[with apologies to Retro-A-Go-Go!]
Subscribe to Post Comments [Atom]
Deconstructing the most sensationalistic recent findings in Human Brain Imaging, Cognitive Neuroscience, and Psychopharmacology
No, of course not. The question really is, does your precuneus make you conscious?
Andrea E. Cavanna and Michael R. Trimble (2006). The precuneus: a review of its functional anatomy and behavioural correlates. Brain 129: 564-583.The precuneus seemed poised to break out into the mainstream in the mid-90's, ever since it was found to be highly active when people were remembering words from a list they had studied earlier (compared to new words they hadn't studied). At first, this activity seemed related to the use of mental imagery during retrieval (Fletcher et al., 1995), because precuneus activity increased for highly concrete and imageable word pairs (e.g., "River-Stream") but not for abstract word pairs (e.g., "Justice-Law"). Subsequent experiments, however, did not replicate this result (Krause et al., 1999).
Functional neuroimaging studies have started unravelling unexpected functional attributes for the posteromedial portion of the parietal lobe, the precuneus. This cortical area has traditionally received little attention, mainly because of its hidden location and the virtual absence of focal lesion studies. However, recent functional imaging findings in healthy subjects suggest a central role for the precuneus in a wide spectrum of highly integrated tasks, including visuo-spatial imagery, episodic memory retrieval and self-processing operations, namely first-person perspective taking and an experience of agency. Furthermore, precuneus and surrounding posteromedial areas are amongst the brain structures displaying the highest resting metabolic rates (hot spots) and are characterized by transient decreases in the tonic activity during engagement in non-self-referential goal-directed actions (default mode of brain function). Therefore, it has recently been proposed that precuneus is involved in the interwoven network of the neural correlates of self-consciousness, engaged in self-related mental representations during rest. This hypothesis is consistent with the selective hypometabolism in the posteromedial cortex reported in a wide range of altered conscious states, such as sleep, drug-induced anaesthesia and vegetative states. ... [The authors describe] preliminary evidence for a functional subdivision within the precuneus into an anterior region, involved in self-centred mental imagery strategies, and a posterior region, subserving successful episodic memory retrieval.
the precuneus and interconnected posterior cingulate and medial prefrontal cortices are engaged in continuous information gathering and representation of the self and external world (Gusnard and Raichle, 2001).The "self-representation" part appears to be off in autistic individuals (Kennedy et al., 2006), because they fail to "engage" the default mode network during rest, relative to an active cognitive task condition. But in the same vein as the critique of the "Lose Yourself" study, a relatively quiet precuneus don't necessarily mean you're not conscious, it can just reflect a focus on things other than yourself and your surroundings. So perhaps the precuneus and its network of friends contribute to our "self-conscious" state.
Alzheimer's disease (AD) and antecedent factors associated with AD were explored using amyloid imaging and unbiased measures of longitudinal atrophy in combination with reanalysis of previous metabolic and functional studies. In total, data from 764 participants were compared across five in vivo imaging methods. Convergence of effects was seen in posterior cortical regions, including posterior cingulate, retrosplenial, and lateral parietal cortex. These regions were active in default states in young adults and also showed amyloid deposition in older adults with AD. At early stages of AD progression, prominent atrophy and metabolic abnormalities emerged in these posterior cortical regions; atrophy in medial temporal regions was also observed. Event-related functional magnetic resonance imaging studies further revealed that these cortical regions are active during successful memory retrieval in young adults. One possibility is that lifetime cerebral metabolism associated with regionally specific default activity predisposes cortical regions to AD-related changes, including amyloid deposition, metabolic disruption, and atrophy. These cortical regions may be part of a network with the medial temporal lobe whose disruption contributes to memory impairment.So basically, the idea is that an overactive self-referential default-mode network burns itself out, somehow leading to the pathological state associated with amyloid deposition, neuronal death, severe brain atrophy, and the ultimate loss of self which occurs in that dreadful disease named after Alois Alzheimer.
Next in a continuing series on hypnosis:
What is hypnosis and how to induce itAnd after writing that lengthy dissertation or grant proposal, it's time to enter a fugue state...
