Hi Raf, Welcome! Please do not respond to this, I'm just putting in a "time filler" until someone more neurobiologically knowledgable answers this later on today, but "A" is in fact being modeled by NuPIC, as often is stated in these circles that the synapses on distal dendrites act as "proximity detectors" - and we model this via a summation of synapse "permanence" values. In addition there is some portion of organic necessity not being abstracted in the software as some of these concepts were deemed to not have a significant enough impact on the overall process (as you also stated). Spikes (some not all), to a certain extent (from explanations I have overheard on this mailing list) are one of those concepts that organic implementation requires yet do not have a significance with regard to maintaining the metaphor in software. Some Spikes are in fact being modeled as a summation instead of a continuous rate (I believe).
Much care (by leading edge neuro-scientific researchers at the Redwood Institute as well as Numenta researchers), has been taken to ascertain that portion of explicit biological translation which is necessary to implement the over-all algorithms, but as always (as I have observed), the community is open to theoretical examination of their assumptions in this regard. Cheers, David On Sat, Dec 5, 2015 at 6:04 AM, Raf <[email protected]> wrote: > Hi everybody. > > I've got a couple of questions for you. > > I'm a med student and I'm new to Nupic. > I'm very impressed by what Numenta is achieving and I do believe that your > work in the long run will be compared to the discovery of penicillin :) > > My project -for now- is to produce a model able to detect > neurological/psychiatric issues through a simple eeg waves recognition; I'm > an intern at the Neurosurgery dept. and my final goal would be to use > patterns recognition as an intraoperative tool to help surgeons distinguish > between healthy tissue and cancerous cells just with a continuous eeg/emg > data feed. > > In order to get familiar with the machine learning world, and not > disposing of good enough datasets, since a couple of years I use financial > data (notoriously difficult-impossible do predict) as a sandbox environment > to experiment with NNs. I had encouraging results. > > I'm still learning the python code behind nupic and I've two questions for > you. > > 1 - FIRST QUESTION > In the paper "Hierarchical Temporal Memory" (version 0.2.1, 2011), I read > that: "[...] The predominant view (especially in regards to the neo-cortex) > is that the rate of spikes is what matters. Therefore the output of a cell > can be viewed as a scalar value". I'm aware that transforming a biological > complex system such as the neocortex into an computer software necessarily > leads to simplifications. As we know from a biological point of view the > transmission of the signal is subject to numerous variables and I wonder > how their implementation could improve the software predictions. > The variables I'd like to focus on are: > -A) The propagation of the action potential along the membranes > follows an exponential loss distribution due to the resistances met along > the axons. For the HTM model (where the synapses express binary weights) > this could mean that the more distant two connected cells are, the weakest > their shared signal becomes (of course directly depending on "where" the > dendrite segments are from their starting point - this would probably > require the introduction of the physical concept of space in HTM). > -B) The signal propagation speed is directly proportional to the > axon's diameter carrying it; this appears to be valid both in unmyelinated > and myelinated axons (though representing a more obvious phenomenon in the > latter type). This could have a huge impact for HTM: if bigger axons (= > weight+) burst temporally before other smaller ones towards the same target > dendrite, they can also inhibit temporarily that targeted cell (causing a > later refractory period) therefore filtering the signal. > -C) Receptors, neurotransmitters, electrical and chemical synapses, > EPSP (excitatory postsynaptic potential) and IPSP (inhibitory postsynaptic > potential) . This is an enormous chapter. Current NNs systems and, if my > understanding is correct, also Nupic treat synapses like if they