Accelerated long-term forgetting and autobiographical memory disorders in temporal lobe epilepsy: One entity or two?

Temporal lobe epilepsy (TLE) is a type of epilepsy that often has a negative impact on patients' memory. Despite the importance of patients' complaints in this regard, the difficulties described by these patients are often not easy to demonstrate through a standard neuropsychological assessment. Accelerated long-term forgetting and autobiographical memory disorders are the two main memory impairments reported in the literature in patients with TLE. However, the methods used by different authors to evaluate long-term memory and autobiographical memory are heterogeneous. This heterogeneity can lead to differences in the observed results as well as how they are interpreted. Yet, despite the methodological differences, objectification of such memory deficits appears to be both specific and robust within this patient population. Analysis of the literature shows that accelerated long-term forgetting and autobiographical memory disorders share the same clinical characteristics. This leads to the assumption that they are, in fact, only one entity and that their evaluation may be done through a single procedure. Our proposal is to place this evaluation within the context of memory consolidation disorders. With such a perspective, evaluation of accelerated forgetting in autobiographical memory should consist of identifying a disorder in the formation and/or recovery of new memory traces.

[Motivations of requests for human immunodeficiency virus (HIV) infection screening at the Centers of Information and Anonymous and Free-of-Charge Screening. Study of 891 cases]. / Motivations des demandes de dépistage de l'infection par le virus de l'immunodéficience humaine (VIH) dans les Centres d'Information et de Dépistage Anonyme et Gratuit (CIDAG). Etude de 891 cas.

In France, human immunodeficiency virus (HIV) testing is usually performed in centers for information and anonymous cost-free detection (Centres d'Information et de Dépistage Anonyme et Gratuit, CIDAG). In this work, we studied the reasons people ask for HIV testing at the CIDAG in Lyons. Eight hundred and ninety one people were asked to give their reasons. The response ratio was 85% and the sex-ratio 1:1. Seventy-five percent of the people were single. The main motivation was the desire to begin a relationship with another person without using condoms. Nonetheless, we were impressed by the high level of high-risk behaviors. To our knowledge, this is the first study about motivations of outpatients at the CIDAG.

Step-length biofeedback device for walk rehabilitation.

A biofeedback gait training system for step length is proposed, adapted to the correction of spatial walking asymmetries by means of a simple, quick and reliable method for daily clinical use. The system is composed of a walkway and a gait analysis device (locometer) measuring the main temporal and distance factors of gait. The step length is imposed on the subject by lighted targets appearing on the walkway, alternately on the right and left side; the subject is asked to place a swinging foot on the lighted target. Feedback to the subject is supplied by direct visual information (the subject looking at the movement and the position of the foot with respect to the lighted target) and an acoustic signal delivered in real time when the length step error is greater than an allowed value. The method is validated on a population of hemiparetic patients who have suffered from a stroke and who have been reeducated with traditional rehabilitation methods. The patients were divided into two groups; one group following a gait training with biofeedback (BFB group) and one group following a gait training without biofeedback (reference group). Preliminary results are presented, showing a significant beneficial effect of the biofeedback method in increasing the step length of paretic limbs and in correcting step-length asymmetry.

Unusual visual stimulation in dynamic balance conditions: proposal for a space motion sickness test.

We previously demonstrated the efficiency of normal vision/unusual vestibular cues conflict to induce motion sickness. In the present study, we investigate whether, inversely, unusual visual information/normal vestibular function conflict also elicited motion sickness. The experiments were again carried out in dynamic balance conditions to increase proprioceptive input. Circular translation of the visual field with diplopia were produced by rotating Fresnel prismatic glasses. The stimulation triggered SMS-like symptoms and dynamic balance disturbance. A positive relationship was found between discomfort and balance disturbance. Unusual visual information should therefore be included in Space Motion Sickness susceptibility testing.

Evidence of the co-activation of alpha-motoneurones and static gamma-motoneurones of the sartorius medialis muscle during locomotion in the thalamic cat.

