Intensive Foreign Language Learning Reveals Effects on Categorical Perception of Sibilant Voicing After Only 3 Weeks.

Models of speech learning suggest that adaptations to foreign language sound categories take place within 6 to 12 months of exposure to a foreign language. Results from laboratory language training show effects of very targeted training on nonnative speech contrasts within only 1 to 4 weeks of training. Results from immersion studies are inconclusive, but some suggest continued effects on nonnative speech perception after 6 to 8 years of experience. We investigated this apparent discrepancy in the timing of adaptation to foreign speech sounds in a longitudinal study of foreign language learning. We examined two groups of Danish language officer cadets learning either Arabic (Modern Standard Arabic and Egyptian Arabic) or Dari (Afghan Farsi) through intensive multifaceted language training. We conducted two experiments (identification and discrimination) with the cadets who were tested four times: at the start (T0), after 3 weeks (T1), 6 months (T2), and 19 months (T3). We used a phonemic Arabic contrast (pharyngeal vs. glottal frication) and a phonemic Dari contrast (sibilant voicing) as stimuli. We observed an effect of learning on the Dari learners' identification of the Dari stimuli already after 3 weeks of language training, which was sustained, but not improved, after 6 and 19 months. The changes in the Dari learners' identification functions were positively correlated with their grades after 6 months. We observed no other learning effects at the group level. We discuss the results in the light of predictions from speech learning models.

Eye movement suppression interferes with construction of object-centered spatial reference frames in working memory.

The brain's frontal eye fields (FEF), responsible for eye movement control, are known to be involved in spatial working memory (WM). In a previous fMRI experiment (Wallentin, Roepstorff & Burgess, Neuropsychologia, 2008) it was found that FEF activation was primarily related to the formation of an object-centered, rather than egocentric, spatial reference frame. In this behavioral experiment we wanted to demonstrate a causal relationship between eye movement control and manipulation of spatial reference frames. Sixty-two participants recalled either spatial ("Was X in front of Y?") or non-spatial ("Was X darker than Y?") relations in a previously shown image containing two to four objects, each with an intrinsic orientation and unique luminance. During half of all recall trials a moving visual stimulus was presented, which participants had to ignore, thus suppressing eye movement. Response times were significantly slower for spatial relations with distraction while there was no effect on non-spatial relations. There was no effect on accuracy, i.e. WM maintenance. This is consistent with the hypothesis that in spatial representations the FEFs are involved in WM content manipulation, such as establishing an object-centered spatial frame of reference.

Amygdala and heart rate variability responses from listening to emotionally intense parts of a story.

Emotions are often understood in relation to conditioned responses. Narrative emotions, however, cannot be reduced to a simple associative relationship between emotion words and their experienced counterparts. Intensity in stories may arise without any overt emotion depicting words and vice versa. In this fMRI study we investigated BOLD responses to naturally fluctuating emotions evoked by listening to a story. The emotional intensity profile of the text was found through a rating study. The validity of this profile was supported by heart rate variability (HRV) data showing a significant correspondence across participants between intensity ratings and HRV measurements obtained during fMRI. With this ecologically valid stimulus we found that narrative intensity was accompanied by activation in temporal cortices, medial geniculate nuclei in the thalamus and amygdala, brain regions that are all part of the system for processing conditioned emotional responses to auditory stimuli. These findings suggest that this system also underpins narrative emotions in spite of their complex nature. Traditional language regions and premotor cortices were also activated during intense parts of the story whereas orbitofrontal cortex was found linked to emotion with positive valence, regardless of level of intensity.

BOLD response to motion verbs in left posterior middle temporal gyrus during story comprehension.

A primary focus within neuroimaging research on language comprehension is on the distribution of semantic knowledge in the brain. Studies have shown that the left posterior middle temporal gyrus (LPMT), a region just anterior to area MT/V5, is important for the processing of complex action knowledge. It has also been found that motion verbs cause activation in LPMT. In this experiment we investigated whether this effect could be replicated in a setting resembling real life language comprehension, i.e. without any overt behavioral task during passive listening to a story. During fMRI participants listened to a recording of the story "The Ugly Duckling". We incorporated a nuisance elimination regression approach for factoring out known nuisance variables both in terms of physiological noise, sound intensity, linguistic variables and emotional content. Compared to the remaining text, clauses containing motion verbs were accompanied by a robust activation of LPMT with no other significant effects, consistent with the hypothesis that this brain region is important for processing motion knowledge, even during naturalistic language comprehension conditions.