Brain Inspired Algorithms
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Overview
After working for nearly a decade in sub-areas of artificial intelligence (robotics, temporal reasoning, constraint satisfaction and satisfiability), by 2006 I started to question the underlying idea that general artificial intelligence could arise by integrated all the sub-areas of AI into a unified Heath Robinson-type hybrid system. For the more neuroscience discovered about the one structure that we know exhibits general intelligence (i.e. the human neocortex) the less it looked like it implemented a hybrid set of independent specialised systems. Instead the neocortex showed itself to possess a remarkably uniform structure that seems to be performing the same basic function across its entire surface. And what has emerged from twenty-first century neuroscience is the idea that the neocortex is primarily engaged in making predictions about its own inputs and outputs – which has come to be known as the theory of predictive processing.
Taking heed of these developments, I formed the Cognitive Computing Unit at Griffith University as a centre of research where we could explore the computational implementation of predictive processsing and the following papers present the outcomes of this research. The primary focus has been the investigation and development of a particular implementation of predictive processing known as Hierarchical Temporal Memory, first proposed by Jeff Hawkins in the mid-2000s. This led to my own proposal of Hierarchical Temporal Intentionality (see ASSC 2014 below) which brings together the idea of predictive processing with the discoveries and insights of twentieth century phenomenology – connecting the brain science with our immediate experience of being conscious. This synthesis of science and consciousness is also a central theme in my new book The Questioning of Intelligence (see the Books page for more details, and The Being of Form below).
As with my work in constraint satisfaction, much of the actual coding and experimental evaluation reported in the papers below was performed by the PhD and Honours students I was supervising. And, as is usual, you can tell who had the greatest input into each paper by the order in which the author’s names are listed. Of these authors, I have been the primary PhD supervisor for Benjamin Cowley, Adam Kneller and Linda Main, and primary Honours supervisor for Andrew Srbic (for more detail on the pre-2010 papers co-authored with Jolon Faichney see the Handwriting Recognition page).
2021
Thornton, J. (2021). The Being of Form. In: The Questoning of Intelligence: A phenomenological exploration of what it means to be intelligent. FUBText: Brighton, pp. 320-350, ISBN 978-1-8384787-0-4
Excerpt: From this we can see that our scientific models of atomic being are not determined or limited by the dimensionalities of our perceptual systems. These dimensionalities only limit the extent to which we can picture or imagine what our scientific models ‘look like’. But if we consider the meaning of these models more fundamentally, we can see that they are still based on a quite specific conception of being—namely an idea of enduring mathematical form. This too is a human idea that is ‘built in’ to our perceptual systems. For, according to our latest scientific theories, these systems have evolved to detect invariance in the streams of sensorimotor input and output, in order to form predictions of the future evolution of these information streams. What emerges from this process are our ideas of a world populated with determinate and identifiable things and events. These are the entities we project to be the causes of the streams of sensorimotor information that continuously activate our nervous systems. Here, in order for something in the world to ‘be’ or to ‘exist’ it must possess the kind of enduring mathematical form that enables us to predict the shape of our future. This is all to do with computational efficiency. If you were to attempt to predict what you will experience in the next moment purely on the basis of the state of excitation of all your sensorimotor nerve impulses in this moment, it would turn out to be impossible. There is just not enough information in the previous state to determine with any accuracy what will happen in the next state. For virtually nothing at this level is stable. It is the river in which you cannot step twice. What the brain is doing is forming connections between its inputs and outputs in such a way as to detect the presence of enduring or stable relationships. Once it has encoded the essential underlying relationships that exist in the sensorimotor streams that emerge from our interactions with a particular object—such as the table in front of me now—then instead of trying to predict how the visual field is going to change as I shift my gaze over the table by examining the immediate state of that visual field, it uses what it has stored from past experience with tables in general, and with this table in particular, to predict and project how the table will appear in the next moment. Of course the immediate state of my visual system informs this process, but it is the mathematical form of the table that is encoded in the brain that determines what I am predicting, both in terms of what I expect to perceive and how I expect to act.
2018
Cowley, B., Thornton, J. R., Main, L. & Sattar, A. (2018). Precision without Precisions: Handling uncertainty with a single predictive model. In: ALIFE 2018, Proceedings of the 2018 Conference on Artificial Life, Tokyo, Japan, MIT Press, pp. 129-136.
