Papers selected by Satoko Ooba

　　　　■Electrophysiologcal localization of brain regions involved in perceptual memory
　　　　■Effect of subthreshold target stimuli on event-related potentials
　　　　■Neuronal correlates of subjective visual perception
　　　　■Distinguishing conscious from unconscious perceptual processes
　　　　■Affective discrimination of stimuli that are not recognized: Effects of shadowing, masking, and cerebral laterality

Electrophysiologcal localization of brain regions involved in perceptual memory

Reinvang I., Magnussen S., Greenlee M.W., & Larsson P.G.
Experimental Brain Research　Vol. 123(4),1998,481-484

Event-related potentials (ERP) were recorded during perceptual discrimination and short-term memory, varying the interstimulus interval (1-10 s) in delayed spatial frequency discrimination. Accuracy of discrimination remained unimpaired across this time interval, but choice reaction times increased. A brain source localization (BESA) model showed that the activity of the parietal and right temporal sources increased with long retention intervals in a sequential activation pattern where a long-latency component of the parietal source specific to the memory condition was observed, the latency of which matched a memory-related increase in choice reaction times in the cognitive task. It is suggested that the temporal sources are involved in encoding and storage of visual information, and the parietal source is involved in memory retrieval.

Effect of subthreshold target stimuli on event-related potentials

Milan Bra´zdil, Ivan Rektor a, Michal Dufek, Pavel Jura´k., & Pavel Daniel a.
Neurophysiology 107 (1998) 64−68

Abstract Objectives: Event-related potentials (ERPs) elicited by subthreshold visual stimuli were studied to assess the relationship between unconscious cognitive processing and the electrical activity of the brain. Methods: A new method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied. Prior to the experiment, the individual ‘subjective’ threshold for the conscious discrimination between frequent and target stimuli was established for each subject. Supraliminal and subliminal, frequent and target visual stimuli were then alternatively presented in random order to each subject. Results: Both the individual and the grand average ERPs revealed a typical response (P3) in the parietal region after supraliminally presented target stimuli. In subliminal conditions an analogous positive deflection in the central-parietal region was observed, which was elicited by the target stimulus, but not the frequent stimulus. Its latency could be clearly distinguished from the latency of the classical P3, the time difference between the two waveforms was approximately 100 ms.

Neuronal correlates of subjective visual perception

Logothetis N.K., Schall J.D.
SCIENCE Vol.245(4919) 1989,761-763

Neuronal activity in the superior temporal sulcus of monkeys, a cortical region that plays an important role in analyzing visual motion, was related to the subjective perception of movement during a visual task. Single neurons were recorded while monkeys (Macaca mulatta) discriminated the direction of motion of stimuli that could be seen moving in either of two directions during binocular rivalry. The activity of many neurons was dictated by the retinal stimulus. Other neurons, however, reflected the monkeys' receptor perception of motion direction, indicating that these neurons in the superior temporal sulcus may mediate the perceptual experience of a moving object.

Distinguishing conscious from unconscious perceptual processes

Cheesman,Jim Merikle,Philip M
Canadian Journal of Psychology. 1986 Dec Vol.40(4) 343-367.

Abstract Discusses the relationship between perceptual processing and awareness, based on a distinction between subjective and objective recognition thresholds. To test the proposed theoretical position that, since perceptual awareness is a subjective state, the subjective (for claimed awareness) threshold better captures the phenomenological distinction between conscious and unconscious processes than the objective threshold (based on discriminative responding), 3 experiments were conducted. The 3rd experiment provided, under slightly different conditions, empirical support for the findings of the 1st two. Exps I and II (with 16 college students and 16 19-29 yr old adults, respectively) used a Stroop-priming task. Results indicate that masked color words, presented above and below a subjective threshold, were effective primes for the subsequent naming of color patches and that the primes had qualitatively different effects.

Affective discrimination of stimuli that are not recognized: Effects of shadowing, masking, and cerebral laterality

Seamon,JohnG Brody,Nathan Kauff,David M
Journal of Experimental Psychology: Learning, Memory, and Cognition. 1983 Jul Vol .9(3) 544-555.

Four experiments with 142 undergraduates replicated and extended R. B. Zajonc's (see record 1980-09733-001) finding that mere exposure to a briefly presented stimulus can increase positive affect through familiarity without enhancing the recognition of that stimulus. Lateralized presentation of irregular polygon stimuli showed that affect judgments were best for stimuli presented in the right visual field (left hemisphere); recognition judgments were best for stimuli presented in the left visual field (right hemisphere). These effects were found only when stimuli were shown for 2 msec and were unmasked or for 5 msec and were pattern masked; when the stimuli were shown for 5 msec and were energy masked, target selection by affect or recognition was no greater than chance. These data, along with results from contingency probability analyses, indicate that affect and recognition judgments are different. Rather than viewing the difference between affect and recognition in terms of different features that might reside in the stimulus, the difference in judgments may reflect the manner in which a stimulus representation has been accessed. When viewed in terms of different retrieval processes that access different information, target selection by affect in the absence of recognition can be interpreted in terms of existing models of recognition memory.