Funding for this research was provided by The Garnett Passes and Rodney Williams Memorial Foundation and La Trobe University.

<ol>
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Dr. Antonio Paolini is a Director of Bioengenesis Technologies Pty Ltd who are the Australian representatives for Tucker Davis Technologies and the Australian distributor of NeuroNexus Probes.

The techniques described here provide a means for testing a range of discrimination tasks rapidly, with short training times and allowing for substantial automation, thus minimising researcher time required for data processing. Using data obtained from the implanted ECG, calculation of heart-rate (HR) change at times of stimulus presentation can be automated. Errors in ECG processing (such as missing a single heart-beat) can be easily identified as they produce spuriously large changes in apparent heart-rate for a very brief period, and such easy error detection minimises the requirement for time-intensive manual data review.
The technique described for the implantation of the ECG telemetry device consistently produces recordings with little or no interference (see Figures 1 &amp; 2). However, relatively small variations in the placement of the lead in the mediastinum region can lead to interference from nearby muscles and particular respiration-associated noise. Verifying correct placement of the leads during the implantation process, particularly after suturing leads in place, allows fine adjustments of lead placement to minimise interference.
The process of brain implantation into the cochlear nucleus is difficult. By using serial presentations of band-pass filtered noise of several frequency ranges, rather than broadband noise as has previously been used3, responses of cell populations at electrode sites can be rapidly reviewed in terms of frequency-response rather than the less-specific noise response. The ability to rapidly identify when a sufficient range of frequency-tuned cell populations are accessible is critical in research when electrical stimulus discrimination is being tested. If insufficient frequency-distribution is obtained, then comparison between stimulation of distinct frequency areas is simply not possible. Nonetheless, the longer process of frequency-amplitude response mapping remains critical to providing detail regarding the broadness of tuning of cell populations and should be performed prior to fixing the electrode in place.
In behavioral training and testing, the inclusion of a non-stimulus (or silent) period between trials, prior to stimulus onset, allows the response to initial stimulus onset to be examined. When using electrical neural stimulation, a response to stimulus onset provides evidence for the simple detection of the stimulus. Thus, when there is no stimulus onset response, but a response when the second alternation stimulus is introduced, it can be deduced that only the latter stimulus can be detected. Without inclusion of such a silent period, there would be no way to determine that the former stimulus was not detected.
A limitation in this behavioral testing technique is that the absence of foot-shocks delivered after the presentation of neural stimulation may lead to the development of specificity in conditioned fear, such that fear is only expressed when acoustic stimulus is presented. That is, the animal may learn that the particular sensory effects of neural stimulation are associated with not receiving a foot shock. In contrast, delivering foot-shocks after the presentation of neural stimulation could lead to a conditioned fear of the neural stimulus itself, distinct from any sound-like properties the neural stimulus may have. Results obtained when excluding a foot-shock after neural stimulation certainly provide stronger evidence for neural stimulus being sound-like than those using a foot-shock after neural stimulation, as in the former case conditioned fear has generalised from acoustic to neural stimulation. Nonetheless, the risk of developing specificity to acoustic rather than neural stimulation is present. The use of band-pass filtered noise as acoustic stimulus rather than pure tone bursts, the former of which may better reflect the perceptual experience of neural stimulation, could reduce the risk of such specificity developing. However, such a procedure introduces the additional variable of band-width of the filter, which will affect discrimination tasks.
An additional limitation associated with any chronic neural implantation, such as required for behavioral testing, is the change in function of the electrode or the associated neural tissue over time. Stimulation of neural tissue can lead to both temporary suppression of neural activity13 and tissue changes such as cell loss14 and direct brain tissue response to the electrode.15
The described approach to implantation and behavioral testing provides a means to test both detection and discrimination of acoustic and electrical stimuli with brief training, and the ability to exert control of trial frequency. The technique of using change in HR as a measure of conditioned fear may be applicable to not only auditory testing, but more generally to any sensory testing in which stimuli can be presented for any discrete period, and in which detection of sensory discrimination is desired.

