Reuptake
Rapid removal of neurotransmitter from the synaptic cleft back into the terminal bouton by transporter molecules embedded in the presynaptic membrane.
Enzymatic Deactivation
Enzyme cleaves the transmitter molecules so they become incapable of binding to a receptor.
Glial cell uptake
Astrocytes take up the neurotransmitter and destroy it before breaking it down.
Autoreceptors
Receptors located on the presynaptic neuron bind the same neurotransmitter as that released by the neuron. Decreases the activity of the presynaptic neuron and acts as a feedback mechanism to keep it from being over activated.
Diffusion
Neurotransmitter diffuses from the synaptic cleft; floats away by putting it out of range of the receptors.
Glutamate
Overactivity of this neurotransmitter is thought to play a role in the development of epilepsy, epilepsy drugs decrease the amount of glutamate released from the neurons which can make someone feel sleepy.
Acetylcholine
Plays a role in overall cortical excitability and has been linked to the ability to pay attention which is important for memory, important for overall arousal and vigilance. Decreased amounts have been linked to types of dementia (Alzheimer's disease)
Norepinephrine
Influences arousal and attention.
Serotonin
Influences sleep, important for regulating aggression and pain, has been linked to memory and is important for putting new memories in long- term storage.
CT
Uses x-rays to provide information on the density of brain structures. CSF is least dense and bone is most dense. Bright areas are high density detected by scintillation counters.
CT Advantages
Measures brain structure.
Good spatial resolution.
Can give immediate information about brain hemorrhage.
CT disadvantages
Involves radiation.
No temporal information provided.
Not able to measure brain function.
MRI
Uses magnetic fields to distort protons to obtain information on brain anatomy/structure. 3 magnetic fields: static, pulse sequence, and intensity to obtain a 3D image.
MRI advantages
Excellent clarity of the picture with better spatial resolution than CT.
Does not require radiation.
MRI disadvantages
No temporal information provided.
Not able to measure brain function.
People with metal in their bodies can't be put in the strong magnetic fields
PET
Uses high-energy ionizing radiation - usually water with a radioactive isotope. Photocells detect photons of light - active areas emit many photons so are bright.
PET advantages
Assess brain structure & function. Allows the examination of how the brain uses a variety of molecules provided that a radioactive version of the molecule can be created.
Can show hypofunction.
PET disadvantages
Need to inject a radioactive substance.
Time needed to measure a radioisotope half-life is slow relative to cognitive processes so spatial resolution is better than temporal.
fMRI
A variation of MRI. "f" stands for functional because neuronal activity accompanied by other physiological function are measured by changes in hemoglobin to determine where activities take place.
fMRI advantages
Measures structure & function. Sensitive to blood flow that is associated with neural activity.
Excellent spatial resolution.
fMRI disadvantages
Moderate temporal resolution abilities relative to cognition.
Ambiguous about active inhibition vs. excitation.
EEG
Detects electrical signals in the brain using surface electrodes applied to the scalp.
EEG advantages
Identifies focally active brain regions produced by active brain cells (postsynaptic currents in the dendrites). Important in diagnosis and treatment of seizures and epilepsy.
EEG disadvantages
The signal may be distorted by attenuation produced by intervening layers of tissue and bone.
MEG
Relies on the recording of magnetic potentials at the scalp to index brain activity. Records magnetic fields using SQUIDS-superconducting quantum interference devices.
MEG advantages
Magnetic fields are detected more easily than electrical fields through the scalp. Magnetic signals won't be affected by the density of tissue in certain areas of the brain.
MEG disadvantages
VERY expensive - requires specialized equipment at ultra cold temperatures.
Only cells aligned parallel to the plane of the surface can be measured.
TMS
Produces a pulsed magnetic field in the brain that induces an electrical field which alters the membrane potential of neurons causing them to fire.
TMS advantages
Can simulate reversible lesions.
Potential to provide information on how the brain reorganizes after injury and to learn about connectivity of brain areas during specific cognitive and language tasks.
TMS disadvantages
Relatively new technology so need to be cautious about the effects of repeated magnetic stimulation to the brain.
Can only measure activity close to the brain surface.
Attention (tx)
Alternating, dividing, selective.
Memory (tx)
Working, long term, explicit, implicit.
Executive Function (tx)
Organizing, planning, self-monitoring.
Factors of Damage Impacting Function
Location, size/extent, severity, age of person, comorbidities.
Frontal Lobe function
Performs executive aspects of attentional control. Planning, guidance, behavior evaluation, judgement, decision making, initiation/suppression, motor programming.
Parietal function
Association cortex, integrates sensory info. Also responsible for reading and writing.
Temporal function
Memory, aud. processing, item recognition, emotion.
Basal Ganglia
Involved in motor control. Indirect pathway damage causes too little movement, damage to direct causes too much.
reticular activating system
Structure of basic attention, regulates alertness and arousal. If damaged, results in coma where the person is unresponsive.
Thalamus
Aids in attention, information filtering.
dorsolateral prefrontal cortex
Working memory
Hippocampus
Long-term memory.
Thromboembolic Stroke
Occurs when an artery is blocked and part of the brain loses its blood supply. Excitotoxicity is a consequence; glutamate builds up during because of a lack of oxygen blocks their receptors and there is too much in the synapse (too much glutamate causes s
Hemorrhage
Caused by rupture or leakage of cerebral blood supply, extracerebral are named according to where the blood accumulates
Brain Tumor
May be primary or secondary, compresses the surrounding brain tissue as it grows, tissue around the tumor can swell and lead to behavioral changes.
Diaschisis
Damage in areas peripheral to the major damage
hydrocephalus
Cerebral ventricles become enlarged, obstructing the flow of CSF from the ventricles into the subarachnoid space, as the pressure rises the ventricles enlarge and the brain is compressed