MBB1 - measuring brain activity

What is brain imaging?

Assesses brain structure and function “non-invasively” without dissection or damage to the brain.

Electroencephalography (EEG) function

Refers to both the equipment used and the data. Measures electrical activity in the brain through electrodes placed on the scalp

When was the first human EEG? When was the first demonstration of epileptiform spikes with the EEG?

1924 - first human EEG by Hans Berger and 1934 - first demonstration of epileptiform spikes by Fisher and Lowenback

Strengths of EEG

good temporal resolution, cheap, portable, safe and well tolerated by patients

EEG limitations

poor spatial resolution, only detects activity on the surface of the cortex

What is the function of Electrophysiology (single neurons)?

Records the electrical activity of individual neurons and their action potentials

When and who were able to record action potentials in axons?

Hodgkin and Huxley recorded the action potentials of axons in Atlantic squids in 1952. Hubel and Wiesel mapped the organisation of the visual system (Nobel prize in 1981)

Electrophysiology (single neurons) strengths

Directly records from individual neurons

Electrophysiology (single neurons) limitations

high risk of infection due to being invasive and can only record a few neurons at a time

MRI structural imaging function

Generates a very strong magnetic field to cause hydrogen atoms to align and the MRI captures the signals emitted from the alignment, generating an image.

fMRI functional imaging function

fMRI reflects how oxygenated blood doesn’t distort while deoxygenated blood does distort around the magnetic field. BOLD tracks the ratio of oxygenated vs deoxygenated blood.

Who and when was BOLD first used to show activation of human visual cortex?

By Kenneth Kwong in 1992

MRI strengths

High spatial resolution, non-invasive imaging, can identify specific structural and functional properties

MRI limitations

expensive, large equipment, safety risks, requires specialist staff.

Positron emissions tomography (PET) function

Uses radioactive tracers to visualise glucose metabolism, the receptor function or protein binding. Can be used to diagnose Alzheimer’s

PET strengths

Can detect different chemicals associated with metabolism or neurotransmitter levels

PET limitations

Expensive, low spatial resolution and requires specialist facilities and staff

Brain modification

Using methods to remove and decrease brain activity or stimulating and enhancing a region to increase brain activity

Enhancement meaning

The improvement of healthy function to above or better than normal

Importance of brain modification for scientific research

Provides information about causation and the necessity of brain regions for specific functions

Ablation studies

Ablation = “to carry away”, ablation studies were carried out on animals

Who introduced the prefrontal leucotomy? How did they test this? What did it prove?

Egas Moniz who removed the frontal lobes of a chimpanzee, making it calmer, hence, linked personality to the frontal lobes

What are the methods for a frontal leucotomy?

Two methods. Either through drilling a hole in the skull or inserting a cutting implement above the eye into the brain

Frontal leucotomy limitations

Ineffective, profound personality consequences, highly invasive

When and who popularised the frontal leucotomy?

Walter Freeman in the 40’s and 50’s

When and who introduced electrical brain stimulation? How did they test this? What did it prove?

Fritsch and Hitzig in 1870 electrically stimulated part of the frontal cortex in dogs which resulted in contractions of muscles on the opposite side. Revealed localisation.

When was non-invasive ECT invented?

In the 1930’s to treat psychiatric symptoms

How does Transcranial Magnetic stimulation (TMS) work?

A coil carrying an electrical current sends a brief, focal magnetic pulse to activate a small region of cortex

Pharmacology drugs function

Can impact every stage of neurotransmitter function from synthesis to release to receptor binding