V) Intracortical brain interfaces

Question 1

Give three reasons to interface the brain.

Answer 1

To gain fundamental knowledges, to restore sensory function or to perform high resolution recording/imaging.

Question 2

What is the grey matter in the brain ? What is the white matter then ?

Answer 2

The grey matter is the body of the cells while the white is the fibers/axons and the white come from the myeline.

Question 3

Cite five structure that coresponds anatomicaly and functionnaly :

Answer 3

Motor tasks, sensory inputs, speech, hearing and vision.

Question 4

What is the “homonculus” purpose ?

Answer 4

To show the topographical organization of muscles.

Question 5

Cite the different parts of the neuron.

Answer 5

Cell body, dendrites, hillcok axon, myelin sheat, node ranvier;, axone.

Question 6

describe the different events happening during an action potential .

Answer 6

Treshold- stimulus - depolarisation - repolarisation - hyperpolarisation (refractory period) and resting state.

Question 7

CIte the different type of recording we can make intracorticaly and to which size of population it is adapted. Also, define if it is invasive or not.

Answer 7

Single Units Array - for one neuron (invasive)
local potential field or electrocorticogram for neuronal population (invasive)
electro-magneto encephalogram (MEG/EEG) for neural mass. (non invasive)

Question 8

Define in three steps the Utah Electrode array

Answer 8

• One electrode per channel
• Backside contacts
• Made out of a single “block”

Question 9

How to create conductive pathways though a wafer ?

Answer 9

Before the thermomigration process. Aluminium pads are created on one side of a n-type silicon wafer. During the process; a temperature gradient is applied to the silicon wafer which drives Si-Al eutetic droplet thorugh the wafer. After the process, highly doped p+ silicon trials result from the eutetic droplet passage through the n type substrate.

Question 10

After the wafer, what are the step to create Utah electrode arrays ?

Answer 10

Using a dicing saw to create the 'posts'.
Etching the posts into needle like with hydrofluoric acid and nitric acid. (dynamic etch and static etch to polish).
electrode metallization (shadow mask, sputter mask with gold and platinum).

Question 11

What was the problem with first implantation of UEA ?

Answer 11

can provoque entry of germs, problem with cables and ground electrodes.

Question 12

What is the Integrated neural interfacte (INI).

Answer 12

Wireless integrated system based on the UEA.

Question 13

Describe the concept of INI.

Answer 13

10x10 array of neural amplifier and spoke detector, FSK:ASK trasmitter, voltage regulator, clock recovery and forward telemetry decoder, charge redistribution adc.

Question 14

Which coating was sed for coating of INI ?

Answer 14

Parylene C and silicon carbide.

Question 15

Describe the steps to create sensor process of INI.

Answer 15

AuSn reflow soldering, SMD assembly, underfilling, coil manufacturing and ferrite assembly, coil assembly.

Question 16

What was the final ‘sandwichin” for INI ?

Answer 16

Si-lid, coil, ferrite, IC, Array.

Question 17

What is the use and limit of UEA ?

Answer 17

can be used in primates but can’t record from different layers for example…

Question 18

What is the principle of Michigan electrodes ?

Answer 18

Silicon substrate, multiple electrodes on one shaft (4).

Question 19

how do the michigan electrodes evoluted ?

Answer 19

wireless, eletronics, signal processing and drug delivrery.

Question 20

What is the good point of having symetric cross section ?

Answer 20

it is thin and penetrates easily and creates less damages.

Question 21

What are “passive probes”

Answer 21

Probes not involving any electronics.

Question 22

How are created interconnects in Michigan electrodes ?

Answer 22

silicon thinned down to became flexible.

Question 23

When is done micromachinning in michigan electrodes ?

Answer 23

Post CMOS.

Question 24

What is CMOS ?

Answer 24

Standard manufactoring technology, Complementary Metal oxide semi conductor. .

Question 25

What was the idea of integrating microfluidic channels ?

Answer 25

Make a channel into silicon, allows the entry of action solution.

Question 26

What was the idea of neuroprobes ?

Answer 26

Recording for single cells or LFP, biosensing (glut, DA), microfluidic (drug delivery) and system (microelectronics, telemetry).

Question 27

How are silicon probes for neuroprobes ?

Answer 27

1/4 shaft perprobes, 9 electrodes per shadt (8 circular body electrode and one tip electrode)/

Question 28

what are the ideas behind flexible probes ?

Answer 28

reduce interaction, mismatch between brain tissue and conventionnal probes, .

Question 29

which ideas were tried to have flexible probes ?

Answer 29

cover probes with soluble material or use materials as parylene C or polyimide.

Question 30

What is the BMT approach to have flexible probes ?

Answer 30

polyimide probes to be implated folded to be solid, guide wires, resurption of coating.