Scientific explanation of our subjective experience.....

Being a card carrying materialist, I've always felt that our mental life could be explained in physical terms. Although I consider myself a twinkie when it comes to appreciating deep philosophical debate, I really think Nagel's succinct summary of the main argument in his recent book "Mind and Cosmos" doesn't hold water, because it makes a basic category error that Metzinger has pointed out. More on that below, but first some clips of Nagel's summary, and a subsequent refutation by Kitcher.

The physical sciences can describe organisms like ourselves as parts of the objective spatio-temporal order – our structure and behavior in space and time – but they cannot describe the subjective experiences of such organisms or how the world appears to their different particular points of view. There can be a purely physical description of the neurophysiological processes that give rise to an experience, and also of the physical behavior that is typically associated with it, but such a description, however complete, will leave out the subjective essence of the experience – how it is from the point of view of its subject — without which it would not be a conscious experience at all.

So the physical sciences, in spite of their extraordinary success in their own domain, necessarily leave an important aspect of nature unexplained.  Further, since the mental arises through the development of animal organisms, the nature of those organisms cannot be fully understood through the physical sciences alone.  Finally, since the long process of biological evolution is responsible for the existence of conscious organisms, and since a purely physical process cannot explain their existence, it follows that biological evolution must be more than just a physical process, and the theory of evolution, if it is to explain the existence of conscious life, must become more than just a physical theory.

Kitcher argues:

...Once he has set up the framework within which the possible positions will be placed, his arguments are not easy to resist. In my view, though, the framework itself is faulty.

Contrary to the Newtonian vision in which everything would be explained on the basis of a small number of physical principles:

…since the 19th century — since Darwin, in fact — that has not been a convincing picture of how the sciences make their advances. Darwin did not supply a major set of new principles that could be used to derive general conclusions about life and its history: he crafted a framework within which his successors construct models of quite specific evolutionary phenomena. Model-building lies at the heart of large parts of the sciences, including parts of physics. There are no grand theories, but lots of bits and pieces, generating local insights about phenomena of special interest….The molecular biologist doesn’t account for life, but for a particular function of life (usually in a particular strain of a particular species). Nagel’s 19th-century predecessors wondered how life could be characterized in physico-chemical terms. That particular wonder hasn’t been directly addressed by the extraordinary biological accomplishments of past decades. Rather, it’s been shown that they were posing the wrong question: don’t ask what life is (in your deepest Newtonian voice); consider the various activities in which living organisms engage and try to give a piecemeal understanding of those.

First, philosophy and science don’t always answer the questions they pose — sometimes they get over them. Second, instead of asking what life and mind and value are, think about what living things and minds do, and what is going on in the human practices of valuing. This shift of perspective has already occurred in the case of life. A Nagel analog who worried about the fact that we lack a physico-chemical account of life, would probably be rudely dismissed; a kinder approach would be to talk about the ways in which various aspects of living things have been illuminated.

Nagel is in the grip of a philosophical perspective on science, once very popular, that the work of the last four decades has shown to be inadequate to cope with large parts of the most successful contemporary sciences. Because of that perspective, a crucial option disappears from his menu: the phenomena that concern him, mind and value, are not illusory, but it might nevertheless be an illusion that they constitute single topics for which unified explanations can be given. The probable future of science in these domains is one of decomposition and the provision of an enormous and heterogeneous family of models. Much later in the day, it may fall to some neuroscientist to explain the illusion of unity, a last twist on successful accounts of many subspecies of mental processes and functions. Or, perhaps, it will be clear by then that the supposed unity of mind and of value were outgrowths of a philosophical mistake, understandable in the context of a particular stage of scientific development, but an error nonetheless.

I think the most coherent view of what is going on in our subjective mental experience is given by Thomas Metzinger in his book "The Ego Tunnel"….. I've extracted some points:

- What he calls the Ego Tunnel (or PSM) is a complex property of the global neural correlate of consciousness (NCC which are the subject of many books)  - what make “Mineness” or “I” possible - a vastly reduced model of what is really 'out there.'

 

- It is a transparent mental image that allows the conscious experience of being a self  to emerge. (Transparency is our not seeing the firing of neurons in our brain, only what they represent for us).

