Poor human olfaction is a 19th-century myth

A review from McGann noting work that shows no anatomical basis for supposing human olfaction to be inferior to animals, although variation in the olfactory receptor molecules in different species does cause differences in which odors are best detected:

Structured Abstract

BACKGROUND

It is widely believed that the human sense of smell is inferior to that of other mammals, especially rodents and dogs. This Review traces the scientific history of this idea to 19th-century neuroanatomist Paul Broca. He classified humans as “nonsmellers” not owing to any sensory testing but because he believed that the evolutionary enlargement of the human frontal lobe gave human beings free will at the expense of the olfactory system. He especially emphasized the small size of the human brain’s olfactory bulb relative to the size of the brain overall, and noted that other mammals have olfactory bulbs that are proportionately much larger. Broca’s claim that humans have an impoverished olfactory system (later labeled “microsmaty,” or tiny smell) influenced Sigmund Freud, who argued that olfactory atrophy rendered humans susceptible to mental illness. Humans’ supposed microsmaty led to the scientific neglect of the human olfactory system for much of the 20th century, and even today many biologists, anthropologists, and psychologists persist in the erroneous belief that humans have a poor sense of smell. Genetic and neurobiological data that reveal features unique to the human olfactory system are regularly misinterpreted to underlie the putative microsmaty, and the impact of human olfactory dysfunction is underappreciated in medical practice.

ADVANCES

Although the human olfactory system has turned out to have some biological differences from that of other mammalian species, it is generally similar in its neurobiology and sensory capabilities. The human olfactory system has fewer functional olfactory receptor genes than rodents, for instance, but the human brain has more complex olfactory bulbs and orbitofrontal cortices with which to interpret information from the roughly 400 receptor types that are expressed. The olfactory bulb is proportionately smaller in humans than in rodents, but is comparable in the number of neurons it contains and is actually much larger in absolute terms. Thus, although the rest of the brain became larger as humans evolved, the olfactory bulb did not become smaller. When olfactory performance is compared experimentally between humans and other animals, a key insight has been that the results are strongly influenced by the selection of odors tested, presumably because different odor receptors are expressed in each species. When an appropriate range of odors is tested, humans outperform laboratory rodents and dogs in detecting some odors while being less sensitive to other odors. Like other mammals, humans can distinguish among an incredible number of odors and can even follow outdoor scent trails. Human behaviors and affective states are also strongly influenced by the olfactory environment, which can evoke strong emotional and behavioral reactions as well as prompting distinct memories. Odor-mediated communication between individuals, once thought to be limited to “lower animals,” is now understood to carry information about familial relationships, stress and anxiety levels, and reproductive status in humans as well, although this information is not always consciously accessible.

OUTLOOK

The human olfactory system is increasingly understood to be highly dynamic. Olfactory sensitivity and discrimination abilities can be changed by experiences like environmental odor exposure or even just learning to associate odors with other stimuli in the laboratory. The neurobiological underpinnings of this plasticity, including “bottom-up” factors like regulation of peripheral odor receptors and “top-down” factors like the sensory consequences of emotional and cognitive states, are just beginning to be understood. The role of olfactory communication in shaping social interactions is also actively being explored, including the social spread of emotion through olfactory cues. Finally, impaired olfaction can be a leading indicator of certain neurodegenerative diseases, notably Parkinson’s disease and Alzheimer’s disease. New experimentation will be required to understand how olfactory sequelae might also reflect problems elsewhere in the nervous system, including mental disorders with sensory symptomatology. The idea that human smell is impoverished compared to other mammals is a 19th-century myth.

A moralistic bias in our default representation of what is possible.

From Phillips and Cushman:

Significance

As humans, we think not only about what is, but also what could be. These representations of alternative possibilities support many important cognitive functions, such as predicting others’ future actions, assigning responsibility for past events, and making moral judgments. We perform many of these tasks quickly and effortlessly, which suggests access to an implicit, default assumption about what is possible. What are the default features of the possibilities that we consider? Remarkably, we find a default bias toward representing immoral or irrational actions as being impossible. Although this bias is diminished upon deliberative reflection, it is the default judgments that appear to support higher-level cognition.

Abstract

The capacity for representing and reasoning over sets of possibilities, or modal cognition, supports diverse kinds of high-level judgments: causal reasoning, moral judgment, language comprehension, and more. Prior research on modal cognition asks how humans explicitly and deliberatively reason about what is possible but has not investigated whether or how people have a default, implicit representation of which events are possible. We present three studies that characterize the role of implicit representations of possibility in cognition. Collectively, these studies differentiate explicit reasoning about possibilities from default implicit representations, demonstrate that human adults often default to treating immoral and irrational events as impossible, and provide a case study of high-level cognitive judgments relying on default implicit representations of possibility rather than explicit deliberation.

Osteoarthritis attenuated by removing senescent cells.

