Ask a Neuroscience Professor

[frob2900]

Why are mice such good candidates for scientific research on various things in psychology and neuroscience? Why not, say, squirrels (or some other arbitrarily chosen small mammal) instead?

I'll go out on a limb and say I think it's because mice breed more easily/faster or have more young so there's a good stock of replacement mice.

Squirrels also have a lot of fur (e.g. on their tail) so the risk of a researcher being allergic to them is probably higher.

 

[El_Machinae]

How are they different from a virus?

A prion is a normal protein that's been folded into a strange shape. This shape is a nucleating agent, such that it causes its brother proteins (of the same type) to turn into the same strange shape.

I think of it as a crystalising agent, like when you supercool water (and its still liquid), but if you introduce an ice crystal, the entire jar will turn to ice.

A virus, by comparison, is a foreign agent that brings along its own genetic material. This genetic material causes the host cell (that's infected) to produce and replicate viruses and export them

Why are mice such good candidates for scientific research on various things in psychology and neuroscience? Why not, say, squirrels (or some other arbitrarily chosen small mammal) instead?

They also use rats and cats as other examples of 'small mammals'. Mice are cheap though, and a there are a gazillion genetic variants.

Mark: what would happen if we measured mouse brain mRNA, and then found the human homologue to those genes and then made a mouse such that its brain expressed human mRNA? Would it be a better animal to work with regarding drug testing, or would it be gimped?

 

[Fifty]

I was listening to a Chomsky lecture about his work in linguistics, and he made the claim that a large part of neuroscience rejects the notion that "we can study language as part of the world".

Do you have any idea what the crap he meant by that, and if he is correct?

 

[Mark1031]

Mark: what would happen if we measured mouse brain mRNA, and then found the human homologue to those genes and then made a mouse such that its brain expressed human mRNA? Would it be a better animal to work with regarding drug testing, or would it be gimped?

I don't know of any cases where human and mouse genes are not interchangable. I;m surhe there are some but the coding region of most mammalian genes are very similar. For drug testing you would prefer the human versions but really it is usually some reaction specific to human physiology that nerfs a drug so having 1 gene substituted wouldn;t help much. That said a biotech company put the entire human immune system into the mouse. They sold 2 of those mice for $200 mil.

 

[Mark1031]

I was listening to a Chomsky lecture about his work in linguistics, and he made the claim that a large part of neuroscience rejects the notion that "we can study language as part of the world".

Do you have any idea what the crap he meant by that, and if he is correct?

I have no idea what he means. Many neuroscientists study language and the development of language. I guess it depends what :as part of the world means".

 

[El_Machinae]

I was wondering if different parts of the neocortex had markedly different gene expressions. I don't know the mouse neocortex as well as I should, so I'll use human examples. Are there any marked gene differences between (say) the left temple and the right temple, or the like? Are there differences between the Wernicke area and the Broca area that could be indicators of those areas?

The reason I ask is because I thought specific genes would make good locuses to insert genes for programmed cell death (in the mouse, now, of course). If we were able to trigger PCD in specific regions of the neocortex due to some environmental trigger, then we could cause deliberate lesions of original neocortex tissue in specific regions.

 

[Mr. Blonde]

If you have some knowledge on addiction:
How bad is caffeine intake? I drink on average about 3 big cups black coffee which equals 0.5-1 g caffeine total per day. Am I considered addicted, and what kind of symptoms can I expect if I quit from one day to the other?
Shouls I be more cautous with alcohol? In football season I have an intake of 15*0.5l of beer per week (around 5% alcohol v/v) distributed to 2 or 3 days.

 

[Mango]

I think that I can answer this one. Often people are told that they're only using a tiny proportion of their brain at once because
a) only some of the neurons are firing at any specific time
b) some parts of the brain are used for specific tasks

Obviously if a part of the brain isn't engaged in the current task then it won't contribute much to thought processes.
However, neurons that don't fire convey just as much information as neurons that do. If all neurons were firing all the time then no information would be conveyed, and the brain wouldn't be working.
We need 'not to be using' parts of the brain in order for the used areas actually to be doing something useful.

I have heard that we only use a small portion of our brain because the human circulatory system is insufficiently developed to provide adequate amounts of blood to a bipedal species. In other words there just isn't enough getting up there because we stand up staight. I've also heard rumors that wisemen in ancient times would have a small hole drilled into the back of their head, exposing their brain cavity, which would increase blood circulation, but that's probably just a rumor. Anywho, do you think it might have something to do with this?

I mean I understand your answer. The brain has specific parts for specific tasks, so unless you're doing those tasks then there's no reason for it to be active, but I'm under the impression that we've mapped the entire brain and are yet to find any use for large portions of it. Supposedly we just don't use it at all throughout our lives.

Oh and another unfounded rumor but supposedly Einstein used around 20 to 40% of his brain. I'm not sure where I heard this one either, but I think the rumor goes that he had an enlarged skull that allowed more use of something.

 

[El_Machinae]

No, we use our entire brain. At least, we use our entire adult brain. The brains of infants have partial die-off of neurons that aren't being used sufficiently to retain them.

 

[Mark1031]

I was wondering if different parts of the neocortex had markedly different gene expressions. I don't know the mouse neocortex as well as I should, so I'll use human examples. Are there any marked gene differences between (say) the left temple and the right temple, or the like? Are there differences between the Wernicke area and the Broca area that could be indicators of those areas?

