The brain's default network - a review

Buckner et al. offer a review of work what our brains are doing when we are not focused on the external environment. This is an open access article in a new annual volume, "The Year in Cognitive Neuroscience," being initiated by the New York Academy of Sciences. (Table of contents of this first issue is here. ) I am passing on the abstract and one central figure and legend from the article:

Thirty years of brain imaging research has converged to define the brain's default network—a novel and only recently appreciated brain system that participates in internal modes of cognition. Here we synthesize past observations to provide strong evidence that the default network is a specific, anatomically defined brain system preferentially active when individuals are not focused on the external environment. Analysis of connectional anatomy in the monkey supports the presence of an interconnected brain system. Providing insight into function, the default network is active when individuals are engaged in internally focused tasks including autobiographical memory retrieval, envisioning the future, and conceiving the perspectives of others. Probing the functional anatomy of the network in detail reveals that it is best understood as multiple interacting subsystems. The medial temporal lobe subsystem provides information from prior experiences in the form of memories and associations that are the building blocks of mental simulation. The medial prefrontal subsystem facilitates the flexible use of this information during the construction of self-relevant mental simulations. These two subsystems converge on important nodes of integration including the posterior cingulate cortex. The implications of these functional and anatomical observations are discussed in relation to possible adaptive roles of the default network for using past experiences to plan for the future, navigate social interactions, and maximize the utility of moments when we are not otherwise engaged by the external world. We conclude by discussing the relevance of the default network for understanding mental disorders including autism, schizophrenia, and Alzheimer's disease.


The default network is activated by diverse forms of tasks that require mental simulation of alternative perspectives or imagined scenes. Four such examples from the literature illustrate the generality. (A) Autobiographical memory: subjects recount a specific, past event from memory. (B) Envisioning the future: cued with an item (e.g., dress), subjects imagine a specific future event involving that item. (C) Theory of mind: subjects answer questions that require them to conceive of the perspective (belief) of another person. (D) Moral decision making: subjects decide upon a personal moral dilemma. Note that all the studies activate strongly PCC/Rsp and dMPFC. Active regions also include those close to IPL and LTC, although further research will be required to determine the exact degree of anatomic overlap. It seems likely that these maps represent multiple, interacting subsystems.

More from the great curmudgeon...

To follow up my June 15 post, here is an Esquire Magazine "What I have learned" offering from Gore Vidal that my colleague Jim Steakley alterted me to. A few selections:

God has been expelled. I think he knows when he’s on a losing wicket.
I went into a line of work in which jealousy is the principle emotion between practitioners. I don’t think I ever suffered from it, because there was no need. But I was aware of it in others, and I found it a regrettable fault.
There was more of a flow to my output of writing in the past, certainly. Having no contemporaries left means you cannot say, “Well, so-and-so will like this,” which you do when you’re younger. You realize there is no so-and-so anymore. You are your own so-and-so. There is a bleak side to it.
You hear all this whining going on, “Where are our great writers?” The thing I might feel doleful about is: Where are the readers?
Some of my father’s fellow West Pointers once asked him why I turned out so well, his secret in raising me. And he said, “I never gave him any advice, and he never asked for any.” We agreed on nothing, but we never quarreled once.
Every fool I knew had gone to university. I didn’t think it necessary. I’d seen some of the results, you know?
When I was young, I was bored shitless with being desired by others. I don’t look in the mirror anymore.
I lived with Howard for fifty years, but what we had was certainly not romantic love, not passionate love. And it certainly was nonsexual. Try and explain that to the fags.
Nonprofit status is what created the Bible Belt. The tax code brought religion back to this country.
When she was running for the Senate, Hillary’s psephologists discovered that the one group that really hated her was white, middle-aged men of property. She got the whole thing immediately -- I heard she said, “I remind them of their first wife.”
“You got to meet everyone -- Jackie Kennedy, William Burroughs.” People always put that sentence the wrong way around. I mean, why not put it the true way, that these people got to meet me, and wanted to? Otherwise it sounds like I spent my life hustling around trying to meet people: “Oh, look, there’s the governor.“
For a writer, memory is everything. But then you have to test it; how good is it, really? Whether it’s wrong or not, I’m beyond caring. It is what it is. As Norman Mailer would say, “It’s existential.” He went to his grave without knowing what that word meant.
We’re the most captive nation of slaves that ever came along. The moral timidity of the average American is quite noticeable. Everybody’s afraid to be thought in any way different from everyone else.
Get rid of religion. It’ll do you no good.
As the Greeks sensibly believed, should you get to know yourself, you will have penetrated as much of the human mystery as anyone need ever know.
I wasn’t like everyone, you know. What everyone did, I was sure not to do.

