A case of probable sporadic Creutzfeldt-Jacob Disease in a tertiary care hospital in Malaysia

The diagnosis of Creutzfeldt-Jakob disease (CJD) can be challenging as findings are non-specific and there is low awareness of the disease. We present a case of an 83-yearold man with a two months history of rapidly progressive dementia. After a series of extensive diagnostic examinations, he was diagnosed with probable sporadic CJD with key findings of rapidly progressive dementia, myoclonus, pyramidal signs, abnormal hyperintensity signals on diffusion-weighted magnetic resonance imaging (DW-MRI) and typical electroencephalograph (EEG). His symptoms progressively worsened and he died four months after the onset of symptoms.

Adjuncts to transcatheter aortic valve implantation

INTRODUCTION

The appreciable rise in percutaneous valve procedures has been pursued by a wave of development in advanced technology to help guide straightforward, streamlined and safe intervention. This review article aims to highlight the adjunctive devices, tools and techniques currently used in transcatheter aortic valve implantation procedures to avoid potential pitfalls. Areas covered: The software and devices featured here are at the forefront of technological advances, most of which are not yet in widespread use. These products have been discussed in national and international structural intervention conferences and the authors felt it important to showcase particularly well designed adjuncts that improve procedural efficacy and safety. Whilst vascular pre-closure systems are used routinely and are an integral part of these complex cardiovascular procedures, these have been well summarised elsewhere and are beyond the scope of this article. Expert commentary: The rising volume of patients with aortic stenosis who are treatable with TAVI means that this exponential increase in procedures must be accompanied by a steady decline in procedural complications. This section provides an overview of our current perspective, and what we feel the direction of travel will be.

G2677T polymorphism can predict treatment outcome of Malaysians with complex partial seizures being treated with Carbamazepine

Carbamazepine (CBZ) is used as the first line of treatment of complex partial seizures (CPS) in Malaysia. While this drug is known to be effective for the treatment of CPS, more than 30% of patients remain drug resistant to CBZ mono-therapy. We examined a possible relationship between patients' response to CBZ mono-therapy and the G2677T SNP of the ABCB1 gene. Three hundred and fourteen patients with CPS were recruited from the Neurology Department of the Kuala Lumpur Hospital, of whom 152 were responders and the other 162 were non-responders to CBZ mono-therapy. DNA was extracted from blood samples and real-time PCR was performed to detect the G2677T SNP of the ABCB1 gene. Results were described as genotype frequencies and compared by logistic regression analysis. Among the 152 responders, 74% had the GG genotype. However, among the 162 non-responders, 26.5% had the GT genotype and 39% had the TT genotype. There was a significant difference in genotype frequency (TT vs GG; odds ratio 4.70; 95% confidence interval, 2.70-8.20) between responders and non-responders. The presence of the T allele of the G2677T SNP appears to be a useful screening marker to determine if a patient is going to be resistant to CBZ as a single drug therapy in the treatment of CPS.

Radiofrequency ablation of cardiac arrhythmias: past, present and future

The treatment of cardiac arrhythmias has been revolutionized by the ability to definitively treat many patients with radiofrequency catheter ablation, rather than requiring lifelong medication. This review covers the history of how this has developed and the methods used currently and explores what the future holds for this rapidly evolving branch of Cardiology.

The predictors of subclinical cerebral infarcts in ischaemic stroke patients

Subclinical cerebral infarcts (SCI) have been increasingly shown to cause a significant clinical impact. However, there are limited data available on Asian patients. The objectives of this study were to determine the prevalence of SCI in ischaemic stroke patients seen in the Hospital Universiti Kebangsaan Malaysia (HUKM) and to identify its associated risk factors. We evaluated the brain computed tomography (CT) evidence of subclinical infarcts in ischaemic stroke patients. The patients were selected from those who were on regular follow up in the neurology clinic following an ischaemic stroke. The risk factors associated with subclinical infarct were documented. The brain CTs were done during acute admission and reviewed for SCI. Sixty-one patients were enrolled in this study. Twenty-two (36.1%) out of the 61 patients had SCI. The risk factors for SCI in our study were hypertension (OR 14.16 CI 2.04-97.89), diabetes mellitus (OR 12.48; CI 1.95-79.77) and leukoaraiosis (OR 28.39; CI 2.33-284.16). Subclinical cerebral infarcts were present in about one third of our ischaemic stroke patients. This finding is higher than in previous studies done on Caucasians. Hypertension, diabetes mellitus and leukoaraiosis independently predict SCI.

