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S Rivaud-Péchoux

Publications and source records attributed to S Rivaud-Péchoux.

At least 19 recordsLinked to original sources
PubMed2006

Mixing pro- and antisaccades in patients with parkinsonian syndromes.

Prosaccades and antisaccades were investigated in three groups of patients with parkinsonian syndromes, Parkinson's disease, corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP), and in a control group. Saccade tasks were performed in single-task blocks (i.e. either blocks of prosaccades or blocks of antisaccades) and in mixed-task blocks (i.e. in blocks of randomly interleaved pro- and antisaccades). Saccade latencies and directional errors (misdirected saccades) were analysed in each subject, and we concentrated more specifically on the comparison of error rates in single tasks and in repeated trials of mixed tasks (i.e. mixing costs). The performance of each group in single tasks was largely consistent with previous studies, with normal antisaccade error rates in Parkinson's disease and CBD patients and increased antisaccade error rates in PSP patients. In contrast, a double dissociation was observed in mixed tasks. Parkinson's disease and CBD patients showed a marked increase in prosaccade and antisaccade error rates in repeated trials of mixed tasks, illustrated by increased mixing costs, whereas PSP patients showed similar error rates in single and repeated trials of mixed tasks, i.e. normal mixing costs. These results demonstrate that: (i) antisaccade performances may be differentially affected in mixed tasks and single tasks; (ii) the region of the dorsolateral prefrontal cortex which is crucial for reflexive saccade inhibition does not seem to be involved in the additional processes required in mixed-task conditions; (iii) the study of interleaved pro- and antisaccades may increase the accuracy of the differential diagnosis between these parkinsonian syndromes.

Aged↗
PubMed2006

Reproduction of self-rotation duration.

The vestibular system detects the velocity of the head even in complete darkness, and thus contributes to spatial orientation. However, during vestibular estimation of linear passive self-motion distance in darkness, healthy human subjects mainly rely on time, and they replicate also stimulus duration when required to reproduce previous self-rotation. We then made the hypothesis that the perception of vestibular-sensed motion duration is embedded within encoding of motion kinetics. The ability to estimate time during passive self-motion in darkness was examined with a self-rotation reproduction paradigm. Subjects were required to replicate through self-driven transport the plateau velocity (30, 60 and 90 degrees /s) and duration (2, 3 and 4s) of the previously imposed whole-body rotation (trapezoid velocity profile) in complete darkness; the rotating chair position was recorded (500 Hz) during the whole trials. The results showed that the peak velocity, but not duration, of the plateau phase of the imposed rotation was accurately reproduced. Suspecting that the velocity instruction had impaired the duration reproduction, we added a control experiment requiring subjects to reproduce two successive identical rotations separated by a momentary motion interruption (MMI). The MMI was of identical duration to the previous plateau phase. MMI duration was fidelitously reproduced whereas that of the plateau phase was hypometric (i.e. lesser reproduced duration than plateau) suggesting that subjective time is shorter during vestibular stimulation. Furthermore, the accurate reproduction of the whole motion duration, that was not required, indicates an automatic process and confirms that vestibular duration perception is embedded within motion kinetics.

Adult↗
PubMed2006

[Autosomal recessive cerebellar ataxias with oculomotor apraxia].

INTRODUCTION: Autosomal recessive cerebellar ataxias (ARCA) comprise a phenotypically and genetically heterogeneous group of diseases. Recently, a subgroup of ARCA associated with oculomotor apraxia has been delineated. STATE OF THE ART: The ataxias with oculomotor apraxia (AOA) include four distinct genetic entities at least: ataxia-telangiectasia, ataxia telangiectasia-like disorder, ataxia with oculomotor apraxia type 1 (AOA1) and type 2 (AOA2). The responsible genes, ATM, MRE11, APTX and SETX respectively, are implicated in DNA-break repair mechanisms. CONCLUSION: We describe the phenotypic and genetic characteristics of these ataxias, based on a review of the literature and a personal study of AOA1 and AOA2 patients.

Apraxias↗
PubMed2005

Upbeat nystagmus due to a small pontine lesion: evidence for the existence of a crossing ventral tegmental tract.

