Multichannel Systems MEA2100 User Manual

MEA2100-System Manual

Information in this document is subject to change without notice.

No part of this document may be reproduced or transmitted without the express written permission of Multi Channel Systems MCS GmbH.

While every precaution has been taken in the preparation of this document, the publisher and the author assume no responsibility for errors or omissions, or for damages resulting from the use of information contained in this document or from the use of programs and source code that may accompany it. In no event shall the publisher and the author be liable for any loss of profit or any other commercial damage caused or alleged to have been caused directly or indirectly by this document.

Printed: 21. 02. 2014

Multi Channel Systems

MCS GmbH

Aspenhaustraße 21

72770 Reutlingen

Germany

Fon +49-71 21-90 92 5 - 0

Fax +49-71 21-90 92 5 -11

info@multichannelsystems.com

www.multichannelsystems.com

Microsoft and Windows are registered trademarks of Microsoft Corporation. Products that are referred to in this document may be either trademarks and/or registered trademarks of their respective holders and should be noted as such. The publisher and the author make no claim to these trademark.

Table of Contents

1 Introduction 1

1.1 About this Manual 1

1.2 Welcome to the MEA2100-System 1

2 Important Safety Advice 3

2.1 Important Safety Advice 3

2.2 Guarantee and Liability 4

2.3 Operator's Obligations 4

3 Software 5

3.1 Setting up MC_Rack 5

3.2 System Requirements 7

3.3 First Use of MC_Rack 8

3.4 Setting up the Internal Stimulus Generator 11

3.5 Setting up LTP-Director Software 23

3.5.1 System requirements 23

3.5.2 Recommended operating system settings 23

3.5.3 Installing the LTP-Director Software 24

3.5.4 Installing the LTP-Analyzer Software 24

3.6 Setting up Cardio2D Software 25

3.6.1 Installing the Cardio2D Software 26

3.6.2 Installing the Cardio2D+ Analyzer Software 26

4 Hardware 27

4.1 Hardware Configuration 27

4.2 MEA2100 Interface Board 28

4.3 MEA2100 Headstages 31

4.4 Digital Signal Processor 33

4.5 Bandwidth and Gain Specification 34

4.6 Stimulus Generator 35

5 The MEA2100-System 37

5.1 Setting up the MEA2100-System 37

5.2 Setting up the MEA 41

iii

MEA2100-System Manual

 Troubleshooting 45

6.1 About Troubleshooting 45

6.2 No Computer Connection / No Recording Possible 45

6.3 Triggering / Digital Input does not Work 46

6.4 Noise on Single Electrodes 46

6.5 MEA is defective 47

6.6 Overall Noise / Unsteady Baseline 47

6.7 Missing Spikes or Strange Signal Behavior 48

7 Appendix 49

7.1 MEA2100 Configuration Software 49

7.2 Technical Support 51

7.3 Technical Specifications 52

7.4 Pin Layout 55

7.5 Changing Gold Spring Contacts 58

7.6 Stimulation 61

7.7 Safe Charge Injection Limits 61

8 Index 65

1 Introduction

1.1 About this Manual

It is assumed that you already have a basic understanding of technical and software terms. No special skills are required to read this manual.

If you are using the device for the first time, please read the Important Safety Advice before installing the hardware and software, where you will find important information about the installation and first steps.

The device and the software are part of an ongoing developmental process. Please understand that the provided documentation is not always up to date. The latest information can be found in the online help of the latest version of MC_Rack and in the Download and Documentation section of the MCS web site: www.multichannelsystems.com

1.2 Welcome to the MEA2100-System

The MEA2100-System is the latest development in the MEA product family of Multi Channel System MCS GmbH. The MEA2100-System is a compact and portable stand-alone system for extracellular recordings from microelectrode arrays (MEAs) with integrated amplification, data acquisition, online signal processing, integrated stimulus generator as well as temperature control.

The MEA2100-System consists of two main devices: The interface board with integrated signal processor and the headstage equipped with amplifier, A / D converter and stimulus generator. It is possible to connect one headstage only or two headstages to one interface board. If you are dealing with two headstages, each headstage can be operated independently by opening the data acquisition software MC_Rack for each headstage separately.

