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The brain is indeed stacked with blood vessels, as shown in a 3D model in Fig. 1.
Fig. 1. 3D-printed model of blood vaculature. Source: Biobots.
The blood supply on the surface of a live brain is readily seen during a craniotomy (Fig. 2.)
Fig. 2. Surface of the brain. Source: The Sterile Eye.
When freshly prepared, the interior of the brain appears ...
36
Unfortunately, we are all still "confuzzled" by how memory works. We are far from a complete understanding of how memory is stored and recalled. Nonetheless, we do know a little, so read on.
Your understanding of basic neural function is almost correct. First, an individual neuron will signal through its single axon onto the dendrites of many downstream ...
24
According to the highly respected WORMATLAS: A Database of Behavioral and Structural Anatomy of Caenorhabditis elegans, the number is invariable in this animal, one of the most studied in the world.
There are 302 neurons in the nervous system of C. elegans; this number is invariant between animals. Each neuron has a unique combination of properties, such ...
18
Its not clear that this is true.
Working with animals has been a little disconcerting over the past 50-60 years. In the distant past, I think most evolutionary anthropologists and their like bought into the idea that humans were completely uniquely intelligent and spiritual. But the more we try to define human sensibilities apart from other animals, the ...
15
You would need to live a long, long, long, long time for this to become remotely problematic.
Your question seems to suppose that a memory is "stored" by a neuron, and since neurons have mass, then the more memories we have the more our brains will weigh. Actually, neurogenesis is pretty rare in the adult brain--most of the cortex is fixed, and new neurons ...
12
Short Answer
Yes, autapses exist, though the role of excitatory autapses in particular is unclear.
Long Answer
A lot of your assumptions are wrong for biological neurons (I'm suspecting you have a background in artificial neural networks but that might be inaccurate). These don't directly impact your question of whether these connections exist, but I ...
11
First of all, let me clear out that these numbers are calculated, not observed (obviously, nobody has counted the number of neurons in any part of brain). So, take these with a grain of salt.
I was unable to find any report that collects and displays all numbers together (Bio Numbers too didn't yield significant information). So I will compile here all the ...
answered Jul 11 '17 at 12:19
another 'Homo sapien'
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10
Well, Erickson et al (2011) attribute the increase in brain volume in the aerobic exercise group to brain-derived neurotrophic factor (BDNF).
Specifically (p. 3020):
In fact, we found here that changes in serum BDNF levels were
associated with changes in anterior hippocampal volume; an important
link because the hippocampus is rich in BDNF, and BDNF ...
10
Many Nematodes do not use traditional hox genes instead the have a strange set up which controls cell placement directly. This means individual adults of many nematode species have the exact same number of cells, it can even be used to identify species. So having the exact same number of neurons is what one should expect in nematodes. https://www.ncbi.nlm....
9
I would like to point out some ways your understanding is wrong. "Neural networks" are usually a computer science term, only very, very loosely based on actual neural networks. The idea of layers in a neural network is pretty much an invention of computer science, it doesn't really reflect the reality. Also, neurons are not binary switches. It isn't so much ...
9
Your image comes from the wiki page Aneurysm. The figure legend on the wiki page identifies it as:
Angiography of an aneurysm in a cerebral artery
I am not an MD so I chose to first dig up a similar appearing cerebral angiography with the aneurysm identified (dark protruding spot indicated by the arrow):
Source: WestJEM, UC Irvine
Taking into account ...
8
Although tinnitus is usually described as a ringing in the ear, there's a whole range of tunes, buzzes, whooshing sounds, humming and hissing sounds that are described of as tinnitus. The sounds can either genuinely be there or be perceived to be there. If it is genuinely there it suggests muscles ate at play or some blood vessel disease if the sounds are in ...
8
The evolutionary pressure on the location of the pituitary is likely not the reason why it resides at the basis of the brain. Instead, its (partly) neural origin makes it anatomically (and functionally) part of the brain. Why would it migrate out of the brain when it doesn't have to? What would the evolutionary pressure be on increasing the length of the ...
8
Short answer
Smooth pursuit is driven by retinal slip, which is determined by external input registered peripherally in the retina.
Background
The smooth pursuit system is a system designed to minimize retinal slip, i.e., the movement of an image across the retina. Saccades are rapid eye movements meant to fixate quickly on a new target (Purves et al., 2001)...
8
A "touch" or "haptic" sensation will be much faster due to several reasons:
Haptic feedback can be processed without the presence of any higher-order cognitive processing, therefore meaning that the signals are being processed via a monosynaptic route.