We report a patient with an isolated large upbeat nystagmus (UBN) in the primary position of gaze. Eye movements were filmed and recorded using electro-oculography. The upward vestibulo-ocular reflex gain, evaluated by pitching the head forward, was markedly reduced compared to when pitching the head back. The lesion was a probable lacunar infarction located in the paramedian and posterior part of the basis pontis, at the upper pons level. This UBN case, with one of the smallest brainstem lesions reported so far, supports the existence in humans of the crossing ventral tegmental tract, described in the cat and transmitting excitatory upward vestibular signals to the third nerve nucleus. It is also suggested that the decussation of this tract lies at the same upper pons level as in the cat but in a slightly more ventral location, i.e. in the posterior basis pontis.

Brain Injuries↗
PubMed2005

Saccade impairments in patients with fronto-temporal dementia.

BACKGROUND: Early diagnosis of fronto-temporal dementia (FTD) is often difficult because of the non-specific presentation. Saccadic eye movements, which are mainly controlled by the frontal areas, may provide a powerful tool for the analysis of frontal lobe dysfunction. The pattern of saccadic abnormalities has not previously been investigated in patients with FTD. OBJECTIVE: To study saccade tasks in a group of 23 patients with FTD and compare the results with aged matched healthy controls. METHODS: Triggering and inhibition of reflexive prosaccades were evaluated in a prosaccade and an antisaccade task, respectively, while the ability to withhold an antisaccade during a delay was explored in a delayed antisaccade task. Patients with progressive supranuclear palsy (PSP), in whom the pattern of eye movement deficit is well documented, were studied with the same protocol. To characterise the frontal lobe dysfunction in FTD more precisely, a battery of neuropsychological tests was carried out in these patients. RESULTS: Patients with FTD showed impaired reflexive saccade inhibition, similar to that observed in patients with PSP, and a decreased ability to withhold an antisaccade. CONCLUSIONS: Inhibition of reflexive and voluntary saccades appears to be independently processed. A delayed antisaccade task could be useful for the early diagnosis of FTD.

Aged↗
PubMed2004

Neural substrate of antisaccades: role of subcortical structures.

BACKGROUND: Experimental and clinical studies suggest that the dorsolateral prefrontal cortex (DLPFC) and the superior colliculus (SC) are crucial for the cancellation of reflexive eye movements toward distracting stimuli. However, the contribution of subcortical structures remains unknown. The basal ganglia provide serial tonic inhibitory connections between the DLPFC and the SC, and could therefore be involved in preventing the triggering of unnecessary saccades. The DLPFC could also exert its inhibitory effect on the SC through direct prefronto-tectal pathways that travel in the internal capsule (IC). Since thalamic dysfunction may be responsible for reduced DLPFC activation, it may be hypothesized that the thalamus could also participate in saccadic inhibition. METHODS: The authors recorded reflexive saccade triggering (prosaccade task) and inhibition (antisaccade task) in 29 patients with a single lesion affecting the striatum, the thalamus, or the IC, and compared these results to control subjects. RESULTS: A normal error rate in the antisaccade task was found in patients with 1) a basal ganglia lesion, 2) a thalamic lesion, or 3) a lesion restricted to the posterior half of the posterior limb of the IC. An increased error rate in the antisaccade task was found in patients with a lesion affecting the anterior limb, the genu, or the anterior half of the posterior limb of the IC. CONCLUSION: These results suggest that neither the basal ganglia nor the thalamus plays a major role in reflexive saccade suppression, but support the hypothesis of a direct DLPFC inhibitory control of saccade triggering on the SC.

Adult↗
PubMed2003

Antisaccade deficit after anterior cingulate cortex resection.

Suppression of unwanted reflexive saccades is a crucial process allowing to sustain voluntary fixation, when required. This inhibition process, which is mainly controlled by the dorsolateral prefrontal cortex, may also involve other cortical and subcortical structures. We prospectively studied the effect of frontal cortical resections involving adjacent regions to the anterior cingulate cortex on the ability to inhibit reflexive saccades. This lesion study included six patients undergoing resection of frontal low grade gliomas, studied prior and after surgery with electro-oculography, using the antisaccade paradigm. Lesions were normalized and mapped in Talairach space allowing to detail the structures whose lesions were associated with antisaccade deficits. In three of the six patients significant early post-operative antisaccade errors were associated with resection of a common critical region, mainly involving the posterior part of the anterior cingulate cortex. This same region was spared in the three remaining patients with no antisaccade deficit, suggesting that the anterior cingulate cortex, known as the cingulate eye field, could play a role in suppression of unwanted saccades.

