[New Paper] Cortico-basal-ganglia network for response inhibition

Watanabe, T., Hanajima, R., Shirota, Y., Tsutsumi, R., Shimizu, T., Hayashi, T., et al. (2015). Effects of rTMS of Pre-Supplementary Motor Area on Fronto Basal Ganglia Network Activity during Stop-Signal Task. The Journal of Neuroscience: 35(12), 4813–4823. 

Response inhibition is one of the key cognitive functions that enable humans to realise their own intentions, and is considered to be supported by fronto-basal-ganglia network. However, causal relationship inside the network has remained unclear.

Here, combining relatively long-lasting types of repetitive transcranial magnetic stimulation (rTMS) with functional magnetic resonance imaging (fMRI), we revealed causal effects of presupplementary motor area (PreSMA) on the network. Using well-established stop-signal task, we found that excitatory and inhibitory rTMS over PreSMA induced significant activity changes in a neural pathway consisting of PreSMA, striatum (STR) and globus pallidus pars interna (GPi). Furthermore, this effect on PreSMA–STR–GPi network activity was highly predictive of behavioral modulations. Interestingly, such causal effects were not seen in right inferior prefrontal cortex or subthalamic nucleus, both of which have been considered to mainly constitute neural mechanisms for response inhibition.

The work will not only demonstrate a causal relationship from PreSMA to basal ganglia during response inhibition, but also add direct evidence for the notion that the fronto-basal-ganglia network for response inhibition comprises multiple top-down regulation pathways in humans. 

[New Paper] Energy landscape during bistable perception

Watanabe, T., Masuda, N., Megumi, F., Kanai, R., & Rees, G. (2014). Energy landscape and dynamics of brain activity during human bistable perception. Nature Communications, 5, 4765. doi:10.1038/ncomms5765

Bistable visual perception is a key paradigm for probing human and animal brainfunctions, and several studies have now shown an intriguing link between the dynamics of bistable perception and the grey matter volume in particular areas of cortex. However, the mechanisms that might link such anatomical features of the brain to subjective experience remained unclear. In this study, we established just such a link by characterising the energy landscapes of brain activity during bistable perception.

During bistable visual perception, we found that human brain activity patterns transited between three spatially distributed energy states. For each participant, this energy landscape predicted both the behavioural dynamics of their perceptual reports and the structural characteristics of focal cortical regions. These findings suggest that the dynamics of brain activity determined by the features of the energy landscape link individual differences in brain anatomy and subjective visual experience.