteinase that is activated by calcium overload in response to noise
What is occurring in this experiment?
IHC to identify special protein
Calpain increase in hair cells by noise exposure
A: control
B: shortly after noise exposure
After noise exposure: B – Activation of the protein inside the synapse
This is a good method to identify the protein standing: Making Antibody
What is the use of immunohistochemistry?
Immunohistochemistry (IHC), allows to measure protein molecules in the tissue, uses dissection with light microscopy and electron microscopy
Why would researchers care about the structural basis of biomolecules and what would be a limitation?
To see how ion channels allow certain ions to pass
Limitation: can only observe proteins that are fixed and not in living tissue
What are 2 Genetic methods of Molecular Biology?
Gene knockout/in: germ cells and conditional knockout/in somatic cells to see the function of particular genes for example
Gene therapy:
Modulation and editing
siRNA
Stem cell transplantation
The nucleobase chain forms ____________,
___________, and ________________________
The nucleobase chain forms genetic code, Ribonucleic acid, and deoxyribonucleic acid.
What are methods suitable for human subjects? (5)
Behavior studies
Evoked potential studies
Functional imaging
Neural recording during surgery
Biopsy
What are methods used on human subjects limited by?
Invasiveness
What type of human method is this?
Behavioral studies in human—example in sound source localization
Speaker can move in space, subject wears a hat with light beam and eyes are blinded. Shows ability to identify the sound location
Which method is the single most important category of functional methods in neuroscience?
Electrophysiology—single category where many different methods are part of this category
has contributed the most in the field
Explain electrophysiology in vivo: (3)
- Consideration of the size of electrodes: Gross electrode (poor spatial selectivity) vs microelectrode (multi units vs single unit)
- Near field vs far field
- Acute vs chronic
Which clamps are used in electrophysiology in vitro? (2)
Patch clamp, whole cell clamp
Explain this method:
Electrodes for recording and stimulation
(2 basic knowledge)
* At least two electrodes are needed to form a signal recording and stimulation circuit to form a loop to allow current to pass. Ex: Reference electrode + Recording electrode (are made of Conductive Material)
- Isolation is needed, only tip is exposed to tissue.
What is this method?
Combination with pharmacological method
The drug can be delivered by pressure, or by iontophoresis (electricity)
Explain this method:
Voltage clamp: One of the methods used in physiological studies, the breakthrough for action potential
Axon from Giant Squid provides the best sample for the study of voltage clamp: to study the feature of ion channels at different mem. potential
What is this method?
Patch clamp: voltage clamp on small patch
Patch is small, allow the study of ion channel properties (single ion channel if patch is really small
Functional units of neurons can be: (2)
Functional units can be single neurons and circuits
Single-neuron activities are the foundation of ____________________ and must be recorded ______________ by __________________
Single-neuron activities are the foundation of signal coding and must be recorded separately (single unit study) by microelectrodes (thin tip, high impedance and better spatial selectivity)
Give an example of the reason we would need to record the activity of a single-neuron:
E.g., To see how acoustic signals are coded in neural behavior
By rate change
By phase locking (temporal pattern)
By place, i.e. tonotopic map in auditory pathway
Single-Recording timelines in experiments can be done for: (2)
Acute and Chronic impairments
Explain single recording in acute impairment: (3)
- Recording over several hours
- Under anesthesia to make the animal stabilized
Difficulty to hold electrode in position - Suitable for microelectrode recording of single neurons
Explain single recording in chronic
impairment: (4)
- Using implanted electrodes
- Can be gross and microelectrodes
- Can be recorded from awake animals
- Long-lasting, allow more manipulation over time
Single-unit recordings can be done for two types of channels:
Single Channels
Multi-Channels
Explain Single channels in single unit recording (3):
Recording activities of one neuron at a time
Very time consuming
Can be combined with dye injection to verify neurons with certain response pattern
Explain Multi-channels in single unit recording (3):
- Recoding activities of many neurons that may be connected via circuits
- Allow exploring of neural circuits and the mechanism of signal processing
- Can be done using acute and implantable electrodes.
