音高訊息的辨識是人類聽覺系統在解析語音聲調及音樂旋律中非常重要的一環。而在辨認音與 音之間的高低關係時，可以使用絕對音高或相對音高的資訊來進行。本計畫利用心理物理學實驗法 及功能性核磁共振腦造影方式探討具有絕對音感和相對音感者在視唱音高及使用音高與語意符號之 連結時的相關腦神經機制。另外，也探討學齡前兒童較偏向使用絕對或相對音高的資訊來表徵旋律 和語音中的音高訊息。由於目前音感方面的腦造影研究大多為知覺性的聽音辨識，探討發聲哼唱的 研究則相對較少。另一方面，音名符號與音高之間的連結所對應的腦神經迴路目前在文獻上仍有爭 議。本計畫第一組的實驗是研究絕對音感與相對音感者在視唱獨立音高時的工作記憶與語意相關腦 神經迴路活化型態，並比較使用不同的音名系統(固定音名及首調音名)來視唱獨立音高時所對應到 的腦區。第二部分研究則探討音高與音名符號系統的連結強度不同，如何反應在記憶與語意相關腦 區活化層度。此部分實驗利用訊號處理方式創造一組音名符號與音高不相符的聲音刺激，藉以探討 絕對音感和相對音感的受試者在聆聽音名與音高匹配/不匹配的聲音刺激時產生的腦神經活化層 度。最後一組實驗將利用心理物理學實驗法來評估學齡前兒童是否較依賴絕對或相對音高的資訊來 辨認旋律中的音高訊息。實驗中針對改變旋律音程的走向(上下行)、音程變化的速率、及音高所在 的頻率區段等，探討是否會影響不同年齡層的兒童區辨音程及語音中音高的關係。 ;This project investigates the functional properties of vocal-motor and language-related cortical regions involved in retrieval and production of musical pitch from long-term auditory memory using psychophysical and functional neuroimaging (fMRI) approaches. Despite a recent upsurge in neuroimaging research on musical pitch processing, comparatively little is known about cortical activation patterns underlying production of musical pitch either vocally or through other perceptual auditory mechanisms. Studies that probed possible brain mechanisms underlying the association between linguistic tokens and musical pitch has also yielded inconsistent conclusions. We hypothesized that distinct neural networks modulated by language-specific components underlie a dissociation between motor and perceptual mechanisms in accessing musical pitch memory. Part I of the proposed research examines cortical activation patterns associated with vocal and non-vocal pitch production by absolute-pitch and relative-pitch musicians. Visually presented musical notes will be sung with pitch names involved in different solmization systems (i.e., fixed-Do and movable-Do systems) to contrast brain activation patterns underlying vocal-pitch production with congruent and incongruent labels. Part II of the proposed research aims to identify language-modulated cortical regions subserving the use of linguistic symbols in facilitating retrieval and labeling of musical pitch from long-term memory. Novel “hybrid” stimuli consisting of incongruent linguistic and pitch cues will be employed to contrast activities in cortical regions underlying perception of unexpected linguistic information during retrieval of musical pitch by musicians trained in different solmization systems. The last set of experiments will use psychophysical procedures to assess whether children invoke absolute and or relative pitch code in processing discrete and continuous musical pitch sequences. Several factors will be examined including the direction, rate and extent of the frequency change as well as frequency region during processing of melodic pitch information. Differences in performance from children within different age range will provide evidence of the putative existence of shifts in the processing of pitch information from absolute to relative pitch code during a critical developmental period.
