Biomedical subjects

Patrick C M Wong

Publications and source records attributed to Patrick C M Wong.

5 recordsLinked to original sources

PubMed2007

Neural characteristics of successful and less successful speech and word learning in adults.

A remarkable characteristic of the human nervous system is its ability to learn to integrate novel (foreign) complex sounds into words. However, the neural changes involved in how adults learn to integrate novel sounds into words and the associated individual differences are largely unknown. Unlike English, most languages of the world use pitch patterns to mark individual word meaning. We report a study assessing the neural correlates of learning to use these pitch patterns in words by English-speaking adults who had no previous exposure to such usage. Before and after training, subjects discriminated pitch patterns of the words they learned while blood oxygenation levels were measured using fMRI. Subjects who mastered the learning program showed increased activation in the left posterior superior temporal region after training, while subjects who plateaued at lower levels showed increased activation in the right superior temporal region and right inferior frontal gyrus, which are associated with nonlinguistic pitch processing, and prefrontal and medial frontal areas, which are associated with increased working memory and attentional efforts. Furthermore, we found brain activation differences even before training between the two subject groups, including the superior temporal region. These results demonstrate an association between range of neural changes and degrees of language learning, specifically implicating the physiologic contribution of the left dorsal auditory cortex in learning success.

Acoustic Stimulation↗

PubMed2004

The role of the insular cortex in pitch pattern perception: the effect of linguistic contexts.

Auditory pitch patterns are significant ecological features to which nervous systems have exquisitely adapted. Pitch patterns are found embedded in many contexts, enabling different information-processing goals. Do the psychological functions of pitch patterns determine the neural mechanisms supporting their perception, or do all pitch patterns, regardless of function, engage the same mechanisms? This issue is pursued in the present study by using 150-water positron emission tomography to study brain activations when two subject groups discriminate pitch patterns in their respective native languages, one of which is a tonal language and the other of which is not. In a tonal language, pitch patterns signal lexical meaning. Native Mandarin-speaking and English-speaking listeners discriminated pitch patterns embedded in Mandarin and English words and also passively listened to the same stimuli. When Mandarin listeners discriminated pitch embedded in Mandarin lexical tones, the left anterior insular cortex was the most active. When they discriminated pitch patterns embedded in English words, the homologous area in the right hemisphere activated as it did in English-speaking listeners discriminating pitch patterns embedded in either Mandarin or English words. These results support the view that neural responses to physical acoustic stimuli depend on the function of those stimuli and implicate anterior insular cortex in auditory processing, with the left insular cortex especially responsive to linguistic stimuli.

Adolescent↗

PubMed2004

Neural bases of talker normalization.

To recognize phonemes across variation in talkers, listeners can use information about vocal characteristics, a process referred to as "talker normalization." The present study investigates the cortical mechanisms underlying talker normalization using fMRI. Listeners recognized target words presented in either a spoken list produced by a single talker or a mix of different talkers. It was found that both conditions activate an extensive cortical network. However, recognizing words in the mixed-talker condition, relative to the blocked-talker condition, activated middle/superior temporal and superior parietal regions to a greater degree. This temporal-parietal network is possibly associated with selectively attending and processing spectral and spatial acoustic cues required in recognizing speech in a mixed-talker condition.

Acoustic Stimulation↗

PubMed2003

Perceptual normalization for inter- and intratalker variation in Cantonese level tones.

Inter- and intratalker variation in the production of lexical tones may contribute to acoustic overlap among tone categories. The present study investigated whether such category overlap gives rise to perceptual ambiguity and, if so, whether listeners are able to reduce this ambiguity using contextual information. In the first experiment, native Cantonese-speaking listeners were asked to identify isolated Cantonese level tones produced by 7 talkers. Identification accuracy was significantly higher when the presentation of items was blocked by talker rather mixed across talkers. In the second experiment, listeners identified the final (target) tone of 6-syllable semantically neutral sentences with f0 patterns of the context (i.e., the first 5 syllables) altered. The same target tone was identified differently depending on the context. In the third experiment, the context portions of stimulus sentences from the second experiment were divided into 2 halves, and their f0 patterns were altered independently. In identifying the target tone, listeners relied more heavily on the f0 pattern of the second (last) half of the context. These results are discussed in relation to characteristic inter- and intratalker variations of lexical tones.

Analysis of Variance↗

PubMed2002

Hemispheric specialization of linguistic pitch patterns.

Pitch is used to signal different aspects of language such as speaker identity, intonation, emphatic stress, and word identity (as signaled by lexical tones). This article reviews research studies investigating hemispheric specialization of these pitch patterns in the context of two competing hypotheses. The functional hypothesis states that pitch patterns are lateralized to different hemispheres of the brain depending on their functions. Those pitch patterns that carry a greater linguistic load (e.g., lexical tones) are lateralized to the left hemisphere, while those that carry a less linguistic load (e.g., intonation patterns signaling affective moods) are lateralized to the right hemisphere. The alternative hypothesis, the acoustic hypothesis, states that all pitch patterns, regardless of their functions, are lateralized to one hemisphere (the right hemisphere in particular). Although most researchers support the functional hypothesis, a comprehensive review, which includes lesion, dichotic-listening, and functional imaging studies of different types of pitch patterns, does not support this view. Moreover, little evidence exists for the alternative hypothesis. Possible methodological problems of these studies, alternative hypotheses, and considerations for future research are noted.

Functional Laterality↗