Larger cortical motor maps after seizures.

Expansion of motor maps occurs in both clinical populations with epilepsy and in experimental models of epilepsy when the frontal lobes are involved. We have previously shown that the forelimb area of the motor cortex undergoes extensive enlargement after seizures, although the extent to which many movement representation areas are altered is not clear. Here we hypothesize that movement representations in addition to the forelimb area will be enlarged after cortical seizures. To test our hypotheses, Long Evans Hooded rats received 20 sessions of callosal (or sham) kindling, and then were subjected to intracortical microstimulation to map several movement representations including the jaw, neck, forelimb, hindlimb, trunk and tail. We found significantly larger total map areas of several movement representations, including movements that could be evoked more posterior than they are in control rats. We also show the presence of more multiple movement sites and lower movement thresholds in kindled rats, suggesting that movements not only overlap and share cortical territory after seizures, but become present in formerly non-responsive sites as they become detectable with our intracortical microstimulation methodology. In summary, several motor map areas become larger after seizures, which may contribute to the interictal motor disturbances that have been documented in patients with epilepsy.

Persistent enhancement of functional MRI responsiveness to sensory stimulation following repeated seizures.

PURPOSE: Neural reorganization and interictal behavioral anomalies have been documented in people with epilepsy and in animal seizure models. Alterations in behavior could be due to somatosensory dysfunction. This study was designed to determine whether seizures can lead to changes in somatosensory representations and whether those changes are persistent. METHODS: Twice-daily seizures were elicited by delivering 1 s of electrical stimulation through carbon fiber electrodes implanted in both the corpus callosum and sensorimotor neocortex of young adult male Long-Evans rats until a total of 20 seizures were elicited. Either 1-3 days or 3-5 weeks following the last seizure, functional magnetic resonance imaging (MRI) was used to image the brain during electrical stimulation of each forepaw independently. KEY FINDINGS: Forepaw stimulation in control rats resulted in a focused and contralateral fMRI signal in the somatosensory neocortex. Rats that had repeated seizures had a 151% increase in the number of voxels activated in the contralateral hemisphere 1-3 days after the last seizure and a 166% increase at 3-5 weeks after the last seizure. The number of voxels activated in response to forepaw stimulation was positively correlated with the duration of the longest seizure experienced by each rat. The intensity of the activated voxels was not significantly increased at either time interval from the last seizure. SIGNIFICANCE: The increased area of activation in somatosensory cortex, which is persistent at 3-5 weeks, is consistent with previous observations of larger motor maps following seizures. Seizure-induced changes in the functioning of sensory cortex may also contribute to interictal behavioral anomalies.

Functional brain mapping at 9.4T using a new MRI-compatible electrode chronically implanted in rats.

There is a need for acute and chronic stimulation of the brain within the MRI for studies of epilepsy, as well as deep brain stimulation for movement and behavioral disorders. This work describes the production and characteristics of carbon fiber-based electrodes for acute and chronic stimulation in the brain. Increasing MRI field strengths are making it increasingly difficult to introduce foreign objects without a susceptibility artifact. We describe the production of, and the characteristics of carbon fiber-based electrodes. These are biocompatible and can be implanted for chronic studies. We show the use of these electrodes at 9.4T for studying functional activation. Data are presented showing regional connectivity. Activation not only occurs near the electrode, but at sites distant and often contralateral to the electrode. In addition, there were sites showing strong negative activation to stimulation both with direct stimulation and during a kindling-associated seizure.

Cortical kindling induces elevated levels of AMPA and GABA receptor subunit mRNA within the amygdala/piriform region and is associated with behavioral changes in the rat.

Cortical kindling causes alterations within the motor cortex and results in long-standing motor deficits. Less attention has been directed to other regions that also participate in the epileptiform activity. We examined if cortical kindling could induce changes in excitatory and inhibitory receptor subunit mRNA in the amygdala/piriform regions and if such changes are associated with behavioral deficits. After cortical kindling, amygdala/piriform regions were dissected to analyze mRNA levels of NMDA, AMPA, and GABA receptor subunits using reverse transcription polymerase chain reaction, or rats were subjected to a series of behavioral tests. Kindled rats had significantly greater amounts of GluR1 and GluR2 AMPA receptor mRNA, and alpha1 and alpha2 GABA receptor subunit mRNA, compared with sham controls, which was associated with greater anxiety-like behaviors in the elevated plus maze and reduced freezing behaviors in the fear conditioning task. In summary, cortical kindling produces dynamic receptor subunit changes in regions in addition to the seizure focus.

Motor maps, seizures, and behaviour.

Atypically organised motor maps have been described in some people with epilepsy and we have modelled this in rats. Our goal is to more fully understand the mechanisms responsible for seizure-induced functional brain reorganisation and to reverse their effects. Here we present an overview of the relationship between neocortical motor maps, seizures, and interictal behaviour. To begin we summarise the observations of atypical motor maps with epilepsy and in animal models following experimentally induced seizures. Our novel experiments have established that motor map expansion is linked to a functional alteration of motor behaviour. Evidence for some of the putative brain mechanisms responsible for motor map size is discussed. Our successes reversing seizure-induced map expansion by two different methods are also briefly reviewed. Lastly, unanswered questions for possible future experimentation are posed.

A comparison of two systems for chlorinating water in rural Honduras.

This study investigated a small subset of the two community water-disinfection systems--hypochlorinators and tablet feeders-in rural Honduras. Levels of residual chlorine were assessed at three locations within the distribution system: the tank, the proximal house, and the distal house. The levels of residual chlorine were compared with the standard guidelines set by the Pan American Health Organization and the International Rural Water Association for potable water that require a minimum of 1.0 (tank), 0.5 (proximal house), and 0.2 (distal house) ppm for each location. The levels of residual chlorine were also compared across systems, e.g. hypochlorinators to tablet feeders. At the tank and proximal house, tablet feeders had significantly higher mean values for levels of residual chlorine (measured in ppm) than hypochlorinators (tank: 1.20 vs 0.67; proximal house: 0.44 vs 0.32, p < 0.001 for both) with no significant difference at the distal house (0.16 vs 0.16). At the tank and proximal house, tablet feeders were more likely to meet recommended standards than hypochlorinators (90.3% vs 13.3%, p < 0.0001 and 41.3% vs 23.7%, p < 0.0001) with a smaller difference seen at the distal house (30.6% vs 27.1%, p = 0.24). The apparent dichotomy in chlorine levels of tablet feeders (e.g. between tank/proximal house and distal house) is discussed. The results suggest that tablet feeders may be more effective than hypochlorinators in supplying clean water in rural, resource-poor settings and possibly serve as an alternative technology for water disinfection. Further research on techniques for empowering and building capacity within community water boards will help organize and introduce sustainable water systems in developing countries.