Dynamical constraints on neural population activity The manner in which neural activity unfolds over time is thought to be central to sensory, motor and cognitive functions in the brain. Network models have long posited that the brain’s computations involve time courses of activity that are shaped by the underlying network. A prediction from this view is that the activity time courses should be difficult to violate. We leveraged a brain–computer interface to challenge monkeys to violate the naturally occurring time courses of neural population activity that we observed in the motor cortex. This included challenging animals to traverse the natural time course of neural activity in a time-reversed manner. Animals were unable to violate the natural time courses of neural activity when directly challenged to do so. These results provide empirical support for the view that activity time courses observed in the brain indeed reflect the underlying network-level computational mechanisms that they are believed to implement.
Bayesian surprise intensifies pain in a novel visual-noxious association Pain perception is not solely determined by noxious stimuli, but also varies due to other factors, such as beliefs about pain and its uncertainty. A widely accepted theory posits that the brain integrates prediction of pain with noxious stimuli, to estimate pain intensity. This theory assumes that the estimated pain value is adjusted to minimize surprise, mathematically defined as errors between predictions and outcomes. However, it is still unclear whether the represented surprise directly influences pain perception or merely serves to update this estimate. In this study, we empirically examined this question using virtual reality. In the task, participants reported felt pain via VAS after their arm was stimulated by noxious heat and thrusted into by a virtual knife actively. To manipulate surprise level, the visual threat suddenly disappeared randomly, and noxious heat was presented in the on- or post-action phases. We observed that a transphysical surprising event, created by sudden disappearance of a visual threat cue combined with delayed noxious heat, amplified pain intensity. Subsequent model-based analysis using Bayesian theory revealed significant modulation of pain by the Bayesian surprise value. These results illustrated a real-time computational process for pain perception during a single task trial, suggesting that the brain anticipates pain using an efference copy of actions, integrates it with multimodal stimuli, and perceives it as a surprise.
The simplicity of physical laws Physical laws are strikingly simple, yet there is no a priori reason for them to be so. I propose that nomic realists—Humeans and non-Humeans—should recognize simplicity as a fundamental epistemic guide for discovering and evaluating candidate physical laws. This proposal helps resolve several longstanding problems of nomic realism and simplicity. A key consequence is that the presumed epistemic advantage of Humeanism over non-Humeanism dissolves, undermining a prominent epistemological argument for Humeanism. Moreover, simplicity is shown to be more connected to lawhood than to mere truth.
The hyperintensionality of art Daniel Nolan successfully predicted a hyperintensional revolution in metaphysics in his 2014 paper ‘Hyperintensional Metaphysicsʼ. He argued that hyperintensionality is not restricted to representations. However, it seems that one of the most promising candidates for non-representational hyperintensionality has not yet been considered as such: art. We will argue that art can provide a rather strong case for non-representational hyperintensionality. One reason for this is that the hyperintensionality of art cannot be captured via a representational kind of hyperintensionality.
Intrahemispheric White Matter Asymmetries and Interhemispheric Connections Underlying the Lateralization of Language Production and Spatial Attention in Left-Handers Leftward language production and rightward spatial attention are salient features of functional organization in most humans, but their anatomical basis remains unclear. Interhemispheric connections and intrahemispheric white matter asymmetries have been proposed as important factors underlying functional lateralization. To investigate the role of white matter connectivity in functional lateralization, we first identified 96 left-handers using visual half field naming tasks. They were then divided into atypical and typical functional dominance based on the lateralization of brain activation in a word generation task (for language production) and a landmark task (for spatial attention). Using a novel fixel-based framework, we obtained fiber-specific properties of white matter pathways. Results showed, first, that differences between two language dominance groups occurred in the asymmetry of the superior longitudinal fasciculus-III (SLF-III), whereas differences between two spatial attention dominance groups occurred in the rostrum and rostral body of the corpus callosum. However, the directions of functional lateralization were not associated with the directions of white matter asymmetries. Second, the degree of language lateralization was predicted by SLF-III asymmetry and the rostral body of the corpus callosum, whereas the degree of spatial attention lateralization was predicted by the rostrum of the corpus callosum. Notably, the degree of each functional lateralization was negatively correlated with the anterior and middle callosal connections, supporting the excitatory model of the corpus callosum. The results suggest that language lateralization is shaped by a combined effect of intra- and interhemispheric connections, whereas spatial attention lateralization relies more on interhemispheric connections.
