- August 26, 2009
- 12:00 PM
- 1,043 views
From the Research Summaries Archives: Care in Second Stage
by Amy Romano in Science & Sensibility
Lamaze International’s popular series, Research Summaries for Normal Birth, was discontinued in 2008 after four years of quarterly round-ups so that we could move to the blog format and launch Science & Sensibility. In order to bring all of our research resources together in one place, we are adding the Research Summaries archive to Science [...]... Read more »
Reichman O, Gdansky E, Latinsky B, Labi S, & Samueloff A. (2008) Digital rotation from occipito-posterior to occipito-anterior decreases the need for cesarean section. European journal of obstetrics, gynecology, and reproductive biology, 136(1), 25-8. PMID: 17368909
Bloom SL, Casey BM, Schaffer JI, McIntire DD, & Leveno KJ. (2006) A randomized trial of coached versus uncoached maternal pushing during the second stage of labor. American journal of obstetrics and gynecology, 194(1), 10-3. PMID: 16389004
Roberts CL, Algert CS, Cameron CA, & Torvaldsen S. (2005) A meta-analysis of upright positions in the second stage to reduce instrumental deliveries in women with epidural analgesia. Acta obstetricia et gynecologica Scandinavica, 84(8), 794-8. PMID: 16026407
Simpson KR, & James DC. (2005) Effects of immediate versus delayed pushing during second-stage labor on fetal well-being: a randomized clinical trial. Nursing research, 54(3), 149-57. PMID: 15897790
- August 26, 2009
- 11:34 AM
- 1,499 views
Polycomb group proteins in Drosophila
by Manasi in Wissenschaft
In the earlier post titled ' Role of polycomb and trithorax in developmental regulation' we have seen that the main function of the polycomb group proteins (PcGs) is to repress target gene expression, their major targets being the homeobox (Hox) genes. These proteins bind to Polycomb Response Elements (PREs), their target sequences on the DNA. The recruitment of the PcGs to these sites occurs due to covalent histone modifications in the DNA. Here we look into this aspect in some detail. Till date three distinct PcG complexes have been discovered in Drosophila Polycomb repressor complex 1 and 2 (PRC1 and 2) and Pho repressive complex (Pho RC). All three contain multiple subunits encoded by PcG genes that are crucial for Hox gene silencing. PRC2 is known to have histone methyl transferase activity. It has H3K27 methylase activity. The PRC1 subunit inhibits nucleosome remodelling and transcription and brings about chromatin compaction. The PRC1 and 2 have various catalytic and non catalytic subunits which play a role in silencing target sites. The Pho repressive complex contains Pho and dSfmbt. Pho subunit has a distinct sequence specific DNA binding activity which is essential for targeting. dSfmbt binds to H3 or H4 tail peptides which are mono or di methylated at H3K9 or H4K20 which is crucial for repression. The above figure depicts a speculative model for long range interactions between the PRE tethered PcG complexes and the methylated nucleosomes in the flanking chromatin. PRC1, PRC2 and PhoRC are locally bound to the PREs whereas trimethylation at H3K27, H3K9 and H4K20 is observed over an extended domain emcompassing the promoter and the coding regions. Left : In case of PRC1 the Pc chromadomain (red triangle) would dock onto the nucleosomes that are tri methylated at H3K27 and through such bridging interactions will bring them in proximity to the other PRE bound PcG proteins. This may permit the other PRC1 subunits to block remodelling of the target nucleosomes or facilitate methylation of the neighbouring hypomethylated (pink) nucleosomes by PRC2. Right : In case of PhoRC, the MBT (Malignant Brain Repeats) of dSfmbt (pink triangle) would interact with mono or dimethylated nucleosomes at H3K9 or H4K20.This bridging interaction would permit PRC2 to efficiently tri methylate H3K27 in hypomethylated nucleosomes. Its is also possible that as yet unindentified HMTases which tri methylate these histones are also localized at the PREs.Similarly proteins with specificity for binding to other mrthyl-lysine modifications in histones might also be localized to the PREs.Various proteins have been purified which are associated to PcG complexes that are strictly essential for silencing. Pcl (Polycomb like) has been shown to be associated with PRC2 and mutations in this protein affect PRC2 functioning. Another protein zeste is a component of PRC1 and it has DNA binding activity. As described above biochemical purification of PRC1, PRC2 and PhoRC suggests that these