Evaluation of a psychophysiologically controlled adaptive automation system, using performance on a tracking task.

Three experiments were conducted to evaluate the performance of a psychophysiologically controlled adaptive automation system. Subjects were asked to perform a compensatory tracking task while their electroencephalogram (EEG) was recorded and an engagement index was derived from the EEG, using the alpha, beta, and theta bandwidths: beta/(alpha + theta) and beta/theta. In Experiment I, EEG was recorded from three different sites: frontal, parietal, and temporal. Although tracking performance did not differ as a function of site, the number of task mode allocations was greater under a negative feedback contingency than under a positive feedback contingency. This effect was seen primarily from frontal sites. Experiments II and III evaluated the adaptive automation system, using extended runs under positive and negative feedback with either a slope (Experiment II) or absolute (Experiment III) criterion used to drive the system. Using either criterion, performance was found to be significantly better under negative feedback. Future evaluation and use of psychophysiologically controlled adaptive automation systems are discussed.

Driving simulation with EEG monitoring in normal and obstructive sleep apnea patients.

STUDY OBJECTIVES: To measure simulated driving performance in obstructive sleep apnea patients and its relationship with EEG defined attention lapses. DESIGN: Prospective, mixed design comparing apnea patients and control subjects over a 60-minute driving simulation task while continuously recording both driving performance and EEG measures. SETTING: Sleep disorders center. PARTICIPANTS: 15 polysomnographically diagnosed obstructive sleep apnea patients (mean age 42 +/- 6 yrs.) and 15 healthy volunteers (mean age 38 +/- 6 yrs.). INTERVENTIONS: NA. MEASUREMENTS AND RESULTS: A computer based driving simulator recorded lane position variability, speed variability, steering rate variability, and crash frequency. The frequency and duration of EEG-defined attention lapses were also measured. The results demonstrated that the apnea group had significantly greater variability in lane position, steering rate, and speed than the control group. The apnea group also had more crashes. In addition, the apnea group had more EEG-defined attention lapses of longer duration. Except for speed and steering rate variability, these differences increased over the 60-minute task. Measures of lane position variability and crash frequency had a significant positive correlation with attention lapse frequency and duration. CONCLUSIONS: The driving simulation task unmasked and quantified marked performance impairments in the sleep apnea group that increased over time. The poor performance appeared related to the EEG-defined attention lapses. Lane position variability appeared to be the most sensitive measure for assessing and quantifying impairment. This study suggests that poorer driving performance and crashes are not entirely due to overt sleep, but inattention due to sleepiness.

A closed-loop system for examining psychophysiological measures for adaptive task allocation.

A closed-loop system was evaluated for its efficacy in using psychophysiological indexes to moderate workload. Participants were asked to perform either 1 or 3 tasks from the Multiattribute Task Battery and complete the NASA Task Load Index after each trial. An electroencephalogram (EEG) was sampled continuously while they performed the tasks, and an EEG index (beta/alpha plus theta) was derived. The system made allocation decisions as a function of the level of operator engagement based on the value of the EEG index. The results of the study demonstrated that it was possible to moderate an operator's level of engagement through a closed-loop system driven by the operator's own EEG. In addition, the system had a significant impact on behavioral, subjective, and psychophysiological correlates of workload as task load increased. The theoretical and practical implications of these results for adaptive automation are discussed.

Evaluation of an adaptive automation system using three EEG indices with a visual tracking task.

A system was evaluated for use in adaptive automation using two experiments with electroencephalogram (EEG) indices based on the beta, alpha, and theta bandwidths. Subjects performed a compensatory tracking task while their EEG was recorded and converted to one of three engagement indices: beta/(alpha + theta), beta/alpha, or 1/alpha. In experiment one, the tracking task was switched between manual and automatic modes depending on whether the subject's engagement index was increasing or decreasing under a positive or negative feedback condition. Subjects were run for three consecutive 16-min trials. In experiment two, the task was switched depending on whether the absolute level of the engagement index for the subject was above or below baseline levels. It was hypothesized that negative feedback would produce more switches between manual and automatic modes, and that the beta/(alpha + theta) index would be most effective. The results confirmed these hypotheses. Tracking performance was better under negative feedback in both experiments; also, the use of absolute levels of engagement in experiment two resulted in better performance. There were no systematic changes in these effects over three 16-min trials. The implications for the use of such systems for adaptive automation are discussed.

Task-specific sex differences in vigilance performance: subjective workload and boredom.

Participants (24 men, 24 women) were asked to perform either a spatial or temporal vigilance task. Task-related Boredom and NASA-Task Load Index scores were collected. The results replicate Dittmar, Warm, Dember, and Ricks' 1993 finding of task-specific sex differences in vigilance performance and subjective workload. The present study also showed task-specific sex differences for boredom ratings. These results suggest that two explanations may account for the sex differences. More accurate perceptual discriminations may account for some of the differences in performance; however, sex differences in perceived boredom may more likely be responsible for the task-specific sex differences in vigilance performance and subjective workload.

Sex differences in visuo-spatial ability: task difficulty, speed-accuracy tradeoff, and other performance factors.

Males have consistently been found to perform better than females on a task that requires the subject to mentally rotate a figure. Recently, Goldstein. Haldane, and Mitchell (1990) suggested that performance factors are operative in explaining sex differences in spatial ability. However, Stumpf (1993) was unable to replicate all of Goldstein et al.'s (1990) findings and to generalize them to other measures of spatial ability. In this study, it was hypothesized (1) that females would take longer to respond and would get fewer correct items than males on a spatial rotation task, and (2) that only females would show a speed-accuracy tradeoff as the difficulty of the spatial task increased from the 90 degrees to 180 degrees rotated conditions. The results confirmed each of these hypotheses. Furthermore, as Stumpf (1993) found, when ratio scores from the number of items correct to number attempted were computed for both males and females, differences in spatial ability were reduced, though still evident.

