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Brain ‘entanglement’ could explain memories
THIS WEEK
SUBATOMIC particles do it. Now the observation that groups of brain cells seem to have their own version of quantum entanglement, or “spooky action at a distance”, could help explain how our minds combine experiences from many different senses into one memory. Previous experiments have shown that the electrical activity of neurons in separate parts of the brain can oscillate simultaneously at the same frequency – a process known as phase locking. The frequency seems to be a signature that marks out neurons working on the same task, allowing them to identify each other. Dietmar Plenz and Tara Thiagarajan at the National Institute of Mental Health in Bethesda, Maryland, wondered whether more complicated signatures also link groups of
Megacrystals formed by dry to wet cycle WHY are these crystals so huge? The answer is ancient climate swings. Gypsum crystals up to 11 metres long were found a decade ago in caves next to the Naica mine near Chihuahua, Mexico. Over the past 200,000 years the regional climate has swung from wet to dry, suggests water trapped in the crystal. Ground level evaporation during the dry period concentrated calcium in salty surface water flowing into the caves. The evaporation repeated as the climate switched back and forth, providing enough calcium to build such big crystals, say Paolo Garofalo of the University of Bologna, Italy, and colleagues (Earth and Planetary Science Letters, vol 289, p 560). ■
10 | NewScientist | 16 January 2010
neurons. To investigate, they analysed neuronal activity using arrays of electrodes implanted in the brains of two awake macaque monkeys and embedded in dish-grown neuron cultures. In both cases, the researchers noticed that the voltage of the electrical signal in groups of neurons separated by up to 10 millimetres sometimes rose and fell with exactly the same rhythm. These patterns of activity, dubbed “coherence potentials”, often started in one set of neurons, only to be mimicked or “cloned” by others milliseconds later. They were also much more complicated than the simple phase-locked oscillations and always matched each other in amplitude as well as in frequency (PLoS Biology, DOI: 10.1371/ journal.pbio.1000278). “The precision with which these new sites pick up on the
activity of the initiating group is quite astounding – they are perfect clones,” says Plenz. Importantly, cloned signals only appeared after one region had reached a threshold level of activity. Plenz likens this to the “tipping point” in human societies when a trend becomes adopted by large numbers of people. This threshold might ensure that our attention is only captured by significant stimuli rather than by every single signal. Since the coherence potentials seemed unique, each one could represent a different memory Plenz suggests. Their purpose may be to trigger activity in the various parts of the brain that store aspects of the same experience. So a smell or taste, say, might trigger a coherence potential that then activates the same potential in neurons in the visual part of the brain. Karl Friston at University College London calls the discovery “a missing piece of the jigsaw puzzle” in terms of brain message transmission. David Robson ■
Planet 2.0 spawned by paired stars
CARSTEN PETER/SPELEORESEARCH &FILMS/NGS
Brain ‘entanglement’ could explain memories
WE THINK of stars as having just one shot at forging planets – a narrow window when the infant stars are surrounded by a disc of dust and gas. Now it seems paired stars may regularly spawn two or even three generations of planets. The mechanism for this, proposed by Hagai Perets at the HarvardSmithsonian Center for Astrophysics in Cambridge, Massachusetts, is simple, if somewhat macabre. A first clutch of planets would form as normal from a disc around one or both of the young stars. When one of the stars dies, it sheds material that then forms a disc around its surviving partner, providing the building blocks for a second generation of planets. Such discs have already been observed. A third generation may even rise from the ashes shed during the death of the second star. Doublestar systems offer “a whole different regime for where to look for planets”, says Perets (arxiv.org/1001.0581v1). Finding such systems may not be too difficult. Planets that are observed orbiting closer or further away from a star than expected for a single star system may be second generation, mainly because double stars drift apart or draw closer together as they lose mass. Perets has identified several candidates. As well as this, multiple litters may be spotted orbiting in two different planes, or rotating in different directions within the same plane. Second-generation planets might also be identified if they are unusually massive: some secondgeneration planets form when material from the dying star flows onto existing planets, potentially causing them to become hefty objects called brown dwarfs. The process could be bad news for existing planets. The addition of gas and dust could impart enough friction to knock them out of orbit, and perhaps even right out of the system, says Perets. Maggie McKee ■