The reason I ask is because I thought specific genes would make good locuses to insert genes for programmed cell death (in the mouse, now, of course). If we were able to trigger PCD in specific regions of the neocortex due to some environmental trigger, then we could cause deliberate lesions of original neocortex tissue in specific regions.

The answer to that is clear in the mouse and it is by and large no. You can see the expression of all the mouse genes in the brain here. I personally have spent hours searching this for interesting cortical patterns and only found a few genes and not with really clear regional cutoffs. They also had a nature paper on this work where they discuss this in more detail.

 

[El_Machinae]

Thanks for answering, and for summarising hours of your own labour.

I'm starting to fall into "the neocortex is a generic sheet" camp, then. The placement of our various functional areas would seem to be due to the placement of neuronal inputs (optic nerves, etc.) which would have genetic uniqueness, no?

 

[Mark1031]

If you have some knowledge on addiction:
How bad is caffeine intake? I drink on average about 3 big cups black coffee which equals 0.5-1 g caffeine total per day. Am I considered addicted, and what kind of symptoms can I expect if I quit from one day to the other?
Shouls I be more cautous with alcohol? In football season I have an intake of 15*0.5l of beer per week (around 5% alcohol v/v) distributed to 2 or 3 days.

No you sound pretty typical. Just from personal experience you will probably have some headache if you quit coffee.

 

[Mark1031]

Thanks for answering, and for summarising hours of your own labour.

I'm starting to fall into "the neocortex is a generic sheet" camp, then. The placement of our various functional areas would seem to be due to the placement of neuronal inputs (optic nerves, etc.) which would have genetic uniqueness, no?

I would say No. I was just at a big meeting on this question. Many people had your view ie that there are a lot of genetically unique neurons. There is some but not as much as many would think. I think a pyramidal cell in the auditory cortex and sensory cortex are probably genetically almost identical.

 

[Mark1031]

BTW we just published a paper in Science that got some press and might be interesting to you. You can hear me talk about it on the BBC here. Starts about 12 min in.

 

[El_Machinae]

That's what I meant by 'generic sheet'. The fact that the auditory cortex is the auditory cortex would be because of the input from the auditory/vestibular nerves. Surely those must have more unique genes (compared to the optic nerves)?

And if not, then the retinal nerves must have unique gene expressions verses the hair nerves ("hair nerves"? That seems wrong) near the tectorial membrane of the ear? At some point, they're designed/interpret to receive different inputs for processing.

edit: x-post. Thanks, I'll watch it.

 

[Tank_Guy#3]

Here is a subject that was brought up in my psych class: How much memory can the human brain store?

Is it a fixed amount or does it appear to vary?

Do you believe that the regular intake of certain drugs (stimulants like caffeine, etc) reduce the risk of degenerative brain diseases, and is that much (if any) data to back this up?

What kind of "-ologists" do those in your field have a hard time getting along with? (Like, those darn [blanks] are spreading their rubbish again).

 

[Mark1031]

That's what I meant by 'generic sheet'. The fact that the auditory cortex is the auditory cortex would be because of the input from the auditory/vestibular nerves. Surely those must have more unique genes (compared to the optic nerves)?

And if not, then the retinal nerves must have unique gene expressions verses the hair nerves ("hair nerves"? That seems wrong) near the tectorial membrane of the ear? At some point, they're designed/interpret to receive different inputs for processing.

edit: x-post. Thanks, I'll watch it.

I guess I didn't understand you. There is vast genetic difference in the primary sensory organs- hair cells retina. There are genetic programs that guide axons can cell movement during development. However in the adult cortex there is not much genetic diversity from region to region.

 

[El_Machinae]

I guess I didn't understand you. There is vast genetic difference in the primary sensory organs- hair cells retina. There are genetic programs that guide axons can cell movement during development. However in the adult cortex there is not much genetic diversity from region to region.

You've now entirely answered my questions. I was hoping for some difference in the neocortex, due to what types of nerves each region was receiving inputs from (though I wouldn't have predicted it).

 

[Mark1031]

Here is a subject that was brought up in my psych class: How much memory can the human brain store?

Is it a fixed amount or does it appear to vary?

I don't know. It is quite a lot. For short term memory most people can remember 7 numbers for a brief period. There is some small variance and there are real savants or people who have developed techniques to allow them to remember much more. There are also real reports of photographic memory although I have not seen it studied in detail.

Do you believe that the regular intake of certain drugs (stimulants like caffeine, etc) reduce the risk of degenerative brain diseases, and is that much (if any) data to back this up?

I don't think it is clear. I had read reports that smoking prevented Alzheimers but a new report shows it increases dementia (possibly by increasing small strokes). I donl;t know anything that is a clear cut benifit.

What kind of "-ologists" do those in your field have a hard time getting along with? (Like, those darn [blanks] are spreading their rubbish again

None really. In every field there are individuals that are resented for either shoddy work or overstatement of the conclusions. Neuroscience is particularly susceptible to grandiose overstatement based on limited data.

 

[El_Machinae]

I was listening to an interview with Brenda Milner (of HM fame*) where she was discussing her estate after she dies.

Is there a reason why neuroscientists aren't more accepting of cryonics, preserving the brain in order to be awoken and repaired later? I'd think that most (successful) neursoscientists are materialists and I don't know what's wrong with the cryonics 'theory' such that it's ignored.

*For the audience: HM was the patient upon whom the character in Memento was based. The guy couldn't form short-term memories.