Dynamic Modulation of Neural Bandwidth

This page describes how the common input model can be used to infer the bandwidth of a model neurone under large scale synaptic input.

Definition and measurement of neural bandwidth

Common input model configuration: Two identical model motoneurones, with extensive dendritic tree (12 dendrites, 248200mm2), and a total synaptic input of 32,000 EPSPs/second to each cell. A percentage of this synaptic input is shared between the two cells, this is the subset of the synaptic inputs for which the bandwidth is to be estimated.

Bandwidth for Uncorrelated Synaptic Input
Correlation analysis of the output discharge of the two cell model with 50 % common synaptic inputs. Each cell has 1000 inputs firing randomly at 32 spikes/sec, they share 16,000 EPSPs/sec.

(a) The two cells demonstrate a tendency for synchronous discharges - due to the common input. (b) The range of frequencies involved is up to 50 Hz.

Thus the bandwidth for this configuration, which reflects the ability of 50% of the total synaptic input to modulate the output discharge, is 50 Hz.

The strength of correlation between the two outputs (and thus the neural bandwidth) varies systematically with the percentage of common input. With 10% common input there is no significant coherence between the outputs (bandwidth is zero). With 80% common input significant coherence is present to frequencies in excess of 200 Hz (bandwidth exceeds 200 Hz); the peak coherence is around 0.15. Bandwidth for Correlated Synaptic Input
Altering the correlation structure, without altering the firing rates, or numbers of inputs, has a dramatic impact on neural bandwidth.
Coherence between the output discharges of the two cell model with 10 % common synaptic inputs (3200 EPSPs/sec), provided by:
(a) One hundred broad band inputs (32 spikes/sec; c.o.v = 1.0) which are weakly correlated over a broad range of frequencies. 
(b) Two sets of periodically firing weakly correlated inputs (160 inputs at 10 spikes/sec; 64 inputs at 25 spikes/sec) which are correlated at their mean firing rate.

Inputs are distributed uniformly over the dendritic tree.


Dynamic Modulation of Neural Bandwidth.

Further details
For further details see the following article

Halliday, D.M. (2000). Temporal correlation of large scale synaptic input is a major determinant of neuronal bandwidth, Neural Computation, 12, 693-707.     PDF is available in the publications page.     Abstract is available here.
If you require further details please contact David Halliday.

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Last Modified 09 July 2002