 

- The model at a given moment is transparent because the brain has no chance of discovering that is is a model - it is a higher order representation integrating its information in longer time window than the lower order information processing in smaller time windows. 

 

- Our visual perception time window is much larger than the time windows of primary visual processing and so those more rapid underlying processes are completely invisible to it (the same thing as not being able to see the individual frames in a movie reel,  because our visual integration time is much longer).   It is a metabolically efficient, quick and dirty way of knowing only what our evolution has deemed it necessary for us to know. 

   

-In this view, Consciousness is taken to be the space of attentional agency,  that set of information currently active in our brains to which we can deliberately direct our high level attention.  Low level attention is automatic and can be triggered by entirely unconscious events.  

 

- Metzinger makes the further assertion that consciousness is epistemologically irreducible:   one reality, one kind of fact, but two kinds of knowledge: first-person knowledge and third-person knowledge, that never can be conflated.

 

- There is a long list of ideas on why consciousness evolved, what it is good for, doing goal hierarchies and long-terms plans, enhancement of social coordination, etc....Old things in the evolution of consciousness are ultrafast and reliable (like qualities of sensory experience) and transparent. In contrast, abstract conscious thought is not transparent or fast,  it is slow and unreliable, experienced as ‘made.’

I like Metzinger's description of consciousness as a  as a new kind of virtual organ - unlike the permanent hardware of the liver, kidney, or heart it is always present. Virtual organs form for a certain time when needed (like an immune response, or like desire, courage, anger)...they are a new computational strategy, that makes classes of facts globally available and allows attending, flexible reacting, within context. The fast acting hardware of our autonomic and neuroendocrine emotional chemistry evolved to support the new classes of transient virtual organs.

Language can boost unseen objects into visual awareness.

From Lupyan et al:

Linguistic labels (e.g., “chair”) seem to activate visual properties of the objects to which they refer. Here we investigated whether language-based activation of visual representations can affect the ability to simply detect the presence of an object. We used continuous flash suppression to suppress visual awareness of familiar objects while they were continuously presented to one eye. Participants made simple detection decisions, indicating whether they saw any image. Hearing a verbal label before the simple detection task changed performance relative to an uninformative cue baseline. Valid labels improved performance relative to no-label baseline trials. Invalid labels decreased performance. Labels affected both sensitivity (d′) and response times. In addition, we found that the effectiveness of labels varied predictably as a function of the match between the shape of the stimulus and the shape denoted by the label. Together, the findings suggest that facilitated detection of invisible objects due to language occurs at a perceptual rather than semantic locus. We hypothesize that when information associated with verbal labels matches stimulus-driven activity, language can provide a boost to perception, propelling an otherwise invisible image into awareness.

A Methods note:

Continuous flash suppression was implemented using anaglyph images: participants wore red/cyan glasses and viewed stereograms containing a high-contrast red mask (∼9° × 9°) and—on object-present trials—a superimposed lower-contrast cyan object (Fig. 1A). Only the object was visible to the right eye and only the mask to the left. The dynamic mask comprised curved line segments, with frames randomly alternating at 10 Hz. Because similarity in spatial properties between stimuli and masks is important for effective suppression of stimuli (72), line segments were used to better mask the curvilinear character of the objects.

(A) Stimulus creation using continuous flash suppression. (B) Basic procedure of experiments 1 and 2.

A drug that alters dopamine receptors and risk-taking behaviors

Interesting observations from Norbury et al. on a drug that activates or enhances action of some dopamine receptors and also increases the probability of taking risky choices. (Maybe a receptor antagonist should be developed for hedge fund managers and investment bankers who keep crashing our economy!).