Jeon et al. use a model of anterior cruciate ligament surgery to show that senescent cells assemble in the traumatized knee joint and trigger development of osteoarthritis and cartilage erosion in mice. By injecting a drug that causes the specific removal of these cells, the arthritis symptoms are alleviated, and cartilage regeneration and recovery are improved. Here is their technical abstract:

Senescent cells (SnCs) accumulate in many vertebrate tissues with age and contribute to age-related pathologies, presumably through their secretion of factors contributing to the senescence-associated secretory phenotype (SASP). Removal of SnCs delays several pathologies and increases healthy lifespan8. Aging and trauma are risk factors for the development of osteoarthritis (OA), a chronic disease characterized by degeneration of articular cartilage leading to pain and physical disability. Senescent chondrocytes are found in cartilage tissue isolated from patients undergoing joint replacement surgery, yet their role in disease pathogenesis is unknown. To test the idea that SnCs might play a causative role in OA, we used the p16-3MR transgenic mouse, which harbors a p16INK4a (Cdkn2a) promoter driving the expression of a fusion protein containing synthetic Renilla luciferase and monomeric red fluorescent protein domains, as well as a truncated form of herpes simplex virus 1 thymidine kinase (HSV-TK). This mouse strain allowed us to selectively follow and remove SnCs after anterior cruciate ligament transection (ACLT). We found that SnCs accumulated in the articular cartilage and synovium after ACLT, and selective elimination of these cells attenuated the development of post-traumatic OA, reduced pain and increased cartilage development. Intra-articular injection of a senolytic molecule that selectively killed SnCs validated these results in transgenic, non-transgenic and aged mice. Selective removal of the SnCs from in vitro cultures of chondrocytes isolated from patients with OA undergoing total knee replacement decreased expression of senescent and inflammatory markers while also increasing expression of cartilage tissue extracellular matrix proteins. Collectively, these findings support the use of SnCs as a therapeutic target for treating degenerative joint disease.

The Science of Consciousness

In 1994 I went to the first of what has become an annual gathering, sponsored by the Center for Consciousness Studies of the University of Arizona, of researchers, mystics, and random wackos, all interested in understanding the scientific basis of consciousness. In attending the first few of these conferences I made connections with others in the field, like Daniel Dennett, that motivated me to develop the course notes from a new offering I put together the University of Wisconsin "The Biology of Mind" into a book with the same title. This year's meeting in La Jolla, CA., has the usual mixture of hard science and far-out speculation. Just looking at the titles of the main talks is an interesting read, and I paste in those here:

Plenary Program 

Can Machines Be Conscious?

Sir Roger Penrose, Oxford, 'How can Consciousness Arise within the Laws of Physics?'

Joscha Bach, Harvard, 'Consciousness as a Memory of Coordinating Attention: The Conductor Model of Consciousness'

Hartmut Neven, Google , Quantum AI, 'Possible Roles of Quantum Effects and Subjective Experience in Artificial Intelligence' 

Language and Consciousness

Noam Chomsky, MIT, 'Language and Unconscious Mental Acts' 

Thomas Bever, U Arizona, 'Three Aspects of (Un)conscious Processing in Language and its Normal Use'

Michael J Spivey, UC Merced, 'Language, Consciousness and Embodied Cognition' 

Biophysics 1 - Memory, Spin and Anesthesia

Matthew Fisher, UC Santa Barbara, 'Are We Quantum Computers, or Merely Clever Robots?' 

Travis Craddock, Nova Southeastern U, 'A Unitary Mechanism of Anesthesia?: Altering Collective Oscillations in Microtubules' 

Non-Invasive Brain Stimulation 

Marom Bikson, CCNY/CUNY, 'Non-Invasive Brain Stimulation Devices to Change Thought and Behavior' 

John Allen, Arizona, 'Transcranial Ultrasound, Mood, and Resting State Network Connectivity' 

Marvin Berman, VieLight, 'Integrating Noninvasive Photobiomodulation and Neuromodulation' 

Michael Rohan, Harvard, 'The Effects of Low Field Magnetic Stimulation on Mood and Brain Function' 

Physics, Cosmology and Consciousness

Ivette Fuentes, U Nottingham, 'Gravity in the Quantum Lab' 

Brian Keating, UCSD, 'Conscious Cosmos' 

​James Tagg, Cengine, Penrose Institute, 'Are Human Beings Computers?' 

Music and the Brain

Elaine Chew, Queen Mary University London, 'Mind over Music Perception'

Scott Makeig, UCSD, 'Mind Over Consciousness?'  

Neuroscience and Consciousness 1

Stephen Grossberg, Boston U, 'The Varieties of Brain Resonances and the Conscious Experiences They Support' 

Georg Northoff, U Ottawa, 'Temporo-Spatial Theory of Consciousness' 

Friday, June 9, 2017

Neuroscience and Consciousness 2 - Anomalies

Daniel P. Sheehan, U San Diego, 'It's About Time: Experiments in Consciousness and Retrocausation' 

Peter Fenwick, UC London, 'A Meditation Teacher Who Can 'Transmit' Subjective Light/Energy'​

Lakhmir S. Chawla, George Washington U, 'End-of-Life Brain Activity' 

Biophysics 2 - Memristors in the Brain?

