1. Maggie Hamilton, Au.D. Hamilton CI Services, LLC
Mapping 101 NOCCCI August 5, 2009
Maggie Hamilton, Au.D.
Hamilton CI Services, LLC

2. What is a Map? Term comes from mathematics
A cochlear implant program loaded on a speech processor
Translates acoustic information into electrical current with other parameters

3. Why is it called a map?
From: Theory and Problems in Group Theory by Baumslag and Chandler 1968
“1.3 MAPPINGS
Definition of mapping
Assign to each even integer the value 1, and to each odd integer the value -1. Let us give the name a to this assignment: thus a assigns to each even element in Z, the set of all integers, the unique ………”

4. Why is it called a map?
“Such an assignment is termed a mapping from Z into {1, -1} or a map from Z into {1, -1}……..
b. Formal definition of Mapping
the reader may ask whether our definition of mapping is precise. After all, it depends upon an English word, assignment, a word this is used in many different ways.
A comparison with Section 1.2b is valuable. In Section 1.2b we introduced the concept of equivalence relation in X, but as we felt uneasy about it, we redefined it in terms of a subset of X2. Here too we feel uneasy about our definition of mapping and so we shall redefine it in terms of sets.”

5. Why is it called a map? A first course in Abstract Algebra
Paley and Weichsel
“A function f from A to B is also called a map or a mapping from A to B (a function is called a map simply because the cartographers map can be thought of as the image of f: A ’ B, where A is a region being mapped and B is the actual map)”

6. Why is it called a map? Webster’s New Collegiate Dictionary
Map (map), n. [F, mappe, in mappemonde map of the world. Fr.]
1. A representation (usually flat) of the surface of the earth or of part of it.
v.t.: mapped: mapping.
1. to delineate as on a map; also, to explore, survey, etc., in getting data for a map. 2. to chart the course of; to plan in detail.

7. Purpose of mapping
To deliver the maximum speech information, with the greatest clarity, within the constraints of the electronics, the body and battery power
Provide hearing using direct electrical stimulation to take the place of missing nerve cells

8. Dynamic Range of Hearing
Very Soft
~100dB
Very Loud

9. A Few Constraints
System uses FM radio waves to transmit a signal, across skin, to up to 22 electrodes
These electrodes are trying to take the place of what 20 thousand or so haircells do for a person with normal hearing and with reduced underlying nerve function
Different locations responsible for different frequency sounds - body supplies a sense of pitch depending on where stimulation occurs

10. Frequency Mapping
Normal hearing: ,000 Hz filtered by the basilar membrane
Implant system: Band-pass filters assigned to locations across the electrode array
Each electrode is responsible for a range of frequencies

11. T’s and C’s and M’s Oh my!
T levels: the amount of current necessary to consistently detect stimulation that is just barely audible
Different from audiometric thresholds

12. C’s and M’s
current level that is the upper or maximum loudness perception that is still perfectly comfortable for each electrode
The program never goes any higher than where C levels are set
Volume setting can increase or decrease C or M levels after the map is made.

13. Sensitivity “bubble” of sound Distance microphone picks up a signal
Affects where, within the current level range between T and C levels, stimulation starts
Increased sensitivity can mean close in sounds are louder or soft sounds can be picked up from farther away

14. Purpose of mapping
To develop the optimal combination of settings for each persons physiology
Not too loud, not too soft but like Baby Bear – Just right.
provide a range of loudness from very soft to very loud
To make all speech sounds salient and as clear as possible