An
event-related potential (ERP) is any measured
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
response that is directly the result of a
thoughtThought and thinking are mental forms and processes, respectively . Thinking allows beings to model the world and to deal with it according to their objectives, plans, ends and desires. Words referring to similar concepts and processes include cognition, sentience, consciousness, idea, and...
or
perceptionIn philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was predicted that building perceiving machines would take about a decade,...
. More formally, it is any stereotyped
electrophysiologicalElectrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
response to an internal or external stimulus.
ERPs are measured with
electroencephalographyElectroencephalography is the recording of electrical activity along the scalp produced by the firing of neurons within the brain . In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from...
(EEG). The
magnetoencephalographyMagnetoencephalography is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as superconducting quantum interference devices . These measurements are commonly used in both research and clinical settings...
(MEG) counterpart of ERP is the ERF, or event-related field.
ERPs can be
reliablyIn statistics, reliability is the consistency of a set of measurements or measuring instrument, often used to describe a test. This can either be whether the measurements of the same instrument give or are likely to give the same measurement , or in the case of more subjective instruments, such as...
measured using electroencephalography (EEG), a procedure that measures
electricalElectricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge...
activity of the brain through the
skullThe skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
and
scalpThe scalp is the anatomical area bordered by the face anteriorly and the neck to the sides and posteriorly.-Layers:It is usually described as having five layers, which can be remembered with the mnemonic "SCALP":....
.
An
event-related potential (ERP) is any measured
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
response that is directly the result of a
thoughtThought and thinking are mental forms and processes, respectively . Thinking allows beings to model the world and to deal with it according to their objectives, plans, ends and desires. Words referring to similar concepts and processes include cognition, sentience, consciousness, idea, and...
or
perceptionIn philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was predicted that building perceiving machines would take about a decade,...
. More formally, it is any stereotyped
electrophysiologicalElectrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
response to an internal or external stimulus.
ERPs are measured with
electroencephalographyElectroencephalography is the recording of electrical activity along the scalp produced by the firing of neurons within the brain . In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from...
(EEG). The
magnetoencephalographyMagnetoencephalography is an imaging technique used to measure the magnetic fields produced by electrical activity in the brain via extremely sensitive devices such as superconducting quantum interference devices . These measurements are commonly used in both research and clinical settings...
(MEG) counterpart of ERP is the ERF, or event-related field.
Measurement
ERPs can be
reliablyIn statistics, reliability is the consistency of a set of measurements or measuring instrument, often used to describe a test. This can either be whether the measurements of the same instrument give or are likely to give the same measurement , or in the case of more subjective instruments, such as...
measured using electroencephalography (EEG), a procedure that measures
electricalElectricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge...
activity of the brain through the
skullThe skull is a bony structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
and
scalpThe scalp is the anatomical area bordered by the face anteriorly and the neck to the sides and posteriorly.-Layers:It is usually described as having five layers, which can be remembered with the mnemonic "SCALP":....
. As the EEG reflects thousands of simultaneously
ongoing brain processesThe term ongoing brain activity is used in electroencephalography and magnetoencephalography for those signal components that are not associated with the processing of a stimulus or the occurrence of specific other events, such as moving a body part, i.e. that do not form evoked potentials/evoked...
, the brain response to a single stimulus or event of interest is not usually visible in the EEG recording of a single trial; to see the brain response to the stimulus, the experimenter must conduct many trials (100 or more) and average the results together, causing random brain activity to be averaged out and the relevant ERP to remain.
While
evoked potentialAn evoked potential is an electrical potential recorded from the nervous system of a human or other animal following presentation of a stimulus, as distinct from spontaneous potentials as detected by electroencephalography or electromyography .Evoked potential amplitudes tend to be low, ranging...
s reflect the processing of the physical stimulus, event-related potentials are caused by the "higher" processes, that might involve
memoryIn psychology, memory is an organism's mental ability to store, retain, and recall information. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing the memory....
,
expectationIn the case of uncertainty, expectation is what is considered the most likely to happen. An expectation, which is a belief that is centred on the future, may or may not be realistic. A less advantageous result gives rise to the emotion of disappointment. If something happens that is not at all...
,
attentionAttention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources...
, or changes in the mental state, among others.
Nomenclature
Though some ERP components are referred to with acronyms (e.g.,
early left anterior negativityThe early left anterior negativity is an event-related potential in electroencephalography , or component of brain activity that occurs in response to a certain kind of stimulus...
- ELAN), most components are referred to by a preceding letter indicating polarity followed by the typical latency in milliseconds. Thus, the N400 ERP component is described as a negative voltage deflection occurring approximately 400ms after stimulus onset, whereas the P600 component describes a positive voltage deflection 600ms after stimulus onset. The stated latencies for ERP components are often quite variable; for example, the N400 component may exhibit a latency between 300ms - 500ms.
Clinical ERP
PhysicianA physician — also known as medical practitioner, doctor of medicine, medical doctor, or simply doctor — practices the ancient profession of medicine, which is concerned with maintaining or restoring human health through the study, diagnosis, and treatment of disease or injury...
s and
neurologistsNeurology is a medical specialty dealing with disorders of the nervous system. Specifically, it deals with the diagnosis and treatment of all categories of disease involving the central, peripheral, and autonomic nervous systems, including their coverings, blood vessels, and all effector tissue,...
will sometimes use a flashing
visualVisual perception is the ability to interpret information and surroundings from visible light reaching the eye. The resulting perception is also known as eyesight, sight or vision...
checkerboard stimulus to test for any damage or trauma in the visual system. In a healthy person, this stimulus will elicit a strong response over the primary
visual cortexThe term visual cortex refers to the primary visual cortex and extrastriate visual cortical areas such as V2, V3, V4, and V5. The primary visual cortex is anatomically equivalent to Brodmann area 17, or BA17...
located in the
occipital lobeThe occipital lobe is the visual processing center of the mammalian brain containing most of the anatomical region of the visual cortex. The primary visual cortex is Brodmann area 17, commonly called V1...
in the back of the brain.