Reward encoding in the monkey anterior cingulate cortex

The anterior cingulate cortex (ACC) is known to play a crucial role in the fast adaptations of behavior based on immediate reward values. What is less certain is whether the ACC is also involved in long-term adaptations to situations with uncertain outcomes. To study this issue, we placed macaque monkeys in a probabilistic context in which the appropriate strategy to maximize reward was to identify the stimulus with the highest reward value (optimal stimulus). Only knowledge of the theoretical average reward value associated with this stimulus--referred to as 'the task value'--was available. Remarkably, in each trial, ACC pre-reward activity correlated with the task value. Importantly, this neuronal activity was observed prior to the discovery of the optimal stimulus. We hypothesize that the received rewards and the task value, constructed a priori through learning, are used to guide behavior and identify the optimal stimulus. We tested this hypothesis by muscimol deactivation of the ACC. As predicted, this inactivation impaired the search for the optimal stimulus. We propose that ACC participates in long-term adaptation of voluntary reward-based behaviors by encoding general task values and received rewards.

Characterization of serial order encoding in the monkey anterior cingulate sulcus

In a previous report we showed that neurons in the anterior cingulate cortex might encode the serial order of the three components (first, second and third) of motor sequences, irrespective of which component is performed, and irrespective of the component that precedes or follows. Here we further explore these data by comparing the magnitude of cell activity at the different ranks. We also compare the activity recorded in the motor sequences and in tasks with only one motor component. We finally discuss functional hypotheses, which may account for the serial order encoding.

The effects of sequence structure and reward schedule on serial reaction time learning in the monkey

This research tests the hypothesis that sequence learning performance in non-human primates will be modulated both by the structure of the sequences to be learned and by the schedule of reward applied during learning. Sequence learning in humans has been extensively explored with serial reaction time (SRT) protocols where learning is revealed by reduced reaction times for stimuli presented in repeating sequences vs. stimuli presented in random series. The SRT protocol has been used to demonstrate that different types of sequential structure may be learned under different awareness conditions. Here, we consider surface and abstract structure of sensorimotor sequences such that sequences ABCBAC and DEFEDF (where A to F correspond to spatial locations on a touch sensitive screen) have different serial order or surface structure, but share the same abstract structure 123213, and are thus considered isomorphic. In four experiments, we manipulated the type of sequential structure to be learned, and the schedule of reward in spatial sequence learning tasks. Both of the two monkeys tested demonstrated significant SRT learning for serial order or surface structure, while they failed to learn and transfer abstract structure. Their learning performance was also modulated by the schedule of reward. These results are in support of our hypothesis and are discussed in the context of existing models of sensorimotor sequence learning.

Anterior cingulate activity during routine and non-routine sequential behaviors in macaques

Anterior cingulate cortex is important in monitoring action for new challenges. We recorded neuron activity in the anterior cingulate sulcus of macaques while they performed a sequential problem-solving task. By trial and error, animals determined the correct sequence for touching three fixed spatial targets. After the sequence was repeated three times, we then changed the correct solution order, requiring a new search. Irrespective of component movements or their kinematics, task-related neurons encoded the serial order of the sequence. Neurons activated with sequence components (68%) differed in activity between search and repetition. Search-related activity occurred when behavioral flexibility was required and ended as soon as the animal accumulated enough information to infer the solution, but had not yet tested it. Repetition-related activity occurred in a regime of memory-based motor performance in which attention to action is less necessary.

Problem solving and logical reasoning in the macaque monkey

This study focuses on the performances of monkeys in a spatial problem-solving task that involves working memory. Two monkeys had to find, by trial-and-error, the touching order of 2 or 3 targets in a set of 3 or 4 fixed spatial targets. When a solution was found and performed 6 times, the order was changed and the animal had to resume a new search within the same set of targets. Thus, in a training session, many searches (up to 60) could be initialised. The data show that the animals conducted a methodical search for the hidden order and found the solution in a minimal number of trials. We conclude that the monkey is able to construct complex cognitive structures, similar to logical reasoning, to solve spatial problems of this type.

