Bootstrap assessment of the reliability of maxima in surface maps of brain activity of individual subjects derived with electrophysiological and optical methods

Surface maps of brain activity can be obtained with electrophysiological and optical recordings. However, there are no established methods for determining the reliability of maps of brain activity across subject groups or across tasks within the same subject. In this paper, we use bootstrapping to establish the reliability of the locations of maxima in maps of surface brain activity of individual subjects obtained with ERP and optical (EROS) recordings and report sample analyses for two data sets. Bootstrapping is a nonparametric method for estimating statistical accuracy from the data in a single sample. The distribution of the statistic of interest is estimated by constructing “bootstrap samples” from a pool of all available cases (with replacement). Many “bootstrap replications” are obtained by calculating the statistic of interest for each sample. In the case of brain activity, many (e.g., 10,000) amplitude distributions can be derived from the data of an individual subject. Frequency counts are then computed for each recording location to establish how many times that location corresponds to a maximum. The value obtained in this fashion represents an estimate of the reliability of the observation.     

Discrimination of voice versus place contrasts in aphasia

A phoneme discrimination test based upon CCVC (consonant-consonant-vowel-consonant) syllables was administered to 36 aphasics, 91 brain-damaged subjects, and 42 normal controls, in normal listening conditions. Errors in the discrimination of voice and place contrasts were determined, and the scores (voice-minus-place errors) obtained by the four experimental groups were compared statistically. Aphasic patients, when compared with the other groups, show a greater difficulty in discriminating place than voice contrasts. Some implications of these findings are discussed.     

Scoring and interpreting the MMPI with a desk-top calculator

The development of a hospital-based routine system for off-line scoring and interpreting the MMPI with a small desk-top computer (HP 9830) is described. Main features of the system include the use of optical mark reader (OMR) cards instead of ordinary answer sheets and a software monitoring system allowing operator-independent processing. In terms of flexibility, speed, and economy, the system compares favorably with other computer-based test systems.     

Memories in drosophila heat-box learning

Learning and memory processes of operant conditioning in the heat-box are analyzed. In a search for conditioning parameters leading to high retention scores, intermittent training is shown to give better results than those of continuous training. Immediate retention tests contain two memory components, a spatial preference for one side of the chamber and a “stay-where-you-are-effect.” Intermittent training strengthens the latter. In the second part, memory dynamics is investigated. Flies are trained in one chamber and tested in a second one after a brief reminder training. With this direct transfer, memory scores reflect an associative learning process in the first chamber. To investigate memory retention after extended time periods, indirect transfer experiments are performed. The fly is transferred to a different environment between training and test phases. With this procedure, an aftereffect of the training can still be observed 2 h later. Surprisingly, exposure to the chamber without conditioning also leads to a memory effect in the indirect transfer experiment. This exposure effect reveals a dispositional change that facilitates operant learning during the reminder training. The various memory effects are independent of the mushroom bodies.     

Putting things into perspective: individual differences in working-memory span and the integration of information

An important function of working memory is the integration of incoming information into an appropriate model of the contextual situation. We hypothesized that individual variability in working-memory function (estimated using Engle's operation-span measure) may lead to differential reactivity to a changing context. We recorded event-related brain potentials (ERPs) and reaction-time measures to stimuli embedded in long stimulus series (two auditory discrimination tasks), and examined the participants' responses in relation to how the current stimuli fit with the context generated by the previous stimuli. In both tasks, participants with low working-memory span scores showed larger brain responses as a function of variations in the local stimulus sequence than participants with high span scores. These data suggest that the low working-memory span group is more affected by the local stimulus sequence than the high span group, possibly because they are more easily swayed by ongoing changes and are therefore less capable of maintaining their attention on the overall sequence.     

Assessing posttraumatic stress disorder with the MMPI-2 in a sample of workplace accident victims

In this study, the predictive capacity of the Minnesota Multiphasic Personality Inventory-2 Posttraumatic Stress Disorder-Keane (MMPI-2 PK) scale was examined in a sample of trauma victims who experienced a serious workplace-related accident and subsequent injury. In keeping with a number of previous investigations, the PK scale was largely ineffective in identifying posttraumatic stress disorder (PTSD) beyond overall symptom and functional severity. In contrast, sets of clinical and content scales proved to be significant predictors of PTSD. These findings suggest that the PK scale is not particularly useful in detecting PTSD in civilian trauma samples. Clinicians might be best advised to use the MMPI-2 clinical and content scales in their assessment of PTSD in civilian patients presenting with a history of trauma.     

A Psychophysiological Examination of Cognitive Processing of and Affective Responses to Social Expectancy Violations

Several models of person perception predict that expectancy violations have both affective and cognitive consequences for the perceiver. Although extant evidence generally supports these claims, the temporal resolution of traditional self-report measures has limited researchers' ability to convincingly link underlying physiological processes with observed outcomes. In this study, we examined these issues by measuring brain (event-related brain potentials) and peripheral (facial electromyogram) electrophysiological activity while participants read positive and negative expectancy-consistent, expectancy-violating, expectancy-irrelevant, and semantically incongruent behavioral sentences about fictitious characters. The electromyogram results indicated that negative (but not positive) expectancy-violating behaviors elicited enhanced negative affect as early as 100 to 300 ms poststimulus. The event-related potentials showed enhanced positivities with latency exceeding 300 ms in response to expectancy violations and negative behaviors. Semantically incongruent sentence endings influenced a separate negative component (N400), suggesting fundamental differences between semantic- and behavior-consistency processing. This difference also was evident in participants' recall. Implications for theoretical models of expectancy violation are discussed.     

Implementation intentions and disengagement from a failing course of action

We explored the consequences of forming implementation intentions that call for action (adjustment of chosen course of action) versus reflection (assessment of the appropriateness of chosen course of action) in situations that activate people's tendency to remain committed to failing courses of action. In Study 1, when negative experiences preceded failure, action and reflection implementation intention participants showed higher rates of disengagement than mere goal intention and no intention participants. However, when positive experiences preceded failure, only action implementation intention participants maintained this high disengagement rate. In Study 2, we observed that time pressure moderated the facilitating effects of action and reflection implementation intentions on disengagement when negative experiences preceded failure. Whereas the effect of action implementation intentions benefited from time pressure, the effect of reflection implementation intentions did not. The present studies construe disengagement as a self-regulation process and highlight the benefits of implementation intentions as a self-regulation tool. Copyright © 2006 John Wiley & Sons, Ltd.