Adult↗
PubMed2003

Cortical control of ocular saccades in humans: a model for motricity.

Our knowledge of the cortical control of saccadic eye movements (saccades) in humans has recently progressed mainly thanks to lesion and transcranial magnetic stimulation (TMS) studies, but also to functional imaging. It is now well-known that the frontal eye field is involved in the triggering of intentional saccades, the parietal eye field in that of reflexive saccades, the supplementary eye field (SEF) in the initiation of motor programs comprising saccades, the pre-SEF in learning of these programs, and the dorsolateral prefrontal cortex (DLPFC) in saccade inhibition, prediction and spatial working memory. Saccades may also be used as a convenient model of motricity to study general cognitive processes preparing movements, such as attention, spatial memory and motivation. Visuo-spatial attention appears to be controlled by a bilateral parieto-frontal network comprising different parts of the posterior parietal cortex and the frontal areas involved in saccade control, suggesting that visual attentional shifts and saccades are closely linked. Recently, our understanding of the cortical control of spatial memory has noticeably progressed by using the simple visuo-oculomotor model represented by the memory-guided saccade paradigm, in which a single saccade is made to the remembered position of a unique visual item presented a while before. TMS studies have determined that, after a brief stage of spatial integration in the posterior parietal cortex (inferior to 300 ms), short-term spatial memory (i.e. up to 15-20 s) is controlled by the DLPFC. Behavioral and lesion studies have shown that medium-term spatial memory (between 15-20 s and a few minutes) is specifically controlled by the parahippocampal cortex, before long-term memorization (i.e. after a few minutes) in the hippocampal formation. Lastly, it has been shown that the posterior part of the anterior cingulate cortex, called the cingulate eye field, is involved in motivation and the preparation of all intentional saccades, but not in reflexive saccades. These different but complementary study methods used in humans have thus contributed to a better understanding of both eye movement physiology and general cognitive processes preparing motricity as whole.

Cerebral Cortex↗
PubMed2003

The parieto-collicular pathway: anatomical location and contribution to saccade generation.

The monkey lateral intraparietal area (LIP), involved in reflexive shifts of visual attention, has two main oculomotor outputs: towards frontal oculomotor areas and towards the superior colliculus. Recent studies suggest that these two outputs do not carry similar information. Direct LIP-collicular neurons would convey visual signals providing the oculomotor system with on-line visuo-spatial information. Parietal visuo-spatial information regarding internal stimuli would access the brainstem oculomotor circuitry through a parieto-frontal network. Consequently, an interruption of parieto-tectal neurons should affect reflexive saccades towards unpredictable targets and have little or no effect on saccades towards predictable or memorised stimuli. In order to test this hypothesis in humans, we have determined in rhesus monkeys the location of LIP-tectal fibres in the region of the internal capsule, and found that these neurons travel in the most posterior region of the posterior limb of the internal capsule. We have then tested, in seven patients with a small lesion involving this region, several oculomotor paradigms designed to determine the influence of spatial predictability on saccade accuracy and the ability to withhold reflexive saccades. In all patients, saccade accuracy was affected in unpredictable conditions but was normal when target location could be predicted or memorised. Reflexive saccade inhibition was affected only in the three patients in whom the capsular lesion had the most anterior extent. These results therefore support in humans the hypothesis that parieto-tectal neurons (i) transmit an on-line signal that is used by the oculomotor system for reflexive saccade triggering, (ii) are not crucial for the computation of internally guided saccades and (iii) are not crucial for reflexive saccade inhibition.

Adult↗
PubMed2003

[Contribution of oculomotor examination for the etiological diagnosis of parkinsonian syndromes].

