The effects of soy milk and isoflavone supplements on cognitive performance in healthy, postmenopausal women.

RATIONALE: The decline in estrogen concentrations in women after menopause can contribute to health related changes including impairments in cognition, especially memory. Because of the health concerns related to hormone replacement therapy (HRT), alternative approaches to treat menopausal symptoms, such as nutritional supplements and/or diet containing isoflavones, are of interest. OBJECTIVES: This study investigated whether soy isoflavones (soy milk and supplement) could improve cognitive functioning in healthy, postmenopausal women. PARTICIPANTS, INTERVENTION AND DESIGN: A total of 79 postmenopausal women, 48-65 years of age, completed a double-blind, placebo-controlled trial in which they were randomly assigned to one of three experimental groups: cow's milk and a placebo supplement (control); soy milk and placebo supplement (soy milk, 72 mg isoflavones/day); or cow's milk and isoflavone supplement (isoflavone supplement, 70 mg isoflavones/day). MEASUREMENTS: Cognitive functioning was assessed using various cognitive tasks before the intervention (baseline) and after the intervention (test). RESULTS: In contrast to predictions, soy isoflavones did not improve selective attention (Stroop task), visual long-term memory (pattern recognition), short-term visuospatial memory (Benton Visual Retention Test), or visuo-spatial working memory (color match task). Also, the soy milk group showed a decline in verbal working memory (Digit Ordering Task) compared to the soy supplement and control groups. CONCLUSION: Soy isoflavones consumed as a food or supplement over a 16-week period did not improve or appreciably affect cognitive functioning in healthy, postmenopausal women.

Is evidence for late selection due to automatic or attentional processing of stimulus identities?

This study determined whether evidence for late selection is due to attention processing or to processing by an automatic system that is separate from attention (two systems framework; Eriksen, Webb, & Fournier, 1990). The task was a two-choice discrimination of a target that appeared in one of two sequentially cued locations in an eight-letter visual display. Attention was directed to the first cued location (cue 1), and whether identification processing occurred at a different location before the second cue (cue 2) directed attention there was determined. Cue validity varied across two experiments, and critical trials were those in which the target appeared at cue 2. For these trials, the target was preceded by a letter (either identical, neutral, or incompatible) that changed to the target at various time intervals following cue 2. Automatic identification was assumed if the incompatible letter interfered with response to the target when it appeared only before cue 2 onset and independent of cue validity. The incompatible letter appearing only before cue 2 onset interfered with the target when the target occurred equally often at cue 1 and cue 2, but not when the target occurred at cue 1 70% and at cue 2 30% of the time. This disconfirms the two systems framework and suggests that attention is required for spatial form processing and response competition.

When complexity helps: an electrophysiological analysis of multiple feature benefits in object perception.

Fournier, L. R., Eriksen, C. W. and Bowd, C. (1998. Multiple feature discrimination faster than single feature discrimination within the same object? Perception & Psychophysics 60, 1384-1405) found that judging the presence of multiple features within an object is faster than judging the presence of the least discriminable of these features alone (multiple feature benefits, MFBs). When an 'absent' response is required, responses are slower when some of the relevant (target) features are present (multiple feature costs, MFCs). The present study utilized psychophysiological measures (of the event-related brain potential and the electromyogram) to determine the contributions of response priming and stimulus evaluation processes (P300 latency) to these effects. P300 latency and reaction time (RT) both showed evidence of MFBs and MFCs. These findings suggest that MFBs and MFCs can be attributed to processing that occurs prior to response selection. No dissociations between P300 latency and RT measures were found for 'present' responses across the single and multiple feature judgements. However, for 'absent' responses, partial dissociations were found between these measures, and partial errors and longer response execution intervals were observed more often when an object contained some target features. These findings suggest that response priming contributes to MFCs, but may not contribute to MFBs.

Interference from multi-dimensional objects during feature and conjunction discriminations.

Feature discrimination performance within an attended object and interference from irrelevant, multi-dimensional objects (distractors) were examined in a two-choice, response compatibility paradigm. Results showed that the amount of interference by multi-dimensional distractors was dependent on three factors: (1) the discriminability of the incompatible, task-relevant distractor features; (2) the number of incompatible, task-relevant distractor features; and (3) whether the task-relevant, incompatible features matched the task goals. The most interesting finding was that additive priming effects were found for multiple, task-relevant features that matched the task goals, whether these features were present in the attended object or in the ignored object. Models that assume that each task-relevant feature primes its corresponding decision/response asynchronously and that this priming is combined to meet a decision/response criterion (at least when attended) can account for distractor interference during conjunction discriminations. Implications of these findings for feature integration models, template models, and a response selection model are discussed.

Electrophysiological, behavioral, and subjective indexes of workload when performing multiple tasks: manipulations of task difficulty and training.