three complexes are separate entities. However since they co localize at the PREs various studies are aimed at finding out the physical interactions between subunits from the different complexes which may explain how PRC1 and PRC2 are localized to the PREs. Different models have been put forward based on various studies. In particular Wang et al (2004), reported that E(z) and Esc (subunits of PRC2) directly interact with Pho, leading to the proposal that Pho directly tethers PRC2 to the PREs. the PRE tethered PRC2 then locally trimethylates H3K27 thereby creating binding sites for the chromodomain of the PRC1 subinut Pc. More recent studies however challenge this model. First quantitative ChIp studies by two different labs suggest that PREs at the Ubx gene are infact devoid of nucleosomes.(V Pirrotta). Moreover PREs constitue of hypersensitive sites providing additional evidence that PRE DNA is not packaged into nucleosomes. Second studies by Mohd Sarip et al (2002), suggested that Pho can directly interact with PRC1 subunits, and that in in vitro studies Pho and PRC1 can co assemble on a naked PRE DNA template in absence of nucleosomes. This assembly assumes a conformation that is difficult to reconcile with the conformation of a nucleosome core particle. Thus available evidence suggests that not only PhoRC, but also PRC1 and PRC2 localize onto the PRE through interactions with Pho and other DNA binding proteins and not through covalent histone modifications or interactions with nucleosomes. This conclusion then raises a major question with regards to the role of histone modification (trimethylation) in PcG silencing. Quantitative ChIp analysis that compared the Ubx gene in its off and on states in Drosophila larvae suggest that trimethylation in the promoter and coding region is essential for PcG silencing. In the 'off' state extensive trimethylation is present throughout the upstream control, promoter and coding regions but in the 'on' state this methylation is restricted only to the upstream control region and not seen in the promoter and coding regions.This led to the proposal that trimethylation at H3K9, H3K27 and H4K20 in the promoter and coding regions is required to demarcate the chromatin interval that is targeted for repression by the PRE-tethered PcG protein complexes. In this context, an important aspect about the relationship between the PREs and histone modifications of the target genes comes from studies with PRE reporter genes in Drososphila, in which the PRE DNA was flanked with FRT ( Flip Recombinase Target) sites and could thus be deleted from the reporter gene. This study indicated that excision of the PRE DNA from the silenced reporter gene, caused loss of PcG silencing, even when the excision was done late in development. Thus although the PcG proteins appear to repress transcription by methylation in promoter and coding regions, silencing depends on the continuous presence of the PREs and the PcGs tethered to them. Although much progress has been made towards understanding the mechanism of PcG silencing, much remains to be learned. It is still not understood how the PcG proteins are targeted to the PREs beacuse Pho binding sites alone do not make a PRE. ChIp studies may also help elucidate additi... Read more »
MULLER, J., & KASSIS, J. (2006) Polycomb response elements and targeting of Polycomb group proteins in Drosophila. Current Opinion in Genetics , 16(5), 476-484. DOI: 10.1016/j.gde.2006.08.005
- August 26, 2009
- 10:41 AM
- 1,332 views
The ring of life
by Pablo Astudillo in astu's science blog
I was really surprised, due to my lack of knowledge in too many areas of life sciences, that our history, the history of all species, from bacterias to humans, it is not like a tree. Usually we think about evolution as a tree, where some species have developed and give rise to a new, improved [...]... Read more »
Lake JA. (2009) Evidence for an early prokaryotic endosymbiosis. Nature, 460(7258), 967-71. PMID: 19693078
Rivera MC, & Lake JA. (2004) The ring of life provides evidence for a genome fusion origin of eukaryotes. Nature, 431(7005), 152-5. PMID: 15356622
- August 26, 2009
- 08:00 AM
- 743 views
Swine Flu and Glutathione Supplements #flu
by sciencebase in Sciencebase Science Blog
Could a simple dietary change that increases glutathione, or indeed supplementation with this antioxidant tripeptide be all you need to boost your immune system and ward of influenza? Several Sciencebase correspondents and hundreds of “bloggers” selling supplements seem to think so…I’m not so sure.