The activity in alpha and gamma efferent axon populations and in group I and group II afferent fibre populations innervating a flexor muscle, the sartorius medialis, was observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the overall activity of a thin, intact branch of the sartorius medialis nerve. The following results were obtained: (1) The gamma-motoneurones have a phasic behaviour characterized by a single discharge period during the hip flexion (swing phase of the step-cycle). (2) The gamma-motoneurones are co-activated with the homonymous alpha-motoneurones. (3) Between rhythmic alpha and gamma discharges, i.e. during the hip extension (stance phase of the step cycle), both alpha- and gamma-motoneurones were normally silent. However, in 5 out of 17 experiments, a few units of the gamma population fired at very low frequency. (4) Two observations indicate that the gamma-motoneurones that are co-activated with the alpha-motoneurones by central locomotor commands are predominantly of the static type. In actual locomotion, the rhythmic fusimotor discharges over-compensate the depressor effect on the firing rate of the group II afferents of the unloading of muscle spindles by the active shortening of the parent muscle. In fictive locomotion, when the transmission of the excitation is blocked by selective curarization in alpha skeleto-motor junctions alone, the rhythmic fusimotor discharges elicit in-phase modulations not only of the group I but also of the group II fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Discharge patterns of gamma motoneurone populations of extensor and flexor hindlimb muscles during walking in the thalamic cat.

Two monopolar recordings of the whole activity in a fine nerve branch innervating the gastrocnemius lateralis (GL) or the sartorius medialis (SM) muscle were obtained during spontaneous walking in thalamic cats. Using a special electronic device, the potentials of several groups of efferent (alpha and gamma) and afferent (I and II) fibres constituting the whole nerve activity were separated. In the present paper we compare the data obtained for an ankle extensor (GL) and a hip-knee flexor (SM) during the step cycle. In both muscles the gamma motoneurone population is activated in parallel with the alpha motoneurone population. Usually, between the cyclic locomotor discharges, the GL gamma neurones are tonically active whereas the SM gamma neurones are silent. During muscle contraction, the group I and II afferent discharges are both length and gamma dependent, but the prevailing factor is the muscle shortening for the GL afferents and the cyclic gamma drive for the SM afferents. Both dynamic and static fusimotor efferents appear to be activated during muscle contraction, but on indirect evidence it is suggested that dynamic action prevails in GL spindles whereas static action dominates in SM spindles.

Simultaneous recording of longitudinal displacements of both feet during human walking.

1. Recordings of longitudinal displacements of both feet have been performed by linking each foot to a length-voltage transducer by means of threads. The movement transmitted to the transducer was reduced by winding the thread around a sixteen strand pulley block. 2. The aspect of the displacement curves allows a direct analysis of the walk. Some typical curves of normal and pathological gaits are presented. Graphic measurements done on several right and left cycles of a 6 m walk episode in 50 adult subjects provided data to determine the mean and the standard deviation of spatial and temporal parameters of the walk. 3. An advantage of this method is to permit the measurement of the parameters of several successive cycles of both sides and so to detect changes in the length, the duration and the velocity of successive cycles of the same foot and of alternated cycles of both feet. This being important to characterize pathological gaits.

Efferent and afferent activity in a gastrocnemius nerve branch during locomotion in the thalamic cat.

The firing patterns of alpha and gamma efferent fibres and of group I and group II afferent fibres innervating the gastrocnemius muscle were observed during spontaneous locomotor movements in the thalamic cat. Multi-unit discharges of each kind of fibre were obtained by electronic sorting of the action potentials from the whole activity of a thin branch of gastrocnemius lateralis or medialis nerve. The main results were: During the locomotor cycle the activity of the afferent and efferent populations was highly modulated. alpha- and gamma-motoneurones were co-activated within the locomotor cycle during ankle plantar-flexion. The gamma discharge began to rise earlier and to fall later than did the alpha discharge. The amplitude of the gamma discharge, unlike that of the alpha discharge, was largely independent of the vigour of walking. Between the cyclic discharges, most of gamma populations were tonically active whereas alpha populations were silent. Subgroups of the alpha and gamma populations were not usually activated according to the cell-size principle, but, the activation of the latest gamma subgroup always preceded that of the earliest alpha subgroup. Modulation of the group I and II afferent discharges was closely related to the cyclic length changes of the parent muscle. Fusimotor activation during the active shortening of gastrocnemius muscle prevented the afferent discharges from pausing. The pattern of afferent and efferent activity during selective curarisation of the extrafusal junctions indicated that the discharge of static gamma-motoneurones is modulated during the locomotor cycle. After curarisation of both extrafusal and intrafusal junctions, an efferent-discharge pattern of central origin persisted alternately in extensor- and flexor-muscle nerves (fictive locomotion). The durations of the fictive locomotor cycle and of the cyclic discharge in the sartorius nerve were increased as a consequence of the suppression of phasic afferent inputs to the C.N.S. Maintained ankle dorsi-flexion slowed the fictive locomotor rhythm and elicited opposite effects, respectively excitation and depression, on the magnitude of the alpha and gamma discharges. Maintained ankle plantar-flexion scarcely perturbed the duration of the fictive locomotor cycle, but the duration of the sartorius-nerve discharge lengthened at the expense of that of the gastrocnemius discharge. Both gastrocnemius alpha- and gamma-motoneurones were depressed, the former considerably more than the latter. The roles of the gastrocnemius afferents and gamma-efferents during the locomotor cycle are discussed in the light of these results.

