Abstract
The structured sequence processing perspective on
language describes common aspects of processing of
language, musical and action sequences. For instance,
syntactic structure across sequences of word or word
categories enables prediction of e.g. the case of words
further down the sentence. When presenting violations
to sequential regularities in natural or artificial syntax,
a common finding is left inferior frontal gyrus (LIFG)
activation, indicating the involvement of LIFG in
structured sequence processing. However, to our
knowledge, only one FMRI-study (Nieuwland, 2011)
investigated activity by (Basque) case violations and
did not find LIFG activation. In phonology, especially
its sub-domain phonotactics, there is structure in
phoneme and syllable sequences. So far, one FMRI-study
(Vaden, 2011) investigated their brain level substrate
using a phonotactic frequency manipulation. High
(spill, probe) vs. low (sneak, jolt) phonotactic frequency
activated the anterior LIFG. The present FMRI-study
(we present results from the first 12 out of 24 planned
participants) manipulates syntactic case and phonotactics
at the sentences final noun phrase of sentences with
high cloze probability. Across participants, the same
German sentences appeared in one of three conditions:
correct, syntactically incorrect (using a case violation
on the sentence final noun phrase) and phonotactically
incorrect (using a phonotactically illegal sound cluster in
the sentence final word). A pilot study (N=5) indicated
that both phonotactic and syntactic violations would
activate the LIFG in at least one of three regions of
interest (ROIs): the pars opercularis, the pars triangularis
and the pars orbitalis. Neither of the two main effects:
syntactically incorrect vs. correct and phonotactically
incorrect vs. correct generated any significant clusters
at FWE correction 0.05 on the whole brain level. In
our planned ROI-analysis with a focus on LIFG, the
syntactic violations activated pars triangularis while the
phonotactic contrast activated pars opercularis and pars
triangularis. Our results show that phonotactic violations and syntactic case violations activate LIFG, which is
expected from the point of view that LIFG is involved in
structured sequence processing in natural language. In
our design which controlled for the exact lexical items
used, phonotactic violations resulted in activation in the
posterior LIFG. In Vaden (2011), phonotactic frequency
activated the more anterior parts of LIFG, for high vs
low phonotactic frequency. The degree of lexical control,
or alternatively our violation (rather than frequency)
manipulation, might have caused the differences. In any
case, together, these two studies provide a basis for the
study of phonotactic representation in LIFG. Since both
our phonotactic violations and syntactic case violations
activate LIFG at the group level, our paradigm provides
a good test bed for investigating neural representation
of syntax and phonotactics in LIFG at the single subject
level. The single subject approach might increase
sensitivity when testing for functional specialization.