It is a highly flexible system, using a headstage that will fit on inverted and upright microscopes. The MEA2100-System acquires data from up to 240 electrode channels, 120 channels per headstage and a sampling frequency of 50 kHz per channel. Eight additional analog IN channels are available, and a 16 bit digital IN / OUT channels. The digitized electrode data is transmitted to the connected interface board via eSATAp cable. The connection between interface board and computer uses a high speed USB connection. Thus, it is possible to use any computer as a data acquisition computer, also a laptop.

MEA2100-System Manual

Data is recorded, stimulated, analyzed, graphed and reviewed with the powerful and easy-to-use MC_Rack program from Multi Channel Systems MCS GmbH. The control functions of the internal stimulator are also integrated into MC_Rack. The MC_Rack data format can be converted in other standard formats with the software MC_DataTool.

The Headstage of the MEA2100-System

At the moment five different types of headstages are available for the MEA2100-System. A headstage for microelectrode arrays (MEAs) with 120 electrodes, a headstage for microelectrode arrays with 60 electrodes or for two MEAs with 60 electrodes respectively and headstages for one or two small microelectrode arrays with 32 recording and 12 stimulation electrodes.

The data acquisition integrated in the headstage supports 120 electrode channels. The sampling rate, signal range and bandwidth can be adjusted via software control and is suitable for a broad range of applications, from single unit spike recordings to field potentials from whole heart preparations.

A special advantage are the three integrated stimulus generator units, which deliver monophasic or biphasic rectangular pulses, as single pulses or pulse trains. You can choose between current or voltage stimulation and you can select each MEA electrode for stimulation within the MC_Rack software. The integrated blanking circuit (BC) disconnects the electrodes from the amplifiers during the stimulation and avoids stimulus artifacts.

As usual in MEA-Systems, the MEA2100-System features a heating element with a Pt100 temperature sensor. If you connect a temperature controller TC02 to the heating element via D-Sub 9 connector, the heating element guarantees constant temperature conditions for the biological sample on the chip. A perfusion system with heating is available for the MEA2100 as optional accessory.

All MEA types with 60 or 120 channels can be used. A modified base plate is available for the headstage to be able to work with perforated MEAs also.

Because of the compact designed headstage you can use most inverted or upright microscopes, for the optical control of the sample on the MEA chip.

The Interface Board of the MEA2100-System

The interface board of the system is equipped with a high-capacity digital signal processor DSP. By moving the detection and analysis of signals and from the data acquisition computer to the digital signal processor inside the interface, it is possible to run online filtering, analysis and feedback stimulation in real-time. The MEA2100-32-System and the MEA2100-Lite- System are descendants including all functions of the MEA2100-System with the exception of the real-time feedback via DSP.

The Digital IN / OUT connector (68-pin MCS standard connector) for 16 digital in- and output bits guarantees the communication with other devices. You can use the digital TTL inputs, for example, for synchronizing the recording in MEA2100-System with other systems. The digital TTL outputs can be used for triggering other devices, for example, an imaging setup.

Four digital inputs and four digital outputs (bit 0 to bit 3) are separately available via Lemo connectors on the front of the interface board. The eight analog inputs (serial connector) are intended for recording additional information from external devices, for example, for recording patch clamp in parallel to the MEA recording, for monitoring the temperature, or for fluidic control.

Two of the eight analog inputs are separately available via Lemo connectors on the front of the interface board. You can connect an audio system to the Audio Out (3.5 mm phone jack) to make electrical activity audible. This audio output is in real-time. Headphones or a speaker can be connected directly to the Audio Out. Two channels at a time can be converted into sound.

2 Important Safety Advice

2.1 Important Safety Advice

Warning: Make sure to read the following advice prior to installation or use of the device and the software. If you do not fulfill all requirements stated below, this may lead to malfunctions or breakage of connected hardware, or even fatal injuries.

