Magnetic Resonance Imaging (MRI) – uses powerful magnets to align hydrogen atoms within a
magnetic field. Then, radio frequencies are directed at the part of the body to be imaged, producing
‘resonace’ or spinning of the hydrogen atoms. When the RF pulses cease, the hydrogen atoms return to
their natural aligment and as the atoms relax, each becomes a miniature radio transmitter emitting a pulse
that is detected. Voxel (volume pixel) is a three dimensional version of a pixel and the darkness or
coloration of each voxel represents the level of activity in an area. fMRI assess brain activity. fMRI uses
the fact that active neurons require more oxygen than less active neurons, and that variations in blood flow
on a particular area will reflect this need. Hemoglobin, the protein molecule that carries oxygen within the
blood has different magnetic properties when combined with oxygen or not and signals from a voxel will
change depending on the oxygenation of the blood in that area – this is known as the blood oxygenation
level dependent (BOLD) effect. MRI is better than CT and PET because it can provide images taken at
any angle without any movement of the individual. fMRI is also better than PET scans.
The electroencephalogram (EEG) – measure the activity of a large number of cells, known as a
field potentials. Most influenced by the cortical cells closest to the electrodes.
Evoked potentials – allows researchers to correlate the activity of cortical sensory neurons
recorded through scalp electrodes with stimuli presented to the participant. ERP – average of 100 or more
Magnetoencephalography (MEG) – record the brain’s magnetic activity. Active neurons put out
tiny magnetic fields. The skull bones and tissues allow magnetism to pass through without any reduction
and thus this is better than EEG in this way. MEG data can be superimposed on three dimensional images
obtained with MRI and this combo can provide simultaneous information about brain activity and
Single cell recordings –both extracellular and intracellular events from a single neuron can be
assessed using tiny mircoelectrodes surgically implanted in the area of interest.
Brain stimulation: the tissues of the brain lack receptors for brain and therefore local anaesthesia is
usually used. For ethical reasons, brain stimulation is done on animals rather than on humans. Repeated
transcranial magnetic stimulation (rTMS) is a technique for stimulating the cortex at regular intervals by
applying a magnetic pulse through a wire coil encased in plastic and placed on the scalp – this can help
temporarily change brain activity immediately below the stimulation site – can inhibit or disinhibit certain
Lesion – injury to neural tissue and can either be naturally occurring or purposefully produced –
primary purpose is to assess the probable function of an area. Ablation is when large areas of brain tissue
are surgically removed. Chemically produced lesions have the advantage of harming only the cell bodies
of neurons while leaving the nerve fibres travelling through the area intact. A reversible type of lesion can
be produced by cooling an area using a probe – the neurons are unable to function when chilled but return
to normal function when it returns to normal temperature.