The results of a small trial published in 1997 suggested that “administration [...]Swine Flu and Glutathione Supplements #flu is a post from: Sciencebase Science Blog
... Read more »
FRIEL, H., & LEDERMAN, H. (2006) A nutritional supplement formula for influenza A (H5N1) infection in humans☆. Medical Hypotheses, 67(3), 578-587. DOI: 10.1016/j.mehy.2006.02.040
- August 26, 2009
- 08:00 AM
- 901 views
How Young is Too Young to Diagnose Depression?
by Shaheen Lakhan in Brain Blogger
Any parent can attest that the “Terrible 2’s” are a moody, temperamental time in the life of a toddler. Many kids are irritable and seem to throw temper tantrums for no reason, and some engage in more destructive behaviors like biting, hitting, and kicking themselves or others. Unfortunately, for some children, this phase lasts well [...]... Read more »
Copeland, W., Shanahan, L., Costello, E., & Angold, A. (2009) Childhood and Adolescent Psychiatric Disorders as Predictors of Young Adult Disorders. Archives of General Psychiatry, 66(7), 764-772. DOI: 10.1001/archgenpsychiatry.2009.85
Luby, J., Belden, A., Sullivan, J., Hayen, R., McCadney, A., & Spitznagel, E. (2009) Shame and guilt in preschool depression: evidence for elevations in self-conscious emotions in depression as early as age 3. Journal of Child Psychology and Psychiatry. DOI: 10.1111/j.1469-7610.2009.02077.x
LUBY, J., BELDEN, A., PAUTSCH, J., SI, X., & SPITZNAGEL, E. (2009) The clinical significance of preschool depression: Impairment in functioning and clinical markers of the disorder. Journal of Affective Disorders, 112(1-3), 111-119. DOI: 10.1016/j.jad.2008.03.026
Luby, J., Si, X., Belden, A., Tandon, M., & Spitznagel, E. (2009) Preschool Depression: Homotypic Continuity and Course Over 24 Months. Archives of General Psychiatry, 66(8), 897-905. DOI: 10.1001/archgenpsychiatry.2009.97
- August 26, 2009
- 07:14 AM
- 1,227 views
“Two years from breast cancer cure” – what’s the real story?
by Cancer Research UK in Cancer Research UK - Science Update
There were dramatic headlines in the papers this week claiming a “Breast cancer breakthrough”, with “Scientists ‘close to breast cancer cure’” or even “Two years from developing ‘potential cure’ for breast cancer”.
It almost seems too good to be true – and it is. The headlines have come from a paper describing laboratory-based research that is [...]... Read more »
Castellano, L., Giamas, G., Jacob, J., Coombes, R., Lucchesi, W., Thiruchelvam, P., Barton, G., Jiao, L., Wait, R., Waxman, J.... (2009) The estrogen receptor- -induced microRNA signature regulates itself and its transcriptional response. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0906947106
- August 26, 2009
- 03:54 AM
- 876 views
Emergencies inspire crowd cooperation, not panic
by Christian Jarrett in BPS Research Digest
Crowd plus emergency equals mass panic, or so urban myths and Hollywood films would have us believe. The reality, recognised by social psychology for some time, is that people in crowds often behave in remarkably cooperative and selfless ways. A new study by John Drury and colleagues suggests that this kind of collaborative behaviour emerges when people in a crowd acquire a shared identity. And contrary to the "mass panic" perspective, an emergency can be the very catalyst that brings people together.If you've ever been on an underground train that gets stranded mid-tunnel, or on an aeroplane that's overstayed its welcome on a runway, you might have glimpsed a mild version of this feeling of a shared fate. With the temperature rising and information lacking, you and your fellow passengers stop feeling like strangers and start to feel united in your predicament.Drury and his colleagues asked 21 survivors of mass emergencies about these feelings of unity and about how much helping behaviour and orderliness they'd witnessed. Between them, the participants had been caught up eleven emergency situations including the crush at Hillsborough, the Harrods bomb of 