A memorial for our president...

I simply can't resist passing this on - an article on a proposal, naturally hatched in a bar, to change the name of a prize-winning water treatment plant on the shoreline of San Francisco to the George W. Bush Sewage Plant. This is a memorial you can contribute to from your bathroom. The proposal has enough signatures to qualify it as an initiative on the November ballot.

Retaliation for unfairness - depends on serotonin

Nature highlights an article by Crockett et al. showing that serotonin modulates our reaction to unfairness. The experimenters:

...temporarily lowered serotonin (5-HT) levels in 20 volunteers and had them play the part of responder in the 'ultimatum game'. The responder can either accept the division of a sum of money offered by the game's proposer, in which case they both get their share, or reject it and deprive both players of the amounts proposed.

Although mood, fairness judgments, basic reward processing, or response inhibition, remained unchanged when players' serotonin levels were lowered, they were more likely to reject unfair and very unfair offers, defined as 30% and 20% of the stake, respectively.

Trust in oxytocin.

I pass on a brief news review by Leonie Welberg from Nature Neuroscience:

The neuropeptide oxytocin is released during childbirth, suckling, touch and orgasm, suggesting that it might have a 'pro-social' function. This idea was strengthened by a recent study in Nature (see my 2/13/06 post, or enter oxytocin inthe search box in the left column of this blog), which showed that an oxytocin nasal spray caused people playing a 'trust' game to retain their trust in a stranger who was looking after their money, even though this trust was violated on many occasions. At the same time, the oxytocin spray decreased activity in the amygdala and the caudate nucleus, brain areas that are involved in the regulation of fear and decision making, respectively.

"We now know ... what exactly is going on in the brain when oxytocin increases trust," says lead researcher Thomas Baumgartner of the University of Zürich, Switzerland. "It seems to diminish our fears." (BBC News, 21 May 2008.) As humans are typically averse to taking social risks, "...a little bit of oxytocin may facilitate carrying on relationships with others," according to Mauricio Delgado, a neuroscientist at Rutgers University in Newark, New Jersey. (ScienceNOW, 21 May 2008.)

How people in real-life situations develop and retain trust in others is another question, however. "They certainly don't do it by spraying stuff up each other's noses," says Paul Zak of the Center for Neuroeconomics Studies at Claremont Graduate University in California. (Science News, 21 May 2008.)

Nevertheless, the findings have implications for understanding mental disorders in which deficits in social behaviour are observed and "...could provide a bridge for potential clinical applications," thinks Delgado (BBC News). An oxytocin spray might help people with a social phobia or autism. "Autistic people also have a fear of social situations and have problems interacting, so it is very likely that oxytocin could help," says Baumgartner. "This hormone seems to play a very specific role in social situations so might be able to improve autism." (BBC News.)

Are the religionists lightening up?

The graphic is from Banerjee's NYTimes summary of the Pew Forum report. The good news is that while the vast majority of Americans (many more than Western Europeans) believe in "God" and eternal life, more accept that there are varieties of Pearly Gates, and how you might get to them. Better yet, fewer get anthropomorphic about it, citing 'an impersonal force' as closer to their idea of God, and thus might be more friendly to the sort of emergence models mentioned in the previous post.

Can 'emergence' put spirituality back into nature?

