[Eeglablist] Average reference issue (channels become flat)

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Mon Oct 30 18:49:16 PDT 2017

Hello Ramtin, some quick suggestions below..please let the list know if you
come up with some good solutions/reasons.

Check out chapters on referencing in handbooks from Luck and from Mike X
Review articles on referencing and referencing issues.
Flatter channels are not unusual both before and after rereferencing.
Central channel when used as reference can also often be flat.
Overall this should not be a big problem for you, I'd recommend dropping
any flat looking channels unless you have a principled reason to keep them.
Google past eeglablist posts that may have dealt with this topic.

On Thu, Oct 26, 2017 at 6:44 AM, Ramtin Mehraram (Student) <
R.Mehraram2 at newcastle.ac.uk> wrote:

> Good evening,
> I am finding an issue cleaning some resting state data acquired with a 128
> channels ANT cap. The signals are initially referenced to Fz, that is
> actually flat. When I try to average re-reference, there is always one or
> two channels that become flat (usually external channels, but it happens
> also with more central ones), even if they look fine before the
> re-referencing. Is it unlikely that the activity of these channels
> corresponds exactly to the average activity of the entire scalp. What do
> you think is actually happening here?
> Thank you in advance for your help
> Ramtin Mehraram
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