BIO254:Chemoaffinity: Difference between revisions
No edit summary |
No edit summary |
||
| Line 4: | Line 4: | ||
A DRAFT | A DRAFT | ||
The Chemoaffinity Hypothesis proposes that axons differentially recognize chemical signals produced by target matching cells. In this way, neurons connect only to specific cells or groups of cells. This selective recognition is the basis for establishing proper functional neuronal connections. The Chemoaffinity Hypothesis was first proposed by the neuropsychologist Roger Wolcott Sperry (August 20, 1913 - April 17, 1994), based on classic experiments performed | Introduction | ||
The Chemoaffinity Hypothesis proposes that axons differentially recognize chemical signals produced by target matching cells. In this way, neurons connect only to specific cells or groups of cells. This selective recognition is the basis for establishing proper functional neuronal connections. The Chemoaffinity Hypothesis was first proposed by the neuropsychologist Roger Wolcott Sperry (August 20, 1913 - April 17, 1994), and is based on classic experiments performed on frogs. | |||
When first proposed, the Chemoaffinity Hypothesis stood in contrast to a competing model called the Resonance Hypothesis. The Resonance Hypothesis predicts nonspecific neuronal connections during early developmental stages. Functional circuits are created by activity dependent rewiring of the initial random connections. Both classic and modern experiments seem to support the Chemoaffinity Hypothesis over the Resonance Hypothesis, making it the most widely accepted model of neuronal wiring. | |||
Early Experiments | |||
In the early 1940, Roger Sperry performed a series of experiments on the visual system of frog. In his experiments, the eye of a frog is severed from the original connection to the tectum, and then rotated 180o and re-implanted. The retinal ganglion cells are able to re-generate axons that project back to the tectum, and re-establish functional synapses. Insterestingly, this rotation of the eye resulted in a subjectively inverted visual world for these frogs: when attracted by a fly in its upper visual field, the frog always lunges downwards. This inappropriate behavior strongly implied that the frog behaves as if its entire visual world is inverted. | In the early 1940, Roger Sperry performed a series of experiments on the visual system of frog. In his experiments, the eye of a frog is severed from the original connection to the tectum, and then rotated 180o and re-implanted. The retinal ganglion cells are able to re-generate axons that project back to the tectum, and re-establish functional synapses. Insterestingly, this rotation of the eye resulted in a subjectively inverted visual world for these frogs: when attracted by a fly in its upper visual field, the frog always lunges downwards. This inappropriate behavior strongly implied that the frog behaves as if its entire visual world is inverted. | ||
These experiments led to the conclusions that when original optic connections were severed, the regenerating axons of the retina grow back to their original location in the tectum and re-established these well-organized connections. Based on these conclusions, Sperry proposed that spatial gradients of chemical cues expressed by tectal cells likely mediate this process during development, i.e. each optic fiber and each tectal neuron possessed chemical cues that uniquely determined their neuronal type and position and optic fibers could utilize these cues to selectively navigate to their predetermined target cell. This inference was subsequently formulated into a general explanation of how neurons form well-organized connections during development and became known as the chemoaffinity hypothesis. | These experiments led to the conclusions that when original optic connections were severed, the regenerating axons of the retina grow back to their original location in the tectum and re-established these well-organized connections. Based on these conclusions, Sperry proposed that spatial gradients of chemical cues expressed by tectal cells likely mediate this process during development, i.e. each optic fiber and each tectal neuron possessed chemical cues that uniquely determined their neuronal type and position and optic fibers could utilize these cues to selectively navigate to their predetermined target cell. This inference was subsequently formulated into a general explanation of how neurons form well-organized connections during development and became known as the chemoaffinity hypothesis. | ||
Modern Experiments | |||
Major Reference: | Major Reference: | ||
Revision as of 22:17, 8 October 2006
A DRAFT
Introduction
The Chemoaffinity Hypothesis proposes that axons differentially recognize chemical signals produced by target matching cells. In this way, neurons connect only to specific cells or groups of cells. This selective recognition is the basis for establishing proper functional neuronal connections. The Chemoaffinity Hypothesis was first proposed by the neuropsychologist Roger Wolcott Sperry (August 20, 1913 - April 17, 1994), and is based on classic experiments performed on frogs.
When first proposed, the Chemoaffinity Hypothesis stood in contrast to a competing model called the Resonance Hypothesis. The Resonance Hypothesis predicts nonspecific neuronal connections during early developmental stages. Functional circuits are created by activity dependent rewiring of the initial random connections. Both classic and modern experiments seem to support the Chemoaffinity Hypothesis over the Resonance Hypothesis, making it the most widely accepted model of neuronal wiring.
Early Experiments
In the early 1940, Roger Sperry performed a series of experiments on the visual system of frog. In his experiments, the eye of a frog is severed from the original connection to the tectum, and then rotated 180o and re-implanted. The retinal ganglion cells are able to re-generate axons that project back to the tectum, and re-establish functional synapses. Insterestingly, this rotation of the eye resulted in a subjectively inverted visual world for these frogs: when attracted by a fly in its upper visual field, the frog always lunges downwards. This inappropriate behavior strongly implied that the frog behaves as if its entire visual world is inverted.
