Neural Networks Flashcards
One neuron can have as many as 1000 dendrites and
60 trillion synapses
Born with all the neurons you are ever going to have
About 10 billion in the cortex
Neuronal connection form
Billions of connections
The cortex (comprised if neuron/cell bodies) becomes thicker (or thinner) based on…
The density, degree, or number of dendritic connections each of those neurons makes
Dendritic connections provide us with ultimately neural networks
Yeppp
External stimulus causes sets of neurons to fire
Build a more enriched dendritic carpet
Neural networks
Make more connections
= cortical thickening
Via typical development, enriched and stimulating environment
Via stimulus- specific deliberate repetitive practice
Neural networks
Make fewer connections= cortical thinning
Prune away unneeded or redundant or inefficient connections- selective thinning
Prune away unused it unstimulated or neglected connections= cortical thinning
Arborization of dendrites
Increase receptive connectivity of each neuron
Which in turn supports development of rich neural networks
And efficient connections–> which is shaped by experiences, efforts, learning, practice or lack thereof
Pools may be divergent
One presynaptic cell engages several pod synaptic cells
One item trigger many related items
Pools of neurons may be convergent
Many presynaptic cells engage one post synaptic cell
Put hand in bag to figure out object
Pools engage to form
Networks
What do neural networks do
Engage in simultaneous firing of a group of linked neurons
This network is wired up to perf tin a specific type of cognitive or motor it sensory activity
What is white matter in the cns
The axons of the billions of neurons which move away from the cell body
White matter in the cns transmit neural impulses to the
Dendrites of other neurons which then wire up to form neural networks
Neural networks are insulted with
A fatty /lipid substance called myelin which is whitish in color Call tracts (not nerves-that is in pns)
Where is white matter in cns
Cerebrum
Subcortex
Cerebellum
Brainstem
White matter in cerebrum
Connecting gray matter/cortical structures; connecting basal ganglia and limbic structures to all the places they go
White matter in subcortex
Running through thalamus nuclei on way to and/or from the cortex to the brainstem or cerebellum
White matter in cerebellum
Moving to/from thalamus, limbic, cortex
White matter in brainstem
Moving to/from cranial nerves, or to/from spinal cord, to connect with spinal nerves
Efferent down thru spinal cord
Afferent up thru brainstem
Types of tracts (myelinated axon fibers) in cns
Projection
Association
Commissural
Projection. Travel
In a vertical manner, carry motor and sensory
Two types of projection
Corona radiati
Internal capsule
Corona radiati
Most superior go to motor and premotor, motor strip
Internal capsule
Fibers bundle up and form right thick cable going thru brainstem –>at level of subcortical structures (one loss of blood supply, knock out many fibers)
Association fibers direction
Bidirectional channels of communication between areas of one hemisphere
Parts of association fibers
Superior longitudinal fasciculus
Inferior longitudinal fasciculus
Uncinate fasciculus
Cingulum
Commissural fibers travel
In a horizontal manner, connecting two hemispheres- communicate between
Commissural fibers
Corpus callosum
Anterior commissure
Do assoc fibers cross over into another hemi
No
Projection fibers (one type of white matter tract in cns)
Move in vertical manner
Project to points ‘far away’ in cns
Axons are relatively long
Many are heading down/up from either spinal or cranial nerves
Anterior limb of corona radiati
Corticothalamic tracts
From cortex to thalamus
Generally excitatory
Forms a circuit with thalamocortical tracts
Anterior limb thalamocortical tracts
From thalamus to cortex
Mostly to sensory processing and pre motor
Generally inhibitory motor movements
Anterior limb corticopontine tracts
From motor cortex to pins
Eventually to cranial nerves
Genu corticibular tracts
From motor cortex to brainstem in general
For cranial nerve output
Posterior limb corticospinal tracts
Innervate spinal neurons for motor outputs
projection fibers from spinal input
From skin joints to primary sensory cortex
Corona radiati
Anterior limb
Genu
Posterior limb
Internal capsule (projection fibers)
The convergence if fibers within the corona radiati
Association fibers (another type of white matter tract in cns)
Connect areas within one hemisphere
Shorter ones exist within one lobe
Longer ones move between lobes
Superior longitudinal fasciculus
Connects frontal lobe with occipital lobe
Has feeder branches that connect temporal to Wernickes and surrounding parietal
Arcuate fasciculus
Many of the superior longitudinal fibers take a sharp curve and head down through the temporal lobe
Uncinate fasciculus
Inferior aspect from anterior temporal horn. Inferior aspect of prefrontal cortex
More direct route
Cingulum (last association fiber)
C shaped Connects limbic lobe with temporal lobe Right below cingulate gyrus Just above the corpus callosum Move in ace like manner- memory, face and emotional processing
Commissural fibers ( last type if white matter tracts in cns)
Connects the two hemi
Move laterally l-r ( if you are looking to the brain from a coronal cut)
Corpus callosum
Best known for its job connecting the l and r hemi
So intra-hemispheric comm and integration
Right hemi
Spatial, musical, temporal
Emtional and social component
L hemi
Language, analytic, verbal
Subcallosal area
Limbic structure
Thalamus
Hypothalamus
Basal ganglia
Anterior and posterior commissures
Two other Commissural fiber tracts located
Anterior To or posterior to the corpus callosum
Anterior commissures connectss
Two olfactory bulbs
Amygdalae
Temporal lobes
Posterior commissures connects
The two thalamic nuclei
Not everyone have this
Connectomics
The process of using high resolution imaging to create a map (connectome) of the brains neural networks
Principles of neural transmission
Convergence (multiple neurons-axons- converge to fire one individual neuron
Divergence one neuron-axon- has an impact on multiple other receiving neurons
Neural transmission dorm neural networks that are
Highly complex
Extremely vulnerable