Exploration of ocular motricity can be helpful for diagnosis in certain parkinsonian syndromes. Oculomotricity is perturbed in Parkinson's disease (PD) and in multiple system atrophy (MSA). The minimal anomalies, sometimes observed in these conditions, both clinically and on oculomotor recordings, cannot contribute significantly to diagnosis. In corticobasal degeneration (CBD), infraclinical oculomotor anomalies can be identified on oculomotor recordings and are relatively specific to atypical parkinsonian syndrome: particularly long latency of ocular saccades related to posterior parietal involvement. The most significant contribution is observed for progressive supanuclear palsy (PSP) where the oculomotor anomalies are evident at clinical examination and are even the cardinal signs of the condition: particularly paralysis of vertical ocular saccades (downbeat and upbeat) or downbeat saccades, ocular pursuit also being perturbed but not reflex movements (preservation of oculocephalic reflexes). This dissociation between palsy of saccade and pursuit movements and preservation of oculocephalic reflexes is the sign of the supranuclear origin of the oculomotor disorder in PSP. In early stage PSP before clinical expression, requiring oculomotor recordings to be recognized, it is relatively specific in the context of degenerative parkinsonian degeneration. PSP also involves other less specific anomalies such as a perturbation of the antisaccade movements (related to a frontal syndrome), anomalous ocular pursuit (becoming saccadic) and presence of square wave. A rigorous clinical examination of oculomotor function at a more advanced stage of PSP, or oculomotor recordings at an early stage of PSP or CBD, can thus contribute significantly to the diagnosis of both conditions.

Basal Ganglia↗
PubMed2001

Effects of transcranial magnetic stimulation of the posterior parietal cortex on saccades and vergence.

Previous studies showed that transcranial magnetic stimulation (TMS) of the posterior parietal cortex (PPC) prolongs the latency of intentional saccades. We examined whether a similar effect exists for reflexive saccades and vergence. To elicit reflexive movements, a gap paradigm was used; lateral saccades and vergence along the median plane were interleaved. TMS was applied on the right PPC 80 ms after target onset. Blocks without TMS were performed and a control experiment with TMS over the primary motor cortex. The latter had no effect on the latency of any type of movements. In contrast, stimulation of the PPC increased the latency of both saccades and vergence, suggesting that the PPC is involved in the triggering of reflexive movements both in direction and in depth.

Adult↗
PubMed2001

Involvement of the cerebellar thalamus in human saccade adaptation.

Saccade adaptation can be experimentally induced by systematically displacing a visual cue during a targeting saccade. Non-human primate studies have highlighted the crucial role of the cerebellum for saccade adaptation, but its neural substrates in humans are poorly understood. Recent physiological experiments suggest that, in addition to cerebellar structures, cortical areas may be involved as well. We have therefore hypothesized that saccade adaptation may rely on a cerebello-cerebral network, in which the cerebellar thalamus may link cerebellar and cerebral structures. To test this hypothesis, we studied saccade adaptation in a group of four patients with a thalamic lesion, with (n = 2) or without (n = 2) involvement of the cerebellar thalamus. Compared to healthy subjects, saccade adaptation was reduced in patients with associated cerebellar syndrome, but normal in patients without cerebellar syndrome. These results are consistent with the hypothesis that cerebello-thalamic pathways contribute to saccade adaptation in humans and suggest that the thalamus relays adaptation-related information from the cerebellum to cerebral cortical oculomotor areas.

Adaptation, Physiological↗
PubMed2001

Behavioural relevance modulates access to spatial working memory in humans.

Neurophysiological studies in monkeys suggest selective representation of behaviourally relevant information in working memory. So far, no behavioural evidence for this has been reported for humans. Here, we investigated the role of behavioural relevance for access to human visuospatial working memory by using delayed oculomotor response tasks. Subjects were presented two successive visual cues in different and unpredictable locations while fixating on a central fixation point. After a delay, an unpredictable auditory signal (one beep or two beeps) sounded and the central fixation point was turned off, initiating the oculomotor response (i.e. memory-guided saccade) phase. Two groups of 10 subjects each were studied in two conditions: in the 'relevant' condition, subjects were instructed to memorize both visual cues and to move the eyes to the remembered position of the first cue (one beep) or the second cue (two beeps). The same stimuli were used in the 'irrelevant' condition, but subjects were instructed to memorize and move the eyes to the position of the first cue only, regardless of the second cue and the auditory signal. In the 'relevant' condition, we found a significant increase in errors of memory-guided saccades to the first cue, when the second cue was located between central fixation point and first cue. This spatially selective interference effect disappeared in the 'irrelevant' condition, despite identical stimuli. On a behavioural level, these results show for the first time the significance of behavioural relevance for access to human spatial working memory. These findings complement recent single-neuron studies in monkeys, showing that the neuronal substrates of working memory selectively represent behaviourally relevant perceptual information.

