# The Nanoneedle Net: A flexible and transparent 3D nanoelectrode array for mapping intracellular dendritic dynamics at the cortical surface

> **NIH NIH R21** · PURDUE UNIVERSITY · 2021 · $226,824

## Abstract

Project Summary
Neurons in the mammalian brain possess elaborate tree-like structures termed dendrites. These dendritic
branches with distinctive morphological features compartmentalize and shape synaptic inputs, which eventually
propagate to the soma to form the action-potential output (AP) – the unit currency of information transfer in the
brain. Unravelling how dendrites transform complex synaptic inputs into AP output, shape population-level brain
activity, and drive sensory input fundamental to our understanding of neural circuit mechanisms and brain
function. Of particular interest are the distal dendrites of layer 5 pyramidal neurons in the barrel cortex, whose
somatic output transfers sensorimotor information to a myriad of brain regions. These deep-layer pyramidal
neurons extend their dendrites vertically into the most superficial layer of the cortex where they integrate
extensive inputs from diverse brain regions, and exhibit a myriad of regenerative feedback events (E.g.: NMDA,
Calcium, Sodium spikes), which are believed to be fundamental to controlling the overall input-output-gain of the
neuron. However, the spatio-temporal dynamics of dendritic activity, and the overall relationship between
dendritic and somatic gain in vivo remains unknown. The small size of these dendrites (~2 µm in diameter) and
their location (<100 µm from the surface) has rendered conventional whole-cell electrophysiology infeasible –
the current gold-standard; while the proposed alternative approaches, such as calcium imaging, lack temporal
resolution to report fast sub-threshold membrane dynamics that underlie neural computation.
Here, we aim to map the electrical dynamics of distal apical dendrites in the somatosensory cortex of awake
behaving mice using a flexible and transparent vertical nanoelectrode platform termed ‘The Nanoneedle Net’.
The Net will comprise of 256 channels with 128 planar electrodes and 128 vertical needles. Each needle will be
40-60 µm in height, ~100 nm in tip diameter, and lipid-coated to facilitate seamless penetration into a membrane.
Our custom fabricated array (electrode pitch of 20 µm) once placed on the surface of the brain will allow the
needles to penetrate <60 µm deep and form a tight electrical seal with distal dendritic branches. Readout will be
accomplished through heavily multiplexed low noise custom CMOS amplifiers. To corroborate the origins of both
planar surface recordings and nanoneedle dendritic recordings in vivo, we will combine conventional intra- and
extracellular ground-truth electrophysiology, two-photon calcium imaging, optogenetics, spike sorting using
template matching, and whisker touch.
Ultimately, this platform will not only allow us to establish the computational rules by which distal dendrites shape
cortical output during active sensation, but provide a universal method to probe dendritic integration in the living
brain.

## Key facts

- **NIH application ID:** 10160915
- **Project number:** 5R21EB029740-02
- **Recipient organization:** PURDUE UNIVERSITY
- **Principal Investigator:** Krishna jayant
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $226,824
- **Award type:** 5
- **Project period:** 2020-05-07 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10160915

## Citation

> US National Institutes of Health, RePORTER application 10160915, The Nanoneedle Net: A flexible and transparent 3D nanoelectrode array for mapping intracellular dendritic dynamics at the cortical surface (5R21EB029740-02). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10160915. Licensed CC0.

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