Trait sensation-seeking, defined as a need for varied, complex, and intense sensations, represents a relatively underexplored hedonic drive in human behavioral neuroscience research. It is related to increased risk for a range of behaviors including substance use, gambling, and risky sexual practice. Individual differences in self-reported sensation-seeking have been linked to brain dopamine function, particularly at D2-like receptors, but so far no causal evidence exists for a role of dopamine in sensation-seeking behavior in humans. Here, we investigated the effects of the selective D2/D3 agonist cabergoline on performance of a probabilistic risky choice task in healthy humans using a sensitive within-subject, placebo-controlled design. Cabergoline significantly influenced the way participants combined different explicit signals regarding probability and loss when choosing between response options associated with uncertain outcomes. Importantly, these effects were strongly dependent on baseline sensation-seeking score. Overall, cabergoline increased sensitivity of choice to information about probability of winning; while decreasing discrimination according to magnitude of potential losses associated with different options. The largest effects of the drug were observed in participants with lower sensation-seeking scores. These findings provide evidence that risk-taking behavior in humans can be directly manipulated by a dopaminergic drug, but that the effectiveness of such a manipulation depends on baseline differences in sensation-seeking trait. This emphasizes the importance of considering individual differences when investigating manipulation of risky decision-making, and may have relevance for the development of pharmacotherapies for disorders involving excessive risk-taking in humans, such as pathological gambling.

Nighttime light impairs our emotional responses.

I have done a number of posts (enter melanopsin in the search box to find them) on a second visual system, involving the visual pigment melanopsin in our retinal ganglion cells, that has been shown to influence mood,memory, and cognition. Bedrosian et al. now add more detail to this story, showing that noctural light exposure, particularly to blue light, impairs emotional responses:

Life on earth is entrained to a 24 h solar cycle that synchronizes circadian rhythms in physiology and behavior; light is the most potent entraining cue. In mammals, light is detected by (1) rods and cones, which mediate visual function, and (2) intrinsically photosensitive retinal ganglion cells (ipRGCs), which primarily project to the suprachiasmatic nucleus (SCN) in the hypothalamus to regulate circadian rhythms. Recent evidence, however, demonstrates that ipRGCs also project to limbic brain regions, suggesting that, through this pathway, light may have a role in cognition and mood. Therefore, it follows that unnatural exposure to light may have negative consequences for mood or behavior. Modern environmental lighting conditions have led to excessive exposure to light at night (LAN), and particularly to blue wavelength lights. We hypothesized that nocturnal light exposure (i.e., dim LAN) would induce depressive responses and alter neuronal structure in hamsters (Phodopus sungorus). If this effect is mediated by ipRGCs, which have reduced sensitivity to red wavelength light, then we predicted that red LAN would have limited effects on brain and behavior compared with shorter wavelengths. Additionally, red LAN would not induce c-Fos activation in the SCN. Our results demonstrate that exposure to LAN influences behavior and neuronal plasticity and that this effect is likely mediated by ipRGCs. Modern sources of LAN that contain blue wavelengths may be particularly disruptive to the circadian system, potentially contributing to altered mood regulation.

Better safe than sorry?...Anxiety and our body’s safety margin.

Sambo and Iannetti find interesting correlations between our anxiety and our interpersonal space boundaries:

The defensive peripersonal space represents a “safety margin” advantageous for survival. Its spatial extension and the possible relationship with personality traits have never been investigated. Here, in a population of 15 healthy human participants, we show that the defensive peripersonal space has a sharp boundary, located between 20 and 40 cm from the face, and that within such space there is a thin, “highest-risk area” closest to the face (i.e., an “ultra-near” defensive space). Single-subject analysis revealed clear interindividual differences in the extension of such peripersonal space. These differences are positively related to individual variability in trait anxiety. These findings point to the potential for measuring a range of defensive behaviors in relation to individual levels of anxiety. Such measures will allow developing procedures to test risk assessment abilities, particularly in professions that require reacting quickly to aversive stimuli near the body, such as firemen, policemen, and military officers. This may also lead to possible interventions to improve their performance under pressure.

Dopamine, rewards, and the brain

The neurotransmitter dopamine is one we all seem to have heard about, claimed to be central to love, gambling, reward, addiction, etc. A recent article by Howe et al. shows a bit more nuance than previously assumed in what dopamine levels are signaling. They ramp up during navigation towards an expected reward. I thought I would pass on a clip from Niv's summary of their findings, followed by the Howe et al. abstract

a, Dopaminergic neurons in the midbrain project to all brain areas, most prominently to the striatum (black arrows). These cells fire at a constant rate of 3–5 spikes per second, with occasional phasic bursts or pauses on the occurrence of positive reward prediction errors (discovering that the local supermarket now supplies your favourite coffee beans, b) or negative reward prediction errors (sipping your coffee and finding that the milk has gone sour, c), respectively. The background (tonic) level of dopamine fluctuates slowly, possibly tracking the average rate of rewards (not shown). d, By measuring dopamine concentrations in the striatum of rats navigating mazes, Howe et al.1 reveal a third mode of dopaminergic signalling: when a prolonged series of actions must be completed to obtain a reward (for instance, all the steps it takes to make a cup of coffee), dopamine concentration ramps up gradually, at each point in time signalling the predicted distance from the goal.