Warning: Always obey the rules of local regulations and laws. Only qualified personnel should be allowed to perform laboratory work. Work according to good laboratory practice to obtain best results and to minimize risks.

The product has been built to the state of the art and in accordance with recognized safety engineering rules. The device may only

 be used for its intended purpose;

 be used when in a perfect condition.

 Improper use could lead to serious, even fatal injuries to the user or third parties and damage

to the device itself or other material damage.

Warning: The device and the software are not intended for medical uses and must not be used on humans.

Malfunctions which could impair safety should be rectified immediately.

High Voltage

Electrical cords must be properly laid and installed. The length and quality of the cords must be in accordance with local provisions.

Only qualified technicians may work on the electrical system. It is essential that the accident prevention regulations and those of the employers' liability associations are observed.

 Each time before starting up, make sure that the power supply agrees with the specifications

of the product.

 Check the power cord for damage each time the site is changed. Damaged power cords should

be replaced immediately and may never be reused.

 Check the leads for damage. Damaged leads should be replaced immediately and may never

be reused.

 Do not try to insert anything sharp or metallic into the vents or the case.

 Liquids may cause short circuits or other damage. Always keep the device and the power cords

dry. Do not handle it with wet hands.

Requirements for the Installation

Make sure that the device is not exposed to direct sunlight. Do not place anything on top of the device, and do not place it on top of another heat producing device, so that the air can circulate freely.

MEA2100-System Manual

2.2 Guarantee and Liability

The General conditions of sale and delivery of Multi Channel Systems MCS GmbH always apply. The operator will receive these no later than on conclusion of the contract.

Multi Channel Systems MCS GmbH makes no guarantee as to the accuracy of any and all tests and data generated by the use of the device or the software. It is up to the user to use good laboratory practice to establish the validity of his / her findings.

Guarantee and liability claims in the event of injury or material damage are excluded when they are the result of one of the following.

 Improper use of the device.

 Improper installation, commissioning, operation or maintenance of the device.

 Operating the device when the safety and protective devices are defective and/or inoperable.

 Non-observance of the instructions in the manual with regard to transport, storage, installation,

commissioning, operation or maintenance of the device.

 Unauthorized structural alterations to the device.

 Unauthorized modifications to the system settings.

 Inadequate monitoring of device components subject to wear.

 Improperly executed and unauthorized repairs.

 Unauthorized opening of the device or its components.

 Catastrophic events due to the effect of foreign bodies or acts of God.

2.3 Operator's Obligations

The operator is obliged to allow only persons to work on the device, who

 are familiar with the safety at work and accident prevention regulations and have been

instructed how to use the device;

 are professionally qualified or have specialist knowledge and training and have received

instruction in the use of the device;

 have read and understood the chapter on safety and the warning instructions in this manual

and confirmed this with their signature.

It must be monitored at regular intervals that the operating personnel are working safely.

Personnel still undergoing training may only work on the device under the supervision of an experienced person.

3 Software

3.1 Setting up MC_Rack

Warning: The operating system settings of the data acquisition computer were preconfigured by MCS and should not be changed by the user. Changing these settings can lead to program instabilities and data loss.

Important: The driver of the MEA2100-System is automatically installed together with the MC_Rack program. Please install MC_Rack before connecting the MEA2100-System to a data acquisition computer.

Please check the system requirements before you install the MC_Rack software. MCS cannot guarantee that the software works properly if these requirements are not fulfilled. It is recommended that you check the MCS web site for software updates on a regular basis.

1. Double-click Setup.exe on the installation volume.

The installation assistant will show up and guide you through the installation procedure.

2. Follow the instructions of the installation assistant.

Installing MC_Rack with the MEA2100-System connected to the computer

The Windows operating system detects a new hardware when the MEA2100-System is connected to the computer, if the program has not been installed beforehand. Please make sure the device has power, that is, the power LED is lighting. Simply cancel the "Found New Hardware Wizard" and proceed with the installation of the MC_Rack program.

Connecting the MEA2100-System to a computer with installed MC_Rack

If MC_Rack had already been installed on the computer before the hardware was connected, the operating system needs to load the driver once. After this procedure, the MEA2100-System will be automatically recognized by the operating system.

