Auditory Brainstem Response

The Auditory Brainstem Response element simulates clinical ABR testing. The learner preps the electrodes, acquires evoked waveforms at a series of levels, marks Waves I, III and V, finds the Wave V threshold, and reports each ear: absolute latencies, interpeak latencies, and a conclusion (normal, conductive, cochlear, retrocochlear, mixed, or no response). It supports click, tone-burst and CE-Chirp stimuli. In the designer it's listed as:

Electrode prep, then mark waves I/III/V and interpret latencies — click / tone / chirp, per ear

Like every Theta element, it follows the lifecycle Design → Settings → Testing → Scoring → Report. The three tabs split the same way: Design is the case, Settings is how the test runs, and Scoring & Report is everything about grading.

Design

The Design tab is the case — the patient, not the equipment.

Ears tested. Both ears, right only, or left only. An ear that isn't tested has no console button and is never graded.

Where the hearing comes from. Either the thresholds you type on this tab, or an Audiogram element in the same lesson. When linked, thresholds and air-bone gaps come from the audiogram — the 2–4 kHz average for click and CE-Chirp, the matching frequency for a tone burst — and are shown read-only. They are rounded to the nearest 5 dB, and an air-bone gap only counts when it is more than 10 dB; anything smaller is treated as no conductive component, so the whole loss reads as sensorineural.

If the linked audiogram is a feigned (non-organic) loss, the ABR follows the patient's true hearing, because a patient can't fake an ABR. A feigned loss over normal hearing gives a normal ABR, which is the cross-check the case teaches. Set that ear's loss type to match the true hearing (usually Normal).

Per ear:

Each ear shows what the learner should find — the conclusion, the absolute and interpeak calls, and the Wave V threshold — read off the same waveforms the learner will record. If the numbers contradict the loss type (a conductive ear with no air-bone gap, a retrocochlear ear whose interpeaks come out normal) an amber note says so and what to change.

In template mode each ear has a Vary each attempt panel: a severity offset applied to every threshold, an air-bone gap offset (only where you designed a gap), and a range for the retrocochlear delay. With a linked audiogram, the audiogram's Template / Fixed setting decides instead: a template audiogram gives every attempt its own hearing (and its own answer key), a fixed one gives every attempt the same case, and nothing on the ABR is randomised on top of it.

How the latencies behave

The simulated patient follows published adult norms, so the waveforms read the way the textbook says they should:

• Normal click at 80 dB nHL: Wave I 1.5, III 3.7, V 5.6 ms (I–V 4.1 ms), each getting ~0.03 ms later per dB as the level falls, and a little more near threshold.
• Conductive: the air-bone gap simply makes the stimulus quieter at the cochlea — every wave is later, the interpeaks stay normal.
• Cochlear (sensorineural): near-normal latency at high levels, a steep latency–intensity function near threshold. A high-frequency loss also delays every click and CE-Chirp wave: 0.1 ms per 10 dB of 4 kHz sensorineural loss above 50 dB HL (Selters & Brackmann, 1977), with normal interpeaks. It comes from the linked audiogram's 4 kHz threshold; without one, from the 4 kHz tone burst when the case tests it, otherwise the click or CE-Chirp's own threshold less its air-bone gap. From about 90 dB HL at 4 kHz this delay passes the 0.4 ms limit, so the answer key reads the absolute latencies as prolonged (the raw latency, as the trace shows it, not corrected), and the Design tab says so under the ear.
• Retrocochlear: the delay lands on every wave after Wave I — prolonged I–III and I–V, normal III–V, the classic eighth-nerve pattern. With no Wave I (a large cochlear loss on top) it only shows as a late Wave V.
• Tone bursts: each frequency follows Neely et al.'s (1988) latency curve — lower frequencies are later and slow down more as the level falls (500 Hz shifts about twice as far as 4 kHz). The recording window is 15 ms, or 20 ms at 500 Hz and 25 ms at 250 Hz, where Wave V near threshold runs past 15 ms.

Attempts recorded before these latency rules came in keep the latencies their learners saw, so the grades they were given never change. An ABR element (or an organization's element preset) saved before them still holds the old tone-burst offsets. Any offset left at its old default now reads as unset, so new attempts follow Neely's curve at that frequency and the Modified badge stays off. An offset you changed yourself is kept.

Preview. What a learner records, with the true peaks marked, for both ears side by side. To keep it short it shows three traces per ear — the top level, the Wave V threshold, and the level just below it (no response); Show all levels brings back the full stack. Show the latency–intensity function plots Wave V for both ears across every level against the normal range. The preview records the way the learner is expected to (see Recording settings below); open Recorded at… to try another rate, polarity or sweep count.