Leon Chua, UCSF, 'Brains are Made of Memristors' 

Jack A. Tuszynski, U Alberta, 'Microtubules as Subcellular Memristors'   

Neuroscience and Consciousness 3

Gentry Patrick, UCSD, 'Destruction as a Means of Remodeling: The Many Roles of Ubiquitin at the Synapse' 

VS Ramachandran, UCSD, 'Embodied Brains and Disembodied Minds' 

Charles F. Stevens, Salk Institute, UCSD, 'The Evolutionary Brain Mechanisms That Underlie Consciousness' 

Saturday, June 10, 2017

Vibrations, Resonance and Consciousness

Anirban Bandyopadhyay, NIMS, Tsukuba, 'Vibrational Frequencies of Biomaterials are the Key to Integration of Information' 

Jiapei Dai, South Central University, China, 'Biophotonic Activities and Transmission in Relation to Consciousness' 

Erik Viirre, UCSD, 'Auditory Vibrations and Frequencies: Sounds in Your Head'   

Eastern Philosophy

Xu Yingjin, Fudan University, China, 'Contemporary Theories of Consciousness and Nishida's notion of 'Basho'' 

Deepak Chopra, Chopra Foundation, 'Mind, Body, and Universe as Human Constructs'  

Origin and Evolution of Life and Consciousness

Bruce Damer, UC Santa Cruz, 'The Origin of Life and Consciousness' 

Alysson R. Muotri, UCSD, 'Cerebral Organoids for Neurodevelopmental and Evolutionary Studie's 

Stuart Hameroff, U Arizona, 'The 'Quantum Pleasure Principle' - Did Life Evolve to Feel Good?'  

Our brains have an innate knowledge of tools.

From Striem-Amit et al.:

Significance

To what extent is brain organization driven by innate genetic constraints, and how dependent is it on individual experience during early development? We show that an area of the visual system that processes both hands and tools can develop without sensorimotor experience in manipulating tools with one’s hands. People born without hands show typical hand–tool conjoined activity, in a region connected to the action network. Taken with findings from studies with people born blind, who also show intact hand and tool specialization in the visual system, these findings suggest that no specific sensory or motor experience is crucial for domain-specific organization of visual cortex. Instead, the results suggest that functional brain organization is largely innately determined.

Abstract

The visual occipito-temporal cortex is composed of several distinct regions specialized in the identification of different object kinds such as tools and bodies. Its organization appears to reflect not only the visual characteristics of the inputs but also the behavior that can be achieved with them. For example, there are spatially overlapping responses for viewing hands and tools, which is likely due to their common role in object-directed actions. How dependent is occipito-temporal cortex organization on object manipulation and motor experience? To investigate this question, we studied five individuals born without hands (individuals with upper limb dysplasia), who use tools with their feet. Using fMRI, we found the typical selective hand–tool overlap (HTO) not only in typically developed control participants but also in four of the five dysplasics. Functional connectivity of the HTO in the dysplasics also showed a largely similar pattern as in the controls. The preservation of functional organization in the dysplasics suggests that occipito-temporal cortex specialization is driven largely by inherited connectivity constraints that do not require sensorimotor experience. These findings complement discoveries of intact functional organization of the occipito-temporal cortex in people born blind, supporting an organization largely independent of any one specific sensory or motor experience.

The invisibility cloak illusion - You're too focused on what you're focused on.

Boothy does a summary of her work with Clark and Bargh. Some slightly edited clips:

That coffee stain on your shirt, those mismatched earrings you absent-mindedly selected this morning...people do not notice those things as much as you think...In a classic study from the 1990s, for example, participants put on a shirt emblazoned with the face of the singer Barry Manilow and then walked into a room full of people... It turned out that the number of people who actually noticed noticed was half the number they had thought.

...here’s the bad news. Most of the time, when you’re minding your own business and feeling relatively inconspicuous, you’re being watched much more than you realize...In one experiment, we asked two strangers participating in our study to arrive in our lab at the same time. They were seated in a waiting room and told that the experimenter was running a little behind schedule...Unbeknown to the participants, the study had begun the moment they walked into the waiting room. The real reason they were made to wait was to give them an opportunity to watch — and to feel observed or unobserved by — each other.

Once the participants were in their private rooms, one of them was asked to write down anything he or she noticed or thought about the other person, and then to report on a numerical scale how much he or she had observed the other person. The other participant was asked to write down anything he or she believed the other person had noticed or thought about him or her, and then to estimate how much the other person had observed him or her, using the same scale...Although people surreptitiously noticed all kinds of details about each other — clothing, personality, mood — we found that people were convinced that the other person wasn’t watching them much, if at all.

So other people notice our coffee stains less than we think, but they watch us in general more than we think. The problem, in both cases, is that we project the focus of our attention onto others...In short, we pay too much attention to what we’re paying attention to.

Increasing honesty in humans with noninvasive brain stimulation

Maréchal et al. show that a bit of electricity applied to your right prefrontal cortex makes you half as likely to be dishonest.  Hmmm..... I wonder if we could get a battery and a few small wires into the "Make America Great Again" baseball cap that Trump wears?

Significance

Honesty affects almost every aspect of social and economic life. We conducted experiments in which participants could earn considerable amounts of money by cheating on a die-rolling task. Cheating was substantial but decreased by more than one-half during transcranial direct current stimulation over the right dorsolateral prefrontal cortex. This stimulation-induced increase in honesty was functionally specific: It did not affect other types of behavioral control related to self-interest, risk-taking, and impulsivity. Moreover, cheating was only reduced when it benefited the participants themselves rather than another person. Thus, the human brain implements specialized processes that enable us to remain honest when faced with opportunities to cheat for personal material gain. Importantly, these processes can be strengthened by external interventions.

