# Brian 1 Hears bridge¶

The “Brian Hears” library is being rewritten for Brian 2 in a more flexible way to allow it to work on multiple devices. Until this work is complete, it is possible to run the version of Brian Hears from Brian 1.x using the “bridge”. To make this work, you must have a copy of Brian 1 installed (preferably the latest version), and import Brian Hears using:

from brian2.hears import *


Many scripts will run without any changes, but there are a few caveats to be aware of. Mostly, the problems are due to the fact that the units system in Brian 2 is not 100% compatible with the units system of Brian 1.

FilterbankGroup now follows the rules for NeuronGroup in Brian 2, which means some changes may be necessary to match the syntax of Brian 2, for example, the following would work in Brian 1 Hears:

# Leaky integrate-and-fire model with noise and refractoriness
eqs = '''
dv/dt = (I-v)/(1*ms)+0.2*xi*(2/(1*ms))**.5 : 1
I : 1
'''
anf = FilterbankGroup(ihc, 'I', eqs, reset=0, threshold=1, refractory=5*ms)


However, in Brian 2 Hears you would need to do:

# Leaky integrate-and-fire model with noise and refractoriness
eqs = '''
dv/dt = (I-v)/(1*ms)+0.2*xi*(2/(1*ms))**.5 : 1 (unless refractory)
I : 1
'''
anf = FilterbankGroup(ihc, 'I', eqs, reset='v=0', threshold='v>1', refractory=5*ms)


Slicing sounds no longer works. Previously you could do, e.g. sound[:20*ms] but with Brian 2 you would need to do sound.slice(0*ms, 20*ms).

In addition, some functions may not work correctly with Brian 2 units. In most circumstances, Brian 2 units can be used interchangeably with Brian 1 units in the bridge, but in some cases it may be necessary to convert units from one format to another, and to do that you can use the functions convert_unit_b1_to_b2 and convert_unit_b2_to_b1.