The influence of body orientation on length judgements Perceiving the size of a visual object requires the combination of various sources of visual information. A recent paper by Kim et al. (Body Orientation Affects the Perceived Size of Objects. Perception 2022, 51: 25–36) concluded that body orientation played a substantial role. The present paper aims to answer the question of whether the reported effect of body orientation on visuo-haptic size matching was due to effects on the visual or the haptic judgements of size. To do so, we used a within-participant design combining an experiment using visuo-haptic size matching with two experiments that assessed the visual and haptic size-percept using free magnitude estimation. Our experiments produced a systematic visuo-haptic mismatch, but the sign of the mismatch was opposite to that of the original study. Moreover, our study did not reveal a systematic effect of body orientation on this mismatch. Thirdly, we found that the mismatch we determined from participants matching a visual and haptic percept was considerably smaller than the mismatch we derived from their visual and haptic size estimates. In summary, our results emphasise that conclusions about the perceived size of objects are very sensitive to details of the experimental approach.
Under Your Skin: the Immune Science Behind Tattoos The skin is the first major barrier to injury and harm in everyday life. In areas where clothes or hats fail to protect us, our skin protects us from the sun’s harsh UV rays. If we trip and fall, we might receive mere scrapes to the skin while our muscles and bones will remain unscathed. If one spills, say, hot coffee on themselves when they trip, it is our skin protecting everything underneath from harm. In addition to being our largest organ and protecting us from a myriad of foreign materials, our skin is teeming with helpful immune cells which are always at the ready to eliminate external threats that may enter our system when the outer layer of our skin becomes compromised. Most of the time, our skin heals from a cut or scrape with no sign of prior injury. So, what exactly happens when we decide to adorn our skin with permanent inky pops of personality – tattoos?
Tattoos have been a part of society for thousands of years. They are a traditional practice in many cultures, such as the Māori people [1]. In modern times, they are seen as a form of creativity and self-expression. At many points in history, they have also been associated with negative parts of society. Opinions and experiences with tattoos are as unique as the works themselves. Less numerous, but also in great variety, are the methods for creating tattoos. Whether it be manual or mechanical, every method has the common goal of delivering permanent ink deep into the skin using sharp force.
(Sub)text: Aesthetic Humility in Marianne Moore’s “The Jerboa”Of all the great American Modernists, the poetry of Marianne Moore is perhaps the most idiosyncratic, even the most radical, of them all—no small feat in a group of friends and admirers that included Ezra Pound, T. S. Eliot, Wallace Stevens, William Carlos Williams, e. e. cummings, and HD. Moore’s preferred form was a syllabic stanza bespoke to each poetic occasion, like the unique shell of each individual snail or paper nautilus, and often containing rhyme. In these stanzas, Moore hid behind her virtuosic performance of deflection and difficulty and, of course, revealed herself in it, much as one of her pet-subjects, the exotic animal-portrait, contained a self-portrait at its heart. In her poem on the jerboa, Moore contrasts the desert mouse’s decorousness with the decadence of empire, and in so doing, distinguishes her ideal of true artistry—a vigorous, humble, and ultimately liberated response to one’s natural and formal limitations—with a false art which oppresses the natural in service of the powerful. Wes & Erin discuss Marianne Moore’s poem, “The Jerboa,” first published in 1932, and whether power and wealth might paradoxically prove less abundant than the strictures of form and necessity.