I was wondering how instinct or other forms of 'memory' are encoded in DNA. It seems there is a reservoir of knowledge that is stored in some way. Is this currently explained in genetics?
---Caroni said:Studies in barn owls have revealed that the additional learned circuits that had been assembled during a sensitive period in juvenile birds were turned on and off in the adult through mechanisms distinct from those that turn innate natural circuits on and off (disinhibition versus AMPA/NMDA ratios for the innate and learned circuits, respectively), suggesting that innate and acquired circuit arrangements can be distinguished functionally
This is an interesting phenomena. It can actually be suppressed by suppressing the signaling of the neurons involved. If you don't suppress their activity, they try to make correlations on what are essentially noise signals in the system and "hard wire" the system by misinterpreting the meaningfulness of those signals.Ygggdrasil said:if you were to take a newly born baby and cover its eyes for its entire early childhood, the child's neural circuitry for interpreting visual stimuli would not develop and the child would be blind despite the fact that the child's eyes work perfectly well.
Hi Ygggdrasil. Are you saying that if an animal's eyes were covered in the same way the child's eyes were, the animal would still be able to see?In many animals, basic instincts and behaviors are encoded in the organism's DNA. The DNA provides instructions for the animal to build specific neural circuits to perform certain behaviors in response to certain stimuli. For example, flies have an escape response triggered by certain stimuli, such as a shadow passing over them. Researchers have identified a specific nerve cell in the fly that controls this response and this nerve cell is the same in all flies of the same species. Artificial stimulation of this nerve cell triggers the escape response. The nematode worm, C. elegans is probably the animal where the neural circuitry for many innate behaviors, as well as the genetic elements controlling the development of the circuitry, is best understood (for example, see http://www.ncbi.nlm.nih.gov/books/NBK20005/).
In humans and other higher mammals, however, the situation is very different. Humans are born with very few innate behaviors and instincts. For example, whereas many animals (insects, fish, reptiles, amphibians, etc.) are fully capable of walking, feeding themselves and even surviving independently after birth, human babies can do practically nothing after birth and cannot survive without a caretaker. The difference here is that the DNA of humans does not specify a wiring diagram for the brain. Rather this wiring diagram is formed in response to the experiences of the individual. For example, if you were to take a newly born baby and cover its eyes for its entire early childhood, the child's neural circuitry for interpreting visual stimuli would not develop and the child would be blind despite the fact that the child's eyes work perfectly well. ...
At the broad level, the locations of certain cell types in the body is genetically programmed genetically, but at the fine level, this is not true for vetebrates. For example, in examining the wiring between nerves and a particular muscle in mice, researchers found substantial variation in the wiring diagram even between the same muscle on the left and right side of the same animal:I guess that DNA codes the location information of every cell in relationship to other cells, sort of a 3D map (a blue print) of how to build the body (identical twins have almost identical physical parameters), if my guess is correct do we know what is the mechanism that interprets the code in DNA into coordinations? This is interesting because as I understand ribosome translates the information coded in DNA to proteins and I'm not aware of any other thing that performs similar task but ribosome.
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1000032Conventionally, the organization of a neural circuit is studied by sparsely labeling its constituent neurons and pooling data from multiple samples. If significant variation exists among circuits, this approach may not answer how each neuron integrates into the circuit's functional organization. An alternative is to solve the complete wiring diagram (connectome) of each instantiation of the circuit, which would enable the identification and characterization of each neuron and its relationship with all others. We obtained six connectomes from the same muscle in adult transgenic mice expressing fluorescent protein in motor axons. Certain quantitative features were found to be common to each connectome, but the branching structure of each axon was unique, including the left and right copies of the same neuron in the same animal. We also found that axonal arbor length is often not minimized, contrary to expectation. Thus mammalian muscle function is implemented with a variety of wiring diagrams that share certain global features but differ substantially in anatomical form, even within a common genetic background.