Effects of triceps stretch by ankle flexion on intact afferents and efferents of gastrocnemius in the decerebrate cat.

We describe the effects on group I and II afferents as well as alpha- and gamma-efferents of gastrocnemius muscles elicited by stretch and release of the triceps surae muscle performed by a dorsiflexion movement, a maintained dorsiflexion and release of the ankle joint. The experiments were made in decerebrated cats in which the neural loops between the muscles and the spinal cord were intact. Multi-unit discharges of each kind of fibre were obtained, electronically on-line, from two monopolar electrodes 4 mm apart on a small branch of the gastrocnemius lateralis or medialis nerve. Sensory and motor impulses were separated according to the opposite directions of their propagation, then both groups were further subdivided according to conduction velocity. The stretch reflex induced by ankle flexion was associated in eighteen out of nineteen experiments with reflex changes in the activity of the gamma-axon population of the gastrocnemius nerve branch. Facilitatory, depressor and biphasic (facilitatory-depressor) effects were observed, the particular type seeming to depend on the level of gamma tone and gamma-motoneurone size. Flexion release led to cessation of the alpha stretch reflex and to a rebound firing of the gamma-axon population. The lengthening reaction and the clasp-knife phenomenon occurred in certain preparations and were associated with reflex inhibition of the gamma-motoneurones. The over-all responses of group I fibres to triceps stretch showed dynamic and static components, whereas those of the group II fibres were, except in two examples, almost devoid of dynamic sensitivity. During release of stretch and as a result of the simultaneous rebound in gamma activity, the afferent discharges showed a very short pause, no pause, or even a rebound. The origins of the discharges of groups I and II muscle afferents and the factors (muscle length, active and passive muscle tension, reflex changes in fusimotor drive) influencing the activity of the receptors involved are considered as far as possible. Some aspects of the mechanisms of the fusimotor reflex are discussed.

Efferents and afferents in an intact muscle nerve: background activity and effects of sural nerve stimulation in the cat.

1. The background activity was observed in gamma and alpha efferent fibres and in group I and II fibres innervating the muscle gastrocnemius lateralis or medialis. The reflex effects of ipsilateral and contralateral sural nerve stimulations on the muscle efferents were analysed together with their consequences upon the afferents of the same muscle. The observations were made in the decerebrated cat without opening the neural loops between the muscle and the spinal cord.2. The multi-unit discharges of each category of fibres were obtained, on line, by an original electronic device (Joffroy, 1975, 1980) that sorted the action potentials from the whole electrical activity of a small branch of gastrocnemius lateralis or medialis nerve according to the direction and velocity of propagation of the potentials.3. The small nerve may be regarded as a representative sample of different functional groups of fibres conducting faster than 12 m.sec(-1) and supplying gastrocnemius muscles.4. Some gamma efferents were always tonically firing except when a transient flaccid state developed. Usually the alpha efferents were silent, probably because the muscle was fixed close to the minimal physiological length.5. Separate and selective stimulations of Abeta, Adelta and C fibres of ipsilateral and contralateral sural nerve showed that each group could induce the excitation of gamma neurones. The reciprocal inhibition period of alpha efferents during a flexor reflex was only once accompanied by a small decrease in gamma-firing.6. The reflex increase of over-all frequency of gamma efferents resulted from an increased firing rate of tonic gamma neurones and from the recruitment of gamma neurones previously silent. When the gamma efferents in the small nerve naturally occurred in two subgroups, the slower-conducting subgroup (mainly composed of tonic gamma axons) was activated before the faster-conducting subgroup (mostly composed by gamma axons with no background discharge). Some rare exceptions were found, however.7. The selective activation of gamma efferents could be obtained with short-and low-frequency stimulation. When, with stronger stimulations, gamma-alpha co-activation was observed, the onset of the gamma-firing increase preceded by 100-600 msec that of the alpha discharge in the small nerve. Likewise, the onset of the gamma-efferent response preceded the increase of over-all electromyographic activity of the whole triceps muscle but only by 10-100 msec. The discrepancy could be due to the soleus alpha motoneurones being activated earlier than the alpha-motoneurones of gastrocnemius muscle, according to the size principle. In only one experiment, the alpha-firing onset preceded the gamma-firing increase.8. Stimulations of ipsilateral or contralateral nerve, whatever the alpha or gamma reflex patterns, always led to increased firing rates of group I and II fibres of the small nerve. The origins of the discharge of group I and II muscle afferents and the excitation mechanisms of the receptors involved are considered. Some aspects of the mechanism of the reflex control of movement are discussed in the light of these results.

