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Biomedical subjects

C Marescaux

Publications and source records attributed to C Marescaux.

At least 55 records · Page 3Linked to original sources

Role of nitric oxide in pentylenetetrazol-induced seizures: age-dependent effects in the immature rat.

PURPOSE: Seizure susceptibility and consequences are highly age dependent. To understand the pathophysiologic mechanisms involved in seizures and their consequences during development, we investigated the role of nitric oxide (NO) in severe pentylenetetrazol (PTZ)-induced seizures in immature rats. METHODS: Four cortical electrodes were implanted in 10-day-old (P10) and 21-day-old (P21) rats, and seizures were induced on the following day by repetitive injections of subconvulsive doses of PTZ. The effects of NG-nitro-l-arginine methyl ester (l-NAME; 10 mg/kg) and 7-nitroindazole (7NI; 40 mg/kg), two NO synthase (NOS) inhibitors, and l-arginine (l-arg; 300 mg/kg), the NOS substrate, were evaluated regarding the mean PTZ dose, seizure type and duration, and mortality rate. RESULTS: At P10, the postseizure mortality rate increased from 18-29% for the rats receiving PTZ only to 100% and 89% for the rats receiving l-NAME and 7NI, respectively; whereas l-arg had no effect. Conversely, at P21, NOS inhibitors did not affect the 82-89% mortality rate induced by PTZ alone, whereas l-arg decreased the mortality rate to 29%. In addition, all NO-related drugs increased the duration of ictal activity at P10, whereas at P21, l-arg and l-NAME affected the first seizure type, producing clonic seizures with l-arg and tonic seizures with l-NAME. CONCLUSIONS: The relative natural protection of very immature rats (P10) against PTZ-induced deaths could be linked to a high availability of l-arg and, hence, endogenous NO. At P21, the modulation of seizure type by NO-related compounds may be related to the maturation of the brain circuitry, in particular the forebrain, which is involved in the expression of clonic seizures.

Age Factors↗

Magnetic resonance imaging follow-up of progressive hippocampal changes in a mouse model of mesial temporal lobe epilepsy.

PURPOSE: Hippocampal sclerosis (HS) is the most frequent lesion found in mesial temporal lobe epilepsy (mTLE). MR imaging is considered to be the most sensitive and specific method to detect HS. Despite extensive studies performed on humans and except in a recent study, the morphologic pattern of HS is usually analyzed when the disease has already fully developed, thus not allowing any insight into the mapping of the progressive morphologic changes inducing the development of mTLE. We have recently characterized a model of mTLE that reproduces the unilateral pattern of HS, induced by intrahippocampal injection of low doses of kainate (KA) in mice. METHODS: In this study, we monitored the temporal evolution of the development of HS in this model of mTLE by using T2-weighted sequence, T2-relaxation time measurements, and T1-weighted spin-echo technique after injection of gadolinium, from 1 h to 120 days after KA injection. RESULTS: HS induced by intrahippocampal KA injection occurred in two phases. First, we observed a transient hyperintense T2-weighted signal in the cortex above the injected hippocampus, most likely indicative of vasogenic edema partly due to the neurotoxic effect of KA. The concomitant increase in the T2 signal in the injected hippocampus and ipsilateral amygdala likely reflects the phase of cytotoxic edema occurring probably in relation to the excitotoxic consequences of both KA and seizure activity. Second, from 15 days on, a persistent unilateral increased T2 signal was detected in the hippocampus, which most probably reflects gliosis. CONCLUSIONS: Our findings indicate that longitudinal follow-up would permit a better understanding of the mechanisms underlying the constitution of HS in humans and eventually development of prevention strategies.

Animals↗

A metabolic and neuropathological approach to the understanding of plastic changes that occur in the immature and adult rat brain during lithium-pilocarpine-induced epileptogenesis.