Activity in the caudate nucleus of monkey during spatial sequencing

1. There are indications that the execution of behavioral sequences involves the basal ganglia. In this study we examined the role of the caudate nucleus in the construction, storage, and execution of spatial plans. 2. Two monkeys (Macaca mulatta) were trained to perform sequences of saccades and arm movements. The animals had to remember the order of illumination, variable from one sequence to another, of three fixed spatial targets. After a delay, they had to visually orient toward, and press each target in the same order. Six different sequences were executed on the basis of the order of illumination of the targets. Single cell activity was recorded from the four caudate nuclei of the two monkeys. 3. Neural activity was analyzed in each sequence during 10 different periods: the instruction period in which the targets were illuminated, the three orientation periods toward the different targets, the three postsaccadic periods, and the three periods of target pressing. Statistical comparisons were made to detect differences between the different sequences with respect to activity in each period (sequence specificity). 4. A total of 2,100 neurons were studied, of which 387 were task related. The task-related cells were found in both the head and the body of the caudate nucleus. 5. During central fixation, anticipatory activity (n = 81) preceded onset of specific events. Four groups were considered: 1) neurons (n = 46) anticipating offset of the central fixation point, 2) neurons (n = 7) anticipating the illumination of any target, regardless of its spatial position or order of presentation (rank), 3) neurons (n = 17) anticipating the illumination of the first target, regardless of its spatial position, and 4) neurons (n = 11) anticipating the illumination of a given target, regardless of its rank. 6. Phasic visual responses to target onset were observed in 48 cells. The cells responded primarily to the contralateral and upper targets. In a majority (n = 35), visual responses were modulated by the rank of the target(s). Many cells (n = 20) responded only if the corresponding target was first; other cells responded only if the target was second or if it had complex time relationships with the other targets. 7. The responses of the cells to the same instruction stimuli repeated twice in a row, and under the condition that the animal did not behaviorally use the first instruction in between, were tested. More than one-third of the tested cells (n = 14) did not respond, or responded very weakly, to the second instruction.(ABSTRACT TRUNCATED AT 400 WORDS)

Neural activity in the caudate nucleus of monkeys during spatial sequencing

Single cell activity was recorded from the monkey caudate nucleus. The animal had to execute motor and oculomotor sequences based on memorized information. In each trial, the monkey had to remember the order of illumination of three fixed spatial targets. After a delay, the animal had to press the targets in the same sequence. The "task-related" cells were activated by onset of the targets and on execution of saccades or arm movements. In a majority of cells, activation did not depend only on the retinal position of the stimuli or on the spatial parameters of gaze and arm movements, but was contingent on the particular sequence in which the targets were illuminated or the movements were performed.

Perforation of the globe--a complication of peribulbar anaesthesia

Peribulbar anaesthesia has been recommended as a safer alternative to retrobulbar anaesthesia. We report a case of perforation of the globe sustained during peribulbar anaesthesia which resulted in blindness. Orbital injections are potentially dangerous, be they peribulbar or retrobulbar. To minimise the risk, short, blunt needles are advocated for the peribulbar route.

Prefrontal cortex and spatial sequencing in macaque monkey

1. Single neuron activity was recorded from the prefrontal cortex of two macaque monkeys during the performance of a task involving spatial sequencing. The monkeys faced a panel displaying a central fixation point and three fixed targets (two lateral and one above the point of fixation). In the first phase of each trial, the three targets were turned on in random order: in the second phase, the animal had to press each target, still lighted, in the order of their illumination. Thus, successful performance of the task depended strongly on temporal memory. The animals were fitted with DC-EOG electrodes. 2. Three hundred and two task-related neurons were recorded in the superior arcuate area and caudal part of sulcus principalis. Among the cells whose pattern of activity appeared to be related to the sequencing task, five classes were distinguished: Visual tonic (VT), fixation, context, saccade related and visual phasic cells. In addition, a small number of cells appeared to be related to other aspects of the behavior, but not to the sequencing task. Our present analysis concentrates on two groups of sequencing task-related cells (VT and context cells). 3. The VT cells (35/302-11.5%) were recorded exclusively from the superior arcuate area. All VT cells increased their firing rate (sustained activation) during fixation of the central fixation point (FP) following onset of one of the three targets used, specific for a given cell (directional or spatial selectivity). In one group of VT cells, a shift in the eye position towards the specific peripheral target resulted in the return of the cells' firing rate to the pre-trial level. In the other group of VT cells, reset of the firing rate to pre-trial level was not related to the onset of fixation of the peripheral target. Sustained activation of the VT cells depended also on the sequential order of illumination of the specific target (temporal selectivity). In twenty-four cells (68.5% of VT cells) sustained activation was observed when the target came first in the sequence. Onset of the target in the second or third rank elicited either no response or only a short lasting phasic activation. In the remaining eleven cells (31.5% of VT cells), sustained activation was only observed when the target came second in a given sequence. The firing of the VT cells was correlated with the animals' performance of the task.(ABSTRACT TRUNCATED AT 400 WORDS)

Taxol, cytochalasin B and colchicine effects on fibroblast migration and contraction: a role in glaucoma filtration surgery?