What changes can we see from the peripheral (low-level) to the central station (high-level cortex)? (8)
- Increased number of neurons
- Increased versatility
- Slower working speed (due to synaptic delay) slower in cortical neurons, faster in SGN
- More complicated circuits, allowing detailed processing*
- Specified processing combined with high level of integration
- More place coding
- Responses are modulated by many factors—inconsistent response to the same stimuli
- interaction with neurons in the same nucleus, other nuclei (ascending, descending, contralateral side, other modalities etc.)
What characteristics can we see in Central neurons and signal processing? (4)
Relay neurons (send a signal across distance) and interneurons (send signals locally)
Principle pathway and local circuits
Excitation and Inhibition
Membrane property variation
What can we see in the integration of Auditory Function?
- Integrate information from single-unit studies
Example in intensity coding of the auditory nerve - Longitude integration (along pathway: ascending and descending innervation)
- Transverse integration: ex: integration across different frequency channels for speech coding
- Cross-modality integration
What does research show about integration in our brain? (4)
- In research, raw data are collected from scattered sources, such as single neurons, different spots of cochlea (for basilar membrane vibration etc), and from different time points
Many examples have learnt so far for integration to better understand neuroscience.
Ex: from point test to figure out BM vibration over the whole cochlea, from ANF response to every sweep of signal to get PSTH etc.
Comparison between the integration in data collections and natural neural activities is interesting (e.g. Volley principle for phase locking by auditory system and by PSTH etc)
What is this test?
Electroencephalography: only largely synchronized brain rhythm can be demonstrated
Way before evoked potential
In EEG, the responses can be interpreted as noise which is randomized (EEG tests spontaneous brain activity)
Which technique is shown in this graph?
Evoke potential: Neuronal response to stimuli
In this graph, time delay varies with stimuli
Due to the consistency of the time lock, the EVPs can be picked up from large noise by time averaging.
Time averaging requires a digital computer.
EVP tech is developed with computer science in the 1970s.
What are the 5 ways to categorize Auditory Evoked Responses (AER)?
- Labelled by Latency—the most common and popular method
- Labelled by stimulus-response relationship: Transient vs sustained
- Labelled as Exogenous or endogenous
- Labelled by the distance between the electrode and the generator
- Labelled by generator
How does the categorization of AER of labelling by latency work?
- Shorter the latency, lower the generators in ascending pathway, therefore smaller in amplitude:
- Deeper in location
- Smaller in number of neurons
- Shorter the latency:
more the transient for synchrony required - Less influenced by sleep
How does the categorization of AER of labeling by stimulus work?
Transient: signals vs responses
Example: click-evoked ABR
Signal: quick change of signal with time, better transient at onset and offset
Responses: those rely on the transient feature of signals, e.g., CAP in EcochG, ABR etc.
Why are transient signals needed for evoked ABR? (3)
- Early response generated from deeper structure (spatial attenuation)
- Early response generated from a smaller number of neurons.
- Action potential of early response has a shorter duration, therefore requires better synchronization.
- APs have both positive and negative phases. Short AP duration means a slight time shifting results in a larger phase shifting.
What is the comparison between transient signals and frequency selectivity? (5)
Applying transient signal: causes poor frequency selectivity
Transient: signal with short duration, sharp on and off
Short duration means broad band
Abrupt on and off causes frequency splattering
Method for compromising: short duration tone with time windows
What are 3 characteristics of clicks in research?
- Broad spectrum in E signals, further limited by transducer (speaker or earphone) but still broad, up limit: ~4-5 kHz
- Evoke below 5 kHz, spread at high intensity
- Synchronization better in high F at basal end due to high speed of traveling wave
Explain this graph related to clicks:
- Cut off at 5 kHz.
- At low-to-moderate intensity, cochlea is excited below 5 kHz
- Major contributor to ABR is 2-5 kHz region
- Click ABR thresholds represents hearing the best in 3-5 kHz, in normal hearing subjects.
