Abstracts

The range of physiologic and pathologic oscillations recorded from human brain extend well beyond what is commonly recorded with clinical acquisition systems. The range of local field activity in human epileptogenic brain extends from DC to [sim]700 Hz. The clinical relevance of DC fluctuations, infraslow oscillations (0.01-0.1 Hz) and ultrafast oscillations (100-700Hz) is unclear, but recent research supports the possible role of pathological high-frequency oscillations in the genesis of focal onset seizures., We studied 10 consecutive patients undergoing presurgical evaluation with hybrid subdural and depth electrodes. The custom hybrid depth and subdural electrodes (Adtech) used for intracranial EEG recordings contain an array of microwire electrodes (40um-60um) and clinical macroelectrodes (1-4mm). The EEG was acquired using a DC coupled broadband amplifier operating in parallel with the clinical EEG acquisition system., The broadband recordings from all 10 patients (5 neocortical grids and 5 temporal depth electrodes) showed oscillations extending from DC to [sim]700Hz. Infraslow oscillations and DC fluctuations tended to be more spatially distributed, but were most prominent in the region of seizure onset. Ultrafast oscillations ([gt]100 Hz) were most often localized, and were most prominent within the seizure onset zone. The ultrafast oscillations were most evident on the microwire electrodes, and were modulated by slow frequency oscillations., Human epileptogenic brain generates local field oscillations that extend over a wide dynamic range (DC-700 Hz). In addition to activity in the usual clinical bands ([sim]0.5-100Hz) there are DC fluctuations and shifts, infraslow frequency oscillations ([sim]0.01-0.1 Hz), and ultrafast oscillations ([gt]100-700 Hz) present. The presence of ultrafast oscillations are often highly localized and most evident on microwire recordings, but can be absent from large clinical macroelectrodes. This suggests that clinical macroelectrodes (2mm) may partially average out ultrafast local field potentials., (Supported by NIH/NINDS K23NS47495-03.)