1. Connect the MEA2100-System to the USB port of the data acquisition computer. Please make sure the device has power, that is, the power LED is lighting.

2. Switch the computer on.

The "Found New Hardware Wizard" is displayed.

1. Choose the option "No", not this time and continue with "Next".

2. Choose the option "Install" the software automatically as recommended. Continue with "Next".

3. The Wizard will automatically find the appropriate MEA2100-System driver. Continue with "Next".

4. The driver installation is finished.

Please check the system requirements before you install the MC_Rack software. MCS cannot guarantee that the software works properly if these requirements are not fulfilled. Please see the MC_Rack help or manual for more information. It is recommended that you check the MCS web site for software updates on a regular basis.

5. Double-click Setup.exe on the installation volume. The installation assistant will show up and guide you through the installation procedure.

6. Follow the instructions of the installation assistant. The MEA2100-System driver and MC_Rack are installed (or updated) automatically.

MEA2100-System Manual Connecting the MEA2100-System

After MC_Rack has been installed on the computer and the MEA2100 device is connected for the first time, the operating system needs to load the driver once. After this procedure, the MEA2100-System will be automatically recognized by the operating system.

1. Connect the MEA2100-System to the USB port of the data acquisition computer. Please make sure the device has power, that is, the power LED is lighting. Switch the computer on.

2. The "Found New Hardware Wizard" is displayed.

3. Choose the option "No", not this time and continue with "Next".

4. Choose the option "Install" the software automatically" as recommended. Continue with "Next".

5. The Wizard will automatically find the appropriate MEA2100-System driver. Continue with "Next".

6. The driver installation is finished.

Please refer to the MC_Rack manual or help.

It is not recommended to run any applications in the background when using MC_Rack. Remove all applications from the "Autostart" folder.

Only one software is necessary to operate the MEA2100-System, MC_Rack. If you purchased the computer together with the system, the software and drivers will be preinstalled and you can start working straight away. If you purchased the computer separately, or want to switch to a different computer, software and drivers must be installed on this computer. Updates for MC_Rack are released on a regular basis on the web site of Multi Channel Systems (www.multichannelsystems.com). Please always use the latest version to ensure optimal performance of your system.

The MEA2100-System is a plug and play device. The driver is automatically installed together with the MC_Rack program. It is therefore recommended to install MC_Rack before connecting the MEA2100-System to a data acquisition computer.

Important: Please make sure that you have full control over your computer as an administrator. Otherwise, it is possible that the installed hardware does not work properly.

3.2 System Requirements

One of the following Microsoft Windows ® operating systems is required: Windows 8.1, Windows 7 (32 or 64 bit), VISTA or XP, English and German versions supported. Other language versions may lead to software errors.

If no MEA2100-System is present, MC_Rack opens in a simulation mode. A computer with low performance may lead to performance limits more often; therefore, MCS recommends an up-to-date computer optionally with a separate hard disk. Please note that there are sometimes hardware incompatibilities of the MEA2100-System and computer components; or that an inappropriate computer power supply may lead to artifact signals. Please contact your local retailer for more information on recommended computer hardware.

Important: You need to have installed the latest MEA2100-System driver to operate the MEA2100-System, which is automatically installed with MC_Rack. The installation may be invalid if the MEA2100-System does not respond. Please contact Multi Channel Systems or your local retailer in this case.

Recommended BIOS settings

Recommended operating system settings

The following automatic services of the Windows operating system interfere with the data storage on the hard disk and can lead to severe performance limits in MC_Rack. These routines were designed for use on office computers, but are not very useful for a data acquisition computer.

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 Turn off Screensaver.

 Turn off Windows Indexing Service for all local disks.

 Turn off Optimize hard disk when idle (automatic disk fragmentation).

 Manual management of automatic Windows Update.

 Power Options: Power scheme: Never turn off monitor, hard disk and system standby.

 It is also not recommended to run any applications in the background when using MC_Rack.

Remove all applications from the Autostart folder.

