Which term refers to very high voltage, generalized, but anterior-dominant fast activity sometimes found in mental retardation?

The term that refers to very high voltage, generalized, but anterior-dominant fast activity sometimes found in mental retardation is "Extreme spindles." Extreme spindles are characterized by their prominence and atypicality compared to standard spindles, both in terms of voltage and distribution across the EEG. They can manifest as a burst of fast activity in the anterior region of the brain, which is often observed in individuals with cognitive impairments, including mental retardation. The presence of these extreme spindles can provide important insights into the neurological status of the individual and may correlate with specific developmental or cognitive conditions.

Standard, regular, and fast rhythm spindles do not embody the same characteristics regarding their high-voltage and anterior dominance, which is why they do not apply to this particular instance as accurately as extreme spindles do.