Neurophysiology Flashcards
Neurons and communication
Main signalling units of the nervous system. 4 divisions: Cell Body/Soma Dendrites -> receive Axon -> transmit Presynaptic Terminals
Received by the dendrite, travel to axon down to next neuron.
Electrical current - positive or negative charge.
Neurotransmitters released by pre-synaptic terminal, picked up by receptors on the postsynaptic dendrite and create new electrical current.
Fluctuations in current create brain-waves (oscillations) - 2500 Herz.
•Which creates an electric current, that then travels down the neuron as before
Measuring and modifying techniques
Measure or modify brain activity.
Measuring: EEG or MEG.
Modifying: Deep Brain Stimulation (DBS), Transcranial Direct Current Stimulation (tDCS), Transcranial Magnetic Stimulation (TMS).
Deep Brain Stimulation
Implants a ‘brain pacemaker’
Sends electrical signal to stimulate parts of brain.
Internal pulse generator under skin by clavicle
Sends out electrical pulse that travels up extension to the lead (insulated wire with electrodes implanted in brain).
Increase neurotransmitter release, neuro-plastic changes, functional activation of region.
Parkinson’s and Chronic Pain in US.
Treatment-resistant Depression and OCD.
DBS for depression
Stimulate Subgenual Cingulate Gyrus & Nucleus Accumbens.
Increased activity in Prefrontal Cortex.
Decreased activity in Amygdala.
Increased serotonin and dopamine.
DBS for OCD
20-40% have persistent, treatment-resistant symptoms.
Most prominent biological model of OCD is the orbitofronto-striatal.
Data limited from small samples.
Most promising target - ventral striatum.
DBS advantage & disadvantages
Reversible, precise, few complications and side-effects.
Invasive, expensive, haemorrhaging, infection, headache, irritable.
Transcranial Direct Current Stimulation (tDCS)
Direct current to a brain region through electrodes on scalp.
Recent resurgence of interest but been around for > 100 years.
Battery powered device delivers constant current.
Electrode in a region of interest.
Reference electrode to complete the circuit.
Increase neuronal excitability (anodal stimulation).
Decrease neuronal excitability (cathodal stimulation).
tDCS for depression
Used in combination with cognitive therapy.
Mantovani et al (2012):
52 year old woman with treatment-resistant depression.
Left prefrontal cortex improved symptoms, remission did not last.
When combined with cognitive therapy remission lasted.
12-month follow-up complete remission and no adverse side-effects.
tDCS advantages and disadvantages
Low spatial resolution - large areas activated/suppressed.
Cognitive impairments/improvements are short term.
Skin irritation.
No long-term adverse effects have been identified.
Transcranial magnetic stimulation (TMS)
Rapidly changing electromagnetic fields to induce electrical currents.
When applied repetitively (rTMS) it can increase or decrease cortical excitability.
Low frequency stimulation inhibits.
High frequency stimulation activates.
rTMS for depression
Activation of left prefrontal cortex.
Inhibition of right prefrontal cortex.
Both simultaneously.
Increases efficacy of anti-depressants.
rTMS for schizophrenia
Left dorsolateral prefrontal cortex (DLPFC) - negative symptoms.
Left temporoparietal cortex (TPC) - positive symptoms - auditory hallucinations.
rTMS advantages and disadvantages
Headaches, seizures, discomfort during stimulation.
No long-term adverse effects.
Definition
Study of the function of the nervous system.
Chemical and electrical.
Central: Brain and Spinal Cord
Peripheral: Nerves in the rest of the body
