Raw Notes : Gyorgy Buzsaki at SFN

Comparative Neuroanatomy with Buzsaki

Large Scale recording of neuronal activity in behaving rodents

Want to separate the types neurons of they record from and control.

Step 1 : extract single neurons from extracellular electrodes

Extracellular electrode arrys give best spatiotemporal resolution at depth in awake freely moving rodent.

Neurons are not point sources of action potentials. The action potential back propagates to dendrites.

Extracellular fields of many neurons strongly overlap.

Can be fooled if you look just in one layer, an action potential recorded in layer IV may actually originate in layer 5. 

Try to infer intracellular features from extracellular recording properties.

Depolarization of the cell during AP chages its intracellular waveform and is refelected in the extracellular waveform. Hence wave-shape sorting algorhitms can be fooled by changing depolarization levels.

Use multidimensional clustering to figure out which spikes come from which neurons.  

Step 2 : From single neurons to neuron types (taxonomy)

Compare the timing of spiking of each neuron relative to the theta cycle.  Also compare in the sharp wave cycle.  

After 6 years of works, they classify constellations of neurons involved in different network patterns.  

Interneurons : Timers and segreators.  Timing is locked to theta cycle.  

Looking at the assembly patterns you can predict the choice of an animal.

see Pastalkova, Science 2008.

In prefrontal cortex.  Use cross-correlation techniques across the population that is recorded.

Short latency large narrow peak indicates monosynaptic excitatory connection. Pyramidal -> Interneurons.  

Short latency spike suppression indicates monosynaptic inhibition. Inter-> Pyr

Has a database of >2500 neurons.  Comparte peak latency and waveshape to the correlation data that defines each as inhibitory or excitatory.  These two groups cluster in the peak latency vs. waveshape space.  So now they have a signature to classify excitatory or inhibitory neurons.

Interacting with circuits

Determine the neuron types

Perturb the correlations with optogenetics to test hypotheses

Simultaneous recoding and stimulation with optical fiber attached to silicon probe (Sebastian Royer @ Janelia)

Figure 8 maze.  

Can record place cells that have characteristic firing pattern during running through the maze.  Can see CHr2 stimulation in some cells.  Neurons fire in stereotyped pattern with theta cycle except when stimulated with ChR2, then it follows the ChR2 stimulation cycle.

Wishlist

Better probes, stimulating on every shank rather than just one shank.  

Larger density recording sites

Further volume reduction

Identification of neurons

Light activation and scilencing of neurons

Improved neurron clustering algorithims