Migration and contraction are fibroblast activities in scar tissue formation which may contribute towards the failure of trabeculectomies. We attempted to modify the migration and contraction of Tenon's capsule fibroblasts in vitro using the drugs taxol, cytochalasin B and colchicine. Migration assays were conducted in 48-well micro-chemotaxis chambers, using rabbit aqueous humour which has been previously identified as a powerful chemoattractant for Tenon's fibroblasts, and fibronectin as the stimuli for migration. All three drugs inhibited the migration of fibroblasts to both fibronectin and aqueous humour, with maximal activity seen at 10(-6)M (taxol), 10(-5)M (cytochalasin B), and 10(-3) M (colchicine). In a single cell contractile assay in which contraction of whole fibroblasts was initiated with exogenous adenosine triphosphate (ATP), taxol and colchicine showed anticontractile activity, maximal at 10(-5)M and 10(-3)M respectively, but cytochalasin B was ineffective. The significance of the activities of these drugs in relation to their proposed use for improving the success of trabeculectomies is discussed.

Role of the dorsolateral prefrontal cortex in organizing visually guided behavior

Unit activity was recorded in the prefrontal cortex of rhesus monkeys during performance of a delayed task with two motor responses, a saccade and an arm movement, to a complex pattern of auditory and visual stimuli. The peculiarity of the paradigm was that onset of the different sensory stimuli, orienting saccade and arm movement, were dissociated in time and occurred at prefixed time intervals. Two hundred and sixteen task-related units were recorded. The data show that the dorsolateral part of the prefrontal cortex plays a crucial role in temporal organization of visually guided behaviour. This cortical area contains the neural substrate of an encoding strategy for remembered or current events and objects in the behavioural surround that are not, as yet, foveated. This encoding mechanism subserves a particular cognitive process. Whether events or objects are, or are not, encoded depends on their significance for future behaviour. While foveation deletes their neural trace, it activates a class of cells that appear involved in the preparation of arm movements towards the foveated region. The destruction of these two complementary mechanisms would disrupt the organism's capacity to integrate temporally and spatially discontinuous information for performance of goal-directed acts.

Chemotactic activity of aqueous humor. A cause of failure of trabeculectomies?

The chemoattractant activity for ocular fibroblasts of the aqueous humor of patients undergoing glaucoma surgery was evaluated in 48-well microchemotaxis chambers and compared with control specimens from patients undergoing cataract extractions. All specimens were chemoattractant, but those from patients who had previously undergone glaucoma surgery that had failed were of significantly greater activity than the controls'. This chemoattractant activity is primarily chemotactic. It consists of heat-stable and heat-labile components. The predisposition of a patient to sustain failed glaucoma drainage surgery may be related to the chemoattractant activity of his aqueous humor, since strongly chemoattractant aqueous humor may encourage fibrosis at the operation site.

Partial characterization of the fibroblast chemotactic constituents of human aqueous humour

This study demonstrates that aqueous humour derived from patients undergoing cataract extraction contains chemoattractants for ocular fibroblasts. The chemoattractant activity is independent of the surgical approach to obtaining the specimen as well as the surgeon operating. Studies in rabbits demonstrate that the chemoattractant activity is not artefactually produced by aqueous sampling and confirm the integrity of the blood-aqueous barrier. Substances responsible for this activity have molecular weights greater than 30,000; they are deactivated by low pH but retain activity at high pH. Identification of the chemoattractants in aqueous humour may allow pharmacological manipulation of would healing in relation to trabeculectomies.

The effect of retinoids on the migration of Tenon's capsule fibroblasts

The effect of the retinoids, retinol and all-trans acid, was assessed in vitro on the migration of rabbit Tenon's capsule fibroblasts, with a view to using these drugs as inhibitors of fibrosis in relation to trabeculectomies. No inhibition of fibroblast migration was demonstrated, and in fact retinol significantly enhanced both the random and directed migration of these cells (p less than 0.001 and p less than 0.01, respectively). This study emphasises the importance of using appropriate cells when investigating the effects of drugs on wound healing.

Wound healing as a barrier to successful filtration surgery

Trabeculectomy fails to control the intra-ocular pressure adequately in a proportion of patients. Approaches to solving this problem have involved modifications of surgery, histological studies of tissue from failed and functioning blebs, animal studies, and in vitro investigations of some of the basic processes of wound healing. This paper reviews the current state of investigations in these disciplines with particular reference to wound healing in this specialised site.