The abstract:

Predictions about future rewarding events have a powerful influence on behaviour. The phasic spike activity of dopamine-containing neurons, and corresponding dopamine transients in the striatum, are thought to underlie these predictions, encoding positive and negative reward prediction errors. However, many behaviours are directed towards distant goals, for which transient signals may fail to provide sustained drive. Here we report an extended mode of reward-predictive dopamine signalling in the striatum that emerged as rats moved towards distant goals. These dopamine signals, which were detected with fast-scan cyclic voltammetry (FSCV), gradually increased or—in rare instances—decreased as the animals navigated mazes to reach remote rewards, rather than having phasic or steady tonic profiles. These dopamine increases (ramps) scaled flexibly with both the distance and size of the rewards. During learning, these dopamine signals showed spatial preferences for goals in different locations and readily changed in magnitude to reflect changing values of the distant rewards. Such prolonged dopamine signalling could provide sustained motivational drive, a control mechanism that may be important for normal behaviour and that can be impaired in a range of neurologic and neuropsychiatric disorders.

Interesting…thinking about science enhances moral behavior.

There have been a number of high profile cases of dishonesty in reporting scientific results over the past ten years, but these errors in the conduct of the scientific method may not change public attitude towards scientific method itself. Ma-Kellams and Blascovich, using the usual cohort of university undergraduates as subjects (this time at Univ. of California Santa Barbara) show that exposure to science and experimental primes of science increase the likelihood of enforcing moral norms, Thinking about science had a moralizing effect on several domains: interpersonal violations, prosocial intentions, and economic exploitation. The experiments tested whether inducing thoughts about science could influence both reported, as well as actual, moral behavior by "priming" students with expose words like “logical,” “hypothesis,” “laboratory” and “theory.” They then judged the severity of a date-rape transgression, determined the level of altruistic activities they intended over the next month, and did a behavioral economic game that measures the level of altruistic motivation. The author's conclusions:

These studies demonstrated the morally normative effects of lay notions of science. Thinking about science leads individuals to endorse more stringent moral norms and exhibit more morally normative behavior. These studies are the first of their kind to systematically and empirically test the relationship between science and morality. The present findings speak to this question and elucidate the value-laden outcomes of the notion of science.

The social pathologies generated by connectivity and internet echo-chambers.

I have to pass on two zinger's from today's paper, a nice piece by Bruni, written during a Shanghai stay, on the ease of keeping your personal world cocoon intact through your iPad and ignoring the real world around you. And second, an article by Bilton on how many moments of our lives we are not really present because we are looking at a smartphone. Brief clips:

...Every experience is being mediated and conceived around how it can be captured and augmented by our devices...No place is this more apparent than our meals, where every portion leading up to, during and after a dining experience is being carved out by particular apps...People make dinner reservations on OpenTable; check in on Foursquare when they arrive at the restaurant; take a picture of their food to share on Instagram; post on Twitter a joke they hear during the meal; review the restaurant on Yelp; then, finally, coordinate a ride home using Uber.

The article also points to a sobering video that has gone viral (18 million viewing as I write this). I have embedded it here:



Maybe the situation isn't hopeless, because the iPhone is only really six years old, and Bilton cites a hopeful precedent:

In the late 1950s, televisions started to move into the kitchen from the living room, often wheeled up to the dinner table to join the family for supper. And then, TV at the dinner table suddenly became bad manners. Back to the living room the TV went.

Second language training reorganizes right hemisphere areas.

Hosoda et al. do a clear demonstration of how first and second languages mainly recruit different part of the brain. Training in a second language correlates with enlargement of parts of the right hemisphere, not the innately favored left hemisphere language areas used by the first language.

