The various methods for recording brain signals in detail, focusing on both non-invasive and invasive techniques.
1.
Electroencephalography (EEG)
Type: Non-invasive
Description:
- EEG involves placing electrodes
      on the scalp to capture electrical activity generated by neurons.
- It records voltage fluctuations
      resulting from ionic current flows within the neurons of the brain.
- This method provides high
      temporal resolution (millisecond scale), allowing for the monitoring of
      rapid changes in brain activity.
Advantages:
- Relatively low cost and easy to
      set up.
- Portable, making it suitable for
      various applications, including clinical and research settings.
Disadvantages:
- Lacks spatial resolution; it
      cannot precisely locate where the brain activity originates, often
      leading to ambiguous results.
- Signals may be contaminated by
      artifacts like muscle activity and electrical noise.
Developments:
- Advances such as high-density EEG
      use more electrodes to improve spatial resolution and signal quality
      through techniques like different montages (e.g., bipolar, Laplacian,
      common average references).
2.
Electrocorticography (ECoG)
Type: Invasive
Description:
- ECoG involves placing electrodes
      directly on the cerebral cortex after a surgical procedure.
- This method measures electrical
      activity from the cortex with higher fidelity than EEG.
Advantages:
- Offers better spatial resolution
      (millimeter scale) and frequency range (up to 200 Hz or more).
- Signals are of higher amplitude
      and quality, providing clearer data that is less susceptible to motion
      artifacts.
Disadvantages:
- Invasive nature requires surgery,
      posing risks such as infection or damage to the brain tissue.
- The electrodes can only be left
      in place for a short time to prevent tissue damage.
3.
Intracortical Recordings
Type: Invasive
Description:
- This technique involves
      implanting electrodes directly into the brain tissue itself to record
      electrical activity at the level of individual neurons or small groups of
      neurons.
Advantages:
- Provides the highest spatial
      resolution and can capture detailed information about neuronal activity.
Disadvantages:
- The procedure is highly invasive,
      entails significant risks, and is usually limited to research
      environments.
4.
Functional Magnetic Resonance Imaging (fMRI)
Type: Non-invasive
Description:
- fMRI measures brain activity by
      detecting changes in blood flow, utilizing the principle of neurovascular
      coupling.
- It captures high-resolution
      images (in the millimeter range) of brain activity across the entire
      brain.
Advantages:
- Offers excellent spatial
      resolution of brain activity and can visualize activation patterns across
      different brain regions.
Disadvantages:
- It is expensive, less portable,
      and typically involves lengthy setup times.
- The equipment can be
      uncomfortable due to noise and requires participants to remain still even
      during scanning.
5.
Near-Infrared Spectroscopy (NIRS)
Type: Non-invasive
Description:
- NIRS uses near-infrared light to
      assess blood flow and oxygenation in the brain, providing insight into
      metabolic processes.
Advantages:
- Portable and can be used in
      various settings, including outside of clinical environments.
Disadvantages:
- Limited depth of penetration and
      spatial resolution compared to fMRI, rendering it less capable of
      capturing deeper brain activity.
Summary
Each method of brain
signal recording has its unique strengths and weaknesses, making them suitable
for different research or clinical applications. Non-invasive methods like EEG
and fMRI offer ease of use and safety, while invasive techniques such as ECoG
and intracortical recordings provide superior spatial resolution and signal
quality at the cost of increased risk. The ongoing development of these
technologies aims to enhance their effectiveness in understanding brain
function and improving clinical outcomes.
 

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