Document:

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----------------------------------------------------------------
 Confidential Materials omitted and filed separately with the       ------------
Securities and Exchange Commission. Asterisks denote omissions.     Exhibit 10.1
----------------------------------------------------------------    ------------

                                   ADDENDUM 1
                     OEM Development and Purchase Agreement

Addendum 1 to the agreement dated 22nd day of December, 1999 (the "Agreement"),
by and between Aspect Medical Systems, Inc. ("Aspect") and GE Marquette Medical
Systems, Inc. ("GE").

Per section 7.3 of the Agreement, Aspect is revising the pricing structure of
the Aspect BIS/EEG Module Kit effective for all kits shipped on or after January
1, 2002. The attached Exhibit A, dated December 4, 2001, replaces Exhibit A in
the original Agreement.

For the purpose of calculating the volume discount for the calendar year 2001
all BIS module kits shipped from January 1, 2001 through December 31, 2001 will
be included in the total volume discount calculation and the discount shall be
in accordance with Exhibit A of the original Agreement.

For the purpose of calculating the volume discount for the calendar year 2002,
Aspect agrees to include the BIS module kits shipped from October 1, 2001
through December 31, 2001 in the total annual volume purchased in calendar year
2002. The price discount earned by this modified volume calculation shall be in
accordance with the Exhibit A attached to this Addendum 1 and the price discount
only be applicable to those BIS module kits shipped from January 1, 2002 through
December 31, 2002.

For example, if [**] BIS/EEG Module Kits are shipped between October 1, 2001 and
December 31, 2001, the volume discount on these [**] kits shall be in accordance
with Exhibit A in the original Agreement and shall not be considered for any
further discounts. A further example, if [**] BIS module kits are shipped in
calendar year 2002, the volume discount will be calculated based on [**] BIS
module kits ([**] from 2001 plus [**] from 2002) and priced in accordance with
Exhibit A attached to this Addendum 1. The price discount earned in accordance
with this discount shall only be applied to the [**] BIS module kits shipped in
calendar year 2002.

Please indicate your acceptance of the Amendment 1 by signing below.

Aspect Medical Systems, Inc.          GE Medical Systems, Inc.

By: /s/ Joan Rubin                    By: /s/ Pat VanRyzin
    --------------------------            --------------------------------

Title: Director, OEM Marketing        Title: General Manager, Patient Monitoring
       -----------------------               -----------------------------------

                                                     ADDENDUM 1 DECEMBER 4, 2001
BOSTON 1410625V1

<PAGE>

                                   ADDENDUM 1
                                    EXHIBIT A
                       ASPECT PRODUCTS AND PURCHASE PRICES
                            EFFECTIVE JANUARY 1, 2002

A)   ASPECT BIS/EEG MODULE KIT:

     List price for Aspect BIS/EEG Module Kit: $[**] (includes $[**] for
     components and $[**] for BIS license)

     Volume discounts:

     ---------------------------------------------------------------------------
      QUANTITY PER YEAR       PRICE (COMPONENTS & LICENSE)         DISCOUNT
     ---------------------------------------------------------------------------
           1-1,000                        $[**]                      [**]
     ---------------------------------------------------------------------------
         1,001-3,000                      $[**]                      [**]%
     ---------------------------------------------------------------------------
           >3,000                         $[**]                      [**]%
     ---------------------------------------------------------------------------

     Exceptions to this pricing are BIS/EEG Module Kits purchased by GE for the
     purpose of exchanging out Aspect A-2000 Monitors to modules as part of the
     co-marketing agreement. Kits for this purpose will be given the maximum
     discount (i.e., [**]% off list price).

B)   ASPECT BIS SENSOR

     Transfer price to GE for distribution solely to GE customers outside North
     America and solely for use with GE BIS/EEG Modules: [**]% of Aspect's list
     price in the U.S.

C)   ASPECT SPARE PARTS/ACCESSORY PRICES

     ---------------------------------------------------------------------------
        ORDERABLE PARTS/PRODUCTS    ASPECT LIST PRICE (US$)      GE PRICE (US$)
     ---------------------------------------------------------------------------
     DSC-XP (replacement)                    $[**]                    $[**]
     ---------------------------------------------------------------------------
     BIS Engine PCB (replacement)            $[**]                    $[**]
     ---------------------------------------------------------------------------
     Sensor Cable (replacement)              $[**]                    $[**]
     ---------------------------------------------------------------------------
     DSC-4 (replacement)                     $[**]                    $[**]
     ---------------------------------------------------------------------------
     User Manual                             $[**]                    $[**]
     ---------------------------------------------------------------------------

Note A: assumes imputed BIS license fee of $[**] per unit for BIS Engine PCB

                                                     ADDENDUM 1 DECEMBER 4, 2001
BOSTON 1410625V1<PAGE>

                                                                    EXHIBIT 10.2

                          ASPECT MEDICAL SYSTEMS, INC.

                            ADVISORY BOARD AGREEMENT

     THIS AGREEMENT, effective as of January 23, 2002, is by and between Stephen
E. Coit (the "Advisor"), and Aspect Medical Systems, Inc. a Delaware corporation
("Aspect").