These experiments led to the conclusions that when original optic connections were severed, the regenerating axons of the retina grow back to their original location in the tectum and re-established these well-organized connections. Based on these conclusions, Sperry proposed that spatial gradients of chemical cues expressed by tectal cells likely mediate this process during development, i.e. each optic fiber and each tectal neuron possessed chemical cues that uniquely determined their neuronal type and position and optic fibers could utilize these cues to selectively navigate to their predetermined target cell. This inference was subsequently formulated into a general explanation of how neurons form well-organized connections during development and became known as the chemoaffinity hypothesis.
Modern Experiments
Major Reference:
Meyer, R. L., 1998, Roger Sperry and his chemoaf_nity hypothesis, Neuropsychologia, 36, 957-980
Recent updates to the site:
- N
- This edit created a new page (also see list of new pages)
- m
- This is a minor edit
- b
- This edit was performed by a bot
- (±123)
- The page size changed by this number of bytes
22 April 2024
|
|
19:28 | "Pick and Place" Assembly of Parts Using PDMS - Amy Lim, Rylie Costello 4 changes history +1 [Rcostello (4×)] | |||
|
|
19:28 (cur | prev) −2 Rcostello talk contribs (→Nanowires) | ||||
|
|
19:26 (cur | prev) 0 Rcostello talk contribs (→Biology-Inspired Solution) | ||||
|
|
15:03 (cur | prev) +2 Rcostello talk contribs (→At the Microscale) | ||||
|
|
15:02 (cur | prev) +1 Rcostello talk contribs (→Overview) | ||||
| 09:24 | CHEM-ENG590E:Wiki Textbook diffhist +16 Rcostello talk contribs (→Chapter 15 - Other Topics) | ||||
| 09:24 | Move log Rcostello talk contribs moved page "Pick and Place" Assembly of Parts Using PDMS - Amy Lim to "Pick and Place" Assembly of Parts Using PDMS - Amy Lim, Rylie Costello | ||||
| 08:59 | "Pick and Place" Assembly of Parts Using PDMS - Amy Lim diffhist −2,792 Rcostello talk contribs (→"Pick and Place" for Microfluidics) | ||||
21 April 2024
| 22:55 | Lee:JC diffhist +24 Wooin Lee talk contribs (→2024) | ||||
| 17:42 | Ernesto-Perez-Rueda:Publications diffhist +55 Ernesto Perez-Rueda talk contribs | ||||
19 April 2024
|
|
21:58 | Hu 2 changes history +58 [Hugangqing (2×)] | |||
|
|
21:58 (cur | prev) −8 Hugangqing talk contribs | ||||
|
|
21:58 (cur | prev) +66 Hugangqing talk contribs | ||||
18 April 2024
| 15:01 | Pan:Who we are diffhist +14 Taopan talk contribs | ||||
|
|
15:00 | Pan:Methods 2 changes history +456 [Taopan (2×)] | |||
|
|
15:00 (cur | prev) +2 Taopan talk contribs | ||||
|
|
14:59 (cur | prev) +454 Taopan talk contribs | ||||
|
|
14:56 | Pan:Publications 2 changes history +396 [Taopan (2×)] | |||
|
|
14:56 (cur | prev) +74 Taopan talk contribs | ||||
|
|
14:54 (cur | prev) +322 Taopan talk contribs | ||||
| 13:03 | BioMicroCenter:Pricing diffhist +166 Challee talk contribs | ||||
|
|
12:58 | BioMicroCenter:Singular Sequencing 2 changes history +124 [Challee (2×)] | |||
|
|
12:58 (cur | prev) +14 Challee talk contribs (→Things to Consider) | ||||
|
|
12:57 (cur | prev) +110 Challee talk contribs | ||||
|
|
12:12 | BioMicroCenter:Tecan Freedom Evo 7 changes history +1,746 [Noelani Kamelamela (7×)] | |||
|
|
12:12 (cur | prev) +4 Noelani Kamelamela talk contribs | ||||
|
|
12:12 (cur | prev) +3 Noelani Kamelamela talk contribs | ||||
|
|
10:13 (cur | prev) +7 Noelani Kamelamela talk contribs (→verrity Chemagic 360) | ||||
|
|
10:08 (cur | prev) −42 Noelani Kamelamela talk contribs (→verrity Chemagic 360) | ||||
|
|
10:08 (cur | prev) +86 Noelani Kamelamela talk contribs (→verrity Chemagic 360) | ||||
|
|
09:34 (cur | prev) +23 Noelani Kamelamela talk contribs (→verrity Chemagic 360) | ||||
|
|
09:32 (cur | prev) +1,665 Noelani Kamelamela talk contribs | ||||
| 11:42 | 3D Cell Culture - McLean Taggart, Emma Villares, Maximillian Marek, Scott LeBlanc, Adam Lyons and Jacob Belden diffhist −3 Sarah L. Perry talk contribs | ||||
|
|
09:35 | BioMicroCenter 2 changes history +92 [Noelani Kamelamela (2×)] | |||
|
|
09:35 (cur | prev) +60 Noelani Kamelamela talk contribs | ||||
|
|
09:20 (cur | prev) +32 Noelani Kamelamela talk contribs | ||||
| 09:32 | Upload log Noelani Kamelamela talk contribs uploaded File:Chemagic360.jpg (from manual) | ||||