The anti-reductionist view of emergence undergoes cycles of popularity as a philosophical topic. Valerie Hardcastle gives a rather critical review (in Jour. Consciousness Studies, Vol. 14, No. 11, pp.119-122) of a recent collection "The Re-Emergence of Emergence - The Emergentist Hypothesis from Science to Religion" edited by Clayton and Davies (Oxford Univ. Press, 2006). This emergentism is 'feel good' stuff. I think most of us get a bit frightened and a bit dried and shriveled up at the implications of strong reductionism in which all the explanatory arrows point down. Reversing the reductionist’s causal arrow with a comprehensive theory of emergence and self-organization that breaks no laws of physics and yet cannot be explained by them is a laudable project, but as Hardcastle wryly notes, one that continues to fail the "where's the beef" test.

Michael Shermer offers a very appealing gloss in his "Skeptic" column in the Scientific American, with the title: Sacred Science - Can emergence break the spell of reductionism and put spirituality back into nature? He specifically reviews a new book by Stuart Kauffman, Reinventing the Sacred (Basic Books, 2008). Denis Noble also reviews Kauffman's book in Science Magazine. Here are some clips from Shermer's column:
Kaufman:

...reverses the reductionist’s causal arrow with a comprehensive theory of emergence and self-organization that Kaufman says “breaks no laws of physics” and yet cannot be explained by them. God “is our chosen name for the ceaseless creativity in the natural universe, biosphere and human cultures.” In Kauffman’s emergent universe, reductionism is not wrong so much as incomplete. It has done much of the heavy lifting in the history of science, but reductionism cannot explain a host of as yet unsolved mysteries, such as the origin of life, the biosphere, consciousness, evolution, ethics and economics... How would a reductionist explain the biosphere, for example? “One approach would be, following Newton, to write down the equations for the evolution of the biosphere and solve them. This cannot be done,” Kauffman avers. “We cannot say ahead of time what novel functionalities will arise in the biosphere. Thus we do not know what variables—lungs, wings, etc.—to put into our equations. The Newtonian scientific framework where we can prestate the variables, the laws among the variables, and the initial and boundary conditions, and then compute the forward behavior of the system, cannot help us predict future states of the biosphere.”... This problem is not merely an epistemological matter of computing power, Kauffman cautions; it is an ontological problem of different causes at different levels. Something wholly new emerges at these higher levels of complexity.

Similar ontological differences exist in the self-organized emergence of consciousness, morality and the economy...economics and evolution are complex adaptive systems that learn and grow as they evolve from simple to complex...they are autocatalytic, containing self-driving feedback loops...such phenomena “cannot be deduced from physics, have causal powers of their own, and therefore are emergent real entities in the universe.” This creative process of emergence, Kauffman contends, “is so stunning, so overwhelming, so worthy of awe, gratitude and respect, that it is God enough for many of us. God, a fully natural God, is the very creativity in the universe.”

Shermer ends noting that Kaufman's:

God 2.0 is a deity worthy of worship. But I am skeptical that it will displace God 1.0, Yahweh, whose Bronze Age program has been running for 6,000 years on the software of our brains and culture.

Brain exercise/fitness links...

Tom Hanson, the Editor of OpenEducation.net, asks me to pass on these two separate posts on brain exercise/fitness, noting some firms that I have mentioned previously, and so I do this as a professional courtesy.

Strengths and Limits of fMRI studies on the brain

Nikos Logothetis offers a long and detailed discussion of what we can and cannot learn from brain imaging approaches. I'm giving a few clips from his discussion:

fMRI is not and will never be a mind reader, as some of the proponents of decoding-based methods suggest, nor is it a worthless and non-informative 'neophrenology' that is condemned to fail, as has been occasionally argued.

The principal advantages of fMRI lie in its noninvasive nature, ever-increasing availability, relatively high spatiotemporal resolution, and its capacity to demonstrate the entire network of brain areas engaged when subjects undertake particular tasks. One disadvantage is that, like all haemodynamic-based modalities, it measures a surrogate signal whose spatial specificity and temporal response are subject to both physical and biological constraints. A more important shortcoming is that this surrogate signal reflects neuronal mass activity.


