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Corpus callosum function in schizophrenia: a neuropsychological assessment of interhemispheric information processing.

Impaired corpus callosum function has been reported in schizophrenia. We measured intra- and interhemispheric visual information processing in 16 schizophrenic patients and 16 matched controls. Although the schizophrenics performed worse between than within cerebral hemispheres, this pattern was similar to that of the normal controls. Schizophrenics do not show particular dysfunction of the corpus callosum.

Adult↗

NMDA receptors in sensory information processing.

During the past year electrophysiological studies, particularly in the visual and somatosensory systems, have begun to uncover the specific roles played by NMDA receptors in the processing of sensory information. Many of the features of NMDA-receptor-mediated sensory responses reflect known properties of the receptor.

Afferent Pathways↗

Multisensory attention and tactile information-processing.

Although a great deal is now known about the peripheral sensory mechanisms involved in tactile information processing [Ann Rev Psychol 1990;50:305], it is only more recently that we have started to gain a clearer understanding of the effects of selective attention on tactile perception [Front Biosci 2000;5:D894]. To date, the majority of this selective attention research has considered each modality in isolation. However, in order to deal with the multimodal selection problems of everyday life, we need to be able to coordinate our selective attention cross-modally [Philos Trans R Soc, Sec B 1998:353; Curr Biol 2000;10:R731]. In this review, I will highlight the results of behavioral studies demonstrating the existence of extensive cross-modal links in selective attention between touch, vision, audition, and even olfaction. In particular, the review is structured around two key research questions: First, "Can attention can be selectively directed to a particular sensory modality?", and second "Are there cross-modal links in spatial attention?". The results of recent neuroimaging studies that have started to elucidate some of the neural mechanisms underlying these cross-modal attentional effects are also discussed, and potential questions for future research outlined.

Attention↗

Olfactory information processing during the course of the menstrual cycle.

In the present study we examined whether olfactory information processing depends on the phase of the menstrual cycle. Five female subjects were investigated during three phases (follicular, ovulatory, luteal) of their menstrual cycle. In each session chemosensory (olfactory) event-related potentials (CSERP) were recorded and olfactory thresholds and the hedonic tone of the test stimulus (citral) were determined. Threshold values were correlated with the salivary cortisol level. The results show that olfactory perception changes during the menstrual cycle. After the first stimulus presentations in a recording session, odors were perceived as more complex or novel during the ovulatory period (enhanced amplitude of P3-1). With continued stimulation, odor processing became faster (reduced latency of NI, P2 and P3-2) around ovulation and slower during the follicular phase. Moreover, odors were described more differentially during the ovulatory period. Olfactory sensitivity was correlated positively with the peripheral cortisol level.

Adult↗

Social-information-processing factors in reactive and proactive aggression in children's peer groups.

We examined social-information-processing mechanisms (e.g., hostile attributional biases and intention-cue detection deficits) in chronic reactive and proactive aggressive behavior in children's peer groups. In Study 1, a teacher-rating instrument was developed to assess these behaviors in elementary school children (N = 259). Reactive and proactive scales were found to be internally consistent, and factor analyses partially supported convergent and discriminant validities. In Study 2, behavioral correlates of these forms of aggression were examined through assessments by peers (N = 339). Both types of aggression related to social rejection, but only proactively aggressive boys were also viewed as leaders and as having a sense of humor. In Study 3, we hypothesized that reactive aggression (but not proactive aggression) would occur as a function of hostile attributional biases and intention-cue detection deficits. Four groups of socially rejected boys (reactive aggressive, proactive aggressive, reactive-proactive aggressive, and nonaggressive) and a group of average boys were presented with a series of hypothetical videorecorded vignettes depicting provocations by peers and were asked to interpret the intentions of the provocateur (N = 117). Only the two reactive-aggressive groups displayed biases and deficits in interpretations. In Study 4, attributional biases and deficits were found to be positively correlated with the rate of reactive aggression (but not proactive aggression) displayed in free play with peers (N = 127). These studies supported the hypothesis that attributional biases and deficits are related to reactive aggression but not to proactive aggression.

Aggression↗

Dividing attention within and between hemispheres: testing a multiple resources approach to limited-capacity information processing.