Abstract: The predictive processing theory of cognition and neural encoding dictates that hierarchical regions in the neocortex learn and encode predictive hypotheses of current and future stimuli. To better handle uncertainty these regions must also learn, infer, and encode the precision of stimuli. In this treatment we investigate the potential of handling uncertainty within a single learned predictive model. We exploit the rich predictive models formed by the learning of temporal sequences within a Hierarchical Temporal Memory (HTM) framework, a cortically inspired connectionist system of self-organizing predictive cells. We weight a cell’s feedforward response by the degree of its own temporal expectations of a response. We test this model on data that has been saturated with temporal or spatial noise, and show significant improvements over traditional HTM systems. In addition we perform an experiment based on the Posner cuing task and show that the system displays phenomena consistent with attention and biased competition. We conclude that the observed effects are similar to those of precision encoding.
2017
Cowley, B., Thornton, J. R., Main, L. & Sattar, A. (2017). Dynamic Thresholds for Self-Organizing Predictive Cells. In: ECAL 2017, Proceedings of the 14th European Conference on Artificial Life, Lyon, France, MIT Press, pp. 114-121.
Abstract: It has become increasingly popular to view the brain as a prediction machine. This view has informed a number of theories of brain function, the most prominent being predictive processing, where generative hypotheses are iteratively updated by error signals. In this treatment we take a lower-level approach by examining the hierarchical temporal memory framework, which views individual pyramidal cells as the primary predictive unit of a self-organizing networked sequence learning system. Within this computational framework, the cell behaviour is constrained by a number of parameters which are static and shared across all cells. To further increase the adaptability of the cells, we shift away from this paradigm by introducing the concept of dynamic thresholds. This allows for the activation threshold (the amount of activity on a distal dendrite needed to form a prediction) to be adjusted continuously and individually for each cell. As a metric we use the prior, or unconditional, probability of activity on the proximal dendrites. Our experiments show that using this metric for dynamic thresholds can improve the predictive capabilities of the system in a number of domains, including anomaly detection, where we achieve state-of-the-art results on the Numenta Anomaly Benchmark.
Cowley, B. & Thornton, J. R. (2017). Feedback Modulated Attention within a Predictive Framework. ACALCI 2017, Artificial Life and Computational Intelligence, 3rd Australasian Conference. Lecture Notes in Computer Science, 10142, 61-73. Springer, ISSN 0302-9743.
Abstract: Attention is both ubiquitous throughout and key to our cognitive experience. It has been shown to filter out mundane stimuli, while simultaneously communicating specific stimuli from the lowest levels of perception through to the highest levels of cognition. In this paper we present a connectionist system with mechanisms that produce both exogenous (bottom-up) and endogenous (top-down) attention. The foundational algorithm of our system is the Temporal Pooler (TP), a neocortically inspired algorithm that learns and predicts temporal sequences. We make a number of modications to the Temporal Pooler and place it in a framework which is inspired by predictive coding. We use a novel technique in which feedback connections elicit endogenous attention by disrupting the learned representations of attended sequences. Our experiments show that this approach successfully filters attended stimuli and suppresses unattended stimuli.
Main, L. & Thornton, J. R. (2017). Stable Sparse Encoding for Predictive Processing. In: SSCI 2017, Proceedings of the 2017 IEEE Symposium Series on Computational Intelligence, Hawaii, USA, IEEE, pp. 1-8.
Abstract: Hierarchical Predictive Coding systems that have adopted prediction as their primary goal, are heavily reliant on the stable sparse coding of sensory input. Furthermore, such systems will require their spatial coding function to be adaptive and able to reform to reflect changes within the environment. These properties of stability and adaptiveness should emerge naturally from the spatial coding system and not be reliant on additional control mechanisms. Hierarchical Temporal Memory is a cortically inspired model that encapsulates both sparse coding and temporal processing functions. We present an investigation into the stability and adaptiveness of three alternative versions of the spatial pooling function. Our results show that two of these SP algorithms are able to form stable sparse distributed representations of audio input, while still remaining adaptive to changes within the input data.
2015
Kneller, A. & Thornton, J. R. (2015). Distal Dendrite Feedback in Hierarchical Temporal Memory. In: IJCNN 2015, Proceedings of the 2015 International Joint Conference on Neural Networks, Killarney, Ireland, IEEE, pp. 385-392.