Normal rabbit aqueous humour, fibronectin, and fibroblast conditioned medium are chemoattractant to Tenon's capsule fibroblasts

Some of the chemotactic and chemokinetic properties of rabbit Tenon's fibroblasts were examined in a 48-well micro-chemotaxis chamber. Normal rabbit aqueous humour, fibronectin, and fibroblast conditioned medium were used in the assay, and all were shown to be chemoattractant. In addition, aqueous humour was shown to be powerfully chemotactic. Since the failure of human trabeculectomies is associated with migration of fibroblasts to the operation site, the study of the chemoattractant influences acting on these cells may allow manipulation of their behaviour in order to influence favourably the outcome of surgery.

Prefrontal unit activity during a delayed oculomotor task in the monkey

1. Unit activity was recorded in the prefrontal cortex of Rhesus monkeys during performance of a delay task with two motor components, an ocular saccade and an arm movement, following a complex pattern of auditory and visual stimuli. A special feature of the paradigm was that onsets of the different sensory stimuli, orienting saccade and arm movement were dissociated in time at predetermined time intervals. 216 task-related units were recorded. Discussion of the data focuses on two groups of cells the activity of which is modified by the saccade: the signal-related pre-saccadic tonic cells and the post-saccadic tonic cells. 2. Activity of signal-related pre-saccadic tonic cells was initiated with the onset of peripheral stimuli, visual and/or auditory, and terminated with an orienting saccade. Spatial selectivity was a feature of most units. They seemed to encode the region of space cued by the stimulus. 3. Many units were visually responsive. Activation of these depended both upon retinal locus of the stimulus and the requirement they imposed on subsequent behavior. Termination of their activity demanded foveation of some visual targets, not necessarily the one which had initiated their response. 4. The majority of these signal-related pre-saccadic tonic cells responded to onset of auditory stimuli. The termination of tonic activity in these cells with foveation of the region in space from which the signal originated suggests a spatial memory process that is no longer used when the visual fixation response can signal equivalent spatial information.(ABSTRACT TRUNCATED AT 250 WORDS)

Visuomotor properties of neurons of the anterior suprasylvian gyrus in the awake cat

Single cell activity was recorded from the Anterior Suprasylvian (ASS) gyrus of cats trained to orient their gaze toward visual or auditory stimuli. Sixty-five fixation cells were activated or suppressed as long as the animals were attentive to a particular region of space in the tangential or in the radial direction. Most of these fixation cells were neither light nor sound sensitive. Fifty-five cells were activated in relation to saccades. Fourteen neurons were active before and 41 after the onset of saccades. Nineteen neurons were also active with spontaneous eye movements in the dark. Fifteen neurons were seemingly related to vergence. They were not light-sensitive. They were preferentially activated by visual stimuli moving in the radial direction either towards or away from animal's face. Fifty light-sensitive neurons responded to moving stimuli. Only two neurons responded to onset of eccentric stationary light-stimuli. Fifty-one neurons showed a modulation in relation to vestibular stimulation. A majority showed, in addition, a vestibulo-collic response. These data suggest that the ASS gyrus in cats has a major role in the construction of the behavioral space.

Activity of neurons in the cat substantia nigra pars reticulata during drinking

Extracellular activity of single neurons in the pars reticulata of the Substantia Nigra (SNpr) was recorded in cats during drinking. Two groups of cells were distinguished: I. Somatosensory cells which responded by a short decrease in firing rate to the arrival of water against the upper lip. We suggest that these stimulus-related responses reflect a complex process linked to preparation of buccolingual movements. II. Action-related cells which were de-activated at the beginning or during the entire drinking period but without modulation in relation to the individual movements of jaws and tongue. We suggest that de-activation of these cells during drinking operates as a gating mechanism which allows implementation of complex motor sequences by cortical and/or subcortical structures.

The preparation of estradiol-17 beta sulfates with triethylamine-sulfur trioxide

Reaction of estradiol-17 beta with triethylamine-sulfur trioxide in pyridine gives exclusively monosulfation at the C17-hydroxyl group with the preparation of 17 beta-sulfooxyestra-1,3,5(10)-trien-3-ol triethylammonium salt (V). The structural assignment suggested by spectroscopic measurements was confirmed by synthetic studies. (Formula: see text) A synthesis of 3-sulfooxyestra-1,3,5(10)-trien-17 beta-ol triethylammonium salt (II) has been accomplished based on the preparation of 17 beta-formyloxyestra-1,3,5(10)-trien-3-ol (XIII). Fusion of the 3-sulfate triethylammonium salt II gives rise to the 17-sulfate triethylamine salt V. The preparation of estradiol-17 beta disulfate has also been achieved.