It remains unsettled whether human language relies exclusively on innately privileged brain structure in the left hemisphere or is more flexibly shaped through experiences, which induce neuroplastic changes in potentially relevant neural circuits. Here we show that learning of second language (L2) vocabulary and its cessation can induce bidirectional changes in the mirror-reverse of the traditional language areas. A cross-sectional study identified that gray matter volume in the inferior frontal gyrus pars opercularis (IFGop) and connectivity of the IFGop with the caudate nucleus and the superior temporal gyrus/supramarginal (STG/SMG), predominantly in the right hemisphere, were positively correlated with L2 vocabulary competence. We then implemented a cohort study involving 16 weeks of L2 training in university students. Brain structure before training did not predict the later gain in L2 ability. However, training intervention did increase IFGop volume and reorganization of white matter including the IFGop-caudate and IFGop-STG/SMG pathways in the right hemisphere. These “positive” plastic changes were correlated with the gain in L2 ability in the trained group but were not observed in the control group. We propose that the right hemispheric network can be reorganized into language-related areas through use-dependent plasticity in young adults, reflecting a repertoire of flexible reorganization of the neural substrates responding to linguistic experiences.

Nocebo pain facilitation occurs at spinal cord level.

I have had the impression that placebo and nocebo effects were the province of higher cortical brain machinations, the power of suggestion tweaking our subjective experience to feeling more or less pain than in the absence of an intervention. Geuter and Büchel now make the interesting observation this power of suggestion relays right down into the spinal cord, to alter its pain signalling pathways:

Nocebo hyperalgesia is an increase in subjective pain perception after a patient or subject underwent an inert treatment without any active ingredient. For example, verbal suggestion of increased pain can enhance both pain experience and responses in pain-related cortical brain areas. However, changes in cortical pain responses may be secondary to earlier amplification of incoming pain signals within the spinal cord. To test for a potential early enhancement of pain signals in the dorsal horn of the spinal cord, we combined a nocebo heat pain paradigm with spinal functional magnetic resonance imaging in healthy volunteers. We found that local application of an inert nocebo cream on the forearm increased pain ratings compared with a control cream, and also reduced pain thresholds on the nocebo-treated skin patch. On the neurobiological level, pain stimulation induced a strong activation in the spinal cord at the level of the stimulated dermatomes C5/C6. Comparing pain stimulation under nocebo to a control pain stimulation of the same physical intensity revealed enhanced pain-related activity in the ipsilateral dorsal horn of the spinal cord. Importantly, the activation of the main effect of pain and the nocebo effect spatially overlapped. The current study thus provides direct evidence for a pain-facilitating mechanism in the human spinal cord before cortical processing, which can be activated by cognitive manipulations such as nocebo treatments.

The Innovation of Loneliness

This is a wonderful succinct video that has gone viral, and I would encourage MindBlog readers to have a look at it. I can't imagine a more effective presentation of how connectivity can destroy real community.

"Life Enhancement"

A colleague sends me material he finds on longevity, life enhancement, etc. and I thought I would pass on two links on trendy compounds du jour, galantamine and theanine. The magazine on this site offers articles on various compounds suspected to be beneficial and actually lists supporting scientific references. This is a contrast with many sites that hawk some proprietary expensive mixture of amino acids or whatever, with no documentation or journal citations pointing to original research.

Meditation factoids - enhancement of “good” genes expression, smoking reduction

Herbert Benson (of "relaxation response" fame) and collaborators have offered a study suggesting that meditation or relaxation down regulates expression of genes involved in inflammation and HPA stress axis (fight or flight) responses. Beneficial changes in genes regulating mitochondrial energy metabolism and insulin production were also noted. Here is their technical abstract:

