Amphetamine disrupts haemodynamic correlates of prediction errors in nucleus accumbens and orbitofrontal cortex.

In an uncertain world, the ability to predict and update the relationships between environmental cues and outcomes is a fundamental element of adaptive behaviour. This type of learning is typically thought to depend on prediction error, the difference between expected and experienced events and in the reward domain that has been closely linked to mesolimbic dopamine. There is also increasing behavioural and neuroimaging evidence that disruption to this process may be a cross-diagnostic feature of several neuropsychiatric and neurological disorders in which dopamine is dysregulated. However, the precise relationship between haemodynamic measures, dopamine and reward-guided learning remains unclear. To help address this issue, we used a translational technique, oxygen amperometry, to record haemodynamic signals in the nucleus accumbens (NAc) and orbitofrontal cortex (OFC), while freely moving rats performed a probabilistic Pavlovian learning task. Using a model-based analysis approach to account for individual variations in learning, we found that the oxygen signal in the NAc correlated with a reward prediction error, whereas in the OFC it correlated with an unsigned prediction error or salience signal. Furthermore, an acute dose of amphetamine, creating a hyperdopaminergic state, disrupted rats' ability to discriminate between cues associated with either a high or a low probability of reward and concomitantly corrupted prediction error signalling. These results demonstrate parallel but distinct prediction error signals in NAc and OFC during learning, both of which are affected by psychostimulant administration. Furthermore, they establish the viability of tracking and manipulating haemodynamic signatures of reward-guided learning observed in human fMRI studies by using a proxy signal for BOLD in a freely behaving rodent.

Ketamine Suppresses the Ventral Striatal Response to Reward Anticipation: A Cross-Species Translational Neuroimaging Study.

Convergent evidence implicates regional neural responses to reward anticipation in the pathogenesis of several psychiatric disorders, such as schizophrenia, where blunted ventral striatal responses to positive reward are observed in patients and at-risk populations. In vivo oxygen amperometry measurements in the ventral striatum in awake, behaving rats reveal reward-related tissue oxygen changes that closely parallel blood oxygen level dependent (BOLD) signal changes observed in human functional magnetic resonance imaging (fMRI), suggesting that a cross-species approach targeting this mechanism might be feasible in psychopharmacology. The present study explored modulatory effects of acute, subanaesthetic doses of ketamine-a pharmacological model widely used in psychopharmacological research, both preclinically and clinically-on ventral striatum activity during performance of a reward anticipation task in both species, using fMRI in humans and in vivo oxygen amperometry in rats. In a region-of-interest analysis conducted following a cross-over placebo and ketamine study in human subjects, an attenuated ventral striatal response during reward anticipation was observed following ketamine relative to placebo during performance of a monetary incentive delay task. In rats, a comparable attenuation of ventral striatal signal was found after ketamine challenge, relative to vehicle, in response to a conditioned stimulus that predicted delivery of reward. This study provides the first data in both species demonstrating an attenuating effect of acute ketamine on reward-related ventral striatal (O2) and fMRI signals. These findings may help elucidate a deeper mechanistic understanding of the potential role of ketamine as a model for psychosis, show that cross-species pharmacological experiments targeting reward signaling are feasible, and suggest this phenotype as a promising translational biomarker for the development of novel compounds, assessment of disease status, and treatment efficacy.

Headache · fatigue · blurred vision · Dx?

One month after moving into her mother's apartment, a 27-year-old woman sought care at our clinic for fatigue, headache, blurred vision, nausea, and morning vomiting. She had weakness and difficulty sleeping, but denied any fever, rashes, neck stiffness, recent travel, trauma, or tobacco or illicit drug use. She did, however, have a 6-year history of migraines.

Dissociation of mGlu2/3 agonist effects on ketamine-induced regional and event-related oxygen signals.

