[Neuroscience] Re: Neuronal activity in the brain
(by tofijoy from yahoo.co.in)
Sun Oct 22 14:20:28 EST 2006
Thank you for your reply, and sorry about using loose terminology in my
question. I hope I am making myself clear in the following.
We know that the primary sources of electrical currents in the brain are the
pyramidal cells in the cortex. We also see that the pyramidal cells are
normally oriented to the cortical surface. Suppose that a particular portion
of the cortex (a cortical patch) is activated during a task. Suppose we
measure the *current density* normally oriented to the cortical surface at
various locations in the patch. Now, will the amplitudes of the current
density be maximum at the center of the patch and slowly decline as we move
along the cortical surface away from the center?
Thank you very much
"Matthew Kirkcaldie" <m.kirkcaldie from removethis.unsw.edu.au> wrote in message
news:m.kirkcaldie-B07890.10410122102006 from news.sydney.pipenetworks.com...
> In article <ehdkh3$are$1 from mailhub227.itcs.purdue.edu>,
> "Fijoy George" <tofijoy from yahoo.co.in> wrote:
>> Hi all,
>> Would someone be able to help me with the following question?
>> When we look at the neuronal activation areas in Functional Magnetic
>> Resonance Images obtained from various experiments, we see that in each
>> area, the activity is most intense at the center and slowly declines
>> the boundary. Now, suppose we were to actually measure the neuronal
>> in the activation areas. Will the current amplitudes follow the same
>> pattern? That is, will the current amplitudes be highest near the center
>> the area, and smoothly decline toward the boundary?
>> Thank you very much
> Fairly unlikely, in my estimate. The nearest correlate to fMRI signal I
> know of is firing rate in neurons, but the decrease at the edges of the
> fMRI signal is likely to be a combination of measurement artifact
> (limited resolution of the technique) and the anatomy of the blood
> vessels - in particular, anastomoses between vessels, spreading
> increased blood flow around the activated area. I'm not exactly sure
> what you mean by "neuronal currents" - firing rates? Evoked
> potentials? More info would allow a better answer.
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