1983, and the over-crowding at the Fatboy Slim beach party in 2002.Twelve of the disaster victims described feelings of unity among the crowd, whereas nine of them said it was more a case of everyone for themselves. In turn, the participants who said their crowd was united reported experiencing a sense of a shared fate; reported seeing and experiencing more examples of people helping others, including strangers; and they also reported more signs of orderliness such as queueing to escape."An aggregate of individuals becomes and acts as a psychological crowd when there is a cognitive redefinition of the self from a personal to a social identity," the researchers said. "...[W]e would suggest that in liberating us from the restrictions of individuality the psychological crowd is a crucial adaptive resource for survival in mass emergencies and disasters."The authors did also caution that their study has a number of serious limitations. Other survivors, less willing to talk than the current participants, might have had a different story to tell. Also, we know that human memory is extremely unreliable at the best of times, and some of the events described here had happened over two decades earlier._________________________________Drury, J., Cocking, C., & Reicher, S. (2009). Everyone for themselves? A comparative study of crowd solidarity among emergency survivors. British Journal of Social Psychology, 48 (3), 487-506 DOI: 10.1348/014466608X357893
... Read more »
Drury, J., Cocking, C., & Reicher, S. (2009) Everyone for themselves? A comparative study of crowd solidarity among emergency survivors. British Journal of Social Psychology, 48(3), 487-506. DOI: 10.1348/014466608X357893
- August 26, 2009
- 12:52 AM
- 614 views
Big Fish, Global Fish
by Laura Klappenbach in About Animals / Wildlife
Scientists have discovered that whale sharks, the largest fish in the sea, all belong to one big school. Instead of breaking down into lots of little social groups scattered throughout their range, whale sharks around the world intermix in a single, widespread breeding population. This is pretty impressive, considering the range of whale sharks stretches in a broad band around the planet's belly that includes the tropical and warm temperate seas between 30°N and 35°S.... Read more »
Schmidt JV, Schmidt CL, Ozer F, Ernst RE, Feldheim KA, Ashley MV, & Levine M. (2009) Low genetic differentiation across three major ocean populations of the whale shark, Rhincodon typus. PloS one, 4(4). PMID: 19352489
- August 26, 2009
- 12:21 AM
- 640 views
Tip of the Week: Acytelome, String and a new database
I recently read an article in Science entitled “Lysine Acetylation Targets Protein Complexes and Co-Regulates Major Cellular Functions” written by Choudhary et al. The research uses “high-resolution mass spectrometry to identify 3600 lysine acetylation sites on 1750 proteins” and “demonstrate[s] that the regulatory scope of lysine acetylation is broad and comparable with that of other [...]... Read more »
Choudhary, C., Kumar, C., Gnad, F., Nielsen, M., Rehman, M., Walther, T., Olsen, J., & Mann, M. (2009) Lysine Acetylation Targets Protein Complexes and Co-Regulates Major Cellular Functions. Science, 325(5942), 834-840. DOI: 10.1126/science.1175371
- August 25, 2009
- 09:34 PM
- 1,215 views
We Get Mail – Sea Sheppard Shenanigans Edition
by Dr. M in Deep Sea News
A few days ago DSN received a letter from one of our fans,
[sic]
To whom it may concern,
After reviewing your comments concerning the Sea Shepard, it is quite apparent that you do not appose the killing of whales by the Japanese!! It is also apparent that you support such actions by these savages!! The efforts that [...]... Read more »
Nagtzaam, G., & Lentini, P. (2008) Vigilantes on the High Seas?: The Sea Shepherds and Political Violence. Terrorism and Political Violence, 20(1), 110-133. DOI: 10.1080/09546550701723658
- August 25, 2009
- 06:45 PM
- 1,811 views
Freeloading pays off, but only up to a point.