RATIONALE: Validating preclinical biomarkers that predict treatment efficacy remains a critical imperative for neuropsychiatric drug discovery. With the establishment of novel in vivo imaging methods, it has become possible to think how such translational proof-of-concept studies may look. OBJECTIVES: The aim of this study was to use in vivo oxygen (O2) amperometry to simultaneously assess the regional and event/task-related O2 changes induced by ketamine challenge in rats, and to determine whether both of these signals are equivalently affected by the mGlu2/3 receptor agonist LY379268. METHODS: O2 signals were measured via carbon paste electrodes implanted in the anterior cingulate cortex (ACC) of rats trained to perform a simple reaction time task (SRT). SRT performance, event-related ACC O2 responses, and regional ACC O2 signal were recorded simultaneously in animals treated with ketamine (10 mg/kg) and/or LY379268 (3 mg/kg). RESULTS: A consistent relationship was observed between baseline SRT performance and related ACC O2 signals, suggesting that ACC engagement is likely to be a requirement for optimal task performance. Ketamine induced a robust and consistent slowing in reaction times that was reflected by a delayed event-related ACC O2 signal increase compared to vehicle controls. Ketamine also produced a regional and task-independent 60-min increase in ACC O2 levels which was effectively attenuated by LY379268. However, LY379238 failed to reverse alterations in event-related O2 signals and associated SRT task performance. CONCLUSIONS: These findings raise questions about the degree to which such reversals of regional ketamine O2 signals could potentially be claimed to predict drug treatment efficacy.

Phenotypic characterization of nonsocial behavioral impairment in neurexin 1α knockout rats.

Neurexins are neuronal presynaptic proteins that play a key role in mediation of synapse formation. Heterozygous partial deletions in the neurexin-1 gene (NRXN1, 2p16.3) have been observed in autism spectrum disorder (ASD) patients. NRXN1-α knockout (KO) mice present behavioral impairments that resemble some of the core ASD symptoms of social impairment and inflexibility/stereotypy. At present, a thorough assessment of cognitive function has yet to be completed. Rats, containing a biallelic deletion of the NRNX1-α gene on a Sprague Dawley background were compared to littermate wild types across a range of tasks designed to test functional domains disrupted in ASD and other neurodevelopmental disorders, including sensory perception (prepulse inhibition), attention (latent inhibition), associative learning (instrumental and Pavlovian conditioning), and memory (rewarded alternation T maze and spatial discrimination). NRXN1α KO rats were found to present with large and persistent nonsocial deficits, including hyperactivity, deficits in simple instrumental learning, latent inhibition, and spatial-dependent learning. No deficit in sensorimotor gating was observed, despite the presence of an exaggerated startle response. Although KO animals were also able to learn a simple Pavlovian conditioning discrimination, they did display impaired latent inhibition. The presence of pronounced impairments in several domains in NRXN1α KO rats clearly suggests that nonsocial cognitive deficits can also be measured in an animal model of ASD. Further exploration of those deficits, both clinically and preclinically, as planned in the Innovative Medicines Initiative's European Autism Interventions: A Multicenter Study for Developing New Medications program, may help to better understand the brain circuitry involved in ASD and therefore open new avenues to advance novel therapies.

Differential contributions of infralimbic prefrontal cortex and nucleus accumbens during reward-based learning and extinction.

Using environmental cues for the prediction of future events is essential for survival. Such cue-outcome associations are thought to depend on mesolimbic circuitry involving the nucleus accumbens (NAc) and prefrontal cortex (PFC). Several studies have identified roles for both NAc and PFC in the expression of stable goal-directed behaviors, but much remains unknown about their roles during learning of such behaviors. To further address this question, we used in vivo oxygen amperometry, a proxy for blood oxygen level-dependent (BOLD) signal measurement in human functional magnetic resonance imaging, in rats performing a cued lever-pressing task requiring discrimination between a rewarded and nonrewarded cue. Simultaneous oxygen recordings were obtained from infralimbic PFC (IFC) and NAc throughout both acquisition and extinction of this task. Activation of NAc was specifically observed following rewarded cue onset during the entire acquisition phase and also during the first days of extinction. In contrast, IFC activated only during the earliest periods of acquisition and extinction, more specifically to the nonrewarded cue. Thus, in vivo oxygen amperometry permits a novel, stable form of longitudinal analysis of brain activity in behaving animals, allowing dissociation of the roles of different brain regions over time during learning of reward-driven instrumental action. The present results offer a unique temporal perspective on how NAc may promote actions directed toward anticipated positive outcome throughout learning, while IFC might suppress actions that no longer result in reward, but only during critical periods of learning.

Dissociable effects of antipsychotics on ketamine-induced changes in regional oxygenation and inter-regional coherence of low frequency oxygen fluctuations in the rat.