The relaxation response (RR) is the counterpart of the stress response. Millennia-old practices evoking the RR include meditation, yoga and repetitive prayer. Although RR elicitation is an effective therapeutic intervention that counteracts the adverse clinical effects of stress in disorders including hypertension, anxiety, insomnia and aging, the underlying molecular mechanisms that explain these clinical benefits remain undetermined. To assess rapid time-dependent (temporal) genomic changes during one session of RR practice among healthy practitioners with years of RR practice and also in novices before and after 8 weeks of RR training, we measured the transcriptome in peripheral blood prior to, immediately after, and 15 minutes after listening to an RR-eliciting or a health education CD. Both short-term and long-term practitioners evoked significant temporal gene expression changes with greater significance in the latter as compared to novices. RR practice enhanced expression of genes associated with energy metabolism, mitochondrial function, insulin secretion and telomere maintenance, and reduced expression of genes linked to inflammatory response and stress-related pathways. Interactive network analyses of RR-affected pathways identified mitochondrial ATP synthase and insulin (INS) as top upregulated critical molecules (focus hubs) and NF-κB pathway genes as top downregulated focus hubs. Our results for the first time indicate that RR elicitation, particularly after long-term practice, may evoke its downstream health benefits by improving mitochondrial energy production and utilization and thus promoting mitochondrial resiliency through upregulation of ATPase and insulin function. Mitochondrial resiliency might also be promoted by RR-induced downregulation of NF-κB-associated upstream and downstream targets that mitigates stress.

The second item: Posner and collaborators find that brief meditation training induces smoking reduction

More than 5 million deaths a year are attributable to tobacco smoking, but attempts to help people either quit or reduce their smoking often fail, perhaps in part because the intention to quit activates brain networks related to craving. We recruited participants interested in general stress reduction and randomly assigned them to meditation training or a relaxation training control. Among smokers, 2 wk of meditation training (5 h in total) produced a significant reduction in smoking of 60%; no reduction was found in the relaxation control. Resting-state brain scans showed increased activity for the meditation group in the anterior cingulate and prefrontal cortex, brain areas related to self-control. These results suggest that brief meditation training improves self-control capacity and reduces smoking.

More on the Neuro-Utopians

A recent article by Benjamin Fong. "Bursting the neuro-utopian bubble" was so widely reported that I have delayed mention of it. In that article he takes on the hubris of some proponents of Obama's "Brain Activity Map Project" that I have mentioned previously. In response to extensive feedback, Fong has issued a clarification of the core of his argument which is worth excerpting here:

One way to present my view would thus be to say that I would like to see a more comprehensive view of scientific inquiry that tames its more “religious” elements, which have gravitated to a particular position that accords the study of the brain a primary importance, and the investigation of psychosocial factors a definitively secondary one...I believe that the $100 million going to the Brain Initiative shows where our priorities lie. We are still far from rectifying a gross imbalance in funding and focus, one that has stemmed, in my view, from an ardent desire for an increasing instrumental control over the world and ourselves.

I attempted to consider two conceptions of scientific inquiry, one of which (science as agent of technological mastery) has come to dominate the other (science as critical examination of our current practices). Drawing on the tradition of critical social theory, I called one “instrumental” and the other “communicative.” My point in distinguishing these two forces was not to give preference to the subordinate party but to argue for the necessity of maintaining a healthy tension between them, especially when it comes to the problem of mental health. I thus heartily agree with many responders that we need both...my concern in the piece was not with “abuses” of science but with the very desire itself and what it unconsciously represses. One does not have to be a psychoanalyst to know that our desires often make us do things of which we are not aware.

In short, it was not my primary intention to argue against the advances of neuroscience, but simply to convey a philosophical wonder about the fact that the idea of changing human physiology — transforming the human being itself — is, at least in some circles, both more “scientific” and more “realistic” than changing human society.

Song of our warming planet

A colleague in the chaos seminar group here at the Univ. of Wisconsin sent around this video translating global warming data into a musical piece. I wanted to pass it on to you, because I find it very effective....

A Song of Our Warming Planet from Ensia on Vimeo.

The Beethoven mouse - a key to auditory transduction

I have to pass on this great montage cover and its legend from the journal Neuron. The article referenced described a gene mutation that leads to progressive hearing loss.

The Beethoven mouse, like its namesake the classical music composer Ludwig von Beethoven, suffers progressive hearing loss and eventual profound deafness. In this issue, Pan et al. examined sensory transduction in inner ear hair cells of Beethoven mice, which carry a point mutation in Transmembrane channel-like 1 gene (Tmc1). They report reduced calcium permeability and reduced single-channel conductance in Beethoven hair cells relative to hair cells that expressed wild type Tmc1. The Beethoven data demonstrate that TMC1 is a component of the hair cell transduction channel. The authors found that a closely related homolog, TMC2, also functions as a component of the transduction channel. The image shows Ludwig von Beethoven as portrayed by Joseph Stieler (1820). A cross-section of the ear, including external ear, middle, and inner ear, appears below. Within the inner ear is the spiral-shaped cochlea. The inset below shows the sensory organ, or organ of Corti. At the bottom right is a scanning electron micrograph of a hair bundle from an inner hair cell, which was the main focus of the Pan et al. study. Cover montage by Emily Mills.

