Search PubMed⌕ Search

Biomedical subjects

J P Banquet

Publications and source records attributed to J P Banquet.

At least 19 recordsLinked to original sources
PubMed2005

A hierarchy of associations in hippocampo-cortical systems: cognitive maps and navigation strategies.

In this letter we describe a hippocampo-cortical model of spatial processing and navigation based on a cascade of increasingly complex associative processes that are also relevant for other hippocampal functions such as episodic memory. Associative learning of different types and the related pattern encoding-recognition take place at three successive levels: (1) an object location level, which computes the landmarks from merged multimodal sensory inputs in the parahippocampal cortices; (2) a subject location level, which computes place fields by combination of local views and movement-related information in the entorhinal cortex; and (3) a spatiotemporal level, which computes place transitions from contiguous place fields in the CA3-CA1 region, which form building blocks for learning temporospatial sequences. At the cell population level, superficial entorhinal place cells encode spatial, context-independent maps as landscapes of activity; populations of transition cells in the CA3-CA1 region encode context-dependent maps as sequences of transitions, which form graphs in prefrontal-parietal cortices. The model was tested on a robot moving in a real environment; these tests produced results that could help to interpret biological data. Two different goal-oriented navigation strategies were displayed depending on the type of map used by the system. Thanks to its multilevel, multimodal integration and behavioral implementation, the model suggests functional interpretations for largely unaccounted structural differences between hippocampo-cortical systems. Further, spatiotemporal information, a common denominator shared by several brain structures, could serve as a cognitive processing frame and a functional link, for example, during spatial navigation and episodic memory, as suggested by the applications of the model to other domains, temporal sequence learning and imitation in particular.

Action Potentials↗
PubMed2004

Spatial navigation and hippocampal place cell firing: the problem of goal encoding.

Place cells are hippocampal neurons whose discharge is strongly related to a rat's location in the environment. The existence of such cells, combined with the reliable impairments seen in spatial tasks after hippocampal damage, has led to the proposal that place cells form part of an integrated neural system dedicated to spatial navigation. This hypothesis is supported by the strong relationships between place cell activity and spatial problem solving, which indicate that the place cell representation must be both functional and in register with the surroundings for the animal to perform correctly in spatial tasks. The place cell system nevertheless requires other essential elements to be competent, such as a component that specifies the overall goal of the animal and computes the path required to take the rat from its current location to the goal. Here, we propose a model of the neural network responsible for spatial navigation that includes goal coding and path selection. In this model, the hippocampal formation allows for place recognition, and stores the set of places that can be accessed from each position in the environment. The prefrontal cortex is responsible for encoding goal location and for route planning. The nucleus accumbens translates paths in neural space into appropriate locomotor activity that moves the animal towards the goal in real space. The complete model assumes that the hippocampal output to nucleus accumbens and prefrontal cortex provides information for generating solutions to spatial problems. In support of this model, we finally present preliminary evidence that the goal representation necessary for path planning might be encoded in the prelimbic/infralimbic region of the medial prefrontal cortex.

Action Potentials↗
PubMed2002

From view cells and place cells to cognitive map learning: processing stages of the hippocampal system.

The goal of this paper is to propose a model of the hippocampal system that reconciles the presence of neurons that look like "place cells" with the implication of the hippocampus (Hs) in other cognitive tasks (e.g., complex conditioning acquisition and memory tasks). In the proposed model, "place cells" or "view cells" are learned in the perirhinal and entorhinal cortex. The role of the Hs is not fundamentally dedicated to navigation or map building, the Hs is used to learn, store, and predict transitions between multimodal states. This transition prediction mechanism could be important for novelty detection but, above all, it is crucial to merge planning and sensory-motor functions in a single and coherent system. A neural architecture embedding this model has been successfully tested on an autonomous robot, during navigation and planning in an open environment.

Animals↗
PubMed2001

Temporal order and spatial memory in schizophrenia: a parametric study.

Spatial working memory has been shown to be impaired in schizophrenia. In contrast, memory for temporal order has been poorly studied in patients with schizophrenia. The aim of this study was to compare and to further characterize spatial working memory and sequence reproduction deficits in patients with schizophrenia under stable medication by manipulating cues (pattern versus sequence), delay, set-size and response type in various recall and recognition tasks. This allowed us to dissociate processes as encoding, retention and retrieval and to compare the performance of patients with schizophrenia to the performance of patients with prefrontal lesions, who have been previously tested in the same tasks. Our results show that increase of the set-size and of the delay decreased performance of both groups, and that these factors had larger detrimental effects in patients with schizophrenia than in controls. Furthermore, comparison between tasks revealed retention and retrieval deficits in schizophrenia. Finally, patients with schizophrenia showed impairments not only in recall but also in sequence recognition tasks with delay. This is in contrast to patients with prefrontal lesions, who have previously been shown to have intact recognition of sequences after a delay. These results suggest that the working memory deficit in schizophrenia cannot be restricted to a prefrontal dysfunction.