Typical and atypical antipsychotics have been shown to alleviate N-methyl-D-aspartate (NMDA) receptor antagonist-induced BOLD signals in healthy humans and animals to differing degrees; factors that might relate to their different molecular mechanisms and clinical profiles. Recent studies have also extended these investigations to the analysis of resting state functional connectivity measures of BOLD signals in different brain regions. Using constant potential amperometry, we examined the effects of the NMDA receptor antagonist S-(+)-ketamine on tissue oxygen levels in medial prefrontal cortex (mPFC) and medial ventral striatum (mVS), and temporal coherence of low-frequency oxygen fluctuations between these regions in freely moving rats. Furthermore, we assessed the extent to which the atypical antipsychotic clozapine and the typical antipsychotic haloperidol could modulate the effects of S-(+)-ketamine on these measures. Acute S-(+)-ketamine (5-25 mg/kg) produced dose-dependent increases in both tissue O2 levels and coherence. Although effects of clozapine and haloperidol alone were relatively minor, their effects on ketamine-induced signals were markedly more distinct. Clozapine dose-dependently attenuated the absolute S-(+)-ketamine (25 mg/kg) O2 signal in both regions, and also attenuated ketamine-induced increases in regional coherence. Haloperidol had no effect on the absolute ketamine O2 signal yet potentiated increases in regional coherence. The dissociable effects of haloperidol and clozapine on ketamine-induced hyperoxygenation and mPFC-mVS coherence elucidate potentially important mechanistic differences between these classes of pharmacology. This study demonstrates for the first time that in vivo amperometry can measure both regional brain tissue O2 levels and inter-regional coherence, advancing BOLD-like measurements of functional connectivity into awake, unconstrained animals.

Prefrontal cholinergic mechanisms instigating shifts from monitoring for cues to cue-guided performance: converging electrochemical and fMRI evidence from rats and humans.

We previously reported involvement of right prefrontal cholinergic activity in veridical signal detection. Here, we first recorded real-time acetylcholine release in prefrontal cortex (PFC) during specific trial sequences in rats performing a task requiring signal detection as well as rejection of nonsignal events. Cholinergic release events recorded with subsecond resolution ("transients") were observed only during signal-hit trials, not during signal-miss trials or nonsignal events. Moreover, cholinergic transients were not observed for consecutive hits; instead they were limited to signal-hit trials that were preceded by factual or perceived nonsignal events ("incongruent hits"). This finding suggests that these transients mediate shifts from a state of perceptual attention, or monitoring for cues, to cue-evoked activation of response rules and the generation of a cue-directed response. Next, to determine the translational significance of the cognitive operations supporting incongruent hits we used a version of the task previously validated for use in research in humans and blood oxygenation level-dependent (BOLD)-functional magnetic resonance imaging. Incongruent hits activated a region in the right rostral PFC (Brodmann area 10). Furthermore, greater prefrontal activation was correlated with faster response times for incongruent hits. Finally, we measured tissue oxygen in rats, as a proxy for BOLD, and found prefrontal increases in oxygen levels solely during incongruent hits. These cross-species studies link a cholinergic response to a prefrontal BOLD activation and indicate that these interrelated mechanisms mediate the integration of external cues with internal representations to initiate and guide behavior.

Changes in reward-related signals in the rat nucleus accumbens measured by in vivo oxygen amperometry are consistent with fMRI BOLD responses in man.

Real-time in vivo oxygen amperometry, a technique that allows measurement of regional brain tissue oxygen (O(2)) has been previously shown to bear relationship to the BOLD signal measured with functional magnetic resonance imaging (fMRI) protocols. In the present study, O(2) amperometry was applied to the study of reward processing in the rat nucleus accumbens to validate the technique with a behavioural process known to cause robust signals in human neuroimaging studies. After acquisition of a cued-lever pressing task a robust increase in O(2) tissue levels was observed in the nucleus accumbens specifically following a correct lever press to the rewarded cue. This O(2) signal was modulated by cue reversal but not lever reversal, by differences in reward magnitudes and by the motivational state of the animal consistent with previous reports of the role of the nucleus accumbens in both the anticipation and representation of reward value. Moreover, this modulation by reward value was related more to the expected incentive value rather than the hedonic value of reward, also consistent with previous reports of accumbens coding of "wanting" of reward. Altogether, these results show striking similarities to those obtained in human fMRI studies suggesting the use of oxygen amperometry as a valid surrogate for fMRI in animals performing cognitive tasks, and a powerful approach to bridge between different techniques of measurement of brain function.