<table border="1">
<tbody>
 <tr>
 <td>Name</td>
 <td>Company</td>
 <td>Model</td>
 <td>Comments </td>
 </tr>
 <tr>
 <td>PowerLab</td>
 <td>ADInstruments</td>
 <td>ML880</td>
 <td>Records data received from the implanted TR40 transmitter</td>
 </tr>
 <tr>
 <td>SmartCtrl controller card</td>
 <td>Med Associates</td>
 <td>DIG-716B</td>
 <td>Controls the behavioral test chamber, including foot shock</td>
 </tr>
 <tr>
 <td>Modular behavioral test chamber</td>
 <td>Med Associates</td>
 <td>ENV-009</td>
 <td>Test chamber size: 30.5cm x 39.4cm</td>
 </tr>
 <tr>
 <td>Aversive stimulus generator</td>
 <td>Med Associates</td>
 <td>ENV-410B</td>
 <td>Delivers aversive foot-shock to metal-bar floor of the cage through a Solid State Scrambler unit</td>
 </tr>
 <tr>
 <td>Programmable Attenuator</td>
 <td>TDT</td>
 <td>PA5</td>
 <td>Controls the amplitude of delivered acoustic signal to ensure stable amplitude across frequencies</td>
 </tr>
 <tr>
 <td>Electrostatic speaker driver</td>
 <td>TDT</td>
 <td>ED1</td>
 <td>Drives the electrostatic speakers (EC1, ES1)</td>
 </tr>
 <tr>
 <td>Free-field electrostatic speaker</td>
 <td>TDT</td>
 <td>ES1</td>
 <td>Sounds are presented using this speaker in the behavioral test chamber</td>
 </tr>
 <tr>
 <td>Coupled electrostatic speaker</td>
 <td>TDT</td>
 <td>EC1</td>
 <td>Sounds are presented using this speaker during neural implant surgery</td>
 </tr>
 <tr>
 <td>Stimulator Base Station</td>
 <td>TDT</td>
 <td>RX7</td>
 <td>Controls delivery of electrical neural stimulation (used with MS16)</td>
 </tr>
 <tr>
 <td>Microstimulator</td>
 <td>TDT</td>
 <td>MS16</td>
 <td>Delivers multichannel electrical neural stimulation</td>
 </tr>
 <tr>
 <td>Processing base station</td>
 <td>TDT</td>
 <td>RZ2</td>
 <td>Records neural activity during brain implantation (using PZ2 preamplifier)</td>
 </tr>
 <tr>
 <td>Preamplifier</td>
 <td>TDT</td>
 <td>PZ2-256</td>
 <td>256-channel high impedance preamplifier</td>
 </tr>
 <tr>
 <td>Telemetry device receiver</td>
 <td>Telemetry Research</td>
 <td>TR162</td>
 <td>Receives digital signal from TR40, and converts to amplified analogue output</td>
 </tr>
 <tr>
 <td>Implantable electrocardiogram telemetry device</td>
 <td>Telemetry Research</td>
 <td>TR40</td>
 <td>The implanted transmitter device, sampling at 2kHz</td>
 </tr>
 <tr>
 <td>Multifunction Processor</td>
 <td>Tucker Davis Technologies (TDT)</td>
 <td>RX6</td>
 <td>Used to generate acoustic stimuli</td>
 </tr>
 <tr>
 <td>Vertex Castavaria</td>
 <td>Vertex Dental</td>
 <td>&nbsp;</td>
 <td>Dental acrylic used to fix the electrode in place</td>
 </tr>
 <tr>
 <td>Kwik-Sil Adhesive, 
 low viscosity</td>
 <td>World Precision Instruments</td>
 <td>&nbsp;</td>
 <td>Silicon elastomer used to coat the electrode shanks</td>
 </tr>
 <tr>
 <td>Multichannel electrode</td>
 <td>NeuroNexus</td>
 <td>a2x16-10mm 
 100-500-413 </td>
 <td>The 2-shank 32-channel extracellular electrode array used for implantation. The electrode sites have been activated to produce a coating of iridium oxide in preparation for stimulation. </td>
 </tr>
</tbody>
</table>

behavioral determination of stimulus pair discrimination of auditory acoustic and electrical stimuli using a classical conditioning and heart-rate approach

Acute animal preparations have been used in research prospectively investigating electrode designs and stimulation techniques for integration into neural auditory prostheses, such as auditory brainstem implants1-3 and auditory midbrain implants4,5. While acute experiments can give initial insight to the effectiveness of the implant, testing the chronically implanted and awake animals provides the advantage of examining the psychophysical properties of the sensations induced using implanted devices6,7.
Several techniques such as reward-based operant conditioning6-8, conditioned avoidance9-11, or classical fear conditioning12 have been used to provide behavioral confirmation of detection of a relevant stimulus attribute. Selection of a technique involves balancing aspects including time efficiency (often poor in reward-based approaches), the ability to test a plurality of stimulus attributes simultaneously (limited in conditioned avoidance), and measure reliability of repeated stimuli (a potential constraint when physiological measures are employed).
Here, a classical fear conditioning behavioral method is presented which may be used to simultaneously test both detection of a stimulus, and discrimination between two stimuli. Heart-rate is used as a measure of fear response, which reduces or eliminates the requirement for time-consuming video coding for freeze behaviour or other such measures (although such measures could be included to provide convergent evidence). Animals were conditioned using these techniques in three 2-hour conditioning sessions, each providing 48 stimulus trials. Subsequent 48-trial testing sessions were then used to test for detection of each stimulus in presented pairs, and test discrimination between the member stimuli of each pair. 
This behavioral method is presented in the context of its utilisation in auditory prosthetic research. The implantation of electrocardiogram telemetry devices is shown. Subsequent implantation of brain electrodes into the Cochlear Nucleus, guided by the monitoring of neural responses to acoustic stimuli, and the fixation of the electrode into place for chronic use is likewise shown.

Watch this Scientific Journal Video about Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach at

Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach

The application of a classical fear conditioning behavioral paradigm for auditory prosthetic research in rats is described. This paradigm provides a mechanism for identifying both detection of, and discrimination between, distinct acoustic and electrical stimuli using heart-rate as an outcome measure.

Acute animal preparations have been used in research prospectively investigating electrode designs and stimulation techniques for integration into neural ...

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14.4K visualizações.  La Trobe University. A aplicação de um paradigma clássico medo condicionado comportamental para auditivo protético investigação em ratos é descrito. Este paradigma fornece um mecanismo para a identificação de ambos, detecção de e discriminação entre, acústica distinta e estímulos elétricos com freqüência cardíaca como uma medida de resultado.

Vídeo: Behavioral Determination of Stimulus Pair Discrimination of Auditory Acoustic and Electrical Stimuli Using a Classical Conditioning and Heart-rate Approach