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Mo
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- December 15, 2009
- 06:05 PM
- 1,053 views
Glimpsing memory traces in real time
by Mo in Neurophilosophy
MEMORY is one of the biggest enduring mysteries of modern neuroscience, and has perhaps been researchered more intensively than any other aspect of brain function. The past few decades have yielded a great deal of knowledge about the cellular and molecular mechanisms of memory, and it is now widely believed that memories are formed as a result of biochemical changes which ultimately lead to the strengthening of connections between nerve cells.
However, it is also clear that memories are not encoded at the level of single neurons. Instead, the memory trace is thought of as a flurry of electrical activity within a scattered population of cells. Yet, very little is known about how memories are encoded and retrieved by populations of cells. Using a new large-scale recording technique, researchers from the Medical College of Georgia have now directly observed, for the first time, the population-level activity associated with encoding and retrieval of memory traces.
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Chen, G., Wang, L., & Tsien, J. (2009) Neural Population-Level Memory Traces in the Mouse Hippocampus. PLoS ONE, 4(12). DOI: 10.1371/journal.pone.0008256
- November 19, 2009
- 04:10 PM
- 1,284 views
The cognitive benefits of time-space synaesthesia
by Mo in Neurophilosophy
SYNAESTHESIA is a neurological condition in which there is a merging of the senses, so that activity in one sensory modality elicits sensations in another. Although first described by Francis Galton in the 1880s, little was known about this condition until recently. A rennaissance in synaesthesia research began about a decade ago; since then, three previously unrecognized forms of the condition have been described, and a possible explanation for how it arises have been put forward.
Of all the forms of this fascinating condition, the least researched is time-space synaesthesia, but two new studies provide some insight into it. One is a case study of an individual whose time-space synaesthesia has an apparently unique characteristic. The second demonstrates that time-space synaesthetes have superior cognitive abilities than non-synaesthetes, and suggests that time-space synaesthesia may underly the savant-like abilities of people with hyperthymestic (or "super-memory") syndrome.
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Jarick, M., Dixon, M., Stewart, M., Maxwell, E., & Smilek, D. (2009) A different outlook on time: Visual and auditory month names elicit different mental vantage points for a time-space synaesthete. Cortex, 45(10), 1217-1228. DOI: 10.1016/j.cortex.2009.05.014
Simner, J., Mayo, N., & Spiller, M. (2009) A foundation for savantism? Visuo-spatial synaesthetes present with cognitive benefits. Cortex, 45(10), 1246-1260. DOI: 10.1016/j.cortex.2009.07.007
- November 13, 2009
- 11:10 AM
- 1,269 views
Dyslexia and the Cocktail Party effect
by Mo in Neurophilosophy
IMAGINE sitting in a noisy restaurant, across the table from a friend, and having a conversation with them as you eat your meal. To communicate effectively in this situation, you have to extract the relevant information from the noise in the background, as well as from other voices. To do so, your brain somehow "tags" the predictable, repeating elements of the target signal, such as the pitch of your friend's voice, and segregates them from other signals in the surroundings, which fluctuate randomly.
The ability to focus on your friend's voice while excluding other noises is commonly referred to as the cocktail party effect. Although first described more than 50 years ago, the brain mechanisms involved are unknown. But a new study by researchers at Northwestern University now shows that activity in regions of the brainstem are modulated by specific characteristics of the speaker's voice, and that this modulation is impaired in children with dyslexia.
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Chandrasekaran, B., Hornickel, J., Skoe, E., Nicol, T., & Kraus, N. (2009) Context-Dependent Encoding in the Human Auditory Brainstem Relates to Hearing Speech in Noise: Implications for Developmental Dyslexia. Neuron, 64(3), 311-319. DOI: 10.1016/j.neuron.2009.10.006
- November 6, 2009
- 12:50 PM
- 1,410 views
The illusion of time: Perceiving the effect before the cause
by Mo in Neurophilosophy
A novel temporal illusion, in which the cause of an event is perceived to occur after the event itself, provides some insight into the brain mechanisms underlying conscious perception. The illusion, described in the journal Current Biology by a team of researchers from France, suggests that the unconscious representation of a visual object is processed for around one tenth of a second before it enters conscious awareness.