Adult↗
PubMed1999

Planning dysfunction in schizophrenia: impairment of potentials preceding fixed/free and single/sequence of self-initiated finger movements.

To test the hypothesis of a planning dysfunction in schizophrenia using a precise temporal definition, the readiness potential (RP), a negative cortical wave preceding self-initiated movements and reflecting motor preparation processes, was studied in patients under stable medication and in controls. The supplementary motor area (SMA), known to be involved in the generation of the RP, has also been implicated in movement selection (fixed versus free) and complexity (single versus sequence). This is the first study using RP for the assessment of the influence of these factors on motor preparation in schizophrenics. Our results show that schizophrenics' RP amplitude is significantly lower than in controls at central and contralateral electrodes. However, RP amplitude increases with task difficulty in both groups, offering important new insight into classical SMA hypoactivation in schizophrenics performing motor tasks. Topographic analysis shows that RP amplitude is, for both groups, significantly higher in sequence than in single movements at fronto-central sites and higher for free than for fixed movements at centro-parietal sites. Finally, RP onset occurs significantly later in schizophrenics than in controls. These results support the view of a motor-preparation and decision-making dysfunction in schizophrenia. They are interpreted within the framework of a fronto-striatal disorder in this disease.

Adult↗
PubMed1997

Functional EEG mapping and SPECT in detoxified male alcoholics.

Fifteen alcoholics diagnosed according to DSM-III-R, who were detoxified for at least 2 weeks and showed no clinical withdrawal signs, were investigated with 16 channel EEG mapping during resting, manumotor and music perception conditions, and were compared with 13 control persons. Single photon emission computed tomography (SPECT) using hexa-methyl-propilene-amine-oxime (HMPAO) labeled with 99m-technetium (99mTc) as tracer was performed separately (in patients only) and submitted to semiquantitative region of interest (ROI) analysis in 2 slices, 6 and 10 cm above canthomeatal line, respectively. Resting EEG showed increased power values in fast beta frequency band for the detoxified alcoholics. On cortical stimulation, patients showed signs of pathological EEG reactivity. Correlations of EEG parameters to cerebral blood flow (CBF) values (patients only) yielded coefficients around zero for all frequency bands (signs of uncoupling). All findings point to organic brain dysfunctions in these patients which extend beyond the period of withdrawal.

Adult↗
PubMed1995

Retardation of mentation in depressives: Posner's covert orientation of visual attention test.

A double-key version of Posner's covert orientation of visual attention test, which involves shifting of preparation for response from one side to another, was administered to 32 depressives and 32 controls to evidence retardation of mentation in depressives and compare it to symptom-rating scales. Results showed depressives' overall response times to be consistently slower than controls. The time of maximal response preparation occurred later in depressives than in controls, showing clear evidence of pure retardation of mentation (not mixed with motor processes). This slowing of mentation was strongly correlated with observable psychomotor retardation but not with depressive severity.

Adult↗
PubMed1993

EEG mapping investigations of psychomotor and music perception brain dysfunction in untreated schizophrenic patients.

Twenty-six untreated schizophrenic inpatients and 34 control persons were investigated using 16-channel EEG mapping during resting, manumotor and music perception tasks. Power values of activation tasks were each referenced to a separate, immediately preceding resting condition, using conventional delta, theta, alpha and 2 beta frequency bands. Results in delta and alpha bands, which maximally separated the two groups, are reported only for space reasons. Results indicated a "nonreactivity" (in all frequency bands) on the two activation paradigms in schizophrenic patients as a group. Major gender effects were obtained in normal persons, but not signs of nonreactivity comparable to patients. Subdividing patients exclusively by means of their EEG changes on activation produced meaningful clinical subgroups of "positive/negative" schizophrenics. This latter finding could contribute towards clinical utility of EEG mapping in psychiatry.

Adult↗
PubMed1991

Brain dysfunction in psychiatric patients during music perception measured by EEG mapping: relation to motor dysfunction and influence of neuroleptic drugs.

We report here our findings on music perception obtained as a companion study to the investigation with 16-channel EEG mapping in psychiatric patients during motor activation, published recently elsewhere. We decided to add on a study of this functional circuit, since there is evidence that it is disturbed in various psychiatric patient groups (another "functio laesa"). Involved in the study were 23 male and 25 female schizophrenics, 11 male and 18 female non-endogenously depressed patients (not presently under medication, i.e. drug-naive or wash-out period from 1 week to 17 years), 26 male and 37 female endogenously depressed patients (medicated with tri- or tetracyclic antidepressants and/or benzodiazepines; no lithium), and 22 male and 17 female control subjects (i.e. n = 179). We compared resting conditions after a special relaxation procedure with three music perception tasks: (1) a standardised rumba rhythm generated by a keyboard and delivered binaurally by earphones, (2) the same as an arpeggio in D major, and (3) the same as an arpeggio with a tonic-subdominant-dominant cadence. Major results were obtained in the delta and alpha frequency bands, yielding signs of "diffuse hyperactivation", most prominent in schizophrenic males, and not observed to a similar extent in any other patient group or in normal controls. Interestingly, there were major sex differences, yielding a more diffuse EEG activation pattern in normal females than in males and thus possibly obscuring signs of brain function diffusion in female patients. Viewing our broader evidence of similar brain dysfunction when examining motor functional circuits, especially in schizophrenics, these findings provide further evidence of a brain disorganization with lack of laterality/diffusion which may be found in subgroups of these patients and not in other psychiatric disorders. In schizophrenic patients, these EEG signs of "diffuse hyperactivation" on simple motor and/or music stimulation were reduced to nearly normal by neuroleptic medication. The latter finding may contribute to possible clinical applications of EEG mapping, considering the EEG's unique suitability for long-term brain function monitoring. Other neuroimaging methods like SPECT and PET should be used for additional "external validation".

