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Have you imagined a world that we could control things without moving our fingers? Will you fancy
playing video games or driving your cars just with your brain? I have to tell you that this fantasy is no
longer impossile with the help of Brain Machine Interface (BMI). In recent decades, as technology
advancing and social ethics system maturing, a heated debate has been triggered over the usage of
BMI. Some argues that current innovations are still not applicable for widely marketing products.
However, most engineers and neuroscientists are excited by technological progress that facilitates
brain mapping, the most sanguine of them comparing their growing ability to tremendous advances
that led to the unimaginable success of the BMI projects. Companies like NeuralLink and
Paradromics, as well as government agency have invested on the projects to test the possibilities
and work on the real world applications [1]. This articles briefly introduces one of the prevailing
technology in BMI: the application of Kalman filter in neural signal decoding, discussing its
advantages and potential improvements, and what makes it robust and powerful that could possibly
allows BMI to enhance our daily life.
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Application of Kalman Filter in Neural Signal Decoding 180D-FW-2023/Knowledge-Base-Wiki Wiki
Backgrounds in Neuroscience
Before we get to the real technique, a simple background in neuroscience is neccessary to unravel
you from the potential confusion in the world of jargons, since the mind, with our brain in general, is
our main subject of research. The main study theme of neuroscience is to link molecules to mind.
Human brain is a highly integrated network of approximately 100 billion individual nerve cells.
Therefore, to fully understand the mechanism behind the BMI devices, a brief understanding of how
neurons are organized into signaling pathways and how they communicated is necessary. We will
introduce how brain functions from three different levels: brain, neuron, and neural signal (action
potential). Further readings in related areas are also encouraged.
The Brain and Behavior
What does our brain look like? Surprisingly, it is complex and ordered at the same time. The central
nervous system (CNS) is bilateral and symmetrical. Studies on brain with modern imaging
techniques discovers that different regions on brain are specialized for different functions. As you
may have gussed, for BMI to decode human cognitive information, the most important part that we
would like to focus on is the cerebral cortex, where brain operations that are responsible for human
cognitive abilities occur. As shown in the graph, It consists of four anatomically distinct lobes with
different functionalities, including planning future actions, hearing, learning, vision, etc. With the
concept of functional engineering prevailing in neuroengineering, it is natural to focus on a specific
area on cerebral cortex to gather information of neuron activity. Therefore, to achieve fancy
operations like controlling the cursor with our mind, for example, we will mainly focus on motor
cortex in frontal lobe, which is responsible for planning future actions and the control of movement.
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A
Neurons
B
Application of Kalman Filter in Neural Signal Decoding 180D-FW-2023/Knowledge-Base-Wiki Wiki
Motor cortex
(Precentral gyrus)
Central sulcus
Frontal lobe
Lateral sulcus
Arcuate
fasciculus
Broca's
area
Vocalization region
of motor area
Parietal lobe
Temporal lobe
Somatic sensory
cortex (Postcentral
gyrus)
Primary auditory
cortex
Occipital
lobe
Angular gyrus
Wernicke's area
Visual
cortex
Figure 1-4 The major areas of the cerebral cortex are
shown in this lateral view of the of the left hemisphere.
A. Outline of the left hemisphere.
B. Areas involved in language. Wernicke's area processes the
auditory input for language and is important to the understand-
ing of speech. It lies near the primary auditory cortex and the
angular gyrus, which combines auditory input with information
from other senses. Broca's area controls the production of in-
telligible speech. It lies near the region of the motor area that
controls the mouth and tongue movements that form words.
Wernicke's area communicates with Broca's area by a bidirec-
tional pathway, part of which is made up of the arcuate fasci-
culus. (Adapted from Geschwind 1979.)
Source: Principles of Neural Science, Fourth Edition. Eric R. Kandel, James H. Schwartz, Thomas M.
Jessell [2]
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What is the basic unit of our brain and what makes it complex? We have to give credit to these
simple but powerful biological creatures: nerve cells (neurons). Just like VLSI transistors, even
though they have relatively basic morphology and architecture, approximately 10^11 neurons in the
brain can support long-ranged and intricate anatomical circuits, where the "complexity" arises from.
Neuron have four regions: cell body (soma), dendrites, axon, and presynaptic terminals. The main
component axon is what we should pay special attention to: it conveys signals (action potential) to
other neurons in long distance (0.1mm - 3m), while ensure the signals propagate without distortion
or failure and preserving its shape at very high speed (1 - 100m/s). Compared to transmission line in
our real life, the efficiency and accuracy of neural signal transmission are mind-blowing. Two
neurons can also communicate at the synapse chemically using neurotransmitters. Neurons, whose
structure diagram is attached below, are the most powerful building blocks of the most complicared
circuits in the world.
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Application of Kalman Filter in Neural Signal Decoding 180D-FW-2023/Knowledge-Base-Wiki Wiki
Excitatory
terminal fiber
of an axon
-Presynaptic cell-
.....Postsynaptic cells-
Inhibitory
terminal
fiber of
an axon
Axon
(initial
segment)
Node of Ranvier
Myelin sheath-
Neural Signal (Action Potential)
Axon
Apical dendrites
Cell body
-Nucleus
Basal
dendrites
Axon
hillock
Presynaptic
terminal
Synaptic
cleft
-Postsynaptic
dendrite
Act
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great va
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carry ir
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https://github.com/180D-FW-2023/Knowledge-Base-Wiki/wiki/Application-of-Kalman-Filter-in-Neural-Signal-Decoding
convey
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creates
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Source: Principles of Neural Science, Fourth Edition. Eric R. Kandel, James H. Schwartz, Thomas M.
Jessell [2]
Synapse
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