Abstract: Recent theories have proposed that the unifying principle of brain function is the minimisation of variational free energy and that this is best achieved using a hierarchical predictive coding (HPC) framework. Hierarchical Temporal Memory (HTM) is a model of neocortical function that fits within the free energy framework but does not implement predictive coding. Recent work has attempted to integrate predictive coding and hierarchical message passing into the existing suite of HTM Cortical Learning Algorithms (CLA) producing a PC-CLA hybrid. In this paper we examine for the first time how such hierarchical message passing can be implemented in a pure HTM framework using distal dendrite structures that are already implemented in the CLA temporal pooler. We show this approach outperforms the more simplistic proximal dendrite structures used in the PCCLA hybrid and also that the new CLA hierarchy is effective for anomaly detection and image reconstruction problems that are beyond the reach of the existing single-level CLA framework.
Main, L. & Thornton, J. R. (2015). A Cortically Inspired Model for Bioacoustics Recognition. ICONIP 2015: 22nd International Conference on Neural Information Processing, Istanbul, Turkey, Lecture Notes in Computer Science, 9492, 348-355, Springer, ISSN 0302-9743.
Abstract: Wavelet transforms have shown superior performance in bioacoustic recognition tasks compared to the more commonly used Mel-Frequency Cepstral Coecients, and offer the ability to more closely model the frequency response behaviour of the basilar membrane within the cochlea. In this paper we evaluate a gammatone wavelet as a preprocessor for the Hierarchical Temporal Memory (HTM) model of the neocortex, as part of the broader development of a biologically motivated approach to sound recognition. Specifically, we implement a gammatone/equivalent rectangular bandwidth wavelet transform and apply it, in conjunction with the HTM’s spatial pooler, to recognise frog calls, bird songs and insect sounds. We demonstrate the improved performance of wavelets for feature detection and the potential viability of using HTM for bioacoustic recognition. Our classication accuracy of 99.5% in detecting insect sounds and 96.3% in detecting frog calls are signicant improvements on results previously published for the same datasets.
Thornton, J. R. (2015). The Transcendence of Computational Intelligence. PhD Confirmation Document, 141 pp. Completed under the supervision of John Mandalios, School of Humanities, Griffith University.
Following on from the introduction, Chapters 2-5 are all intended for inclusion in the final thesis. They cover Part One described above, with Chapter 2 providing a method of access, and Chapters 3-5 examining the work of Descartes, Schopenhauer and Husserl in relation to the material presented in Chapter 2. Finally, the appendices present two conference papers and one workshop paper that I have written and presented during my candidature. These papers cover various aspects of the questions I intend to address in Parts Two and Three, including the relevance of Heidegger to contemporary cognitive neuroscience (Appendix A), whether the activity of the human brain is causally closed under laws that determine the local low-level functioning of neural populations (Appendix B) and how contemporary models of neocortical functioning can be mapped onto Husserl’s phenomenological account of temporal consciousness (Appendix C).
2014
Cowley, B., Kneller, A. & Thornton, J. R. (2014). Cortically-Inspired Overcomplete Feature Learning for Colour Images. PRICAI 2014: Trends in Artificial Intelligence, 13th Pacific Rim International Conference on Artificial Intelligence. Lecture Notes in Computer Science, 8862, 720-732, Springer, ISSN 0302-9743.
Abstract: The Hierarchical Temporal Memory (HTM) framework is a deep learning system inspired by the functioning of the human neocortex. In this paper we investigate the feasibility of this framework by evaluating the performance of one component, the spatial pooler. Using a recently developed implementation, the augmented spatial pooler (ASP), as a single layer feature detector, we test its performance using a standard image classification pipeline. The main contributions of the paper are the implementation and evaluation of modications to ASP that enable it to form overcomplete representations of the input and to form connections with multiple data channels. Our results show that these modications signicantly improve the utility of ASP, making its performance competitive with more traditional feature detectors such as sparse restricted Boltzmann machines and sparse auto-encoders.
Thornton, J. R. (2014). Hierarchical Temporal Intentionality. Abstract in: ASSC 18: Handbook of the 18th Conference of the Association for the Scientific Study of Consciousness, Brisbane, Australia, University of Queensland, pp. 41-42.
