Scientists make advances in neuroscience and vision research
This is a confocal micrograph of a single cone bipolar cell (green) that extends its dendrites to receive synaptic inputs (red dots) from a local population of cone photoreceptor terminals (violet). Credit: Sammy Lee
Thanks to a new study of the retina, scientists at UC Santa Barbara have developed a greater understanding of how the nervous system becomes wired during early development.
The research team examined the connectivity of nerve cells, called neurons, in mice. Neurons communicate with one another via synapses where the dendrites and axon terminals of different cells form contacts. This is where nerve signals are transmitted from one neuron to another.
Scientists have understood for some time how neuronal activation at developing synapses contributes to the patterns of connectivity observed in maturity, explained Ben Reese, senior author and professor in UCSB's Neuroscience Research Institute and the Department of Psychological & Brain Sciences.
Incoming activity plays a critical role in sculpting neuronal form and the elaboration of synaptic connections. The new research shows, by contrast, how relationships between neighboring cells of the same type independently regulate neuronal size and connectivity.
The researchers circumvented the difficulty of visualizing the three-dimensional relationships between neurons within the brain by working within the retina. The retina is an outgrowth of the brain during embryonic development, and is a precisely layered structure in which the cells, their dendrites and their axons are restricted to discrete strata. "This makes the visualization and analysis of neuronal morphology and connectivity far simpler," said Reese.
The scientists used two genetically modified mouse models to modulate the density of one particular type of retinal neuron, a class of cone bipolar cell. Cone bipolar cells relay information from the population of cone photoreceptors to the retinal ganglion cells. The latter are neurons that in turn project information to locations within the brain where further visual processing of the retinal image takes place.
The lead author on the study, Sammy Lee, was a postdoctoral researcher working in Reese's lab and supported by a C.J. Martin National Health & Medical Research Council fellowship from Australia during the course of the study. Lee labeled individual cone bipolar cells with a fluorescent dye through a new microinjection procedure developed by Patrick Keeley, a graduate student in the Reese lab.
"What Dr. Lee has shown is that cone bipolar cells modulate the size of their dendritic fields (branched extensions of the neuron) in association with the local density of like-type neurons," said Reese. "One line of mice has conspicuously fewer cone bipolar cells, each now with a larger dendritic territory, while the other line shows heightened densities and correspondingly smaller dendritic fields."
Other studies have suggested such homotypic (like-type) modulation of dendritic field size, but the current study directly shows this modulation following genetic manipulation of neuronal density, according to Reese.
Additionally, the researchers found that connectivity with the afferent population of cone photoreceptors is impacted directly, with the larger dendritic fields being innervated by more cones, and the smaller dendritic fields connecting with fewer cones. At any individual cone, the number of dendritic endings associating with that cone was not observed to change, so that the total number of connections made by a cone bipolar cell was remarkably plastic, defined solely by the number of cone contacts formed.
"This developmental plasticity in dendritic growth and synapse number may be well-suited to ensure uniform coverage and connectivity between two populations of neurons afferents and their targets when the number of cells in each population is specified independently," said Reese.
Other studies from Reese's lab, recently reported in The Proceedings of the National Academy of Sciences and Investigative Ophthalmology and Visual Science, showed how neuronal number is tightly specified genetically, yet is highly variable between different strains of mice. "Wiring together two populations, each of which may vary nearly two-fold in size, yet independent of each other, might best be served by such homotypic plasticity during early development," he said.
Studies like these may prove relevant for re-establishing connectivity following nerve cell re-specification or replacement in degenerative diseases, particularly as advances in stem cell biology make this an increasing possibility, said Reese.
Provided by University of California - Santa Barbara
- Scientists make strides in vision research May 20, 2011 | not rated yet | 0
- From eye to brain: Researchers map functional connections between retinal neurons at single-cell resolution Oct 06, 2010 | not rated yet | 0
- Getting wired: How the brain does it Aug 26, 2009 | not rated yet | 0
- Hi-res detector used by researchers to map neural circuits of the retina Oct 12, 2010 | not rated yet | 0
- Researchers to develop probes to study cellular GPS Nov 10, 2009 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
How can there be villous adenoma in colon, if there are no villi there
10 hours ago As title suggest. Thanks :smile:
How can there be a term called "intestinal metaplasia" of stomach
May 21, 2013 Hello everyone, Ok Stomach's normal epithelium is simple columnar, now in intestinal type of adenocarcinoma of stomach it undergoes "intestinal...
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
Ratio of Hydrogen of Oxygen in Dessicated Animal Protein
May 13, 2013 As an experiment, for the past few months I've been consuming at least one portion of Jell-O or unflavored Knox gelatin per day. I'm 64, in very...
- More from Physics Forums - Medical Sciences
More news stories
(HealthDay)—Migraines and depression can each cause a great deal of suffering, but new research indicates the combination of the two may be linked to something else entirely—a smaller brain.
Neuroscience 1 hour ago | 5 / 5 (1) | 0 |
Moving objects attract greater attention – a fact exploited by video screens in public spaces and animated advertising banners on the Internet. For most animal species, moving objects also play a major ...
Neuroscience 4 hours ago | not rated yet | 0 |
It is known that signs of neurological disorders such as Alzheimer's and Huntington's disease can appear years before the disease becomes manifest; these signs take the form of subtle changes in the brain and behavior of ...
Neuroscience 4 hours ago | not rated yet | 0
Scientists have reversed behavioral and brain abnormalities in adult mice that resemble some features of schizophrenia by restoring normal expression to a suspect gene that is over-expressed in humans with ...
Neuroscience 5 hours ago | 5 / 5 (1) | 0 |
Researchers at Johns Hopkins have unraveled the molecular foundations of cocaine's effects on the brain, and identified a compound that blocks cravings for the drug in cocaine-addicted mice. The compound, already proven safe ...
Neuroscience 5 hours ago | not rated yet | 0 |
(HealthDay)—Implementation of systematic monitoring for medication adherence will allow for identification of barriers to adherence and tailoring of interventions, according to a viewpoint piece published ...
19 minutes ago | not rated yet | 0
Every day, their baby stopped breathing, his collapsed bronchus blocking the crucial flow of air to his lungs. April and Bryan Gionfriddo watched helplessly, just praying that somehow the dire predictions weren't true.
49 minutes ago | 5 / 5 (1) | 0
A new study shows there is a gender gap when it comes to behavior and self-control in American young children – one that does not appear to exist in children in Asia.
53 minutes ago | not rated yet | 0
As the world prepares for what may be the next pandemic strain of influenza virus, in the H7N9 bird flu, a new UC Irvine study reveals that the 2009 H1N1 swine flu pandemic was deadliest for people under the age of 65, while ...
49 minutes ago | not rated yet | 0
(HealthDay)—The American Cancer Society, which is celebrating on Wednesday a century of fighting a disease once viewed as a death sentence, is making a pledge to put itself out of business.
19 minutes ago | not rated yet | 0
National Lung Screening Trial (NLST) investigators also conclude that the 20 percent reduction in lung cancer mortality with low-dose computed tomography (LDCT) versus chest X-ray (CXR) screening previously reported in the ...
45 minutes ago | not rated yet | 0