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Neuro-cognitive effects of Hf-rTMS over the right versus left dorsolateral prefrontal cortex on the attentional modulation of emotional information in healthy subjects: an event-related fMRI-study
Abstracts Results: Fig. 1a shows the group rCBF activation map for volitional movement and for 2Hz stimulation. Fig. 1b shows the relative rCBF change in M1 and CMA/SMA. For volitional movement, the analysis revealed stronger rCBF and BOLD effects (data not shown) in the stimulated M1 compared to SMA/CMA. The opposite effect was observed for 2Hz rTMS. Although the activation maps overlap more in the stimulated M1 than in CMA/SMA, rCBF signal change shows robust modulation in both areas and for both conditions. Significant rCBF activation can also be observed in contralateral M1 due to 2Hz stimulation. Conclusion: We report rCBF changes due to TMS stimulation measured by simultaneous ASL imaging, thereby demonstrating the feasibility of this new technique. The observed spatial activation patterns are in concordance with previous TMS motor cortex studies (e.g. Bestmann et al., E J Neurosc, 2004). In order to increase the statistical robustness of the results, more subjects will be added and the coregistration of the functional data slices to the structural images will be improved.
291 Method: In this sham-controlled cross over study, temporary changes in mood and attentional processing of emotional information were evaluated in samples of healthy female subjects who received Hf- rTMS applied to the right or left DLPFC. Attentional processing of negative versus neutral information was measured using an emotional modification of the exogenous cueing task, which was administered during event-related fMRI. Results: Behavioural results indicated that healthy subjects showed significantly more difficulties in disengaging attention away from negative information after Hf-rTMS over the right DLPFC, but not after left rTMS, nor after placebo stimulation. These difficulties to disengage were related to specific altered brain activation patterns within the abovementioned cortical-limbic circuitry. Results could not be attributed to changes in mood. Conclusions: This study suggests that Hf- rTMS over the right DLPFC may cause a disruption in the activity of brain areas that functionally interact during attentional processing, causing difficulties in disengaging away from negative information. Based on these results, it can be suggested that dysfunctional top-down cognitive processes, such as biases in the modulation of attention, can disrupt the ability to regulate emotional responses and, as such, function as a vulnerability factor for mood disorders.
rTMS Poster Only 165
Selective modulation of intracortical inhibition by low intensity Theta Burst Stimulation
McAllister SM1, Rothwell JC2, Ridding MC1, 1The University of Adelaide (Adelaide, AU); 2University College London (London, UK)
rTMS Poster Only 164
Neuro-cognitive effects of Hf-rTMS over the right versus left dorsolateral prefrontal cortex on the attentional modulation of emotional information in healthy subjects: an event-related fMRI-study
De Raedt R1, Leyman L1, Dannlowski U2, Vanderhasselt M1, Luypaert R3, Baeken C3, 1Ghent University (Ghent, BE); 2University of Mu¨nster (Mu¨nster, DE); 3Free University of Brussels (Brussels, BE) Objective: Recent neuroimaging studies have provided support for a specific network related to the interplay between attention and emotion. They show a widely distributed and functionally interactive network of cortical-limbic pathways that play a central role in the cognitive regulation of mood. More specifically, it is suggested that connectivity between the dorsal anterior cingulate cortex (dACC) and the dorsolateral prefrontal cortex (DLPFC) initiates top-down monitoring of attentional resources causing inhibition of emotional responses through efferent connections with ventral emotional arousal systems such as the orbitofrontal cortex (OFC) and the amygdala. Experimentally induced causal manipulations of ongoing cortical processing of emotional stimuli in healthy subjects, using rTMS, may be used to investigate these interconnected brain systems important in attention/emotion interactions. This can provide more insight into potential dysregulations in patients with mood disorders.
Objective: Continuous Theta Burst Stimulation (cTBS) reduces motor cortical excitability, evidenced by a reduction in the amplitude of motor evoked potentials (MEPs). This effect is thought to be due to a decrease in the efficacy of excitatory synapses which contribute to the generation of the MEP. cTBS may have a similar effects on inhibitory synapses as, in parallel with the MEP amplitude decrease, there is a reduction in short interval intracortical inhibition (SICI) (Huang et al., 2006). Given that cortical inhibitory circuitry has a low threshold for activation, the present study sought to investigate, by using low intensity cTBS, if it was possible to preferentially alter the efficacy of inhibitory pathways. Methods: Eleven healthy subjects were studied. cTBS was applied over the hot spot of the first dorsal interosseous muscle at 70% of active motor threshold (10% below standard TBS intensity). cTBS consisted of 3 stimuli applied at 50 Hz repeated every 200 ms for 40 s. Resting and active motor thresholds and MEPs were assessed at baseline and 5 minutes post-cTBS. SICI and ICF were investigated using paired pulse TMS with interstimulus intervals of 3 ms and 10 ms respectively. The test intensity evoked MEPs of approximately 1 mV and the conditioning intensity was 5% below active motor threshold. SICI/ICF was assessed prior to, and in the period 7-20 minutes following, cTBS. Results: There was no significant change in motor thresholds post-cTBS (p. 5 0.05). There was also no significant change in MEP amplitude folˆ 6 0.1 mV; post :1.2 A ˆ 6 0.2 mV; p. 5 0.05). lowing post-cTBS (pre:1.1 A ˆ 6 8.4 % at baseline However SICI was significantly reduced from 44.3 A ˆ 6 13.2 % following stimulation (p 5 0.03). There was a signifto 67.3 A ˆ 6 22.9 % to 183.4 % A ˆ 6 24.9 % icant increase in ICF from 142.4 A post-cTBS (p 5 0.04). Conclusion: These novel findings demonstrate that cTBS can reduce SICI when applied at an intensity which is sub-threshold for inducing a change in MEPs. It is thought that the after effects of cTBS are due to long term depression (LTD) (Huang et al., 2007). We suggest these results indicate that low intensity cTBS may selectively induce LTD-like effects in inhibitory synapses. The increase in ICF may be a reflection of the reduced excitability of inhibitory circuits (Ziemann, 2004). References: Huang et al. 2006 Neuron, 45, 201-6
291 Method: In this sham-controlled cross over study, temporary changes in mood and attentional processing of emotional information were evaluated in samples of healthy female subjects who received Hf- rTMS applied to the right or left DLPFC. Attentional processing of negative versus neutral information was measured using an emotional modification of the exogenous cueing task, which was administered during event-related fMRI. Results: Behavioural results indicated that healthy subjects showed significantly more difficulties in disengaging attention away from negative information after Hf-rTMS over the right DLPFC, but not after left rTMS, nor after placebo stimulation. These difficulties to disengage were related to specific altered brain activation patterns within the abovementioned cortical-limbic circuitry. Results could not be attributed to changes in mood. Conclusions: This study suggests that Hf- rTMS over the right DLPFC may cause a disruption in the activity of brain areas that functionally interact during attentional processing, causing difficulties in disengaging away from negative information. Based on these results, it can be suggested that dysfunctional top-down cognitive processes, such as biases in the modulation of attention, can disrupt the ability to regulate emotional responses and, as such, function as a vulnerability factor for mood disorders.