were all > electrical synapses. In reality, according to the current consesus, the > mammal brain uses electrical synapses mostly to "synchronize" vast areas of > the neocortex (I'm deliberately omitting other findings because are not > relevant to my point). Although the electrical synapses demonstrates > various advantage when compared to their chemical equivalents (speed, > resistance, fatigue, etc.), it appears that the complexity and the fine > filtering/modulation of the signals inside the PFC is due to the presence > of numerous other elements present in chemical synapses: neurotransmitters > (such as acetylcholine, dopamine, gaba, norepinephrine...); pre-synaptic, > synaptic gap and post-synaptic features; different receptors; etc. Each of > these elements can strongly influence the signal and the overall "learning" > process. For example: although an axon "weight" is big and it is bursting > copiously the above mentioned elements can suppress its signal. > > My first question is: are the first two points (A and C) implemented in > Nupic? Do you reckon that it could be useful to increase the complexity of > Nupic also implementing the chemical synapses "class" with the elements > described in point C? > > > 2 - SECOND QUESTION > I'm trying to run a couple of models. This is an extract from a OPF I > created through swarming. > > 'model': 'CLA', > 'modelParams': {'anomalyParams': {u'anomalyCacheRecords': None, > u'autoDetectThreshold': None, > u'autoDetectWaitRecords': None}, > 'clParams': {'alpha': 0.06173462582232023, > 'clVerbosity': 0, > 'regionName': 'CLAClassifierRegion', > 'steps': '0'}, > 'inferenceType': 'NontemporalClassification', > 'sensorParams': {'encoders': {u'DATE_dayOfWeek': None, > u'DATE_timeOfDay': > {'fieldname': 'DATE', > 'name': > 'DATE', > > 'timeOfDay': (21, > > 2.2537623685060675), > 'type': > 'DateEncoder'}, > u'DATE_weekend': None, > '_classifierInput': > {'classifierOnly': True, > > 'clipInput': True, > > 'fieldname': 'VO', > > 'maxval': 2.0, > > 'minval': 0.0, > 'n': > 449, > > 'name': '_classifierInput', > > 'type': 'ScalarEncoder', > 'w': > 21}, > u'o10N_A': None, > u'o11N_A': None, > u'o12N_A': None, > u'o13N_A': None, > u'o14N_A': None, > u'o15N_A': None, > u'o1N_A': None, > u'o1N_B': None, > u'o2N_A': None, > u'o2N_B': None, > u'o3N_A': None, > u'o3N_B': None, > u'o4N_A': None, > u'o4N_B': None, > u'o5N_A': None, > u'o5N_B': None, > u'o6N_A': None, > u'o6N_B': None, > u'o7N_A': None, > u'o7N_B': None, > u'o8N_A': None, > u'o8N_B': None, > u'o9N_A': None, > u'o9N_B': None}, > 'sensorAutoReset': None, > 'verbosity': 0}, > 'spEnable': False, > 'spParams': {'columnCount': 2048, > 'globalInhibition': 1, > 'inputWidth': 0, > 'maxBoost': 2.0, > 'numActiveColumnsPerInhArea': 40, > 'potentialPct': 0.8, > 'seed': 1956, > 'spVerbosity': 0, > 'spatialImp': 'cpp', > 'synPermActiveInc': 0.05, > 'synPermConnected': 0.1, > 'synPermInactiveDec': 0.0005}, > 'tpEnable': False, > 'tpParams': {'activationThreshold': 16, > 'cellsPerColumn': 32, > 'columnCount': 2048, > 'globalDecay': 0.0, > 'initialPerm': 0.21, > 'inputWidth': 2048, > 'maxAge': 0, > 'maxSegmentsPerCell': 128, > 'maxSynapsesPerSegment': 32, > 'minThreshold': 12, > 'newSynapseCount': 20, > 'outputType': 'normal', > 'pamLength': 1, > 'permanenceDec': 0.1, > 'permanenceInc': 0.1, > 'seed': 1960, > 'temporalImp': 'cpp', > 'verbosity': 0}, > 'trainSPNetOnlyIfRequested': False}, > > If I understood correctly, all the inputs (from o1N_A to o15N_A) were > discarded by the swarming process. I've also run a larger swarm, but they > are still discarded. Unfortunately I'm sure that at least a good 60% of > them are relevant sensors. How can I improve the swarming? Am I doing > something wrong? (The sensors are outputs from thoracic low-res electrodes; > the predicted field is "VO" which represents the amount of spO2 present in > the blood stream at the moment - the idea is to predict the oxygen > saturation from the respiratory act). > > Thanks for your replies. Sorry for my english (I'm italian). > > Raf > > > -- > Raf > www.madraf.com/algotrading > reply to: [email protected] > skype: algotrading_madraf > > -- *With kind regards,* David Ray Java Solutions Architect *Cortical.io <http://cortical.io/>* Sponsor of: HTM.java <https://github.com/numenta/htm.java> [email protected] http://cortical.io
