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Customer Support News

See Us On The Road at these upcoming tradeshows ...

New Products

Multi I/O Processor - We've added a high channel count analog I/O device to our popular multiprocessor line.

Microstimulator System - New for neurophysiologists.

Microwire Arrays - Need customized electrode arrays and reliable performance? You can get both when you get your arrays from TDT.

SykofizX - Software for psychophysical experiments that supports both System 3 and System II!

Tech Talk

What is the multiprocessor advantage?

Sorting out spike sorting ....

Rubber, baby-buggy buffers?

Isn't it time to understand how sample rate relates to the time based parameters of some components?

Who is that new voice on the Tech Support line?

Customer Support News

Our customers are our most valuable assets and we are committed to offering support that is second to none. In keeping with this viewpoint, we've instituted an aggressive customer upgrade program to ensure that every TDT user has the latest hardware and software versions running in their lab. In all cases, hardware and software problem fixes are upgraded at no charge and performance upgrades are offered with generous trade-in pricing.

Engineers at TDT have spent the past five years developing some of the most innovative and powerful stimulation and acquisition systems available for research. After completing this initial period of vigorous product development, we've focused on improving the functionality and usability of our hardware and software systems.

We've addressed dozens of issues, from resolving concerns as simple as making the system fans quieter to developing powerful system extensions like our new multiprocessor devices that offer 20 fold improvements in processing capability. We've also improved reliability and functionality by reworking our PC interfaces, making them faster and more robust.

On the software front, we are implementing a two-phase program designed to first improve software design and stability, and then address ease of use and general functionality issues. The first phase is now complete and phase two is well under way.

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New Products

Multi I/O Processor

The RX8 is the newest addition to our line of High Performance Processors. The RX8 targets those needing multiple channels of analog input or output. It offers up to 24 channels configured at the factory, offering users an opportunity to mix and match inputs and outputs as well as audio and PCM converters. With a sample rate at a screaming 100 kHz, providing a functional bandwidth of 40 kHz, the RX8 add incredible versatility to the TDT System 3 line.

Depending on the configuration you choose, use the RX8 to:

• Drive speaker arrays.
• Acquire from microphone arrays.
• Drive cochlear implants.
• Control stepper motors.

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Microstimulator System

Features:

• Deliver stimuli on up to 16 channels
• Generate and process complex waveforms
• Battery-powered device operation and high voltage stimulus generation
• Delivers up to +/- 100 µA of current through a 1M load

Our new Multichannel MicroStimulator system is a programmable current stimulator that can deliver complex stimulation patterns simultaneously across multiple microelectrode channels. The system also incorporates a user-programmable DSP and multi-channel A/D input for dynamic, real-time stimulus control based on analog control signals from virtually any signal source.

Programmable DSP
This powerful system can generate complex arbitrary waveforms or be used to design and deliver complex patterns of biphasic pulses with stimulus durations of less than 50 microseconds. The system is available with either two or five cutting edge DSPs delivering exceptional processing power.

Onboard Memory
With 128 megabytes of onboard memory, you can design complex patterns offline and then upload them to the signal processor for play out.

Real-Time Processing
Alternately, the system can acquire and process signals from external devices, such as a video camera or microphone, to stimulate a prosthetic eye or ear. Acquired signals can be filtered, rectified, or smoothed for stimulus output.

Optically Isolated
A proven digital communication system optically isolates the electrical stimulator from the waveform generators to eliminate AC power surges and noise, ensuring superior performance.

Unique Stimulus Isolator Design
Capable of delivering up to 100 µAs of current simultaneously across up to 16 stimulating electrodes (impedances up to 1 M), the MS16/MS4 includes special current limiting circuitry to ensure subject safety when using low impedance electrodes.

Isolated Power Supply
The Stimulus Isolator is powered by a high voltage power supply that is housed in a separate box for easy replacement of batteries. This self-contained battery pack and the Isolator’s fiber optic connection to the processor base station allows for complete isolation between the waveform generator and stimulus delivery.

Circuit Example: Stimulation Based On Analog Input
The Multichannel MicroStimulator system can generate both the typical microstimulator stimulation patterns and the more complex stimulation patterns required for the development of neuroprosthetic devices. In the RPvds processing chain below, analog input from an A/D converter is filtered into a 100 Hz band centered at 1 kHz using the ButCoef and Biquad components.

The stimulus envelope in this band is computed through half-wave rectification and smoothing of the signal. The resulting envelope is used to control the amplitude of 200 µs stimulus pulses in real-time.

