What do you notice? Edited from

Transcription

1 What do you notice? Edited from

2 How can a one brain region increase the likelihood of eliciting a spike in another brain region?

3 Communication through increases in firing rate Neuron Group 1 sends projections to Neuron Group 2 Neuron Group 1 Neuron Group 2 Neuron Group 2 integrates the inputs it receives from Neuron Group 1 over a time window. If Neuron Group 1 increases the number of action potentials it exhibits in that time window, it increases its ability to elicit spiking activity in Neuron Group 2. This is a this dominant model for communication between neurons because many neurons modulate their firing rate in ways that correlate with meaningful stimulus or cognitive parameters.

4 Is Neuron Group 2 affected by firing rate changes in Neuron Group 1? Neuron Group 1 Neuron Group 2 Tsodyks and Markram, PNAS, 1997 Increases in firing rate in presynaptic neurons elicits smaller EPSPs in postsynaptic neurons. The resulting influence on the membrane potential of the postsynaptic cell plateaus, limiting the presynaptic neuron s ability to alter activity in the postsynaptic cell via changes in firing rate.

5 Communication through increases in synchronous Neuron Group 1 sends projections to Neuron Group 2 Neuron 1 Neuron 2 Neuron Group 2 receives synchronized inputs from Neuron Group 1 over a time window. If Neuron Group 1 sends bursts of inputs within a short time window, it increases its ability to elicit spiking activity in Neuron Group 2. This is something that can be achieved in neurons engaged in gamma oscillatory networks.

6 How well do postsynaptic neurons respond to sudden increases in input? Neuron 1 Neuron 2 Dramatic increases in the membrane potential (fast changes, higher slope) decreases the voltage threshold for eliciting action potentials. This suggests that neurons are sensitive to a high density of input within a short time period.

7 Communication through neuronal coherence Neuron Groups 1 and 3 send projections to Neuron Group 2 Neuron Group 1 Neuron Group 2 Neuron Group 3 Neuron Group 2 receives synchronized inputs from Neuron Group 1 during excitability peaks, but Neuron Group 3 exhibits excitability when Neuron Group 2 is not receptive. Only Neuron Group 1 is able to effectively communicate with Neuron Group 2, and communication from Neuron Group 3 is prohibited.

8 Neuron Group 1 Is there evidence that there are non-optimal times for postsynaptic neurons to receive input? Neuron Group 2 Neuron Group 3 Action potentials can only be elicited in a postsynaptic neuron receiving alternating current injection when a presynaptic neuron is stimulated within a short temporal window. This suggests that communication between neurons may need to be temporally coordinated.

9 Driving fast-spiking interneurons in barrel cortex induces a gamma rhythm and gates sensory responses Schematic of the experiment: Responses of a RS cell to single WS: Average: Light = optogenetic stimulation of FS cells, WS = whisker stimulation Schematic model of gating sensory responses by gamma oscillations: Cardin et al., Nature, 2009

10 How can a one brain region increase the likelihood of eliciting a spike in another brain region?