Bacteriorhodopsin: a biological material for information processing.
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The present study was aimed at deciphering whether the delay in choice reaction time (RT) and the silent period (SP) caused by transcranial magnetic stimulation (TMS) of the motor cortex in the ongoing electromyogram are due to the same physiological mechanism. To this end, the effect of TMS was studied in 6 healthy volunteers performing a between-hand choice RT task. Specific predictions were derived from a logic inspired from the "postponed stages" hypothesis (Pashler & Johnson, 1989). This logic predicts a correlation between SP duration and RT when the stimulated cortex is involved in the response, and a stronger correlation when the stimulation is delivered later during the RT interval. The effect of TMS on RT was twofold: At early stimulation times, the stimulation shortened the RT and this effect was independent of the involvement of the stimulated motor cortex in the subsequent response. At later stimulation times, TMS had a disruptive effect, provided that the stimulated cortex was involved in the response. When the stimulated cortex was involved in the response, there was a correlation between SP and RT; this correlation was stronger when the stimulation occurred later. In contrast, there was no correlation between these two variables when the stimulated cortex was not involved.
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Recovery of cognitive function after mild head injury (MHI) is thought to be relatively swift and complete. The present study replicates and extends previous work in which university students with self-reported concussion demonstrated reduced P300 amplitude on a set of easy and difficult attention tasks, in addition to performing more poorly than controls on demanding cognitive tasks many years after injury. In the present study, 13 students with self-reported concussion (MHI group: M time since injury = 8 years) and 10 controls were matched for age, sex, education, and a variety of cognitive, physical and emotional complaints. Controls outperformed the MHI group on the Digit Symbol substitution task and on a difficult dual task involving tone discrimination and visual working memory. Additionally, controls exhibited larger P300 amplitudes on both an easy and a difficult auditory discrimination task. A combination of electrophysiological, neuropsychological and self-report indices predicted group membership (MHI vs. control) with 88% accuracy. The present results, coupled with previous work, offer preliminary evidence that the combination of event-related potentials and demanding behavioral measures might reveal long-lasting, subtle cognitive problems associated with MHI. These findings may challenge existing notions of complete recovery after MHI.
Mock jurors recruited from jury rolls were either not given written statements of expert witnesses' direct testimony or were provided with such statements before or after the presentation of that testimony. Presentation of the statements before the testimony and cross-examination provided jurors with a schema that allowed them to distinguish more effectively among the claims of four differentially worthy plaintiffs because they processed more probative evidence than other jurors. Jurors in receipt of written statements before the testimony found the evidence to be more comprehensible than other jurors. Jurors provided with written statements following testimony and cross-examination were able to differentiate between the most and least severely injured plaintiffs, whereas jurors not in receipt of any written statements were unable to differentiate among any of the differentially worthy claimants. The limitations of this case management technique and of the study are discussed.
The intestinal reactivity to emotional experiences is poorly understood. We therefore compared healthy controls with nonpsychiatric irritable bowel syndrome (IBS) patients and IBS patients with comorbid phobic anxiety disorders with respect to rectal wall reactivity during exposure to everyday words with emotional content. We found that 70.3% of the subjects responded either with increased or decreased rectal tone during exposure to anger words, 75.0% when exposed to sadness words, and 76.6% when exposed to anxiety words. We also investigated event-related potentials in the brain to the same stimuli. We observed significant group differences in the frontal brain to sadness (P < 0.001) and anxiety (P = 0.013) distracter words, and threshold significant group difference to anger (P = 0.053) distracter words. Rectal wall reactivity during the word series significantly predicted frontal amplitude to the same word series, indicating a close interaction among mind, brain, and gut.
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This study investigated developmental increases in processing speed in young children, relative to adults, with only nonverbal stimuli. R. Kail's (1991) model of the rate of change in processing speed from childhood to adulthood was evaluated. Processing speed was measured in 34 children at 4 years, 37 at 5 years, and 38 at 6 years and in 43 adults, with a battery of 8 computer-administered tests. Results showed clear age-related increases in processing speed that cannot be attributed to increased accuracy and error rate monitoring. Kail's model adequately accounted for the observed rate of developmental change in processing speed; however, the parameter estimates of R. Kail and Y. Park (1992) provided more accurate predictions than did the meta-analytically derived estimates of Kail (1991). Findings support the global developmental trend hypothesis and suggest that this trend extends beyond the range of verbal skills evaluated in previous research.
The relation between resource limitations and the type of processing (automatic vs. controlled) on a multiple-frame search task (MFST) was examined in 15 schizophrenic and 15 normal control subjects. After 320 trials of consistently mapped practice, the patients' detection accuracy was normalized, and the effect of processing load (letter array size) on their detection accuracy was eliminated, which suggests automatization. Changes in load effects with practice could not be used as an index of automatization in control subjects, because of their unexpected lack of load effects at the beginning of practice. In a dual-task (MFST during auditory shadowing) condition after MFST practice, patients' MFST accuracy deteriorated nonsignificantly, and patients' shadowing declined significantly. The findings suggest schizophrenics have reduced available processing resources, but research is needed to determine whether this is due to abnormal automatization.
This study examined the influence of smoking cues and nicotine deprivation on responses to alcohol among hazardous drinkers. Fifty-six daily smoking, hazardous drinkers were exposed to either smoking cues or control cues after either 6 hr of nicotine deprivation or no deprivation. Urges to drink alcohol, alcohol-related cognitive processing, and alcohol consumption were assessed after cue exposure. Results indicated that nicotine deprivation increased urges to drink, the accessibility of alcohol outcome expectancies, and the volume of alcohol consumed. There was little influence of the smoking cue manipulation on these processes. Implications for understanding the mechanisms underlying alcohol-tobacco interactions are discussed.
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