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PubMed2000

The role of the spindle in human information processing of high-intensity stimuli during sleep.

Sleep spindles are 12-14 Hz oscillations in EEG, which are thought to inhibit or 'gate' information processing. Event-related potentials may be employed to probe the extent of information processing during sleep. Previous research indicates that event-related potentials elicited by moderate intensity stimuli show increased positivity (or further removal of negativity) when stimuli are presented concurrent with spindles. However, the effectiveness of spindles to inhibit the processing of much louder stimuli remains unknown. The purpose of the present study was to investigate the extent of this gating, by using a range of stimuli including those that are loud and intrusive. Eight good sleepers were recorded during a single night. Auditory stimuli were delivered randomly at 0, 60, 80 or 100 dB SPL. Trials were sorted off-line by sleep stage, stimulus intensity and spindle characteristic (i.e. spindle absent, spindle present). During the sleep-onset period, the often-reported changes in event-related potentials were observed - N1 decreased and P2 increased in amplitude. In Stage 2 sleep, P2 was affected by the presence of spindles, particularly when stimulus intensity was loud. Its amplitude was greatest when spindles occurred following the onset of the stimulus. Scalp-recorded spindles might, therefore, be a consequence of the prior thalamic inhibition of information processing, especially when confronted by loud, intrusive external stimuli.

Acoustic Stimulation↗
PubMed2002

Dopamine and human information processing: a reaction-time analysis of the effect of levodopa in healthy subjects.

RATIONALE: Dopamine is involved in a variety of motor and non-motor information-processing operations. One way to determine its contribution to human information processing is to study reaction time (RT) performance after oral absorption of its precursor, levodopa, which increases its concentration in the nervous system. OBJECTIVE: The purpose of the present study was to investigate the effect of a single dose of levodopa on information processing in healthy human subjects using the additive-factor method. After oral absorption of a single dose of levodopa (200 mg) or a placebo (randomized, double-blind, cross-over design), eight adults (aged 21-28 years, mean 25 years) performed a two-choice visual RT task. Signal intensity, stimulus-response mapping and foreperiod duration were manipulated. RESULTS: The effects of these three variables were found additive on RT, indicating that that three independent stages - namely, stimulus preprocessing, response selection and motor adjustment - were manipulated. Levodopa improved RT performance in a specific way: it interacted with signal intensity but its effect was additive with those of stimulus-response mapping and foreperiod duration. CONCLUSION: These results show that levodopa specifically affects the stimulus preprocessing stage, which suggests that the dopaminergic system plays a role in sensory processing, possibly by acting on the level of arousal.

Adult↗
PubMed2001

Cognitive function and information processing in type 2 diabetes.

AIMS: To determine whether uncomplicated Type 2 diabetes is associated with impairment of cognitive function and information processing ability. METHODS: Thirty-eight participants with uncomplicated Type 2 diabetes and 38 non-diabetic controls were studied. The two groups were comparable for age and premorbid intellectual ability, and did not have other medical disorders likely to affect cognitive function. An extensive battery of tests was administered which assessed different levels and domains of cognitive functions including verbal and visual memory, executive function, general mental ability and efficiency of information processing. RESULTS: No significant differences were found between the diabetic and control groups on any measure of cognitive function or information processing. The performance on these tests was not associated with recent glycaemic control (assessed by HbA1c). Duration of diabetes, however, correlated significantly with poorer performance on several measures of verbal memory. CONCLUSIONS: The results of the present study suggest that some aspect of Type 2 diabetes (as indexed by the estimated duration of the disorder) does relate significantly to cognitive function within the group with diabetes. However, other diabetes-related factors, such as macrovascular disease, hypertension and depression, may contribute more to previously observed cognitive decrements in Type 2 diabetes.

Age of Onset↗
PubMed1993

Information processing efficiency in chronic fatigue syndrome and multiple sclerosis.

OBJECTIVE: To compare the cognitive performance of subjects with chronic fatigue syndrome (CFS), multiple sclerosis (MS), and healthy controls. All subjects were matched for age, education, and verbal intelligence, as previous neuropsychological studies of CFS had not used appropriate control groups. DESIGN: Case-control design. All subjects were given a neuropsychological battery and the test scores were compared among the groups. SETTING: Subjects with CFS and subjects with MS were recruited from private and institutional practice and from the community. Healthy subjects were recruited from the community. PATIENTS/OTHER PARTICIPANTS: Twelve subjects (all female) with CFS participated in the study. Chronic fatigue syndrome was diagnosed in these patients in accordance with the requirements outlined by the Centers for Disease Control as modified subsequently to not exclude patients with concurrent depression and/or anxiety. All subjects with CFS were referred for a neuropsychological examination to assess persistent cognitive complaints. Eleven subjects (10 female, one male) with the diagnosis of clinically stable MS were chosen from clinics and the community because of complaints of mild to moderate cognitive impairment. The subjects with MS and 11 healthy volunteers (10 female, one male) were matched to the group with CFS by age, education, and estimated verbal intelligence (based on the Vocabulary subtest of the Wechsler Adult Intelligence Scale-Revised). The subjects with MS had a mean Kurtzke Expanded Disability Status Scale score of 4.95 (SD, 1.95; range, 2.0 to 7.5). As a result of the matching procedure, there were no differences among the three groups in age (F[2,31] = 0.32), education (F[2,31] = 0.80), and verbal intelligence (F[2,31] = 0.31). INTERVENTIONS: None. MAIN OUTCOME MEASURES: These measures included the Beck Depression Inventory (BDI), the Paced Auditory Serial Addition Test (PASAT), Digit Span Test, and the Similarities Test of Verbal Abstract Reasoning. RESULTS: The mean number of correctly identified responses collapsed across the four PASAT trials was significantly different across groups (F[2,31] = 4.03; P < .05). While the CFS and MS groups did not differ from each other, subjects with CFS (SEM, 124.2 +/- 6.4) and subjects with MS (SEM, 112.9 +/- 10.9) scored significantly below controls (SEM, 146.4 +/- 6.4) (Fisher's Protected Least Significant Difference test; P < .05). There were significant differences among the three groups on mean Digit Span Test performance (F[2,31] = 5.5; P < .01). While the CFS and MS group did not differ significantly from each other, only the CFS group was significantly lower than control (Fisher's Protected Least Significant Difference test; P < .05). Mean performance on the Similarities test did not differ among the three groups (F = 0.58). In addition, there were significant differences among the three groups in mean BDI scores (F[2,31] = 7.6; P < .01). The CFS and MS groups did not differ significantly from each other, and both groups showed a statistically significantly elevated mean BDI score relative to the control group (Fisher's Protected Least Significant Difference test; P < .05). No significant correlations were found between BDI scores and PASAT total scores (CFS, r = -.21; MS, r = .13; control, r = .27), or between BDI and Digit Span Test (CFS, r = -.32; MS, r = -.40; control, r = -.19). Results of the PASAT and Digit Span Test were significantly correlated in the CFS group (r = .71; P < .01), but not in the MS (r = .06) or control groups (r = .49). CONCLUSIONS: These results indicate that subjects with CSF and subjects with MS show significant impairment on a test of complex concentration when compared with appropriate controls. The data suggest that subjects with CFS and subjects with MS have difficulty on tasks that require the simultaneous processing of complex cognitive information. Selective impairment in information processing efficiency may lie at the

Adult↗
PubMed2006

Controlling hippocampal output: the central role of subiculum in hippocampal information processing.

The subiculum has a central position between the hippocampus proper and entorhinal and other cortices, as well as a range of subcortical structures. The functional role of subiculum within the hippocampal formation circuit remains largely unexplored and a theoretical and experimental consensus on its functions has yet to emerge. Presented here is a simple and speculative model of the functions of the subiculum, based partly on anatomical, behavioural and neurophysiological considerations. The model suggests, firstly, that the subiculum acts to amplify hippocampal output, given the prominent bursting behaviour of its neurons and, secondly, that there is a dorso-ventral segregation of function within the subiculum. The dorsal component appears principally concerned with the processing of information about space, movement and memory, whereas the ventral component appears to play a major regulatory role in the inhibition of the HPA axis.

Action Potentials↗
PubMed2005

Craniofacial inputs to upper cervical dorsal horn: implications for somatosensory information processing.

The aim of this study was to characterize the properties of somatosensory neurons in the first 2 cervical spinal dorsal horns (C1 and C2 DHs) and compare them with those previously described for the rostral subnucleus caudalis (rVc). A total of 74 nociceptive neurons classified as wide-dynamic-range (WDR) or nociceptive-specific (NS), as well as 72 low-threshold mechanoreceptive (LTM) neurons, was studied in urethane/chloralose-anesthetized rats. The majority of LTM neurons were located in laminae III/IV and had a small mechanoreceptive field (RF) that included the posterior face and cervical tissues. In contrast, the nociceptive neurons were located in laminae I/II or V/VI, and the RF of each C1 and C2 DH nociceptive neuron included a part of the face and in 47% of them the RF included a region supplied by upper cervical afferents. There was a gradual caudal shift in the neuronal RF from nasal/intraoral tissues towards the neck as recording sites progressed from rVc to C1 and C2 DHs. In contrast to LTM neurons, many C1 and C2 DH nociceptive neurons received mechanosensitive convergent afferent inputs from cervical and craniofacial deep tissues (e.g., tongue muscles or temporomandibular joint), and over 50% could be activated by hypoglossal (XII) nerve electrical stimulation. We propose that C1 and C2 DHs represent part of the caudal extension of the Vc, and that Vc and C1 and C2 DHs may act together as one functional unit to process nociceptive information from craniofacial and cervical tissues, including that from deep craniofacial tissues.

Afferent Pathways↗
PubMed1997

Information processing and symmetry-breaking in memory evolutive systems.

The aim of this paper is to evaluate the role of symmetry and symmetry-breaking processes on the complex information processing developed by hierarchical evolutionary natural systems, such as biological, neural, social or cultural systems. The study is conducted in the frame of the Memory Evolutive Systems, which give a mathematical model of these systems. The dynamics of a MES is modulated by the competition between a net of internal regulation centers which act apart-but encode overlapping strategies which have to be equilibrated. The main characteristics of these systems, at the root of their complexity and adaptability, is a symmetry-breaking in the passage from a higher (or macro) level to a lower (or micro) level: several disparate sub-systems with different comportments at the micro level can be undistinguishable at the higher macro level because of a similar macro behavior (Multiplicity Principle). It is responsible for the development of a dialectics between heterogeneous regulation centers, and for the emergence in time of more and more complex objects. An application to neural systems vindicates an emergentist dynamical reduction of mental states to physical states.

Animals↗
PubMed1997

Why is the alphabetically middle letter in a multiletter array so hard to determine? Memory processes in linear-order information processing.

In 3 experiments, participants identified target letters in multiletter strings of different interletter steps. Results show that the alphabetically extreme targets in the arrays (A or C in BCA) were consistently identified faster than were the interior letters, with the alphabetically middle target (B in BCA) identified most slowly. Distance effects were not consistent across different targets. The findings are not consistent with the ends-inward serial search, comparison, and serial search plus comparison models. The data suggest that an interior target was identified by first identifying the terminal letter and then mentally constructing the linear order inward by probabilistically using either a comparison or an interitem serial search process to achieve maximal efficacy. This suggestion is consistent with the ends-inward construction theory of linear-order learning.

Analysis of Variance↗
PubMed2006

Lesions of the dorsal hippocampus or parietal cortex differentially affect spatial information processing.

The present experiments used 2 versions of a modified Hebb-Williams maze to test the role of the dorsal hippocampus (dHip) and parietal cortex (PC) in processing allocentric and egocentric space during acquisition and retention. Bilateral lesions were made to either the dHip or PC before maze testing (acquisition) or after maze testing (retention). The results indicate that lesions of the dHip impair allocentric maze acquisition, whereas lesions of the PC impair egocentric maze acquisition. During retention, lesions of the PC produced a significant impairment on both maze versions, whereas lesions of the dHip produced short-lived, transient impairments on both maze versions. These results suggest that during acquisition, the hippocampus and PC process spatial information in parallel; however, long-term retention of spatial information requires the PC with the dHIP as necessary for retrieval and/or access but not necessarily storage.

