Effects of consciousness on human brain waves following binocular rivalry.

When the two eyes of an observer are exposed to conflicting stimuli, they enter into binocular rivalry and the two possible percepts will alternate in dominance. We investigated neural activity and its time course following binocular rivalry by measuring human event-related brain potentials to transitions from rivalrous to non-rivalrous stimulation. When these changes did not entail a change in conscious perception they elicited a markedly attenuated N1 component and a delayed and attenuated P3 peak as compared to percept-incompatible changes and non-rivalrous control conditions. These results suggest that in humans binocular rivalry is resolved at latest in extrastriate visual areas.

Facilitation of visual search at new positions: a behavioral and ERP study of new object capture.

Visual search was studied in two consecutive displays. Display 1 items changed identity whilst retaining their positions when the additional items appeared in Display 2. In the New condition, the target appeared at one of the new positions, whereas in the Old condition, the target appeared at one of the old positions. Responses were faster and accuracy increased in the New condition. Event-related brain potentials revealed an Old-New difference 400 ms after Display 2 onset for the smaller set size, suggesting that subjects had a holistic impression that the target was absent at a new position. A posteriorly distributed processing difference between both conditions was manifest at around 1200 ms, suggesting a bias for search at new positions.

Retrieval latency and "at-risk" memories.

Does retrieval latency reflect variations in the strength of associations in episodic memory? In three experiments, subjects were given a single study and test trial on each of five lists of 10 paired associates. Spoken recall latencies were measured. When the subjects were later given a second test, initial recall latency was systematically related to intertest retention--that is, the faster the initial correct recall of a pair, the more likely a pair was to be recalled at the second test. This effect occurred at retention intervals of 5 min, 30 min, and 24 h and was present in the data for individual subjects. The results are consistent with the classical view of latency as a measure of trace strength and stand in sharp contrast with results reported by Benjamin, Bjork, and Schwartz (1998) that showed that fast retrievals from semantic memory were more poorly retained than slower ones.