Chien-Te Wu and his colleagues at the Brain and Cognition Research Centre in Toulouse used a visual phenomenon called motion-induced blindness, in which a constantly rotating background causes prominent and motionless visual stimuli to disappear and reappear. This is demonstrated in the video below. Fixate on the flashing green spot in the centre, and you'll notice that the surrounding yellow spots begin to disappear and reappear after about ten seconds. Then replay the clip and focus on any of the yellow spots; you'll see that it is a visual disappearance illusion. Exactly how it works is unclear; according to one hypothesis it is due to the properties of neurons in area V1 of the visual cortex. Read the rest of this post... | Read the comments on this post...... Read more »
Wu, C.-T., et al. (2009) The Temporal Interplay between Conscious and Unconscious Perceptual Streams. Curr. Biol. . info:/10.1016/j.cub.2009.10.017
- October 28, 2009
- 02:37 PM
- 1,331 views
Phantom limbs can contort into impossible configurations
by Mo in Neurophilosophy
FOLLOWING the surgical removal of a body part, amputees often report sensations which seem to originate from the missing limb. This is thought to occur because the brain's model of the body (referred to as the body image) still contains a representation of the limb, and this leads to the experience that their missing limb is still attached to their body. Occasionally, amputees say that they cannot move their phantom limbs. They are perceived to be frozen in space, apparently because they cannot be seen.
Yet, research shows that the body image is malleable and easily manipulated. And according to new research published in the Proceedings of the National Academy of Sciences, so too are phantom limbs. The study shows that some amputees can make their phantom limbs defy the anatomical constraints of the physical body, using visual imagery to make them perform movements which could not possibly be performed by a real physical limb.
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Moseley, G., & Brugger, P. (2009) Interdependence of movement and anatomy persists when amputees learn a physiologically impossible movement of their phantom limb. Proc. Nat. Acad. Sci. DOI: 10.1073/pnas.0907151106
- October 20, 2009
- 12:55 PM
- 1,156 views
Lasers used to write false memories onto the fruit fly brain
by Mo in Neurophilosophy
THE humble fruit fly (Drosophila melanogaster) has the ability to learn and remember, and to make predictions about the outcome of its behaviours on the basis of past experience. Compared to a human brain, that of the fruit fly is relatively simple, containing approximately 250,000 cells. Even so, little is known about the anatomical basis of memory formation. The neural circuitry underlying memories in these insects has now been dissected. In an elegant new study published in the journal Cell, researchers from the University of Oxford show that aversive memories are dependent on a tiny cluster of neurons, and also demonstrate that such memories can be implanted in the fruit fly's brain by using light to manipulate the cells' activity. Read the rest of this post... | Read the comments on this post...... Read more »
Claridge-Chang, A., Roorda, R., Vrontou, E., Sjulson, L., Li, H., Hirsh, J., & Miesenböck, G. (2009) Writing Memories with Light-Addressable Reinforcement Circuitry. Cell, 139(2), 405-415. DOI: 10.1016/j.cell.2009.08.034
- October 18, 2009
- 07:43 PM
- 1,281 views
Mice navigate a virtual reality environment
by Mo in Neurophilosophy
USING an inventive new method in which mice run through a virtual reality environment based on teh video game Quake, researchers from Princeton University have made the first direct measurements of the cellular activity associated with spatial navigation. The method will allow for investigations of the neural circuitry underlying navigation, and to a better understanding of how spatial information is encoded at the cellular level.
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Harvey, C., Collman, F., Dombeck, D., & Tank, D. (2009) Intracellular dynamics of hippocampal place cells during virtual navigation. Nature, 461(7266), 941-946. DOI: 10.1038/nature08499
- October 16, 2009
- 04:50 PM
- 1,229 views
Surgery on conscious patients reveals sequence and timing of language processing
by Mo in Neurophilosophy
THINKING of and saying a word is something that most of us do effortlessly many times a day. This involves a number of steps - we must select the appropriate word, decide on the proper tense, and also pronounce it correctly. The neural computations underlying these tasks are highly complex, and whether the brain performs them all at the same time, or one after the other, has been a subject of debate.
This debate has now apparently been settled, by a team of American researchers who had the rare opportunity to investigate language processing in conscious epileptic patients undergoing surgery. In today's issue of the journal Science, the researchers report that the brain processes lexical, grammatical and phonological information in a well defined sequence that lasts less than half a second, and that a single language centre known as Broca's Area is involved in all these tasks.
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Sahin, N., Pinker, S., Cash, S., Schomer, D., & Halgren, E. (2009) Sequential Processing of Lexical, Grammatical, and Phonological Information Within Broca's Area. Science, 326(5951), 445-449. DOI: 10.1126/science.1174481
- October 12, 2009
- 02:50 PM
- 1,699 views
Kicking performance affects perception of goal size
by Mo in Neurophilosophy
ATHLETES who are on a winning streak often claim that they perceive their targets to be bigger than they actually are. After a run of birdies, for examples, golfers sometimes say that the cup appeared to be the size of a bucket, and baseball players who have a hit a few home runs say that the ball is the size of a grapefruit. Conversely, targets are often reported to be smaller than they actually are by athletes who are performing badly.