Effects of extraversion and mental arithmetic on heart-rate reactivity.

The purpose of the present study was to examine the effect of extraversion and task difficulty on heart-rate reactivity. 15 extraverts and 15 introverts as identified by their scores on the Eysenck Personality Inventory completed mental arithmetic problems of three levels of difficulty. Two-way analysis of variance indicated that heart-rate reactivity increased as task difficulty increased. Also, introverts showed larger heart-rate reactivity to the task than extraverts. The present findings partially support Eysenck's physiological theory of extraversion in that introverted subjects were more aroused by the mental arithmetic task; however, the factors which produce such a difference are unclear.

Differential conditioning of environmental cues with amygdala kindling.

Recent evidence suggests that the pairing of environmental cues with kindling stimulation can affect the rate at which seizures develop. In the present study, the effect of differential conditioning was evaluated. Rats were kindled in either a black box or a highly illuminated white box. Half of the subjects in each of these groups (discrimination groups) was placed in the opposite box on separate days without receiving kindling stimulation. The remaining subjects (control groups) were placed only in the box in which they received stimulation. Subjects kindled in the white box developed stage 5 (clonic) seizures significantly faster than those kindled in the black box. Those subjects that received discrimination training with the white box positive kindled faster than all other groups. However, after reaching stage 5, both discrimination groups, regardless of which box was positive, had significantly shorter afterdischarge (AD) durations during threshold testing as compared with the control groups. Seizure thresholds did not differ for the different groups. No evidence for conditioned seizures was found. The results were discussed in terms of the potential facilitory and inhibitory effects of environmental cues on seizures.

The effect of amygdala-kindled seizures on the acquisition of taste and odor aversions.

Two experiments were conducted to investigate the effect of amygdala-kindled seizures on the acquisition of fluid aversions using taste, odor, and compound taste-odor cues. In Experiment 1 all subjects were poisoned with lithium chloride 30 minutes after ingesting a novel taste. Experimental subjects were either kindled 15 minutes following ingestion or 15 minutes following LiCl injection. The strength of the taste aversion in the kindled animals was significantly attenuated compared to nonkindled controls. There was a tendency for kindling within the CS-US interval to be more disruptive than kindling that occurred after LiCl injection. The second study explored the effect of kindling after the CS on the development of aversions to an odor cue or a compound taste-odor cue. This study found that kindling after drinking effectively blocked the acquisition of both odor and taste aversions and compounding did not affect the strength of the odor aversion.

The effects of naloxone and interstimulation interval on post-ictal depression in kindled seizures.

Two experiments were conducted to investigate the effects of naloxone hydrochloride on seizure thresholds seizure afterdischarges (thresholds and durations) and on post-ictal depression. Experiment 1 examined the effects of naloxone dosage and interstimulation interval (ISI) on kindled seizures. Eight male hooded rats were exposed to a factorial combination of two ISIs (30 and 60 s) and 3 naloxone doses (2, 10 mg/kg and a saline control) during a threshold testing procedure. Naloxone was found to significantly shorten motor seizure duration and post-ictal depression. Experiment 2 examined the effects of naloxone on a subsequent suprathreshold-stimulation-induced seizure following an initial suprathreshold stimulation. A factorial combination of 3 naloxone doses (2, 5 and 10 mg/kg) and a saline control and two ISIs (2 and 6 min) separating the two stimulations was employed. While no main effects for either naloxone or ISI were found in the subsequent seizure activity, there was a significant interaction between naloxone and ISI for the subsequent motor seizure duration. It was concluded from the results of the present experiments that the direction and consistency of naloxone's effects on kindled seizures were present but not very strong. However, the effects of ISI on seizure activity were found to be consistent with the previous literature.

Phencyclidine raises kindled seizure thresholds.

Phencyclidine (PCP) has been reported to have both anesthetic and seizure-inducing properties. In the present experiment the effect of PCP on previously established seizures, kindled in the amygdala, was examined, using rats as subjects. In a repeated measures design three doses of PCP (1, 2 and 5 mg/kg) were compared with a saline control condition. The high dose of PCP was found to significantly increase seizural afterdischarge thresholds, while not affecting seizure durations.

The effect of interstimulation interval on the assessment and stability of kindled seizure thresholds.

Two experiments were conducted to investigate the importance of the interstimulus interval (ISI) in the assessment of kindled seizure thresholds using an ascending method of limits. A third experiment examined the effect of varying the interval between successive threshold tests on threshold stability. No differences in afterdischarge (AD) or motor seizure (MS) threshold were observed when the ISI was either five minutes or 48 hours. However, a 30 second ISI yielded significantly higher AD and MS thresholds and shorter seizure duration compared to 1, 3, or 5 minute ISI's. AD and MS thresholds were found to be relatively stable over five successive tests when the inter-test interval was 48 hours. An inter-test interval of 24 hours, however, yielded progressively higher thresholds over the five tests.

Effects of alcohol on kindled seizure thresholds in rats.

Seizures were kindled in the amygdala and ventral hippocampus of rats until a stage 5 (clonic convulsion) was elicited. Stage 5 thresholds were than determined. Animals were then injected with either saline, or a 600 mg/kg, or 1600 mg/kg dose of 25% ethanol. The effect of each of these injections on seizure thresholds was assessed. The 1600 mg/kg dose caused a significant elevation in both AD and motor seizure thresholds, relative to the 600 mg/kg dose and saline, which did not differ. The elevation of seizure thresholds was significantly greater for animals with seizures kindled in the ventral hippocampus.