MOTOR SYSTEMS · SECOND-YEAR MEDICINE
Movement
in the age of AI
From digital biomarkers
to virtual brains
Ali Mirzakhani Neuroprocessing · 30 minutes
Join the opening experimentScan or tap · use your own phoneExplanation
English
This lesson follows four connected questions about movement: how to measure it, how to monitor it, how to intervene, and how to model it. The route begins with a movement task you can try on your own device, then moves from digital movement measures toward virtual brains.
MEET YOUR PRESENTER

Ali
Mirzakhani
PhD Candidate in Neuroscience
MSc Biomedical Engineering
Tehran University of Medical Sciences
Neuroprocessing.org ↗From biomechanics
to neuroscience
- BScBiomedical Engineering
BiomechanicsGame-based wrist rehabilitation with a joystick, Arduino and Processing 3.
- MSc2020–2021
BiomechanicsCardiac tissue motion and deformation across a cardiac cycle, using Digital Volume Correlation and AI.
- PhDSince 2022
NeuroscienceMotor skill learning in animal studies on rats.
YOUR FIRST DIGITAL MOVEMENT MEASURE
How fast can you
stay accurate?
A tap becomes a number. What would make that number clinically useful?
Join the opening experimentScan or tap · use your own phoneSame distance. Three target sizes. How does precision change your movement?
Start when comfortable. The first hit anchors your position and is not timed.
Follow your selected instruction. Misses count; the timer keeps running. Size-block order is randomized. Keep the window and device orientation unchanged.
Your 18 measured movements will appear here.
Nothing is uploaded or saved.
Prediction: when the target shrinks but distance stays fixed, what might change?
What does this measure?
Each point is a successful target-to-target interval, including time spent correcting misses. The anchor click before each size block is excluded. Distance is fixed within this trial; target-size order is randomized. There are only six acquisitions per size.
Mouse, touchscreen, display size, input latency, practice, fatigue and browser timing affect the result. This is an educational demonstration of a speed–accuracy trade-off, not a clinical test or a diagnostic score. Keyboard walkthroughs are unmeasured. The last completed run is retained in memory for an optional strategy comparison; Reset or reload clears it. No result leaves this page.
The chart groups your actual intervals by target width; it does not fit a movement law from these few trials. Comparing strategies is exploratory: order, practice and fatigue are not controlled.
Background: Fitts, 1954.
Try the target-acquisition task in presentation mode: fixed distance, three target widths, six timed successful transfers per width. Inspect actual intervals and misses. The initial anchor is excluded; correction time remains in the measured interval. This is a classroom demonstration, not a clinical test.
A classroom movement measure, not a validated clinical biomarker. Actual results from this page only. Informal target-acquisition task; device and practice affect timing. Fitts · 1954 ↗
Explanation
English
This task keeps the target distance fixed and uses three target widths. Each width begins with an unmeasured anchor hit, followed by six timed successful transfers. A miss does not restart the interval, so the time spent correcting it remains in the measurement. Inspect your actual intervals and misses. Device and practice affect timing, and a short trial may not show the expected pattern. This is an informal classroom movement measure, not a validated clinical biomarker.
EXPLORE THE MEASUREMENT
What can AI measure
in a walk?
Make a movement
measurable
Reveal the body points. Move through time. Follow the ankle trajectory.
Explore the sequence to see how positions become a trajectory.
Original teaching illustration. No patient video or AI inference is running.
Digital movement measures need a defined purpose and validation. FDA: digitally derived measures ↗
Explanation
English
Reveal the body landmarks, move through the sequence and follow the ankle trajectory. Positions across time become a movement trajectory that can be inspected. This is an original synthetic teaching illustration. No patient video or AI inference runs here. A digital movement measure still needs a defined purpose and validation.
THE COMPUTATIONAL CHAIN
From pixels to
clinical information
Video
Images recorded under a repeatable protocol.
Body points
Pose models estimate visible landmarks.
Movement
Geometry and biomechanics turn coordinates into estimates.
Clinical meaning
Evaluate the measure for the intended population and use.
Finding a knee in an image is one step in the measurement process.
Uhlrich et al. · OpenCap · PLOS Computational Biology 2023 ↗
PUBLISHED MEASUREMENT-VALIDATION STUDIES
A biomechanics lab
in your pocket
Synchronized phone views
Computer vision meets musculoskeletal simulation.
Read the original study ↗Handheld phone
Model fitting evaluated in 1,021 clinical videos.
Explore the authors’ demonstration ↗Motion and dynamics are model estimates. Validate the intended use.
