Public Library of Science (PLoS) Where Does Consciousness Come From?. 2009, ScienceDaily

– Consciousness arises as an emergent property of the human mind. Yet basic questions about the precise timing, location and dynamics of the neural event(s) allowing conscious access to information are not clearly and unequivocally determined.

Some neuroscientists have even argued that consciousness may arise from a single “seat” in the brain, though the prevailing idea attributes a more global network property.

Do the neural correlates of consciousness correspond to late or early brain events following perception? Do they necessarily involve coherent activity across different regions of the brain, or can they be restricted to local patterns of reverberating activity?

A new paper suggests that four specific, separate processes combine as a “signature” of conscious activity. By studying the neural activity of people who are presented with two different types of stimuli – one which could be perceived consciously, and one which could not – Dr. Gaillard of INSERM and colleagues, show that these four processes occur only in the former, conscious perception task.

This new work addresses the neural correlates of consciousness at an unprecedented resolution, using intra-cerebral electrophysiological recordings of neural activity. These challenging experiments were possible because patients with epilepsy who were already undergoing medical procedures requiring implantation of recording electrodes agreed to participate in the study. The authors presented them with visually masked and unmasked printed words, then measured the changes in their brain activity and the level of awareness of seeing the words. This method offers a unique opportunity to measure neural correlates of conscious access with optimal spatial and temporal resolutions. When comparing neural activity elicited by masked and unmasked words, they could isolate four converging and complementary electrophysiological markers characterizing conscious access 300 ms after word perception.

All of these measures may provide distinct glimpses into the same distributed state of long-distance reverberation. Indeed, it seems to be the convergence of these measures in a late time window (after 300 ms), rather than the mere presence of any single one of them, which best characterizes conscious trials. “The present work suggests that, rather than hoping for a putative unique marker – the neural correlate of consciousness – a more mature view of conscious processing should consider that it relates to a brain-scale distributed pattern of coherent brain activation,” explained neuroscientist Lionel Naccache, one of the authors of the paper.

The late ignition of a state of long distance coherence demonstrated here during conscious access is in line with the Global Workspace Theory, proposed by Stanislas Dehaene, Jean-Pierre Changeux, and Lionel Naccache.

Journal reference:

Adapted from materials provided by Public Library of Science

Toronto, 2009 (IANS) It may soon be possible to erase bad memories from the human brain.

Canadian scientists at the University of Toronto and the local Hospital for Sick Children have found a link between a given memory and specific neurons – the cells in the brain that transmit information – that store it.

The human brain has over 100 billion neurons, but memories are stored in only small number of them. Scientists have been trying to identify these precise neurons that encode a given memory.

Now in their experimental study on mice (which has 100 million neurons), the Toronto research team has succeeded in identifying precise neurons that carry a particular memory.

Unlike in the past when scientists had deleted an entire brain region in mice to try and erase a memory in the hopes of finding out about how memories are normally stored, the Toronto team has succeeded in removing only the small portion of neurons that stored a specific memory.

“Though previous studies have provided important evidence suggesting that specific neurons are involved in a memory, we believe this (study) paper is the first to establish causal links,” a university statement quoted study leader and physiology professor Sheena Josselyn as saying.

In their previous experiments, the same research team had found evidence that in mice, fear memories are stored in specific neurons within a brain structure known as the lateral amygdala (LA) that have a high amount of a specific protein (CREB).

This means that CREB levels helps dictate which neurons are involved in storing a memory.

Now in their latest study, the research team destroyed only these LA neurons with high levels of CREB and found that mice no longer remembered the fearful event. The research team also showed that random removal of any LA neurons does not erase the fear memory. You have to remove only specific set of neurons that store a memory.

“Our experiences, both good and bad, teach us things,” said study leader Josselyn.

“If we did not remember that the last time we touched a hot stove we got burned, we would be more likely to do it again. So in this sense, even memories of bad or frightening experiences are useful.

“However, there are some cases in which fearful memories become maladaptive, such as with post-traumatic stress disorder or severe phobia. Selectively erasing these intrusive memories may improve the lives of afflicted individuals,” she said.

“Our studies suggest that one strategy would be to target interventions to that small subset of neurons actually involved in storing a memory, rather than the entire brain. It sounds like a futuristic film, but our results in mice do provide proof-of-principle that this may one day be possible in humans,” said co-researcher Paul Frankland.