The circuit could be easily modified to allow the signal envelope to control stimulus pulse interval or duration.

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Microwire Arrays

The MW16 Microwire Array is a simple and reliable electrode for chronic multi-channel neurophysiology applications. Chronic arrays eliminate the need for anesthetized and head-fixed preparations, and allow for recording and stimulation in awake, behaving animals in naturalistic settings. In addition to greater physical and behavioral freedom, chronic arrays provide long-term access to a block of neural tissue, and increase the data yield from each valuable experimental subject.

Features:

• Customizable electrode arrays with user specified array geometry
• Reliable quality and performance
• Up to 16 channels

With over 15 years of experience in manufacturing hardware for scientific applications, Tucker-Davis Technologies has the resources to reliably deliver the arrays you depend on for your research. Our manufacturing methods produce consistent, dependable, and affordable arrays while maintaining the flexibility to build custom arrays to your specifications. With TDT microwire arrays you can design your own electrodes without the time and labor intensive task of building arrays by hand.
Microwire Array Configuration

All standard TDT microwire arrays use 50 µM polyimide-insulated tungsten microwire. This wire has excellent recording characteristics and its rigidity facilitates insertion. The standard array consists of 16-channels configured in two rows of eight electrodes each. Electrode separation is 250 µM within rows, with 500 µM separation between rows. The overall length of our standard array is about 2.5 cm, but can be customized simply by adjusting the length to which the micro-wire is cut. An optional epoxy “land” near the recording end of the array maintains electrode spacing.

Standard values are listed below. The user can request a custom value for most specifications.

n Rows X n Electrodes = [2X8] (Max rows = 2, Max channels = 16)
Metal = [Tungsten] (Metal = Tungsten)
Electrode Diameter = [0.050 mm] (Electrode diameter of 0.050)
Insulation = [Polyimide] (Insulation = Polyimide or Formvar)
Row Pitch = [0.250 mm] (Row pitches of 0.250, 0.300, 0.450 mm + multiples)
Row Distance = [0.500 mm] (Row distances at 0.05 intervals from 0.05 - 0.8 mm)
Total Length = [25 mm] (Total length 15 - 120 mm)
Tip-to-Land = [2mm] (Tip-to-Land 2-120 mm)

Looking ahead ....
We've recently expanded our R&D department allowing us to look towards expanding our microwire offerings. Tetrode, stereotrode, and high channel count microwires are currently under development.

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SykofizX

SykofizX is a comprehensive software application for designing and conducting psychophysical experiments in audition. Designed specifically for scientists conducting experiments in speech perception and psychoacoustics, it meets the needs of a wide variety of users, ranging from those who prefer a "turn-key" application to those who desire complete control over any aspect of the experimental process. SykofizX provides a powerful array of tools for customizing entire experimental designs from beginning to end,and includes standard subject interface modules suitable for testing of infant and adult human listeners as well as animal subjects.

Extensible:

• Support for TDT System II and System 3 hardware as well as APOS emulation with System 3 hardware.
• Modular architecture
• Interchangeable standard plugins
• Vast libraries of standard and customizable scripts
• Flexible data export for off-line analysis
• Support for interleaving conditions during data collection
• Fully network compatible for remote access and control
• Powerful XML data storage format
• The application derives much of its flexibility from a plugin architecture that allows the user to easily modify existing experimental designs to create novel designs with minimal effort.

Flexible:

• Run multiple subjects/experiments simultaneously using independent TDT hardware configurations
• Simultaneous use of Data Collection, Analysis, and Design modes
• Fully integrated and easy-to-use calibration mode
• Flexible subject interface configuration suitable for psychophysics and speech perception research with human adult, infant, and animal subjects
• Multiple presentation and independent variable manipulation methods
• Multiple data display features from Data Collection and Analysis modes
• Convenient evaluation utilities available from Data Collection and Design modes for verification, demonstration, and subject training
• Run conditions under random, sequential, or custom order during data collection
• Complete control over stimulus and subject response timing
• Support for .wav and other stimulus file formats
• Support for interleaved tracking

View more information about SykofizX on our Website or contact us today.

Comprehensive Software

• Experiment control
• Signal generation
• Multi-modal subject interface
• Data acquisition
• Data analysis and export
• System calibration

Standard Method Plug-ins

• Same-different
• Yes-no
• Forced-choice
• Rating
• Identification
• Categorization
• Magnitude estimation
• Magnitude production

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Tech Talk

This month our technical support team tackles some important questions, so follow the links below and get ready to absorb the expertise of our hard working gurus.

