Σάββατο 26 Φεβρουαρίου 2011
Στον πατέρα μου οφείλω ό,τι κατάφερα στη ζωή μου.
Στον πατέρα μου οφείλω ό,τι κατάφερα στη ζωή μου. Αυτό που είμαι και - σε καθοριστικό βαθμό - αυτό που έγινα. Από πολύ νωρίς προσπάθησε να μου εμφυσήσει την πεποίθηση ότι η μόνη πραγματική περιουσία μου είναι τα βιβλία που έχω διαβάσει, η μουσική που έχω ακούσει ως ύψιστο μέσο διαισθητικής κατανόησης του κόσμου και της θέσης μου σ' αυτόν και η αγάπη που θα επιτρέψω στον εαυτό μου να δώσει αφειδώλευτα και χωρίς ανταλλάγματα στους άλλους. Ένα χαμόγελο ως απάντηση στη δική μου ή την ξένη θλίψη, μια θερμή χειραψία, μια αγκαλιά, ένα ξόρκι διάσημου προγόνου στα χείλια που θα διώξει τον φόβο της αύριον, μια γλυκιά μελαγχολία που θ' αποτελέσει τ' αναγκαίο αντιστάθμισμα στην υπερβολική χαρά μιας απρόσμενης επιτυχίας... Αυτά - και τόσα άλλα, μικρά, ανθρώπινα, που δεν τα πιάνει το μάτι, που δεν αποτιμώνται σε χρήμα ή "επιφάνεια" κοινωνική και τα τοιαύτα - υπήρξαν η μεγαλύτερη κληρονομιά, η ισχυρότερη αντίσταση, το αβύθιστο εκτόπισμα της μέχρι τώρα ζωής μου. Διότι η θειότητα - αυτό που κυριαρχεί στη στάση μας απέναντι στα πράγματα και μας εμπνέει - δεν υπάρχει στις απεικονίσεις του Θείου, στα κάθε λογής είδωλα, στα "χρυσά μοσχάρια". Υπάρχει μέσα μας. Είναι ενδιάθετη. Δεν φανερώνεται στα ποικίλα και κατά κανόνα άχρηστα αποκτήματα, αλλά στην καλλιέργεια της ικανότητας του καθενός από μας να κατανοεί και να νιώθει...
Τετάρτη 9 Φεβρουαρίου 2011
Thoughts of Hopes, Opportunities Keep People From Clinging to Failing Investments
It’s a common problem in the business world—throwing good money after bad. People cling to bad investments, hoping that more time, effort, and money will rescue their turkey of a project. A new study published in Psychological Science, a journal of the Association for Psychological Science, finds that changing people’s mindsets can make them more likely to abandon a failing investment.
“These situations happen all the time,” says Assistant Professor Daniel C. Molden, of Northwestern University, who conducted the study with his graduate student Chin Ming Hui. “They happen with businesses; they happen in the Pentagon with weapons systems.” The producers of Spider-Man: Turn off the Dark are making the most expensive musical of all time, plagued with cost overruns and cast injuries. “If they had at any point objectively reevaluated their position and thought, ‘What is the probability that this is going to make money?’ they might have just pulled the plug,” Molden says. Now the musical will have to be wildly successful to make back the estimated $65 million that went into its production.
Molden and Hui devised an experiment to find out if they could change how people dealt with the “sunk costs” from their previous investments. Volunteers were first asked to write generally about either their personal duties and obligations or their personal hopes and aspirations. Then they were asked to imagine that they were the president of an aviation company who had committed $10 million to building a special kind of airplane. But with $9 million already spent and the project nearly done, another company had announced they had made a better, cheaper plane. They were asked whether they would spend the last $1 million or cancel the project.
People who had thought about their hopes and aspirations were more likely to say they would abandon the project. On the other hand, people who had written about their duties and obligations felt it was their responsibility to finish the project—thus throwing good money after bad. Molden suggests that this is because people who focus on their own hopes are thinking positively about opportunities for growth, and are therefore more likely to appreciate what else might be accomplished with the remaining $1 million, whereas people who focus on duties and obligations are feeling anxious and thinking about how abandoning the project would be accepting complete failure.