A fusion method for the preparation of steroid sulfates

A method for the preparation of steroid triethylammonium sulfates is outlined which involves the fusion of triethylamine-sulfur trioxide and steroids. Experimental details are presented which define the process as a thermal equilibrium resulting in the preferential sulfation of aliphatic hydroxyl groups. Sulfation of an aromatic hydroxyl group can be achieved in the absence of an aliphatic hydroxyl group. With excess reagent both types of hydroxyl groups in the same molecule can be sulfated.

Role of the cat substantia nigra pars reticulata in eye and head movements. I. Neural activity

Single unit activity was recorded in the Substantia Nigra pars reticulata (SNpr) of cats trained to orient their gaze toward visual and/or auditory targets. Cells in the SNpr have a steady high rate of spontaneous activity ranging from 35 to 120 spikes per second. The neurons respond to sensory stimuli or in relation to saccadic eye movements with a decrease or a cut-off of the spontaneous discharge. Among 109 cells recorded in the SNPR 60 were responsive to visual stimuli (mean latency = 118 ms). Most of the receptive fields which were plotted were large encompassing part of the ipsilateral field. Thirty nine (39) cells were responsive to auditory stimuli (mean latency = 81 ms). A majority of these cells showed a better response for stimuli located in the contralateral hemifield. In a few cells, the sensory responses were modulated by the subsequent orienting behavior of the animals. Thirty one (31) cells showed a response in relation to saccades. These units typically stopped discharging between 50 and 300 ms prior to the onset of the saccade. 39% of these units also responded in relation to spontaneous saccades in the dark. 61% of the saccadic cells also responded to sensory stimuli in the absence of saccades. Six (6) cells were found to respond to active head movements. These results are discussed in the framework of the role that the basal ganglia might have in the selection of the sensory stimuli that trigger orienting behaviors.

Role of the cat substantia nigra pars reticulata in eye and head movements. II. Effects of local pharmacological injections

Guided and reflex eye movements were studied in cats trained to make orienting saccades toward visual and auditory targets. Injections of a GABA-agonist (Muscimol) or GABA-antagonists (Bicuculline and Picrotoxin) were made in the Substantia Nigra pars reticulata (SNpr). Bicuculline and Picrotoxin, whether unilaterally or bilaterally injected had no effect on the posture nor the oculomotor performance of the animals. Neck muscle activity remained symmetrical. Unilateral injections of Muscimol produced oro-facial akinesia, reduction of the number of eye movements, contralateral head turning, visual neglect mostly (but not only) for ipsilateral visual space. Balance between the gains of the vestibulo-ocular reflex (VOR) in the two directions of movement was changed. Gain was decreased for the ipsilateral rotation. The optokinetic nystagmus (OKN) was not affected. Contralateral neck muscles were hypertonic. After bilateral injections of Muscimol, the cats did not orient. The VOR was normal when the injections induced no postural asymmetry. Hypertony was bilateral. Implications of these results for the role of the basal ganglia in motor control are discussed. We suggest that in Parkinson's disease the fixed inhibitory drive of the SNpr on the tectum and on the thalamus is disrupted.

Visual responses of thalamic neurons depending on the direction of gaze and the position of targets in space

Visual receptive field properties of neurons in the region of the thalamic internal medullary lamina were studied in alert cats while they fixated in various directions. In slightly more than 50% of the cells, the responsiveness of the cells was found to depend on the location of the stimulus with respect to the head-body axis (stimulus absolute position). A cell could ignore a stimulus outside its absolute field even if it was well placed within its receptive field. Three types of neurons were distinguished. Neurons with small central receptive fields were tonically activated when the animal fixated the stimulus in one half of the screen (usually contralateral). The firing rate of these cells was related to the stimulus absolute position measured along a preferred axis. Similarly, neurons with large receptive fields fired as a function of stimulus absolute position but stimulus fixation was not required. Neurons with eccentric fields responded to stimuli located in a target area defined in head-body coordinates. Such cells gave presaccadic bursts with eye movements terminating in the target area. The conclusion proposed is that neurons exist which code visual spatial information in a non-retinal frame of reference. This coding takes place at the time of stimulus presentation. Its role may be seen in the initiation of visually guided movements.