There are short reflex arcs between the spinal cord and the limb (meaning that you can react before you ...
8
The brain does not control all bodily movements. Some movements are to a great extent controlled by neural networks in the spinal cord. The spine contains a network which is pre-programmed to control the muscles in frequently-used movements such as running or swimming in chickens. This is why a chicken can run away after you chop its head off. Likewise, ...
7
I haven't read anything particularly about dendrites being reshaped, though I would expect them to be as flexible as other parts of the cells.
The more commonly discussed topic (in my literary experience) is reshaping of the axon's branches before forming synaptic terminals. These branches are not fixed even in adults - neurons can grow new and retract old ...
7
The newest and most accurate method (far more accurate than older extrapolating/manual counting methods (Stereology) and yielding some surprising results) to estimate number/density of neurons/cells in brains is Isotropic Fractionator to my knowledge. Using this keyword you find some recent papers, comparing different brain areas (cerebral cortex, cerebellum,...
7
I think that the advantages of using both hands with equal ease is quite evident whether it be sports, at your work or while you are doing your household chores.
An obvious advantage is using both hands to write or draw with both at the same time.
I would be focusing on the disadvantages that may be faced.
1) Ambidextrous people are more prone to ...
7
One of the many advantage of an all-or-none system is that resources can be conserved for timing events that require synchronized collaboration between many cells (like locomotion). Binary behavior may also partially be a side effect of speed and efficient long-distance information transfer (which is one of the great advantages of neurons as cells in the ...
7
The developmental growth of bone tissue is hormonally controlled. It is, as far as I know, not under direct neuronal control. Before reaching adolescence, the long bones (mainly in the arms and legs) grow in the epiphyseal plate, the area of the bone where cartilage is formed and ossified on the diaphyseal side, thereby lengthening the bone. The longitudinal ...
7
Often artificial neurons are created with conventions that zero is "rest" and 1 is "threshold". The unit starts at 0, and when it reaches 1 it will send an input to all of its targets and be reset back to 0.
This isn't exactly how real biological neurons work, but its a reasonable approximation in some contexts (and can do real world computations).
Most of ...
7
Short Answer:
"Always" is always a dangerous term in biology.
Longer Answer:
What does a neuron do if it does not get stimulated/receives no signal for a long time. Will it die ... or try to find new connections that might send signals?
What neurons do when they aren't stimulated depends on the neuron and phase of development. Typically, thresholds for ...
6
As you say, a neuron can have thousands of inputs via its thousands of dendrites. Each of those dendrites can have a synaptic connection to the (axonic) output of a different neuron. So the neuron can take inputs from thousands of different neurons, not just from one other neuron.
At the other end of the neuron, the output of the axon can form synaptic ...
6
Short answer
Axons can be over a meter long, but dendrites are never that long. Distance in the body is covered by axons. The dendritic part of skin receptors is generally considered to be the receptor part and the receptor part only. The elongated structure leading to the soma, as well as the axonal part to the spinal cord are generally considered to be one ...
6
Excitatory neurons in layer 4 are not all stellate in all cortical areas, for example see Smith and Populin, 2001 who show clearly that in auditory cortex most excitatory cells in layer 4 are pyramidal. There are also many cortical areas that have no clear "layer 4" and also do not contain spiny stellate cells.
In general, intracortical circuitry is not ...
6
Short answer
Based on shape and approximate position, I think it is the corpus callosum.
Background
I think it is the corpus callosum (Fig. 1). The corpus callosum is approximately 10 cm in length and is C-shaped. It becomes thicker posteriorly, as is also evident in your image. The corpus callosum is a structure consisting of white-matter, containing about ...
6
Neurons are suspended, as you say, in an extracellular matrix. Brain tissues are a little bit more specific. Here I quote a few summaries from literature to answer and give your a perspective on your basic question. In bold I highlight important statements which differentiate the brain's ECM from the ECM found elsewhere in the body.
Barros, Franco & ...
5
One thing I think you're missing: a perceptron model and a spiking model aren't mutually exclusive. In fact, in perceptrons, people usually use a sigmoid function. That's not a coincidence: it kind of simulates a spike. If you were to model an organism such as C. elegans, whose neurons aren't spiking (but use "graded action potentials"), you would use ...
5
Mechanical force can compress neurons and cause action potentials as you probably experienced in the form of hitting the funny bone. Strong enough acceleration of the brain tissue may be causing massive excitation of neurons as indicated by animal EEG study. It suggests that the loss of consciousness is due to generalized epileptic seizure. However, it is ...
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