What is the multiprocessor advantage?

TDT’s Multiprocessor devices have a four-fold advantage over our single processor devices:

• A more powerful DSP runs faster and can process data more efficiently.
• Improved multi-DSP architecture allows users to realize the true transfer rate of the gigabit interface. Users can stream data at rates of 24 Megabits per second or nearly 1.2 million samples a second.
• Complex circuits can be run on a single device instead of multiple devices. This minimizes potential issues with connecting devices together, improves the design of circuits for controlling the hardware, and simplifies timing of circuits for controlling stimulation and acquisition.
• New components that run only on multiprocessors improve circuit design and streamline data processing.

Which multiprocessor is right for me?

These new processors address the full spectrum of TDT’s client base.

The RX5 Pentusa is designed for high channel count data acquisition. You can acquire up to 64 channels on a single device or tackle complex tasks or filtering across multiple channels.

The RX6 Pirhana is designed for high frequency auditory stimulation and acquisition or complex 3D audio projects. A powerful combination of increased processing power and high quality D/As and A/Ds makes this device ideal for researchers generating auditory stimuli for bats, mice, or other animals with high frequency hearing.

The RX7G is a multichannel microstimulator capable of delivering complex stimulation patterns simultaneously across multiple microelectrode channels. The system incorporates the RX7 programmable base station and multi-channel A/D input for dynamic, real-time stimulus control based on analog control signals from virtually any signal source.

The RX8 is a generic Analog I/O device for users that require high channel generic I/O (+/- 10V). The system design allows users to configure the type of I/O at the factory. TDT has designed the system to use both Sigma-Delta (24-bit high quality audio DA/AD) and PCM (16-bit AD/DA with no group delays). With this processor you can generate or acquire high quality audio signals on the same device you use to control audio feedback systems or motor controls in real-time.

How difficult is it to migrate to the new processors?

Migration should be painless, but we are always here to help if you need us.

The multiprocessor devices are part of the System 3 hardware line and are supported by our popular RPvds graphical programming interface and OpenEx software platform. Most users are able to migrate to the new device with little or no change to existing software. Multiprocessors support previous RPvds components and new multi-channel and multiprocessing components that streamline development of new processing chains.

Are multiprocessors affordable?

With all this power, you’ll be surprised just how affordable they are. For multi-channel or complex tasks, the price advantage over single processors is phenomenal. Because one multiprocessor device can do the work of many single processor devices upgrading is very affordable. TDT also offers generous trade-in pricing program for users who wish to replace existing single processor devices with the new multiprocessor alternative.

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Sorting out spike sorting ....

Each of the spike discrimination components available in RPvds has advantages and disadvantages. Let's take a moment to look at two spike sorting components supported by OpenEx, SortSpike and SortSpike2.

Both of these components allow online real-time spike sorting using a fixed voltage window discriminator for spike detection and time-voltage window discriminators for spike sorting. They differ, however, in several important ways. SortSpike offers artifact rejection while SortSpike2 supports biphasic spike acquisition. If either of these factors is critical in your research then the choice is clear. Perhaps most significant, however, is how the captured signal is stored in the buffer.

SortSpike centers the peak of the waveform and uses this value as the time stamp for the signal. The position of the discriminator does not affect the position of the waveform in the buffer. Because SortSpike uses the peak of the signal as the center, variation in signal amplitude due to the ambient background noise may shift the true peak of the waveform. This jitter will cause minor variation in the time stamp of the signal and may affect the acquired signal since the position of the waveform is dependent on the peak signal. The noisier the signal, the greater the effect.

The time stamp and position of the waveform for SortSpike2 is dependent on the time of the threshold crossing for the signal. As a result, signals that differ in shape may have their peaks at different positions in the buffer. If it is important for the time stamp to be relative to the peak of a waveform then it may be necessary to calculate a new time stamp offline. Changing the position of the discriminator can also affect the positioning of a signal in the buffer. For example, setting the signal to noise of the threshold relatively low shifts the time stamp to an earlier point (since the signal crosses the threshold earlier) and shifts the peak to a later point.

The comparison chart below will give you a quick overview of the comparison points discussed in this article. See your OpenEx Help for more information on spike detection components and how they are implemented in OpenEx.

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Rubber, baby-buggy buffers?

Which is more challenging? Understanding the various RPvds buffer components or saying rubber baby-buggy bumpers three times fast? By the end of this article, it's sure to be the bumpers, not the buffers.

