subjects. As opposed to the previous study, the patients were tested post-operatively. The
temporal resection includes the medial temporal lobe structures (hippocampal and sur-
rounding cortex) and in some patients, the excision involves the temporal pole as well.
Considering the predominant contribution of LTL structures in processing rapid sequen-
tial information, we expected a deficit in detecting microtemporal variations in familiar
tunes in patients with LTL lesion. In this study, the task of detection of temporal increments
required no tonal judgment, for which the RTL is usually needed.^47 –^50 We therefore postu-
lated adequate performance for patients with RTL lesion. Moreover, an effect of level of
expectation of inter-onset interval was predicted for normal subjects and for patients with
RTL lesion. If this effect reflects a perceptually driven processing, it should disappear in
patients with LTL lesion, otherwise it might be also present in this patient group.
The results of this study are displayed in Figure 14.3 which represents detection accuracy
of the three groups of subjects for expected and unexpected inter-onset increments. An
area under the receiver operating curve (ROC) derived from the number of hits and false
alarms was computed for each subject. As predicted, a significant deficit in detecting inter-
onset increments was obtained in patients with LTL lesion as compared to subjects with
RTL lesion and normal subjects, these two latter groups being not different. This deficit
characterizing patients with LTL lesion cannot be attributed to difficulty in identifying the
tunes since all the subjects were able to adequately recognize the melodies. The results of
this study suggest that the ability to detect an inter-onset increment introduced in very well
known tunes depends on the integrity of LTL structures, extending to the musical domain
the previously reported role of the LTL in rapid sequential processing.
Moreover, the results showed that it is more difficult to detect expected than unexpected
temporal increments for all the subjects indicating therefore that top-down processing
remains functional for the three groups of subjects. Moreover, it means that expectations
of nonmusician listeners were identical to those of pianists, extending to the simple
monodic familiar tunes findings reported with polyphonic classical stock pieces.^45212 Figure 14.3Detection accuracy derived from the area under the receiver operating curve (ROC) of the three
groups of subjects (LTRleft temporal resection, RTRright temporal resection and NCNormal controls)
for expected and unexpected inter onset increments. The bars represent the standard error of the mean.
Area under ROC curve020406080100RTR LTR NC
Group
Expected Unexpected