Prominent oligodendroglial response in surgical specimens of patients with temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is characterized by distinct neuropathological findings, such as hippocampal sclerosis and reactive astrogliosis. Recently, MRI studies have revealed the presence of white matter pathology in brains of epilepsy patients. The purpose of this study is to evaluate the involvement of oligodendroglia in the epileptogenic process. Using TPPP/p25 as a marker for mature oligodendroglia, we evaluated the hippocampus in 26 surgical specimens from patients with TLE and 9 autopsy controls without neuropathological alterations for changes in oligodendroglial cell densities (mm2) in hippocampal, entorhinal, and temporal white matter, and the amount of perineuronal oligodendrocytes in CA1 subregion. Oligodendrocyte cell densities were significantly elevated in epilepsy patients compared to controls in all four examined white matter subregions. In addition, in the CA1 sector, the percentage of neurons showing more than one perineuronal oligodendrocyte was significantly higher in epilepsy patients. In conclusion, our study expands the glial reactions beyond astrogliosis and shows that prominent oligodendroglial response is a consistent pathological feature characteristic for TLE.

Harmonic context influences pitch class equivalence judgments through gestalt and congruency effects.

The context in which a stimulus is presented shapes the way it is processed. This effect has been studied extensively in the field of visual perception. Our understanding of how context affects the processing of auditory stimuli is, however, rather limited. Western music is primarily built on melodies (succession of pitches) typically accompanied by chords (harmonic context), which provides a natural template for the study of context effects in auditory processing. Here, we investigated whether pitch class equivalence judgments of tones are affected by the harmonic context within which the target tones are embedded. Nineteen musicians and 19 non-musicians completed a change detection task in which they were asked to determine whether two successively presented target tones, heard either in isolation or with a chordal accompaniment (same or different chords), belonged to the same pitch class. Both musicians and non-musicians were most accurate when the chords remained the same, less so in the absence of chordal accompaniment, and least when the chords differed between both target tones. Further analysis investigating possible mechanisms underpinning these effects of harmonic context on task performance revealed that both a change in gestalt (change in either chord or pitch class), as well as incongruency between change in target tone pitch class and change in chords, led to reduced accuracy and longer reaction times. Our results demonstrate that, similarly to visual processing, auditory processing is influenced by gestalt and congruency effects.