RPvds includes different buffer components to meet the specific needs of researchers doing many different types of tasks. Let’s take a look at some of their distinguishing properties.

Averaging Buffers
AvgBuf and AvgBuf2 buffers are aimed specifically at performing online averaging of signals. AvgBuf implements a summer in memory for basic signal averaging. AvgBuf2 sums two alternating signals, acquired on a single input line and provides the user with additional features and control, such as allowing for variable buffer size and artifact rejection.

Random Access Buffers
The RamBuf component allows access to any arbitrary point in a buffer. It increases the flexibility in circuit design. It allows the user to load a large buffer with all the signals concatenated and then access any signal by going to the specific point in the buffer where the signal of interest starts. One of its most useful features is that it allows simultaneous read and write access to the same buffer.

Snippet Buffers
The SnipStore component stores a snippet of data with half the number of points before the trigger and half the points after a trigger. This makes it useful for storing data where the values before the trigger are important, such as significant unexpected spike artifacts. It also has a tag input which is stored at the start of every block. This is usually used for storing timestamps. Despite its name, SnipStore is not commonly used to store spike data, which can be stored more effectively using a spike sorting component and a serial store.

Serial Buffers
While two of the most commonly used buffers – SerialBuf and SerSource – seem similar in function, they have subtle yet important differences. The main difference is that that the SerSource allows only read operations, while the SerialBuf allows both read and write operations.

The SerSource buffer loads the first value of the buffer at run. When IdxEnab goes high, it retains the first value for the length of the first sample pulse. At the end of that sample, when the trigger goes low, it then loads the next value and awaits the next trigger. So the point of loading a new value as output is the falling edge of the trigger.

SerialBuf works differently. The SerialBuf buffer gets loaded with the first value only when the enable line is triggered. It then retains the same value until the next trigger. So the point of change is the rising edge of the trigger.

These subtle differences often mean you’ll need to build your circuit differently depending on the buffer you use. For example, when using a SerSource, a latch triggered by the same pulse that triggers the SerSource’s enable line should be used at the SerSource’s output.

In the RPvds Component Reference, you’ll find detailed information on each buffer component as well as a comparison chart to help you decide which component is right for your task.

Note: You'll also find the comparison chart and buffer descriptions in the online version of the TDT help.

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Isn't it time to understand how sample rate relates to the time based parameters of some components?

The time based parameters of PulseTrain, Schmitt, and TTLDelay components are directly related to the sampling period.

When using RPvds components that define a high, low, or delay period based on time, such as PulseTrain, Schmitt, and TTLDelay, there is always a fixed difference between expected and actual values that relates to the sample period (inverse of the sample rate). The maximum possible difference with these components is +/- the sample period . The table below shows the possible difference at different sample rates.

The actual length of time that the component will remain high is the multiple of the sample period that is the closest to the set time. For example, the table below assumes that a component, such as a PulseTrain, is set to go high for 2 ms. The actual time that the PulseTrain would remain high and the expected difference are in the final two columns.

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Who is that new voice on the Tech Support line?

Many of you might have noticed there is a new kid on the block in Tech Support. Taryn, our newest addition, graduated from Arizona State University with a BS in Bioengineering and an emphasis on biomechanics. Most recently, she worked and volunteered in the ASU Adaptive Neural Systems Laboratory studying how spinal cord injuries affect balance control.

Despite delays in getting her furniture shipped cross-country and arriving in Florida to face three back-to-back hurricanes, she is settling in nicely. The rest of the support team is thrilled to have another great problem solver onboard.

"Taryn is professional and amazingly comfortable with her multi-cultural colleagues," said Madhu, who celebrated her one year anniversary with TDT earlier this Fall. With an undergraduate degree in Biomedical Engineering from Bombay University and a Masters in Biomedical Engineering at the University of Wisconsin, Madhu fast became our OpenEx guru.
VJ, our Tech Support veteran, seems happy to have Taryn helping out as well. "If only she knew APOS," said VJ.

Ever wonder why our new support staff is always so knowledgeable? It is all due to our three step approach. First, we set high standards during hiring. Second, each new team member goes through an intense training program before they ever speak to a customer. Finally, they always have the support of veteran Tech Support team members and, of course, our Staff Scientists.

Know someone who would make a great TDT Tech Support person? We are still hoping to expand our team by one more person, so send them a link to our Website. Sorry, no finder's fees, but you might get priority help if you end up with a friend on the inside.

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