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TMS/EEG studies on the control of visual attention Maurizio Corbetta

TMS/EEG studies on the control of visual attention Maurizio Corbetta. Electrical stimulation in monkeys. Visual enhancement By FEF stimulation. Moore & Armstrong, Nature, 2003. Transcranial magnetic stimulation. EEG potential elicited by TMS (potential maps).

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TMS/EEG studies on the control of visual attention Maurizio Corbetta

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  1. TMS/EEG studies on the control of visual attention Maurizio Corbetta

  2. Electrical stimulation in monkeys Visual enhancement By FEF stimulation Moore & Armstrong, Nature, 2003

  3. Transcranial magnetic stimulation

  4. EEG potential elicited by TMS (potential maps) The potential maps revealed that the P30 component was distributed centrally, the N45 component formed a dipole centered over the stimulation site, and the N100 component had a wide distribution with slight predominance over the left central region. A: scalp distribution of the grand-average potentials recorded during single-pulse TMS. Numbers in the top left corner of each map indicate time after the TMS pulse.B: CURRY-generated probability distribution of a dipole of the N45 negative potential and the best possible fit; note that the dipole is oriented perpendicular to the central sulcus, with the positive pole lying posterior to the negative one. Paus et al., 2001

  5. Visual Cortex Ruff et al. Current Biology, 2006 FEF SC LIP V4v V3v Ekstrom et al. Science, 2008

  6. Taylor et al. Cerebral Cortex, 2007 Fuggetta et al. J.Neurophysiology, 2006

  7. If IPS and FEF are sources of attention then interference with their preparatory activity during a spatial attention task should disrupt target detection and preparatory signals in visual cortex. This interference should not occur after stimulation of nodes in the VAN. Questions

  8. Event-related de-synchronization is a correlate of cortical preparatory processes ERDreflects reduction of alpha or beta EEG rhythms non phase-locked to the event ERD ERPs Hidden into the EEG rhythms, ERPs indicate small neuronal synchronization phase-locked to the event 0 (EMGo) +1 sec -3.5 -3.0 EEG related to a voluntary finger movement 17/45

  9. Occipital alpha power (or de-synchronization) is predictive of the locus of spatial attention Thut et al J.Neurosci 2006

  10. Inter-hemispheric preparatory signals in both DAN and visual cortex predict the locus of spatial attention Locus attention= R-L map activity Sylvester et al., J.Neurosci 2007

  11. Task • Subjects: N=16 right handed • Factors: • Cue direction (L/R) • Target validity (valid/invalid 80/20) • Target type (canonical or rotated) • TMS: • Figure 8 coil • MagStim Rapid 2 (2.2. Tesla) • Individual resting excitability based • on right motor cortex stimulation. • 4. rTMS train at cue onset: • 20 Hz, 150 ms, 100% individual motor threshold

  12. rTMS methods • R FEF; R IPS/PSL; R PrCe; Vertex sham • Talairach coordinates based on meta-analysis fMRI studies (He et al. 2007) • Individual head model to atlas transformation • Neuro-navigation for targeting

  13. EEG methods Brian Amp, 27 EEG electrodes; augmented 10–20 system; 0.05–100 Hz, sampling; rate, 256 Hz. EOG recordings for eye movements. Acquisition: -2 sec to +2 sec post-cue. 120 trials per site. Off line rejection of artifacts at the single trial level (eye movement, blinking, or mouth, head, trunk, or arm movements). Common average. At least 92 trials per condition.

  14. EEG analysis: identification of IAF • Individual Alpha Frequency (IAF) peak is the higher power density in the 6-12 Hz spectrum. With reference to the IAF, the sub-bands of interest are: • Low Alpha -2Hz to IAF to IAF • High Alpha as IAF to IAF +2 Hz • Fixed bands of interest:beta1(13-20 Hz),beta2(21-30 Hz),and gamma(31-44 Hz)

  15. EEG analysis: computation of ERD/ERS Delay=2 sec Target+mask= 70+130 ms Cue=250 ms T T -0.5-1.5 s +0.5-1.5 s ERD%=(E-R)/R*100

  16. IPS- and FEF-TMS duringcueperiod impair target detection Accuracy Reaction Time

  17. Right VF advantageforalpha-numericstimuli

  18. TMS duringcueperiod impairsreorientingtounattendedtargets

  19. R-IPS effect on target detection was independent of cue encoding

  20. EEG waves and spectra post-TMS

  21. TMS over right IPS disrupts anticipatory de-synchronization of occipito-parietal alpha rhythms Low Alpha High Alpha

  22. TMS over right IPS and right FEF disrupts normal contralateral alpha power topography

  23. Across subjects abnormal synchronization after right IPS-TMS correlated with slower RTs Left parietal (P3) Left occipital (O1)

  24. Within subjects abnormal synchronization after right FEF-TMS correlated with slower but not faster trials

  25. TMS effects on behavior were independent of effects on stimulus evoked activity

  26. Discussion: behavior Previous studies reported deficits in stimulus processing and reorienting of attention (Pascual-Leone et al., 1994; Hilgetag et al., 2001; Rushworth et al., 2001; Grosbras and Paus, 2002, 2003; Chambers et al., 2004; Taylor et al., 2005; Thut et al., 2005). Here the deficit is due to interference with preparatory processes in IPS and FEF, not ventral PrCe. 2. Deficit was bilateral: a) spatial vs. non-spatial signals in PPC; b) temporal expectancy; c) feature attention. 3. Deficit extended to the target period, i.e. stimulus-driven reorienting, more than 2 seconds post-TMS. Jack et al. 2007

  27. Discussion: electrophysiology • Control of visual attention by control of oscillatory signals in visual occipital cortex. • IPS/FEF interference disrupts alpha desynchronization • IPS/FEF disrupts alpha topography • Correlation between RT and abnormall synchronization across and within subjects. 2. Consistent with MEG of spatial attention (Siegel et al. 2008). 3. Consistent with BOLD Grangier of spatial attention (Bressler et al. 2008).

