前頭葉と抑制機能：反応抑制研究の現在と未来 The frontal lobe and inhibitory function: Present and future of response inhibition research
S3-3-2-1 fMRIによる反応抑制研究 MRI correlates of response inhibition ○地村弘二1,2 ○Koji Jimura1,2 東京工業大学精密工学研究所1, 東京大学医学部統合生理学教室2 Prec Intell Lab, Tokyo Inst Tech1, Dept Physiol Univ Tokyo Sch Med, Tokyo Japan2 Inhibition of inappropriate responses has been examined by well-established behavioral paradigms, such as the go/nogo, and the stop-signal tasks, that require inhibition of motor responses under situations where response commissions are predominant. As broad fields of studies have demonstrated, use of these simple behavioral tasks has provided robust and consistent evidences, allowing the exploration of distributed neural systems implementing response inhibition. In the current talk, we first outline brain-wide mechanisms of this function that have been identified by prior studies. Posterior part of the inferior frontal gyrus (pIFG) in the right hemisphere has been consistently found to be involved in response inhibition, possibly serving as a core mechanism of this function. Other cortical and subcortical regions, including pre-supplementary motor area and subthalamic nucleus, also contribute to this function, but seem to be dissociated from the right pIFG functionally. Although right hemisphere dominance of response inhibition has long been suggested, recent studies found the involvement of left-lateralized fronto-parietal regions in individuals with more efficient control for response inhibition. These collective evidences suggest multiple neural mechanisms that support response inhibition, and provide potential application to clinical assessments using the simple behavioral paradigms.	S3-3-2-2 体性感覚刺激Go/No-go課題を用いた随意運動抑制過程 Somato-motor inhibitory processing in humans using Go/No-go paradigm ○中田大貴1 ○Hiroki Nakata1 早稲田大学スポーツ科学学術院1 Faculty of Sports Sciences, Waseda University1 Event-related potentials (ERPs) have been used to investigate the neural substrates of response execution and inhibition during Go/No-go paradigms. In No-go trials, two large components, which show a negative deflection at around 140-300 ms (N2) after stimulus onset and a positive deflection at around 300-600 ms (P3), are elicited, compared with ERPs recorded in Go trials. The ERP components in No-go trials have been called 'No-go potentials', and many studies mainly have used visual and auditory stimulation. We previously reported that No-go-related brain potentials were also found in the somatosensory (tactile) modality, and pain (noxious). In this presentation, firstly, we will show the characteristics of No-go related brain potentials using somatosensory Go/No-go paradigm. Then, we will demonstrate the regions responsible for inhibitory processing in somatosensory Go/No-go paradigm using magnetoencephalography (MEG). MEG data revealed that a long-latency response peaking at approximately 160 ms was recorded in only nogo trials, and the equivalent current dipole was estimated to lie around the posterior part of the inferior frontal sulci in the prefrontal cortex. We also clarified the cortical rhythmic activity in No-go processing by using MEG. A rebound in amplitude was recorded in the No-go trials for theta, alpha, and beta activity, peaking at 600-900 ms. A suppression of amplitude was recorded in Go and No-go trials for alpha activity, peaking at 300-600 ms, and in Go and No-go trials for beta activity, peaking at 200-300 ms. Finally, we will show the muscle activation pattern of the lower limbs for the stopping motion of actual baseball batting by recording surface electromyography (EMG) from eight muscles. The muscle activities for 'Swing' and 'Stopping' trials were examined in 10 skilled baseball players and 10 unskilled novices, and the characteristics of EMG activities for 'Stopping' were compared between the two groups.
S3-3-2-3 What has human brain stimulation told us about the neural basis of response inhibition? ○Christopher Chambers1 School of Psychology, Cardi. University1 The ability to inhibit thoughts and actions is a hallmark of effective cognitive control. A convergence of evidence from neurophysiology, neuropsychology and neuroimaging points to a crucial role of the prefrontal cortex, particularly the inferior frontal cortex (IFC), in a range of inhibitory behaviours. Here I will discuss the contribution of human brain stimulation techniques, including transcranial magnetic stimulation (TMS), to understanding the cognitive neuroscience of inhibition. Neurostimulation methods provide a natural complement to neuroimaging techniques because they can reveal which centres and networks and necessary for control in the healthy human brain. I will conclude by considering whether response inhibition is supported by a specialised neurophysiological network or whether inhibitory processes in regions such as IFC reflect more general mechanisms of attention and action planning.	S3-3-2-4 Neurobiological markers and predictors of adolescent impulsivity disorders ○Hugh Garavan1 Department of Psychiatry, The University of Vermont1 The adolescent years constitute a critical period in physical, neurobiological, psychological and social development. Moreover, many psychiatric conditions and risk-related behaviors such as drug use and abuse emerge during this period. Although drug and alcohol use during adolescence is common there is considerable variation across individuals in long-term outcomes. We will present data from a longitudinal neuroimaging-genetic study of 2,400 fourteen-year-old European adolescents. Brain structure and brain function measures were examined for their relationship to adolescent drug use. Activity in regions such as orbitofrontal cortex underlying impulse control and ventral striatum underlying reward anticipation were reduced in those adolescents already using alcohol and, importantly, these effects were present in very light drinkers suggesting pre-existing differences that may have predisposed adolescents to early alcohol use. Models employing machine-learning techniques applied to the data collected at age 14 can successfully predict binge drinking levels at 16. These models show that brain activity on reward and cognitive control tasks, combined with personality, demographics and measures of parental alcohol and nicotine use predict subsequent binge drinking with high accuracy. This research may help address a perennial issue in research with human volunteers insofar as it can separate predisposing differences from the consequences of use.

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