EEG is a functional brain research technique that records electric activity caused by neural activity. EEG is often recorded to study ERPs (see below). EEG is typically measured with electrodes attached to the scalp. EEG offers a good temporal resolution, but exact sources of brain activity are challenging to interpret. It is a safe, cost-effective and easy method that is in heavy clinical and scientific use around the world, even in studies of newborn infants.
We use the following EEG devices:
BrainProducts BrainAmp DC
NeuroScan Synamps 2
Event-related potentials (ERP)
ERPs are electric responses recorded from the brain, and they are calculated from the EEG signal. ERPs are event-related, i.e., they depict the brains activity in response to an internal or external stimulus, for example a repeating sound. In a typical ERP experiment, EEG is recorded and at the same time, the participant hears sounds, sees pictures or performs a given task.
In measuring ERPs it is important to have an extremely controlled set of stimuli. Usually the external stimuli are auditory, visual, or both and they are repeated rapidly in a sequence. These stimuli can be delivered by using specialized hardware and software which are optimized to maintain high temporal accuracy. For presenting stimuli we mainly use Presentation (Neurobehavioral Systems) and Psychtoolbox.
Mismatch negativity (MMN)
MMN is an ERP response with negative polarity, calculated by subtracting the ERP to frequently occurring standard stimuli from the ERP to occasionally occurring deviant stimuli in a so-called oddball paradigm. It reflects pre-attentive processing of expectation violations and can reflect differences in long-term experience, e.g., it can be modified with language learning or music training. MMN was first introduced by Risto Näätänen and colleagues in CBRU in 1978, and is currently studied extensively around the world. Because MMN elicitation is pre-attentive, it can be measured already in prenatal and neonatal age.