P600
Encyclopedia
The P600 is an event-related potential
(ERP), or peak in electrical brain activity measured by electroencephalography
(EEG). It is a language-relevant ERP and is thought to be elicited by hearing or reading grammatical
errors and other syntactic
anomalies. Therefore, it is a common topic of study in neurolinguistic experiments investigating sentence processing in the human brain.
The P600 can be elicited in both visual (reading) and auditory (listening) experiments, and is characterized as a positive-going deflection with an onset around 500 milliseconds after the stimulus that elicits it; it often reaches its peak around 600 milliseconds after presentation of the stimulus (hence its name), and lasts several hundred milliseconds.Different authors give slightly different time periods for the P600; for example, claim it may start as early as 400 milliseconds, and describes it as occurring "between 600–1000 ms. In other words, in the EEG waveform it is a large peak in the positive direction, which starts around 500 milliseconds after the subject sees or hears a stimulus. It is typically thought of as appearing mostly on centro-parietal
electrodes (i.e., over the posterior part of the center of the scalp), but frontal P600s have also been observed in several studies. In EEG, however, this distribution at the scalp does not mean the P600 is coming from that part of the brain; a 2007 study using magnetoencephalography
(MEG) speculates that the generators of the P600 in the posterior temporal lobe
, behind Wernicke's area
.
The P600 was first reported by Lee Osterhout and Phillip Holcomb in 1992. It is also sometimes called the Syntactic Positive Shift (SPS), since it has a positive polarity and is usually elicited by syntactic phenomena.
s, and the processing of filler-gap dependencies (such as wh-words that appear at the beginning of a sentence in English
but are actually interpreted somewhere else).
Grammatical errors
A P600 may be elicited by several kinds of grammatical errors in sentences, such as problems in agreement
, such as "the child *throw the toy". In addition to this sort of subject-verb disagreement, P600s have also been elicited by disagreements in tense
, gender
, number
, and case
, as well as phrase structure violations. A 2009 study has suggested that these errors elicit stronger P600s than the other syntactic stimuli that have been implicated.
Garden paths
P600s are also known to occur when a sentence contains no outright grammatical error, but must be parsed in a different way than the reader originally expects. These sentences are known as "garden path" sentences, because the reader follows one interpretation of the sentence only to realize later that this interpretation was wrong and he must backtrack to understand the sentence. For example, found P600s elicited by the word to in sentences such as
Syntactic errors in music
P600s are also elicited by errors in musical harmony, such as when a chord is played out of key with the rest of a musical phrase. This implies that P600s are not "language-specific," but "can be elicited in nonlinguistic (but rule-governed) sequences."
Dependencies and complexity
Some studies have found a P600 elicited by words where there is no grammatical error and no "garden path" (i.e., where the word is exactly what the reader would expect), but when the sentence is complex because there are a number of noun phrase
s active. This has most often been the case when the reader has to "re-activate" a word that appeared earlier in the sentence. For example, in a sentence like "Who did you imitate?", the word who appears in the beginning of the sentence but is actually the direct object of imitate, and must be interpreted in that way (i.e., as "you imitated who?"); several studies have found that after the reader sees the word imitate he or she has a P600 response, possibly as a result of re-activating who. These sorts of P600s get stronger as the number of noun phrases active in the sentences increases, suggesting that the P600 generator is sensitive to the level of complexity in a sentence.
Semantic attraction
demonstrated a so-called "semantic P600" in sentences that are grammatically correct but semantically anomalous, and in which syntactic reanalysis is more appealing than semantic reanalysis. For example, a P600 may be elicited in the following sentence:
in that it is triggered when a subject encounters "improbable" stimuli—since ungrammatical sentences are relatively rare in natural speech, a P600 may not be a linguistic response but simply an effect of the subject's "surprise" upon encountering an unexpected stimulus.
Event-related potential
An event-related potential is any measured brain response that is directly the result of a thought or perception. More formally, it is any stereotyped electrophysiological response to an internal or external stimulus....
(ERP), or peak in electrical brain activity measured by electroencephalography
Electroencephalography
Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...
(EEG). It is a language-relevant ERP and is thought to be elicited by hearing or reading grammatical
Grammaticality
In theoretical linguistics, grammaticality is the quality of a linguistic utterance of being grammatically well-formed. An * before a form is a mark that the cited form is ungrammatical....
errors and other syntactic
Syntax
In linguistics, syntax is the study of the principles and rules for constructing phrases and sentences in natural languages....
anomalies. Therefore, it is a common topic of study in neurolinguistic experiments investigating sentence processing in the human brain.
