抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://archive-ouverte.unige.ch/unige:104893/ATTACHMENT01

The dynamic functional connectome: State-of-the-art and perspectives

Mind-wandering is often defined as task-unrelated or stimulus-unrelated thought. In this Review, Christoff and colleagues present a definition for mind-wandering that places more emphasis on the dynamic nature of this process. They also examine the brain networks underlying mind-wandering and its involvement in various brain disorders. Most research on mind-wandering has characterized it as a mental state with contents that are task unrelated or stimulus independent. However, the dynamics of mind-wandering — how mental states change over time — have remained largely neglected. Here, we introduce a dynamic framework for understanding mind-wandering and its relationship to the recruitment of large-scale brain networks. We propose that mind-wandering is best understood as a member of a family of spontaneous-thought phenomena that also includes creative thought and dreaming. This dynamic framework can shed new light on mental disorders that are marked by alterations in spontaneous thought, including depression, anxiety and attention deficit hyperactivity disorder.

Mind-wandering as spontaneous thought: a dynamic framework

Discoveries over the past two decades demonstrate that regions distributed throughout the association cortex, often called the default network, are suppressed during tasks that demand external attention and are active during remembering, envisioning the future and making social inferences. This Review describes progress in understanding the organization and function of networks embedded within these association regions. Detailed high-resolution analyses of single individuals suggest that the default network is not a single network, as historically described, but instead comprises multiple interwoven networks. The multiple networks share a common organizational motif (also evident in marmoset and macaque anatomical circuits) that might support a general class of processing function dependent on internally constructed rather than externally constrained representations, with each separate interwoven network specialized for a distinct processing domain. Direct neuronal recordings in humans and monkeys reveal evidence for competitive relationships between the internally and externally oriented networks. Findings from rodent studies suggest that the thalamus might be essential to controlling which networks are engaged through specialized thalamic reticular neurons, including antagonistic subpopulations. These association networks (and presumably thalamocortical circuits) are expanded in humans and might be particularly vulnerable to dysregulation implicated in mental illness. The brain’s default network is thought to comprise a set of regions in the association cortex. Randy Buckner and Lauren DiNicola review findings from humans, monkeys and rodents indicating that multiple subnetworks make up the default network and explore the implications of these observations.

The brain’s default network: updated anatomy, physiology and evolving insights

The hippocampus as a cognitive map

Interactions between the default network and dorsal attention network vary across default subsystems, time, and cognitive states.

Although mind-wandering occupies up to half of our waking thoughts, it is seldom discussed in philosophy. My paper brings these neglected thoughts into focus. I propose that mind-wandering is unguided attention. Guidance in my sense concerns how attention is monitored and regulated as it unfolds over time. Roughly speaking, someone’s attention is guided if she would feel pulled back, were she distracted from her current focus. Because our wandering thoughts drift unchecked from topic to topic, they are unguided. One motivation for my theory is what I call the “Puzzle of the Purposeful Wanderer”. On the one hand, mind-wandering seems essentially purposeless; almost by definition, it contrasts with goal-directed cognition. On the other hand, empirical evidence suggests that our minds frequently wander to our goals. My solution to the puzzle is this: mind-wandering is purposeless in one way—it is unguided—but purposeful in another—it is frequently caused, and thus motivated, by our goals. Another motivation for my theory is to distinguish mind-wandering from two antithetical forms of cognition: absorption (e.g. engrossment in an intellectual idea) and rumination (e.g. fixation on one’s distress). Surprisingly, previous theories cannot capture these distinctions. I can: on my view, absorption and rumination are guided, whereas mind-wandering is not. My paper has four parts. Section 1 spells out the puzzle. Sections 2 and 3 explicate two extant views of mind-wandering—the first held by most cognitive scientists, the second by Thomas Metzinger. Section 4 uses the limitations of these theories to motivate my own: mind-wandering is unguided attention.

Zachary C. Irving

Papers

Mind-wandering as spontaneous thought: a dynamic framework

Interactions between the default network and dorsal attention network vary across default subsystems, time, and cognitive states.

Mind-wandering is unguided attention: accounting for the “purposeful” wanderer

Mind-Wandering as a Scientific Concept: Cutting through the Definitional Haze.

Is an off-task mind a freely-moving mind? Examining the relationship between different dimensions of thought.