Hi katrien,
> dear all,
> I have remarked something strange, with which you could possibly help
> in interpretation.
> I study bilinguals in first (L1) and second (L2) language during a
> verb generation task. I perform within-group analyses by using an
> anova. I compared several (sub)groups of L1 > L2 and L2 > L1.Only one
> particular group showed significant activation in L1 > L2. which is
> strange, because you would expect - if any - activations in L2 > L1.
> So, to double check I took a look at the 1 sampled T test of each
> group seperately. I supposed that these activations found in the
> comparison could be either (1) actual activations of L1 or (2)
> deactivated clusters in L2.
> None of the clusters could retrieved in the one-sampled-T-test of L1,
> but all four in the deactivation contrast of the 1-sampled-T-test of L2.
>
> 1- am I correct in supposing that these deactivations in L2 cause the
> activations in L1 > L2?
Yep that's right - all groups show deactivation for L2 but only one
group a significant L1>L2... Any differences between the groups for L1
or L2 only?
> 2- how to interpret these "deactivations": I realise that they can be
> interpreted as variations in the baseline/default activation of the
> brain. So that if the brain becomes "active", deactivations occur in
> unrelevant areas. However, the areas I have got are not all
> "unrelevant" to a language task (right VLPFC, left SMA, Right STG, and
> R dorsal motor/premotor)
Euh well good questions ... who knows?
I can't answer that but some papers I know could be helpful:
*1* the most famous: Gusnard, D. A. and Raichle M.E. (2001). Searching
for a baseline: functional imaging and the resting human brain. Nature
Neuroscience 2: 685-694.
*2* few sitations but nice: Frankenstein, U., A. Wennerberg, et al.
(2003). Activation and Deactivation in Blood Oxygenaion Level Dependent
Functional Magnetic Resonance Imaging. Concepts in Magnetic Resonance
16A(1): 63-70.
> any help is greatly appreciated!
If it really helps... ;-)
Best
- Cyril
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