Settings

How the test runs. The choices most authors make are up front; the rest is under Advanced.

Advanced (collapsed — a Modified badge shows when anything inside differs from the standard):

Testing

1. Electrode prep (if on). A prep screen opens first: the learner scrubs each site on the patient's head, then checks impedances. Too little scrubbing leaves the impedance high; too much abrades the skin ("Ouch!"). The target is never shown — acceptability is judged silently at scoring. Poor prep makes every trace noisier.

2. Testing. The console at the bottom holds ear, stimulus, level, rate, polarity, sweeps and Acquire. Each trace builds up as sweeps are collected; Stop ends it early. Traces stack by level, and repeating a level overlays the repeat in grey — a real wave repeats, noise doesn't. Every trace is drawn in the ear's colour whether or not it holds a response: telling a response from noise near threshold is the learner's job, so nothing on screen does it for them.

3. Marking. Tap a trace to place the selected wave; a tap right on an existing marker selects that marker's wave instead. Marking starts on Wave V and stays on the wave you pick — use the wave buttons, 1–5, or ← / →. Slide a marker sideways to adjust it. Under the waveforms, the Wave latencies table lists every trace with a box per wave: typing a latency moves that marker, and ↑ / ↓ nudge it by 0.05 ms (Shift + ↑ / ↓: 0.25 ms). The interpeaks (I–III, III–V, I–V) sit beside each trace — on a narrow screen, under the table for the selected trace. A trash icon deletes a trace. The latency–intensity plot (both ears, against the normal range) is in the view settings (gear) and sits beside the report. On an exam the plot shows the learner's own points without the normal range.

The console can be run from the keyboard — Space to acquire, ↑ / ↓ for the level, Enter to save the Wave V threshold at the current level, and R / L / E for the ear. See Keyboard shortcuts.

4. Report. Beside the waveforms, for the ear on the console: the Wave V threshold for each tested stimulus (a level, or NR for no response), absolute latencies and interpeak latencies (normal / prolonged), and the conclusion. Switching ears on the console switches the report with it. Only what the Scoring & Report tab grades or reports is asked. An amber dot on an ear button means that ear's report isn't finished.

Scoring

Tolerances come first — how close an answer must be: wave marks ± 0.3 ms of the true peak, interpeaks ± 0.4 ms, the Wave V threshold ± 10 dB (no response must match exactly).

Below them, every item is Scored, Report-only, or Off, per ear, with the controls on the right — Same for both ears is on by default. The accepted rates, polarities and fewest sweeps sit under those items' names.

Peaks are graded on the highest-level trace of each stimulus — the one waves are read from clinically. Every wave genuinely present there must be marked; marks on other traces are shown but never counted, so collecting extra levels can only help.

For rate, polarity and sweeps, the expected value from Settings is always accepted and you can accept others alongside it (the fewest sweeps accepted can only be lowered below the expected count, never raised above it). Only the traces the learner read are judged:

• Every trace they marked a wave on must be recorded at an accepted rate and polarity, with at least the minimum sweeps.
• The levels each Wave V threshold was read from — the level they called and the level one step below it, or the loudest level they recorded for no response. Each of these levels passes when at least one trace there was recorded at an accepted rate (and, separately, polarity), and its sweeps are judged on its best-averaged trace. A quick look at another setting beside a proper recording costs nothing, but a level recorded only the wrong way fails. The called level and the one below it are judged separately.

Traces at other levels aren't judged. If the learner marked nothing and reported no threshold at a level they recorded, every level they recorded is judged by the same one-trace-per-level rule.

The tab ends with the answer key for the design, read exactly as an attempt will read it. What counts as a prolonged latency is on the Settings tab.

Report

On the results screen (View data), each graded ear shows the waveform stack for every stimulus the learner recorded — redrawn exactly as recorded, noise and all — with their marks, a latency table, and their report beside the expected answers. The graded breakdown is on the Scores tab.

The PDF shows the same per ear: up to three waveform stacks (anything that doesn't fit is named in the caption), a run table with I / III / V and the interpeaks, and the interpretation and Wave V thresholds the lesson asked for, next to the expected values.

Advanced analytics can measure wave-marking accuracy and error, unmarked waves, interpeaks, thresholds, the conclusion, electrode prep, sweeps collected, and — when the lesson grades it — whether the traces were recorded with the expected settings.