Sem2 Week 4 - Neuroscience

A fine wire electrode placed near neurons in the brain. It detects small voltage changes in the surrounding fluid picking up spike signals without penetrating the cell.

Sub-millisecond. This makes them among the most precise tools for tracking the exact timing of neural firing.

One or a few neurons at a time depending on how close the electrode tip is to each cell.

A grid of rigid silicon shanks that can be surgically implanted into the cortex. It is the most widely used implantable multi-electrode array design.

It decodes motor cortex signals to allow patients to control robotic limbs with their thoughts. The BrainGate Consortium is a key example.

High-density silicon probes with 960 recording sites along 1 cm digitising 384 channels simultaneously at 30 kHz allowing recording from 100+ neurons at once.

A high-density array with 4096 channels recording at 18 kHz. It covers a larger area than Neuropixels and is typically used for in vitro recordings.

Electrocorticography. Electrode grids placed directly on the cortical surface requiring surgery but not penetrating brain tissue.

Planning epilepsy surgery. It localises seizure foci across large areas of cortex before deciding what tissue to remove.

Summed synaptic activity from thousands of neurons beneath each scalp electrode reflecting population-level brain activity rather than individual neurons.

Sub-millisecond. Electrical signals travel almost instantaneously so EEG can track rapid changes in brain activity very precisely.

Signals are smeared and distorted passing through brain skull and scalp before reaching electrodes making it hard to pinpoint where activity originates.

An EEG signal averaged across many repetitions of the same stimulus. Averaging cancels random noise leaving only the brain’s consistent response to that event.

Components like N1 P2 N2 and P3 named by polarity (N=negative P=positive) and latency in milliseconds. They reflect stages of sensory processing attention and cognition.

The tiny magnetic fields generated by synchronised electrical currents in neurons detected using superconducting sensors called SQUIDs.

Both have similar spatial resolution but MEG is less distorted by the skull and scalp because magnetic fields pass through tissue more uniformly than electric fields.

Accurately localising the brain source of a signal in both space and time for example tracking how reading activates different areas in sequence.

Blood-Oxygen-Level Dependent (BOLD) contrast. Active neurons consume more oxygen increasing local blood oxygenation which fMRI detects.

A 3D volume unit and the basic spatial element of an fMRI image. A single voxel can contain up to millions of neurons.

About 1 sample per 1-2 seconds because it measures slow blood flow changes rather than electrical signals directly.

A technique using fluorescent indicators that light up when calcium enters a neuron during firing allowing neural activity to be visualised directly.

Roughly 100 to 10000 neurons simultaneously depending on the imaging setup and volume being scanned.

Around 30 frames per second or less because the fluorescent indicators respond and decay slowly over seconds.

It captures all neurons within a defined volume whereas electrodes only sample neurons immediately adjacent to the probe tip.