 Be careful when using a Virus Scanner. These programs are known to disturb MC_Rack,

and even data loss may occur.

When using a MEA2100-System it is recommended to connect a high performance computer with a separate hard disk for program files and data storage. The provided possibility to use up to 240 channels with up to 50 kHz needs high memory capacity. Please remove data and defragment the hard disk regularly to ensure optimal performance.

MEA2100-System Manual

3.3 First Use of MC_Rack

Data Source Setup

Every MEA of the MEA2100-System can be operated completely independently by one instance of MC_Rack. To be able to open more than one instance of MC_Rack, please first open the "Advanced Configuration" dialog in the "Edit" menu.

Please increase the maximum number of instances according to the number of MEAs you are going to use in parallel:

 one MC_Rack instance for one HS32, HS60 or one HS120,

 two MC_Rack instances for one HS2x32, HS2x60, or two HS32, HS60 or two HS120,

 four MC_Rack instances for two HS2x32 or HS2x60.

Afterwards you can open several instances of MC_Rack and assign every instance to one MEA of the system.

After opening MC_Rack as many times as necessary, please open the “Data Source Setup” dialog from the “Edit” menu. This dialog can only be opened in one instance at a time, please do the adjustments in one instance after the other. The example below shows the settings for one MEA2100-HS2x60.

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Select “USB” and MEA2100 (S/N: XXXXX-A) as Data Source. Select “Configuration” in the “Source Layout”. Please select the type of the connected headstage in the "Amp" drop down menu. If a MEA2100-HS2x60 is connected you have additionally to select the "Block" in the right drop down menu of “Virtual Device Configuration”. For the first instance of MC_Rack, select Block 1 (Channel 1…64) and for the second instance Block 2 (Channel 65…128). Select the appropriate MEA type from the drop down menu for each instance. If a second headstage is connected to the same interface board, it will become available in the "Data Source Setup" as MEA2100 (S/N: XXXXX-B). The settings for the second headstage are analogous to the first.

MEA2100-32-System

The MEA2100-32-System is a descendant of the MEA2100-System with all available functions except of the real-time feedback feature. In “Data Source Setup” it is present as an different device “MEA2100-32”. The “MEA2100-2x32” can be operated separately with two instances of MC_Rack as usual, two headstages with two MEAs with four instances of MC_Rack.

MEA2100-System Manual Hardware Settings for the MEA2100-System in the Data Source

When using the MEA2100-System, the “Hardware” tab of the MC_Rack software is modified. Please see also chapter “Defining a Data Source”.

In the "Hardware" tab of the Data Source, the gain setting must be adjusted to ensure a correct scaling of the data in MC_Rack. The gain is a fixed hardware property, while sampling frequency and input voltage range of the data acquisition board can be selected according to the demands of the experiment.

The appropriate “Amplifier Gain” factor of the MEA2100-System will automatically be entered. Depending on the hardware revision the MEA2100-System the gain factor is 5, in older revisions factor 2.

The ADCs (Analog Digital Converter) of the MEA2100 system have a resolution of 24 bit, the MC_Rack software can record and display data with a resolution of 16 bit. To handle the complete 24 bit range, the input voltage range selection in the MC_Rack software can select a window of 16 bit out of these 24 bits, resulting in the following signal ranges:

+/- 812 μV; +/- 1727 μV, +/- 3545 μV; +/- 7090 μV;

+/- 14 mV; +/- 28 mV, +/- 57 mV; +/- 114 mV; +/- 227 mV

A smaller input range results in a better resolution in bits/μV, signals larger than the selected range will be clipped. In summary, the procedure has exactly the same functionality as a software selectable gain, even though, strictly speaking, it is not.

The “Sampling Frequency” should also be selected as low as possible, depending on the signals you like to measure, to minimize data file size.

If several instances of MC_Rack are used to operate the MEA2100-System, for example with a MEA2100-HS2x60 headstage or two MEA2100-HS120 headstages, each instance of MC_Rack operates independently; you can define the “Input Voltage Range of Data Acquisition Board” and the “Sampling Frequency” for each instance of MC_Rack individually.