- This will change for subjects with high frequency hearing loss into 3-5 k region.
Explain Sustained response or steady-state response:
Example: 40 Hz response
Repeated click presented at a rate of 40 Hz
Or any signal with a periodicity of 40 Hz, such as AM
Event-related potentials: related to the circumstances under which the nuclei are excited rather than to the physical properties of the signals
ASSR at higher frequency: generator moves to the brainstem
Established at higher frequency to overcome 40Hz
Why is it named steady-state potential?
it is not a response to the transient feature of the signal.
What are the advantages of 40 Hz event-related response?
Provides big amplitude, better frequency selectivity (due to long duration of stimuli)
What are the disadvantages of 40 Hz event-related response?
unknown generator, not reliable in children, influenced by sleep (consciousness)
40 Hz is impacted by sleeping status, not ABR which is why ASSR at 80-100 Hz
How 40 Hz ASR added up?
- internal events: Na-Nc, Pa-Pc, interval ~25 ms
- If stimuli have a periodicity of 40 Hz (25 ms interval), the peaks will add up
- In response to a single stimuli, our system produces many peaks. We add them over a period of time to be able to create the overall peaks
What are ASSR signals? (4)
ASSR tell the function of region of carrier frequency (CF)
Carriers: could be tone, narrow/wide band noise
Amplitude modulation to produce periodicity: modulation frequency (MF)
Signal energy: mainly at CF, two sidebands: CF+/-MF
40 Hz: ____________________
80 Hz: ____________________
Higher the frequency=
_________________________________
___________________________
________________________________________________
40 Hz: from midbrain and above
80 Hz: from the brainstem
Higher the frequency=
more from the peripheral (lower level)
Smaller the amplitude
Less influenced by sleep (more potential to be used by small children
How does the categorization of AER of labeling by Exogenous or endogenous work?
Exogenous: depend on the physical features of the stimulus (SLR, MLR, N1-P2, LLR)
Endogenous: perceptual—depend on the “context” not physical features; example: P300 and other cognitive components
Involves top-down process
What is Mismatch negativity (MMN)? (6)
Special signals that sit between the border of Exogenous or endogenous
Event Related Potential, but not cognitive
Elicited by discriminable changes in signal
No attention is needed
But based upon memory train established by preceding (standard) stimulus
Odd-ball paradigm
Explain the oddball procedure:
Two type of stimuli: 1. is regular stimuli 2. Odd signal rare/ randomized
Standard: 1000 Hz
Odd: 1000 Hz +
b: the difference between responses to standard and deviant sti
MMN is an MLR, not endogenous
Response to common signal and odd signal.
When the difference is small, you won’t see a difference between common and odd signal compared to if the difference is higher
What does this graph show?
Endogenous response: longer latency, require attention, related to perception
What does this graph show?
Stimuli: sentences with different endings.
Normal ending: frequent stimuli
Illogical ending: odd stimuli
Perception: understanding the sentences.
How does the categorization of AER from labeling by the distance between the electrode and the generator work? (2)
In near-field:
* Electrodes close to the generator
* Used when monitoring: (1) in SR, (2) in combination with far-field recording for localization of generator, (3) behavior of a single neuron
In far-field:
* Electrodes far away from the generator
* Used as a non-invasive method
How does the categorization of AER from labeling by the generator work? (3)
ECochG: response from cochlea
ABR: auditory brainstem response
Cortical responses/potentials
ABR is much smaller than MLR and SVP
MLR at the brainstem level
SVP at higher levels
How does this experiment work and what does it show?
Dipole electric field in Volume conductor
Dashed lines: pathway for current—between two poles.
Solid lines (iso-potential line): from any point in each line, the distance ratio to two poles remains constant.
Therefore, the voltage is the same along any line
The dashed lines and solid lines are orthogonal to each other
What does this graph show?
Amplitude change with distance
Near field: larger amplitude, larger change if distance change
Far field: smaller amplitude, small change with distance
What does this graph show?