Figure - Two slices of GE-EPI demonstrating the high functional signal-to-noise ratio (SNR) of the images, but also the strong contribution of macrovessels. The yellow areas (indicated with the green arrows) are pia vessels, an example of which is shown in the inset scanning electron microscopy image (total width of inset, 2 mm). For the functional images red indicates low and yellow indicates high.

MRI may soon provide us with images of a fraction of a millimetre (for example, 300 x 300 m² with a couple of millimetres slice thickness or 500 x 500 x 500 m³ isotropic), which amount to voxel volumes of about two–three orders of magnitude smaller than those currently used in human imaging. With an increasing number of acquisition channels such resolution may ultimately be attained in whole-head imaging protocols, yielding unparalleled maps of distributed brain activity in great regional detail and with reasonable—a couple of seconds—temporal resolution. Would that be enough for using fMRI to understand brain function?

The answer obviously depends on the scientific question and the spatial scale at which this question could be addressed—"it makes no sense to read a newspaper with a microscope", as neuroanatomist Valentino Braitenberg once pointed out. To understand the functioning of the microcircuits in cortical columns or of the cell assemblies in the striosomes of basal ganglia, one must know a great deal about synapses, neurons and their interconnections. To understand the functioning of a distributed large-scale system, such as that underlying our memory or linguistic capacities, one must first know the architectural units that organize neural populations of similar properties, and the interconnections of such units. With 10¹⁰ neurons and 10¹⁴ connections in the cortex alone, attempting to study dynamic interactions between subsystems at the level of single neurons would probably make little sense, even if it were technically feasible. It is probably much more important to understand better the differential activity of functional subunits—whether subcortical nuclei, or cortical columns, blobs and laminae—and the instances of their joint or conditional activation. If so, whole-head imaging with a spatial resolution, say, of 0.7 0.7 mm² in slices of 1-mm thickness, and a sampling time of a couple of seconds, might prove optimal for the vast majority of questions in basic and clinical research. More so, because of the great sensitivity of the fMRI signal to neuromodulation. Neuromodulatory effects, such as those effected by arousal, attention, memory, and so on, are slow and have reduced spatiotemporal resolution and specificity.

Logothesis offers a concluding perspective.

The limitations of fMRI are not related to physics or poor engineering, and are unlikely to be resolved by increasing the sophistication and power of the scanners; they are instead due to the circuitry and functional organization of the brain, as well as to inappropriate experimental protocols that ignore this organization. The fMRI signal cannot easily differentiate between function-specific processing and neuromodulation, between bottom-up and top-down signals, and it may potentially confuse excitation and inhibition. The magnitude of the fMRI signal cannot be quantified to reflect accurately differences between brain regions, or between tasks within the same region. The origin of the latter problem is not due to our current inability to estimate accurately cerebral metabolic rate of oxygen (CMRO2) from the BOLD signal, but to the fact that haemodynamic responses are sensitive to the size of the activated population, which may change as the sparsity of neural representations varies spatially and temporally. In cortical regions in which stimulus- or task-related perceptual or cognitive capacities are sparsely represented (for example, instantiated in the activity of a very small number of neurons), volume transmission (see Supplementary Information)—which probably underlies the altered states of motivation, attention, learning and memory—may dominate haemodynamic responses and make it impossible to deduce the exact role of the area in the task at hand. Neuromodulation is also likely to affect the ultimate spatiotemporal resolution of the signal.

This having been said, and despite its shortcomings, fMRI is currently the best tool we have for gaining insights into brain function and formulating interesting and eventually testable hypotheses, even though the plausibility of these hypotheses critically depends on used magnetic resonance technology, experimental protocol, statistical analysis and insightful modelling. Theories on the brain's functional organization (not just modelling of data) will probably be the best strategy for optimizing all of the above. Hypotheses formulated on the basis of fMRI experiments are unlikely to be analytically tested with fMRI itself in terms of neural mechanisms, and this is unlikely to change any time in the near future.

Neuro-puffs and neuropundits...