Hardware Filter Settings

While the MEA2100-System in principle can measure DC signals, this is for most purposes very impractical, as the baseline would constantly drift. Therefore the system is equipped with software configured hardware filters. By default, a second order high pass filter with a cut off frequency of 1 Hz is used to prevent a baseline drift. The upper cut off frequency is 3.3 kHz. Additionally you can use the software filters of MC_Rack, if necessary.

Note: It is possible to change the settings of these filters without modification of firmware or hardware. Please read chapter ”MEA2100 Configuration Software”.

3.4 Setting up the Internal Stimulus Generator

The headstage of the MEA2100-System is equipped with an integrated 3-channel stimulus generator. The three stimulation channels operate independently.

Even when using multiple instances of MC_Rack, each instance is completely independent and each instance has three stimulus channels available for the electrodes which are controlled by that instance.

It is possible to choose between current or voltage controlled stimulation, and any electrode can be selected for stimulation. The control functions for electrode selection and definition of the stimulation parameters are integrated into MC_Rack you do not need any additional software. However, it is possible to import stimulation patterns generated in MC_Stimulus II as ASCII data.

Important: the same stimulation pulse, please be aware that in some configurations (when more than one electrode is used within a block of 30 electrodes which are powered by the same current source) the current level of the stimulation pulse will be divided among these electrodes. That means the current level is lower than expected. Please read also chapter “Stimulation” in the Appendix.

Add the internal stimulus generator to your rack: Click menu “Edit” and choose "Add MEA2100 Stimulator".

In current stimulation mode, if you select two or more stimulation electrodes for

Software

The following dialog appears.

Select the tab of any of the three stimulation channels (Stimulus 1, 2 or 3). In the "Stimulus" tab page, you can define the stimulation pulse and select how the stimulation is started and stopped.

MEA2100-System Manual

Click “Stimulus 1” tab page, for example.

Defining the stimulation pulse

In "Output Mode" you can choose whether you want to stimulate in voltage or current mode. To set up the stimulus pulse or pulse train, please use the eight provided up down boxes.

The individual stimulation pulse is defined in the "Pulse" window. Set up a monophasic pulse by selecting the voltage / current in mV/μA and the duration time T1 in μs. For setting up a biphasic pulse you have to select the stimulation strength and time also for the second phase. The shape of the pulse is displayed immediately in the window below. Once started, a programmed paradigm will run to its’ end, or till it is manually terminated.

Warning: Anodic (positive) pulses can lead to a formation of titanium oxide on the MEA electrodes. When using MEA electrodes of TiN material, use only negative voltages pulses or biphasic current pulses applying the negative phase first. Always regard the safe-charge injection limits. Otherwise, electrodes can be irreversibly damaged by electrolysis.

When using the "Train" window for setting up a pulse train, please select the "Inter Pulse Interval IPI" in μs and the number of pulses in the train in "Repeat". If no pulse train is needed, set the IPI to zero and the “Repeat” to one.

The "Inter Train Interval ITI" function can be used to repeat a single pulse or a pulse train.

The interval time can be set in ms, and also the number of repeats. The complete programmed paradigm is shown in the graphical display below the stimulus window.

Once started, a programmed paradigm will run to its’ end, or till it is manually terminated.

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If the “Continuous Mode” is activated, the paradigm will be repeated indefinitely, till manually stopped. Please note that stimulation does not stop when MC_Rack is stopped.

Importing a stimulation file created with MC_Stimulus II

To generate more complex stimulation patterns it is possible to import a stimulation file setup with the MC_Stimulus II software as ASCII data. Please read the respective stimulus generator STG manual for detailed information about creating a stimulus file. You can import any pulse type available in MC_Stimulus II.

 Program the file in MC_Stimulus II as usual: channel 1 will become stimulus 1 in MC_Rack,

channel 2 will become stimulus 2, and channel 3 will become stimulus 3

 Export the file as ASCII file (MC_Stimulus II: File - Export ASCII)

 Import this file in MC_Rack (Stimulus Tab: Import File)

It is not necessary to program Sync Out pulses. Information in MC_Stimulus Channel 4 and up and all Sync Out channels will be ignored.

