自发的Necker-cube反转可能不是那么自发
Mareike Wilson1,2,3,4, Lukas Hecker1,2,3,4,5, Ellen Joos6
1Department of Psychiatry and Psychotherapy, Medical Center - University of Freiburg, Freiburg, Germany.
Frontiers in human neuroscience
|June 16, 2023
概括
电脑电图 (EEG) 信号预测Necker立方体的感知逆转在它们发生前高达1秒,这表明这些自发的变化之前有神经不稳定. 这挑战了突然感知变化的概念.
科学领域:
- 神经科学是一个神经科学.
- 认知心理学 认知心理学
- 视觉感知 视觉感知 视觉感知
背景情况:
- 对模两可的图形的感知逆转,如Necker立方体,通常被认为是自发的.
- 理论模型表明神经表征的不稳定性先于这些感知转变.
- 了解感知不稳定的神经相关性是预测逆转的关键.
研究的目的:
- 调查前的感知不稳定性的脑电图 (EEG) 相对应物. 尼克尔立方体反转.
- 为了确定神经活动是否可以预测自发的感知逆转.
- 在内源与外源的感知逆转过程中比较神经模式.
主要方法:
- 呈现了模两可的内克克立方体,并在自发逆转过程中记录了EEG.
- 使用明确立方体来诱导外源逆转进行比较.
- 分析了从感知逆转事件发生前1秒到发生期间的EEG数据.
主要成果:
- 逆转和稳定性试验之间的显著EEG差异出现在自发Necker立方体逆转1秒前.
- 在逆转之前,大约在890毫秒内观察到最大的EEG差异 (p = 7.59 × 10^-6,科恩的d = 1.35).
- 对于外源诱导的逆转,没有发现可比的EEG模式.
结论:
- 脑电图显示神经不稳定会先发生自发的内克立方体反转.
- 感知逆转不是完全自发的,因为不稳定发生在更长的时间范围内.
- 这些发现为模两可的图形感知中的感知转变提供了预测标记.
相关概念视频
02:15SN1 Reaction: Stereochemistry
8.7K
This lesson provides an in-depth discussion of the stereochemical outcomes in an SN1 reaction.
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
In the first step of an SN1 reaction, the bond between the electrophilic carbon and the leaving group ionizes to generate the carbocation intermediate. The second step of the mechanism is the nucleophilic attack.
In the formed carbocation, the positively charged carbon is sp2 hybridized with a trigonal planar geometry. As all the three substituents lie on the same plane, a plane of symmetry for the...
8.7K
02:23SN2 Reaction: Stereochemistry
9.7K
In an SN2 reaction, the nucleophilic attack on the substrate and departure of the leaving group occurs simultaneously through a transition state. As the nucleophile approaches the substrate from the back-side, the configuration of the substrate carbon changes from tetrahedral to trigonal bipyramidal and then back to tetrahedral, leading to an inversion in the configuration of the product.
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
If the substrate is an achiral molecule at the α-carbon, the inversion of configuration is not...
9.7K
01:34Woodward–Hoffmann Selection Rules and Microscopic Reversibility
3.2K
Electrocyclic reactions, cycloadditions, and sigmatropic rearrangements are concerted pericyclic reactions that proceed via a cyclic transition state. These reactions are stereospecific and regioselective. The stereochemistry of the products depends on the symmetry characteristics of the interacting orbitals and the reaction conditions. Accordingly, pericyclic reactions are classified as either symmetry-allowed or symmetry-forbidden. Woodward and Hoffmann presented the selection criteria for...
3.2K
02:27SN2 Reaction: Mechanism
14.5K
The kinetic studies of SN2 reactions suggest an essential feature of its mechanism: it is a single-step process without intermediates. Here, both the nucleophile and the substrate participate in the rate-determining step.
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
The presence of the more electronegative halogen in the substrate creates a polarized carbon-halide bond. The halide pulls the electron cloud generating an electrophilic center at the carbon atom. Thus, the carbon atom carries a partial positive charge while the halide has a...
14.5K
01:23Atomic Nuclei: Nuclear Relaxation Processes
685
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
685
01:28Atomic Nuclei: Types of Nuclear Relaxation
333
Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
333