by Iddo Friedberg in Byte Size Biology
Quorum sensing
Social behavior is not exactly the first term that comes to mind with relation to microbes. After all, we assume a certain amount of intelligence and an ability to implement a behavioral pattern in response to peer actions. Humans, yes. Apes, yes. Birds of a feather flock together… so birds, yes. Ants and bees [...]... Read more »
Diggle, S., Griffin, A., Campbell, G., & West, S. (2007) Cooperation and conflict in quorum-sensing bacterial populations. Nature, 450(7168), 411-414. DOI: 10.1038/nature06279
Czárán T, & Hoekstra RF. (2009) Microbial communication, cooperation and cheating: quorum sensing drives the evolution of cooperation in bacteria. PloS one, 4(8). PMID: 19684853
- August 25, 2009
- 04:59 PM
- 1,435 views
Noncaloric sweeteners might not be the solution either
by bikemonkey in DrugMonkey
The American Heart Associations recommendation to cut down on dietary sugar is all over the news. Discussion of this by Isis the Scientist triggered a comment from Callinectes :
Someone reading this may therefore assume diet drinks with Aspartame, Splenda, etc. may be okay because it's 0 calories and added "sugar". Can anyone comment authoritatively on this? The way I see it, it's still just empty calories and not very good for you when consumed regularly on a weekly or (heaven forbid) daily basis.
To which Isis responded:
One might argue that diet drinks still activate the "Hedonistic food pathways" in the brain (centers in the ventral tegmental area and nucleus accumbens) that lead us to associate reward with food intake, causing us to take in more energy-dense food... That said, I don't know of any multi-variate studies comparing risk between sugar drinks, diet drinks,... let's be clear that Aspartame and Splenda are zero calorie sweeteners, meaning they would technically not contribute to the AHA's recommended daily intake.
I am reminded of what I think of as a reasonably provocative series of observation from Susan Swithers and Terry Davidson at Purdue. Read the rest of this post... | Read the comments on this post...... Read more »
Swithers, S., & Davidson, T. (2008) A role for sweet taste: Calorie predictive relations in energy regulation by rats. Behavioral Neuroscience, 122(1), 161-173. DOI: 10.1037/0735-7044.122.1.161
Swithers SE, Baker CR, & Davidson TL. (2009) General and persistent effects of high-intensity sweeteners on body weight gain and caloric compensation in rats. Behavioral neuroscience, 123(4), 772-80. PMID: 19634935
- August 25, 2009
- 04:41 PM
- 1,336 views
The Pip and Pop Effect: Sound helps us find visual changes
by Dave Munger in Cognitive Daily
Take a look at the following picture:
Your job is to look for the one line that's either perfectly horizontal or perfectly vertical. It took me about 25 seconds to find it. Can you do better?
How about now?
A little easier, right?
But the task can be made difficult again by randomly changing the colors of all the other lines in the picture, a few at a time. Now you don't know which flash to look at and the task is just as hard as it was before.
But a team led by Erik Van der Burg found an interesting way to make the task easy again: just add a clicking sound that plays only when the horizontal or vertical line is displayed. They call this the "Pip and Pop Effect." The question which then arises is, why does the sound help?
The researchers showed displays like this to six paid volunteers, who were instructed to focus on the central dot and try to identify as quickly as possible whether the key line in the picture was horizontal or vertical. Half the time a tone was played in sync with the horizontal/vertical line changing colors. This graph shows the results:
Read the rest of this post... | Read the comments on this post...... Read more »
Van der Burg, E., Olivers, C., Bronkhorst, A., & Theeuwes, J. (2008) Pip and pop: Nonspatial auditory signals improve spatial visual search. Journal of Experimental Psychology: Human Perception and Performance, 34(5), 1053-1065. DOI: 10.1037/0096-1523.34.5.1053
- August 25, 2009
- 03:34 PM
- 704 views
Were ankylosaurs’ clubbed tails weapons?