Modification by lidocaine of the discharges of primary endings of muscle spindles in cat tenuissimus muscle.

The effects of lidocaine (1--20 microgram/ml) on afferent discharge patterns of primary endings of muscle spindles in cat tenuissimus muscle were investigated. Discharge from the endings, recorded in Ia afferent axons, was evoked by ramp stretch of the muscle, stimulation of single static or dynamic fusimotor axons or by a combination of stretch and fusimotor stimulation. Spontaneous discharge of the endings at the initial length of the muscles was reduced by 2--5 microgram/ml and abolished by 10--15 microgram/ml lidocaine. The static but not the dynamic discharge elicited by muscle stretch was blocked by concentrations of 10--15 microgram/ml. The same concentrations abolished static and dynamic fusimotor influences on primary ending discharge. However, in one experiment where the spindle was microscopically observed, fusimotor stimulation still resulted in contraction of the intrafusal muscle even when fusimotor stimulation failed to elicit changes in discharge response patterns of the primary endings. These findings indicate that lidocaine interferes with the encoding mechanism prior to block of impulse conduction in either the fusimotor or afferent axons.

Histological analysis of cat muscle spindles following direct observation of the effects of stimulating dynamic and static motor axons.

1. Eleven cat tenuissimus spindles have been analysed mainly by cutting serial, transverse, 1 micrometer thick sections following direct observation of the effects of dynamic motor (gamma or beta) stimulation. 2. Histological results from these spindles were also used to interpret the effects of static fusimotor stimulation of other spindles. 3. Dynamic motor stimulation usually produced contractions seen as convergent movements of sarcomeres in single bag fibres, identified as bag1 fibres for reasons given in the text. 4. In one spindle a single dynamic axon produced a translational movement in one pole of a bag1 fibre and a convergent movement in each pole of a bag2 fibre, together with movements in other unidentified (presumably chain) fibres. Subsequent analysis showed that besides innervating both bag fibres the axon also supplied two chain fibres. 5. Contrary to expectation, motor endings on the bag1 fibres seldom occurred at the sites of convergent movement. Only two cases of coincidence occurred among sixteen foci and twenty-one motor endings; otherwise focus and nearest ending were separated by distances of 0.85--2.5 mm. 6. Most of the convergent movements of sarcomeres observed in bag1 fibres occurred in a region of the pole that is ultrastructurally distinct from the region where most of the motor endings were located. The possible relevance of this to the production of contractions in the bag1 fibre is discussed. 7. Convergent movement foci in bag2 fibres produced by the stimulation of static axons occurred largely within the same regions of the pole as the motor endings were located, though, whereas foci were observed in both intra- and extracapsular regions, most of the endings were intracapsular.

Identification of intrafusal muscle fibres activated by single fusimotor axons and injected with fluorescent dye in cat tenuissimus spindles.

1. Intrafusal muscle fibres of cat tenuissimus spindles have been injected with the fluorescent dye Procion Yellow and identified histologically after recording their changes in membrane potential during 1/sec stimulation of single static or dynamic gamma axons. 2. Thirteen intrafusal muscle fibres innervated by static gamma axons were identified as eight bag2 and five chain fibres. The fact that none proved to be a bag1 fibre is not regarded as significant, for reasons given in the Discussion. 3. In one spindle Procion Yellow was injected into two intrafusal muscle fibres activated by the same static gamma axon; they were identified as a bag2 and a chain fibre. 4. Nine intrafusal muscle fibres innervated by dynamic gamma axons were identified as seven bag1 fibres, one bag2 fibre, and one long chain fibre. 5. In one spindle two bag fibres were injected, one activated by a dynamic gamma axon, the other by a static gamma axon; the former proved to be a bag1 fibre, the latter a bag2 fibre. 6. Stimulation of static gamma axons elicited junctional potentials in seven bag2 fibres and one damaged chain fibre, and action potentials in one bag2 and four chain fibres. In the whole sample of impaled intrafusal muscle fibres (identified and unidentified) activated by static axons, junctional potentials were recorded from twenty-three (62.2%), and action potentials from fourteen (37.8%). Stimulation of dynamic gamma axons always elicited junctional potentials. 7. In a number of instances it was possible to examine the ultrastructure of motor endings belonging to the stimulated gamma axon. The myoneural junctions of trail endings supplied by static gamma axons to bag2 and chain fibres were both smooth and folded; the deepest and most regular folding occurred on chain fibres. The terminals of p2 plates supplied to bag1 fibres by dynamic gamma axons had smooth myoneural junctions.

