Pausing for thought: engagement of left temporal cortex during pauses in speech

Abstract

Pauses during continuous speech, particularly those that occur within clauses, are thought to reflect the planning of forthcoming verbal output. We used functional Magnetic Resonance Imaging (fMRI) to examine their neural correlates. Six volunteers were scanned while describing seven Rorschach inkblots, producing 3 min of speech per inkblot. In an event-related design, the level of blood oxygenation level dependent (BOLD) contrast during brief speech pauses (mean duration 1.3 s, SD 0.3 s) during overt speech was contrasted with that during intervening periods of articulation. We then examined activity associated with pauses that occurred within clauses and pauses that occurred between grammatical junctions. Relative to articulation during speech, pauses were associated with activation in the banks of the left superior temporal sulcus (BA 39/22), at the temporoparietal junction. Continuous speech was associated with greater activation bilaterally in the inferior frontal (BA 44/45), middle frontal (BA 8) and anterior cingulate (BA 24) gyri, the middle temporal sulcus (BA 21/22), the occipital cortex and the cerebellum. Left temporal activation was evident during pauses that occurred within clauses but not during pauses at grammatical junctions. In summary, articulation during continuous speech involved frontal, temporal and cerebellar areas, while pausing was associated with activity in the left temporal cortex, especially when this occurred within a clause. The latter finding is consistent with evidence that within-clause pauses are a correlate of speech planning and in particular lexical retrieval. D

The spatial and temporal dynamics of anticipatory preparation and response inhibition in task-switching

“…The timing of the early differential positivity is consistent with the contention that goal activation occurs in anticipation of the stimulus on informatively cued trials. This fits nicely with the associated superior temporal gyrus activation, as this area is important for temporal action planning (Kirscher et al, 2004;Paulus et al, 2005), as well as for the generation of verbal task labels (Price, 2000) a process shown to be critical in task-switching literature (Goschke, 2000). The size of the RT benefit for informative relative to noninformatively cued trials was correlated with activity in the left superior PPC (Fig.…”

Predicting pauses in L1 and L2 speech: the effects of utterance boundaries and word frequency

“…Previous research has shown that at least in constrained description tasks (in which participants had to describe a path from picture to picture on a computer screen), L1 speakers are more likely to pause before lower frequency nouns in comparison to higher frequency nouns (Hartsuiker and Notebaert 2010;Kircher et al 2004). The current study showed that, in more spontaneous speech, both L1 and L2 speakers are more likely to pause before lower frequency nouns than before higher frequency nouns and that L2 proficiency did not modulate this effect.…”

Native ‘um’s elicit prediction of low-frequency referents, but non-native ‘um’s do not

“…Taken together, our results suggest that listeners are sensitive to the increased likelihood of speakers to be disfluent when formulating low-frequency referents (Hartsuiker & Notebaert, 2010;Kircher et al, 2004;Levelt, 1983;Schnadt & Corley, 2006). Moreover, this sensitivity guides them to use disfluency as a cue to predict reference to a low-frequency object.…”

“…Instead of counterbalancing the two fluency conditions across the LF and HF filler targets, each LF filler target was recorded in the disfluent condition and each HF filler target was recorded in the fluent condition. The reason for this design was that we aimed at a fluent:disfluent ratio across the two frequency conditions which resembled the ratio in spontaneous speech (with disfluencies occurring more often before low-frequency words; Hartsuiker & Notebaert, 2010;Kircher et al, 2004;Levelt, 1983;Schnadt & Corley, 2006). Using our design, the fluent:disfluent ratio was 1:3 for low-frequency targets and 3:1 for high-frequency targets.…”

“…Frequency of occurrence is known to affect lexical retrieval (Almeida, Knobel, Finkbeiner, & Caramazza, 2007;Caramazza, 1997;Jescheniak & Levelt, 1994;Levelt, Roelofs, & Meyer, 1999), and it has been identified as a factor affecting the distribution of disfluencies (Hartsuiker & Notebaert, 2010;Kircher, Brammer, Levelt, Bartels, & McGuire, 2004;Levelt, 1983;Schnadt & Corley, 2006). For Experiment 1, using native speech materials, we hypothesize that if we present listeners with two known objects-one having a high-frequency and the other having a low-frequency name-we may find a disfluency bias towards low-frequency objects.…”