There is not a generally accepted definition of hypnosis. For many authors it is seen as a state of focused attention, concentration and inner absorption with a relative suspension of peripheral awareness (Laureys et al., in press).
Hypnosis has three main components: absorption, dissociation and suggestibility (Spiegel, 1991). Absorption is the tendency to become fully involved in a perceptual, imaginative or ideational experience. Subjects prone to this type of cognition are more highly hypnotizable than others who never fully engage in such experience (Hilgard et al., 1963). Dissociation is the mental separation of components of behavior that would ordinarily be processed together (e.g., the dream-like state of being both actor and observer when re-experiencing autobiographical memories). This may also involve a sense of involuntariness in motor functions or discontinuities in the sensations of one part of the body compared with another. Suggestibility leads to an enhanced tendency to comply with hypnotic instructions. This represents not a loss of will butrather a suspension of critical judgment because of the intense absorption of the hypnotic state.Hmmm, "suspension of critical judgment" -- that's not gonna happen here. But what are the "neural correlates" of a hypnotic state?
This area is hypothesized to be involved in the representation (monitoring) of the world around us (Gusnard and Raichle, 2001).Raichle and colleagues have argued for a "default mode" or "resting state" of brain function that engages a certain network of brain regions (posterior cingulate and precuneus and medial prefrontal cortex) during "rest." These regions become DEactivated when people are engaged in the typical types of cognitive tasks they're asked to do in a scanner. So it's really only a "resting state" when compared to doing, say, the Stroop task. When asked to rest and stare at a plus sign, you may engage in idle daydreaming or think about what you'll have for dinner or remember your hot date from last night or silently sing.
"No, no, no, don't try any of that cow hypnosis on me, all right? It's not gonna work!"
"cholinergic systems arising in the basal forebrain play an important role in orienting; the norepinephrine (NE) system arising in the locus coeruleus of the midbrain is involved in alerting; and the anterior cingulate cortex (ACC) and lateral prefrontal cortex are target areas of the mesocortical dopamine system -- involved in executive attention."It sounds nice, but it's hard to imagine the "one attentional system, one neurotransmitter" mapping is correct.
"...evidence relating hypnotic phenomena to attentional mechanisms is mounting (Raz et al., 2002b) and there is general accord that hypnotic phenomena implicate attention (Karlin, 1979) and relate to self-regulation (Posner and Rothbart, 1998)."I guess we'll have to take their word for it (or else read the cited references). At any rate, the major intersection between attention and hypnosis in the research realm has been elimination of the well-known Stroop interference effect in highly hypnotizable people who are under a specific post-hypnotic suggestion to avoid reading the words (Raz et al., 2002b, 2003, 2005, 2006), which is usually considered a pretty darn automatic process.
"Drugs known to affect the dopaminergic system as well as alter consciousness (e.g., propofol) seem to induce hypnosis-like experiences and modulate executive attention (DiFlorio, 1993; Fiset et al., 1999; Rainville et al., 2002; Xie et al., 2004)."
COMT (catechol-O-methyltransferase) catalyzes the transfer of a methyl group from S-adenosylmethionine to catecholamines, including the neurotransmitters dopamine, epinephrine, and norepinephrine. This O-methylation results in one of the major degradativeSo basically, COMT is an enzyme that breaks down all catecholemines, not just dopamine. And both DA and NE have effects on prefrontal cortex.
pathways of the catecholamine transmitters.
Arnsten AF, Li BM.Nonetheless, the overall finding on suggestion and Stroop is interesting, even if the genetics at this point are questionable.
Neurobiology of executive functions: catecholamine influences on prefrontal cortical functions.
Biol Psychiatry. 2005 57(11):1377-84. Review.