Effect of electrode position: Far field recording (b) yields poor spatial selectivity and smaller amplitude
Explain the effect of neural structure:
Neural structure : Open vs closed field
Neural activities in a closed field cannot be recorded in far-field
Open field: Neurons are arranged in the same direction which yields better summation the signal distributed from all sides
Closed field: Neurons are orientation is randomized. AP may be spacially added but spacially cancel each other
What can we see in Electrocochleography (ECochG)? (3)
- First group of AER studied
- Those groups of response: Mature immediately after birth
- Contain receptor potentials from hair cells
- SP (summating potential), CM (cochlear microphonics)
- neural response—CAP (compound action potentials)
What can we see from clicks in EcochG?
SP is not shown because of the filter setting. Eliminating CM by averaging with alternating polarity
CM has no latency
N1 and N2 = CAP
How can we get rid of CM and show SP? By substracting/oddilating? 180 difference
What are the basic features of CM?
Basic Feature of CM
Mimic sound wave—can be eliminated by alternating averaging
In alternating average, signal is presented in opposite polarity in every following stimulation, adding the response will cancel the CM.
No latency (except the time for sound travels from speaker to cochlea)
Generated mainly by OHCs
Reflect the function of MET
Least useful in clinic
Easily contaminated by electro-magnetic artifacts from transducer
How to identify artifacts in CM testing? (3)
Artifacts increase linearly with sound level, but CM saturated at high sound level
Artifacts have no time delay (because electrical takes no time)
Close sound pathway will reduce CM but not artifacts
What are the basic features of SP? (4)
- Appears as baseline shift in response to sound
- Contributed from IHCs, OHCs, and probably neurons.
- Varied in amplitude, polarity with sound intensity, level, and duration, as well as electrode location
- Recorded from the extracochlear electrode, SP is likely to be negative (similar polarity as CAP), but can also be positive if stimulation frequency is very high.
What are basic features of CAP? (4)
- N1 from dendrites of SGNs, latency ~1 ms
- N2 from axons of SGNs, latency ~ 2 ms
Someone thinks that N2 from CN neurons. - Recorded extrocochlearly, CAP is dominated by SGNs of basal turn—due to better synchrony
- CAP is dominated by ANFs with high SR.
What is the application purposes from mainly SP and CAP? (4)
-Meniere’s disease/endolymphatic hydrops, by measuring SP/CAP ratio
- Identify wave I in ABR
- Monitoring in surgery
- Diagnosis of auditory neuropathy
Explain ABR: (5)
- Transient responses—require higher level of synchronization
- Short latencies–<12 ms
- Not influenced by sleep
- Quick and well-documented after-birth development
- Clear generators
How do we identify generators for ABR?
Combination of near-field and far-field recording to identify generators for ABR
What is the shortest ABR pathway?
SGN-CN-IC
What is the Longest ABR pathway?
SGN-CN-MNTB-SOC-LL-IC
Therefore, one peak may result from multiple nuclei.
What are the identification methods of the neural generators in ABR? (3)
Simultaneous near-field and far-field recording
Three-dimensional recording
Lesion experiment
(Certain wave peaks may have multiple generators because of the complexity of the auditory pathway)
Explain AMLR:
Auditory Middle Latency Response
Latencies: 12-50 ms
Generators: not clear/multiple sources for each peak
Later development. not available at birth (need 14 mo. to see clearly, not mature until 7yrs)
Easily contaminated by muscle movement
Influenced by sleep
Better frequency selectivity—steady state response
Explain ALR:
Auditory Later Response
Latencies: 50-250 ms
Multiple components
Influenced by sleep
Unclear generators
Big amplitude
But need longer stimulus interval
What are the Applications of AEP in Auditory Assessment? (5)
Long-latency response provides better frequency selectivity
Need cooperation from the subject
Only for mature subjects
Big variation
ABR is still used most, but need improvement
Behavioral tests are always favored, Evoked potentials are used when subjects cannot do behavioral tests