PURPOSE: The age-related functional changes that underlie epileptogenesis remain to be clarified. In the present study, we explored the correlation between metabolic changes, neuronal damage, and epileptogenesis during the silent and chronic phases after status epilepticus (SE) induced by lithium-pilocarpine in 10-day-old (P10), 21-day-old (P21), and adult rats. METHODS: Local cerebral metabolic rates for glucose (LCMRglcs) were measured by the [14C]2-deoxyglucose method during the silent period (14 and 60 days after SE in P10 and P21 rats and only at 14 days after SE in adult rats because the silent phase lasts for about 14 days in adults and 60 days in P21 rats) and the interictal phase of the chronic period (2 months after spontaneous seizures or 6 to 7 months after SE in P10 and P21 rats that do not become epileptic). Neurodegeneration was assessed by the silver staining and cresyl violet techniques. RESULTS: In P10 rats, there was no damage and no metabolic consequences at any time after SE. During the silent phase in P21 rats, metabolic decreases were recorded at 14 days after SE, mainly in damaged forebrain regions. At 60 days after SE, P21 rats exhibited metabolic increases in both damaged forebrain and intact brainstem areas. In adult rats studied at 14 days after SE, LCMRglcs decreased in damaged forebrain areas involved in the genesis and propagation of seizures and increased in brainstem areas involved in the remote control of epilepsy. During the interictal phase of the chronic period, LCMRglcs decreased in damaged forebrain areas of adult epileptic rats and P21 rats that were not spontaneously epileptic, whereas it was similar to control levels in epileptic P21 rats. CONCLUSIONS: The process of epileptogenesis and its effects differ in duration and functional consequences in P21 and adult rats. The factors that underlie these age-related differences remain to be explored.

Age Factors↗

Endogenous control of hippocampal epileptogenesis: a molecular cascade involving brain-derived neurotrophic factor and neuropeptide Y.

PURPOSE: Seizures increase the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. Because this neurotrophin exerts modulatory effects on hippocampal neuronal excitability, it may play an important role in epileptogenesis initiated in this structure. Moreover BDNF is known to regulate the expression of neuropeptide Y (NPY), which displays modulatory properties on seizure activity. This suggests that the effects of BDNF on epileptogenesis may be mediated by NPY. METHODS: Adult male rats received a 7-day chronic intrahippocampal infusion of BDNF, BDNF antisense oligodeoxynucleotides, NPY, or anti-NPY immunoglobulin G during kindling of the hippocampus. The long-term regulation of NPY expression by BDNF was also studied by immunohistochemistry and radioimmunoassay. RESULTS: BDNF applied during the first week of hippocampal stimulation significantly delayed the progression of kindling, an effect that outlasted the end of the infusion by at least 7 days. Conversely, infusion of BDNF antisense oligodeoxynucleotides to reduce the expression of endogenous BDNF in the hippocampus aggravated the electroencephalographic expression of seizures. Chronic infusion of BDNF increased the expression of NPY in the hippocampus, with a time course similar to that of the protective effect of the neurotrophin on kindling. Finally, chronic infusion of NPY in the hippocampus delayed the progression of hippocampal kindling, whereas anti-NPY antibodies had an aggravating effect. CONCLUSIONS: Our results suggest that the seizure-induced increase in BDNF expression in the hippocampus may constitute an endogenous protective mechanism able to counteract hippocampal epileptogenesis. This protective effect appears to be mediated at least in part through the regulation of NPY expression.

Animals↗

Isotope tracer-techniques in rolandic epilepsy and its variants.

For ethical and practical reasons there are few studies on brain metabolism in rolandic epilepsy and it's variants. Most studies are performed in Landau-Kleffner syndrome or epilepsy with continuous spikes and waves during slow wave sleep (CSWS) which are considered to be included within the spectrum of rolandic epilepsy. The results of studies using isotope tracer-techniques in rolandic epilepsy and its variants are summarized.

Brain↗

Repetitive electroconvulsive seizures induce activity of c-Jun N-terminal kinase and compartment-specific desensitization of c-Jun phosphorylation in the rat brain.