The prefrontal cortex guides behaviors, thoughts, and feelings using representational knowledge, i.e., working memory. These fundamental cognitive abilities subserve the so-called executive functions: the ability to inhibit inappropriate behaviors and thoughts, regulate our attention, monitor our actions, and plan and organize for the future. Neuropsychological and imaging studies indicate that these prefrontal cortex functions are weaker in patients with attention-deficit/hyperactivity disorder and contribute substantially to attention deficit/hyperactivity disorder symptomology. Research in animals indicates that the prefrontal cortex is very sensitive to its neurochemical environment and that small changes in catecholamine modulation of prefrontal cortex cells can have profound effects on the ability of the prefrontal cortex to guide behavior. Optimal levels of norepinephrine acting at postsynaptic α-2A-adrenoceptors and dopamine acting at D1 receptors are essential to prefrontal cortex function. Blockade of norepinephrine α-2-adrenoceptors in prefrontal cortex markedly impairs prefrontal cortex function and mimics most of the symptoms of attention-deficit/hyperactivity disorder, including impulsivity and locomotor hyperactivity. Conversely, stimulation of α-2-adrenoceptors in prefrontal cortex strengthens prefrontal cortex regulation of behavior and reduces distractibility. Most effective treatments for attention-deficit/hyperactivity disorder facilitate catecholamine transmission and likely have their therapeutic actions by optimizing catecholamine actions in prefrontal cortex.
While the media focus was on "Medical Road Rage," another article in the June 2006 issue of the Archives of General Psychiatry was more interesting to The Neurocritic:
Schmahl C, Bohus M, Esposito F, Treede RD, Di Salle F, Greffrath W, Ludaescher P, Jochims A, Lieb K, Scheffler K, Hennig J, Seifritz E.Do borderline patients injure themselves to "feel" (or "feel more normal") OR to down-regulate the emotional components of pain? The results don't really answer this question or the question posed in my title, but the authors give 2 options:
Neural correlates of antinociception in borderline personality disorder.
Arch Gen Psychiatry. 2006 Jun;63(6):659-66.
CONTEXT: A characteristic feature of borderline personality disorder (BPD) is self-injurious behavior in conjunction with stress-induced reduction of pain perception. Reduced pain sensitivity has been experimentally confirmed in patients with BPD, but the neural correlates of antinociceptive mechanisms in BPD are unknown. We predicted that heat stimuli in patients with BPD would activate brain areas concerned with cognitive and emotional evaluation of pain. OBJECTIVE: To assess the psychophysical properties and neural correlates of altered pain processing in patients with BPD. DESIGN: Case-control study. SETTING: A university hospital. PARTICIPANTS: Twelve women with BPD and self-injurious behavior and 12 age-matched control subjects. INTERVENTIONS: Psychophysical assessment and blood oxygen level-dependent functional magnetic resonance imaging during heat stimulation with fixed-temperature heat stimuli and individual-temperature stimuli adjusted for equal subjective pain in all the participants. Main Outcome Measure Blood oxygen level-dependent functional magnetic resonance imaging signal changes during heat pain stimulation. RESULTS: Patients with BPD had higher pain thresholds and smaller overall volumes of activity than controls in response to identical heat stimuli. When the stimulus temperature was individually adjusted for equal subjective pain level, overall volumes of activity were similar, although regional patterns differed significantly. Patient response was greater in the dorsolateral prefrontal cortex and smaller in the posterior parietal cortex. Pain also produced neural deactivation in the perigenual anterior cingulate gyrus and the amygdala in patients with BPD. CONCLUSION: The interaction between increased pain-induced response in the dorsolateral prefrontal cortex and deactivation in the anterior cingulate and the amygdala is associated with an antinociceptive mechanism in patients with BPD.
Limbic deactivation has been found to correlate with the degree of coping in aversive situations in general. . . . Thus, in view of these findings, self-inflicted pain may function to normalize neural activity in specific brain regions involved in emotional and cognitive processing. Alternatively, repeated self-injury could lead to an adaptation of pain thresholds and pain processing reflected in the current findings of elevated pain thresholds and disturbed prefrontal and limbic pain processing.
