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PubMedDate not supplied

Information processing by nonspiking interneurons: passive and active properties of dendritic membrane determine synaptic integration.

Nonspiking interneurons control activities of postsynaptic cells without generating action potentials in the central nervous system of many invertebrates. Physiological characteristics of their dendritic membrane have been analyzed in previous studies using single electrode current- and voltage-clamp techniques. We constructed a single compartment model of an identified nonspiking interneuron of crayfish. Experimental results allowed us to simulate how the passive and active properties of the dendritic membrane influence the integrative processing of synaptic inputs. The results showed that not only the peak amplitude but also the time course of synaptic potentials were dependent on the membrane potential level at which the synaptic activity was evoked. When the synaptic input came sequentially, each individual input was still discernible at depolarized levels at which the membrane time constant was short due to depolarization-dependent membrane conductances. In contrast, synaptic potentials merged with each other to develop a sustained potential at hyperpolarized levels where the membrane behaved passively. Thus, synaptic integration in a single nonspiking interneuron depends on the value of membrane potential at which it occurs. This probably reflects the temporal resolution required for specific types of information processing.

Action Potentials↗
PubMed2001

An evaluation of a caffeinated taurine drink on mood, memory and information processing in healthy volunteers without caffeine abstinence.

RATIONALE: Caffeine is present in a wide variety of beverages, often together with a number of other ingredients, such as sugars, taurine, glucuronolactone and vitamins. However, the majority of psychopharmacological studies have used pure caffeine tablets or drinks with doses in excess of those normally consumed in daily life. In addition, all the participants are usually deprived of caffeine for 10 h or more before the study. Consequently, it has been argued that any improvement in performance is only due to a reversal of caffeine withdrawal. OBJECTIVE: The present two studies tested participants who had minimal deprivation from caffeine (an hour or less) with an 80-mg caffeinated (80 mg/250 ml), taurine-containing beverage (commercially available) verum, which also contained sugars, glucuronolactone and vitamins. The placebos in the two studies were a sugar-free and a sugar-containing drink, in order to examine the effects of the sugar. METHODS: In total, 42 participants were tested with a rapid visual information test, a verbal reasoning test, a verbal and non-verbal memory test and a set of mood measures. Prior to testing, they were allowed ad libitum caffeinated beverages until 1 h before testing (study 1) and unrestricted caffeine use before testing (study 2). RESULTS: In both studies, the caffeinated, taurine-containing beverage produced improved attention and verbal reasoning, in comparison with a sugar-free and the sugar-containing drinks. The improvement with the verum drink was manifested in terms of both the mean number correct and the reaction times. Another important finding was the reduction in the variability of attentional performance between participants. No effects on memory were found. There were no differences in performance between the glucose and sugar-free drinks. CONCLUSIONS: Moderate doses of caffeine and taurine can improve information processing in individuals who could not have been in caffeine withdrawal.

Adolescent↗
PubMed2000

Abnormal information processing in dementia of Alzheimer type. A study using the event-related potential's field.

Electrical field changes of event-related potentials (ERPs) were investigated in 26 patients with dementia of Alzheimer's type (DAT) and 12 age-matched normal subjects. The patients were assessed with the Clinical Dementia Rating and Mini-Mental State. Each patient selected had only mild to moderate mental disability. Auditory oddball stimulation was presented at 1.5 s intervals and 1,000 Hz for the nontarget and 2,000 Hz for the target tones, both at 85 dB. The target tones were 20% of all the tones. The reference-independent data (latency, global field power: GFP, dissimilarity index: DISS and location of centroids) were obtained and analyzed for each ERP component. The momentary electric strength or 'hilliness' of the ERPs landscape was indicated by GFP. The patients showed prolonged latencies and decreased P300 GFP amplitudes and of N100 GFP. These findings suggest that the abnormal electrical field of ERP may reflect abnormal information processing following the attentional process for target stimuli in DAT patients.

Aged↗
PubMed1988

Event-related brain potentials: a window on information processing in schizophrenia.

The application of the P300 component of the event-related brain potential to the study of attentional impairment in schizophrenia is discussed, and two recent studies are described. In one, the relative effects on P300 of stimulus modality and probability were evaluated. The data showed that the P300 is smaller in schizophrenic patients relative to normal controls for low-probability auditory stimuli. Next is described a preliminary report that evaluated whether this P300 reduction reflects a core deficit (trait marker) or clinical symptomatology (state marker). To pursue this question, a group of schizophrenic patients was studied on and off neuroleptic medication. The data showed that improvement in clinical state was highly correlated with increased visual P300 but was uncorrelated with auditory P300. These findings suggest that P300 elicited in the visual modality has the characteristics of a state marker of schizophrenia. In contrast, auditory P300 remains a candidate for a vulnerability trait marker of schizophrenia. The core deficit in schizophrenia thus appears to involve the auditory information-processing system, whereas fluctuations in clinical state may be reflected in the visual processing system.

Antipsychotic Agents↗
PubMed1983

The emergence of spatial perspective taking: an information-processing alternative to egocentrism.

120 children between ages 4 and 8 were administered a set of 4 visual perspective-taking tasks similar to ones employed in previous investigations. It was hypothesized that children's competence with the tasks would be a function of the number and type of spatial relationships embedded in the stimulus displays. 2 kinds of spatial relationships were described: (1) internal relationships--those between objects within a display; and (2) external relationships--those between the display and a frame of reference. Of the 4 task types, type A tasks necessitated awareness of possible variations in external relations, types B and C tasks required both awareness and computation of changes in those external relationships, and type D tasks required simultaneous coordination of internal and external spatial relationships. It was predicted that the tasks would sequence in terms of difficulty level as A less than B, B = C, and C less than D. Analysis of variance results on the obtained data revealed a good fit with the hypothesized predictions. The findings were discussed in terms of an information-processing analysis of children's performance on perspective-taking tasks.

Child↗
PubMed2000

Visual information processing in patients with schizophrenia: evidence for the impairment of central mechanisms.

Patients with schizophrenia are especially impaired in the detection of spatial location if the briefly presented target stimulus is followed by a mask in a close temporal proximity (target location backward masking (BM) paradigm). It has been suggested that this phenomenon is related to the impairment of low spatial and high temporal frequency-sensitive transient (magnocellular) visual channels. To test this hypothesis, we measured target location BM and visual contrast sensitivity (CS) in clinically remitted patients with schizophrenia. In the BM task, subjects were asked to indicate the position of letters appearing at four possible spatial locations. In the CS test, a two-alternative forced choice method was used to measure the minimal contrast level required for the detection of horizontal gratings set at low spatial and high temporal frequencies (0.5 cycle/degree and 8 Hz, respectively). We found that the schizophrenia patients with normal CSs (spared transient channel functions) showed a marked deficit in the target location BM task. This suggests that the abnormality of subcortical transient channels does not explain some visual information processing dysfunctions in schizophrenia. Instead, deficient cortical interactions of rapidly changing environmental signals may be involved.

Adult↗
PubMed1999

Depressogenic cognitive styles: predictive validity, information processing and personality characteristics, and developmental origins.

Two of the major cognitive theories of depression, the theory of Beck [Beck, A. T. (1967). Depression: clinical, experimental and theoretical aspects. New York: Harper & Row. and Beck, A. T. (1987) Cognitive models of depression. Journal of Cognitive Psychotherapy: an International Quarterly, 1, 5-37] and the hopelessness theory [Abramson, Metalsky, & Alloy, (1989) Hopelessness depression: a theory-based subtype of depression. Psychological Review, 96, 358-372], include the hypothesis that particular negative cognitive styles increase individuals' likelihood of developing episodes of depression, in particular, a cognitively mediated subtype of depression, when they encounter negative life events. The Temple-Wisconsin Cognitive Vulnerability to Depression (CVD) project is a two-site, prospective longitudinal study designed to test this cognitive vulnerability hypothesis, as well as the other etiological hypotheses of Beck's and the hopelessness theories of depression. In this article, based on CVD project findings to date, we review evidence that the hypothesized depressogenic cognitive styles do indeed confer vulnerability for clinically significant depressive disorders and suicidality. In addition, we present evidence regarding moderators of these depressogenic cognitive styles, the information processing and personality correlates of these styles and the possible developmental antecedents of these styles. We end with a consideration of future research directions and the clinical implications of cognitive vulnerability to depression.

Cognition Disorders↗
PubMed2006

Temporal decoding by phase-locked loops: unique features of circuit-level implementations and their significance for vibrissal information processing.

Rhythmic active touch, such as whisking, evokes a periodic reference spike train along which the timing of a novel stimulus, induced, for example, when the whiskers hit an external object, can be interpreted. Previous work supports the hypothesis that the whisking-induced spike train entrains a neural implementation of a phase-locked loop (NPLL) in the vibrissal system. Here we extend this work and explore how the entrained NPLL decodes the delay of the novel, contact-induced stimulus and facilitates object localization. We consider two implementations of NPLLs, which are based on a single neuron or a neural circuit, respectively, and evaluate the resulting temporal decoding capabilities. Depending on the structure of the NPLL, it can lock in either a phase- or co-phase-sensitive mode, which is sensitive to the timing of the input with respect to the beginning of either the current or the next cycle, respectively. The co-phase-sensitive mode is shown to be unique to circuit-based NPLLs. Concentrating on temporal decoding in the vibrissal system of rats, we conclude that both the nature of the information processing task and the response characteristics suggest that the computation is sensitive to the co-phase. Consequently, we suggest that the underlying thalamocortical loop should implement a circuit-based NPLL.

Animals↗
PubMed2002

Stress and selective attention: the interplay of mood, cortisol levels, and emotional information processing.

The effects of a stressful challenge on the processing of emotional words were examined in college students. Stress induction was achieved using a competitive computer task, where the individual either repeatedly lost or won against a confederate. Mood, attention, and cortisol were recorded during the study. There were four findings: (1) Participants in the negative stressor condition were faster to shift attention away from negative words than positive or neutral words; (2) attentional shifts away from negative words were associated with stress-induced mood lowering; (3) participants in the negative stress condition with elevated scores on the Beck Depression Inventory were slow to disengage attention from all stimuli; and (4) elevated depression scores were associated with lower cortisol change from baseline during the experimental phase, and with higher cortisol levels during the recovery phase. These findings point to information-processing strategies as a means to regulate emotion, and to atypical features of cognitive and adrenocortical function that may serve as putative risk markers of depression.

Adolescent↗
PubMed1978

Complex learning and information processing by pigeons: a critical analysis.

THREE MODELS OF CONDITIONAL DISCRIMINATION LEARNING BY PIGEONS ARE DESCRIBED: stimulus configuration learning, the multiple-rule model, and concept learning. A review of the literature reveals that true concept learning is not characteristic of the behavior of pigeons in matching-to-sample, oddity-from-sample, or symbolic matching studies. Instead, pigeons learn a set of sample-specific S(D) rules. Transfer of the discrimination to novel stimuli, at least along the hue dimension, is predicted by a "coding hypothesis", which holds that pigeons make a unique, but usually unobserved response, R(1), to each sample, and that the comparison stimulus chosen depends on which R(1) was emitted in the presence of the sample. Convincing evidence is found that pigeons do code sample hues, but there is little evidence that allows one to infer that the "coding event" must have behavioral properties. Parameters of the conditional discrimination paradigm are identified, and it is shown that by appropriate parametric manipulation, a variety of analogous tasks may be generated for both human and animal subjects. The tasks make possible the comparative study of complex learning, attention, memory, and information processing, with the added advantage that behavior processes may be compared systematically across tasks.

Journal Article↗
PubMed2005

Information processing in severe disorders of consciousness: vegetative state and minimally conscious state.

OBJECTIVE: To study the presence of electrophysiological indicators of remaining cortical functions in patients with persistent vegetative state (PVS) and minimally conscious state (MCS). Previous electrophysiological and PET data indicated that some PVS patients have partially intact cortical processing functions. However, it remains unclear whether the reported patients were representative for PVS population or just some exceptional cases. METHODS: Event-related brain responses to stimuli of different complexity levels, recorded in 98 patients with extremely severe diffuse brain injuries, 50 of which in PVS. Four main indicators of cortical functions were: (i) N1-P2 complex as an index of simple, undifferentiated cortical processing; (ii) mismatch negativity as an index of pre-attentive, probably unconscious, cortical orientation; (iii) P3 wave as an index of deep cortical analysis of physical stimuli, and (iv) brain responses to semantic stimuli. RESULTS: Cortical responses were found in all PVS patients with a background EEG activity > 4 Hz. All responses investigated, including those to semantic stimuli that indicated comprehension of meaning, occurred significantly above chance, though less frequently than in patients with severe brain injuries who were conscious. CONCLUSIONS: Cortical responses were lacking in most patients with severe EEG slowing (< 4 Hz). Follow-up data revealed that the presence of a mismatch negativity, a short disease duration, and the traumatic etiology were related to a better outcome. SIGNIFICANCE: The data show that in a subpopulation of PVS patients with preserved thalamocortical feedback connections, remaining cortical information processing is a consistent finding and may even involve semantic levels of processing.

Auditory Cortex↗
PubMedDate not supplied

Diurnal variations of performance and information processing.

The aim of the study was to establish whether performance of a task in which controlled search is required fluctuates during the day or, on the other hand, performance of a task in which the automatic detection is required does not fluctuate during the day. The material and the procedure for setting the subject with an automatic detection set and for controlled search were determined as experimental paradigms and based on the results of the studies published by Shiffrin and Schneider. Eighteen volunteers from first and second year students of Psychology (9 boys and 9 girls) took part in the study. The study was done in January and February 1985 in the Laboratory of experimental psychology of Tours (France) on Tuesdays, Thursdays and Fridays. Each subject individually participated in 4 sessions on the same day, at 08(30); 11(45); 13(45) and 17(00). The results indicate that the performances (number of the targets correctly detected and the reaction time) only fluctuate in the course of the day when the controlled search is required. We suggest that the independence or the dependence of performance variation may be linked to the use of one or another of the two information processes described by Shiffrin and Schneider: controlled search and automatic detection.

Adult↗
PubMed1999

Genetic influence on auditory information processing in schizophrenia: P300 in monozygotic twins.

BACKGROUND: It is widely accepted that schizophrenia is to some extent genetically determined. Abnormalities of the P300 component are one of the most robust biological findings in schizophrenia. They outlast clinical impairment and are present also in relatives of schizophrenic patients. In the present study on schizophrenic twins, the heritability of auditory P300 abnormalities and the influence of task difficulty on heritability was examined. METHODS: Twenty-two monozygotic twin pairs were included into this study (eight pairs discordant, five pairs concordant for schizophrenia or schizoaffective psychosis according to ICD-10 criteria, and nine control pairs). Two different versions of the auditory oddball paradigm were used to control for deficient stimulus perception. RESULTS: Compared to healthy controls, P300 amplitudes were significantly smaller in affected twins as well as in the non-affected co-twins of the discordant pairs. CONCLUSIONS: Our results suggest that P300 amplitude reduction is a genetically transmitted vulnerability marker for schizophrenia. Because the findings were independent of the difficulty of the task and could be demonstrated even when pitch disparity was adjusted to the subjects' ability to discriminate tones, the findings can not be related to the genetic influence on higher information processing.

Adult↗
PubMed2005

Emotional information processing in violent patients with schizophrenia: association with psychopathy and symptomatology.

Schizophrenia and psychopathy have been independently shown to be associated with deficits in the recognition of facial expressions. These disorders are highly co-morbid in forensic settings, and both are associated with aggressive behaviour. This study examines the relative contribution of psychopathic traits and psychotic symptoms to reported deficits in facial affect recognition in forensic patients with schizophrenia. Fifty-four male patients with schizophrenia were recruited from medium and high security hospitals. Participants were categorised into groups with high (HP), medium (MP) and low (LP) scores on the Psychopathy Checklist: Screening Version and based on symptomatology assessed using the Positive and Negative Syndrome Scale. Participants completed an animated facial affect recognition task assessing accuracy across the six basic emotions over high and low intensities. The HP group was found to have impaired recognition of sadness at low intensity compared with the LP group. In the overall sample, facial affect recognition for negatively valenced emotions was not related to positive or negative symptom scores. However, recognition accuracy for disgust was found to be negatively related to the severity of cognitive symptoms. Patients with high psychopathy scores and schizophrenia showed similar deficits in emotional information processing to those reported in the literature in non-psychotic psychopathic samples.

Adult↗
PubMed2000

A computational model of information processing in the frontal cortex and basal ganglia.

Performance on the Wisconsin Card Sort Test (WCST) of patients with schizophrenia, Parkinson's disease (PD), and Huntington's disease (HD) was simulated by a neural network model constructed on principles derived from neuroanatomic loops from the frontal cortex through the basal ganglia and thalamus. The model provided a computational rationale for the empirical pattern of perseverative errors associated with frontal cortex dysfunction and random errors associated with striatal dysfunction. The model displayed perseverative errors in performance when the gain parameter of the activation function in units representing frontal cortex neurons was reduced as an analog of reduced dopamine release. Random errors occurred when the gain parameter of the activation function in units representing striatal neurons was reduced, or when the activation level was itself reduced as an analog of a striatal lesion. The model demonstrated that the perseveration of schizophrenic, Huntington's, and demented Parkinsonian patients may be principally due to ineffective inhibition of previously learned contextual rules in the frontal cortex, while the random errors of Parkinson's and Huntington's patients are more likely to be due to unsystematic errors of matching in the striatum. The model also made specific, empirically falsifiable predictions that can be used to explore the utility of these putative mechanisms of information processing in the frontal cortex and basal ganglia.

Basal Ganglia↗
PubMed1993

Local interneurons and information processing in the olfactory glomeruli of the moth Manduca sexta.

Intracellular recordings were made from the major neurites of local interneurons in the moth antennal lobe. Antennal nerve stimulation evoked 3 patterns of postsynaptic activity: (i) a short-latency compound excitatory postsynaptic potential that, based on electrical stimulation of the antennal nerve and stimulation of the antenna with odors, represents a monosynaptic input from olfactory afferent axons (71 out of 86 neurons), (ii) a delayed activation of firing in response to both electrical- and odor-driven input (11 neurons), and (iii) a delayed membrane hyperpolarization in response to antennal nerve input (4 neurons). Simultaneous intracellular recordings from a local interneuron with short-latency responses and a projection (output) neuron revealed unidirectional synaptic interactions between these two cell types. In 20% of the 30 pairs studied, spontaneous and current-induced spiking activity in a local interneuron correlated with hyperpolarization and suppression of firing in a projection neuron. No evidence for recurrent or feedback inhibition of projection neurons was found. Furthermore, suppression of firing in an inhibitory local interneuron led to an increase in firing in the normally quiescent projection neuron, suggesting that a disinhibitory pathway may mediate excitation in projection neurons. This is the first direct evidence of an inhibitory role for local interneurons in olfactory information processing in insects. Through different types of multisynaptic interactions with projection neurons, local interneurons help to generate and shape the output from olfactory glomeruli in the antennal lobe.

Animals↗
PubMed2001

Auditory information processing during adequate propofol anesthesia monitored by electroencephalogram bispectral index.

UNLABELLED: Memory for intraoperative events may arise from inadequate anesthesia when the hypnotic state is not continuously monitored. Electroencephalogram bispectral index (BIS) enables monitoring of the hypnotic state and titration of anesthesia to an adequate level (BIS 40 to 60). At this level, preserved memory function has been observed in trauma patients. We investigated memory formation in elective surgical outpatients during target-controlled propofol anesthesia supplemented with alfentanil. While BIS remained between 40 and 60, patients listened to a tape with either familiar instances (exemplars) from two categories (Experimental [E] group, n = 41) or bird sounds (Control [C] group, n = 41). After recovery, memory was tested directly and indirectly. BIS during audio presentation was on average (+/- SD) 44 +/- 5 and 46 +/- 5 for Groups E and C, respectively. No patient consciously recalled the intraoperative period, nor were presented words recognized reliably (Group E, 0.9 +/- 0.8 hits; Group C, 0.8 +/- 0.8 hits) (P = 0.7). When asked to generate category exemplars, Group E named 2.10 +/- 1.0 hits versus 1.98 +/- 1.0 in Group C (P = 0.9). We found no explicit or implicit memory effect of familiar words presented during adequate propofol anesthesia at BIS levels between 40 and 60 in elective surgical patients. IMPLICATIONS: This study suggests that stable levels of adequate hypnosis may prevent information processing and memory formation during general anesthesia and supports the feasibility of electroencephalogram bispectral index as a monitor of adequate anesthesia.

Acoustic Stimulation↗
PubMed2005

Cortical cholinergic transmission and cortical information processing in schizophrenia.

Models of the neuronal mediation of psychotic symptoms traditionally have focused on aberrations in the regulation of mesolimbic dopaminergic neurons, via their telencephalic afferent connections, and on the impact of abnormal mesolimbic activity for functions of the ventral striatum and its pallidal-thalamic-cortical efferent circuitry. Repeated psychostimulant exposure models major aspects of the sensitized activity of ventral striatal dopaminergic transmission that is observed in patients exhibiting psychotic symptoms. Based on neuroanatomical, neurochemical, and behavioral data, the hypothesis that an abnormally reactive cortical cholinergic input system represents a necessary correlate of a sensitized mesolimbic dopaminergic system is discussed. Moreover, the abnormal cognitive mechanisms that contribute to the development of psychotic symptoms are attributed specifically to the aberrations in cortical cholinergic transmission and to its consequences on the top-down regulation of sensory and sensory-associational input functions. Experimental evidence from studies demonstrating repeated amphetamine-induced sensitization of cortical cholinergic transmission and the ability of antipsychotic drugs to normalize the activity of cortical cholinergic inputs, and from experiments indicating the attentional consequences of manipulations that increase the excitability of cortical cholinergic inputs, supports this hypothesis. Relevant human neuropathological and psychopharmacological data are discussed, and the implications of an abnormally regulated cortical cholinergic input system for pharmacological treatment strategies are addressed. Given the role of cortical cholinergic inputs in gating cortical information processing, even subtle changes in the regulation of this cortexwide input system that represent a necessary transsynaptic consequence of sensitized mesolimbic dopaminergic transmission profoundly contribute to the neuronal mediation of psychotic symptoms.

Acetylcholine↗