PBL: 1,021 counts videos, not patients. Peiffer et al. · npj Digital Medicine · 5 June 2026 ↗. Single-phone PBL is a separate study from the original OpenCap system.
CLINICIAN-SUPPORTING MONITORING
A clinic visit
is a snapshot
What happens
between visits?
Wrist-derived trends can complement examination of bradykinesia, tremor and dyskinesia.
Personal KinetiGraph: a defined measurement system. Wrist motion does not capture the entire body.
Repeated wearable observations
Conceptual timeline · no symptom values or patient data
PKG Gen2/GKC-2000: FDA K161717 · indications and device description ↗. Monitoring and autonomous diagnosis are different uses.
INTERPRETING A DIGITAL MEASURE
One measured change.
Several possible causes.
movement
A variable we can quantify.
Pain or fatigue
Musculoskeletal constraints
Neurological impairment
Medication and context
Measurement → interpretation → mechanism: each step needs evidence.
Conceptual clinical reasoning example. FDA: intended use and validation of digital measures ↗
SINGLE-PARTICIPANT FEASIBILITY STUDY
A digital bridge
from brain to spine
Cortical
recording
Implanted ECoG signals
Computational
decoder
Estimate intended movement
Spinal
stimulation
Adjust epidural stimulation
One participant · chronic incomplete cervical spinal cord injury
Prior stimulation and rehabilitation; improved control with the system.
Conceptual system diagram. Lorach et al. · Nature 2023 ↗. This study does not establish routine treatment or anatomical repair of the cord.
AN APPROVED CLINICAL INDICATION
Pair stimulation
with rehabilitation
practice↻Paired vagus
nerve stimulation
Vivistim · Paired VNS
A specific patient group
Chronic ischemic stroke with moderate to severe arm impairment.
Paired stimulation during rehabilitation. This example is neuromodulation; it does not require an AI claim.
FDA PMA P210007 · 27 August 2021 ↗ · Dawson et al. · pivotal trial · Lancet 2021 ↗
A FUTURE SCENARIO
What would better
movement care look like?
Repeatable
measurement
Clinician
interpretation
Testable
prediction
Evaluated
patient benefit
A personalized model needs a defined decision, independent validation and meaningful outcomes.
A digital twin is a predictive research ambition. A 3D avatar alone is not one.
Future scenario, not a validated clinical system. FDA: computational-model credibility and context of use ↗
ANIMAL LEARNING RESEARCH
Can a rat
learn to drive?
A new consequence.↗Open the official demonstration
Operate a vehicle
to reach food
Time, route, control actions and performance over practice.
Behavior alone does not localize the circuit that learned it.
Crawford et al. · Behavioural Brain Research 2020 ↗. Male rats; enriched housing improved learning performance. The lab’s films may show later demonstrations of the research programme.
DEEP LEARNING FOR BEHAVIORAL MEASUREMENT
From behavior
to testable patterns
x, y, confidenceWhat changes
with practice?
Route geometry
Movement variability
Interaction with the apparatus
Explore DeepLabCut ↗Conceptual workflow; no tracking output or animal dataset is fabricated here. Mathis et al. · Nature Neuroscience 2018 ↗. Check labels, occlusion and tracking error in the actual recording.
DORKENWALD ET AL. / NATURE 2024
Can we reconstruct
a brain?
One adult female fruit-fly brain.
A structural map opens new questions about function.
Dorkenwald et al. · Neuronal wiring diagram of an adult brain · Nature 634, 124–138 (2024). The synapse count describes the published reconstructed connectome, not every synapse in the tissue.
EXPLORE THE MODEL ARCHITECTURE
A virtual brain
inside a virtual body
Interactive explanatory diagram. No neural or physics simulation runs here. Eon’s technical account · March 2026 ↗. Existing brain/body models, sparse readout, engineered mappings and trained controllers all contribute.
PERSIAN JOURNAL CLUB · FREE FOR EVERYONE
From connectome
to behavior
Can we simulate a brain?
Read the map. Inspect the models.
Ask what the evidence supports.
Ali Mirzakhani · Vahid Hosseinkhani
with Neuroprocessing
Neuronal wiring diagram
of an adult brain
Dorkenwald et al.
Nature · 2024
Persian-language event · ۲۲ آذر ۱۴۰۵ · گروه علوم اعصاب و مطالعات اعتیاد، دانشکدهٔ فناوریهای نوین پزشکی. Meeting details are announced on the event page.
CONTINUE READING
The evidence
behind the story
Study populations, intended uses and limitations matter. Each lecture illustration is distinguished from published evidence. This reading list is outside the 30-minute class.