Cinematographic analysis of contractile events produced in intrafusal muscle fibres by stimulation of static and dynamic fusimotor axons.

1. Muscle spindles with an intact blood supply and uninterrupted connexions with ventral and dorsal spinal roots (Bessou & Pagés, 1967, 1972) have been prepared in cat's tenuissimus muscles with the aim of cinephotographically recording intrafusal movements induced by the stimulation of single static or dynamic gamma axons; the time cours of these movements and the morphological kind of activated intrafusal muscle fibres have been established. 2. Displacements of spindle guiding marks in the equatorial region elicited by stimulating single static gamma axons are 4-20 times greater in amplitude than the ones elicited by stimulating dynamic gamma axons at the same frequency. 3. The dynamic gamma axons induced a contraction only in nuclear bag fibres which, in addition, never received any static gamma innervation. The static gamma axons evoked contractions either in nuclear bag fibres alone, or in nuclear chain fibres alone, or in both types of intrafusal fibres. Two thirds of static gamma axons supplied nuclear bag fibres. For various reasons, one half only of static gamma axons innervating nuclear bag fibres could be shown to simultaneously innervate nuclear chain fibres. Consequently, about one third of static gamma axons supplied both nuclear bag fibres and nuclear chain fibres, but it is highly probable that this latter figure is an underestimate. One third of static gamma axons produced contraction in nuclear chain fibres only. In this work, the distribution of fusimotor axons has been established in only one muscle spindle of the cluster of muscle spindles that each fusimotor axon is generally innervating. 4. Generally speaking, a static gamma axon elicits contraction of several intrafusal fibres whereas a dynamic gamma axon innervates only one intrafusal fibre and frequently only one pole of the fibre. 5. One third of static gamma axons evoked contractions in nuclear chain fibres that seemed to involve the whole pole. The other static gamma axons and all dynamic gamma axons produced, in the intrafusal fibres that they supplied, one or several foci of localized contractions. 6. The nuclear chain fibres contract and relax faster than nuclear bag fibres. The contractions of nuclear bag fibres supplied by static gamma axons are stronger and faster than those of nuclear bag fibres innervated by dynamic gamma axons. Nearly all nuclear bag fibres innervated by static gamma axons, like the nuclear chain fibres, show transient contractions at each pulse of a stimulation at low frequency (2-20/sec). 7. The results are discussed taking into account the available anatomical and physiological data on the muscle spindle. Their consequences with regard to intrafusal working are briefly considered.

Intracellular potentials from intrafusal muscle fibers evoked by stimulation of static and dynamic fusimotor axons in the cat.

1. Membrane potential changes of single intrafusal muscle fibres were intracellularly recorded in spindles of cat's tenuissimus muscle on stimulating single static or dynamic fusimotor axons.2. One third of responses elicited on stimulating static fusimotor axons were action potentials while the remainder were junction potentials. Repetitive stimulation of static axons eliciting junction potentials produced summation, facilitation and in some instances the appearance of propagated potentials.3. All the responses evoked on stimulating dynamic fusimotor axons were junction potentials which summated but never produced propagated potentials during repetitive stimulation.4. Most of the impalements leading to junction potentials were located in the transition zone between intra- and extra-capsular regions of spindle poles.5. The relation between extracellular and intracellular potentials elicited by stimulation of a fusimotor axon (static or dynamic) makes it possible to assign a physiological nature to the junction potentials recorded intracellularly and to exclude effects attributable to injury.6. A coupling between junction potential and local contraction is indirectly inferred from the frequencygrams which have been previously obtained during single shock stimulation of dynamic fusimotor axons.