Carisbamate has powerful disease-modifying effects in the lithium-pilocarpine model of temporal lobe epilepsy.

Lithium-pilocarpine, a relevant model of temporal lobe epilepsy was used to test the neuroprotective and antiepileptogenic effects of carisbamate. Status epilepticus (SE) was induced in adult rats by lithium and pilocarpine. Carisbamate (30, 60, 90, and 120 mg/kg) was injected at 1 and 9 h after SE onset and continued twice daily for 6 additional days. The reference groups received diazepam instead of carisbamate. Neuroprotection was assessed during the first 24 h of SE with Fluoro-Jade B and after 14 days with thionine staining. SE severity and epileptic outcome were assessed by video, and surface and depth electroencephalographic recordings. At the two highest doses, carisbamate treatment reduced SE severity; produced strong neuroprotection of hippocampus, ventral cortices, thalamus, and amygdala; prevented mossy fiber sprouting in the dentate gyrus of the hippocampus; and delayed or suppressed the occurrence of spontaneous motor seizures. Rats with no spontaneous motor seizures displayed spike-and-wave discharges that share all the characteristics of absence seizures. In conclusion, carisbamate is able to induce strong neuroprotection and affect the nature of epileptogenic events occurring during and after lithium-pilocarpine status epilepticus, reflecting marked insult- and disease-modifying effects.

Characterisation of carbon paste electrodes for real-time amperometric monitoring of brain tissue oxygen.

Tissue O2 can be monitored using a variety of electrochemical techniques and electrodes. In vitro and in vivo characterisation studies for O2 reduction at carbon paste electrodes (CPEs) using constant potential amperometry (CPA) are presented. Cyclic voltammetry indicated that an applied potential of -650 mV is required for O2 reduction at CPEs. High sensitivity (-1.49 ± 0.01 nA/µM), low detection limit (ca. 0.1 µM) and good linear response characteristics (R² > 0.99) were observed in calibration experiments performed at this potential. There was also no effect of pH, temperature, and ion changes, and no dependence upon flow/fluid convection (stirring). Several compounds (e.g. dopamine and its metabolites) present in brain extracellular fluid were tested at physiological concentrations and shown not to interfere with the CPA O2 signal. In vivo experiments confirmed a sub-second response time observed in vitro and demonstrated long-term stability extending over twelve weeks, with minimal O2 consumption (ca. 1 nmol/h). These results indicate that CPEs operating amperometrically at a constant potential of -650 mV (vs. SCE) can be used reliably to continuously monitor brain extracellular tissue O2.

Metabolic activity in the brain of juvenile and adult rats with a neonatal ventral hippocampal lesion.

Longitudinal studies on patients for schizophrenia suggest that functional brain perturbations precede the onset of symptoms. Rats with a neonatal ventral hippocampal lesion (NVHL) are considered as a heuristic neurodevelopmental model of schizophrenia. We characterized basal metabolic changes observed in NVHL rats before and after the age when known behavioral alterations have been reported. Male pups were lesioned with ibotenic acid at postnatal day 7 (PD7). We measured local cerebral metabolic rates for glucose (LCMRglc) by the quantitative autoradiographic [(14)C]2-deoxyglucose technique at pre- (PD21) and postpubertal (PD42) ages when NVHL rats do not express abnormal dopamine related behaviors, and at adulthood (PD70). We observed a widespread increase in LCMRglcs in PD21 NVHL indicative of an ongoing intense reorganization of the brain while at PD42, increases were less extended. At PD70, changes in glucose metabolism were restricted to specific systems, such as the auditory system, the cerebellum, the serotonergic median raphe, and median septum. These data show in a heuristic animal model of schizophrenia that functional metabolic changes within the brain could precede the onset of dopamine-related behavioral alterations and lead to a distinct ensemble of functional changes in adulthood in systems that may be relevant to schizophrenia.

Selective reorganization of GABAergic transmission in neonatal ventral hippocampal-lesioned rats.

