NuPIC Glossary



What follows is a lexicon of terms used in not only NuPIC but HTM. It includes jargon used within the NuPIC code projects as well as theory jargon.

Numenta (NTA) - California-based machine learning research and development company

Online Prediction Framework (OPF) - A construct used in machine learning for dynamic data

NuPIC - Numenta Platform for Intelligent Computing

Cap’n Proto - Serialization and deserialization library

SWIG - Simplified Wrapperand Interface Generator, used for working C/C++ into Python and other high level languages

KNN - K-Nearest Neighbor, an algorithm used in supervised machine learning

SVM - Support Vector Machine, a construct used in supervised machine learning

Cortical Learning Algorithm (CLA) - Original name for the implementation of HTM as an algorithm

Apache Portable Runtime Library (APR) - A library which is used to help interoperability and platform-specific implementations of software

Spatial pooler (SP) - HTM algorithm which is responsible for updating columns in a region and outputting the list of active columns

Temporal memory ( TM ) - HTM algorithm which is responsible for updating cells in a region and processing predictions

Temporal pooler (TP) - The region or node which is responsible for recognizing temporal patterns in the temporal memory activation. Historically refers to the process which is now the temporal memory ™.

Hierarchical Temporal Memory (HTM) - Theory of intelligence based on similarities in neocortical structures, developed by Jeff Hawkins

Region - A logical collection of columns and cells which share an input and connect through distal dendrite segments between cells

Node - A region or class which receives data and performs some operation, and optionally sends the data to other nodes

Sensor - A region or node which is responsible for interfacing between raw data and other nodes, such as encoders

Effector - A region or node which only serves to write input data to a file

Encoder - A region or node which implements an algorithm for turning data (e.g. integers, dates, etc) into a sparse distributed representation (SDR) in a consistent manner

Pass-through node - A node whose purpose is to simply pass its input to the next region.

Zeta1Node - Deprecated term for the combination of a spatial pooler and temporal memory (previously referred to as temporal pooler) nodes.

Classifier - A machine learning component which classifies data into one of a number of categories (or “buckets”)

Category - A term used in machine learning which refers to one of a number of “classes” or categories that a data input can belong to. Also referred to as a “bucket”.

Bucket - See Category

Cell - A learning component in HTM which connects to other cells in the region through distal dendrite segments and recognizes patterns in activity leading up to its own activation

Column - A collection of cells which connects to an input SDR through a proximal dendrite segment and recognizes a particular spatial pattern

Column center - A location in the input space where a column’s receptive field is centered; creates a spatial mapping of columns to the input space

Dendrite - A collection of synapses representing a population of connected neurons. Each dendrite might be said to represent an SDR space that could be computed separately. There are different areas of dendrites around a pyramidal neuron, defined below.

All dendrites represent a limb on their dendritic tree.

  • Proximal Dendrite - close to the cell body, typically before the first branch in the dendritic tree
  • Distal Dendrite - far from the cell body, after the first branch in the dendritic tree
  • Apical Dendrite - far reaching dendrites that reach upward to receive feedback from cells in a higher layer or further up the hierarchy

Dendritic Tree - One dendrite extending from the soma and all subsequent branches and extensions combined are sometimes referred to as a dendritic tree.

Segment or “dendritic segment”- see dendrite

Synapse - (In HTM) An object which represents the permanence of a connection of a dendrite in a segment

Permanence - The real valued strength of a synapse, between 0.0 and 1.0

Boost - An auxiliary parameter given to help give unused columns a better chance of becoming active; boost is a number >= 1 which is multiplied with the overlap score for a column

Activation Threshold - The minimum overlap score a column must have to be considered for activity

Global inference - A parameter of an HTM region; when true, all columns in the entire region are compared and the top N columns are chosen as active for the given input

Receptive field - The maximum range from the column center in the input space that a given column can possibly connect to

Feedback - The transfer of data from regions higher in a hierarchy to those below (not yet implemented in HTM)

Feed-forward activity - Also referred to as bottom up activity, the transfer of data from regions lower in a hierarchy to those above

Bottom-up activity - See Feed-forward activity

CMake - A program used to generate Makefiles for projects

GTest - Google’s C++ test framework

YAML - YAML Ain’t Markup Language, a JSON-based human-readable file format

Network - A collection of nodes through which data passes

Network API - Implementation of algorithms, sensors, effectors, etc in a network structure

Link - A connection between two nodes in a network

Uniform link -

Graded link -

Sparse link -

Splitting map -

OPF API - Online Prediction Framework API, one of three APIs used in HTM which provides swarming and online learning

Model -

Metric -

Client - The end-user and/or his/her machine, in the context of networking. A client accesses data through a server.

Algorithms API - One of three APIs used in HTM which provides a simple interface to the spatial pooler and temporal memory algorithms

Sparse Distributed Representation (SDR) - A data structure with a large number of bits, only a fraction of which are active at a given time

Graph - A collection of interconnected nodes; see network

Directed graph - A graph in which the connections between nodes are directional (one is an output and the other is an input); examples include flow-charts, internet networks

Directed acyclic graph - A directed graph which contains no closed loops


I just majorly changed the definitions of dendrites and segments. I need someone to review for accuracy please. You can review changes by clicking on the edit button at the top right of the wiki: