Biomedical subjects

C Grillon

Publications and source records attributed to C Grillon.

32 records · Page 2Linked to original sources

PubMed1990

Increased distractibility in schizophrenic patients. Electrophysiologic and behavioral evidence.

The inability of schizophrenics to filter irrelevant information has often been implicated in the psychopathology of schizophrenia. Despite numerous attempts at characterizing the behavior of schizophrenics in the presence of distractors, evidence of increased distractibility has been equivocal due to the difficulty of assessing simultaneously the behavioral and neurophysiological effects of distracting stimuli. We report the results of an experiment in which event-related potential and performance measures were used to assess distractibility during reaction time tasks under different distracting conditions. The results supported the view of an increased distractibility in schizophrenic patients. Event-related potential data suggested that in schizophrenic patients, a reduced amount of processing resources is allocated to process external stimuli and attention is abnormally apportioned to task-irrelevant vs task-relevant stimuli.

Adolescent↗

PubMed1990

Effects of rare non-target stimuli on brain electrophysiological activity and performance.

In order to assess the effects of non-target stimuli on task performance and electrophysiological activity, 16 subjects performed reaction time (RT) experiments under 3 conditions. In all conditions, subjects had to press a button upon detection of rare (15%) target stimuli (1600 Hz) presented among frequent (85%) non-target stimuli. The 3 conditions differed based on their non-target stimuli. In one condition, the non-targets consisted of 'standard' stimuli (900 Hz). In the two other conditions, rare and deviant non-target stimuli were randomly added to the standard stimuli. These deviant non-target stimuli consisted of either constant (700-Hz tones) or novel (buzzes, filtered noises and other unusual sounds) stimuli. Both the rare target and non-target stimuli elicited P300, responses. Behavioral (RT) and electrophysiological (event-related potential) data showed that stimuli that followed standard stimuli were processed differently compared to stimuli that followed deviant non-target stimuli. In the conditions containing deviant non-target stimuli, the P3b to the target stimuli was smaller and later, and the mean RT longer than in the condition with no deviant stimuli. These behavioral and electrophysiological changes induced by the deviant non-target stimuli were discussed with reference to two factors, distraction and increased level of task difficulty. It was suggested that each of these factors were differentially sensitive to the novelty of the rare deviant stimuli.

Acoustic Stimulation↗

PubMed1990

Cell surface lectins of human granulocytes: their expression is modulated by mononuclear cells and granulocyte/macrophage colony-stimulating factor.

This paper presents the characterization of a sugar-specific receptor on the surface of human circulating polymorphonuclear cells. With the help of fluorescent neoglycoproteins and flow cytometry, a receptor was identified as being specific for alpha-L-rhamnosyl residues. The number of receptors was 55,000/cell and their affinity reached 2 x 10(8) l mol-1. This number changed as a function of the biological state of the cells. Indeed, receptor expression was modulated by the presence of other cells. T cells and B cells increased the number of receptors on the granulocyte surface. Expression of the alpha-L-rhamnose-specific lectin was dependent on lymphocyte derived soluble factor(s), which induce(s) growth and differentiation of polymorphonuclear phagocytes. Granulocyte/macrophage colony-stimulating factor (GM-CSF) specifically produced a significant increase in the number of receptors for alpha-L-rhamnose (2-10-fold/cell). This modulation was independent of protein kinase C activators such as phorbol ester, which produced no effect on alpha-L-rhamnose receptor expression. These findings demonstrate that GM-CSF may stimulate post differentiation functions and properties of mature granulocytes.

Antibodies, Monoclonal↗

PubMed1989

Brainstem and middle latency auditory evoked potentials in autism and developmental language disorder.

Brainstem auditory evoked potentials (BAEP) and middle latency responses (MLR) were studied in 8 nonretarded subjects with infantile autism (mean age = 23.3, SD = 2.8), 8 subjects with receptive developmental language disorder (mean age = 16.3, SD = 1.4), and normal control subjects matched to each group for age, gender, and Performance IQ. Click stimuli were delivered monaurally to the left and the right ear and binaurally for both the BAEPs (70-dB HL, 7/sec) and the MLRs (60-dB HL, 13/sec). Amplitudes and latencies (Waves I to VI), interwave latencies (III-V, I-V, and I-III), and Wave I/V amplitude ratio of the BAEPs were determined for each group. For the MLR study, Wave Na, Pa, and Nb latencies, and Wave Na-Pa and Pa-Nb amplitudes were calculated. There were no consistent differences in the BAEP and MLR characteristics of the control and the experimental groups. These results suggest that the abnormal cognitive processes indexed by the cognitive and attention-related event-related potential components in infantile autism and receptive developmental language disorder are not due to abnormal sensory processing in the brainstem and in areas central to the brainstem whose activity generates the BAEPs and MLRs.

Adolescent↗

PubMed1989

Pathophysiologic findings in nonretarded autism and receptive developmental language disorder.

In nonretarded autistic, receptive developmental language disordered, and normal subject groups, we recorded in auditory and visual target detection tasks two neurophysiological components of the event-related brain potential, Nc and P3b. Existent research shows that, in normals, Nc and P3b appear early in development, are associated with attention and memory processes, and are endogenous which means that they are triggered by internal, consciously initiated attentional and cognitive mechanisms and that they can be triggered even by the omission of sensory stimulation so long as it has meaning or importance for the subject. In this report, Nc and P3b were recorded in response to auditory and visual stimulation and to the omission of auditory and visual stimulation. Consistent with the hypothesis that non-retarded autism involves abnormal attentional and cognitive responses to important information, P3b was found to be smaller than normal and Nc was small and often absent in the nonretarded autistic group even under the condition when no auditory language or sensory processing was required. Receptive developmental language disorder has been linked with difficulties in processing sequences of auditory stimuli, and in this study P3b was found to be somewhat enlarged in this group even under the conditions when P3b was elicited by stimuli separated by 1 sec and also when P3b was elicited by the omission of stimulation.

Action Potentials↗

PubMed1988

Visual memory processes in high-functioning individuals with autism.

High-functioning autistic individuals were compared with age-matched normal control subjects on a visual recognition memory task. In order to evaluate the effects of "meaning" and "delay" on the visual memory of autistic individuals, meaningful (pictures) and meaningless (nonsense shapes) stimuli were presented visually in no delay and 1-minute delay intervals to both groups. It was concluded that autistic subjects perform particularly poorly on meaningless material, but they are able to utilize meaning to aid their visual memory. Contrary to expectations, 1-minute delay intervals did not differentially affect the visual memory performance of autistic individuals compared to control subjects. The results do not support the idea of a simple parallel between autism and mediotemporal lobe amnesias. The visual memory performance of the autistic subjects was discussed in the light of the possibility of a subtle involvement of the mediotemporal brain structures and inflexible cognitive strategies poorly suited to encode novel information.

Adolescent↗

PubMed1987

EEG topography of response to visual stimuli in generalized anxiety disorder.

EEG activity was recorded in 11 normal subjects and 19 patients with generalized anxiety disorder (GAD) at rest and while they were viewing a series of ten 4 sec continuous lights. Topographical cortical changes were assessed using 32-channel EEG power estimate maps. The percent changes from baseline to stimulation, for the first 5 and the last 5 light stimuli, were calculated and topographically mapped. Patients with GAD showed less decrease in alpha activity during the first 5 stimuli and more alpha activity during the last 5 stimuli in comparison to normal controls. Delta, theta, alpha, beta I and beta II did not show any difference during the resting periods. The topographical distribution of response to light was different in each group. Normal controls had a parieto-occipital reactivity and GAD patients a centro-parietal one with the maximum difference between the two groups being located in the occipital region. During the stimulation, beta I activity was decreased in controls and increased in patients. The diminishing reactivity of the patients is interpreted as a diminution of attention to external stimulation because of competing internal interferences. The pattern of regional reactivity suggests the importance of the centro-parietal and/or occipital regions in anxiety.

Adult↗

PubMed1987

[Long latency auditory evoked potentials: value of multichannel analysis and of high-resolution graphic mapping].

Auditory Evoked Potentials maps (AEP) were computed from 32 simultaneously recorded channels over both hemispheres using a linear interpolation algorithm. Reference electrode was extracephalic. Stimulus was a 781 Hz tone (intensity 70 dB HL, duration 256 msec). Average AEP were from 128 responses to randomly delivered stimuli. Direct current and frequencies over 50 Hz were removed by means of a digital filter (FFT). Results from 15 subjects showed before 120 msec a symmetrical response of AEP at vertex with left ear, right ear or binaural stimulation. Between 120 and 170 msec, maps of evoked responses were asymmetrical showing greater potentials over temporal areas contralateral to the stimulated ear.

Cerebral Cortex↗

PubMed1986

Computed EEG topography of response to visual and auditory stimuli.

