2. An fMRI investigation of covertly and overtly produced mono- and multisyllabic words. Shuster LI, Lemieux SK. Brain and Language 93 (2005):20-31.

3. The Insula: what is it? An forgotten island of cortex hiding behind the lateral fissure Ill-defined functions may include Visceral sensory Vestibular Motor Supplementary motor Speech movements

4. Background: Speech and the Insula Left anterior insular damage linked to acquired apraxia of speech (AOS) (Dronkers, 1996) AOS characterized as, "a disorder in the motor planning of articulatory movements” Lesion-overlap method 25 chronic stroke patients with AOS 19 patients non-AOS aphasics Hence, “this area seems to be specialized for the motor planning of speech“ AOS Non-AOS

5. Background: Speech and the Insula Insular damage-AOS correlation does not appear to hold for acute-stage stroke patients (Hillis et al., 2004) Insula currently thought to be involved in motor movements of speech E.g. coordination of muscle movements rather than planning (Ackermann & Riecker, 2004)

6. Overview Goal: Examine the role of the insula in overt and covert speech production Methods: fMRI Blood Oxygenation Level Dependent (BOLD) responses Overtness contrast Syllabic-length contrast Logic: Overtness contrast should identify general overt speech areas Syllable-length contrast should show specific areas with graded activation in motor planning of utterances Shuster and Lemieux (2005)

7. Behavioral task: Participants (n=10) auditorily prompted to overtly or covertly “say” individual words 30 monosyllabic nouns 30 tetrasyllabic nouns Words frequency-matched à la Thorndike and Lorge (1944) (No additional behavioral tasks; no behavioral measures taken) Shuster and Lemieux (2005): Methods

8. Repeat the word to yourself as quickly as you can, without moving any part of your mouth. Just hear yourself saying the word inside your head. Be careful not to move any part of your mouth and try not to swallow during the response time

9. But do either of these criticisms really matter here? -Length effects may be difficult to interpret. Criticisms of Materials Length likely confounded with concreteness Thorndike-Lorge?

10. Criticisms of the tasks Image-naming or stem-completion would have been a better task Phonological vs. articulatory rehearsal Participants may have been ‘sleeping’ in covert trials A behavioral measure was needed Covert-subtraction-based differences difficult to interpret

11. Shuster and Lemieux (2005): Methods Design details: Event-related design Allows isolation of speech/motion artifacts Requires long ISIs (1250 ms!) Overt and covert response blocks of 12.5 minutes each All words presented in each block Randomized word orders Block order counterbalanced between subjects

12. Shuster and Lemieux (2005): Methods Imaging details: 1.5T scanner Anatomical scans.86 x.86 x 1.2mm voxels Functional scans 20 interleaved axial slices acquired 3.43 x 3.43 x 5 mm voxels No baseline BOLD responses analyzed via AFNI Subtraction methods for overtness and length

13. Shuster and Lemieux (2005): Methods An interesting analysis detail… “the stimulus time series was convolved with a gamma variate function” Translation: speech- motion artifacts removed by correlating observed data with an idealized ‘motion artifact’ function

14. Overview of results More overall activity in overt than covert speech Included more activity in general cognitive regions More overall activity in multisyllabic than monosyllabic word production Shuster and Lemieux (2005): Results

15. Overtness effects Covert > Overt Overt > Covert

16. Mono- vs. Multisyllable effects Mono- > Multisyllabic Multi- > Monosyllabic Shuster and Lemieux (2005): Results

17. Left Insula More active in overt speech No more active with longer words Active in speech production but maybe not in sequencing speech movements Shuster and Lemieux (2005): Discussion

18. Left inferior parietal lobule (and the left parietal cortex in general) More active with longer (overt) words Consistent with previous production and apraxia studies Indicates involvement in word-length dependent processes (e.g. articulatory planning, sequencing, monitoring) Shuster and Lemieux (2005): Discussion

19. Left Superior Temporal Sulcus (STS) More active in overt speech No more active with longer words Activity may reflect perception of self- generated speech Confounded by auditory stimulus presentation Shuster and Lemieux (2005): Discussion

20. Conclusions: Covert and overt speech produced qualitatively different response patterns, including more activation of general cognitive regions, suggesting that covert production may not be a good substitute for overt production Shuster and Lemieux (2005)

21. Conclusions: The left insula is active in overt speech production, but shows no utterance- length-dependent effects, suggesting a revised role in overt speech production The left parietal cortex, however, does show more length-related activity Shuster and Lemieux (2005)

22. Questions for discussion Any thoughts on the role of the insula in speech? Monitoring in the left inferior parietal cortex? What might have been happening in the “inner speech condition? How might this change our interpretation of overt vs. covert results? Occipital activation? Shuster and Lemieux (2005)

23. “Clearly, as Bennett and Netsell (1999) noted, further studies are required before the specific role of the left insula in speech production can be established” --Shuster and Lemieux (2005)