Post-mortem studies suggested a disturbance of the GABAergic system in schizophrenia. Neonatal ventral hippocampal-lesioned (NVHL) rats were used as a neurodevelopmental model of schizophrenia. Here, we characterized the GABAergic system, focusing on the GABA-synthesizing enzyme, GAD67, GABAergic interneuron characteristic proteins, and the GABA transporter, gat-1. As the GABAergic system is crucial to brain excitability, the sensitivity to pentylenetetrazol (PTZ) administration, an antagonist of GABAA receptors, was also evaluated in such rats. Male pups were lesioned with ibotenic acid at postnatal day 7. As adults, they were submitted to standard behavioural tests, i.e. prepulse inhibition of the startle reflex and increased locomotion under apomorphine, to assess the effectiveness of the lesions and the PTZ infusion test before immunohistochemistry of the GABAergic neuron markers. We found a widespread perturbation of the enzyme responsible for GABA synthesis, GAD67 and a decrease of specific interneurons, restricted to the hippocampus, entorhinal and prefrontal cortex, but no alteration of gat-1-positive fibres. The usual behavioural properties of the model, such as hyperlocomotion under apomorphine and a deficit in sensorimotor gating were confirmed. NVHL rats showed changes in cortical excitability reflected by higher susceptibility than sham-operated rats to spike wave discharges and decreased susceptibility to clonic seizures, induced by increasing the dose of PTZ. These findings indicate that a neonatal lesion of the ventral hippocampus elicits alterations in the GABAergic system leading to functional consequences on brain excitability, lending support to the idea that GABAergic systems could be involved in the pathophysiology of schizophrenia.

Calorie-restricted ketogenic diet increases thresholds to all patterns of pentylenetetrazol-induced seizures: critical importance of electroclinical assessment.

PURPOSE: Thresholds to pentylenetetrazol (PTZ) seizures were usually based only on clinical symptoms. Our purpose was to use electroclinical patterns to assess the efficacy of a ketogenic and/or calorie-restricted diet on PTZ-induced seizures. METHODS: Forty 50-day-old rats were divided in four weight-matched groups and fed controlled diets: normocalorie carbohydrate (NC), hypocalorie carbohydrate (HC), normocalorie ketogenic (NK), and hypocalorie ketogenic (HK). After 21 days, blood glucose and beta-hydroxybutyrate levels were determined and seizures were induced by continuous infusion of PTZ. The clinical and EEG thresholds to each seizure pattern were compared between the different groups. RESULTS: The electroclinical course of PTZ-induced seizures was similar in all groups. The HK group exhibited higher thresholds than the other ones for most clinical features: absence (p = 0.003), first overt myoclonia (p = 0.028), clonic seizure (p = 0.006), and for EEG features: first spike (p = 0.036), first spike-and-wave discharge (p = 0.014), subcontinuous spike-and-wave discharges (p = 0.005). NK, HC, and NC groups were not significantly different from each other. Blood glucose and beta-hydroxybutyrate levels were not correlated with electroclinical seizure thresholds. After the clonic seizure, despite stopping PTZ infusion, a tonic seizure occurred in some animals, without significant difference regarding the diet. CONCLUSION: This approach permitted a precise study of the electroclinical course of PTZ-induced seizures. In addition to the usually studied first overt myoclonia, we clearly demonstrated the efficiency of a calorie restricted KD in elevating thresholds to most electroclinical seizure patterns. We confirmed the lack of efficiency of the KD to reduce seizure severity once the seizure has started.

Effects of carisbamate (RWJ-333369) in two models of genetically determined generalized epilepsy, the GAERS and the audiogenic Wistar AS.

PURPOSE: The antiepileptic effects of carisbamate were assessed in two models of genetic epilepsy, a model of absence seizures, the Genetic Absence Epilepsy Rat from Strasbourg (GAERS) and a model of convulsive seizures, the Wistar Audiogenic Sensitive (AS) rat. METHODS: GAERS were equipped with four cortical electrodes over the frontoparietal cortex and the duration of spike-and-wave discharges (SWD) was recorded for 20-120 min. In Wistar AS, the occurrence of, latency to, and duration of wild running and tonic seizures were recorded. RESULTS: In GAERS, carisbamate (10, 30, and 60 mg/kg) dose dependently reduced the expression of SWD that totally disappeared at the two highest doses by 40 min after injection. SWD duration returned to control levels by 100 min after the injection of 30 mg/kg carisbamate while SWDs were totally suppressed for 120 min after the injection of 60 mg/kg carisbamate. In Wistar AS, 10 mg/kg carisbamate increased the latency to the first running episode and induced the occurrence of a second running episode in three of eight rats. This episode was not present in untreated rats and was indicative of decreased sensitivity to the stimulus. This dose of carisbamate increased by 327% the latency to the tonic seizure that still occurred in the six of eight rats studied. At 20 and 30 mg/kg, no rats exhibited any wild running or tonic seizure. CONCLUSIONS: The present results support the broad spectrum of antiepileptic activity of carisbamate confirming its efficacy in animal models of primary generalized seizures of both tonic-clonic and of the absence type.

