Transcript hendrickx

Connectomes
A big difference between the Connectome and
Genome projects is in data volumes. The difference
between 1.6 GB for the genome and my estimate of
13 PB for the connectome is a factor on the order of
10 billion. A projection based on Moore’s Law – still
the most reliable guide to our ability to handle data
volumes – stipulates 67 years to advance from the
2003 achievement of the Genome Project to what is
needed to record all connections in a human brain.
A diffusion tensor imaging scan of a healthy brain adds color to its white matter. "It's
not perfect...but it's so much better than anything we've had before," says Gregory
Sorensen, an associate professor of radiology at Harvard Medical School. Image credit:
Zephyr/Science Photo Library
Diffusion ellipsoid. Three eigenvectors are demonstrated, with
the principal eigenvector along the Z direction. Courtesy of Dr
Andrei I. Holodny, MD.
Separation: steer to avoid crowding
local flockmates
Alignment: steer towards the average
heading of local flockmates
Cohesion: steer to move toward the
average position of local flockmates
The Human Connectome Project
Tractography-based segmentation of the human
thalamus.
White Matter Tractography
• Association fibers
– Superior longitudinal fasciculus (SLF)
– Arcuate fasciculus (AF)
– Uncinate fasciculus (UF)
– Fronto-occipital fasciculus (FOF)
– Extreme capsule (EmC)
– Middle longitudinal fasciculus (MdLF)
– Inferior longitudinal fasciculus (ILF)
– Cingulum bundle (CB)
Arcuate fasciculus (AF)
Reverse Engineering
Healthy Human Brain
86 billion neurons and 85 billion neuroglial cells7000 connections per neocortical neuron in adults. (Young children have many
more. A unique number identifying a single neuron in a population of 86 billion can be expressed in 37 bits of information. To
identify the two neurons would take 37 + 37 = 74 bits per connection, or 518,000 bits (65 kilobytes) per neuron. Multiplying by 86
billion neurons gives a total of 5.59 petabytes (PB) of information. That’s just for the basic connectivity map: a record of which
neurons are connected to which. More information would be required. We would also need to know the type of synaptic
connection (whether electrical or chemical, and if chemical, the specific neurotransmitter to which the synaptic receptor
responds). As that is largely a function of the transmitting neuron, it might not need to be expressed as a property of the
connection; but if it were, then estimating 100+ neurotransmitters, that would take another 9 bits per connection. The 3D spatial
location of the synapse is also important; it could be expressed to 1 nm precision (probably overkill) using 93 bits. Therefore we
could express the type and location of each neural connection, and the identities of the transmitting and receiving neurons, in 74
+ 9 + 93 bits = 176 per connection. That multiplies out to over 13 PB for the whole brain. Although my brain weighs just 2% of my
body, the ‘informational weight’ of my brain – dominated by the connectivity map – might well come in at 95% or higher!
Let’s work with those numbers. Remember, the 13 PB estimate is only for neural connectivity. Other properties of the neurons are
important, as are attributes of the glia and blood vessels of the brain. But the volume of information required to capture those
attributes is on the level of whole cells rather than connections; as such it is insignificant compared to the connectivity
information. One more petabyte should be enough. Accordingly, I will revise my estimate of the volume of information required to
replicate a person to a whopping 15 petabytes. Although that’s 15 times my first estimate, it makes very difference to the
prediction of when human replication technology will become commercial reality. Assuming Moore’s Law, a factor of 15 adds
eight years. We should be able to transmit 15 PB in one second by 2057.
A local capillary network in rat brain tissue from the visual cortex.
The central core region seems to be the brain's "default" network. The brain contains a central
core consisting of 8 distinct subregions in the posterior medial area of the cortex. This core
radiates a dense network of fibres to other parts of the cortex, and may act as an integrated
system which co-ordinates the combined activity of the two hemispheres.
POSTERIOR CINGULATE CORTEX AND PRECUNEUS
Moral Sensitivity
Processing Self Relevant Stimuli
Frontooccipital tracts processing information from Frontal Eye
Fields to occipital areas and secondary projection into parietal
association areas and the “the Theater of the Mind”
A reconstruction of 114 rod bipolar nerve cells from a piece of mouse retina. The
dense bundles (top) are dendrites, and the sparser processes below are axons (credit:
MPI for Medical Research)
Dendrites form dense bundles where bipolar cells receive signals from rod
photoreceptors (gray spheres) staining the neurons of a section of tissue with heavy
metals to make them visible (credit: MPI for Medical Research)
Virtual reconstructions of nerve fiber tracts crossing the corpus callosum in the human (right) and
rhesus monkey brain in vivo (left). green = prefrontal lobe, light blue = premotor and
supplementary motor areas, dark blue = primary motor cortex, red = primary sensory cortex,
orange = parietal lobe, yellow = occipital lobe, violet = temporal lobe
Axial tractographic image demonstrates white-matter tracts in the brain in the leftright (red), anterior-posterior (green), and superior-inferior (blue) directions.
Courtesy of Dr Andrei I. Holodny, MD.
Brain Network Related To Intelligence
Identified
IQ inheritance: By comparing the brain scans of twins, scientists discovered that the
quality of the fatty tissue that insulates neural wires is largely inherited. The parietal
lobe, which is involved in logic and mathematics, is 85 percent genetically determined,
whereas the visual cortex is about 76 percent, and the temporal lobe, which is
involved in learning and memory, is only 45 percent genetically determined.
Credit: David Shattuck, Arthur Toga, Paul Thompson/UCLA
Parcellation Scheme for human left
lateral parietal cortex
A network graph showing all of the synaptic connections in the pharynx of the
nematode Prisitonchus pacificus. 53 ROI.
First ever 3D map of a brain’s neurons.
This is a map of an owl-monkey brain.
Dynamic Network Connectivity (DNC):
A new form of rapid neuroplasticity
Advantages of DNC:
Mechanisms that weaken network
connectivity:
Mechanisms that strengthen network
connectivity:
Optimal Levels of Dopamine D1
Sculpt Network Inputs:
Genetic Insults in Mental Illness:
Genetic insults to intracellular DNC signaling pathways
in schizophrenia:
Genetic Insults to extracellular DNC
signaling pathways in ADHD:
Environmental insults to DNC with
normal aging