Electroconvulsive seizures (ECS) are used for therapy of pharmacoresistent depression and are supposed to induce long-lasting neuronal alterations in morphology and gene expression. In this study, we have investigated the phosphorylation of the transcription factor protein c-Jun at its serine 73 residue by immunohistochemistry and the activity of the c-Jun N-terminal kinase 1 (JNK1) by immunocomplex assay following repetitive ECS in adult rats. In untreated controls, nuclear c-Jun immunoreactivity, but not N-terminal phosphorylation, was present in a variety of neuronal populations including the hippocampus, the temporobasal cortex and the amygdalar complex. Daily ECS for 1, 5 or 10 days (1x, 5x or 10x ECS) did not alter the expression of c-Jun but caused a substantial N-terminal phosphorylation of c-Jun (phospho-c-Jun). Nuclear phospho-c-Jun immunoreactivity was maximal within 15 min following ECS, and became absent after 30 min. The highest levels of phospho-c-Jun labeling were found after 1x ECS in the amygdalar complex, the dorsomedial hypothalamus and the piriform cortex. The inducibility of c-Jun N-terminal phosphorylation was preserved in the medial amygdala and piriform cortex, but significantly declined in the basal amygdala and medial hypothalamus with progressive ECS stimulation. One single ECS 3 or 5 days following 10x ECS yielded a pattern of phospho-c-Jun as seen following 10x ECS; thus, a lag of 5 days was not sufficient to provoke the initial level of N-terminal phosphorylation of c-Jun. In the rostral hippocampus, c-Jun was not phosphorylated at any investigated time inspite of its high constitutive expression. In some contrast with this compartment-specific phosphorylation of c-Jun, immunocomplex assays revealed that the JNK1 activity was strongly enhanced in both amygdala and hippocampus. Our findings demonstrate that rapid JNK activation and phosphorylation of c-Jun as stand-by transcription factor characterize the beginning of neuroplastic changes, e.g., following ECS, a classic treatment of mental disorders. The N-terminal phosphorylation is compartment specific and can habituate following repetitive stimulation suggesting that the differential activation of the JNK/c-Jun axis is part of the neuronal strategy to integrate transynaptic excitation.

Animals↗

Evidence for the involvement of the pallidum in the modulation of seizures in a genetic model of absence epilepsy in the rat.

Inhibition of the subthalamic nucleus (STN) has been shown to suppress seizures in different animal models of epilepsy. The aim of this study was to examine the role of the pallidal inputs to the STN in the control of absence seizures in a genetic model in the rat. Disinhibition of the globus pallidus or the ventral pallidum, by local injections of a GABA(A) antagonist, suppressed absence seizures. Conversely, inhibition of the ventral pallidum by a GABA(A) agonist aggravated absence seizures. Furthermore, the antiepileptic effects of intrapallidal injections of a GABA(A) antagonist were correlated with a decrease of extracellular levels of glutamate in the substantia nigra. Our results show that both the globus pallidus and the ventral pallidum exert a modulatory influence on absence seizures and suggest that these effects are mediated through the STN.

Animals↗

Expression of mRNA encoding alpha1E and alpha1G subunit in the brain of a rat model of absence epilepsy.

Low voltage-activated calcium channels are thought to play a key role in the generation of spike and waves discharges characteristic of absence epilepsy. Therefore, the expression level of mRNA encoding calcium channel alpha1E and alpha1G subunits was measured in the brain of genetic absence epilepsy rats from Strasbourg (GAERS). Using quantitative RT-PCR and in situ hybridization, no difference was found in alpha1G mRNA expression between GAERS and control animals, while a decreased expression of alpha1E was seen in the cerebellum and the brain stem of the GAERS. This phenomenon was not observed in young animals when the epileptic phenotype is not expressed.

Animals↗

Spatial and temporal relationships between C-Fos expression and kindling of audiogenic seizures in Wistar rats.

In a strain of Wistar rats selected in our laboratory, audiogenic seizures (AS), characterized by a wild running phase followed by a tonic seizure, can be elicited by exposure to sound. In these animals repeated daily stimulations induce permanent changes which reflect the extension of seizure activity from the brainstem to the forebrain. C-Fos immunoreactivity was used to further characterize the sound-susceptibility of the strain and to specify the spatiotemporal relationships between c-Fos expression and development of AS kindling. AS susceptible rats appeared to be more sensitive to a subthreshold sound as compared to controls. Sound-evoked wild running induced a similar pattern of c-Fos as a full AS in naive rats, confirming the epileptic nature of this early component. AS-induced c-Fos labeling in the auditory pathways of the brainstem extended to the forebrain with repetition of AS and marked increases in c-Fos expression sequentially occurred in the amygdala and perirhinal cortex, followed by the frontoparietal cortex, the piriform cortex, and finally the hippocampus and entorhinal cortex. These results show that the kindled AS preferentially propagate from the brainstem, through the amygdala and the perirhinal cortex, to the motor cortex, with the piriform cortex and hippocampus as secondary targets. No more c-Fos expression was detected 24 h after an AS. A down-regulation of cortical c-Fos induction was observed 1 and 2 days after daily exposure to kindled AS, with full recovery of c-Fos expression after a 5-day seizure-free period. This suggests a regulatory function of c-Fos expression in development of kindling.

Acoustic Stimulation↗

Pertussis toxin decreases absence seizures and GABA(B) receptor binding in thalamus of a genetically prone rat (GAERS).

Postsynaptic GABA(B) receptor-mediated events have previously been shown to be reduced by prior treatment with pertussis toxin in rat brain. In the present study genetic absence epilepsy rats from Strasbourg (GAERS) were given single bilateral injections of pertussis toxin (PTx 0.4 microg), denatured-PTx or vehicle saline into the relay nuclei of the thalamus under anaesthesia. After recovery the spike and wave discharge duration (SWD) was monitored for up to 6 days following which the brains were removed and GABA(B) or GABA(A) receptor autoradiography performed on 10 microm transverse sections. By 6 days the SWD of the rats treated with PTx was suppressed by 96% compared with vehicle-injected rats with a significant (62%) reduction even after 1 day. Denatured toxin had no effect at any time. After 6 days GABA(B), but not GABA(A), receptor binding was significantly reduced by 70-80% in the ventrolateral and ventral posteriolateral thalamic nuclei. No changes in other brain regions were detected and denatured toxin failed to alter GABA(A) or GABA(B) receptor binding in any brain region. These data implicate G-protein mechanisms in the generation of SWD in GAERS and support the role of GABA(B) receptors in their induction within the thalamus.

Animals↗

Recurrent seizures and hippocampal sclerosis following intrahippocampal kainate injection in adult mice: electroencephalography, histopathology and synaptic reorganization similar to mesial temporal lobe epilepsy.

Human mesial temporal lobe epilepsy is characterized by hippocampal seizures associated with pyramidal cell loss in the hippocampus and dispersion of dentate gyrus granule cells. A similar histological pattern was recently described in a model of extensive neuroplasticity in adult mice after injection of kainate into the dorsal hippocampus [Suzuki et al. (1995) Neuroscience 64, 665-674]. The aim of the present study was to determine whether (i) recurrent seizures develop in mice after intrahippocampal injection of kainate, and (ii) the electroencephalographic, histopathological and behavioural changes in such mice are similar to those in human mesial temporal lobe epilepsy. Adult mice receiving a unilateral injection of kainate (0.2 microg; 50 nl) or saline into the dorsal hippocampus displayed recurrent paroxysmal discharges on the electroencephalographic recordings associated with immobility, staring and, occasionally, clonic components. These seizures started immediately after kainate injection and recurrid for up to eight months. Epileptiform activities occurred most often during sleep but occasionally while awake. The pattern of seizures did not change over time nor did they secondarily generalize. Glucose metabolic changes assessed by [14C]2-deoxyglucose autoradiography were restricted to the ipsilateral hippocampus for 30 days, but had spread to the thalamus by 120 days after kainate. Ipsilateral cell loss was prominent in hippocampal pyramidal cells and hilar neurons. An unusual pattern of progressive enlargement of the dentate gyrus was observed with a marked radial dispersion of the granule cells associated with reactive astrocytes. Mossy fibre sprouting occurred both in the supragranular molecular layer and infrapyramidal stratum oriens layer of CA3. The expression of the embryonic form of the neural cell adhesion molecule coincided over time with granule cell dispersion. Our data describe the first histological, electrophysiological and behavioural evidence suggesting that discrete excitotoxic lesions of the hippocampus in mice can be used as an isomorphic model of mesial temporal lobe epilepsy.

Animals↗

Susceptibility to focal and generalized seizures in Wistar rats with genetic absence-like epilepsy.

The susceptibility to develop cortically induced focal and generalized seizures was examined in Genetic Absence Epilepsy Rats from Strasbourg (GAERS), an inbred strain of Wistar rats with absence epilepsy. A GABA-withdrawal syndrome induced after suppression of a 2-h intracortical GABA infusion was used as a model of focal epileptogenesis: localized cortical discharges appear at the infusion site within 1 h. GAERS were more prone to develop a GABA-withdrawal syndrome than non-epileptic inbred controls and non-selected Wistar rats. After a transient suppression of absence seizures following GABA infusion in GAERS, generalized spike-and-wave discharges and focal spikes were recorded simultaneously in the cortex. GAERS also showed a higher incidence of systemic pentylenetetrazol-induced convulsions at the dose of 25 mg/kg. Higher doses had similar convulsant effects in all groups. In conclusion, the results confirm a genetic susceptibility in GAERS and/or resistance in inbred non-epileptic rats to focal and generalized seizures involving the cortex. Rats with absence epilepsy appear to be more prone to seizures elicited by cortical GABA deficiency.

Animals↗

Cerebral correlates of hemispheric lateralization during a pitch discrimination task: an ERP study in dichotic situation.

OBJECTIVE: Electrophysiological correlates of perceptual asymmetry for dichotic pitch discrimination were investigated in 12 right-handed volunteers, whose dichotic listening performances attested the classical 'right ear advantage' in a verbal discrimination task. METHODS: Event related potentials (ERPs), elicited by dichotic and binaural pairs of tones applied in a classical oddball paradigm including right ear targets, left ear targets and binaural targets (5% occurrence each) were recorded from medial and lateral scalp locations. Latencies and baseline to peak amplitudes were measured for P1, N1, P2, N2 and P3 components. RESULTS: ERPs recorded in response to dichotic (compared with binaural) target pairs, exhibited delayed latencies for N2 and P3, correlated with prolonged RTs, probably linked to greater difficulty in identification of the target. They also displayed enhanced N1 and P2 voltages, which may reflect the simultaneous activation of two different populations of neurons in the auditory cortical areas. We observed specific lateralization effects for pitch discrimination with a left ear advantage on latency of early components. CONCLUSIONS: Together with amplitude asymmetries in the N2 component, the findings bring strong electrophysiological support to Kimura's structural model for dichotic perceptions with a right hemisphere prevalence in a pitch discrimination task.

Acoustic Stimulation↗

Correlation between hypermetabolism and neuronal damage during status epilepticus induced by lithium and pilocarpine in immature and adult rats.

The correlation between seizure-induced hypermetabolism and subsequent neuronal damage was studied in 10-day-old (P10), 21-day-old (P21), and adult rats subjected to lithium-pilocarpine status epilepticus (SE). Local CMRglc (LCMRglc) values were measured by the [14C]2-deoxyglucose method for a duration of 45 minutes starting at 60 minutes after the onset of SE, and neuronal damage was assessed by cresyl violet staining at 6 days after SE. In P21 and adult rats, LCMRglc values were increased by 275 to 875% in all thalamic, cortical, forebrain, and hypothalamic regions plus the substantia nigra. In addition, at P21 there were also large increases in LCMRglc in brainstem regions. In P10 rats, metabolic increases were mostly located in cortical and forebrain regions plus the substantia nigra but did not affect hypothalamic, thalamic, or brainstem areas. In adult rats, there was an anatomical correlation between hypermetabolism and neuronal damage. At P21, although hypermetabolism occurred in regions with damage, the extent of damage varied considerably with the animals and ranged from an almost negligible to a very extended degree. Finally, in P10 rats, although quite pronounced hypermetabolism occurred, there was no neuronal damage induced by the seizures. Thus, in the present model of epilepsy, the correlation between marked hypermetabolism and neuronal damage can be shown in adult rats. Conversely, immature rats can sustain major metabolic activations that lead either to a variable extent of damage, as seen at P21, or no damage, as recorded at P10.

Aging↗

Combined measurements of hippocampal N-acetyl-aspartate and T2 relaxation time in the evaluation of mesial temporal lobe epilepsy: correlation with clinical severity and memory performances.