“At the very least, when things start to go wrong, people should stop and evaluate the costs and benefits of going forward,” Molden says. Instead, it seems that people think, “I’ve already committed so much to this, I can’t quit now.”
Of course, not everything that appears to be going badly will fail. Buildings, movies, or government programs that run over cost could still be a success in the end. Spider-Man could turn out to be the best musical of all time. “Things can work out,” says Molden. “The problem is that when people decide to push ahead because of what has already been invested versus some reasonable expectations of what will happen next, more often than not, they don’t.”
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“These situations happen all the time,” says Assistant Professor Daniel C. Molden, of Northwestern University, who conducted the study with his graduate student Chin Ming Hui. “They happen with businesses; they happen in the Pentagon with weapons systems.” The producers of Spider-Man: Turn off the Dark are making the most expensive musical of all time, plagued with cost overruns and cast injuries. “If they had at any point objectively reevaluated their position and thought, ‘What is the probability that this is going to make money?’ they might have just pulled the plug,” Molden says. Now the musical will have to be wildly successful to make back the estimated $65 million that went into its production.
Molden and Hui devised an experiment to find out if they could change how people dealt with the “sunk costs” from their previous investments. Volunteers were first asked to write generally about either their personal duties and obligations or their personal hopes and aspirations. Then they were asked to imagine that they were the president of an aviation company who had committed $10 million to building a special kind of airplane. But with $9 million already spent and the project nearly done, another company had announced they had made a better, cheaper plane. They were asked whether they would spend the last $1 million or cancel the project.
People who had thought about their hopes and aspirations were more likely to say they would abandon the project. On the other hand, people who had written about their duties and obligations felt it was their responsibility to finish the project—thus throwing good money after bad. Molden suggests that this is because people who focus on their own hopes are thinking positively about opportunities for growth, and are therefore more likely to appreciate what else might be accomplished with the remaining $1 million, whereas people who focus on duties and obligations are feeling anxious and thinking about how abandoning the project would be accepting complete failure.
“At the very least, when things start to go wrong, people should stop and evaluate the costs and benefits of going forward,” Molden says. Instead, it seems that people think, “I’ve already committed so much to this, I can’t quit now.”
Of course, not everything that appears to be going badly will fail. Buildings, movies, or government programs that run over cost could still be a success in the end. Spider-Man could turn out to be the best musical of all time. “Things can work out,” says Molden. “The problem is that when people decide to push ahead because of what has already been invested versus some reasonable expectations of what will happen next, more often than not, they don’t.”
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Πέμπτη 3 Φεβρουαρίου 2011
Neurobiologists find that weak electrical fields in the brain help neurons fire together
Coordinated behavior occurs whether or not neurons are actually connected via synapses
IMAGE: Ephaptic coupling leads to coordinated spiking of nearby neurons, as measured using a 12-pipette electrophysiology setup developed in the laboratory of coauthor Henry Markram.
Click here for more information.
Pasadena, Calif.—The brain—awake and sleeping—is awash in electrical activity, and not just from the individual pings of single neurons communicating with each other. In fact, the brain is enveloped in countless overlapping electric fields, generated by the neural circuits of scores of communicating neurons. The fields were once thought to be an "epiphenomenon, a 'bug' of sorts, occurring during neural communication," says neuroscientist Costas Anastassiou, a postdoctoral scholar in biology at the California Institute of Technology (Caltech).
New work by Anastassiou and his colleagues, however, suggests that the fields do much more—and that they may, in fact, represent an additional form of neural communication.
"In other words," says Anastassiou, the lead author of a paper about the work appearing in the journal Nature Neuroscience, "while active neurons give rise to extracellular fields, the same fields feed back to the neurons and alter their behavior," even though the neurons are not physically connected—a phenomenon known as ephaptic coupling. "So far, neural communication has been thought to occur at localized machines, termed synapses. Our work suggests an additional means of neural communication through the extracellular space independent of synapses."