Pathogenesis and pharmacology of epilepsy in the lithium-pilocarpine model.

To try to identify the critical structures during epileptogenesis, we used the lithium-pilocarpine model that reproduces most clinical and neuropathological features of temporal lobe epilepsy (TLE). We used imaging techniques as well as a disease modifying approach and pharmacological strategy. With [14C]-2-deoxyglucose autoradiography, we assessed changes in cerebral glucose utilization. T2-weighted magnetic resonance imaging (MRI, 4.7 T) allowed follow-up of structures involved in epileptogenesis. A potential disease-modifying effect was studied using preconditioning with brief seizures (amygdala kindling, maximal electroshocks) and pharmacological strategies including vigabatrin (250 mg/kg), caffeine (0.3 g/L in drinking water), topiramate (10-60 mg/kg), pregabalin (50 mg/kg followed by 10 mg/kg), or RWJ-333369 (10-120 mg/kg). In adult and PN21 rats that became epileptic, entorhinal, and piriform cortices were the initial structures exhibiting significant signal changes on MRI scans, from 6 h after status epilepticus (SE) onset, reflecting neuronal death. In PN21 rats that did not become epileptic, no signal occurred in parahippocampal cortices. In hippocampus, MRI signal change appeared 36-48 h after SE, and progressively worsened to sclerosis. During the latent and chronic phases, the metabolic level in the hilus of adult and PN21 epileptic rats was normal although neuronal loss reached 60-75%. Protection limited to CA1 and/or CA3 (caffeine, topiramate, vigabatrin, amygdala kindling) did not affect the latency to spontaneous seizures. Protection limited to the entorhinal and piriform cortices (pregabalin) delayed epileptogenesis. The combined protection of Ammon's horn and parahippocampal cortices (RWJ-333369) prolonged the latency before the onset of seizures in a dose-dependent manner or, in some cases, prevented the epilepsy. The entorhinal and piriform cortices are critically involved in the early phase of the epileptogenesis while the hilus may initiate and/or maintain epileptic seizures. Pharmacological protection of the basal cortices is necessary for a beneficial disease-modifying effect but this must be combined with protection of the hippocampus to prevent epileptogenesis in this model of TLE.

The combination of topiramate and diazepam is partially neuroprotective in the hippocampus but not antiepileptogenic in the lithium-pilocarpine model of temporal lobe epilepsy.

Lithium-pilocarpine induces status epilepticus (SE), leading to extensive damage and spontaneous recurrent seizures (SRS). Neuroprotective and antiepileptogenic effects of topiramate (TPM) associated with diazepam (DZP) were investigated in this model. SE was induced by LiCl and pilocarpine. TPM (10, 30 or 60 mg/kg) was injected at the onset of SE and 10h later and DZP (2.5 and 1.25mg/kg) at 2 and 10h after SE. TPM treatment was continued twice daily for 6 days. Other rats received two injections of DZP on the day of SE. Cell counting was performed on thionine-stained sections 14 days after SE and after 2 months of epilepsy. Occurrence and frequency of SRS were video-recorded. The MRI T2-weighted signal was quantified in hippocampus and ventral cortices. DZP-TPM treatment induced partial neuroprotection in CA1 and hilus, and tended to increase the percentage of rats with protected neurons in layer III/IV of the ventral entorhinal cortex. The latency to and frequency of SRS were not modified by DZP-TPM. T2-weighted signal was decreased in hippocampus 3 days after SE at all TPM doses and in ventral hippocampus after epilepsy onset. In conclusion, although DZP-TPM treatment was able to partially protect two areas critical for epileptogenesis, the hippocampus and ventral entorhinal cortex, it was not sufficient to prevent epileptogenesis.