  28. Communication through Coherence, Fries (2005)

  29. The role of right and left intraparietal cortices in the control of the visuo-spatial attention. an EEG-rTMS study Paolo Capotosto, Claudio Babiloni, Gian Luca Romani, Maurizio Corbetta Journal of Neuroscience (Under revision)

  30. rTMS recordings • Fifteen healthy young volunteers underwent simultaneous EEG-rTMS recordings • rTMS (20 Hz; 150 ms; motor threshold) was delivered at: • SHAM rTMS • rTMS on Right FEF • rTMS on Right IPS • rTMS on Right PrCe

  31. Behavioral effects of rTMS at different cortical sites (a): Group means (± standard error, SE) of the reaction time (ms). (b): Group means (± standard error, SE) of the accuracy (%). Duncan post-hoc tests: one (p<0.05) asterisk. (c): The accuracy of visual discrimination was significantly more impaired on invalid trials after rTMS in R-IPS(t0) than Sham and L-IPS (t0). Duncan post-hoc tests: one asterisk (p<0.0001).

  32. Topography of alpha power as function of rTMS conditions (a): Topographic maps of anticipatory low and high alpha ERD/ERS during the cue period (+1000-2000 msec after the onset of the cue). (b): Group means (± standard error, SE) of the low alpha ERD/ERS divided by hemisphere (left or right). (c): Group means (± standard error, SE) of the high alpha ERD/ERS divided by hemisphere (left or right). Duncan post-hoc tests: one (p<0.02) or two asterisks (p<0.001).

  33. Contralateral spatial selectivity of alpha power by rTMS condition These means illustrate the results of a main ANOVA effect for Hemisphere (contra or ipsi to cue stimulus) in the Sham (p< 0.05). No main effects were found in Right and Left IPS Group means (± standard error, SE) of the high alpha ERD/ERS for the three Conditions (Sham, R-IPS (t0), L-IPS (t0)) divided by Hemisphere (contra or ipsi to cue stimulus).

  34. Across-subject correlation between alpha ERD/ERS and RTs. (a): Scatter-plot showing the (positive) linear correlation between anticipatory high alpha ERD/ERS at parietal electrode (i.e. P3-P4) and reaction time to valid target presented in the right hemi field, for left “IPS” condition. (b): Scatter-plot showing the (positive) linear correlation between anticipatory high alpha ERD/ERS at parietal electrode (i.e. P3-P4) and reaction time to valid target presented in the right hemi field, for right “IPS” condition.

  35. “Right intraparietal cortex plays a causal role in the modulation of cortical activity related to spatial reorienting and visuomotor transformations during 300-500 ms post-stimulus: an rTMS-EEG study” Paolo Capotosto, Claudio Babiloni, Gian Luca Romani, and Maurizio Corbetta

  36. Experimental Paradigm Twenty-four healthy young volunteers underwent simultaneous EEG-rTMS recordings • rTMS (20 Hz; 150 ms; motor threshold) was delivered at: • SHAM rTMS • rTMS on Right IPS

  37. Behavioral effects of rTMS at different cortical sites. (a): Group means (± standard error, SE) of the accuracy (%). (b): Group means (± standard error, SE) of the reaction time (ms). Duncan post-hoc tests: one (p<0.0005) asterisk. (c): The accuracy of visual discrimination was significantly more impaired on invalid trials after rTMS in rIPS than sham. Duncan post-hoc tests: one asterisk (p<0.02) or two asterisk (0.0002).

  38. Across-subject correlation between the RTs of the two experimental conditions. (a): Scatter-plot showing the (positive) linear correlation between Reaction time in the sham and rIPS condition for the valid trials. (b): Scatter-plot showing the (positive) linear correlation between Reaction time in the sham and rIPS condition for the invalid trials..

  39. Topography of P2 and P3 amplitude as function of rTMS and target validity

  40. ERPs waveforms (a):Grand average (N=24) waveforms of event related potentials (ERPs), obtained averaging data of all subjects. These ERPs refer to the valid and invalid trials at Pz electrode in the sham and rIPS conditions (b): Group means (± standard error, SE) of the P2 peak amplitude. (c): Group means (± standard error, SE) of the P3 peak amplitude. Duncan post-hoc tests: one (p<0.02) or two asterisks (p<0.0001).

  41. Across-subject correlation between the late ERPs component of the two experimental conditions. (a): Scatter-plot showing the (positive) linear correlation between P2 peak amplitude in the sham and rIPS conditions. (b): Scatter-plot showing the (positive) linear correlation between P3 peak amplitude in the sham and rIPS conditions.

  42. Conclusions • Results showed longer reaction time and reduction of correct responses after rTMS over right IPS and FEF and left IPS compared to no effective rTMS or rTMS over right PrCe. Interestingly, the accuracy of visual discrimination was significantly more impaired after rTMS in right IPS on invalid than valid trials. • While disruption of IPS preparatory activity may have a more general effect on alpha desynchronization and target detection, preparatory activity in FEF may play an especially important role when visual selection/discrimination is more demanding. • The rTMS over both right and left IPS and right FEF disrupted the normal contralateral preponderance of the anticipatory alpha rhythms. • P1 and N1 components to the target stimulus in parieto-occipital cortex were not affected by right or left IPS inactivation. • Right IPS-rTMS abolished the P3 difference between invalid and valid targets observed in SHAM

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