rTMS Poster Only 165
Selective modulation of intracortical inhibition by low intensity Theta Burst Stimulation
McAllister SM1, Rothwell JC2, Ridding MC1, 1The University of Adelaide (Adelaide, AU); 2University College London (London, UK)
rTMS Poster Only 164
Neuro-cognitive effects of Hf-rTMS over the right versus left dorsolateral prefrontal cortex on the attentional modulation of emotional information in healthy subjects: an event-related fMRI-study
De Raedt R1, Leyman L1, Dannlowski U2, Vanderhasselt M1, Luypaert R3, Baeken C3, 1Ghent University (Ghent, BE); 2University of Mu¨nster (Mu¨nster, DE); 3Free University of Brussels (Brussels, BE) Objective: Recent neuroimaging studies have provided support for a specific network related to the interplay between attention and emotion. They show a widely distributed and functionally interactive network of cortical-limbic pathways that play a central role in the cognitive regulation of mood. More specifically, it is suggested that connectivity between the dorsal anterior cingulate cortex (dACC) and the dorsolateral prefrontal cortex (DLPFC) initiates top-down monitoring of attentional resources causing inhibition of emotional responses through efferent connections with ventral emotional arousal systems such as the orbitofrontal cortex (OFC) and the amygdala. Experimentally induced causal manipulations of ongoing cortical processing of emotional stimuli in healthy subjects, using rTMS, may be used to investigate these interconnected brain systems important in attention/emotion interactions. This can provide more insight into potential dysregulations in patients with mood disorders.
Objective: Continuous Theta Burst Stimulation (cTBS) reduces motor cortical excitability, evidenced by a reduction in the amplitude of motor evoked potentials (MEPs). This effect is thought to be due to a decrease in the efficacy of excitatory synapses which contribute to the generation of the MEP. cTBS may have a similar effects on inhibitory synapses as, in parallel with the MEP amplitude decrease, there is a reduction in short interval intracortical inhibition (SICI) (Huang et al., 2006). Given that cortical inhibitory circuitry has a low threshold for activation, the present study sought to investigate, by using low intensity cTBS, if it was possible to preferentially alter the efficacy of inhibitory pathways. Methods: Eleven healthy subjects were studied. cTBS was applied over the hot spot of the first dorsal interosseous muscle at 70% of active motor threshold (10% below standard TBS intensity). cTBS consisted of 3 stimuli applied at 50 Hz repeated every 200 ms for 40 s. Resting and active motor thresholds and MEPs were assessed at baseline and 5 minutes post-cTBS. SICI and ICF were investigated using paired pulse TMS with interstimulus intervals of 3 ms and 10 ms respectively. The test intensity evoked MEPs of approximately 1 mV and the conditioning intensity was 5% below active motor threshold. SICI/ICF was assessed prior to, and in the period 7-20 minutes following, cTBS. Results: There was no significant change in motor thresholds post-cTBS (p. 5 0.05). There was also no significant change in MEP amplitude folˆ 6 0.1 mV; post :1.2 A ˆ 6 0.2 mV; p. 5 0.05). lowing post-cTBS (pre:1.1 A ˆ 6 8.4 % at baseline However SICI was significantly reduced from 44.3 A ˆ 6 13.2 % following stimulation (p 5 0.03). There was a signifto 67.3 A ˆ 6 22.9 % to 183.4 % A ˆ 6 24.9 % icant increase in ICF from 142.4 A post-cTBS (p 5 0.04). Conclusion: These novel findings demonstrate that cTBS can reduce SICI when applied at an intensity which is sub-threshold for inducing a change in MEPs. It is thought that the after effects of cTBS are due to long term depression (LTD) (Huang et al., 2007). We suggest these results indicate that low intensity cTBS may selectively induce LTD-like effects in inhibitory synapses. The increase in ICF may be a reflection of the reduced excitability of inhibitory circuits (Ziemann, 2004). References: Huang et al. 2006 Neuron, 45, 201-6