Startle reflex modulation by pleasant and unpleasant odors in a between-subjects design.

Participants were presented with an acoustic startle probe while they smelled either a pleasant odor or an unpleasant odor (n = 40 per condition). Within each condition, participants were presented with four blocks in which odor was present and four in which odor was not present (no-odor control). Significant differences were found in both conditions between the odor and no-odor blocks. In the unpleasant odor condition, blink magnitude was greater during the odor blocks; in the pleasant odor condition, blink magnitude was smaller during the odor blocks.

Startle reflex modulation during exposure to pleasant and unpleasant odors.

The eyeblink component of the startle response to acoustic probes was measured while subjects smelled pleasant odors, unpleasant odors, or no odor. Peak electromyogram (EMG) 20-90 ms after probe onset was greater during unpleasant than during no odor conditions; EMGs for pleasant odors did not differ from those for no odor. Base tension in orbicularis oculi muscles was also higher during unpleasant odors. The results for unpleasant odors parallel those found in previous studies that have used a variety of methods for producing negatively valenced experiences. The results for pleasant odors diverge from those of most previous studies, which have found startle attenuation during positively valenced experiences. However, the results may be compatible with the suggestion (Lang, Bradley, & Cuthbert, 1992) that the motivational state that modulates startle involves both valence and arousal. Pleasant odors may require appropriate contexts to produce the positive motivational state required for startle attenuation.

Hedonic ratings of odors as a function of odor sequence in older adults.

Pleasant and unpleasant odors were presented to 20 subjects in two same-valence blocks, i.e., all pleasant ones first, all unpleasant ones second, or vice versa, and in alternation. Hedonic ratings increased for the second block of odors which followed the first block of oppositely valenced odors. Alternation did not appear to affect hedonic ratings. These findings suggest that presentation of odors can alter hedonic ratings, producing a contrast effect when odors are given in a blocked fashion.

Affect and memory: effects of pleasant and unpleasant odors on retrieval of happy and unhappy memories.

Interpretation of studies of induced mood and memory is complicated by the fact that mood induction procedures may elicit mood-related cognition in addition to mood per se. We used odors to produce positive and negative experiences with minimal cognitive involvement. College women recalled memories cued by neutral words while exposed to a pleasant odor, unpleasant odor, or no odor. Subjects then rated their memories as to how happy or unhappy the events recalled were at the time they occurred. Subjects in the pleasant odor condition produced a significantly greater percentage of happy memories than did subjects in the unpleasant odor condition. When subjects who did not find the odors at least moderately pleasant or unpleasant were removed from the analysis, more pronounced effects on memory were found. The results suggest that congruence between the general hedonic tone of current experience and that of material in long-term memory is sufficient to bias retrieval.

EEG asymmetry and sleep mentation during REM and NREM.

The hypothesis that dreaming is mediated by the right hemisphere was evaluated by monitoring EEG power asymmetry during REM and NREM sleep, and obtaining mentation reports when short-term temporal shifts in the EEG indicated relative left- or right-hemispheric dominance. Content analyses provided no support for the right-hemisphere hypothesis; indeed, some scales showed higher content during relative left-hemispheric dominance. In contrast to earlier reports, no difference between REM and NREM in EEG asymmetry was observed.

Right hemispheric specialization for mental imagery: a review of the evidence.

An implicit assumption in the literature on functional hemispheric asymmetry is that the right hemisphere plays a special role in mental imagery. Using a definition of mental imagery as quasi-perceptual experience, we draw distinctions among visual imagery, visual recognition memory, and visuospatial abilities. We then review the research literature to evaluate the hypothesis that mental imagery is a specialized function of the right cerebral hemisphere, and find that it receives little unambiguous support. Case reports of loss of imagery are no more frequent with right than with left unilateral brain damage. Systematic studies of brain-injured patients provide some support for the hypothesis, but are also consistent with the alternative hypothesis of bilateral representation of imagery. Commissurotomized patients report dreaming and being able to form visual images. Behavioral and psychophysiological studies of non-brain-injured patients either fail to provide evidence in favor of the hypothesis or can be interpreted as compatible with the alternate hypothesis of bilateral hemispheric involvement in imagery. We conclude that there is, presently, insufficient empirical basis for considering imagery a right hemispheric function. We then discuss implications of this conclusion for future research.

Perinatal factors in hand and eye preference: data from the Collaborative Perinatal Project.

Data from 5,899 girls and boys who participated in the NIH Collaborative Perinatal Project were analyzed for relationships between birth order and birth stress and hand and eye preference as measured at age seven. None of the birth variables were significantly related to hand preference at the 0.05 level for either boys or girls. However, left eye preference was related to birth stress in boys. When both sexes were combined, left eye preference was also associated with low and high birthweight, and also with right lateral position of the head in the maternal pelvis.

Bilateral hemispheric alpha activity during visual imagery.

Subjects responded to questions designed to be answered with or without accompanying visual imagery, while saccadic eye movements and temporoparietal EEG were recorded. Findings of suppressed eye-movement rate and suppressed alpha output during response to the high-imagery questions were interpreted as evidence of the presence of visual imagery. However, the interaction between Question Type and Hemisphere was not significant, indicating equal effect of visual imagery on alpha activity in the two hemispheres, contrary to the popular belief that visual imagery is a function of the right cerebral hemisphere.

EEG asymmetries in recognition of faces: comparison with a tachistoscopic technique.

Twelve field-dependent and twelve field-independent women, who had previously shown opposite superiorities in a tachistoscopic face recognition task, returned to the laboratory for a session in which FEG asymmetry was measured during two facial and two verbal recognition tasks. Although task-related EEG asymmetries were observed, there was no effect of cognitive style on either direction or amount of asymmetry. These results suggest a lack of comparability among different methods of assessing individual differences in lateral functions.

Field independence and laterality in the perception of faces.

For a sample of 28 college males the degree of left visual-field bias in the perception of faces correlated .45 (p less than .01) with extent of field-independent performance, as assessed by a composite score based on the Embedded-Figures Test, the Rod-and-Frame Test, and ratings on the Articulation-of-Body-Concept Scale. In a second study with 16 female and 10 male college subjects using the Group Embedded-Figures Test, field-independent subjects again showed greater left visual-field lateralization of face perception (r = .43, p less than .05). Based on Witkin's view of field independence as a manifestation of psychological differentiation, possible links between extent of differentiation at the psychological and neurophysiological levels are suggested.

Field-dependence-independence and lateral eye movements following verbal and spatial questions.

In three studies a small positive relationship was found between field-dependent cognitive style and the tendency to give a higher percentage of right lateral eye movements to verbal than to spatial questions. However, in only one of the three studies was the relationship significant (r = .32, n = 52). It is concluded that differences among samples in cognitive style probably cannot account for different patterns of results in studies of lateral eye movement.