Early experience shapes the amygdala’s sensitivity to race.

Here is a fascinating finding. Not surprising, I suppose, but Telzer et al. show that orphan human infants raised with exposure to only same-race faces (European or Asian) have heightened amygdala responses to out-group faces than those raised with exposure to same- and other-race faces. Later age of adoption is associated with greater biases to race.

In the current study, we investigated how complete infant deprivation to out-group race impacts behavioral and neural sensitivity to race. Although monkey models have successfully achieved complete face deprivation in early life, this is typically impossible in human studies. We overcame this barrier by examining youths with exclusively homogenous racial experience in early postnatal development. These were youths raised in orphanage care in either East Asia or Eastern Europe as infants and later adopted by American families. The use of international adoption bolsters confidence of infant exposure to race (e.g., to solely Asian faces or European faces). Participants completed an emotional matching task during functional MRI. Our findings show that deprivation to other-race faces in infancy disrupts recognition of emotion and results in heightened amygdala response to out-group faces. Greater early deprivation (i.e., later age of adoption) is associated with greater biases to race. These data demonstrate how early social deprivation to race shapes amygdala function later in life and provides support that early postnatal development may represent a sensitive period for race perception.

Looking at the Posit Science brain renewal training program.

I recently did a post pointing to Patricia Marx's article on brain exercises meant to counter aging. The authors went through the training regime of Mike Merzenich's company "Posit Science." I just got the Kindle version of his new book (pub. date July 27, 2013) "Soft Wired - How the new science of brain plasticity can change your life." I got impatient with the excellent presentation of background material in parts I-III of the book that I am familiar with and noted that at the end of each chapter a URL pointed to a bibliography of original articles supporting its statements. On reaching part IV of the book, "The Brain in Retreat," after a brief scan of the text, I ditched reading the book and went straight to the richly annotated gold mine of references. Below, for example, are some slightly edited clips from the references for Chapter 19 "Losing Ground, Just By Having a Birthday!
How, more exactly, do mental and physical performance abilities change as we grow older?"...probably more than you wanted to know about how our brains and bodies lose it with aging.

I soon found that the references are a work in progress. Detailed literature citations disappear at chapter 22 then reappear with chapter 25, and then trying to pull up references for chapters 32-37 gets a "bad link" message. Both the book and the references detail hassles with getting patents on brain training exercises, forming first one, and then a second company. I would have been happy to be spared this information and would like to have seen some justification why patents and private profits were appropriate for research publicly funded by foundations and the government.

I was frustrated by Part V, "Strengthening, correction, and rejuvenation through brain training" because it was mainly a string of homilies on good living, an advertisement for Posit Science, and an account of Merzenich's personal regimes. What about actually explaing a few of the exercises??? The references did give the meat of studies testing the efficacy of various attention, memory, and language exercises.

I'm currently looking at some of the free exercises, and may get back to you if I decide to cough up the subscription fee for the whole set and really get into it.

Here then are samples from the Merzenich Ch. 19 references:

-Several hundred studies have documented changes in processing speed associated with aging. There are many measured brain process “speeds;” they ALL slow down. See Salthouse TA (2000) Aging and measures of processing speed.  Biol Psychol 45:35

-There is one interesting exception: The strength of fast inhibitory processes normally weaken, to the extent that the modulatory response characteristics of neurons in the cortex support faster successive-signal responding (because post-excitatory inhibition is weaker). This change confers no behavioral advantage because the responding in such an inhibition-impaired brain is so noisy that information that comes from signal processing with such degradation declines dramatically. See de Villers-Sidani et al (2010) Recovery of functional and structural age-related changes in the primary auditory cortex with operant training. PNAS 107:13900.

-The extensions of time required to identify successively presented inputs are, on the average, substantially longer in older populations…I identify the MIT professor Jim DiCarlo as making the most convincing arguments that the richer exploration of stimuli via repeated eye movements—more strongly expressed in young vs older individual—is a key to accurate recognition. For example, see DiCarlo JJ et al (2012)  How does the brain solve visual object recognition? Neuron 73:415.

