Noise! The bane of many neurophysiologists' existence! Here, we go over some
common sources of noise related to the SpikerBox.
The recording electrodes are not connected to any preparation,
so when you turn it on, all you hear is an open-circuit squelch.
Remind you of the World Cup, anyone?
I have a cockroach leg attached to my SpikerBox,
It's been there about three days, so it's dead.
I also have a speaker attached to make the spikes louder for you to hear.
But how come we don't hear any spikes?
Beyond the occasional capacitor pop and some low level noise,
you don't hear much of a response when I touch the leg.
That's because the neurons are dead.
I placed a fresh cockroach on my SpikerBox,
but what is that dreadful humming?
That humming you're hearing is the 60 Hz line noise that's running through all
powered equipment plugged into the electrical sockets on your wall
So I'm moving the soldering iron away from the SpikerBox and turning it off.
Turning off the fluorescent lights as well as turning off all powered appliances
plugged into the wall around my desk, so now the only thing running is the SpikerBox
and the battery-powered speaker. Notice how clean and crisp the spikes sound.
As a rule, turn off all devices plugged into the wall sockets around your SpikerBox.
Now that's a response!
Our modern age, with all its lovely technology!
You can now use your iPhone to record spikes.
Whoa, what was that?
When you receive text messages,
the 3G network that you're receiving those calls on -and messages- is interfering
with the amplifier of the SpikerBox.
Whoa, there we go again! So how can you record your spikes without having all this
3G network noise interfering with the amplifier sensitive electronics?
You do what you do when you're on an airplane: You simply put it on airplane
mode so that the 3G network is no longer interfering with the SpikerBox.
Using my special iPhone Cable I now have my SpikerBox connected
directly to my iPhone.
So fresh, so clean!
For those of you interested in recording spikes on your laptop,
here is a trick that will vastly improve the signal-to-noise ratio of the signal
going into the line-in of your laptop.
Unscrew the fasteners holding your SpikerBox together,
pop off the lid to expose the guts of your SpikerBox. Now, remove
the speaker connection from the connection on the SpikerBox board.
Put your SpikerBox back together and go grab your laptop.
This trick only applies to those who bought a SpikerBox prior to august 2010;
if you purchased one afterwards,
you do not need to go through this.
Now, you can see the LED of your SpikerBox is on,
but we're not hearing anything because we remove the speaker connection.
I now take a standard headphone jack cable, plug it into the line-out of the SpikerBox,
and into the line-in of the laptop, and I fire up my free favorite software,
Audacity.
Let's hit record!
Whoa, that doesn't sound good at all!
But Wait!Remember what I said about the 60 Hz line noise?
Let's remove the power connector to the laptop so it's now running on battery power alone.
Pretty good, but not perfect. Oh! if we turn up the LCD monitor up to maximum brightness,
we remove all noise associated with LCD flicker,
and now the spikes are coming through loud and clear.
And if I touch the leg with a stick,
Look and hear those robust responses!
The SpikerBox is a wonderful tool for probing the mysteries of neurons, but it is a sensitive
scientific instrument, and care must be taken to ensure what you're hearing and recording
is real nervous system activity.
We're working hard to continually improve the signal-noise ratio of our SpikerBox,
and we look forward to, and have already heard, suggestions from you out there on how to
make your neurons as clean and crisp as possible.