Research ERP
Experimental psychologistsExperimental psychology is a methodological approach rather than a subject and encompasses varied fields within psychology. Experimental psychologists have traditionally conducted research, published articles, and taught classes on neuroscience, developmental psychology, sensation, perception,...
and
neuroscientistsNeuroscience is the scientific study of the nervous system. Such studies span the structure, function, evolutionary history, development, genetics, biochemistry, physiology, pharmacology, informatics, computational neuroscience and pathology of the nervous system.The International Brain Research...
have discovered many different stimuli that elicit reliable ERPs from participants. The timing of these responses is thought to provide a measure of the timing of the brain's communication or time of information processing. For example, in the checkerboard paradigm described above, in healthy participants the first response of the visual cortex is around 50-70 msec. This would seem to indicate that this is the amount of time it takes for the transduced visual stimulus to reach the
cortexThe cerebrum or telencephalon, together with the diencephalon, constitute the forebrain, along with the front lobe. It is the most anterior or, especially in humans, most superior region of the vertebrate central nervous system. "Telencephalon" refers to the embryonic structure, from which the...
after
lightLight is electromagnetic radiation, particularly radiation of a wavelength that is visible to the human eye ....
first enters the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
. Alternatively, the
P300The P300 wave is an event related potential which can be recorded via electroencephalography as a positive deflection in voltage at a latency of roughly 300 ms in the EEG. The signal is typically measured most strongly by the electrodes covering the parietal lobe...
response occurs at around 300ms regardless of the stimulus presented: visual, tactile,
auditorySound is a travelling wave which is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.- Perception of sound...
,
olfactoryOlfaction refers to the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
, gustatory, etc. Because of this general invariance in regard to stimulus type, this ERP is understood to reflect a higher cognitive response to unexpected and/or cognitively salient stimuli.
Due to the consistency of the P300 response to novel stimuli, a
brain-computer interfaceA brain–computer interface , sometimes called a direct neural interface or a brain–machine interface, is a direct communication pathway between a brain and an external device...
can be constructed which relies on it. By arranging many signals in a grid, randomly flashing the rows of the grid as in the previous paradigm, and observing the P300 responses of a subject staring at the grid, the subject may communicate which stimulus he is looking at, and thus slowly "type" words.
Other ERPs used frequently in research, especially
neurolinguistics researchNeurolinguistics is the study of the neural mechanisms in the human brain that control the comprehension, production, and acquisition of language. As an interdisciplinary field, neurolinguistics draws methodology and theory from fields such as neuroscience, linguistics, cognitive science,...
, include the ELAN, the N400, and the P600/SPS.
Further reading
- Steven J. Luck: An Introduction to the Event-Related Potential Technique. Cambridge, Mass.: The MIT Press, 2005. ISBN 0262621967
- Todd C. Handy: Event-Related Potentials : A Methods Handbook. Cambridge, Mass.: The MIT Press (B&T), 2004. ISBN 0262083337
- Monica Fabiani, Gabriele Gratton, and Kara D. Federmeier: Event-Related Brain Potentials : Methods, Theory, and Applications. In: Handbook of Psychophysiology / ed. by John T. Cacioppo, Louis G. Tassinary, and Gary G. Berntson. 3rd. ed. Cambridge: Cambridge University Press, 2007. ISBN 0-521-84471-0. pp. 85-119
- John Polich and Jody Corey-Bloom, Alzheimer's Disease and P300: Review and evaluation of Task and Modality. Current Alzheimer Research, 2005, 2, 515-525
See also
- Bereitschaftspotential
In neurology, the Bereitschaftspotential or BP , also called the pre-motor potential or readiness potential , is a measure of activity in the motor cortex of the brain leading up to voluntary muscle movement. The BP is a manifestation of cortical contribution to the pre-motor planning of volitional...
- Early left anterior negativity
The early left anterior negativity is an event-related potential in electroencephalography , or component of brain activity that occurs in response to a certain kind of stimulus...
- Erich Schröger
Erich Schröger is a German psychologist and neuroscientist.-Biography:Schröger studied philosophy and psychology at Ludwig Maximilians University in Munich. In 1982 he earned a Baccalaureat in Philosophy; in 1986 he earned a Diploma in Psychology; and in 1991 he was awarded a PhD for his work on...
- Evoked potential
An evoked potential is an electrical potential recorded from the nervous system of a human or other animal following presentation of a stimulus, as distinct from spontaneous potentials as detected by electroencephalography or electromyography .Evoked potential amplitudes tend to be low, ranging...
- Induced activity
The term induced activity is used in electroencephalography and magnetoencephalography for certain types of stimulus-related activity. The following explanation is for electroencephalographic activity, but the concept is the same in magnetoencephalography....
- P300 (neuroscience)
The P300 wave is an event related potential which can be recorded via electroencephalography as a positive deflection in voltage at a latency of roughly 300 ms in the EEG. The signal is typically measured most strongly by the electrodes covering the parietal lobe...
- Mismatch negativity
The mismatch negativity or mismatch field is a component of the event-related potential to an odd stimulus in a sequence of stimuli. It arises from electrical activity in the brain and is studied within the field of cognitive neuroscience and psychology. It can occur in any sensory system, but...
- N100
- N400