Analysis of Variance↗
PubMed1986

Age-related slowing in semantic information processing speed: an individual differences analysis.

This study investigated age differences in the speed of processing semantic information. Thirty young adults and 25 older adults completed five reaction time (RT) tasks: simple RT, two-choice RT to nonverbal stimuli, and three tasks measuring speed of making semantic judgments. The data were used to examine individual differences in RT factors, estimated by means of confirmatory factor analysis. All three semantic RT tasks loaded on a single semantic RT factor, with equivalent factor loadings for young and older participants, indicating that the three tasks were measuring a common factor of semantic memory access speed (SMA). The two groups differed significantly in the covariances among the RT factors; most important, the SMA factor had a higher correlation with a two-choice RT factor in the older group. This finding is taken as support of individual differences in age-related slowing on these two RT factors.

Adult↗
PubMed1981

Temporal information processing in speech perception.

For a set of formal rules for the phonetic interpretation of speech during its perception one should have data concerning a possible structure and parameters of a subjective mechanism for processing temporal information, from segmenting the speech signal to making phonetic decisions. At present such data cannot be found in the literature. An attempt has been made to find out more about some parts of the subjective mechanism of duration measurement and comparison by studying the perception of tempo changes in short sound sequences. Running or 'momentary' tempo is shown to be the feature of tempo change perception, and possible procedures for its detection have been tested. A computational technique for getting the quantitative parameters of the mechanism is briefly described.

Humans↗
PubMed1975

Information processing limits: the effects of information load and age.

As a test of the effects of age and information load Ss performed a visual and auditory discrimination task under conditions requiring division of attention. Amount of stimulus information was determined by the number of stimulus alternatives which could occur in a set of trials. Performance by 12 Ss over age 40 was impaired in comparison to 12Ss under age 40. Performance for all Ss was a function of amount of information, but there was no Age X Information Load interaction. It has been reported in the literature that age-related performance decrements are correlated with task complexity. These data indicate that amount of information is not a critical dimension of task complexity as it contributes to age-related performance deficits.

Adult↗
PubMed2002

[Analysis of the morphological substrate of information processing in the dog brain pallidal complex based on organizational characteristics of its afferent projections].

Projections from functionally diverse cortical and subcortical structures (cortex, amygdaloid body, substantia nigra, ventral tegmental area, and thalamus) to the pallidum (globus pallidus, entopeduncular nucleus and ventral pallidum) were studied in dogs using the method of axonal transport of the retrograde markers. Anatomical aspects of both the functional heterogeneity of the pallidal structures and integrative processing of information which underlie the mechanisms of adaptive behavior, were analyzed on the basis of the results obtained.

Afferent Pathways↗
PubMed1992

Information processing in the dentate gyrus.

The dentate gyrus is viewed as playing a major role in the generation of epileptiform activity. The ramifications of disrupted neuronal activity in the dentate gyrus are discussed with emphasis on the role of the dentate gyrus in processing sensory information. Several features of conditioned auditory-evoked potentials reflective of activity in the perforant path are described with respect to the activity of dentate granule cells. Comparisons of the sequential changes which occur in the perforant path synaptic activity and dentate granule cell discharge reveal an inverse relationship between synaptic input from the perforant path and degree of cell firing on any given trial. This inverse relationship is addressed in terms of extra-hippocampal projections to the cortex as well as recurrent connections to the enthorhinal area and the cells of origin of the perforant path. It is concluded that the perforant path regulates the response of the dentate granule cells to sensory input from the neocortex by decreasing synaptic drive when granule cell activity is high and increasing that synaptic drive when granule cell activity is low. This extra-hippocampal control of perforant path activity serves to 'clamp' the dentate granule cell response rate within a tightly controlled range to guarantee that granule cells will have some response capacity to 'unexpected' sensory experiences.

Afferent Pathways↗