01 Properties of Neurons in the Vertebrate Cortex

• ependymal cells (cerebro-spinal liquor - plexus choroideus, neurgeneration as cell depots)

• oligodendrocytes (insulation)

• astrocytes (biochemical control of endothelia, nutrients, extracellular ion balance)

• microglia (migrate from bone marrow, immune system like macrophages)

• structural support

• life support (nutrients, oxygen, immune system)

• ionic insulation

• synaptic plasticity and synaptogenenis

• morphology (classical method)

• axonal termination

• type of synapses

• neurotransmitters

• triangular soma

• single axon

• apical and basal dendrites with spines

• input from local axons and upper cortical layers

• project to neighbouring cortical areas

• in layers II, III, V, VI

• silver staining method from 1873

• stains only 1 in a 100 neurons (mechanism unknown)

• stains only 50% of the length of axon/dendrites (too thin at the ends)

• star like shape

• excitatory (spiny) and inhibitory (aspiny)

• input from local axons only

• can target dendrite, soma or axon

• modulating excitation of pyramidal cells

• parvalbumin (layer IV)

• Somatostatin (layer V)

• 5HT3aR

• calcium regulating protein

• GABAergic

• L II-VI

• inhibition of e.g. pyramidal (on soma)

  • soma -> very fast inhibitory loop

• fast spiking basket and chandelier cells

  • basket: soma, proximal dendrite

    • main inhibitory system in neocortex

    • fast, precise, powerful

    • feedfordward inhibition

    • cortical rhythms

    • inh-exc balance

  • chandelier: axon initial segment

• regulating sensory plasticity

• inhibits growth hormon?

• input to apical pyramidal dendrite -> slower than PV

• GABAerg

• Martinotti: dendrites of PC

  • from layer V (+II+VI) axons to layer I, spread horizontally

  • facilitating excitatory activity, inhibition when overexcited

  • selective inhibition

• target layer 4

• mainly in layer I and II (associative) + III

• GABAerg

  • ionotropic serotonin and ACh-R

• sensonry processing and longrange interareal cortical communication

• long-range cortical communication

• neuroglial:

  • linking networks of interneurons

  • eliciting slow, long-lasting IPSPs

• whole brain: 170 billion cells

• 86000 million / 85B neurons

  • most neurons in Cerebellum

  • counting: voxel -> mixing -> counting nuclei -> extrapolating

• primates relatively more neurons for structure mass

• birds have denser forebrains than primates

• weight from water

  • 500kcal a day

• around 8000-10000 synapses per neuron

• every neuron can be reached within 2-4 steps

  • all neurons receive recurrent feedback (2-neuron loops)

• number of synapses relates to storage capacity of brain

• synchronized input

• within hemisphere (most connections, 90%)

• callosal

• cortico-thalamical (more than thalamo-cortical so the cortex can control own input)

• brainstem-cortex

• all connections are reciprocal

• dense mesh of axons and dendrites at the border to adjacent areas

• axons running parallel to cortical surface layer

• with matter axons

• 
  

• almost no effects on arm coordination when cute into gray matter

• disabled when cut in white matter

—> suggests horizontal intracortical interaction in less extensive and fundamental in cerebral integration as assumed

1/4 input

2/3/5/6 output

1: axons of Martinotti cells connect to neighboring columns

2/3: outgoing axons to other cortical areas

4: incoming stimulus informastion fromn thalamus

5: outgoing mayelinated axons form fibre tracts in the white matter

6: to thalamus