Week 6 Flashcards
What do lesion studies tell us about behaviour
Lesion studies help to understand the functions of particular brain areas through observing behaviour changes after a site is damaged.
What is experimental ablation
Experimental ablation is the removal or destruction of a portion of the brain of a laboratory animal.
What is a brain lesion
A brain lesion refers explicitly to a wound or injury of the brain.
Who is phineas gage
He was a construction worker who set off an explosion that sent an iron rod shooting through his cheek and head.
He had a complete personality change after experiencing damage to his frontal lobe.
Who was Tan
He was someone with language difficulties. He was able to understand and follow commands however the only word he could say was Tan.
Broca performed an autopsy which found a lesion on the left frontal lobe of his left cerebral hemisphere, in an area now known as “Broca’s Area”.
His condition was termed “Aphasia” (the inability to produce words that were meaningful, but being able to understand language perfectly).
Who was HM
He suffered a bicycle accident at a young age that left him with severe seizures (epilepsy). At 26 he was operated on and it was successful.
The doctors realised the seizures were originating from the left and right medial temporal lobes which include; the hippocampus, amygdala and part of the entorhinal cortex. They removed the related brain tissue.
After the surgery his long term memory formation was impaired.
How does a researcher produce a subcortical lesion
Radio frequency lesions and excitotoxic lesions
What is a radio frequency lesion.
Electrical current is passed through a stainless steel wire (electrode)
Researchers guide the electrode to a very specific location in the brain
Activate a lesion making device that produces an alternating current of very high frequency - a radio frequency
Passing current through brain tissue produces heat that kills cells surrounding the tip of the electrode.
What is an excitotoxic lesion
Excitatory amino acid is injected via a cannula into a brain region.
The amino acid kills neuron cell bodies by stimulating them to death
Axons nearby are spared = selectivity.
What are sham lesions
Researchers insert an electrode or a cannula into the brain region of an animal, but do not activate the RF current, or inject the amino acid.
This is to account for possible damage to brain tissue along the way of a cannula or electrode being put in the brain.
How can brain lesions be made temporarily
Injecting a local anaesthetic into the part of the brain you want to lesion. This anaesthetic blocks action potentials in axons entering or leaving to produce a temporary lesion.
What are the 3 types of non invasive brain structure imaging
- Computerised tomography (CT)
- Magnetic Resonance Imaging (MRI)
- Diffusion Tensor Imaging (DTI)
What is Computerised tomography (CT Scan)
The use of a device that employs a computer to analyse data obtained by a scanning a beam of X-rays to produce a two-dimensional picture of a “slice” through the body
What is Magnetic Resonance Imaging (MRI)
A technique whereby the interior of the body can be accurately imaged; involves the interaction between radio waves and a strong magnetic field.
The magnet causes protons in the brain tissue to line up in parallel (normally they are in random orientations)
Protons are knocked over by a powerful pulse of radio waves. When the pulse is turned off, the protons go back to their original configuration, emitting radio waves as they do.
Scanner picks up the radio frequency energy being emitted.
A powerful computer compiles the density based information to generate a detailed cross sectional view of the brain
Where are protons found and where are they mostly found in the brain.
In the nuclei of atoms, and most protons in the brain are hydrogen atoms
What is Diffusion Tensor Imaging (DTI)
An imaging method that uses a modified MRI scanner to reveal bundles of myelinated axons in the living human brain.
Molecules move in random directions because of thermal agitation, and the higher temperature, the faster the movement.
DTI takes advantage of this.
Movement of water molecules in bundles of white matter will not be random, but will tend to be in a direction parallel to the axons that make up the bundles
The MRI scanner uses information about the movement of the water molecules to determine the location and orientation of bundles of axons in white matter.
What is Fractional Anisotropy (FA)
It measures the freedom of movement of water around the tissues.
Where are FA values high and low
White matter is higher FA values and grey matter is lower FA values