PURPOSE: In this study we tried to find a correlation between the clinical severity and memory performances, by comparing proton magnetic resonance (MR) spectroscopy and T2 relaxation time measurements in the hippocampi, in a homogeneous group of 27 patients with unilateral mesial temporal lobe epilepsy with ipsilateral hippocampal sclerosis on MR imaging, with a view to answer the following questions: (a) how sensitive is this approach for the assessment of the apparently normal contralateral hippocampus, (b) do the results relate to the clinical severity, and (c) does it allow evaluation of the degree of hippocampal dysfunction. METHODS: Volume-selective proton MR spectroscopy of the head of both hippocampi was performed at 3 T, by using the PRESS sequence, with an echo time of 135 ms, to estimate NAA/(Cho + Cr) ratios. The relaxation times were measured at 0.28 T, by using a conventional Carr-Purcell-Meiboom-Gill sequence, with a repetition time of 2,000 ms, an echo time of 15 ms, and 48 echoes. RESULTS: The combination of NAA/(Cho + Cr) ratio and T2 relaxation time values was allowed to classify contralateral hippocampus abnormalities in two groups: first, decreased NAA/(Cho + Cr) ratio with strongly increased T2 relaxation time values corresponding to abnormalities observed in sclerotic ipsilateral hippocampi; and second, decreased NAA/(Cho + Cr) ratio with normal or slightly increased T2 relaxation time values. Whereas the NAA/(Cho + Cr) ratio or T2 relaxation time value alone was not correlated with memory performances, their association shows that left hippocampal injury evaluated both by NAA and T2 relaxation time measurements was clearly correlated with verbal memory scores, and right hippocampal injury, with visual memory scores. On the other hand, the maximal seizure frequency reported by the patients was correlated with ipsilateral NAA/(Cho + Cr) ratio and T2 relaxation time values but not with contralateral results. CONCLUSIONS: We showed that the combination of NAA and T2 relaxation time measurements can be used to examine the degree of ipsi- and contralateral hippocampal dysfunction or injuries and their relations with memory performances in the presurgical evaluation of patients.

Adult↗

Lupus anticoagulant induced by the combination of valproate and lamotrigine.

A 5-year-old boy with generalized absence seizures was treated with valproate (VPA), 30 mg/kg/day. One month after VPA introduction, routine examination showed moderate reduction in fibrinogen and prolonged partial thromboplastin time (PTT). The search for lupus anticoagulant (LAC) was negative. After 10 months of VPA treatment, seizures persisted, and lamotrigine (LTG), 2 mg/kg/day, was progressively given with VPA. Seizures disappeared, but PTT was more prolonged than before LTG introduction. The search for LAC was positive, and enzyme-linked immunosorbent assays (ELISAs) for immunoglobulin G (IgG) anticardiolipid antibodies were positive. Serum autoantibody screen and rheumatoid factor were negative; serum complement was normal. LAC eventually disappeared with VPA discontinuation. We believe that LTG may have exacerbated an initially mild immune response induced by VPA without clinical evidence of systemic disease. We therefore suggest that careful surveillance for LAC and systemic disease should be instituted when VPA is used with LTG.

Antibodies, Anticardiolipin↗

Idiopathic rolandic epilepsy with "interictal" facial myoclonia and oromotor deficit: a longitudinal EEG and PET study.

PURPOSE: The prognosis of benign epilepsy with centrotemporal spikes (BECTS) is always favorable as far as the epilepsy is concerned. However, some data suggest that affected children may be at risk for minor cognitive impairment. We report here the longitudinal study of a young girl demonstrating that BECTS also may be associated with severe motor disturbances. METHODS: BECTS (rare left oromotor seizures, right rolandic spike-waves activated during sleep) started at the age of 3 years 6 months in a girl with normal initial psychomotor development. Her clinical, neuropsychological, and EEG status was assessed every 3-6 months. Regional cerebral glucose metabolism was measured by using the [18F]fluorodeoxyglucose-positron emission tomography (FDG-PET) method. RESULTS: Between the age of 5 and 6 years, the girl had (a) increased seizure frequency; (b) brief perioral and palpebral myoclonic jerks, concomitant with the spike component of interictal spike-waves, and (c) persistent but fluctuating oromotor deficits (drooling, dysarthria, dysphagia). The EEG showed a marked increase in abundance and amplitude of wake and sleep interictal abnormalities, which became bilateral. Awake FDG-PET revealed a bilateral increase of glucose metabolism in opercular regions. A complete and definitive EEG and clinical remission occurred at age 5 years 11 months and has persisted since (present age, 7 years 9 months). CONCLUSIONS: This case confirms that during BECTS, epileptiform dysfunctions within rolandic areas may induce "interictal" positive or negative oromotor symptoms, independent of classic seizures.

Brain↗