Research carried out in the past 5 years suggests that these are more than just anecdotes, and that performance in sports can actually affect perception. A new study by psychologists at Purdue University now lends more weight to this, by providing evidence that success rate in American football field goals affects how the size of the goal posts is perceived.
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Witt, J., & Dorsch, T. (2009) Kicking to bigger uprights: Field goal kicking performance influences perceived size. Perception, 38(9), 1328-1340. DOI: 10.1068/p6325
- October 8, 2009
- 05:00 PM
- 1,331 views
The virtual body illusion and immersive Second Life avatars
by Mo in Neurophilosophy
SECOND LIFE is an online "virtual world" which enables users to create a customised avatar, or digital persona, with which they interact with each other. Since its launch just over 6 years ago, it has become incredibly popular, with millions of "residents" now using it regularly to meet others, interact with them, and even to have sex. Users have also established virtual universities, businesses and a virtual economy.
Now, imagine a futuristic version of Second Life, in which avatars can transfer sensations to the bodies of their users. Such a scenario may seem far-fetched, but a team of European researchers has now taken us one step closer it. They demonstrate a perceptual illusion in which a computer-generated virtual body can be made to feel like one's real body, so that one can feel sensations from it and respond to it as if it were real.
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Slater, M. et al. (2009) Inducing illusory ownership of a virtual body . Front. Neurosci. info:/
- October 7, 2009
- 01:20 PM
- 1,441 views
Visual analgesia: Seeing the body reduces pain
by Mo in Neurophilosophy
VISION is now well known to modulate the senses of touch and pain. For example, various studies have shown that looking at oneself being touched has the opposite effect - it can enhance tactile acuity, so that one can discriminate between two pinpoints which would otherwise feel like a single sensation. And last year, researchers from the University of Oxford showed that making a limb look larger or smaller than it actually using binoculars can respectively enhance and diminish painful sensations.
These phenomena occur because the brain fuses stimuli from different sensory systems to generate a coherent experience of bodily sensations. The precise mechanisms are unknown, and it is also unclear whether these effects depend upon specific visual stimuli. But according to a new study from University College London, the general "context" of vison is enough to modulate pain. In the current issue of the Journal of Neuroscience, they report that merely looking at one's hand can affect the perception of laser-induced pain, and how it is processed in the cerebral cortex. Together with earlier work, these findings point to a simple method for managing acute pain.
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Longo, M., Betti, V., Aglioti, S., & Haggard, P. (2009) Visually Induced Analgesia: Seeing the Body Reduces Pain. Journal of Neuroscience, 29(39), 12125-12130. DOI: 10.1523/JNEUROSCI.3072-09.2009
- October 2, 2009
- 11:15 AM
- 1,996 views
Circadian and social cues regulate sodium channel trafficking in electric fish
by Mo in Neurophilosophy
SEVERAL hundred species of fish have evolved the ability to generate electric fields, which they use to navigate, communicate and home in on prey. But this ability comes at a cost - the electric field is generated continuously throughout life, so consumes a great deal of energy, and it can also attract predators which are sensitive to it. Electrogenic fish species therefore utilize various strategies to save energy and to minimize the likelihood of being detected. Some generate irregular pulses of electrical discharges whose rate can be modulated; others can also modulate the strength of the electric field.
A beautiful study published in the open access journal PLoS Biology now reveals the cellular and molecular mechanisms underlying one of these behavioural adaptations. It shows that in one species of electric fish, circadian cues and social encounters regulate the movements of proteins called voltage-gated sodium channels - which are crucial for generating the electric field - in cells of the electric organ. At night, low light levels and social interactions drive the insertion of sodium channels into the cell membranes, leading to a dramatic increase in the strength of the electric field.
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Markham, M., McAnelly, M., Stoddard, P., & Zakon, H. (2009) Circadian and Social Cues Regulate Ion Channel Trafficking. PLoS Biology, 7(9). DOI: 10.1371/journal.pbio.1000203
- September 23, 2009
- 04:55 PM
- 1,245 views
Flight of the remote-controlled cyborg beetle
by Mo in Neurophilosophy
REMOTE-CONTROLLED insects may sound like the stuff of science fiction, but they have already been under development for some time now. In 2006, for example, the Defense Advanced Research Projects Agency (DARPA, the Pentagon's research and development branch) launched the Hybrid Insect Micro-Electro-Mechanical Systems project, whose ultimate aim is turn insects into unmanned aerial vehicles.Such projects provide proof of principle, but have met with limited success. Until now, that is. In the open access journal Frontiers in Integrative Neuroscience, a team of electrical engineers led by Hirotaka Sato of the University of California, Berkeley, report the development of an implantable radio-controlled neural stimulating device, with which they demonstrate, for the very first time, the accurate control of flight in freely flying insects.