Abstract: In recent years, a more unified understanding of the functioning of the neocortex has emerged. This understanding sees the neocortex as a hierarchically structured Bayesian prediction machine that perceives and acts according to a delicate interaction between direct inputs from the body and environment, and feedback within the brain concerning what it expects those inputs to be. This hierarchical predictive coding model provides an elegant account of how attention, perception, cognition and action can be understood as different aspects of a single process that aims to minimise prediction errors. Nevertheless, predictive coding models are not immediately concerned with predicting the future, but rather with predicting what is to happen now. As such, the predictive coding paradigm leaves the temporal horizons of experience unexplained. These horizons were first clearly identified in Husserl’s investigations of the unified tripartite structure of temporal consciousness. Several recent attempts have been made to explain how such a tripartite structure could be realised within current understandings of neocortical processing, but, as yet, none have been convincing. In this paper I introduce Jeff Hawkins’ model of neocortical processing that extends hierarchical predictive coding by proposing that the entire neocortex is engaged in sequence learning. This hierarchical temporal memory (HTM) model provides a coherent mapping between processes occurring in the brain and the structures of temporal consciousness. The paper also provides a phenomenological examination and reinterpretation of the meaning of the HTM model. This re-interpretation takes both consciousness and neocortical functioning to be fundamentally structured in terms of intentionality.
2013
Thornton, J. R. & Srbic, A. (2013). Spatial Pooling for Greyscale Images. International Journal of Machine Learning and Cybernetics. 4(3), 207-216, Springer, ISSN 1868-8071.
Abstract: It is a widely held view in contemporary computational neuroscience that the brain responds to sensory input by producing sparse distributed representations. In this paper we investigate a brain-inspired spatial pooling algorithm that produces sparse distributed representations of spatial images by modelling the formation of proximal dendrites associated with neocortical minicolumns. In this approach, distributed representations are formed out of a competitive process of inter-column inhibition and subsequent learning. Specifically, we evaluate the performance of a recently proposed binary spatial pooling algorithm on a well-known benchmark of greyscale natural images. In the process, we augment the algorithm to handle greyscale images, and to produce better quality encodings of binary images. We also show that the augmented algorithm produces superior population and lifetime kurtosis measures in comparison to a number of well-known coding schemes and explain how the augmented coding scheme can be used to produce high-delity reconstructions of greyscale input.
2012
Thornton, J. R., Main L. & Srbic, A. (2012). Fixed Frame Temporal Pooling. AI 2012: 25th Australasian Joint Conference on Artificial Intelligence, Lecture Notes in Computer Science, 7691, 707-718, Springer, ISSN 0302-9743.
Abstract: It is a widely held view in contemporary computational neuroscience that the brain responds to sensory input by producing sparse distributed representations. In this paper we investigate a brain-inspired spatial pooling algorithm that produces sparse distributed representations of spatial images by modelling the formation of proximal dendrites associated with neocortical minicolumns. In this approach, distributed representations are formed out of a competitive process of inter-column inhibition and subsequent learning. Specifically, we evaluate the performance of a recently proposed binary spatial pooling algorithm on a well-known benchmark of greyscale natural images. In the process, we augment the algorithm to handle greyscale images, and to produce better quality encodings of binary images. We also show that the augmented algorithm produces superior population and lifetime kurtosis measures in comparison to a number of well-known coding schemes and explain how the augmented coding scheme can be used to produce high-delity reconstructions of greyscale input.
2011
Thornton, J. R., Srbic, A., Main, L. & Chitsaz, M. (2011). Augmented Spatial Pooling. AI 2011: 24th Australasian Joint Conference on Artificial Intelligence, Lecture Notes in Computer Science. 7106, 261-270, Springer, ISSN 0302-9743.
Abstract: Applications of unsupervised learning techniques to action recognition have proved highly competitive in comparison to supervised and hand-crafted approaches, despite not being designed to handle image processing problems. Many of these techniques are either based on biological models of cognition or have responses that correlate to those observed in biological systems. In this study we apply (for the first time) an adaptation of the latest hierarchical temporal memory (HTM) cortical learning algorithms (CLAs) to the problem of action recognition. These HTM algorithms are both unsupervised and represent one of the most complete high-level syntheses available of the current neuroscientific understanding of the functioning of neocortex.