The “Stimulus” interface will be disabled and the imported pattern will be shown in the graphical stimulus display. To skip the imported pattern and reactivate the “Stimulus” interface, click the “Unload File” button.

MEA2100-System Manual Starting and stopping the stimulation

In the "Trigger" drop down menu it is possible to choose different types of triggers to start the stimulation. The LED next to the Start / Stop button indicates the status of stimulation; the LED turns orange when the stimulation is running, the LED turns grey when the stimulation is stopped.

Important: It is not necessary for MC_Rack to run in "Play" or "Record" mode to be able to start a stimulation paradigm, and a running paradigm will continue even after MC_Rack is stopped. Once started, a programmed paradigm will run to its’ end, or till it is manually terminated.

If "Manual" is selected in the "Trigger" drop down menu, the "Start" and "Stop" buttons can be used to control the stimulation manually.

If "Start" is selected, the stimulation starts as soon as MC_Rack is started (in "Play" or "Record" mode). A delay between start of MC_Rack and start of stimulation in ms can be selected in the "Pre" time window. You can stop the stimulation paradigm by pressing the "Stop" button.

If a "DigIn" is selected, the stimulation starts if a TTL pulse is delivered to the respective connectors Digital In 1 to 4 on the front of the MEA2100-System interface board.

If the internal STG is connected to one or more "Trigger Detectors" in the MC_Rack virtual tree, it is also possible to start the stimulation on any of these Triggers (Trigger 1, 2 …).

If the “Real-time Feedback” tool is activated, any of the internal STG can be started on one of the conditions defined in the Real-time Feedback tool (RF1, RF2, RF3 …). Please see chapter “Real-time Feedback with MEA2100-System” for more information. The tool must be present and active, for the "Real-time Feedback" conditions to become available.

Important: The Real-time Feedback is not available in MEA2100-32- and MEA2100-Lite-Systems!

If a new trigger arrives before the programmed stimulation paradigm is finished, the paradigm starts again from the beginning. All three stimulus channels can be started and stopped independently.

To repeat a stimulation pulse in a loop, activate the “Continuous Mode”. The pulse will be applied continuously until it is stopped by manually with the “Stop” button.

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Selection of stimulation electrodes

Click the “Channels” tab to assign the programmed stimulation patterns to individual electrodes, and to activate the blanking circuit BC, and to operate the “List Mode”.

To apply the stimulation pattern of a specific stimulation channel (Stim. 1, 2 or 3) to one or more electrodes, select the desired stimulation channel (Stim. 1 to 3) and click the electrodes you want to apply this paradigm to. To apply the stimulation pattern to all electrodes, click the button “All” below the grid. Electrodes can be grounded or selected as regular recording electrodes (Not Stim.) in the same way.

Electrodes selected for stimulation pattern 1 “Stim.1” are colored in blue, for stimulation pattern 2 “Stim. 2” are colored in red, or stimulation pattern 3 “Stim. 3" are colored in yellow. To cancel a stimulation electrode, please use the radio button “Not Stim.” and click on the selected electrode.

The blanking feature to avoid stimulation artifacts can be activated or deactivated via the check box “Blanking”.

For the MEA2100-32-System the “Channels” tab is adapted respectively. The function “Dedicated Stimulation Electrodes” is not available.

MEA2100-System Manual Blanking

A blanking signal transiently switches off the input stage of the amplifier during the stimulus, thus avoiding stimulus artifacts on non-stimulating electrodes.

Amplifier saturation is effectively prevented and the recovery time is greatly reduced. During the blanking period, a flat line is displayed. This blanking period extends a few hundred microseconds before and after the actual stimulus, currently 600 μs, but might be subject to change. The pre- and post-time are experimentally optimized and can not be changed by the user.

Dedicated Stimulation Electrodes

The function “Dedicated Stimulation Electrodes” can be used to further avoid stimulation artifacts on the electrodes surrounding the stimulation electrode which are sometimes not completely removed by the blanking alone. Usually, the stimulation electrode will be connected to the stimulator output only during the stimulation pulse, and afterwards be switched back to the amplifier to be used as recording electrode. This sometimes causes switching artifacts independently from the actual stimulation.

However, if the function “Dedicated Stimulation Electrodes” is active, the selected stimulation electrodes will be constantly connected to the stimulator outputs. This causes permanent higher noise on the selected stimulation electrodes, and makes of course recording on the stimulation electrodes impossible, but almost completely removes residual artifacts. The images below show stimulation on electrode F3 with and without “Dedicated Stimulation Electrodes” activated.

Note: The artifact suppression additional to blanking via “Dedicated Stimulation Electrodes” is not available when using the “List Mode”.

“Dedicated Stimulation Electrodes” selected (X-Axis: 1000 ms, Y-Axis: +/- 500 μV).

“Dedicated Stimulation Electrodes” deselected (X-Axis: 1000 ms, Y-Axis: +/- 500 μV).

Software

List Mode

Clicking the button List Mode opens an additional window: List of Stimulation Patterns. In List Mode it is possible to generate and download a list of up to 256 user defined stimulation patterns, which will then be applied automatically one after the other.

When the List Mode is activated, the three stimulator units are coupled to a single starting trigger. The starting trigger is set in the tab of the first stimulator unit, Stimulus 1. In Stimulus 2 and 3, the respective functions are disabled. To uncouple the stimulator units again, close the List Mode dialog. The step from one stimulation pattern to the next in the list happens when the start condition defined for Stimulus 1 occurs (for example, manual start, incoming trigger, real-time feedback trigger) and all three stimulator units are idle. Please see the red bars on the picture. However, the next pattern can only be started by the respective starting condition when the previous stimulation paradigm, including all breaks, is completely finished.

That means, if one stimulation pattern of any of the three stimulator units is still running when the condition occurs, nothing will happen. This also holds true when a stimulator unit is not actually used in the currently active stimulation pattern. Hence, the longest programmed stimulation pattern determines the minimum possible time between two starting triggers, even if the respective stimulator unit is not actually used. It is therefore advisable to set a stimulation pattern with a length of 0 on all unused stimulator units, and keep all patterns as short as possible.

A stimulation pattern can contain single or multiple stimulation electrodes and may get an user defined name. To create a list of different stimulation patterns, please do the following.

MEA2100-System Manual

Click the button “List Mode”. There are two windows in the “List of Stimulus Pattern”. The small window on the right side is for typing in a name for a pattern. In the window on the left side the list of stimulation pattern will be displayed and arranged.

When opening the “List Mode” for the first time, the term “New” appears and the current stimulation pattern is the first stimulation pattern in the list. To change the name, please overwrite the name with the specific name of this pattern in the small window.

To insert a stimulation pattern, select with the mouse the position in the list where you want to place the pattern. The line will be highlighted in blue. Type the specific name of this pattern in the small window. Click the button "New" and the new list entry appears.

To append a pattern, select the line under the last list entry. The line will be highlighted in blue. Type the specific name of this pattern in the small window. Click the button "New" and the new list entry appears.

To rename a pattern of the list, select the pattern which will be highlighted in blue. Then you can change the name of the pattern in the list. Please click the “Rename” button.

The command “Remove” eliminates the pattern in the list, which is highlighted in blue. With “Up” or “Down” you can move the patterns to arrange them in that sequence you like to apply them.

Click “Download” to download the list of stimulation patterns to the internal stimulus generator of the MEA2100 headstage.

To start the stimulation patterns in the list mode, please use the “Trigger Start” in “Stimulus 1” tab of this dialog. The trigger start in Stimulus 2 and Stimulus 3 tab will not be available, but all three triggers run simultaneously.

The stimulation patterns from the list will be applied one after the other and change every time the start condition defined for Stimulus 1 occurs and all three stimulator units are idle, as described above. When the end of the list is reached, the software jumps back to the first pattern and continues. When the “Restart” button is pressed, the software jumps to the first entry in the list, respectively.

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