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[Neuroscience] Re: Frequencies of impulses in brain

r norman via neur-sci%40net.bio.net (by r_s_norman At _comcast.net)
Sat Dec 9 23:11:30 EST 2006

On Sun, 10 Dec 2006 14:55:41 +1100, Matthew Kirkcaldie
<m.kirkcaldie At removethis.unsw.edu.au> wrote:

>In article <1165701310.527446.233760 At n67g2000cwd.googlegroups.com>,
> "Marcin" <marcin.gierlicki At gmail.com> wrote:
>> Hi,
>> I'm looking for informations about signals frequencies in brain
>> depending on area of it. For example range of frequencies for area
>> responsible for hearing or motor function. I need this information to
>> my master thesis about recordin extracellular signals from neuronal
>> cells.
>> Can someone help ?
>> Kind of animal dosen't matter ;)
>> Thanks,
>> Marcin
>Maximum spike rate in neurons can be up to 2kHz - I believe there are 
>phase-locked responses in cochlear afferents about this fast.
>In cortex, 500-1000 spikes per second is the upper limit.  Almost never 
>see 2 action potentials close than 1ms apart, aside maybe from burst 
>firing in a basket cell.
>In cortical extracellular recording, we typically use bandpass filtering 
>to include, say, 300Hz - 10kHz, and would generally sample at 
>10kHz-20kHz depending on specific requirements (and yes, we know about 
>Nyquist limits!).  Including lower frequencies causes a lot of baseline 
>shifts in potential to interfere with spike discrimination.  Sadly the 
>baseline shifts are probably very important to cortical function, we 
>just don't know how!

An important point to add is that the recording bandwidth has to do
with the time course of a single impulse, not the frequency of
impulses.  Although typical impulse frequencies are seldom as high as
these limits, usually below 100/sec, you still need the 10kHz
bandwidth to capture the pulse shape accurately..

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