by Zen Faulkes in NeuroDojo
I’m going to dare to step way outside my research expertise on this post, and look at a paper because I love me some dinosaurs. I particularly love ankylosaurs; there’s one within arm's reach in my office. Ankylosaurs are often depicted in art locked in combat with a savage meat eater like Tyrannasaurus rex, mainly relying on its armor, but wielding one massive weapon: a huge bony club at the end of its tail.I was disappointed to learn that the ankylosaurs I had as a kid (and that I still have on my desk) didn’t really exist, but were composites of many different species. Now, will Victoria Arbour destroy another childhood memory with her analysis of whether ankylosaurs could really use their clubbed tails as weapons?The first couple of paragraphs made me quaver in my decision to try understanding this paper. I have no idea what “postzygapophyses” are, except that they’re some part of skeletal anatomy. But I march on to the descriptions of the X-rays slices they did of some skeletons.Arbour estimated of the placement of tail muscles by looking at tendons that fossilized, and using crocodiles as a model. She suggests that the tail could be bent sideways, but says nothing about swinging it up, as is often depicted in art.To figure out the forces the animal might have been able to generate by swinging the tail, Arbour crunches some numbers using estimates of muscle mass, inertia, and so on. Unfortunately for a casual reader like me, the number presented are not linked to anything that I might reasonably be able to relate to. That comes in the discussion, fortunately, where the $64,000 question starts to take shape.: COuld these clubbed tails do damage?For some of the ankylosaurs with small clubs, Arbour argues, probably not. But some of the animals with larger clubs probably could. Since the shear forces needed vary from bone to bone, Arbour suggests future studies might try to quantify the strength of leg bones of meat eating dinosaurs as well as ribs of ankylosaurs. Arbour is more interested in the latter possibility, in fact: she suggests that the size of the clubs is such that juveniles probably did not have very large clubs, which she argues means they are unlikely to be defensive weapons. Instead, she thinks the clubs may have been used in ankylosaur on ankylosaur competition. This may be testable. Recent research on ceratopsian dinosaurs (like Triceratops) showed injuries consistent with the horns being used for competition. If ankylosaurs were clubbing each other, the breaks in the bones should be preserved.So the notion of ankylosaurs using their tails as weapons may not be completely wrong, the hypothesis has taken a bit of a beating here. (Pun fully intended!)ReferenceArbour, V. (2009). Estimating Impact Forces of Tail Club Strikes by Ankylosaurid Dinosaurs PLoS ONE, 4 (8) DOI: 10.1371/journal.pone.0006738... Read more »
Arbour, V. (2009) Estimating Impact Forces of Tail Club Strikes by Ankylosaurid Dinosaurs. PLoS ONE, 4(8). DOI: 10.1371/journal.pone.0006738
- August 25, 2009
- 03:04 PM
- 674 views
"Categorical perception" in neuroscience studies of speech
by Greg Hickok in Talking Brains
Old speech phenomena don't die they just become morphed into neuroscience studies. -Andrew LottoThe phenomenon of categorical perception appears to be riding the coattails of the resurgence of interest in motor theories of speech perception. Back in the motor theory heyday, categorical perception was all the rage. Listeners appeared to perceive speech sounds differently from non-speech sounds, i.e., categorically, and this was taken as evidence for the motoric nature of the speech perception process. The argument was something like this... Acoustic signals vary continuously. Articulatory patterns are categorical (/b/ is always produced bilabially). Perception mirrors the categorical nature of articulation. Therefore we perceive speech via our motor system.Problems with this view quickly arose. Non-human, and therefore non-speaking, animals such as chinchillas and quail, were found to exhibit categorical perception for speech sounds. Babies too, who hadn't yet acquired the ability to articulate speech, also exhibited categorical perception. Categorical perception of non-speech sounds was also demonstrated. Further, perception of speech sounds was found to be continuous if listeners were asked to rate how well a stimulus represented a given category rather than asking them to make a binary decision.Interest in categorical perception (CP) faded -- except in neuroscience where the pace of CP studies seems to be accelerating. Here's just a few from this year:Möttönen R, Watkins KE. Motor representations of articulators contribute tocategorical perception of speech sounds. J Neurosci. 2009 Aug 5;29(31):9819-25.Salminen NH, Tiitinen H, May PJ. Modeling the categorical perception of speechsounds: A step toward biological plausibility. Cogn Affect Behav Neurosci. 2009Sep;9(3):304-13. Clifford A, Franklin A, Davies IR, Holmes A. Electrophysiological markers of categorical perception of color in 7-month old infants. Brain Cogn. 2009Prather JF, Nowicki S, Anderson RC, Peters S, Mooney R. Neural correlates of categorical perception in learned vocal communication. Nat Neurosci. 