Extracellular electric fields exist throughout the living brain, though they are particularly strong and robustly repetitive in specific brain regions such as the hippocampus, which is involved in memory formation, and the neocortex, the area where long-term memories are held. "The perpetual fluctuations of these extracellular fields are the hallmark of the living and behaving brain in all organisms, and their absence is a strong indicator of a deeply comatose, or even dead, brain," Anastassiou explains.
Previously, neurobiologists assumed that the fields were capable of affecting—and even controlling—neural activity only during severe pathological conditions such as epileptic seizures, which induce very strong fields. Few studies, however, had actually assessed the impact of far weaker—but very common—non-epileptic fields. "The reason is simple," Anastassiou says. "It is very hard to conduct an in vivo experiment in the absence of extracellular fields," to observe what changes when the fields are not around.
To tease out those effects, Anastassiou and his colleagues, including Caltech neuroscientist Christof Koch, the Lois and Victor Troendle Professor of Cognitive and Behavioral Biology and professor of computation and neural systems, focused on strong but slowly oscillating fields, called local field potentials (LFP), that arise from neural circuits composed of just a few rat brain cells. Measuring those fields and their effects required positioning a cluster of tiny electrodes within a volume equivalent to that of a single cell body—and at distances of less than 50 millionths of a meter from one another.
"Because it had been so hard to position that many electrodes within such a small volume of brain tissue, the findings of our research are truly novel," Anastassiou says. Previously, he explains, "nobody had been able to attain this level of spatial and temporal resolution."
An "unexpected and surprising finding was how already very weak extracellular fields can alter neural activity," he says. "For example, we observed that fields as weak as one millivolt per millimeter robustly alter the firing of individual neurons, and increase the so-called "spike-field coherence"—the synchronicity with which neurons fire with relationship to the field."In the mammalian brain, we know that extracellular fields may easily exceed two to three millivolts per millimeter. Our findings suggest that under such conditions, this effect becomes significant."
What does that mean for brain computation? "Neuroscientists have long speculated about this," Anastassiou says. "Increased spike-field coherency may substantially enhance the amount of information transmitted between neurons as well as increase its reliability. Moreover, it has been long known that brain activity patterns related to memory and navigation give rise to a robust LFP and enhanced spike-field coherency. We believe ephaptic coupling does not have one major effect, but instead contributes on many levels during intense brain processing."
Can external electric fields have similar effects on the brain? "This is an interesting question," Anastassiou says. "Indeed, physics dictates that any external field will impact the neural membrane. Importantly, though, the effect of externally imposed fields will also depend on the brain state. One could think of the brain as a distributed computer—not all brain areas show the same level of activation at all times.
"Whether an externally imposed field will impact the brain also depends on which brain area is targeted. During epileptic seizures, pathological fields can be as strong as 100 millivolts per millimeter¬—such fields strongly entrain neural firing and give rise to super-synchronized states." And that, he adds, suggests that electric field activity—even from external fields—in certain brain areas, during specific brain states, may have strong cognitive and behavioral effects.
Ultimately, Anastassiou, Koch, and their colleagues would like to test whether ephaptic coupling affects human cognitive processing, and under which circumstances. "I firmly believe that understanding the origin and functionality of endogenous brain fields will lead to several revelations regarding information processing at the circuit level, which, in my opinion, is the level at which percepts and concepts arise," Anastassiou says. "This, in turn, will lead us to address how biophysics gives rise to cognition in a mechanistic manner—and that, I think, is the holy grail of neuroscience."
###
The work in the paper, "Ephaptic coupling of cortical neurons," published January 16 in the advance online edition of the journal, was supported by the Engineering Physical Sciences Research Council, the Sloan-Swartz Foundation, the Swiss National Science Foundation, EU Synapse, the National Science Foundation, the Mathers Foundation, and the National Research Foundation of Korea.