Abstract

Honesty plays a key role in social and economic interactions and is crucial for societal functioning. However, breaches of honesty are pervasive and cause significant societal and economic problems that can affect entire nations. Despite its importance, remarkably little is known about the neurobiological mechanisms supporting honest behavior. We demonstrate that honesty can be increased in humans with transcranial direct current stimulation (tDCS) over the right dorsolateral prefrontal cortex. Participants (n = 145) completed a die-rolling task where they could misreport their outcomes to increase their earnings, thereby pitting honest behavior against personal financial gain. Cheating was substantial in a control condition but decreased dramatically when neural excitability was enhanced with tDCS. This increase in honesty could not be explained by changes in material self-interest or moral beliefs and was dissociated from participants’ impulsivity, willingness to take risks, and mood. A follow-up experiment (n = 156) showed that tDCS only reduced cheating when dishonest behavior benefited the participants themselves rather than another person, suggesting that the stimulated neural process specifically resolves conflicts between honesty and material self-interest. Our results demonstrate that honesty can be strengthened by noninvasive interventions and concur with theories proposing that the human brain has evolved mechanisms dedicated to control complex social behaviors.

The fading American dream in a nutshell...

From Chetty et al.:

We estimated rates of “absolute income mobility”—the fraction of children who earn more than their parents—by combining data from U.S. Census and Current Population Survey cross sections with panel data from de-identified tax records. We found that rates of absolute mobility have fallen from approximately 90% for children born in 1940 to 50% for children born in the 1980s. Increasing Gross Domestic Product (GDP) growth rates alone cannot restore absolute mobility to the rates experienced by children born in the 1940s. However, distributing current GDP growth more equally across income groups as in the 1940 birth cohort would reverse more than 70% of the decline in mobility. These results imply that reviving the “American dream” of high rates of absolute mobility would require economic growth that is shared more broadly across the income distribution.

Our spatial memory is driven by perceived animacy of simple shapes.

Chin points to work of van Buren and Scholl who use “wolfpack” animations of dart shapes whose points track the movement of a disc (the prey) to show that these are more readily remembered than identical animations in which the dart points are oriented away from or perpendicular to the prey. Perceiving such moving shapes as animate reinforces visual memory and has possibly been important in human evolution. The abstract of the article:

Even simple geometric shapes are seen as animate and goal-directed when they move in certain ways. Previous research has revealed a great deal about the cues that elicit such percepts, but much less about the consequences for other aspects of perception and cognition. Here we explored whether simple shapes that are perceived as animate and goal-directed are prioritized in memory. We investigated this by asking whether subjects better remember the locations of displays that are seen as animate vs. inanimate, controlling for lower-level factors. We exploited the ‘Wolfpack effect’: moving darts (or discs with ‘eyes’) that stay oriented toward a particular target are seen to be actively pursuing that target, even when they actually move randomly. (In contrast, shapes that stay oriented perpendicular to a target are correctly perceived to be drifting randomly.) Subjects played a ‘matching game’ – clicking on pairs of panels to reveal animations with moving shapes. Across four experiments, the locations of Wolfpack animations (compared to control animations equated on lower-level visual factors) were better remembered, in terms of more efficient matching. Thus perceiving animacy influences subsequent visual memory, perhaps due to the adaptive significance of such stimuli.

Semantics and the science of fear - the amygdala doesn't 'cause' fear.

Here are some core clips from an article in which Joseph Ledoux updates an idea he proposed several decades ago:

…that objectively measurable behavioral and physiological responses elicited by emotional stimuli were controlled nonconsciously by subcortical circuits, such as those involving the amygdala, while the conscious emotional experience was the result of cortical (mostly prefrontal) circuits that contribute to working memory and related higher cognitive functions. Building on a distinction emerging in the study of memory, I referred to these as implicit (nonconscious) and explicit (conscious) fear circuits

He has come to realize:

...that the implicit–explicit distinction had less traction in the case of emotions than in memory. The vernacular meaning of emotion words is simply too strong. When we hear the word ‘fear’, the default interpretation is the conscious experience of being in danger, and this meaning dominates. For example, although I consistently emphasized that the amygdala circuits operate nonconsciously, I was often described in both lay and scientific contexts as having shown how feelings of fear emerge from the amygdala. Even researchers working in the objective tradition sometimes appear confused about what they mean by fear; papers in the field commonly refer to ‘frightened rats’ that ‘freeze in fear’. A naïve reader naturally thinks of frightened rats as feeling ‘fear’. As noted above, using mental state terms to describe the function of brain circuits infects the circuit with surplus meaning (psychological properties of the mental state) and confusion invariably results.

Recently, I have … abandoned the implicit–explicit fear approach in favor of a conception that restricts the use of mental state terms to conscious mental states. I now only use ‘fear’ to refer to the experience of fear. It is common these days to argue that folk psychological ideas will be replaced with more accurate scientific constructs as the field matures. Indeed, for nonsubjective brain functions, subjective state labels should be eliminated. This is what I had in mind when I proposed calling the amygdala circuit a defensive survival circuit instead of a fear circuit (see Figure). However, the language of folk psychology describes conscious experiences, such as fear, just fine.

Figure - The Two-Circuit View of Threat Processing and the Experience of Fear. (A) In the two-circuit model, threats are processed in parallel by subcortical and cortical circuits. A subcortical defensive survival circuit centered on the amygdala initiates defensive behaviors in response to threats, while a cortical (mostly prefrontal) cognitive circuit underlying working memory gives rise to the conscious experience of fear. In many situations, survival circuit activity also contributes, albeit indirectly, to fearful feelings. (B) Conscious feelings of fear are proposed to emerge in the cortical circuit as a result of information integration in working memory, including information about sensory and various memory representations, as well as information from survival and arousal circuit activity within the brain, and feedback from body responses.