Omni Brain links to a new feature at Nature: a 3 month trial period of "open" peer review. For those who opt to submit their papers under this track,
authors can choose to have their submissions posted on a preprint server for open comments, in parallel with the conventional peer review process. Anyone in the field may then post comments, provided they are prepared to identify themselves. Once the usual confidential peer review process is complete, the public 'open peer review' process will be closed. Nature will report on the results after the trial period is over.In other words, The Neurocritic must be identified by name to post open comments on the web, but may maintain anonymity if the editors send me a manuscript for review. In addition, the trial
will continue in parallel with Nature's usual procedures, and does not affect the likelihood of eventual publication of the submitted work.So what do the editors and authors do with the open peer review comments??
Comments will be reviewed by staff before being published. You can be as critical or controversial as you like, but please don't get personal or offensive, and do keep it brief. Excessively long entries may be cropped. Remember this is for feedback and discussion - not for publishing papers or press releases.
We strongly encourage you to use your real, full name. Email addresses are required: this is just in case we need to discuss your comment with you privately. They won’t be published.
UPDATE: well, they did allow this post to get in (perhaps to demonstrate the benefits of the current peer review system):
I am the biggest name in the world in electromagnetic theory. All my attempts to publish on electromagnetic theory have for thirty years been rejected worldwide by the system of peer review.
My comments are at
Now back to our irregularly scheduled neuroscience programming!
. . .
And I gotta say - I’m going to go out on the limb here - I believe slavery was wrong. No, I don’t care who that upsets. I just hope the mainstream media give me the credit for the courage it took to say that today. I know the blogosphere is just going to explode tomorrow. But enough about me - if there can be enough about me.
So we must build walls. A wall obviously across the entire southern border. That’s the answer. That may not be enough -- maybe a moat in front of it, or a fire-pit. Maybe a flaming moat, filled with fire-proof crocodiles. And we should probably wall off the northern border as well. Keep those Canadians with their socialized medicine and their skunky beer out. And because immigrants can swim, we’ll probably want to wall off the coasts as well. And while we’re at it, we need to put up a dome, in case they have catapults. And we’ll punch some holes in it so we can breathe. Breathe free. It’s time for illegal immigrants to go -- right after they finish building those walls. Yes, yes, I agree with me.
There are so many challenges facing this next generation, and as they said earlier, you are up for these challenges. And I agree, except that I don't think you are. I don't know if you're tough enough to handle this. You are the most cuddled generation in history. I belong to the last generation that did not have to be in a car seat. You had to be in car seats. I did not have to wear a helmet when I rode my bike. You do. You have to wear helmets when you go swimming, right? In case you bump your head against the side of the pool. Oh, by the way, I should have said, my speech today may contain some peanut products.
My mother had 11 children: Jimmy, Eddie, Mary, Billy, Morgan, Tommy, Jay, Lou, Paul, Peter, Stephen. You may applaud my mother's womb. Thank you, I'll let her know. She could never protect us the way you all have been protected. She couldn't fit 11 car seats. She would just open the back of her Town & Country - stack us like cord wood: four this way, four that way. And she put crushed glass in the empty spaces to keep it steady. Then she would roll up all the windows in the winter time and light up a cigarette. When I die I will not need to be embalmed, because as a child my mother hickory-smoked me.
There's Mary and her father, grinning at the prospect of the "Marriage Protection Amendment" serving to distract the American public from ongoing "collateral damage" in Iraq.
The White House has been kind enough to put the text of President Bush's speech advocating the "Marriage Protection Amendment" yesterday on their webpage. It would make a perfect example of illogical argumentation for a logic course.Recommmended reading, and a depressing reminder that logic and science are not allowed by the current administration.The union of a man and woman in marriage is the most enduring and important human institution.
But apparently not so enduring that it can't withstand more people getting married.For ages, in every culture, human beings have understood that marriage is critical to the well-being of families. And because families pass along values and shape character, marriage is also critical to the health of society. Our policies should aim to strengthen families, not undermine them.
I totally agree. But why does this claim not apply to families headed by gays? And what is the causal link between gay marriage and diminishing these good things about marriage? If gays are allowed to get married, are straight couples suddenly going to stop passing along values and shaping character?
OR, Trust and Fairness in Science.