     The parties agree as follows:

     1.  SERVICE AS ADVISOR.

         (a) The Advisor agrees to serve under the term of this Agreement as an
advisor to Aspect as a member of its Neurodiagnostic Advisory Board ("AB").

         (b) The Advisor will, at Aspect's request, devote up to 12 days in each
twelve month period during the term of this Agreement to attend and participate
in meetings of the AB. In addition, the Advisor shall from time to time consult
by telephone with Aspect in the Advisor's area of expertise.

     2. TERM. This Agreement may be terminated at any time by either party, with
or without reason, by written notice to the other party.

     3. COMPENSATION. Aspect shall, in a timely fashion, pay Advisor $3,000/day
for the services rendered after receiving an invoice for such services.

     4. EXPENSES. Aspect will reimburse the Advisor for all travel and other
out-of-pocket expenses incurred by him in connection with his services
hereunder, provided such expenses are approved in advance by Aspect and
appropriate documentation (e.g. receipts) of the incurred expenses is provided.

     5. CONFIDENTIALITY. The Advisor recognizes and acknowledges that all
technology, know-how, inventions, business plans, and other confidential
information of Aspect communicated to, learned of, developed or otherwise
acquired by the Advisor in the course of his or her services hereunder
("Confidential Information") are valuable assets of Aspect to be kept
confidential and secret, and therefore agrees to keep confidential and not
disclose or use, except in connection with the fulfillment of his services for
Aspect under this Agreement, any Confidential Information of Aspect.
"Confidential Information" shall not include, however, information placed in the
public domain through no fault of the Advisor; information disclosed to the
Advisor by a third party entitled to disclose it; information already known to
the Advisor prior to receipt thereof from Aspect; or information that is
independently developed by the Advisor without reference to information provided
by Aspect and not in the course of the performance of his services hereunder.
All tangible materials containing Confidential Information and all tangible
property of Aspect in the custody or possession of the Advisor shall be
delivered to Aspect, upon the earlier of (i) a request by Aspect or (ii)
termination of his relationship with Aspect. After such delivery, the Advisor
shall not retain any such materials or tangible property.
<PAGE>

     6. DEVELOPMENTS.

        (a) The Advisor will make full and prompt disclosure to Aspect of all
inventions, improvements, discoveries, methods, developments, software, and
works of authorship, whether patentable or not, which are created, made,
conceived or reduced to practice by him or under his direction or jointly with
others in the course of his performance of services for Aspect or using Aspect's
Proprietary Information, whether or not during normal working hours or on the
premises of Aspect (all of which are collectively referred to in this Agreement
as "Developments"). The Advisor agrees to assign and does hereby assign to
Aspect (or any person or entity designated by Aspect) all his right, title and
interest in and to all Developments, and all related patents, patent
applications, copyrights and copyright applications.

        (b) The Advisor agrees to cooperate fully with Aspect, both during and
after his relationship with Aspect, with respect to the procurement, maintenance
and enforcement of copyrights, patents and other intellectual property rights
(both in the United States and foreign countries) relating to Developments. The
Advisor shall sign all papers, including, without limitation, copyright
applications, patent applications, declarations, oaths, formal assignments,
assignments of priority rights, and powers of attorney, which Aspect may deem
necessary or desirable in order to protect its rights and interests in any
Development. The Advisor further agrees that if Aspect is unable, after
reasonable effort, to secure the signature of the Advisor on any such papers,
any executive officer of Aspect shall be entitled to execute any such papers as
the agent and the attorney-in-fact of the Advisor, and the Advisor hereby
irrevocably designates and appoints each executive officer of Aspect as his
agent and attorney-in-fact to execute any such papers on his behalf, and to take
any and all actions as Aspect may deem necessary or desirable in order to
protect its rights and interests in any Development, under the conditions
described in this sentence.

     7. REPRESENTATIONS OF THE ADVISOR.

        (a) The Advisor represents that there are no agreements to which he is a
party or by which he is bound, with any current or previous employer or any
other party, forbidding or restricting him from entering into this Agreement or
performing services for Aspect hereunder. In addition, the Advisor consents to
being named as an Advisor in various reports, brochures, advertisements or other
documents in printed or electronic form produced by or on behalf of Aspect,
including any and all documents filed with the Securities and Exchange
Commission.

        (b) The Advisor will not disclose to Aspect or induce Aspect to use any
confidential or proprietary information or material belonging to any previous or
present employer or others.

     8. MISCELLANEOUS.

        (a) If any other provision of this Agreement is prohibited under
applicable laws or regulations of any jurisdiction, such provision shall be
severed and the remaining provisions shall continue in full force and effect.

        (b) The relationship of the parties shall be that of independent
contractors.

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        (c) This Agreement shall be binding upon and inure to the benefit of
Aspect, and its successors and assigns, and the Advisor.

        (d) This Agreement shall be governed by the laws of the Commonwealth of
Massachusetts.

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date and year first above written.

                                  ASPECT MEDICAL SYSTEMS, INC.

                                  By:      /s/ J. Neal Armstrong
                                           -------------------------------------

                                  Date:    January 23, 2002

                                  ADVISOR

                                  Stephen E. Coit

                                  /s/ Stephen E. Coit
                                  ----------------------------------------------
                                  (SIGNATURE)

                                  Date:    January 23, 2002

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