stdp_synapse_facetshw_hom – Synapse type for spike-timing dependent plasticity using homogeneous parameters¶
Description¶
stdp_facetshw_synapse
is a connector to create synapses with spike-timing
dependent plasticity (as defined in [1]).
This connector is a modified version of stdp_synapse
.
It includes constraints of the hardware developed in the FACETS (BrainScaleS)
project [2], [3], as for example, 4-bit weight resolution, sequential updates of groups
of synapses and reduced symmetric nearest-neighbor spike pairing scheme. For
details see [3].
The modified spike pairing scheme requires the calculation of tau_minus_
within this synapse and not at the neuron site via Kplus_
like in
stdp_synapse_hom
.
Warning
This synaptic plasticity rule does not take precise spike timing into account. When calculating the weight update, the precise spike time part of the timestamp is ignored.
The synapse IDs are assigned to each synapse in an ascending order (0,1,2, …) according their first presynaptic activity and is used to group synapses that are updated at once. It is possible to avoid activity dependent synapse ID assignments by manually setting the no_synapses and the synapse_id(s) before running the simulation. The weights will be discretized after the first presynaptic activity at a synapse.
Parameters¶
Common properties |
||
tau_plus |
ms |
Time constant of STDP window, causal branch |
tau_minus_stdp |
ms |
Time constant of STDP window, anti-causal branch |
Wmax |
real |
Maximum allowed weight |
no_synapses |
integer |
Total number of synapses |
synapses_per_driver |
integer |
Number of synapses updated at once |
driver_readout_time |
real |
Time for processing of one synapse row (synapse line driver) |
readout_cycle_duration |
real |
Duration between two subsequent updates of same synapse (synapse line driver) |
lookuptable_0 |
list of integers |
Three look-up tables (LUT) |
lookuptable_1 |
list of integers |
|
lookuptable_2 |
list of integers |
|
configbit_0 |
list of integers |
Configuration bits for evaluation
function. For details see code in
function |
configbit_1 |
list of integers |
|
reset_pattern |
list of integers |
Configuration bits for reset behavior. Two bits for each LUT (reset causal and acausal). In hardware only (all false; never reset) or (all true; always reset) is allowed. |
Common properties can only be set on the synapse model using
SetDefaults()
.
Individual properties |
||
a_causal |
real |
Causal and anti-causal spike pair accumulations |
a_acausal |
real |
|
a_thresh_th |
real |
Two thresholds used in evaluation function No common property, because variation of analog synapse circuitry can be applied here |
a_thresh_tl |
real |
|
synapse_id |
integer |
Synapse ID, used to assign synapses to groups (synapse drivers) |
Transmits¶
SpikeEvent