Sleep state and seizure foci related to depth spike activity in patients with temporal lobe epilepsy

Depth spike activity was evaluated from medial temporal lobe sites using computer spike recognition techniques in all-night sleep records derived from 10 patients with medically refractory complex partial seizures. Sleep stages were classified into 1 of 4 groups: wakefulness, REM sleep, light sleep and deep sleep. Some disturbance in the periodicity of the sleep cycle was noted in most patients, but the relative proportions of REM sleep, light sleep and deep sleep were close to that reported for normals. Depth spike activity was observed to be most frequent in a majority of sites during deep sleep in 6 patients and during light sleep in 3 patients. In 1 patient equal numbers of sites showed maximal activation during light sleep and deep sleep. In 4 patients, certain sites in the more epileptogenic lobe demonstrated a maximal rate during waking or REM sleep. All patients reported in this study were considered to be suitable for temporal lobectomy. In contrast to the results obtained from a previous study, the side with the site demonstrating maximal mean spike rate did not necessarily correspond to the side chosen for lobectomy. Significant correspondence across patients between the more epileptogenic lobe and maximal spike rate was not found during waking and was further reduced during light sleep and deep sleep. The correspondence was, however, significant during REM sleep and for the side containing the site demonstrating the smallest activation in mean spike rate during light sleep or deep sleep relative to waking. These results indicate that an analysis of sleep induced changes in depth spike activity can be useful in improving predictions concerning epileptogenicity. Quantification of other aspects of the interictal EEG, such as background activity, may further improve such predictions.

Computerized detection of rapid eye movements during paradoxical sleep

A technique for automatically analysing rapid eye movements in sleep EOG is described, in which time of occurrence, amplitude and duration of each REM are measured. This method is based on the pattern recognition algorithm that simulates visual analysis.

Modification of spontaneous ECoG and behavior in cat by monoamine precursors

The effects of increasing the brain monoamine content on the three types of localized rhythms identified in somatic area I ("mu-type rhythms") were studied in freely moving cats. Increases in brain monoamines (catecholamines and serotonin) were produced by injecting L-Dopa and 5-HTP, L-tyrosine, L-tryptophan and tryptamine were also tested. It is concluded that the two subsets of rhythms, one accompanying high levels of alertness and vigilance and the other appearing during quiet wakefulness, are related to the catecholaminergic systems, while those characterizing drowsiness seem to be controlled by a serotoninergic system. The latter, however, is distinct from that controlling slow sleep.

Effects of two neuroleptic drugs on focal somatoparietal rhythms in free awake cats

In freely moving cats, systemic administration of Chlorpromazine (CPZ) and Haloperidol (HP), two neuroleptics which presumably block catecholamine receptors, leads to a suppression of the waking mu-type rhythms. There is a clear difference, however, in that CPZ leads to slow wave sleep while HP only induces sustained drowsiness. The difference in their action is tentatively explained by their differential effect on an enzyme that is not involved in the metabolism of biogenic amines, tryptophan pyrrolase. We suggest that it is through this pathway that CPZ might increase and HP might decrease brain tryptophan and thereby lead to opposite changes in brain 5-HT content.

Modifications of the pattern-evoked potential (PEP) in relation to the stimulated part of the visual field (clues for the most probable origin of each component)

A spatio-temporal analysis of the successive and simultaneous components of the pattern-evoked potential recorded on the scalp, and of their modifications according to which part of the visual field is stimulated, was carried out with 20 'normal' subjects, in order to shed some light on their most probable sites of origin. The stimulus consisted in the onset of a 20 degree checkerboard presented in runs of 75 stimuli each. Its duration was 750 msec and its frequency of occurrence was random (about 1 every 1500 msec). Twelve different visual field situations were recorded: whole field, half fields and quadrants and stimuli limited to the fovea, to the macula and to extramacular areas. Data were collected from 9 active electrodes (in line, forming a cross montage), and various reference electrodes (ear lobes, Fz, non-cephalic). Eye movements were simultaneously recorded. The electrophysiological data were digitized on line and processed by computer in the form of averaged spatio-temporal maps. In addition to the classical posterior components which peak on the midline (N 60, N 140, and P 200) or less than 4 cm away on both sides (P 90), a late negative wave (LN 210) was differentiated which peaked lower than the inion and more than 8 cm away from the midline on both hemispheres. The large inter-individual variability of the spatio-temporal organization of these components under the same conditions, as well as its very good intra-individual reproducibility, were emphasized. Interpreted on the basis of a simple dipole sheet model of the visual cortex, the changes observed for each component in the 12 experimental situations led to the following suggestions: only the first component N 60 could reflect the activity of the part of area 17 emerging on the convexity, whereas P 90 (Jeffreys' CI) is more likely to originate in area 19 and the midline components N 140 and P 200 in area 18. The topography and reactivity of LN 210 could fit with the hypothesis that it reflects activity of the infero-temporal cortex.

