Portrait of Nickolaj Ajay Atchuthan

Nickolaj Ajay Atchuthan

EmailCV

PhD Fellow · Aalborg University

Pain neuroscience and machine learning

I’m a biomedical engineer doing basic research at the Center for Neuroplasticity and Pain. My PhD combines experimental surgery, intracranial recordings and machine learning to study nociception, the neural processing of potentially harmful stimuli, in anaesthetised pigs.

I’m currently finishing my PhD thesis. In my free time, I learn by building machine-learning tools around my hobbies, sometimes for myself or friends, sometimes just to try an idea.

Interactive ASCII rendering of an anatomical brain.

Selected work

Oct 2023–presentPhD project

At the surface and below: cortical responses to graded nerve stimulation

Center for Neuroplasticity and Pain · Aalborg University

My PhD asks how the primary somatosensory, anterior cingulate and prefrontal cortex, regions associated with sensory, affective and cognitive processing, respond to graded ulnar-nerve stimulation in anaesthetised pigs, and whether machine learning can read the stimulus intensity from those responses.

We developed an approach to ACC access and electrode targeting using surgical landmarks and real-time electrophysiological guidance. I performed the craniotomies, durotomies, and surface- and depth-electrode placement to record all three regions at once.

The thesis combines three studies: explainable deep learning of S1 responses; multiregion time–frequency physiology with mixed-effects models and threshold-free cluster enhancement; and a comparison of shallow-to-deep decoders under zero-shot cross-animal transfer and subject-specific fine-tuning.

  • PyTorch
  • Explainable ML
  • Transfer learning
  • Time-frequency analysis
  • Mixed-effects modelling
  • Permutation inference
  • Experimental neurosurgery

Research softwarePhD infrastructure

TDT-to-BIDS data pipeline

Center for Neuroplasticity and Pain · Aalborg University

Our Tucker-Davis Technologies (TDT) recordings did not fit neatly into the Python tools and data-sharing workflow I wanted to use. I started building a converter around the Brain Imaging Data Structure (BIDS), adapting its organisation to our animal recordings.

The pipeline reads TDT data into MNE-Python and keeps S1/PFC and ACC recordings in separate files to accommodate their different sampling rates. It currently saves FIF files with recording metadata and stimulation events in a BIDS-inspired layout, keeping recordings separate from processed outputs.

This is still in development. My aim is to make it reusable beyond our dataset, helping other TDT users prepare recordings for analysis and open-data sharing.

  • Python
  • ETL pipelines
  • Signal processing
  • Data quality
  • Data provenance
  • MNE-BIDS

Sep 2024–Dec 2024Visiting research

Neural-fibre modelling for spinal cord stimulation

Grill Lab · Duke University

At the Grill Lab at Duke, I investigated how spinal cord stimulation waveforms change neural-fibre activation. The simulations showed lower activation thresholds but less consistent firing with burst stimulation. This work became an IEEE EMBC 2025 paper.

Using Python and PyFibers, I simulated myelinated axons with an interpolated McIntyre–Richardson–Grill (MRG) model, representing nodal ion-channel dynamics and current flow through the myelinated fibre.

I compared tonic, FAST, and burst stimulation across fibre diameters, pulse widths, and active or passive charge balancing. I used bisection searches to estimate activation thresholds, then swept stimulation amplitude to examine how reliably each pulse produced an action potential. Spatiotemporal voltage maps let me inspect where spikes began, how they propagated, and when burst responses became irregular.

The model explores possible mechanisms rather than predicting clinical outcomes.

  • Python
  • Computational modelling
  • Biophysical axon models
  • Activation thresholds
  • Parameter sweeps

Side projectSoftware development

Trading-card identification and price lookup

I wanted to check whether a card in a shop was worth buying without manually searching several marketplaces. I used a pretrained DINOv3 vision transformer to index reference-image embeddings and retrieve matches by cosine similarity, with OCR to help resolve card identity. I also used 3D UMAP to inspect the embedding space.

After the user confirms a match, the app brings together available marketplace API prices and compares ungraded resale and graded-card scenarios against the sticker price, selling fees, grading costs, and configurable margin thresholds. Missing prices can be entered manually. It is a hobby project for comparing purchase options, not predicting resale returns.

  • DINOv3 embeddings
  • Similarity search
  • 3D UMAP
  • PaddleOCR
  • Next.js

Publications

  1. 2025

    Exploring Tonic and Burst Stimulation in Neural Fibers: A Computational Modeling Approach

    Nickolaj Ajay Atchuthan, Warren M. Grill, and Suzan Meijs

    IEEE EMBC 2025

  2. 2025

    Strengths & Weaknesses of RANSAC applied to Epidural & Intracortical Recordings

    Nickolaj Ajay Atchuthan, Felipe Rettore Andreis, Winnie Jensen, and Suzan Meijs

    IEEE EMBC 2025

  3. 2025

    A convolutional neural network to distinguish between brain responses to non-noxious and noxious input of the same modality: what does the machine see that we do not see?

