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From the vault…

At the start of 2019, our first newsletter featured three new publications on the auditory system - a nod to the upcoming Association for Research in Otolaryngology meeting that took place in person in Baltimore that month.

The benefit of NeuroNexus probes for this work is the consistent layout of electrode sites on silicon probes. The researchers all used linear arrays, for example spaced every 50um for recordings in mouse, and spaced every 100um for recordings in guinea pig. Both of these options are standard in the NeuroNexus catalog.

In two of the studies, the linear arrays were inserted along the tonotopic axis in the inferior colliculus, enabling recording of single neurons from multiple isofrequency bands. What this means is that NeuroNexus probes enabled the researchers to sample neuronal activity throughout a particular region of the brain that is sensitive to sound. Different neurons in that region are activated by different frequencies; each individual neuron responds to a narrow frequency band and is characterized by just one "best frequency". The neurons in the inferior colliculus are arranged in order by their best frequency, and a linear microelectrode array can be inserted along that arrangement to sample from neurons with as many different best frequencies as possible.

With this setup, one study compared neuronal activity in response to frequencies above and below a particular frequency that was used to induce hearing loss. The other study determined that the neuronal arrangement in the inferior colliculus was altered if a specific step in auditory system development was disrupted.

The third publication we featured was a great reminder to our staff in the office and our Neuroscientist colleagues alike that NeuroNexus probes can be used in a very wide range of research models. The researchers used several probe designs to record from auditory cortices in the zebra finch and studied the processing stages of song.

Bonus Tip: Probe Insertion

Our January 2019 product feature addressed the challenge of penetrating the dense surface of the brain. While we recommend performing a durotomy prior to probe insertion, the pia exhibits some resistance and so causes the underlying tissue to dimple beneath a probe. In our experience, if you pause insertion and wait a few minutes, the probe will work itself into the tissue and you can be on your way. We also get asked to sharpen probe tips for certain applications.

The NeuralGlider by Actuated Medical is a device that produces tiny vibrations along the axis of the probe to facilitate insertion without dimpling. This is especially advantageous for recordings in superficial regions where dimpling could put pressure on the tissue of interest, or could cause the probe to insert past the target and have to be retracted. We are happy to be able to rent out a NeuralGlider to interested labs.