[Temporal organization of paroxysmal discharges in the child. II. Polygraphic recordings during sleep]

A study of the paroxysmal activities in the course of all night sleep was carried out on 6 children aged 6 to 12 years, who were previously recored by means of biotelemtry during the day (cf. Findji et al. 1978). The discharges were analysed and quantified in the same way as in daytime but here in relation to the organization of sleep. The latter shows serious disturbances by comparison with normal children or children who only have sleep problems. The global quantifications (average densities of discharges per stage) do not, in our population, evidence any effect of facilitation or diminution which would be specific to a given stage. Comparison of the chronological evolutions of the densities of paroxysmal activities with the different stages of sleep shows that the connections between these phenomena can be either nil, or very close, according to the subject, and in one case, according to the time of night. This raises the problem of the heterogeneity of the 'states' gathered under the same codification of stages and shows the multiplicity of factors which can interfere with the modulation of the discharges, even during sleep. The analysis of long duration day or night records underlines the extreme complexity of the temporal organization of paroxysmal discharges, in which both hypotheses formulated at the beginning of this study seem to find partial support: internal modulation connected to more or less stable biological rhythms, and the role of environmental factors and the subject's reactions, which more or less mask the intrinsic rhythms.

[Temporal organization of paroxysmal discharges in the child. I. Biotelemetric recordings during wakefulness]

Based on telemetric recordings performed on 6 children, a study of the time distribution of intra-clinical paroxysmal discharges was carried out. It was tested whether this distribution is stochastic, and if not so, whether is depends upon an internal biological rhythm or upon environmental and behavioural factors. The times of occurrence of paroxysmal discharges, generalized and/or focal or partial, were located by visual inspection, and fed into a computer for statistical evaluation. Discharges and intervals were thus quantified for the overall recording time, for one situation or for groups of situations; the chronological distribution of discharges during successive 300 sec epochs was also computed. In all the cases, the discharge density varied from one moment to the next, but not in random fashion: the hypothesis of an internal modulation of the discharges was verified in some specific cases, more often, the changes in the discharge chronology seemed to be related to modifications of psychophysiological states observed during the successive experimental situations. The factors involved, namely, alertness, specific attention, stress, posture, etc., seemed to play a different role in each case; no simple correlation with the topography of discharges could be established. One explanation does not exclude the other: modulation of the discharges by biological rhythms could at any time be masked by variations due to environmental factors and to the subject's specific reaction to the latter. This type of study presents considerable methodological and interpretative difficulties which tend to emphasize individual differences rather than allowing to draw general laws.

Spatio-temporal organization of EEG in premature infants and full-term new-borns

Inter- and intrahemispheric EEG relationships were studied as a function of maturation in new-born infants. The spatio-temporal organization of EEG activity obtained during the two stages of sleep described in new-born infants - quiet sleep and active sleep - was analysed in 9 full-term new-born infants and 5 prematures (6 records). EEGs were recorded through transverse parietal montage made up of six bipolar derivations. Two epochs of 1.5 min each - successively obtained in both stages of sleep - were digitized, filtered in three frequency bands (beta, theta and delta) and computer-processed according to two methods, factor analysis and rhythms averaging. 1. The following EEG characteristics were found in both groups: (a) Instability of frequency within each frequency band (beta, theta and delta). However, theta activity was the most stable of the three, especially in quiet sleep. (b) Variability of topographical organization (i.e., localization of maxima of potentials) from one moment to another in both stages of sleep and in the three frequency bands. In spite of this intra-individual variability some sort of "average structure" was found in all infants; it was characterized by usually lateral and often symmetrical positions of the maxima of potential on the two hemispheres. For the same infant this structure was the same in the three frequency bands. (c) Poor interhemispheric relationships under all conditions, as well as poor interregional links in one hemisphere. 2. Some EEG characteristics differentiated the two groups and thus seemed to be related to maturation. Compared to full-term newborns the premature group showed: better stability for all three activities, especially for beta activity; higher frequency and larger amplitude of beta activity; better inter- and intrahemispheric relationships; fewer differences related to sleep stages. These results are discussed in terms of organization of the underlying cortical generators. The authors suggest that the active areas would increase in number and in surface with maturation, whereas the links between these different separate areas would remain very poor in the human full-term new-borns as well on one hemisphere as across hemispheres. This last finding would argue against the hypothesis that the corpus callosum which, as is well known, matures early, plays an important role in the establishment of interhemispheric links.