Data Acquisition PackageThe standard package includes...
Additional features included with Electrophysiology Tools
- Test pulse measures electrode resistance, cell capacitance, etc.
- Monitor electrode series resistance during acquisition
- P over N leak subtraction
- Real-time population spike slope measurement
The chart and scope programs were designed to emulate familiar laboratory instruments. The digital chart recorder displays signals in a scrolling graph window. The display range can be changed on the fly, without interrupting the recording. Event "tags" can be added to the chart record, with associated comments. The chart program can deliver a regular stimulus or timing pulse to a selected output channel. It can emulate a digital tape recorder by acquiring continuous signals at audio frequencies.
Continuous recording in Chart mode
The digital oscilloscope features a storage mode, signal averaging and real-time baseline subtraction (emulates AC coupling but with no signal distortion). The display range can be changed on the fly using "hot-keys". Sweeps can be triggered at regular intervals or when a signal on any channel crosses a specified threshold. The scope program can deliver a stimulus pulse to a selected output channel during each sweep.
Monitor brief signals in Scope mode
Test-Pulse Window Monitors the Seal Resistance or Cell Membrane Parameters
The test-pulse window is a useful tool for electrophysiologists. It can monitor patch electrode resistance during seal formation, or it can monitor the electrical parameters defining the quality of a whole-cell recording. These are the electrode series resistance, the membrane resistance and capacitance of the cell. The test-pulse program estimates these parameters by fitting an exponential (shown in red) to the decaying phase of the response to a voltage-clamp step.
Test Pulse monitors passive electrical properties of a neuron
Data Acquisition with Flexible Stimulus Patterns and P/N Leak Subtraction
The most sophisticated component of the data acquisition package is the protocol-driven acquisition program. It can monitor and record signals from up to 12 input channels (8 ADC and 4 TTL), while sending a complex series of waveforms to 8 output channels (4 DAC and 4 TTL). Data acquisition is controlled by a "protocol", which is simply a graph file that contains a series of output waveforms. It also contains instructions about which input channels to record signals from, how many episodes to acquire, etc.
Example protocols supplied with AxoGraph X demonstrate many of the available features.
There are protocols for...
- delivering a regular stimulus while monitoring response amplitude
- recording the current-voltage relationship while performing online I-V analysis
- delivering a "chirp" output waveform (modulated sinusoid)
- induction of long term synaptic potentiation (LTP)
- and many more
Protocols can be linked together in a chain so that they execute one after another. This permits the design of complex stimulus and recording paradigms.
Protocol-driven acquisition:
A series of voltage steps produce a characteristic current response
Online Analysis : Current-Voltage Curves Generated Automatically from Acquired Data
Protocols can be set up to perform online analysis at selected time points during the acquisition. Several online analysis programs are supplied, together with example protocols demonstrating their use. The analysis programs can be modified or extended using the built-in programming environment.
This current-voltage plot was generated automatically
as soon as the stimulus protocol completed
Hot-Keys
Hot keys are used to adjust the y-axis range of the scope or acquisition monitor during data acquisition (online). Click the "Hot Keys" button in the Acquisition toolbar for a complete list of the revised online hot keys.
Acquisition hot-key help window
Telegraphs
AxoGraph X (with Electrophysiology Tools pack) can automatically determine the gains on input channels when acquiring data from a supported patch-clamp amplifier. This is done by reading 'telegraphs' from the patch-clamp device. Telegraphs can be voltage signals read from analog input channels, or messages sent from the program controlling the patch-clamp.
The AxoGraph X Data Acquisition system supports the following digitizers...
Instrutech ITC-16, ITC-18 and ITC-1600 digitizers. Older Instrutech digitizers may not be compatible with the PCI-X bus found in PowerMacs manufactured from early 2005, or the PCI-express bus in Macs manufactured from early 2006. Instrutech sell a 'universal' PCI adaptor card that works with PCI and PCI-X. A USB-2 adaptor is available for the ITC-16 and ITC-18 (pre-2005 Macs do not directly support USB-2, but a USB-2 interface card can be installed in a PCI slot).
Digidata 1320 Series digitizers from Axon Instruments / Molecular Devices Corp (MDC). This is a legacy device, as the 1320 series is no longer sold by MDC. The Digidata shipped with a PCI SCSI adapter that is compatible with Power Macs purchased before mid-2005. Newer PowerMacs and Intel-based MacPros have either a PCI-X bus or a PCI-express bus, which are not supported by MDC. However, compatible 3rd party PCI-X and PCI-express SCSI interface cards are available for around US$250-$450. Suggestions on where to purchase, and how to install these interface cards are included with AxoGraph X.
Digidata 1440A digitizer from Axon / MDC is currently supported by AxoGraph X for Windows XP, but is not supported by AxoGraph X for OS X. Work has begun on an OS X driver for this device, and it should be complete in 1st quarter 2008. We are also working to add support for a range of National Instruments digitizers, and are targetting early 2008.
If no digitizer is installed, the Data Acquisition Package will run in demonstration mode, which simulates a whole-cell voltage-clamp recording. All acquisition features are available in demo mode, and most of the example protocols can be run.
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