Two experiments tested the limiting case of a multiple resources approach to resource allocation in information processing. In this framework, the left and right hemispheres are assumed to have separate, limited-capacity pools of undifferentiated resources that are not mutually accessible, so that tasks can overlap in their demand for these resources either completely, partially, or not at all. We tested all three degrees of overlap in demand for left hemisphere supplies, using dual-task methodology in which subjects were induced to pay different amounts of attention to each task. Experiment 1 compared complete and partial overlap by combining a verbal memory load with a task in which subjects named nonsense syllables briefly presented to either the left or right visual field (LVF and RVF, respectively). Experiment 2 compared complete versus no overlap by using the same verbal memory load combined with a laterally presented same-different judgment task that did not require a spoken response. Decrements from single-task performance were always more severe when the visual field task stimulus was presented to the RVF. Further, subjects in Experiment 1 were able to trade performance between tasks on both LVF and RVF trials because there was always at least some overlap in left hemisphere demand. In Experiment 2, performance trade-offs were observed on RVF (complete overlap) trials, but not on LVF trials, where no overlap in demand existed. These results contradict a single-capacity model, but they support the idea that the hemispheres' resource supplies are independent and have implications for both cerebral specialization and divided attention issues.

Attention↗

[The study of central nervous information processing with transcranial magnetic stimulation].

In cognitive neuroscience different methods are used to study central nervous information processing. Transcranial magnetic stimulation (TMS) is a non-invasive, well tolerated technique to interfere with cortical neuronal activity with high temporal and fair spatial resolution. In the past 10 years the use of TMS expanded from its application as a diagnostic routine procedure in neurology to the study of various cognitive functions. In this paper the physical and technical aspects of TMS and studies on the effects of single pulse versus repetitive TMS in the motor cortex are reviewed. Then, research on visual perception and attention is presented and studies on higher cognitive functions, such as speech, memory, and emotions are discussed.

Brain↗

Tracking early and late stages of information processing: contributions of startle eyeblink reflex modification.

Startle eyeblink modification was examined as a measure of information processing. College students were presented with tones of 5 and 7 s duration of either high or low pitch, followed by startle-eliciting stimuli at lead intervals of 120, 2,000, 4,500, or 6,000 ms. Attention to tones was manipulated by instructing the task group to count the longer tones of either pitch. The no-task group had no instructed task. Startle eyeblink was inhibited at the short lead interval and facilitated at the long lead intervals in both groups. The task group showed greater inhibition and facilitation during attended than during ignored tones, indicating that early and late controlled processing was occurring. In the task group, the degree of facilitation appeared to reflect the degree of cognitive demands of the task. Startle eyeblink modification may provide a sensitive measure of the nature and timing of stages of processing in active and passive attentional conditions.

Adult↗

Cortical potential distributions and information processing.

The use of sets of spatiotemporal cortical potential distributions (CPDs) as the basis for cognitive information processing results in a very large space of cognitive elements with natural metrics. Results obtained from current source density (CSD) analysis suggest that in the CPD picture, action potentials may make only a relatively minor contribution to the brain's code. In order to establish if two CPDs are close, we consider standard metrics in spaces of continuous functions, and these may be employed to ascertain if two stimuli will be identified as the same. The correspondence between the electrical activity within brain regions, including not only action potentials but all postsynaptic potentials (PSPs), and CPDs is considered. We examine the possibility of using the CSD approach to find potential distributions using the descriptive approach in which precise sets of times are ascribed to the occurrence of action potentials and PSPs. Using metrics in the multidimensional space of paths of collections of point processes, we show that closeness of CPDs is implied by closeness of sets of spike times and PSP times if a certain metric is used but not others. We also set forth a dynamical model consisting of a system of reaction-dif fusion equations for ionic concentrations coupled with nerve membrane potential equations and active transport systems. Making the approximation of a descriptive approach, the correspondence between sets of spike times and PSP times and CPDs is obtained as with the CSD method. However, since it is not possible to ascribe precise times to the occurrence of PSPs and action potentials, the descriptive approach cannot be used to describe the configuration of electrical activity in cortical regions accurately. We also discuss how the CPD framework relates to the binding problem and submillisecond timing.

Algorithms↗

The influence of nursing diagnosis on information processing by undergraduate students.

PURPOSE: To examine the influence of a nursing diagnosis course on the information processing by undergraduate students. METHODS: A quasi-experimental study conducted with two groups (experimental, n = 15; control, n = 22) of undergraduate nursing students, subjecting only one to a nursing diagnosis course. The students' ability to identify, cluster, and name clusters of relevant data were compared between and within groups. FINDINGS: After the course, the experimental group performed better than the control group in the three activities studied. CONCLUSIONS: The results of this study suggest that the nursing diagnosis content in teaching favors clinical reasoning to determine the patient's nursing care.

Adult↗

Information processing following mild head injury.

Research has shown that individuals who have sustained mild head injury demonstrate a slowed speed of processing that is exacerbated by fatigue/stress. We administered the Paced Auditory Serial Addition Test (PASAT) at the beginning and at the end of a 4-h experimental protocol to determine whether fatigue or a stressor would result in poorer scores for individuals who had previously sustained mild head injury. A significant improvement was found between the first and second administration for both head-injured and control subjects, but difference scores revealed a significant between-groups difference for the first of the four trials, with the head-injured participants performing worse than controls. Apparently, head-injured participants were slower to develop, as well as slower to regain, a means of efficiently processing rapidly presented information.