The P600 can be elicited in both visual (reading) and auditory (listening) experiments, and is characterized as a positive-going deflection with an onset around 500 milliseconds after the stimulus that elicits it; it often reaches its peak around 600 milliseconds after presentation of the stimulus (hence its name), and lasts several hundred milliseconds.Different authors give slightly different time periods for the P600; for example, claim it may start as early as 400 milliseconds, and describes it as occurring "between 600–1000 ms. In other words, in the EEG waveform it is a large peak in the positive direction, which starts around 500 milliseconds after the subject sees or hears a stimulus. It is typically thought of as appearing mostly on centro-parietal
Parietal lobe
The parietal lobe is a part of the Brain positioned above the occipital lobe and behind the frontal lobe.The parietal lobe integrates sensory information from different modalities, particularly determining spatial sense and navigation. For example, it comprises somatosensory cortex and the...
electrodes (i.e., over the posterior part of the center of the scalp), but frontal P600s have also been observed in several studies. In EEG, however, this distribution at the scalp does not mean the P600 is coming from that part of the brain; a 2007 study using magnetoencephalography
Magnetoencephalography
Magnetoencephalography is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs...
(MEG) speculates that the generators of the P600 in the posterior temporal lobe
Temporal lobe
The temporal lobe is a region of the cerebral cortex that is located beneath the Sylvian fissure on both cerebral hemispheres of the mammalian brain....
, behind Wernicke's area
Wernicke's area
Wernicke's area is one of the two parts of the cerebral cortex linked since the late nineteenth century to speech . It is involved in the understanding of written and spoken language...
.
The P600 was first reported by Lee Osterhout and Phillip Holcomb in 1992. It is also sometimes called the Syntactic Positive Shift (SPS), since it has a positive polarity and is usually elicited by syntactic phenomena.
Elicitation
The P600 was originally considered a "syntactic" ERP, and therefore is elicited by several types of syntactic phenomena, including ungrammatical stimuli, garden path sentences that require reanalysis, complex sentences with a large number of thematic roleThematic role
Thematic role is a linguistic notion, which may refer to:* Theta role * Thematic relation...
s, and the processing of filler-gap dependencies (such as wh-words that appear at the beginning of a sentence in English
English language
English is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
but are actually interpreted somewhere else).
Grammatical errors
A P600 may be elicited by several kinds of grammatical errors in sentences, such as problems in agreement
Agreement (linguistics)
In languages, agreement or concord is a form of cross-reference between different parts of a sentence or phrase. Agreement happens when a word changes form depending on the other words to which it relates....
, such as "the child *throw the toy". In addition to this sort of subject-verb disagreement, P600s have also been elicited by disagreements in tense
Grammatical tense
A tense is a grammatical category that locates a situation in time, to indicate when the situation takes place.Bernard Comrie, Aspect, 1976:6:...
, gender
Grammatical gender
Grammatical gender is defined linguistically as a system of classes of nouns which trigger specific types of inflections in associated words, such as adjectives, verbs and others. For a system of noun classes to be a gender system, every noun must belong to one of the classes and there should be...
, number
Grammatical number
In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....
, and case
Grammatical case
In grammar, the case of a noun or pronoun is an inflectional form that indicates its grammatical function in a phrase, clause, or sentence. For example, a pronoun may play the role of subject , of direct object , or of possessor...
, as well as phrase structure violations. A 2009 study has suggested that these errors elicit stronger P600s than the other syntactic stimuli that have been implicated.
Garden paths
P600s are also known to occur when a sentence contains no outright grammatical error, but must be parsed in a different way than the reader originally expects. These sentences are known as "garden path" sentences, because the reader follows one interpretation of the sentence only to realize later that this interpretation was wrong and he must backtrack to understand the sentence. For example, found P600s elicited by the word to in sentences such as
The broker persuaded to sell the stock was tall.In sentences such as this, the preferred reading is to interpret "persuaded" as the main verb of the sentence (i.e., "the broker persuaded me"), and upon seeing the word to the reader has to re-analyze the sentence to mean something more like "the broker that was persuaded to sell the stock, he was tall".
Syntactic errors in music
P600s are also elicited by errors in musical harmony, such as when a chord is played out of key with the rest of a musical phrase. This implies that P600s are not "language-specific," but "can be elicited in nonlinguistic (but rule-governed) sequences."
Dependencies and complexity
Some studies have found a P600 elicited by words where there is no grammatical error and no "garden path" (i.e., where the word is exactly what the reader would expect), but when the sentence is complex because there are a number of noun phrase
Noun phrase
In grammar, a noun phrase, nominal phrase, or nominal group is a phrase based on a noun, pronoun, or other noun-like word optionally accompanied by modifiers such as adjectives....
s active. This has most often been the case when the reader has to "re-activate" a word that appeared earlier in the sentence. For example, in a sentence like "Who did you imitate?", the word who appears in the beginning of the sentence but is actually the direct object of imitate, and must be interpreted in that way (i.e., as "you imitated who?"); several studies have found that after the reader sees the word imitate he or she has a P600 response, possibly as a result of re-activating who. These sorts of P600s get stronger as the number of noun phrases active in the sentences increases, suggesting that the P600 generator is sensitive to the level of complexity in a sentence.