Psychology is different from other sciences, and has hurdles that they lack. Atoms do not study atoms, but minds study mental states and behaviors. When we engage in psychological research, we must take care to account for the prominent role of subjective experiences in our lives, while also being careful not to attribute subjective causes to behaviors controlled nonconsciously. Conflation of behavioral control circuits with subjective states by indiscriminate use of subjective state terms for both behavioral control circuits and conscious experiences is not a problem restricted to fear. It is present in many areas, including motivation, reward, pain, perception, and memory, to name a few obvious ones. Fear researchers, by addressing this issue, might well set an example that also paves the way for crisper conceptions in other areas of research.

What we perceive depends on how much it costs us.

Interesting work from Hagura et al. showing that our perceptual decisions are biased by the action costs that are associated with our subsequent decisions is summarized by de Lange and Fritsche:

Perceptual decision-making is not solely determined by the characteristics of the sensory stimulus, but is influenced by several factors such as expectation, reward, and previous history , which may all facilitate perceptual decision-making under uncertainty. A factor that has been mostly neglected in laboratory settings is that, in everyday life, making perceptual decisions between several options entails actions which can differ dramatically in their associated motor cost. For instance, imagine standing in front of an apple tree and searching for the reddest-looking apple to pick. Naturally, picking apples higher up in the tree requires more physical effort than picking low-hanging apples. Therefore, your decision about whether to pick a high- or low-hanging apple has consequences for the subsequently accruing motor costs. Does this difference in expected motor costs influence your perceptual decision about the color of the apples? That is, do you judge the low-hanging fruit as more red? We know that motor costs can bias the choice behavior in perceptual decision-making tasks to maximize the expected utility of the choice, but it is unclear whether motor costs can affect the perceptual decision itself.

Hagura et al. shed light on this question. They asked participants to indicate the direction of motion (leftward or rightward) of a cloud of moving dots, by moving one of two robotic manipulanda with their left or right hand, respectively. Unknown to the participants, the resistance for moving one of the manipulanda was gradually increased, while the other remained unchanged. In line with a previous study, Hagura et al. found that participants subsequently showed a tendency to avoid decisions for the motion direction that was associated with the energetically more-costly motor response. Crucially, after the induction of asymmetric motor response costs for manual responses, participants showed a similar bias when indicating their decisions vocally. This transfer of the bias onto decisions reported with a different effector – for which motor response costs were not manipulated – suggests that the repeated exposure to motor response costs associated with a particular decision can bias future perceptual decisions themselves. Thus, the manual-to-vocal transfer effect provides first evidence that motor costs are not necessarily integrated with perceptual decisions at the motor output stage, but that recent experience of motor costs can change how sensory input is transformed into a perceptual decision.

The current results suggest that motor costs can bias perceptual decisions before they are transformed into an effector-specific response. However, the exact stage along the visual processing stream at which this bias occurs is unclear. Motor costs could target an early stage of visual processing, biasing the sensory representation of visual input, or occur at a later stage, targeting a general, effector-unspecific decision stage. Using a drift-diffusion model approach, the authors found that their data were best explained by a model in which the motor costs change the decision bound that is used to make the decision, rather than the evidence accumulation process itself. This suggests that motor costs target a later decision layer, rather than the sensory representation, and distinguishes it from other processes such as attentional biases which affect the accumulation rate of sensory evidence. An intriguing outstanding question, related to this issue, is whether motor costs can alter the appearance of visual stimuli

Has Trump stolen philosophy’s critical tools?

Casey Williams does an intriguing piece in the NYTimes “The Stone” section on topics in philosophy. I’m sure he is not crediting Trump with any awareness of Foucault, Derrida, deconstruction, etc., but here are a few chunks, the whole piece is worth reading:

Trump’s playbook should be familiar to any student of critical theory and philosophy. It often feels like Trump has stolen our ideas and weaponized them.

For decades, critical social scientists and humanists have chipped away at the idea of truth. We’ve deconstructed facts, insisted that knowledge is situated and denied the existence of objectivity. The bedrock claim of critical philosophy, going back to Kant, is simple: We can never have certain knowledge about the world in its entirety. Claiming to know the truth is therefore a kind of assertion of power.

These ideas animate the work of influential thinkers like Nietzsche, Foucault and Derrida, and they’ve become axiomatic for many scholars in literary studies, cultural anthropology and sociology. From these premises, philosophers and theorists have derived a number of related insights. One is that facts are socially constructed. People who produce facts — scientists, reporters, witnesses — do so from a particular social position (maybe they’re white, male and live in America) that influences how they perceive, interpret and judge the world. They rely on non-neutral methods (microscopes, cameras, eyeballs) and use non-neutral symbols (words, numbers, images) to communicate facts to people who receive, interpret and deploy them from their own social positions.

Call it what you want: relativism, constructivism, deconstruction, postmodernism, critique. The idea is the same: Truth is not found, but made, and making truth means exercising power.

The reductive version is simpler and easier to abuse: Fact is fiction, and anything goes. It’s this version of critical social theory that the populist right has seized on and that Trump has made into a powerful weapon.

Some liberals have argued that the best way to combat conservative mendacity is to insist on the existence of truth and the reliability of hard facts. But blind faith in objectivity and factual truth alone has not proven to be a promising way forward...Even if we felt comfortable asserting the existence of something like “truth,” there’s no going back to the days when Americans agreed on matters of fact — when debates about policy were guided by a commitment to truth and reason. Indeed, critique shows us that it’s doubtful that those days, like Trump’s “great” America, ever existed.