Adolescent↗

Nonlinear Optics for High-Speed Digital Information Processing.

Recent advances in developing nonlinear optical techniques for processing serial digital information at high speed are reviewed. The field has been transformed by the advent of semiconductor nonlinear devices capable of operation at 100 gigabits per second and higher, well beyond the current speed limits of commercial electronics. These devices are expected to become important in future high-capacity communications networks by allowing digital regeneration and other processing functions to be performed on data signals "on the fly" in the optical domain.

Journal Article↗

Apparently enhanced visual information processing in female fragile X carriers: preliminary findings.

Eighteen normally intelligent adult female fragile X carriers were tested with the "de Sonneville Visual Attention Tasks," a computer-based set of reaction-time experiments, in order to assess different aspects of their attention capacity. The subject group was compared with a group of 48 adults, who were not known to be fragile X carriers. We publish preliminary results of this study. These show that the fragile X carriers have significantly faster reaction times at a substantial number of the tests. This suggests that normally intelligent female fragile X carriers might process simple visual information, such as the targets offered in these reaction time experiments, at a faster rate than control women.

Adult↗

Cerebral information processing estimated by unpredictability of the EEG.

Processing of complex information by the brain desynchronizes neuronal cells and therefore increases the unpredictability of the EEG, rather than its amplitude or power. A model of this mechanism describes the EEG as being composed of both an unpredictable fraction and a fraction that can be predicted from the past EEG. The model realistically simulates EEG of several behavioural states and suggests a simple algorithm for the computation of EEG predictability (values between 0% and 100%). Applications in sleep analysis and event-related desynchronization demonstrated that the algorithm is more accurate and artifact-resistant than the usual (spectral) power methods.

Algorithms↗

Temporal information processing in cones: effects of light adaptation on temporal summation and modulation.

We have studied the temporal information processing of turtle cones in steady states of light adaptation using intracellular recording techniques. We measured the linear range incremental sensitivity of cones as a function of the stimulus duration. Linear range incremental sensitivity is a function of the background intensity. It is also proportional to the duration of short duration stimuli but is independent of duration for long duration stimuli. The plot of log sensitivity versus log stimulus duration displays two straight line asymptotes; a slope of one for short durations and a slope of zero for long durations. These asymptotes intersect at a time, the critical duration, which decreases with increasing background intensity. Linear systems theory was used to predict these results in addition to the interdependence of critical duration, response kinetics, and sensitivity for any state of adaptation. We have also calculated cone sensitivity as a function of sinusoidal frequency for a variety of background intensities. Correlations between these results and psychophysical studies suggest that the limits on temporal summation established by the cones appear not to be substantially altered by the rest of the retina.

Adaptation, Ocular↗

Revictimization and information processing in women survivors of childhood sexual abuse.

This study examined the effect of sexual revictimization on information processing of trauma-related stimuli in a sample of child sexual abuse (CSA) survivors diagnosed with posttraumatic stress disorder (PTSD). Fifty-one treatment-seeking women participated in this study. Participants completed the Sexual Experiences Survey regarding sexual revictimization in the last 6 months and performed a modified emotional Stroop task in which they named the colors of neutral words (e.g., apple), general threat words (e.g., malignant and death), and sexual/victimization words (e.g., penis and abuser). As predicted, the revictimized participants (n = 16) took significantly longer to color-name sexual/victimization words than did the nonrevictimized participants. These results suggest that revictimization serves to prime preexisting "trauma" memory networks, thereby amplifying the impact of childhood sexual trauma on selective attention toward trauma-related stimuli.

Adult↗

Visual information processing in high-functioning individuals with autism spectrum disorders and their parents.

The authors assessed visual information processing in high-functioning individuals with pervasive developmental disorders (PDD) and their parents. The authors used tasks for contrast sensitivity, motion, and form perception to test visual processing occurring relatively early and late in the magnocellular-dorsal and parvocellular-ventral pathways. No deficits were found in contrast sensitivity for low or high spatial frequencies or for motion or form perception between individuals with PDD in comparison with a matched control group. Individuals with PDD performed equally with or better than controls on motion detection tasks. In addition, the authors did not find differences on any of the tasks between parents of the PDD group and matched control parents. These results indicate that high-functioning individuals with PDD and their parents are able to process visual stimuli that rely on early or late processing in the magnocellular-dorsal and parvocellular-ventral pathways as well as controls.

Adolescent↗