Semantic attraction
demonstrated a so-called "semantic P600" in sentences that are grammatically correct but semantically anomalous, and in which syntactic reanalysis is more appealing than semantic reanalysis. For example, a P600 may be elicited in the following sentence:
The hearty meal was devouring the kids.This suggests that the reader would rather interpret the sentence as containing a morphosyntactic error (saying "devouring" instead of "devoured by") rather than a semantic one (meals can't devour kids, but can be devoured by them). The interpretation of "semantic P600s" has attracted considerable attention and controversy in the literature.
Interpretations
There are several theories about what computational processes the P600 may be triggered by. Because it often happens in response to grammatical violations or garden path sentences, one theory is that the P600 reflects processes of revision (i.e., trying to "rescue" the interpretation of a sentence that can't be processed normally because of structural errors) and reanalysis (i.e., trying to rearrange the structure of a sentence that has been interpreted incorrectly because of a garden path). On the other hand, other models suggest that the P600 may not reflect these processes in particular, but just the amount of time and effort in general it takes to build up coherent structure in a sentence, or the general processes of creating or destroying syntactic structure (not specifically because of repair). Another proposal is that the P600 does not necessarily reflect any linguistic processes per se, but is similar to the P300P300 (neuroscience)
The P300 wave is an event related potential elicited by infrequent, task-relevant stimuli. It is considered to be an endogenous potential as its occurrence links not to the physical attributes of a stimulus but to a person's reaction to the stimulus. More specifically, the P300 is thought to...
in that it is triggered when a subject encounters "improbable" stimuli—since ungrammatical sentences are relatively rare in natural speech, a P600 may not be a linguistic response but simply an effect of the subject's "surprise" upon encountering an unexpected stimulus.
See also
- Somatosensory evoked potentialSomatosensory Evoked PotentialSomatosensory Evoked Potentials are a useful, noninvasive means of assessing somatosensory system functioning. By combining SEP recordings at different levels of the somatosensory pathways, it is possible to assess the transmission of the afferent volley from the periphery up to the cortex...
- C1 and P1C1 & P1 (Neuroscience)The C1 and P1 are two human scalp-recorded event-related brain potential components, collected by means of a technique called electroencephalography . The C1 is named so because it was the first component in a series of components found to respond to visual stimuli when it was first discovered...
- Visual N1Visual N1The Visual N1 is a visual evoked potential, a type of event-related electrical potential , that is produced in the brain and recorded on the scalp. The N1 is so named to reflect the polarity and typical timing of the component. The "N" indicates that the polarity of the component is negative with...
- Mismatch negativityMismatch negativityThe 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
- N200N200 (neuroscience)The N200, or N2, is an event-related potential component. An ERP can be monitored using a non-invasive electroencephalography cap that is fitted over the scalp on human subjects...
- N2pcN2pcN2pc refers to an ERP component linked to selective attention. The N2pc appears over visual cortex contralateral to the location in space to which subjects are attending; if subjects pay attention to the left side of the visual field, the N2pc appears in the right hemisphere of the brain, and...
- N170N170The N170 is a component of the event-related potential that reflects the neural processing of faces.When potentials evoked by images of faces are compared to those elicited by other visual stimuli, the former show increased negativity 130-200 ms after stimulus presentation...
- P200P200In neuroscience, the visual P200 or P2 is a waveform component or feature of the event-related potential measured at the human scalp. Like other potential changes measurable from the scalp, this effect is believed to reflect the post-synaptic activity of a specific neural process...
- N400
- P300 (neuroscience)P300 (neuroscience)The P300 wave is an event related potential elicited by infrequent, task-relevant stimuli. It is considered to be an endogenous potential as its occurrence links not to the physical attributes of a stimulus but to a person's reaction to the stimulus. More specifically, the P300 is thought to...
- P3aP3aThe P3a, or novelty P3, is a component of time-locked signals known as event-related potentials . The P3a is a positive-going scalp-recorded brain potential that has a maximum amplitude over frontal/central electrode sites with a peak latency falling in the range of 250-280 ms...
- P3bP3bThe P3b is a subcomponent of the P300, an event-related potential component that can be observed in human scalp recordings of brain electrical activity...
- Late Positive ComponentLate Positive ComponentThe LPC is a positive-going event-related brain potential component that has been important in studies of explicit recognition memory...
- Difference due to MemoryDifference due to MemoryDifference due to Memory indexes differences in neural activity during the study phase of an experiment for items that subsequently are remembered compared to items that are later forgotten...
- Contingent negative variationContingent negative variationThe contingent negative variation was one of the first event-related potential components to be described. The CNV component was first described by Dr. W. Grey Walter and colleagues in an article published in Nature in 1964...
- Error-related negativityError-related negativityError-related negativity , , is a component of an event-related potential . ERPs are electrical activity in the brain as measured through electroencephalography and time-locked to an external event...
- BereitschaftspotentialBereitschaftspotentialIn 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...
- Lateralized readiness potentialLateralized readiness potentialIn neuroscience, the lateralized readiness potential is an event-related brain potential, or increase in electrical activity at the surface of the brain, that is thought to reflect the preparation of motor activity on a certain side of the body; in other words, it is a spike in the electrical...
- Early left anterior negativityEarly 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...