Brain activity associated with the rubber foot illusion.
- 作者列表："Matsumoto N","Nakai R","Ino T","Mitani A
:The internal representation of the body is constantly updated by sensory information based on interactions with the environment. The internal representation of the hand can be experimentally manipulated with the rubber hand illusion (RHI) paradigm. Brain activity during the RHI provides insight into the neural mechanisms underpinning the reconstruction of the internal representation of the hand. Recently, the RHI paradigm has been employed for the lower limb, revealing that the illusion is also induced in the lower limb (rubber foot illusion; RFI). However, the neural correlates of the RFI remain unknown. We used functional magnetic resonance imaging (fMRI) to examine brain activity during the RFI. Forty-four healthy volunteers participated in the fMRI experiment. Significant increases in activation were observed in the bilateral medial and middle frontal gyri, left supplemental motor area, bilateral inferior parietal lobuli, precunei, calcarine cortices, and cerebellar hemispheres; and in the vermis and bilateral thalami during the right RFI. During the left RFI, significant increases in activation were observed in the bilateral medial, middle, and superior frontal gyri; left inferior frontal gyrus and supplemental motor area, bilateral inferior parietal lobuli and middle temporal gyri, and in the left cerebellar hemisphere, vermis, and bilateral thalami. Conjunction analysis revealed that the prefrontal cortex including the bilateral medial and middle frontal gyri, parietal cortex including the bilateral inferior parietal lobuli, and cerebellum including the bilateral cerebellar hemispheres and vermis were conjointly activated during the right and left RFIs. The distribution of co-activated brain areas during the RFI was similar to the previously reported distribution of brain areas activated during the RHI. Co-activation of these brain areas may be associated with the reconstruction of the internal representation of the body. The fact that these areas are activated both in the RFI and RHI will have implications for the treatment of patients with disturbed internal bodily representation.
: 身体的内部表征不断被基于与环境相互作用的感觉信息更新。手的内部表示可以用橡胶手错觉 (RHI) 范式进行实验操纵。RHI 期间的大脑活动提供了对支持重建手部内部表征的神经机制的见解。最近，RHI 范式被用于下肢，揭示了下肢也会诱发错觉 (橡胶足错觉; RFI)。然而，RFI 的神经相关性仍然未知。我们使用功能磁共振成像 (fMRI) 检查 RFI 期间的大脑活动。44 名健康志愿者参加了 fMRI 实验。在双侧额叶内侧和中回、左侧补充运动区、双侧顶下叶、前叶、 calcarine 皮质和小脑半球观察到激活显著增加; 在右侧 RFI 期间在蚓部和双侧丘脑。在左侧 RFI 期间，观察到双侧内侧、中部和额上回的激活显著增加; 左侧额下回和补充运动区, 双侧顶下小叶和颞中回，左侧小脑半球、蚓部和双侧丘脑。结合分析发现前额叶皮质包括双侧额叶内侧和中额叶，顶叶皮质包括双侧顶下叶, 右侧和左侧 RFIs 同时激活小脑，包括双侧小脑半球和蚓部。RFI 期间共激活脑区的分布与之前报道的 RHI 期间激活脑区的分布相似。这些脑区的共同激活可能与身体内部表征的重建有关。这些区域在 RFI 和 RHI 中都被激活的事实将对身体内部表征紊乱患者的治疗产生影响。
METHODS::In recent years, transcranial electrical stimulation (tES) has been used to improve cognitive and perceptual abilities and to boost learning. In the visual domain, transcranial random noise stimulation (tRNS), a type of tES in which electric current is randomly alternating in between two electrodes at high frequency, has shown potential in inducing long lasting perceptual improvements when coupled with tasks such as contrast detection. However, its cortical mechanisms and online effects have not been fully understood yet, and it is still unclear whether these long-term improvements are due to early-stage perceptual enhancements of contrast sensitivity or later stage mechanisms such as learning consolidation. Here we tested tRNS effects on multiple spatial frequencies and orientation, showing that tRNS enhances detection of a low contrast Gabor, but only for oblique orientation and high spatial frequency (12 cycles per degree of visual angle). No improvement was observed for low contrast and vertical stimuli. These results indicate that tRNS can enhance contrast sensitivity already after one training session, however this early onset is dependent on characteristics of the stimulus such as spatial frequency and orientation. In particular, the shallow depth of tRNS is likely to affect superficial layers of the visual cortex where neurons have higher preferred spatial frequencies than cells in further layers, while the lack of effect on vertical stimuli might reflect the optimization of the visual system to see cardinally oriented low contrast stimuli, leaving little room for short-term improvement. Taken together, these results suggest that online tRNS effects on visual perception are the result of a complex interaction between stimulus intensity and cortical anatomy, consistent with previous literature on brain stimulation.