Yale University, June/July 2009, . Brain Energy Use Key To Understanding

Consciousness, ScienceDaily  –  High levels of brain energy are required to maintain consciousness, a finding which suggests a new way to understand the properties of this still mysterious state of being, Yale University researchers report. 

At its simplest, consciousness can be defined as the ability to respond meaningfully to external stimuli. Most studies of consciousness have used imaging technology to try to pinpoint areas of brain activity during tasks such as memorization or problem solving.

There are two problems with such an approach, said Robert G. Shulman, Sterling Professor Emeritus of molecular biophysics and biochemistry at Yale and lead author of the paper, to be published this week in the online edition of the journal Proceedings of the National Academy of Sciences. First, functional magnetic resonance imaging has shown that many areas of the brain, not just one or two, are recruited during tasks such as memory tests and are scant help in studying the state of being conscious. Second, the amount of energy used in such tasks is minute, about one percent of baseline energy available to the brain.

“Neuroimaging has been looking at the tip of the iceberg,” Shulman said. “We looked at the rest of the iceberg.”

What is the other 99 percent of energy consumption doing?

Shulman and colleagues have proposed that it is needed to maintain a person in a state of consciousness. Heavily anesthetized people are known to show approximately 50 percent reductions in cerebral energy consumption. When the paws of lightly anesthetized rats with rather high baseline energy levels were stroked, fMRI signals were received in the sensory cortex and in many other areas of the brain. In heavily anesthetized rats the signal stopped at the sensory cortex. Both the total energy and the fMRI signals changed when the person or animal lost consciousness.

“What we propose is that a conscious person requires a high level of brain energy,” Shulman said.

The finding has profound implications for our understanding of the connection between the brain and consciousness, Shulman said. “You can think of consciousness not as a property of the brain, but of the person.”

Anesthesiologists consider a person to be in a behavioral state of consciousness when he or she can respond to simple stimuli. Properties of this state, such as the high energy and the delocalized fMRI signals, allow the person to perform the interconnected activities that make up our everyday lives. Shulman suggests that these more energetic properties of the brain support human behavior and should be considered when interpreting the much weaker signals that are typically recorded during fMRI studies.

Other Yale researchers involved in the study are professors Fahmeed Hyder and Douglas L. Rothman.

The study was funded by the National Institutes of Health.

Adapted from materials provided by Yale University.

GoogleNews.com, Washington Business Journal, July 2009, by Tierney Plumb  —  Universities, life sciences companies, health care investors and patient advocates have banded together to inform policy makers, the media and the public about regenerative medicine.

The Washington, D.C.-based Alliance for Regenerative Medicine aims to advance scientific research in regenerative medicine, which includes such methods as using stem cells to grow cells. Stem cell research was pioneered by University of Wisconsin researcher James Thomson.

The Alliance, which is being co-operated by H&K and Adjuvant Global Advisors, expects many more companies, universities and organizations to join on in the coming weeks.

Some of the initial charter members include the Wake Forest Institute for Regenerative Medicine, Stanford University, Geron, Johnson & Johnson, and Aldagen. Investor organizations include Kleiner, Perkins and Proteus Ventures.

“Regenerative medicine holds enormous promise,” said Thomas Okarma, president and CEO of Geron Corp. “It is critical to educate policy makers about this technology in order to gain the Federal support necessary to turn that potential into cost-effective treatments for patients.”

ScienceDaily (July 21, 2009) – Dental and tissue engineering researchers at Tufts University School of Dental Medicine and the Sackler School of Graduate Biomedical Sciences at Tufts have harnessed the pluripotency of human embryonic stem cells (hESC) to generate complex, multilayer tissues that mimic human skin and the oral mucosa (the moist tissue that lines the inside of the mouth). 

 “For the first time, we have established that a single source of hESC can provide the multiple cell types needed to interact within a three-dimensional tissue model to generate complex, multilayer tissues. We are a step closer to a practical therapy to help with diseases of the skin and mouth,” said Jonathan Garlick, DDS, PhD, professor of oral and maxillofacial pathology at Tufts University School of Dental Medicine and a member of the cell, molecular & developmental biology program faculty at the Sackler School of Biomedical Sciences at Tufts.