For this very reason, these strategies remain useful, however much something like them may be misused, and however carelessly some critical theorists and philosophers have deployed them. Even in a “post-truth era,” a critical attitude allows us to question dominant systems of thought, whether they derive authority from an appearance of neutrality, objectivity or inevitability or from a more Trumpian appeal to alternative facts that dispense with empirical evidence. In a world where lawmakers still appeal to common sense to promote regressive policies, critique remains an important tool for anyone seeking to move past the status quo.

This is because critical ways of thinking demand that we approach knowledge with attention and humility and recognize that, while facts might be created, not all facts are created equal.

While Trump appeals more often to emotions than to facts — or even to common sense — critique can help those who oppose him question the Trumpian version of reality. We can ask not whether a statement is true or false, but how and why it was made and what effects it produces when people feel it to be true. Paying attention to how knowledge is created and used can help us hold leaders like Trump accountable for what they say.

And if we question all ideas — not just the ones we dislike — perhaps our critiques can also reveal new ways of thinking and suggest political possibilities undreamed of by either Trump or his centrist opponents.

Details of our brain's upstairs-downstairs emotion regulation.

Morawetz et al. (open source) offer a study probing how our brain's prefrontal upstairs modulates the up-regulation or down-regulation of our emotional reactivity downstairs, in the amygdala:

The ability to voluntarily regulate our emotional response to threatening and highly arousing stimuli by using cognitive reappraisal strategies is essential for our mental and physical well-being. This might be achieved by prefrontal brain regions (e.g. inferior frontal gyrus, IFG) down-regulating activity in the amygdala. It is unknown, to which degree effective connectivity within the emotion-regulation network is linked to individual differences in reappraisal skills. Using psychophysiological interaction analyses of functional magnetic resonance imaging data, we examined changes in inter-regional connectivity between the amygdala and IFG with other brain regions during reappraisal of emotional responses and used emotion regulation success as an explicit regressor. During down-regulation of emotion, reappraisal success correlated with effective connectivity between IFG with dorsolateral, dorsomedial and ventromedial prefrontal cortex (PFC). During up-regulation of emotion, effective coupling between IFG with anterior cingulate cortex, dorsomedial and ventromedial PFC as well as the amygdala correlated with reappraisal success. Activity in the amygdala covaried with activity in lateral and medial prefrontal regions during the up-regulation of emotion and correlated with reappraisal success. These results suggest that successful reappraisal is linked to changes in effective connectivity between two systems, prefrontal cognitive control regions and regions crucially involved in emotional evaluation.

Brain correlates of third person perspective improving interactions with criticism.

Interesting work (open source) from Leitner et al.:

Previous research suggests that people show increased self-referential processing when they provide criticism to others, and that this self-referential processing can have negative effects on interpersonal perceptions and behavior. The current research hypothesized that adopting a self-distanced perspective (i.e. thinking about a situation from a non-first person point of view), as compared with a typical self-immersed perspective (i.e. thinking about a situation from a first-person point of view), would reduce self-referential processing during the provision of criticism, and in turn improve interpersonal perceptions and behavior. We tested this hypothesis in an interracial context since research suggests that self-referential processing plays a role in damaging interracial relations. White participants prepared for mentorship from a self-immersed or self-distanced perspective. They then conveyed negative and positive evaluations to a Black mentee while electroencephalogram (EEG) was recorded. Source analysis revealed that priming a self-distanced (vs self-immersed) perspective predicted decreased activity in regions linked to self-referential processing (medial prefrontal cortex; MPFC) when providing negative evaluations. This decreased MPFC activity during negative evaluations, in turn, predicted verbal feedback that was perceived to be more positive, warm and helpful. Results suggest that self-distancing can improve interpersonal perceptions and behavior by decreasing self-referential processing during the provision of criticism.

Histone variants promote vulnerability to depressive behaviors

Lepack et al. find that a particular histone protein variant in the nucleus accumbens contributes to stress susceptibility in mice (histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes.) The work suggests that compounds that block its action might be sought as potential therapies for human stress and depressive disorders.

Significance

Human major depressive disorder is a chronic remitting syndrome that affects millions of individuals worldwide; however, the molecular mechanisms mediating this syndrome remain elusive. Here, using a unique combination of epigenome-wide and behavioral analyses, we demonstrate a role for histone variant dynamics in the nucleus accumbens (NAc)—a critical brain center of reward and mood—contributing to stress susceptibility in mice. These studies, which also demonstrate that molecular blockade of aberrant dynamics in the NAc promotes resilience to chronic stress, promise to aid in the identification of novel molecular targets (i.e., downstream genes displaying altered expression as the result of stress-induced histone dynamics) that may be exploited in the development of more effective pharmacotherapeutics.

Abstract

Human major depressive disorder (MDD), along with related mood disorders, is among the world’s greatest public health concerns; however, its pathophysiology remains poorly understood. Persistent changes in gene expression are known to promote physiological aberrations implicated in MDD. More recently, histone mechanisms affecting cell type- and regional-specific chromatin structures have also been shown to contribute to transcriptional programs related to depressive behaviors, as well as responses to antidepressants. Although much emphasis has been placed in recent years on roles for histone posttranslational modifications and chromatin-remodeling events in the etiology of MDD, it has become increasingly clear that replication-independent histone variants (e.g., H3.3), which differ in primary amino acid sequence from their canonical counterparts, similarly play critical roles in the regulation of activity-dependent neuronal transcription, synaptic connectivity, and behavioral plasticity. Here, we demonstrate a role for increased H3.3 dynamics in the nucleus accumbens (NAc)—a key limbic brain reward region—in the regulation of aberrant social stress-mediated gene expression and the precipitation of depressive-like behaviors in mice. We find that molecular blockade of these dynamics promotes resilience to chronic social stress and results in a partial renormalization of stress-associated transcriptional patterns in the NAc. In sum, our findings establish H3.3 dynamics as a critical, and previously undocumented, regulator of mood and suggest that future therapies aimed at modulating striatal histone dynamics may potentiate beneficial behavioral adaptations to negative emotional stimuli.

