Late negativity in visual evoked potentials in humans to changes in the topology of simple nonverbal stimuli.

Late negativity arising in evoked potentials to semantic mismatching of sequentially presented stimuli is usually linked with verbal or symbolic representations of stimuli during the process of perception. The present studies showed that the late negativity characteristic of semantic mismatch arises even in the context of non-symbolic and nonverbal stimuli, for example, stimuli consisting of four points differing only in terms of topology or angular size. Distraction of attention from the test stimuli completely eliminated the late negativity effect. It is suggested that any stimulus composition can have semantic (meaning) and formal (shape, pattern) descriptions which, when stimuli are compared using the oddball paradigm, result in various levels of the N400 component depending on the amount of attention paid to the stimuli themselves.