“Researchers have been seeking methods to grow skin-like tissues outside of the body using new sources of stem cells such as hESC, with the goal of advancing regenerative medicine as a new therapy to replace or repair damaged or diseased tissue. Little is known about how hESC can be developed into the multilayer tissues similar to those that line the gums, cheeks, lips, and other areas in the mouth. We used in vitro tissue engineering techniques to produce skin-like tissues that mimic the lining tissues found in the oral cavity,” said Garlick.

Using a combination of chemical nutrients and specialized surfaces for cell attachment, an hES cell line (H9) was directed to form two distinct specialized cell populations. The first population forms the surface layer (ectodermal, the precursor to epithelial tissue), while the second is found beneath the surface layer (mesenchymal).

Following the isolation and characterization of these cell populations, the researchers incorporated them into an engineered, three-dimensional tissue system where they were grown at an air-liquid interface to mimic their growth environment in the oral cavity. Within two weeks, tissues developed that were similar in structure to those constructed using mature cells derived from newborn skin, which are the current gold standard for tissue fabrication. 

“These engineered tissues are remarkably similar to their human counterparts and can be used to address major concerns facing the field of stem cell biology that are related to their clinical use. We can now use these engineered tissues as ’tissue surrogates’ to begin to predict how stable and safe hESC-derived cells will be after therapeutic transplantation. Our goal is to produce functional tissues to treat oral and skin conditions, like the early stages of cancer and inflammatory disease, as well as to accelerate the healing of recalcitrant wounds,” said Garlick. 

First author Kyle Hewitt is a graduate student in cell, molecular & developmental biology program at the Sackler School of Graduate Biomedical Science at Tufts and is a member of Garlick’s lab.

This study was supported by the National Institute of Dental and Craniofacial Research at the National Institutes of Health.

Garlick is also director of the Center for Integrated Tissue Engineering (CITE) at Tufts University School of Dental Medicine.

Journal reference:

  • 1. Hewitt et al. Three-Dimensional Epithelial Tissues Generated from Human Embryonic Stem Cells. Tissue Engineering Part A, 2009; 090710171045048 DOI: 10.1089/ten.tea.2009.0060

Adapted from materials provided by Tufts University, Health Sciences.


Virtual reconstruction of the pelvis of a female Neanderthal from Tabun (Israel). The colours indicate the individual bone fragments that were fit together. The gray wedge shows the estimated configuration of the sacrum (lower part of the spinal column). (Credit: Tim Weaver, University of California) 

Max Planck Society,. Virtual Reconstruction of a Neanderthal Woman’s Birth Canal Reveals Insights Into Evolution Of Human Child Birth, ScienceDaily – Researchers from the University of California at Davis (USA) and the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel).

Although the size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans, the shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans. The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in the evolution of humankind (PNAS, April 20th, 2009).

Childbirth in humans is more complicated than in other primates. Unlike the situation in great apes, human babies are about the same size as the birth canal, making passage difficult. The birth mechanism, a series of rotations the baby must undergo to successfully navigate its mother’s birth canal, distinguishes humans not only from great apes but also from lesser apes and monkeys.

It has been difficult to trace the evolution of human childbirth because the pelvic skeleton, which forms the margins of the birth canal, tends to survive poorly in the fossil record. Only three fossil female individuals preserve fairly complete birth canals, and they all date to earlier phases of human evolution.

Tim Weaver of the University of California (Davis, USA) and Jean-Jacques Hublin, director at the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) now present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel). The size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans. However, its shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans, without rotation of the baby’s body.

A significant shift in childbirth apparently happened quite late in human evolution, during the last 400,000 – 300,000 years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neanderthals and the lineage leading to present-day humans.

The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in human evolution. The computer files will be available from the websites of University of California at Davis and the Max Planck Institute for Evolutionary Anthropology.

Journal reference:

  • 1. Timothy D. Weaver, Jean-Jacques Hublin. Neandertal birth canal shape and the evolution of human childbirth. Proceedings of the National Academy of Sciences, 2009; 106 (20): 8151 DOI: 10.1073/pnas.0812554106

Adapted from materials provided by Max Planck Society.