2009 Feb;12(2):221-8. I hinted previously that the failure to use signal detection analysis methods in the context of categorical perception studies may have contaminated the whole field of CP research. Lori Holt recently pointed me to a paper by Schouten et al. 2003, provocatively titled "The End of Categorical Perception as We Know It". The point of the paper is exactly was I was hinting at: perception only looks categorical because of inherent bias in the tasks used to measure it. The traditional categorical-perception experiment measures the bias inherent in the discrimination task (Schouten et al. 2003, p. 71) Here's another interesting quote from this paper:Despite an auspicious beginning with a clear experimental definition ... categorical perception has in practice remained an ill-defined or even undefined concept, which could be used to underpin a variety of sometimes mutually exclusive claims, for example for or against the motor theory (p. 72) This is an interesting paper that is worth a close look. But back to bias... Let me illustrate very simply using some categorical perception data that I pulled from the literature. The graph below shows real data from a CP experiment using a GA-DA continuum. The task is explicitly categorical: subjects are asked to decide whether a stimulus is an example of GA or DA. This is not a good task to determine whether subjects perceive speech sounds categorically because it forces them to categorize. As Schouten et al. put it, "... if the nature of the task compels subjects to use a labelling strategy, categorical perception will be pretty much a foregone conclusion" (p. 77). Nonetheless, use of d-prime measures shows a rather different picture to standard measures. The vertical access is proportion of GA responses, and the horizontal axis is the various stimuli along the continuum. Perception looks nicely categorical. Now plot the same data in d-prime units. To do this you can calculate d' for each pair of adjacent stimuli (how well are Ss discriminating Stim1 from Stim2, Stim2 from Stim3, etc.). Plotted here is cumulative d'. We should see discontinuities in the cumulative d'. Instead we see a more continuous function.Have a look at the papers by Lori Holt and Andrew Lotto that I highlighted in a previous post as well as the Schouten et al. paper for more critical views on the nature of categorical perception. Then there's always long-time CP skeptic Dominic Massaro. His work on the topic is also worth a look. What are the implications for neuroscience studies of speech perception? Well, if CP is nothing more than task effects and/or subject bias, then by using CP paradigms to map speech perception systems, all that is being mapped is task strategies and/or subject bias. No wonder all these studies find effects in the frontal lobe! Schouten, B. (2003). The end of categorical perception as we know it Speech Communication, 41 (1), 71-80 DOI: 10.1016/S0167-6393(02)00094-8... Read more »
Schouten, B. (2003) The end of categorical perception as we know it. Speech Communication, 41(1), 71-80. DOI: 10.1016/S0167-6393(02)00094-8
- August 25, 2009
- 02:25 PM
- 616 views
An overnight therapy session...without a therapist
by William Lu in The Quantum Lobe Chronicles
Today I point you toward a fascinating review article by Walker and van der Helm looking at the crucial function of sleep on emotional regulation. Here is a snippet of their abstract:This review surveys an array of diverse findings across basic and clinical research domains, resulting in a convergent view of sleep-dependent emotional brain processing. On the basis of the unique neurobiology of sleep, the authors outline a model describing the overnight modulation of affective neural systems and the (re)processing of recent emotional experiences, both of which appear to redress the appropriate next-day reactivity of limbic and associated autonomic networks. Furthermore, a rapid eye movement (REM) sleep hypothesis of emotional-memory processing is proposed, the implications of which may provide brain-based insights into the association between sleep abnormalities and the initiation and maintenance of mood disturbances.Sleep FTW!Walker, M., & van der Helm, E. (2009). Overnight therapy? The role of sleep in emotional brain processing. Psychological Bulletin, 135 (5), 731-748 DOI: 10.1037/a0016570... Read more »
Walker, M., & van der Helm, E. (2009) Overnight therapy? The role of sleep in emotional brain processing. Psychological Bulletin, 135(5), 731-748. DOI: 10.1037/a0016570
- August 25, 2009
- 01:00 PM
- 1,787 views
Holding heavy objects makes us see things as more important
by Ed Yong in Not Exactly Rocket Science
Gravity affects not just our bodies and our behaviours, but our very thoughts. That's the fascinating conclusion of a new study which shows that simply holding a heavy object can affect the way we think. A simple heavy clipboard can makes issues seem weightier - when holding one, volunteers think of situations as more important and they invest more mental effort in dealing with abstract issues.