Watching the brain think about friends.

Work from Wlodarski and Dunbar (open source) produces imaging data suggesting that maintaining friendships may be more cognitively exacting than maintaining kin relationships. The graphics of imaging showing differences in kin versus friend processing are very nice. Their introduction offers background on the cognitive underpinnings for managing different types of relationships having varying degrees of closeness. Their abstract:

The aim of this study was to examine differences in the neural processing of social information about kin and friends at different levels of closeness and social network level. Twenty-five female participants engaged in a cognitive social task involving different individuals in their social network while undergoing functional magnetic resonance imaging scanning to detect BOLD (Blood Oxygen Level Dependent) signals changes. Greater levels of activation occurred in several regions of the brain previously associated with social cognition when thinking about friends than when thinking about kin, including the posterior cingulate cortex (PCC) and the ventral medial prefrontal cortex (vMPFC). Linear parametric analyses across network layers further showed that, when it came to thinking about friends, activation increased in the vMPFC, lingual gyrus, and sensorimotor cortex as individuals thought about friends at closer layers of the network. These findings suggest that maintaining friendships may be more cognitively exacting than maintaining kin relationships.

From learning to instinct

I pass on a few chunks from the Science Perspective article by Robinson and Barron:

An animal mind is not born as an empty canvas: Bottlenose dolphins know how to swim and honey bees know how to dance without ever having learned these skills. Little is known about how animals acquire the instincts that enable such innate behavior. Instincts are widely held to be ancestral to learned behavior. Some have been elegantly analyzed at the cellular and molecular levels, but general principles do not exist. Based on recent research, we argue instead that instincts evolve from learning and are therefore served by the same general principles that explain learning.

Tierney first proposed in 1986 that instincts can evolve from behavioral plasticity, but the hypothesis was not widely accepted, perhaps because there was no known mechanism. Now there is a mechanism, namely epigenetics. DNA methylation, histone modifications, and noncoding RNAs all exert profound effects on gene expression without changing DNA sequence. These mechanisms are critical for orchestrating nervous system development and enabling learning-related neural plasticity.

For example, when a mouse has experienced fear of something, changes in DNA methylation and chromatin structure in neurons of the hippocampus help stabilize long-term changes in neural circuits. These changes help the mouse to remember what has been learned and support the establishment of new behavioral responses. Epigenetic mechanisms that support instinct by operating on developmental time scales also support learning by operating on physiological time scales. Evolutionary changes in epigenetic mechanisms may sculpt a learned behavior into an instinct by decreasing its dependence on external stimuli in favor of an internally regulated program of neural development (see the figure).

There is evidence for such epigenetically driven evolutionary changes in behavior. For example, differences in innate aggression levels between races of honey bees can be attributed to evolutionary changes in brain gene expression that also control the onset of aggressive behavior when threatened. These kinds of changes can also explain more contemporary developments, including new innate aspects of mating and foraging behavior in house finches associated with their North American invasion 75 years ago, and new innate changes in the frequency and structure of song communication in populations of several bird species now living in urban environments. We propose that these new instincts have emerged through evolutionary genetic changes that acted on initially plastic behavioral responses.

The Nature Fix

Suttie points to a recent book from Florence Williams, also reviewed by Jason Mark, that I would like to be able to slow down enough to actually read, rather than just doing a slightly amplified tweet. 

From Suttie:

...researchers in Finland found that even short walks in an urban park or wild forest were significantly more beneficial to stress relief than walks in an urban setting. And researchers at Stanford found that walks in a natural setting led to better moods, improved performance on memory tasks, and decreased rumination when compared to urban walks.

Similarly, having nature nearby seems to benefit our health. Researchers in England analyzed data from 40 million people and found that residents who lived in a neighborhood with nearby open, undeveloped land tended to develop fewer diseases and were less likely to die before age 65. Most significantly, this finding was not related to income levels, suggesting that green spaces may buffer against poverty-related stress. And nature experiences have been used to treat mental disorders, like PTSD and drug addiction, with some level of success.

From Mark:

Two centuries ago, the Romantics trumpeted the virtues of nature as the antidote to the viciousness of industrialization. In 1984, the biologist Edward O. Wilson put a scientific spin on the idea with his book “Biophilia,” which posited that humans possess an innate love of nature.

Wilson’s argument was persuasive, yet it was mostly an aspiration dressed up as a hypothesis. In the generation since, scientists have sought to confirm the biophilia hypothesis — and they’re starting to get results. As little as 15 minutes in the woods has been shown to reduce test subjects’ levels of cortisol, the stress hormone. Increase nature exposure to 45 minutes, and most individuals experience improvements in cognitive performance. There are society-scale benefits as well. Researchers in England have shown that access to green spaces reduces income-related mental health disparities.

