So do I or Neither do I ?

[martinusadjie]

Which one is correct?

I seldom visit my grandma.
~ So do I.
or
~ Neither do I.

Thank you in advance.

[Marius Hancu]

Seldom has negative connotation/value here:

>I seldom visit my grandma.

means:

I practically do not visit my grandma.

So it's neither, IMO.