Conditional associative memory for musical stimuli in nonmusicians: implications for absolute pitch

Abstract

A previous positron emission tomography (PET) study of musicians with and without absolute pitch put forth the hypothesis that the posterior dorsolateral prefrontal cortex is involved in the conditional associative aspect of the identification of a pitch. In the work presented here, we tested this hypothesis by training eight nonmusicians to associate each of four different complex musical sounds (triad chords) with an arbitrary number in a task designed to have limited analogy to absolute-pitch identification. Each subject under-went a functional magnetic resonance imaging scanning procedure both before and after training. Active condition (identification of chords)-control condition (amplitude-matched noise bursts) comparisons for the pretraining scan showed no significant activation maxima. The same comparison for the posttraining scan revealed significant peaks of activation in posterior dorsolateral prefrontal, ventrolateral prefrontal, and parietal areas. A conjunction analysis was performed to show that the posterior dorsolateral prefrontal activity in this study is similar to that observed in the aforementioned PET study. We conclude that the posterior dorsolateral prefrontal cortex is selectively involved in the conditional association aspect of our task, as it is in the attribution of a verbal label to a note by absolute-pitch musicians.

Figure 1.

Average subject performance on the recall task in training sessions 1 and 2. Error bars indicate SE.

Figure 2.

S2_{chords - noise} - S1_{chords - noise} contrast. The sagittal cuts to the left of the figure indicate the location of the coronal cuts to the right. a, Inferior portion of the left middle frontal gyrus, near the rostral border of area 8 and partly in the inferior frontal sulcus. b, c, A band of activity along area 8 of the right middle frontal gyrus. d, The junction of the right posterior middle frontal gyrus and superior precentral sulcus, corresponding to rostral area 6/caudal 8.

Figure 3.

The S2_{chords - noise} - S1_{chords - noise} group contrast and a 40% thresholded probability map of the right precentral gyrus, derived from the MNI International Consortium for Brain Mapping 152 subject normal cohort (Mazziotta et al., 2001), are overlaid onto a three-dimensional rendering of a single subject. This clearly illustrates the position of the peak shown in Figure 2d as lying anterior to the precentral gyrus in rostral area 6/caudal 8.

Figure 4.

a, Spatial conjunction of the tones - noise contrast in AP subjects from the PET results of Zatorre et al. (1998) and the S2_{chords - noise} - S1_{chords - noise} contrast of this study. b, Same as a but with the S2_{chords - noise} - S1_{chords - noise} image flipped at approximately the midsagittal line (see Results, Imaging: conjunction).