METHODS:OBJECTIVE:There is growing interest in treating diseases by electrical stimulation and block of peripheral autonomic nerves, but a paucity of studies on excitation and block of small diameter autonomic axons. We conducted in vivo quantification of the strength-duration properties, activity-dependent slowing (ADS), and responses to kilohertz frequency (KHF) signals for the rat vagus nerve (VN). APPROACH:We conducted acute in vivo experiments in urethane-anesthetised rats. We placed two cuff electrodes on the left cervical VN and one cuff electrode on the anterior subdiaphragmatic VN. The rostral cervical cuff was used to deliver pulses to quantify recruitment and ADS. The caudal cervical cuff was used to deliver KHF signals. The subdiaphragmatic cuff was used to record compound action potentials (CAPs). MAIN RESULTS:We quantified the input-output recruitment and strength-duration curves. Fits to the data using standard strength-duration equations were qualitatively similar, but the resulting chronaxie and rheobase estimates varied substantially. We measured larger thresholds for the slowest fibres (0.5 to 1 m/s), especially at shorter pulse widths. Using a novel cross-correlation CAP-based analysis, we measured ADS of ~2.3% after 3 min of 2 Hz stimulation, which is comparable to ADS reported for sympathetic efferents in somatic nerves, but much smaller than ADS in cutaneous nociceptors. We found greater ADS with higher stimulation frequency and non-monotonic changes in CV in select cases. We found monotonically increasing block thresholds across frequencies from 10 to 80 kHz for both fast and slow fibres. Further, following 25 s of KHF signal, neural conduction could require tens of seconds to recover. SIGNIFICANCE:The quantification of mammalian autonomic nerve responses to conventional and KHF signals provides essential information for development of peripheral nerve stimulation therapies and for understanding their mechanisms of action.
METHODS:BACKGROUND:Early accounts of forced thought were reported at the onset of a focal seizure, and characterized as vague, repetitive, and involuntary intellectual auras distinct from perceptual or psychic hallucinations or illusions. Here, we examine the neural underpinnings involved in conceptual thought by presenting a series of 3 patients with epilepsy reporting intrusive thoughts during electrical stimulation of the left lateral prefrontal cortex (PFC) during invasive surgical evaluation. We illustrate the widespread networks involved through two independent brain imaging modalities: resting state functional magnetic resonance imaging (fMRI) (rs-fMRI) and task-based meta-analytic connectivity modeling (MACM). METHODS:We report the clinical and stimulation characteristics of three patients with left hemispheric language dominance who demonstrate forced thought with functional mapping. To examine the brain networks underlying this phenomenon, we used the regions of interest (ROI) centered at the active electrode pairs. We modeled functional networks using two approaches: (1) rs-fMRI functional connectivity analysis, representing 81 healthy controls and (2) meta-analytic connectivity modeling (MACM), representing 8260 healthy subjects. We also determined the overlapping regions between these three subjects' rs-fMRI and MACM networks through a conjunction analysis. RESULTS:We identified that left PFC was associated with a large-scale functional network including frontal, temporal, and parietal regions, a network that has been associated with multiple cognitive functions including semantics, speech, attention, working memory, and explicit memory. CONCLUSIONS:We illustrate the neural networks involved in conceptual thought through a unique patient population and argue that PFC supports this function through activation of a widespread network.