The Perception of Korean laryngeal contrasts by native speakers of English:
evidence from an fMRI study
It has long been observed that adult speakers have considerable difficulty recognizing
nonnative allophones which correspond to a single phoneme or phonetic category in their own
languages (as first reported by Lado 1957, followed up experimentally by Eckman et al. 2003).
Recent fMRI (functional Magnetic Resonance Imaging) studies demonstrated a measure of
reorganization in the brain regions involving specifically the learning of nonnative Hindi
dental-retroflex contrasts (Golestani & Zatorre 2004) and Mandarin lexical tone distinctions
(Wang et al. 2003). However, these studies revealed that, after learning the nonnative sounds,
the second-language speakers produced no significant difference in brain activation regions
from native-language speakers when both groups performed a perception task. Conversely,
Callan et al. (2004) compared brain activation patterns directly involving perception of the
English /r/-/l/ contrast between English native speakers and Japanese native speakers who had
learned to perceive the English liquid contrast over a period of one month. Unlike Golestani &
Zatorre (2004), Callan et al. found a result which seems to support their ‘Internal Model’ of
neurolinguistic organization, because the Japanese learners of the nonnative sounds, through
training, produced a different activation pattern in the brain from the native English speakers.
The Internal Model is a mechanism that simulates how various mappings between different
brain regions are used for identifying difficult second-language phonetic contrasts.
The present study contributes to this discussion by comparing brain activational patterns
between native speakers of Korean and adult English speakers who have learned the Korean
three-way laryngeal phoneme contrasts of tense /p’ t’ k’/ vs. lax /p t k/ vs. aspirated /ph th kh/.
The study localized the brain regions involved in the learning of these famously difficult
phonetic categories, and investigated whether there is support for the Internal Model that
Callan et al. (2004) proposed. The results of the experiment show that there is a significant
difference in activation between the native and the second-language speakers, consistent with
the findings of Callan et al. (2004). The results also indicate, however, that perceptual
identification of nonnative phonemes does not necessarily involve regions of the brain thought
to instantiate articulatory-auditory and articulatory-orosensory internal models. This is
because activation not only in STG, the region involved with auditory-speech representation,
but also activation in the left posterior STG and PT, the regions involved with auditoryarticulatory gestural speech representation, is not found. Callan et al. (2003, 2004) argued that
the cerebellum is involved with instantiating articulatory-auditory and articulatory-orosensory
internal models, but present findings suggest that the cerebellum may be involved with
controlling the larynx along with the somatosensory association cortex (BA7) and orosensory
areas in the SMG (BA40); this is supported by the fact that the cerebellum is considered to be
a region of the brain that plays an important role in the integration of sensory perception and
motor output (Grodd et al., 2001; Wildgruber et al., 2001). Thus, the current results are not
completely consistent with the Internal Model and suggest that the left posterior STG is
involved only with oral gesture representation in speech, not with laryngeal gestures.
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