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Learning sequences of events (e.g., a-b-c) is conceptually a simple problem that can be solved using asymmetrically linked cell assemblies [e.g., "phase sequences" (Hebb, 1949)], provided that the elements of the sequence are unique. When elements repeat within the sequence, however (e.g., a-b-c-d-b-e), the same element belongs to two separate "contexts,"(More)
Focal seizures appear to start abruptly and unpredictably when recorded from volumes of brain probed by clinical intracranial electroencephalograms. To investigate the spatiotemporal scale of focal epilepsy, wide-bandwidth electrophysiological recordings were obtained using clinical macro- and research microelectrodes in patients with epilepsy and control(More)
Synchronization of local and distributed neuronal assemblies is thought to underlie fundamental brain processes such as perception, learning, and cognition. In neurological disease, neuronal synchrony can be altered and in epilepsy may play an important role in the generation of seizures. Linear cross-correlation and mean phase coherence of local field(More)
Although much is known about persistent molecular, cellular, and circuit changes associated with temporal lobe epilepsy, mechanisms of seizure onset remain unclear. The dentate gyrus displays many persistent epilepsy-related abnormalities and is in the mesial temporal lobe where seizures initiate in patients. However, little is known about seizure-related(More)
The use of large-scale electrophysiology to obtain high spatiotemporal resolution brain recordings (>100 channels) capable of probing the range of neural activity from local field potential oscillations to single-neuron action potentials presents new challenges for data acquisition, storage, and analysis. Our group is currently performing continuous,(More)
Vasospasm is a major contributor to morbidity and mortality in aneurysmal subarachnoid hemorrhage (SAH), with inflammation playing a key role in its pathophysiology. Myeloperoxidase (MPO), an inflammatory marker, was examined as a potential marker of vasospasm in patients with SAH. Daily serum samples from patients with aneurysmal SAH were assayed for MPO,(More)
Loss of heterozygosity (LOH) for chromosome 10 is the most frequent genetic abnormality observed in high-grade gliomas. We have used fluorescent microsatellite markers to examine a series of 83 patients, 34 with anaplastic astrocytoma (grade 3) and 49 with glioblastoma multiforme (grade 4), for LOH of chromosome 10. Genotype analysis revealed LOH for all(More)
An emergent problem in the study of pathogen evolution is our ability to determine the extent to which their rapidly evolving genomes recombine. Such information is necessary and essential for locating pathogenicity loci using association studies, and it also directs future screening, therapeutic and vaccination strategies. Recombination also complicates(More)
PURPOSE   Focal seizures are thought to reflect simultaneous activation of a large population of neurons within a discrete region of pathologic brain. Resective surgery targeting this focus is an effective treatment in carefully selected patients, but not all. Although in vivo recordings of single-neuron (i.e., "unit") activity in patients with epilepsy(More)
High frequency oscillations are associated with normal brain function, but also increasingly recognized as potential biomarkers of the epileptogenic brain. Their role in human cognition has been predominantly studied in classical gamma frequencies (30-100 Hz), which reflect neuronal network coordination involved in attention, learning and memory. Invasive(More)