Adult↗
PubMed2000

Longitudinal ocular motor study in corticobasal degeneration and progressive supranuclear palsy.

OBJECTIVE: To evaluate the usefulness of ocular motor information in the early diagnosis of corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). METHODS: Seven PSP patients, six CBD patients, and three atypical CBD patients were followed longitudinally with repeated electrooculographic (EOG) recordings, at 6-month intervals, to search for features that could confirm or modify the diagnosis. Visually guided saccades and antisaccades were studied. Data from clinical evaluations were independently collected. RESULTS: PSP patients had decreased saccade velocity throughout the disease course. Patients with probable CBD showed preserved saccade velocity but important increased saccade latency ipsilateral to the apraxia side. Similar to patients with PSP, those with atypical CBD features exhibited clinically evident abnormalities of vertical saccades and early slowing of horizontal saccade velocity, but no increase in saccade latency or early square-wave jerks. When clinical "telltale signs" appeared and the clinical diagnosis was reviewed independent of EOG recording, the three patients with atypical CBD features were diagnosed as having PSP although new or overlapping syndromes cannot be excluded. CONCLUSIONS: Consecutive EOG recordings help diagnose atypical CBD and PSP disorders earlier.

Aged↗
PubMed2000

Lesions affecting the parahippocampal cortex yield spatial memory deficits in humans.

Anatomical studies in monkeys, and functional imaging and lesion studies in humans, suggest that, within the primate medial temporal neocortex, the parahippocampal cortex (PHC) is particularly involved in spatial tasks. However, evidence for a functional specialization of the PHC regarding its spatial memory functions has so far been lacking. Here, we investigated spatial memory functions of the human perirhinal cortex (PRC) and PHC. Patients with lesions affecting the PRC but sparing the PHC, and patients with lesions affecting both PRC and PHC, performed an oculomotor delayed response task with unpredictably varied memory delays of up to 30 s. Compared to controls, patients with PRC+PHC lesions showed a significant delay-dependent inaccuracy of memory-guided eye movements contralateral to the lesion side, whereas patients with PRC lesions showed no significant inaccuracy. Our results show that the PHC is a critical component for spatial memory in humans and suggest that (i) extrahippocampal spatial memory functions of the medial temporal lobe may not be equally distributed in the medial temporal neocortex, but may be largely confined to the PHC, and (ii) damage to connections between cortices involved in spatial cognition and rostral regions of the temporal lobe is unlikely to account for the observed spatial memory deficits with PHC lesions.

Adult↗
PubMed2000

Improvement of memory guided saccades in parkinsonian patients by high frequency subthalamic nucleus stimulation.

Recent studies in the monkey suggest that the subthalamic nucleus (STN) is involved in control of eye movement, yet its functional significance in humans is unknown. Saccadic eye movements were studied in eight parkinsonian patients treated by bilateral electrical stimulation of the STN. STN stimulation improved the accuracy of memory guided saccades but not of reflexive visually guided saccades and had no effect on the antisaccade task. This study shows that, by contrast with levodopa, STN stimulation improves memory guided saccade deficits, and illustrates for the first time in humans the role of the STN in the control of purposive saccades.

Electric Stimulation Therapy↗
PubMed2000

A common mechanism for the control of eye and head movements in humans.

How the human brain controls the subtle coupling between eye and head movements is still debated. The brain could either coordinate two separate (eye and head) networks or use a single system involved in gaze (eye + head) control. In a recent report, a total transfer from eye to head movements was observed in a patient with congenital ophthalmoplegia. This led the authors to hypothesize that such transfer resulted from a long-term adaptation between oculomotor and head movement systems. We report on a patient in whom a similar transfer was observed but at the acute stage of an acquired ophthalmoplegia. This case demonstrates that the transfer between head and eye movements does not necessarily require long-term adaptation and supports the hypothesis of a common unique gaze motor command in which eye and head movements would be rapidly exchangeable.

Adult↗