It’s all very encouraging, but how exactly does nature have such an effect on people? To answer that question, Williams shadows researchers on three continents who are working on the frontiers of nature neuroscience.

Maybe it’s the forest smells that turn us on; aerosols present in evergreen forests act as mild sedatives while also stimulating respiration. Perhaps it’s the soundscape, since water and, especially, birdsong have been proven to improve mood and alertness. Nature’s benefits might be due to something as simple as the fact that natural landscapes are, literally, easy on the eyes. Many of nature’s patterns — raindrops hitting a pool of water or the arrangement of leaves — are organized as fractals, and the human retina moves in a fractal pattern while taking in a view. Such congruence creates alpha waves in the brains — the neural resonance of relaxation.

In this context, I want to mention again Wallace Nicholl's book on our connection to water, "Blue Mind." He recently asked me to attend a conference he organized on this subject, and I was sorry that I was not free to do this.

Brain stimulation enhances memory.

Important work from Ezzyat et al., a potential approach to ameliorating memory loss in dementia:

Highlights

•Intracranial brain stimulation has variable effects on episodic memory performance 

•Stimulation increased memory performance when delivered in poor encoding states 

•Recall-related brain activity increased after stimulation of poor encoding states 

•Neural activity linked to contextual memory predicted encoding state modulation

Summary

People often forget information because they fail to effectively encode it. Here, we test the hypothesis that targeted electrical stimulation can modulate neural encoding states and subsequent memory outcomes. Using recordings from neurosurgical epilepsy patients with intracranially implanted electrodes, we trained multivariate classifiers to discriminate spectral activity during learning that predicted remembering from forgetting, then decoded neural activity in later sessions in which we applied stimulation during learning. Stimulation increased encoding-state estimates and recall if delivered when the classifier indicated low encoding efficiency but had the reverse effect if stimulation was delivered when the classifier indicated high encoding efficiency. Higher encoding-state estimates from stimulation were associated with greater evidence of neural activity linked to contextual memory encoding. In identifying the conditions under which stimulation modulates memory, the data suggest strategies for therapeutically treating memory dysfunction.

Brain-heart dialogue shows how racism hijacks perception

Tsakiris does a nice summary of his work that shows a biological basis for why you’re more than twice as likely as a white person to be unarmed if you’re killed in an encounter with the police. Here is the core text:

At my lab at Royal Holloway, University of London, we decided to test whether the cardiac cycle made a difference to the expression of racial prejudice. The heart is constantly informing the brain about the body’s overall level of ‘arousal’, the extent to which it is attuned to what is happening around it. On a heartbeat, sensors known as ‘arterial baroreceptors’ pick up pressure changes in the heart wall, and fire off a message to the brain; between heartbeats, they are quiescent. Such visceral information is initially encoded in the brainstem, before reaching the parts implicated in emotional and motivational behaviour. The brain, in turn, responds by trying to help the organism stabilise itself. If it receives signals of a raised heart-rate, the brain will generate predictions about the potential causes, and consider what the organism should do to bring itself down from this heightened state. This ongoing heart-brain dialogue, then, forms the basis of how the brain represents the body to itself, and creates awareness of the external environment.

In our experiment, we used what’s known as the ‘first-person shooter’s task’, which simulates the snap judgments police officers make. Participants see a white or black man holding a gun or phone, and have to decide whether to shoot depending on the perceived level of threat. In prior studies, participants were significantly more likely to shoot an unarmed black individual than a white one.

But we timed the stimuli to occur either between or on a heartbeat. Remarkably, the majority of misidentifications occurred when black individuals appeared at the same time as a heartbeat. Here, the number of false positives in which phones were perceived as weapons rose by 10 per cent compared with the average. In a different version of the test, we used what’s known as the ‘weapons identification task’, where participants see a white or black face, followed by an image of a gun or tool, and must classify the object as quickly as possible. When the innocuous items were presented following a black face, and on a heartbeat, errors rose by 20 per cent.

Yet in both instances, when the judgment happened between heartbeats, we observed no differences in people’s accuracy, irrespective of whether they were responding to white or black faces. It seems that the combination of the firing of signals from the heart to the brain, along with the presentation of a stereotypical threat, increased the chances that even something benign will be perceived as dangerous.

It’s surprising to think of racial bias as not just a state or habit of mind, nor even a widespread cultural norm, but as a process that’s also part of the ebbs and flows of the body’s physiology. The heart-brain dialogue plays a crucial role in regulating blood pressure and heart rate, as well as motivating and supporting adaptive behaviour in response to external events. So, in fight-or-flight responses, changes in cardiovascular function prepare the organism for subsequent action. But while the brain might be predictive, those predictions can be inaccurate. What our findings illustrate is the extent to which racial and possibly other stereotypes are hijacking bodily mechanisms that have evolved to deal with actual threats.

The psychologist Lisa Barrett Feldman at Northeastern University in Boston coined the term ‘affective realism’ to describe how the brain perceives the world through the body. On the one hand, this is a reason for optimism: if we can better understand the neurological mechanisms behind racial bias, then perhaps we’ll be in a better position to correct it. But there is a grim side to the analysis, too. The structures of oppression that shape who we are also shape our bodies, and perhaps our most fundamental perceptions. Maybe we do not ‘misread’ the phone as a gun; we might we actually see a gun, rather than a phone. Racism might not be something that societies can simply overcome with fresh narratives and progressive political messages. It might require a more radical form of physiological retraining, to bring our embodied realities into line with our stated beliefs.