IMAGE: Ephaptic coupling leads to coordinated spiking of nearby neurons, as measured using a 12-pipette electrophysiology setup developed in the laboratory of coauthor Henry Markram.
Click here for more information.
Pasadena, Calif.—The brain—awake and sleeping—is awash in electrical activity, and not just from the individual pings of single neurons communicating with each other. In fact, the brain is enveloped in countless overlapping electric fields, generated by the neural circuits of scores of communicating neurons. The fields were once thought to be an "epiphenomenon, a 'bug' of sorts, occurring during neural communication," says neuroscientist Costas Anastassiou, a postdoctoral scholar in biology at the California Institute of Technology (Caltech).
New work by Anastassiou and his colleagues, however, suggests that the fields do much more—and that they may, in fact, represent an additional form of neural communication.
"In other words," says Anastassiou, the lead author of a paper about the work appearing in the journal Nature Neuroscience, "while active neurons give rise to extracellular fields, the same fields feed back to the neurons and alter their behavior," even though the neurons are not physically connected—a phenomenon known as ephaptic coupling. "So far, neural communication has been thought to occur at localized machines, termed synapses. Our work suggests an additional means of neural communication through the extracellular space independent of synapses."
Extracellular electric fields exist throughout the living brain, though they are particularly strong and robustly repetitive in specific brain regions such as the hippocampus, which is involved in memory formation, and the neocortex, the area where long-term memories are held. "The perpetual fluctuations of these extracellular fields are the hallmark of the living and behaving brain in all organisms, and their absence is a strong indicator of a deeply comatose, or even dead, brain," Anastassiou explains.
Previously, neurobiologists assumed that the fields were capable of affecting—and even controlling—neural activity only during severe pathological conditions such as epileptic seizures, which induce very strong fields. Few studies, however, had actually assessed the impact of far weaker—but very common—non-epileptic fields. "The reason is simple," Anastassiou says. "It is very hard to conduct an in vivo experiment in the absence of extracellular fields," to observe what changes when the fields are not around.
To tease out those effects, Anastassiou and his colleagues, including Caltech neuroscientist Christof Koch, the Lois and Victor Troendle Professor of Cognitive and Behavioral Biology and professor of computation and neural systems, focused on strong but slowly oscillating fields, called local field potentials (LFP), that arise from neural circuits composed of just a few rat brain cells. Measuring those fields and their effects required positioning a cluster of tiny electrodes within a volume equivalent to that of a single cell body—and at distances of less than 50 millionths of a meter from one another.
"Because it had been so hard to position that many electrodes within such a small volume of brain tissue, the findings of our research are truly novel," Anastassiou says. Previously, he explains, "nobody had been able to attain this level of spatial and temporal resolution."
An "unexpected and surprising finding was how already very weak extracellular fields can alter neural activity," he says. "For example, we observed that fields as weak as one millivolt per millimeter robustly alter the firing of individual neurons, and increase the so-called "spike-field coherence"—the synchronicity with which neurons fire with relationship to the field."In the mammalian brain, we know that extracellular fields may easily exceed two to three millivolts per millimeter. Our findings suggest that under such conditions, this effect becomes significant."
What does that mean for brain computation? "Neuroscientists have long speculated about this," Anastassiou says. "Increased spike-field coherency may substantially enhance the amount of information transmitted between neurons as well as increase its reliability. Moreover, it has been long known that brain activity patterns related to memory and navigation give rise to a robust LFP and enhanced spike-field coherency. We believe ephaptic coupling does not have one major effect, but instead contributes on many levels during intense brain processing."
Can external electric fields have similar effects on the brain? "This is an interesting question," Anastassiou says. "Indeed, physics dictates that any external field will impact the neural membrane. Importantly, though, the effect of externally imposed fields will also depend on the brain state. One could think of the brain as a distributed computer—not all brain areas show the same level of activation at all times.