SUBATOMIC particles do it. Now the observation that groups of brain cells seem to have their own version of quantum entanglement, or “spooky action at a distance”, could help explain how our minds combine experiences from many different senses into one memory. Previous experiments have shown that the electrical activity of neurons in separate parts of the brain can oscillate simultaneously at the same frequency – a process known as phase locking. The frequency seems to be a signature that marks out neurons working on the same task, allowing them to identify each other. Dietmar Plenz and Tara Thiagarajan at the National Institute of Mental Health in Bethesda, Maryland, wondered whether more complicated signatures also link groups of
Megacrystals formed by dry to wet cycle WHY are these crystals so huge? The answer is ancient climate swings. Gypsum crystals up to 11 metres long were found a decade ago in caves next to the Naica mine near Chihuahua, Mexico. Over the past 200,000 years the regional climate has swung from wet to dry, suggests water trapped in the crystal. Ground level evaporation during the dry period concentrated calcium in salty surface water flowing into the caves. The evaporation repeated as the climate switched back and forth, providing enough calcium to build such big crystals, say Paolo Garofalo of the University of Bologna, Italy, and colleagues (Earth and Planetary Science Letters, vol 289, p 560). ■
10 | NewScientist | 16 January 2010
neurons. To investigate, they analysed neuronal activity using arrays of electrodes implanted in the brains of two awake macaque monkeys and embedded in dish-grown neuron cultures. In both cases, the researchers noticed that the voltage of the electrical signal in groups of neurons separated by up to 10 millimetres sometimes rose and fell with exactly the same rhythm. These patterns of activity, dubbed “coherence potentials”, often started in one set of neurons, only to be mimicked or “cloned” by others milliseconds later. They were also much more complicated than the simple phase-locked oscillations and always matched each other in amplitude as well as in frequency (PLoS Biology, DOI: 10.1371/ journal.pbio.1000278). “The precision with which these new sites pick up on the
activity of the initiating group is quite astounding – they are perfect clones,” says Plenz. Importantly, cloned signals only appeared after one region had reached a threshold level of activity. Plenz likens this to the “tipping point” in human societies when a trend becomes adopted by large numbers of people. This threshold might ensure that our attention is only captured by significant stimuli rather than by every single signal. Since the coherence potentials seemed unique, each one could represent a different memory Plenz suggests. Their purpose may be to trigger activity in the various parts of the brain that store aspects of the same experience. So a smell or taste, say, might trigger a coherence potential that then activates the same potential in neurons in the visual part of the brain. Karl Friston at University College London calls the discovery “a missing piece of the jigsaw puzzle” in terms of brain message transmission. David Robson ■
Planet 2.0 spawned by paired stars
CARSTEN PETER/SPELEORESEARCH &FILMS/NGS
Brain ‘entanglement’ could explain memories
WE THINK of stars as having just one shot at forging planets – a narrow window when the infant stars are surrounded by a disc of dust and gas. Now it seems paired stars may regularly spawn two or even three generations of planets. The mechanism for this, proposed by Hagai Perets at the HarvardSmithsonian Center for Astrophysics in Cambridge, Massachusetts, is simple, if somewhat macabre. A first clutch of planets would form as normal from a disc around one or both of the young stars. When one of the stars dies, it sheds material that then forms a disc around its surviving partner, providing the building blocks for a second generation of planets. Such discs have already been observed. A third generation may even rise from the ashes shed during the death of the second star. Doublestar systems offer “a whole different regime for where to look for planets”, says Perets (arxiv.org/1001.0581v1). Finding such systems may not be too difficult. Planets that are observed orbiting closer or further away from a star than expected for a single star system may be second generation, mainly because double stars drift apart or draw closer together as they lose mass. Perets has identified several candidates. As well as this, multiple litters may be spotted orbiting in two different planes, or rotating in different directions within the same plane. Second-generation planets might also be identified if they are unusually massive: some secondgeneration planets form when material from the dying star flows onto existing planets, potentially causing them to become hefty objects called brown dwarfs. The process could be bad news for existing planets. The addition of gas and dust could impart enough friction to knock them out of orbit, and perhaps even right out of the system, says Perets. Maggie McKee ■