Check out this debunking of neuroimaging research on things like political partisanship and superbowl commercials.

A new perspective on culture-specific behavior

Yamagishi et al. demonstrate that the East Asian "preference" for conformity is actually a default strategy to avoid accrual of negative reputation. When the possibility for negative evaluations in a given situation was clearly defined, cultural differences in the tendency for uniqueness disappeared. The framework for analyzing the motivations for choices made by Japanese and Americans in a simple task is described in a summary in Science.

When offered a single colored pen from a group of five pens as a token payment for filling out a survey, Hokkaido students were less likely than Wolverines (Michigan students) to take a particular pen if it were the only one of that color available--that is, they would avoid reducing the scope of choice for subsequent people and thus, by incurring the cost of passing up the uniquely colored pen, not run the risk of making a negative impression on others. In contrast, a cultural psychological assessment would explain this outcome as revealing the preference (higher valuation) that East Asians place on conformity as opposed to the affinity of Westerners for individualism. When the choice task was expanded to include situations where the student was told explicitly that he was the first or the last of the five students to receive pens, the East-West difference disappeared; both Japanese and Americans were less likely to take the uniquely colored if they were the first and more likely (equally so) if they were the last to choose.

Yamagishi et al. suggest that:

... while cultural psychological perspectives are commendable for bringing culture into the mainstream of psychology, they have tended to be oversimplistic in attributing the cause of culture-specific behaviors to internalized cultural norms and values.

Their approach to the issue of the culturally grounded nature of human behavior is:

... from a game-theoretic perspective, and proposes an institutional approach as an alternative to the cultural psychology approach. The institutional approach to cultural differences views culture-specific behavior as strategies adapted to a set of collectively created social incentives. In this framework, no psychological concepts such as self-construals are required to interpret cultural differences, and thus the institutional approach can provide a more parsimonious explanation of cultural differences that can extend toward social science disciplines outside of psychology.

A population genetic analysis of male homosexuality

As a companion to the previous post, I pass along this article by Ciani et al. arguing that only a two-locus genetic model for male homosexuality with at least one locus on the X chromosome, in which gene expression is sexually antagonistic (increasing female fitness but decreasing male fitness), accounts for all the known empirical data. That data is interesting (as described in this account in Slate):

It starts with four curious patterns. First, male homosexuality occurs at a low but stable frequency in a wide range of societies. Second, the female relatives of gay men produce children at a higher rate than other women do. Third, among these female relatives, those related to the gay man's mother produce children at a higher rate than do those related to his father. Fourth, among the man's male relatives, homosexuality is more common in those related to his mother than in those related to his father.

More on gay and straight brains.

A recent study notes that in several measures of brain symmetry, straight men and gay women were similar, and gay men and straight women were similar. MindHacks points out a further interesting feature: that amygdala reactivity to simply breathing unscented air (thus having nothing obvious to do with sexual preference or activity per se) is different in gay and straight men and women. This is yet more evidence that sexual preference is not determined solely by individual developmental experience. Here is the complete abstract of the Savic and Per Lindström article, followed by the PET scan amygdala data, which speaks for itself, and finally a clip from the discussion. PDF of article here.

Cerebral responses to putative pheromones and objects of sexual attraction were recently found to differ between homo- and heterosexual subjects. Although this observation may merely mirror perceptional differences, it raises the intriguingquestion as to whether certain sexually dimorphic features in the brain may differ between individuals of the same sex but different sexual orientation. We addressed this issue by studying hemispheric asymmetry and functional connectivity, two parameters that in previous publications have shown specific sex differences. Ninety subjects [25 heterosexual men (HeM) and women (HeW), and 20 homosexual men (HoM) and women (HoW)] were investigated with magnetic resonance volumetry of cerebral and cerebellar hemispheres. Fifty of them also participated in PET measurements of cerebral blood flow, used for analyses of functional connections from the right and left amygdalae. HeM and HoW showed a rightward cerebral asymmetry, whereas volumes of the cerebral hemispheres were symmetrical in HoM and HeW. No cerebellar asymmetries were found. Homosexual subjects also showed sex-atypical amygdala connections. In HoM, as in HeW, the connections were more widespread from the left amygdala; in HoW and HeM, on the other hand, from the right amygdala. Furthermore, in HoM and HeW the connections were primarily displayed with the contralateral amygdala and the anterior cingulate, in HeM and HoW with the caudate, putamen, and the prefrontal cortex. The present study shows sex-atypical cerebral asymmetry and functional connections in homosexual subjects. The results cannot be primarily ascribed to learned effects, and they suggest a linkage to neurobiological entities.