Tomlin D, Kayali MA, King-Casas B, Anen C, Camerer CF, Quartz SR, Montague PR. Agent-specific responses in the cingulate cortex during economic exchanges. Science. 2006 May 19;312(5776):1047-50.
Interactions with other responsive agents lie at the core of all social exchange. During a social exchange with a partner, one fundamental variable that must be computed correctly is who gets credit for a shared outcome; this assignment is crucial for deciding on an optimal level of cooperation that avoids simple exploitation. We carried out an iterated, two-person economic exchange and made simultaneous hemodynamic measurements from each player's brain. These joint measurements revealed agent-specific responses in the social domain ("me" and "not me") arranged in a systematic spatial pattern along the cingulate cortex. This systematic response pattern did not depend on metrical aspects of the exchange, and it disappeared completely in the absence of a responding partner.
As such, prejudice may arise in part because perceivers assume that outgroup members’ mental states do not correspond to their own and, accordingly, mentalize in a non-self-referential way about the minds of people from different groups. Without a self-referential basis for mentalizing about outgroup members, perceivers may rely heavily on precomputed judgments—such as stereotypes—to make mental state inferences about very dissimilar others. This view suggests that a critical strategy for reducing prejudice may be to breach arbitrary boundaries based on social group membership by focusing instead on the shared similarity between oneself and outgroup members.and here's the Tomlin et al. conclusion:
However, it is reasonably clear that cingulate and paracingulate cortices contribute to normal social cognition and adaptive decision-making. The results of this paper add the important possibility that many other variables in the social domain may be arranged in such a systematic fashion through the spatial domain, a phenotype that could be disturbed in afflictions where the capacity to distinguish "me" from "not me" is impaired.Uh, yeah.
One question deserves separate consideration: Did the reveal screens generate simple surprise or novelty responses along cingulate that were not related to the social element of the exchange? Although this reasonable interpretation is possible, the control experiments suggest otherwise. The response pattern along the cingulate disappeared in the control experiments where subjects received stimuli that were visually identical to those in the trust game and were composed of novel, reward-related information.However, it's very surprising(!) that novelty and reward did not activate the cingulate in these control conditions, given the number of studies that have reported otherwise.
These experiments have elicited not only brain responses in previously described theory-of-mind networks (27–29), but also have elicited formerly unreported activations along the cingulate cortex that correlate with the revelation of a social partner's decision (29). Although evoked during an economic exchange with another human, these cingulate activations did not modulate as a function of the fairness of the exchange, nor did they occur in exchanges with computer partners (28).
. . .
Given the previously reported activations in the anterior and posterior portions of the medial cingulate during a social exchange (28), a detailed analysis of the cingulate cortex in each pair of subjects was performed.
27. J Rilling, D Gutman, T Zeh, G Pagnoni, G Berns, C Kilts, Neuron 35, 395 (2002).
28. J. K. Rilling, A. G. Sanfey, J. A. Aronson, L. E. Nystrom, J. D. Cohen, Neuroimage 22, 1694 (2004).
29. A. G. Sanfey, J. K. Rilling, J. A. Aronson, L. E. Nystrom, J. D. Cohen, Science 300, 1755 (2003).
...Science, that is. The latest example of declining standards in that tabloid is (you guessed it) a new fMRI study, described as a highlight of the May 18 issue:
Who Gets the Credit?It appears that Tomlin gets the credit, despite this irony:
In working backward from outcomes to behavior or in strategic planning for future scenarios, one important issue is who gets the credit (and how much) for the eventual result. In the trust game, the first player has to decide how much money to invest, and the second player has to decide how much of the multiplied investment to give back. Tomlin et al. (p. 1047) have carried out a large-scale simultaneous brain imaging study and suggest that different regions of the cingulate cortex become active when what the "other" player has chosen to do is revealed, compared with situations when "I" have done the choosing.
Damon Tomlin,1* M. Amin Kayali,1* et al.
*These authors contributed equally to this work.
Lisa: I can't believe those idiot judges were impressed by glowing plastic tubes.--from "Saddlesore Galactica"
Homer: [wearing a garland of glow sticks] Look, Lisa! It glows. [waves one in front of his face, fascinated] Ooooh.