EEG activity was monitored in 15 normal subjects at rest and while they were given 10 sec continuous light or tone stimuli of different intensities. Topographical cortical changes were assessed using 16-channel EEG power estimate maps of the left hemisphere. Statistical analyses were performed using analyses of variance and t test, and the reactivity of the EEG, i.e., the percent change from the baseline state, in response to stimulation, was topographically mapped. Significant EEG reactivity was recorded in alpha, theta and delta bands without modification in the beta band. Stimulation-induced effects were maximum in the posterior part of the brain for both tone and light. The light effect was stronger than tone in the alpha band, but no differences in modality effect were recorded in the delta or theta band. Analysis of frequency bands within the alpha and theta band revealed a different pattern of reactivity with different regional involvements for tone and light. EEG reactivity occurred mainly in 7-10 Hz frequency bands with no significant change in 5, 6, 11, 12 and 13 Hz. Reactivity was maximal in the temporal area during tone for 7-9 Hz and in the occipital region during light for 8-10 Hz. The 8 and 9 Hz frequency bands showed increased blocking with an increase in stimulus intensity. Taken together, the results indicate that visual and auditory stimuli both produce an EEG amplitude decrease which is greatest over their respective primary sensory cortex.

Adult↗

PubMed1985

Hoffmann reflex variations produced by task demand characteristics.

It has been shown that monosynaptic reflexes could be facilitated or inhibited during tasks differing in nature. The amplitude of the Hoffmann reflex (H reflex) and heart rate have been studied during the performance of two versions of a mental task and a tracking task varying in degree of difficulty. Modification of the H reflex does not depend upon the nature of the task. A slight increase in cardiac rhythm and a facilitation of H reflex during easy tasks and a marked increase in cardiac rhythm associated with inhibition of H reflex during difficult tasks were observed. The increase in H reflex would be due to an activation of the reticular formation. The inhibition of motor response can be attributed to an effortful process which develops when the tasks become difficult.

Adult↗

PubMed1983

Morphine pretreatment reduces clomipramine effect in mouse forced-swimming test.

It had previously been shown that naloxone inhibits the effect of clomipramine both in a pain test in the forced-swimming test in mice which is proposed as an antidepressant study model. Evidence is reported of a decrease in activity of clomipramine in the forced-swimming test in mice after morphine pretreatment. The hypothesis of an interaction with mu-opiate receptors is considered.

Animals↗

PubMed1983

[Activation motor response in depressive states. Changes in the Hoffmann reflex during psychomotor testing].

Psychophysiological response of activation was explored both in control and depressed patients before and after antidepressant treatment. Hoffmann reflex (H reflex) and heat rate were recorded. Two psychomotor tests were studied in order to modify the level of vigilance. Control subjects had two different psychophysiological responses: slight increase of cardiac rhythm together with facilitation of H reflex or marked increase of cardiac rhythm associated with inhibition of H reflex. Depressed patients always showed an increase in H reflex during each task. H reflex was reduced only when patient recovered after a period of treatment. In both populations, heart rate for a given test was modified in the same way. Results are discussed in the light of the existence of two different activating systems. In depressed patients the lack of inhibition of H reflex could be explained by the decrease of initial arousal.

Adult↗

PubMedDate not supplied

Effects of task relevance and attention on P3 in schizophrenic patients.

The P3 component of the event-related potentials (ERPs) to auditory task-relevant and task-irrelevant stimuli in 'Attend Auditory' (i.e., reaction time task) and 'Attend Visual' (i.e., when the auditory stimuli were being ignored) conditions was investigated in 13 RDC/DSM-III diagnosed schizophrenic patients. ERPs were recorded from Fz, Cz, and Pz. Compared to controls, schizophrenics had a significantly smaller P3 in the Attend Auditory than in the Attend Visual condition and to the task-relevant than to the task-irrelevant stimuli. Furthermore, the patients' P3 response to the most salient task-irrelevant stimuli in the Attend visual condition was normal. The results are discussed as suggesting that schizophrenics either allocate relatively more resources to task-irrelevant than task-relevant stimuli or that they fail to habituate to task-irrelevant stimuli.

Adult↗

PubMedDate not supplied

Middle latency auditory evoked potentials (MAEPs) in chronic schizophrenics.

Middle latency auditory evoked potentials were recorded in medicated chronic schizophrenics and controls at stimulation rates of 10/s, 2/s, and 1/s. Increasing the stimulation rate did not change Pa amplitude but decreased Pb amplitude. There was no difference between the two groups.

Acoustic Stimulation↗