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Sato, H., et al. (2009) Remote Radio Control of Insect Flight. Front. Integr. Neurosci. , 3(24). info:/
- September 21, 2009
- 02:20 PM
- 1,306 views
Vegetative and minimally conscious patients can learn
by Mo in Neurophilosophy
THE vegetative and minimally conscious states are examples of what are referred to as disorders of consciousness. Patients in these conditions are more or less oblivious to goings-on in their surroundings - they exhibit few, if any, signs of conscious awareness, and are usually unable to communicate in any way. It is, therefore, extremely difficult to establish what these patients are experiencing, and the consciousness disorders are among the least understood, and most commonly diagnosed, conditions in medicine.
Recently though, technologies such as functional neuorimaging have enabled clinicians to gain some insight into the minimally consious and vegetative states. Nevertheless, proper assessment and diagnosis of patients are still major challenges, and there are big ethical questions regarding how they should be treated. However, researchers from the University of Cambridge have made what could be a significant advance.
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Bekinschtein, T., Shalom, D., Forcato, C., Herrera, M., Coleman, M., Manes, F., & Sigman, M. (2009) Classical conditioning in the vegetative and minimally conscious state. Nature Neuroscience. DOI: 10.1038/nn.2391
- September 19, 2009
- 11:50 AM
- 1,244 views
The social thermometer: Temperature affects how we perceive relationships
by Mo in Neurophilosophy
LANGUAGE contains many sayings which link our feelings and behaviour towards others to temperature. We might, for example, hold "warm feelings" for somebody, and extend them a "warm welcome", while giving somebody else "the cold shoulder" or "an icy stare". Why is that we have so many metaphors which relate temperature to social distance? According to the cognitive scientist George Lakoff, we judge others on the basis of warmth because abstract concepts, such as affection, are firmly grounded in bodily sensations.
There is evidence for Lakoff's hypothesis, which shows that these sayings are more than just metaphors. Last year, a by psychologists from the University of Toronto showed that participants who recalled an experience in which they felt socially excluded gave lower estimates of room temperature than participants who recalled a social inclusion experience. Hans IJzerman and Gün R. Semin of Utrecht University now show that the opposite is also true. In a paper published in Psychological Science, they report that temperature affects the perception of social relations and the language used to describe them.
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Ijzerman H. , & Semin G.R. (2009) The Thermometer of Social Relations: Mapping Social Proximity on Temperature. Psychological science. PMID: 19732385
- September 17, 2009
- 04:54 PM
- 1,528 views
A dual-use fluorescent calcium sensor virus
by Mo in Neurophilosophy
A paper by researchers from Princeton University, just published in the open access journal PLoS One, describes a new virus-based technique for probing the connections between neurons while simultaneously monitoring their activity in live animals. Various methods are available for studying the activity of neurons and how they are connected to one another, but examining the co-ordinated activity of multiple nerve cells in neural circuits has, until now, posed a big challenge, because none of them can monitor both activity and connectivity at the same time. Read the rest of this post... | Read the comments on this post...... Read more »
Granstedt, A., Szpara, M., Kuhn, B., Wang, S., & Enquist, L. (2009) Fluorescence-Based Monitoring of In Vivo Neural Activity Using a Circuit-Tracing Pseudorabies Virus. PLoS ONE, 4(9). DOI: 10.1371/journal.pone.0006923
- September 14, 2009
- 10:05 AM
- 1,440 views
Eye movements reveal unconscious memory retrieval
by Mo in Neurophilosophy
THIS short film clip shows two images of the same scene. Watch it carefully, and see if you can spot the subtle difference between the two. As you watch, your eyes will dart back and forth across the images, so that you can perceive the most important features. And even though you might not be consciously aware of the differences, your brain will have picked up on them. This implicit form of remembering is referred to as relational memory; in this case, the brain is encoding the perceptual associations between items in the image. And recent studies have shown that relational memory retrieval is evident in eye movements - even if you did not explicitly detect the change in the second image, you will, without knowing it, have spent more time looking at the changed area than at others.