Adolescent↗
PubMed1986

EEG mapping of left hemisphere dysfunction during motor performance in schizophrenia.

With a newly developed system of brain electrical activity mapping we studied 10 right-handed, neuroleptic-treated schizophrenics (five of the disorganized, five of the paranoid type, corresponding to 295.1 and .3 in DSM-III), compared with 10 normal controls. Increasingly complex motor tasks were used for cortical activation, all functional states being referenced to resting states recorded after a special relaxation program. We found higher delta and theta amplitudes during rest, as noted in previous studies, and lower beta power values. As a major result, however, we found a widespread left hemisphere dysfunction in schizophrenics, predominantly in the left primary sensory and motor areas. Additionally, we found signs of a "compensatory" overactivation in patients in motor tasks, when this hemisphere is not "used" by normal persons. The results support our findings obtained with this method during multisensory motor coordination in schizophrenia. The results in these patients suggest that these are not merely vigilance, attention, or motivation dysfunctions, but rather specific cortical correlates of impaired motor performance.

Acute Disease↗
PubMed1983

Inter- and intrahemispheric relationships of the EEG activity during sleep in man.

Using both linear and non-linear multivariate analysis associated with classical statistical tests, inter- and intrahemispheric relations of the cerebral electrical activity (EEG) during sleep were analysed by spectral power, coherence (CH) and correlation functions. Whilst a steady diffuse decrease in linear phase relations (CH) appeared during the evolution from waking to slow wave sleep, paradoxical sleep was associated with low interhemispheric CHs (mostly frontal) and high intrahemispheric CHs. Simultaneously, at a much lower degree of temporal resolution (25.6 sec periods), the correlations between EEG activities of identical frequencies but of different topographies were highly positive during sleep, whilst the correlations between activities of different frequencies at the same site on the scalp varied according to sleep states and frequencies. These findings suggest the interpretation of deep sleep in man as a state of transient partial disconnection between hemispheres.

Adult↗
PubMed1981

Effect of task and stimulus probability on evoked potentials.

Some experimental data demonstrate the existence of at least two different P300s distinguished by latency, topography and functional significance. These positive waves are preceded by a negative component which has been labelled N200. The purpose of this study was to analyze the modifications of these negative and positive components according to probability and task (GO vs. NOGO) in order to better understand the significance of each of them in terms of stages of information processing. Six normal subjects were tested twice on separate days, in a GO-NOGO paradigm. Auditory stimuli - high pitch (GO) and low pitch (NOGO) - were presented in three different occurrence probability combinations: 0.2/0.8; 0.5/0.5; 0.8/0.2, in successive blocks. In both GO and NOGO responses, a vertex N200 component was followed by two positive waves - the first peaking at 300 msec at Cz (Cz : P300), the other one Ca 400 msec at Pz (Pz : P400). An inverse relation between amplitude and probability was seen for the three components but it was twice as large for P400 as for P300. A task effect was only seen for N200, the amplitude and latency of which increased in the GO condition. From the first session to the second, the amplitude of N200 decreased whereas that of P300 increased.

Adult↗
PubMed1981

[Spatio-temporal organisation of EEG in sleep stages (author's transl)].

The purpose of this study was to test the hypothesis of the existence and independence of multiple generators of the sleep rhythms. Spatio-temporal analysis of the sleep EEG of 6 subjects was realised both visually and by multi-dimensional analysis of the parameters of spectral power (PS) and coherence (CH). Four results have been demonstrated: a relative decrease of the global CH during the transition from waking to deep sleep, with reappearance of high CH during paradoxical sleep (PS); (2) a negative correlation between the activities of frontal and occipital regions, mostly for alpha and theta frequencies; (3) a dominance of the activity of one hemisphere (the left here) during sleep, with a possible change of this dominance during paradoxical sleep; (4) a slow oscillation of power (SOP) with a periodicity of 1-5 min. variable according to subjects and sleep stages. These results suggest the existence of two partially independent groups of generators (anterior and posterior) for the slow frequencies of sleep.

Electroencephalography↗