From the discussion:

HeW and HoM displayed more pronounced between-amygdala connections and greater connections with the anterior cingulate, the subcallosum, and the hypothalamus. This connectivity pattern provides a strong substrate for processing of external stimuli that are relayed by the two amygdalae and represents a possible pathway for their functional interconnection in HeW and HoM. The remarkable similarity between HeW and HoM in the connectivity pattern deserves special attention. The amygdala has a key role in emotional reactions to external stimuli, including stress; the subcallosum and the anterior cingulate, on the other hand, are highly involved in mediation of mood and anxiety-related processes. Affective disorders are 2–3 times more common in women than men, and the tight functional connections between the amygdala and cingulate in women is currently discussed as a possible neurobiological substrate for their higher vulnerability, in addition to the effects of estrogen and testosterone. Interestingly, the incidence of depression and suicide attempts is elevated in homosexual subjects, and HoM in particular. Although the underlying mechanisms are likely to be multifactorial and include social pressure, the presently observed similarity with HeW vis-a`-vis the amygdala connectivity motivates further evaluations.

A new mind blog...

At the risk of promoting further blog overload, I've added the Psychology Today blog to the 'other mind blogs' list just under 'Archives' in the right column. It has some good stuff.

Increasing complexity of nerve synapses during evolution

Nicholas Wade points to the work of Grant and colleagues on how the complexity of nerve interconnections (synapses) has increased during evolution as the variety of their protein components has increased from a few to several hundred. Vertebrate synapses have about 1,000 different proteins, assembled into 13 molecular machines, one of which is built from 183 different proteins. The human brain has about 100 billion neurons, interconnected at 100 trillion synapses. Grant provides an analogy:

If the synapses are thought of as the chips in a computer, then brainpower is shaped by the sophistication of each chip, as well as by their numbers...From the evolutionary perspective, the big brains of vertebrates not only have more synapses and neurons, but each of these synapses is more powerful — vertebrates have big Internets with big computers and invertebrates have small Internets with small computers.

The top part of the figure (click to enlarge) shows the phylogenetic relationships of the species studied. The number of varieties of two signaling complexes, NMDA receptor (NRC or MASC) / postsynaptic density (PSD) are in parentheses. The lower half shows the occurrences of PSD and MASC homologs found in each of the 19 species as a percentage of those found in human.

Evolutionary Psychology as Maladapted Psychology

Bolhuis reviews a book with the title of this post by philosopher Robert Richardson. (I have read a longer excellent book, "Adapting Minds", by philosopher David Buller. Here are some clips from the review:

Evolutionary psychology aims to apply evolutionary theory to the human mind. Specifically, it proposes that the mind consists of cognitive modules that evolved in response to selection pressures faced by our Stone Age ancestors. The approach has a wide popular appeal, perhaps because it often addresses such exciting topics as human desire, sex, and passion....Richardson readily acknowledges that our psychological capacities are evolved traits subject to natural selection. But at the same time, he maintains that there is very little we can find out about the evolution of the mind and that the evolutionary psychology interpretation is wrong from the perspective of evolutionary biology...he criticizes mainly the methods used by evolutionary psychologists, weighing the approach's theoretical framework using criteria from evolutionary biology...The main problem with evolutionary psychology is that it usually does not consider alternative explanations but takes the assumption of adaptation through natural selection as given.