In a variety of languages, from English to Dutch to Chinese, importance is often described by words pertaining to weight. We speak of 'heavy news, 'weighty matters' and 'light entertainment'. We weigh up the value of evidence, we lend weight to arguments with facts, and our opinions carry weight if we wield influence and authority. These are more than just quirks of language - they reflect real links that our minds make between weight and importance.
Nils Jostmann from the University of Amsterdam demonstrated the link between weight and importance through a quartet of experiments. In each one, a different set of volunteers held a clipboard that either weighed 1.5 pounds or 2.3 pounds.
The extra 0.8 pounds were enough to make volunteers think that a foreign currency was worth more money. Forty volunteers were asked to guess the conversion rates between euros and six other currencies, indicating their estimate by marking a straight line. Those who held the heavier clipboard valued the currencies more generously, even though a separate questionnaire showed that they felt the same about the euro.
Money, of course, does have its own weight, so for his next trick, Jostmann wanted to stay entirely within the abstract realm. He considered justice - an area that is free of weight but hardly free of importance. Jostmann showed 50 volunteers a scenario where a university committee was denying students the opportunity to voice their opinions on a study grant. It was a potentially weighty issue, but more so to the students who held the heavy clipboard. They felt it was more important that the university listened to the students' opinions.
Read the rest of this post... | Read the comments on this post...
... Read more »
Jostmann, N., Lakens, D., & Schubert, T. (2009) Weight as an Embodiment of Importance. Psychological Science. DOI: 10.1111/j.1467-9280.2009.02426.x
- August 25, 2009
- 10:40 AM
- 574 views
The Neural Basis of Multitasking
In a headline-grabbing recent study, the NHTSA revealed that talking on a cell phone–even with a hands free headset–is effectively the same as driving with a .08 blood alcohol reading, or legal intoxication. Texting is even worse, but a poll released yesterday showed that a majority (52%) of the world’s drivers often have their thumbs [...]... Read more »
Dux, P., Tombu, M., Harrison, S., Rogers, B., Tong, F., & Marois, R. (2009) Training Improves Multitasking Performance by Increasing the Speed of Information Processing in Human Prefrontal Cortex. Neuron, 63(1), 127-138. DOI: 10.1016/j.neuron.2009.06.005
- August 25, 2009
- 10:15 AM
- 817 views
Actually, you ARE walking in circles
by Katie Kline in EcoTone
This post isn’t quite about ecology. But it’s about a phenomenon that many ecologists have ample experience with. A study out last week in Current Biology found that when people get lost in the wilderness, they actually do walk in circles.
Jan Souman of the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, and his [...]
... Read more »
Souman JL, Frissen I, Sreenivasa MN, & Ernst MO. (2009) Walking Straight into Circles. Current biology : CB. PMID: 19699093
- August 25, 2009
- 10:00 AM
- 1,273 views
I Must Be Guilty – the Video Says So
by David DiSalvo in Neuronarrative
A minor landslide of research from the past few years points to a dismaying fact about memory — it can be manipulated, far more often and extensively than previously thought. One implication of this realization is that eyewitness testimony, a stanchion of our criminal justice system, is no longer beyond reproach. Another is that in a world dominated by endlessly plyable electronic media, you can never be 100% sure that what you’re seeing is what really happened. Two recent studies from the journal Applied Cognitive Psychology illustrate that last point nicely.... Read more »
Wade, K., Green, S., & Nash, R. (2009) Can fabricated evidence induce false eyewitness testimony?. Applied Cognitive Psychology. DOI: 10.1002/acp.1607
Nash, R., & Wade, K. (2009) Innocent but proven guilty: Eliciting internalized false confessions using doctored-video evidence. Applied Cognitive Psychology, 23(5), 624-637. DOI: 10.1002/acp.1500
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