If used properly, electrical stimulation is an extraordinarily useful and powerful technique for dissecting behavioural and neuro-physiological mechanisms underlying psychological processes.
When current is passed extra-cellularly, most of the voltage change is in the voltage outside the cell. We change the transmembrane potential (Vm) primarily by changing the voltage outside the cell (Vo)
Transcranial direct current stimulation (tDCS) uses a low-intensity (0.5-2mA) constant current, which is applied directly to the head, partially penetrates the skull, and enters the brain. This non-invasive method of stimulation has been shown to modulate cortical excitability, producing changes of up to 40% that can last for between 30 and 120 minutes.
Clinical applications of tDCS are:
Motor enhancement in stroke rehabilitation.
Behavioural performance enhancement with Alzheimer patients.
Modulation of emotional neural circuits in depression.
Transcranial Magnetic Stimulation (TMS) is a technique that induces localized, relatively small amplitude currents in cortical tissue via the principles of electromagnetic induction. TMS can be used to study brain activity both as a tool for modulating cortical excitability and as a method for probing neurophysiology within the primary motor cortex.
TMS can be used in the treatment of depression, Parkinson's disease, Dystonia, Schizophrenia, Tinnitus, and in stroke patients or those suffering chronic pain.
Electro-convulsive Therapy (ECT) is a procedure, done under anaesthesia, in which small electric currents are passed through the brain, intentionally triggering a brief seizure. ECT seems to cause changes in brain chemistry that can quickly reverse symptoms of certain mental health conditions. ECT often works when other treatments are unsuccessful and when the full course of treatment is completed, but it may not work for everyone.
ECT can provide rapid, significant improvements in severe symptoms of several mental health conditions such as.
Severe depression accompanied by psychosis, severe mania, Catatonia, or agitation and aggression in people with dementia.
An Event-Related Potential (ERP) is the average electrical activity time-locked to a stimulus, e.g., click or flash. ERPs can be auditory, visual, or somatosensory. Evoked Potentials are a subset of ERPs, e.g., AEP, VEP and SEP.
Clinical auditory evoked potentials are used to gather information about the inner ear and brain hearing pathways, cortical activity.
Clinical visual evoked potentials test the function of the visual pathway from the retina to the visual cortex.
Clinical somatosensory evoked potentials identify impaired conduction caused by axonal loss or demyelination, for example, those caused by Multiple Sclerosis.
3D printing is also known as additive manufacturing. It is a process of making three dimensional solid objects from a digital file. The desired object is created by laying down successive layers of material until the object is created. Each of these layers can be seen as a finely sliced horizontal cross-section of the eventual object.
EEG electrodes and sensors can be manufactured using 3D printing technology.