However, it was unclear whether relational memory retrieval involved the same neural substrates as retrieval of other, more familiar types of memory, such as your recollection of what you had for breakfast this morning, or what you did last weekend. This latter form of memory (known as declarative memory) is well known to involve the hippocampus, a brain structure buried deep with the brain, in the medial temporal lobe. Now researchers from the University of California, Davis, report that unconscious retrieval of relational memory also involves the hippocampus, and that activity in this part of th ebrain can predict the eye movements associated with expression of this type of memory.
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Hannula, D.E. . (2009) The Eyes Have It: Hippocampal Activity Predicts Expression of Memory in Eye Movements. Neuron, 1-8. info:/
- August 27, 2009
- 10:12 PM
- 1,467 views
Nature's fibre optics
by Mo in Neurophilosophy
THE retina has an inverted structure which seems ill-suited to its function: the rod and cone cells, which are sensitive to light, and which convert light energy into electrical impulses, point backwards and are located at the back of the retina, so that light entering the eye has to pass through several layers of irregularly organized cells before it reaches them. The retina also contains nerve fibres which are positioned perpendicular to the path of light entering the eye, and many of the structures in the upper cell layers have a diameter similar to that of the wavelength of visible light. One would therefore think that light entering the eye would be subjected to a significant amount of reflection and scattering. Yet, nature somehow contrived to overcome this awkward architecture, and the retina performs its function perfectly.
As well as the various types of neurons, the retina contains specialized glial cells called Müller cells, which are arranged in parallel to each other and are oriented in the direction along which light travels through the eye. Müller cells are about 150μm (micrometres, thousandths of a millimetre) in length, and span the entire thickness of the retina, projecting from the vitreous humour (the viscous fluid in the back of the eye) to the back of the retina where light enters the rods and cones. Like other glial cells, Müller cells have been largely ignored until recently: they were thought to do little more than support and nourish retinal neurons. But in recent years it has been determined that glial cells perform other important functions, and Müller cells may overcome the retina's architectural problem, by functioning as optical fibres which transmit light through it. Read the rest of this post... | Read the comments on this post...... Read more »
Franze, K., Grosche, J., Skatchkov, S., Schinkinger, S., Foja, C., Schild, D., Uckermann, O., Travis, K., Reichenbach, A., & Guck, J. (2007) Muller cells are living optical fibers in the vertebrate retina. Proceedings of the National Academy of Sciences, 104(20), 8287-8292. DOI: 10.1073/pnas.0611180104
- August 26, 2009
- 06:20 PM
- 1,253 views
The star-nosed mole's amazing appendages
by Mo in Neurophilosophy
THIS weird and wonderful creature is the star-nosed mole (Condylura cristata), a small, semi-aquatic mammal which inhabits the low wetlands of eastern North America. Like other moles, it eeks out an existence in a network of narrow underground tunnels, and digs shallow surface tunnels where it forages for insects, worms and molluscs.Living as it does in almost complete darkness, the star-nosed mole has poorly developed eyes, and is virtually blind. Instead, it relies heavily on its remarkable star-shaped nose. This organ enables the star-nosed mole to decide whether something is edible with astonishing speed - in fact, it recently entered the Guinness Book of Records as the world's fastest forager - and also to smell out food underwater. Read the rest of this post... | Read the comments on this post...... Read more »
Catania, K. (2006) Olfaction: Underwater 'sniffing' by semi-aquatic mammals. Nature, 444(7122), 1024-1025. DOI: 10.1038/4441024a
Catania, K., & Remple, F. (2005) Asymptotic prey profitability drives star-nosed moles to the foraging speed limit. Nature, 433(7025), 519-522. DOI: 10.1038/nature03250
- August 6, 2009
- 04:58 PM
- 1,423 views
Those clever corvids
by Mo in Neurophilosophy
NOT so long ago, the idea that birds might possess some form of what we call intelligence seemed quite ridiculous.Yet in recent years, this view has changed dramatically, with numerous studies showing that some bird species are capable of complex cognition. Members of one family of birds in particular - the Corvidae, which includes crows, rooks and ravens - have an ability to make and use tools which is at least as sophisticated as that of chimpanzees.
Two new studies, published this week, provide yet more demonstrations of the remarkable cognitive abilities of this group of birds. One shows that Caledonian crows can use up to three tools in sequence to obtain food, the other that rooks can use stones to raise the level of water in a vessel in order to bring a floating worm into reach.
Watch videos of the birds performing these tasks below.
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Wimpenny, J., Weir, A., Clayton, L., Rutz, C., & Kacelnik, A. (2009) Cognitive Processes Associated with Sequential Tool Use in New Caledonian Crows. PLoS ONE, 4(8). DOI: 10.1371/journal.pone.0006471
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