    Nickolaj Ajay Atchuthan, Mikkel Bjerre Danyar, Hjalte Færregård Clark, Felipe Rettore Andreis, Winnie Jensen, and Suzan Meijs

    Research Square v1 preprint

  4. 2023

    Classification of noxious and non-noxious event-related potentials from S1 in pigs using a convolutional neural network

    Nickolaj Ajay Atchuthan, Hjalte Clark, Mikkel Bjerre Danyar, Amalie Koch Andersen, Felipe Rettore Andreis, and Suzan Meijs

    IEEE NER 2023

  5. 2023

    Spatio-Temporal Analysis of LTP-like Neuroplasticity in Pigs

    Mikkel Bjerre Danyar, Hjalte Færregård Clark, Nickolaj Ajay Atchuthan, Louise K. Daugbjerg, Amalie Koch Andersen, Taseer A. M. Janjua, and Winnie Jensen

    IEEE NER 2023

In preparation

  1. Thesis

    Mixed-effects modelling and threshold-free cluster enhancement of time–frequency contrasts in simultaneous somatosensory, prefrontal and anterior cingulate responses to graded peripheral nerve stimulation in a porcine large animal model

    Nickolaj Ajay Atchuthan, Christian Kruse Pedersen, Winnie Jensen, and Suzan Meijs

    Manuscript in preparation

  2. Thesis

    Zero-shot cross-animal transfer versus subject-specific fine-tuning of shallow-to-deep decoders for graded nerve stimulation from intracranial recordings of sensory, affective and cognitive cortical systems in a large animal model

    Nickolaj Ajay Atchuthan, Christian Kruse Pedersen, Winnie Jensen, and Suzan Meijs

    Manuscript in preparation

Experience

Apr 2024–present

PhD Fellow

Center for Neuroplasticity and Pain · Aalborg University

Working with multiregion intracranial recordings, signal analysis, research data pipelines, and interpretable deep-learning models.

Sep 2024–Dec 2024

Visiting Scholar

Grill Lab · Duke University

Built Python models of neural-fibre responses to spinal cord stimulation, resulting in an IEEE EMBC 2025 paper.

Oct 2023–Apr 2024

Research Assistant

Center for Neuroplasticity and Pain · Aalborg University

Developed explainable CNN analyses for intracranial recordings and evaluated RANSAC-based channel-quality methods. This work became the methodological starting point for the PhD.

Jan 2023–Jun 2023

Teacher in Business Informatics

TECHCOLLEGE · Aalborg

Taught business informatics (erhvervsinformatik), a core vocational subject covering digital empowerment, business-oriented digital development and computational thinking.

Education

2024–2025

Laboratory animal science

University of Copenhagen · Aarhus University

FELASA-accredited training in animal procedures, project design and care (EU Functions A, B and D), followed by an advanced course in porcine models for biomedical research. Together they underpin the surgical work in my PhD, including craniotomies, durotomies and electrode implantation.

2021–2023

MSc in Biomedical Engineering and Informatics

Aalborg University

  • LFP and spike activity. Analysed local field potentials and spikes across a 16-channel S1 microelectrode array, retaining spatial information to compare changes in time and frequency.
  • CNN classification of cortical responses. Preprocessed porcine µECoG recordings and used short-time Fourier spectrograms as CNN inputs to distinguish responses to different stimulation conditions.
  • Resting-state EEG and pain sensitivity. Used EEG band-power features and a random forest to study human pain sensitivity, in collaboration with REDO Neurosystems.
  • CNN-LSTM thesis. Combined continuous-wavelet spectrograms with a CNN-LSTM to compare S1 µECoG recordings across high-frequency stimulation, spared nerve injury, and control groups, and examined model feature attribution.

The first two projects were presented at IEEE NER 2023 in Baltimore.

2018–2021

BSc in Biomedical Engineering and Informatics

Aalborg University

Bachelor project: thermotactile feedback. With two fellow students, I developed a prosthetic interface that conveys temperature through modality-matched thermal feedback. We followed the V-model from functional and non-functional requirements through prototype development, verification, and user testing. We were finalists in the Health HUB AAU Innovation Award 2021.

EMG-controlled hand prosthesis. Earlier project work combined muscle-signal control, analogue circuitry, and vibrotactile feedback, connecting biosignal processing with assistive-device development.

Outside the lab

I enjoy photography, and hiking or climbing when I get to travel.

A sandstone arch framing distant mesas beneath a clear sky
A lone hiker overlooking a canyon landscape at sunset
Sunlight filtering between tall trees onto a forest path