N400

Definition

The N400 is an event-related potential (ERP) component that is observed in EEG recordings, typically peaking around 400 milliseconds after the presentation of a meaningful stimulus. It is primarily associated with semantic processing, particularly in response to words or sentences that violate expectations or contain incongruent information. The N400 provides valuable insights into how the brain processes language and meaning, and its amplitude is often modulated by contextual factors and the predictability of upcoming words.

5 Must Know Facts For Your Next Test

1. The N400 is most commonly elicited by words that are semantically incongruent with their preceding context, such as 'He took a bite of the sandwich and then began to fly.'
2. The amplitude of the N400 is inversely related to the predictability of a word; less predictable words generate larger N400 responses.
3. N400 responses can be observed not just with words, but also with pictures and other visual stimuli that violate semantic expectations.
4. Different languages exhibit N400 effects, indicating that this component is crucial for understanding language processing across diverse linguistic systems.
5. Clinical studies have shown that patients with certain neurological disorders may exhibit altered N400 responses, helping researchers understand language impairments.

Review Questions

• How does the N400 reflect semantic processing in the brain, and what does it indicate about language comprehension?
  • The N400 reflects semantic processing by showing increased brain activity when individuals encounter words or phrases that do not fit the expected meaning based on prior context. This suggests that the brain actively predicts and evaluates incoming information for coherence, which is essential for effective language comprehension. An increased N400 amplitude indicates a higher cognitive load required to process unexpected or incongruent stimuli.
• Discuss how the amplitude of the N400 can be influenced by contextual factors in language processing.
  • The amplitude of the N400 can be influenced by several contextual factors, including word predictability and sentence structure. For instance, if a word is expected based on prior context, its N400 response will be smaller compared to a word that is surprising or unexpected. This modulation demonstrates how context shapes our understanding of language and highlights the brain's ability to integrate contextual clues during comprehension.
• Evaluate the significance of the N400 in understanding linguistic processing across different languages and its implications for studying language disorders.
  • The significance of the N400 lies in its ability to provide insights into linguistic processing across various languages, indicating that this ERP component is a fundamental aspect of how humans understand meaning. Its presence in different linguistic contexts supports theories about universal principles in language comprehension. Moreover, studying N400 responses in individuals with language disorders can reveal specific deficits in semantic processing, guiding interventions and therapies aimed at improving communication abilities.

Related terms

Event-Related Potential (ERP): An ERP is a measured brain response that is directly the result of a specific sensory, cognitive, or motor event, often studied using EEG.

Semantic Processing: The cognitive process by which individuals comprehend the meanings of words and sentences, playing a crucial role in language understanding.

P300: The P300 is another ERP component that appears roughly 300 milliseconds after stimulus presentation and is associated with attention and the processing of unexpected or significant stimuli.