"Whether an externally imposed field will impact the brain also depends on which brain area is targeted. During epileptic seizures, pathological fields can be as strong as 100 millivolts per millimeter¬—such fields strongly entrain neural firing and give rise to super-synchronized states." And that, he adds, suggests that electric field activity—even from external fields—in certain brain areas, during specific brain states, may have strong cognitive and behavioral effects.
Ultimately, Anastassiou, Koch, and their colleagues would like to test whether ephaptic coupling affects human cognitive processing, and under which circumstances. "I firmly believe that understanding the origin and functionality of endogenous brain fields will lead to several revelations regarding information processing at the circuit level, which, in my opinion, is the level at which percepts and concepts arise," Anastassiou says. "This, in turn, will lead us to address how biophysics gives rise to cognition in a mechanistic manner—and that, I think, is the holy grail of neuroscience."
###
The work in the paper, "Ephaptic coupling of cortical neurons," published January 16 in the advance online edition of the journal, was supported by the Engineering Physical Sciences Research Council, the Sloan-Swartz Foundation, the Swiss National Science Foundation, EU Synapse, the National Science Foundation, the Mathers Foundation, and the National Research Foundation of Korea.
Flash of fresh insight by electrical brain stimulation
Are we on the verge of being able to stimulate the brain to see the world anew - an electric thinking cap? Research by Richard Chi and Allan Snyder from the Centre for the Mind at the University of Sydney suggests that this could be the case.
They found that participants who received electrical stimulation of the anterior temporal lobes were three times as likely to reach the fresh insight necessary to solve a difficult, unfamiliar problem than those in the control group. The study published on February 2 in the open-access journal PLoS ONE.
According to the authors, our propensity to rigidly apply strategies and insights that have had previous success is a major bottleneck to making creative leaps in solving new problems. There is normally a cognitive tradeoff between the necessity of being fast at the familiar on one hand and being receptive to novelty on the other.
Chi and Snyder argue that we can modulate this tradeoff to our advantage by applying transcranial direct current stimulation (tDCS), a safe, non-invasive technique that temporarily increases or decreases excitability of populations of neurons. In particular, tDCS can be used to manipulate the competition between the left and right hemisphere by inhibiting and/or disinhibiting certain networks. Their findings are consistent with evidence that the right anterior temporal lobe is associated with insight or novel meaning and that inhibition of the left anterior temporal lobe can induce a cognitive style that is less top-down, less influenced by preconceptions.
While further studies involving brain stimulation in combination with neuroimaging are needed to elucidate the exact mechanisms leading to insight, Chi and Snyder can imagine a future when non-invasive brain stimulation is briefly employed for solving problems that have evaded traditional cognitive approaches.
###
They found that participants who received electrical stimulation of the anterior temporal lobes were three times as likely to reach the fresh insight necessary to solve a difficult, unfamiliar problem than those in the control group. The study published on February 2 in the open-access journal PLoS ONE.
According to the authors, our propensity to rigidly apply strategies and insights that have had previous success is a major bottleneck to making creative leaps in solving new problems. There is normally a cognitive tradeoff between the necessity of being fast at the familiar on one hand and being receptive to novelty on the other.
Chi and Snyder argue that we can modulate this tradeoff to our advantage by applying transcranial direct current stimulation (tDCS), a safe, non-invasive technique that temporarily increases or decreases excitability of populations of neurons. In particular, tDCS can be used to manipulate the competition between the left and right hemisphere by inhibiting and/or disinhibiting certain networks. Their findings are consistent with evidence that the right anterior temporal lobe is associated with insight or novel meaning and that inhibition of the left anterior temporal lobe can induce a cognitive style that is less top-down, less influenced by preconceptions.
While further studies involving brain stimulation in combination with neuroimaging are needed to elucidate the exact mechanisms leading to insight, Chi and Snyder can imagine a future when non-invasive brain stimulation is briefly employed for solving problems that have evaded traditional cognitive approaches.
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