This dissertation reviews theoretical and empirical differences beween nouns and verbs, and presents several experiments that used ERPs ("Event-Related Potentials") to investigate brain processes during reading of nouns and verbs in English sentential contexts.

When word frequency and physical form of the nouns and verbs were matched (as in sentences like "The children paint ...." and "The children's paint ...."), verbs evoked consistently greater electrical positivity from 150-300 milliseconds post stimulus onset (the P2 epoch) and from 500-800 milliseconds (the P600 epoch).

In cases of syntactic anomaly (number disagreement, such as "The children smiles ...." and "One of the child's smile ....") anomalous nouns and verbs evoked increased left anterior negativity from about 50 to 500 milliseconds (a LAN effect), followed by an increased positivity from 500 to 800 milliseconds (a P600 effect). Relative to controls of their own classes, syntactic disagreement caused similar effects on nouns and verbs.

Semantic anomalies ("The wolf howls...." versus "The work howls ....") evoked increased negativity most prominent at posterior sites during the N400 epoch. Within syntactic categories, this effect was observed only for verbs, perhaps because the nouns appeared in the first phrase of the sentence while the verbs were in the second; anomalous nouns and verbs evoked similar ERPs to one another, but appropriate verbs evoked smaller N400 components than appropriate nouns.

Highly wordlike pseudowords in noun and verb contexts evoked increases in the N400 and P600 components relative to controls; N400 amplitude was comparable to that evoked by real but semantically anomalous words, and P600 effects were similar to those evoked by syntactic anomalies. ERPs were not affected by whether the pseudowords appeared in noun or verb positions within the sentences.