This study examined whether alpha event-related desynchronization (ERD) and theta event-related synchronization (ERS) could successfully measure changes in cognitive workload and training while an operator was engaged in a continuous, interactive, control task(s). Alpha 1 (8-10 Hz) ERD, alpha 2 (10-12 Hz) ERD, and theta (3-7 Hz) ERS were determined for a communications event that occurred during multiple task workload conditions or as a single task. Other measures (alpha and theta EEG power, heart rate, respiration, eye blinks, behavioral performance, and subjective workload ratings) were also evaluated. Results showed that alpha 2 EEG, heart rate, behavioral, and subjective measures were sensitive to changes in workload in the multiple tasks. In addition, eye blink rate and behavioral measures were sensitive to training. Alpha ERD and theta ERS were not sensitive to workload and training in our interactive, multiple task environment. However, they were effective indexes of cognitive/behavioral demands within an interactive single task.

Multiple-feature discrimination faster than single-feature discrimination within the same object?

In the present study, we investigated whether judging the presence of multiple features within an object would be superior to judging the presence of only one feature. Feature discriminability and the number of features to discriminate within an object were varied. Specific features were judged as present or absent. Results showed that judging the presence of two or three features was faster than judging the presence of the less discriminable of these two or three features alone (multiple-feature benefits). These findings suggest that relevant features within an object activate (prime) a decision or response in a parallel, asynchronous fashion based on discriminability (Miller, 1982a). The ability of a response priming model, a response mapping model, and a template model to account for multiple-feature benefits is discussed.

The dimensionality of the flanker compatibility effect: a psychophysiological analysis.

The psychophysiological approach was used to evaluate the effects of feature similarity and "intrinsic response mapping" on the flanker compatibility effect. Symbol (e.g., < > < and

Selective attentional delays and attentional capture among simultaneous visual onset elements.

Visual discrimination and detection responses to a single stimulus presented simultaneously with noise stimuli are slower and less accurate than are responses to a single stimulus presented alone. This occurs even though the location of the relevant stimulus (target) is known or visually indicated with stimuli onset. Results showed that noise elements delay focal attending and processing of a target. Furthermore, precuing the target location reduces, and can eliminate, target processing delays. Processing delays were not due to response competition or to random attentional capture by noise. It is suggested that simultaneous stimuli are perceived initially as a single object, and delays in processing a single stimulus are due to difficulties in perceptually segregating this stimulus from noise. Precuing is assumed to facilitate this segregation process.

Coactivation in the perception of redundant targets.

Reaction time (RT) to redundant stimuli was investigated while controlling for distraction effects and response competition. In Experiment 1, a redundancy gain was found for 2 target letters with identical features (redundant) compared to trials in which 2 different targets shared the same response assignment (compatible) indicating coactivation of stimulus inputs. No difference in RTs was found between compatible displays and displays containing 2 targets with different responses (incompatible), suggesting (with other evidence) that letters were serially processed. In Experiment 2, a redundancy gain was again found. Unlike in Experiment 1, incompatible displays produced response competition, indicating a redundancy gain with parallel processing. Three forms of redundancy gains operating under specific conditions are discussed.

How much processing do nonattended stimuli receive? Apparently very little, but....

The early versus late selection issue in attention models was examined by means of a new methodology. Through cues or precues, attention was directed to one location of a multistimulus visual display and, while attention was so engaged, the identity of a stimulus located at a different position in the display was changed. By varying the time after display onset before the stimulus was changed, we controlled the preview time that the original stimulus was represented on the retina. Then, using a marker cue, we directed the subject's attention to the location of the changed stimulus. The subject's response was a timed discrimination between two possible target letters. The data of main interest was the effect of preview time upon the subject's latency in identifying the new target that appeared in the changed location. We found that the preview time of the original stimulus, before RT was affected to the new target, depended upon whether the original stimulus was a neutral (noise) letter or whether it was the alternative target. When the original stimulus was a noise letter, RTs to the new target were just as fast as those obtained in the control condition in which the target was present throughout the preview interval and did not change its identity. Significant effects upon RT were obtained at preview times of 83 msec when the original stimulus was one of the targets that changed to the alternative target. Preview times also varied as a function of precuing. Preview times were correspondingly shortened when the first cue occurred 50 msec before display onset, thus providing an extra 50 msec for attention to be directed to the first display location. The results were interpreted in terms of two separate information-processing systems in the human: an automatic system and an attentional system. Even though a stimulus may have been automatically processed, when the attention system is directed to that stimulus, processing starts at the beginning again.

Processing redundant signals: coactivation, divided attention, or what?

The evidence for and against a redundancy gain in reaction time (RT) when the target is repeated in the visual display is reviewed. We consider the relevance of redundancy gains under these circumstances to the question of whether attention can be simultaneously directed to separate locations in the visual field. In the present experiments, two capital letters were the target stimuli in a two-alternative forced-choice RT paradigm. In addition to the usual conditions of single-target trials, trials on which the target is repeated in the display, and trials on which the target occurs with a noise letter, we introduced the innovation of a condition in which both targets occur in the display. In our two experiments, RT was fastest with single-target displays and slowest with displays containing a target and a noise letter. There was no significant difference in RT to displays in which the target was repeated and displays in which both targets were presented. Both conditions showed a redundancy gain when compared with displays containing a target and a noise letter. The lack of response competition in the both-targets condition and the overall pattern of the results were well explained by a unitary attentional focus that serially processed the letters in the display. Analyses of minima and maxima RTs were consistent with this interpretation.