It is also possible that the decreased temporal sensitivity for the rapid tempo is related to
a difficulty to determine if the irregular sequence was the first or the second one suggest-
ing deficit in the temporal order processing. Although this judgement was not affected
when slower tempos were presented, it becomes more difficult to make such a judgement
in rapid sequences (subjects sometimes having trouble to separate the sequences per se).
This additional constraint might have penalized more strongly patients with LTL
dysfunction than the other subjects.
In previous studies, rapid temporal processing deficits were usually reported in
language-impaired subjects (Ref. 43 for review). Results of the present investigation extend
this finding to patients presenting a limited LTL lesion without associated massive language
disorders, indicating that time-related disturbances are not necessarily associated with lan-
guage disturbances. However, the present results differ from the data obtained in language-
impaired subjects since in this latter case, subjects presented a deficit with a slower tempo
(300 ms IOI) while the subjects with LTL dysfunction did not present any difficulties in this
condition. It seems that the severity of the sequential auditory deficit observed in patients
with or without verbal deficit varies. Although these divergent results could be explained
by methodological differences between the studies, it is also possible that the severity of the
temporal deficits could be correlated to the severity of verbal deficits. The patients tested in
the present study might be situated at one end of the continuum, showing limited tempo-
ral processing deficits and relatively preserved verbal abilities, while dysphasic or dyslexic
subjects could be located at the other end, with more severe temporal deficits and more
severe language deficits. Conversely, it is also possible that rapid sequential temporal pro-
cessing can be disturbed without affecting language functions, which would suggest that
they depend on distinct neural substrates. Future research will be necessary to determine
whether the same underlying mechanism is responsible for the deficit observed in
epileptic and dysphasic patients.
Perception of inter-onset increment in musical sequences:
temporal microstructure of familiar tunes
The goal of this study was to extend to the musical domain the role of the LTL in process-
ing small timing variations. As emphasized in the introduction, it seems that the percep-
tion of small timing differences within a musical sequence has not been investigated in
neuropsychology. To explore this issue, we designed a task involving the detection of inter-
onset interval increments in familiar monodic tunes improving therefore the ecological
validity of the task.
Several descriptive studies showed that performers considerably modify the temporal
structure as noted in the score when interpreting a piece of music (for review, see Ref. 44),
a piece being never played exactly as it is written in the score. However, music played in this
way seems perfect to the listeners, suggesting that we are expecting these temporal changes.
Such temporal microvariations occur at specific locations and are supposed to reflect the
subjective temporal structure of music. It has been demonstrated that consequently, a lis-
tener is expecting these musical microvariations in perceiving musical excerpts.^45 In an
experimental study using classical pieces of music (microstructural expectations), Repp
210