-We commonly record correlated changes in representational accuracy and speed in variously impaired (including aging) brains…The less accurate the brain’s neurological representation of what it sees or hears or feels, the longer it takes to “get the answer right,” i.e., to resolve what it is being seen or heard or felt.

-The degradation of our ability to suppress distractors of either external or internal origin with age has been repeatedly documented in behavioral and brain imaging studies; and the susceptibility to distractors has been shown to directly contribute to forgetfulness in older and otherwise-impaired individuals.  See, as an introduction to this rapidly growing literature, Gazzaley A, D’Esposito M (2007) Top-down modulation and normal aging.  Ann NY Acad Sci 1097:67.

-Many studies have shown that the strength of modulation of brain activity by attention is weaker in most neurologically and psychiatrically impaired populations. That modulation is largely controlled by the release of the neuromodulator acetylcholine. On the statistical average, acetylcholine-based modulation progressively weakens as the decades pass by.  For an introduction to this literature, see, for example, Pekkonen E et al (2005) Cholinergic modulation of preattentive auditory processing in aging. Neuroimage 27:387

The list goes on: references on contraction of useful field of vision, changes in driving abilities with aging, hearing loss, less vestibular control, less 'executive control'

-For documentation of the multifaceted decline into a more egocentric older life, see, for example, Orth U et al (2010) Tracking the trajectory of shame, guilt and pride across the life span. J Per Soc Psychol 99:1061; or McFarland C et al (1992) Biased recollections in older adults: The role of implicit theories of aging. J Pers Soc Psychol 62:837.

How the brain shifts between purpose and habit.

Gremel et al. do a nice explication of the brain's upstairs/downstairs story, illustrating with direct electrical recordings how the mouse brain switches between different action strategies (goal-directed and habitual). Goal directed action recruits the frontal cortex while habitual action correlates more with activity in a deeper subcortical structure, the striatum. More indirect imaging data show the story is almost surely same for us. It is the upstairs stuff that is more susceptible to aging, and most of us find it more of an effort to do novel versus habitual actions as we age.

Shifting between goal-directed and habitual actions allows for efficient and flexible decision making. Here we demonstrate a novel, within-subject instrumental lever-pressing paradigm, in which mice shift between goal-directed and habitual actions. We identify a role for orbitofrontal cortex (OFC) in actions following outcome revaluation, and confirm that dorsal medial (DMS) and lateral striatum (DLS) mediate different action strategies. Simultaneous in vivo recordings of OFC, DMS and DLS neuronal ensembles during shifting reveal that the same neurons display different activities depending on whether presses are goal-directed or habitual, with DMS and OFC becoming more and DLS less engaged during goal-directed actions. Importantly, the magnitude of neural activity changes in OFC following changes in outcome value positively correlates with the level of goal-directed behavior. Chemogenetic inhibition of OFC disrupts goal-directed actions, whereas optogenetic activation of OFC specifically increases goal-directed pressing. These results also reveal a role for OFC in action revaluation, which has implications for understanding compulsive behavior.

A brain correlate of near death hallucinations and visions?

Borjigin et al. make some fascinating observations on brain activity that occurs during the moments of cardiac arrest when brain glucose levels have dropped precipitously. Activity associated with information processing briefly increases 8-fold, a burst even after 'clinical death.' Maybe this is why some patients can recall conversation happening in the operating room.

The brain is assumed to be hypoactive during cardiac arrest. However, the neurophysiological state of the brain immediately following cardiac arrest has not been systematically investigated. In this study, we performed continuous electroencephalography in rats undergoing experimental cardiac arrest and analyzed changes in power density, coherence, directed connectivity, and cross-frequency coupling. We identified a transient surge of synchronous gamma oscillations that occurred within the first 30 s after cardiac arrest and preceded isoelectric electroencephalogram. Gamma oscillations during cardiac arrest were global and highly coherent; moreover, this frequency band exhibited a striking increase in anterior–posterior-directed connectivity and tight phase-coupling to both theta and alpha waves. High-frequency neurophysiological activity in the near-death state exceeded levels found during the conscious waking state. These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.