Richardson rightly suggests that paleontologists are unlikely to unearth the evidence that can inform us about the social structure of our ancestral communities. I think one can go a step further. Even if we would be able to muster the evidence needed for an evolutionary psychological analysis of human cognition, it would not tell us anything about our cognitive mechanisms. The study of evolution is concerned with a historical reconstruction of traits. It does not, and cannot, address the mechanisms that are involved in the human brain. Those fall within the domains of neuroscience and cognitive psychology. In that sense, evolutionary psychology will never succeed, because it attempts to explain mechanisms by appealing to the history of these mechanisms. To use the author's words, "We might as well explain the structure of orchids in terms of their beauty." In this excellent book, Richardson shows very clearly that attempts at reconstruction of our cognitive history amount to little more than "speculation disguised as results." The book's title implies that the field is itself subject to selection pressure. Richardson is certainly piling it on.

Anticipating the Future to ‘See’ the Present

The title of this post is also the title of an article by Benedict Carey that describes works supporting the idea that the brain uses a bag of ad hoc tricks to build a streaming model of the world. Because it takes the brain at least a tenth of a second to model visual information, it is always working with old information. The argument is that the brain has evolved to meet this problem by projecting or guessing a split second into the future when it perceives motion. By modeling the future during movement, it is “seeing” the present. These two illusions illustrate the process:

Leaning toward the image makes it appear as if it is bulging.

The radiating lines trick the brain into perceiving motion forward, so the center appears to bulge.

Evaluating mental exercises

This article on pumping up your little grey cells in the Times of London is worth reading, also this New Scientist article.

Schizophrenia and the Brain

Here is a very nice instructional video from Thompson at UCLA, whose images I have shown in previous posts, showing brain developmental differences in normal and schizophrenic children between the ages of 4 and 21. It also shows how recently developed drugs inhibit the degenerative changes.

Social cognition in plants?

I suppose it is a bit of a stretch to call it social cognition, but it is recognition of kin and non-kin species, now discovered in plants. This is a bit of a shock, in part because most animals have not even been shown to have the ability to recognize relatives, despite the huge advantages in doing so. Some plants not only avoid competing with kin by not sending roots towards them, but also sniff out their victims. We're talking about careful experiments here, not New Age fantasies about plant feelings and sentience. Check out the account by Yoon. This excerpt is from its ending:

Recent debates have revolved around a longstanding question: which of the abilities and attributes that scientists have long considered the realm of just animals, like sensing, learning and memory, can sensibly be transferred to plants?...At the extreme of the equality movement, but still within mainstream science, are the members of the Society of Plant Neurobiology, a new group whose Web site describes it as broadly concerned with plant sensing....The very name of the society is enough to upset many biologists. Neurobiology is the study of nervous systems — nerves, synapses and brains — that are known just in animals. That fact, for most scientists, makes the notion of plant neurobiology a combination of impossible, misleading and infuriating....Thirty-six authors from universities that included Yale and Oxford were exasperated enough to publish an article last year, “Plant Neurobiology: No Brain, No Gain?” in the journal Trends in Plant Science. The scientists chide the new society for discussing possibilities like plant neurons and synapses, urging that the researchers abandon such “superficial analogies and questionable extrapolations.”

Defenders point out that 100 years ago, some scientists were equally adamant that plant physiology did not exist. Today, that idea is so obviously antiquated that it could elicit a good chuckle from the many scientists in that field...As for the “superficial analogies,” the new wave botanists are well aware that plants do not have exact copies of animal nervous systems...“No one proposes that we literally look for a walnut-shaped little brain in the root or shoot tip,” five authors wrote in defense of the new group. Instead, the researchers say, they are asking that scientists be open to the possibility that plants may have their own system, perhaps analogous to an animal’s nervous system, to transfer information around the body....“Plants do send electrical signals from one part of the plant to another,” said Dr. Eric D. Brenner, a botanist at the New York Botanical Garden and a member of the Society of Plant Neurobiology...Although those signals have been known for 100 years, scientists have no idea what plants do with them...“No one’s asked how all that information is integrated in a plant, partly because we’ve convinced ourselves that it isn’t,” Dr. Brenner said. “People have been intimidated from asking that question.”