Specifically, we extend the latest HTM work on augmented spatial pooling, to produce a fixed frame temporal pooler (FFTP). This pooler is evaluated on the well-known KTH action recognition data set and in comparison with the best performing unsupervised learning algorithm for bag-of-features classification in the area: independent subspace analysis (ISA). Our results show FFTP comes within 2% of ISA’s performance and outperforms other comparable techniques on this data set. We take these results to be promising, given the preliminary nature of the research and that the FFTP algorithm is only a partial implementation of the proposed HTM architecture.
2009
Thornton, J. R., Faichney, J., Blumenstein, M., Nguyen, V. & Hine, T. (2009). Offline Cursive Character Recognition: A state-of-the-art comparison. In: IGS 2009: Proceedings of the 14th Conference of the International Graphonomics Society, Dijon, France, pp. 148-151.
Abstract: Recent research has demonstrated the superiority of SVM-based approaches for offline cursive character recognition. In particular, Camastra’s 2007 study showed SVM to be better than alternative LVQ and MLP approaches on the large C-Cube data set. Subsequent work has applied hierarchical vector quantization (HVQ) with temporal pooling to the same data set, improving on LVQ and MLP but still not reaching SVM recognition rates.
In the current paper, we revisit Camastra’s SVM study in order to explore the effects of using an alternative modified direction feature (MDF) vector representation, and to compare the performance of a RBF-based approach against both SVM and HVQ. Our results show that SVMs still have the better performance, but that much depends on the feature sets employed. Surprisingly, the use of more sophisticated MDF feature vectors produced the poorest results on this data set despite their success on signature verification problems.
2008
Thornton, J. R., Faichney, J., Blumenstein, M. & Hine, T. (2008). Character Recognition using Hierarchical Vector Quantization and Temporal Pooling. AI 2008: 21st Australasian Joint Conference on Artificial Intelligence. Lecture Notes in Computer Science, 5360, 562-572, Springer, ISSN 0302-9743.
Abstract: In recent years, there has been a cross-fertilization of ideas between computational neuroscience models of the operation of the neocortex and artificial intelligence models of machine learning. Much of this work has focussed on the mammalian visual cortex, treating it as a hierarchically-structured pattern recognition machine that exploits statistical regularities in retinal input. It has further been proposed that the neocortex represents sensory information probabilistically, using some form of Bayesian inference to disambiguate noisy data.
In the current paper, we focus on a particular model of the neocortex developed by Hawkins, known as hierarchical temporal memory (HTM). Our aim is to evaluate an important and recently implemented aspect of this model, namely its ability to represent temporal sequences of input within a hierarchically structured vector quantization algorithm. We test this temporal pooling feature of HTM on a benchmark of cursive hand-writing recognition problems and compare it to a current state-of-the-art support vector machine implementation. We also examine whether two preprocessing techniques can enhance the temporal pooling algorithm’s performance. Our results show that a relatively simple temporal pooling approach can produce recognition rates that approach the current state-of-the-art without the need for extensive tuning of parameters. We also show that temporal pooling performance is surprisingly unaffected by the use of preprocessing techniques.
2006
Thornton, J. R., Gustafsson, T., Blumenstein, M. & Hine, T. (2006). Robust Character Recognition using a Hierarchical Bayesian Network. AI 2006: 19th Australian Joint Conference on Artificial Intelligence. Lecture Notes in Computer Science, 4304, 1259-1264, Springer, ISSN 0302-9743.
Abstract: There is increasing evidence to suggest that the neocortex of the mammalian brain does not consist of a collection of specialised and dedicated cortical architectures, but instead possesses a fairly uniform, hierarchically organised structure. As Mountcastle has observed [1], this uniformity implies that the same general computational processes are performed across the entire neocortex, even though different regions are known to play different functional roles. Building on this evidence, Hawkins has proposed a top-down model of neocortical operation [2], taking it to be a kind of pattern recognition machine, storing invariant representations of neural input sequences in hierarchical memory structures that both predict sensory input and control behaviour. The first partial proof of concept of Hawkins’ model was recently developed using a hierarchically organised Bayesian network that was tested on a simple pattern recognition problem [3]. In the current study we extend Hawkins’ work by comparing the performance of a backpropagation neural network with our own implementation of a hierarchical Bayesian network in the well-studied domain of character recognition. The results show that even a simplistic implementation of Hawkins’ model can produce recognition rates that exceed a standard neural network approach. Such results create a strong case for the further investigation and development of Hawkins’ neocortically-inspired approach to building intelligent systems.