Cortical processing of vowels and tones as measured by event-related desynchronization

Abstract

Event-Related Desynchronization (ERD) and Synchronization (ERS) were studied in 20 normal subjects during a Sternberg-type auditory memory-scanning paradigm. Half of the subjects performed the experiment with vowels and the other half with tones as stimuli. The stimuli consisted of 100 msec long synthesized vowels and 100 msec long tones produced by eight different synthesized instruments. In this paradigm each trial started with the presentation of a visual warning signal, after which a four-stimulus set was presented for memorization whether after a probe stimulus was presented and identified by the subject as belonging or not belonging to the memorized set. The ERD/ERS of the lower (8-10 Hz) and upper (10-12 Hz) alpha frequency bands differed in their reactivity to stimulus type; the differences between the two frequency bands reached statistical significance only in the case of vowels. The presentation of the memory set elicited ERS which was more pronounced in the 10-12 Hz frequency band and greater for vowels than for tones. On the other hand, the presentation of the probe elicited ERD which was greater for vowels than for tones, especially in the upper alpha frequency band. The results of this exploratory study suggest that ERD is closely related to memory process and that the ERD/ERS-technique might provide a valuable tool for future research encompassing more complex auditory stimulation like speech and music.

Auditory processing indexed by stimulus-induced alpha desynchronization in children

“…3) both in the upper (8 Hz) and lower (12 Hz) bands, increased after 200 ms and reached its maximum at around 500 ms. In the literature, a similar time course of induced alpha ERD in response to auditory stimuli has been reported in adults when subjects were required to compare a probe stimulus to a set of previously heard stimuli (Karrasch et al, 1998;Krause et al, 1995Krause et al, , 2001 and when subjects had to detect a target stimulus in an oddball paradigm (Mazaheri and Picton, 2005). These experiments commonly showed that alpha ERD began approximately 300-600 ms after stimulus onset, followed by a peak of ERD around 600-800 ms, and ended around 1500-2000 ms.…”

“…Since we used a passive listening task, the difference between violin and noise sounds cannot be associated with cognitive demands directly. However, it is reasonable to assume that the violin sound is more meaningful compared to white noise, and thereby initiates more complex auditory processing which leads to the pronounced upper alpha ERD as shown in adults (Krause et al, 1995). Thus, we propose that the upper alpha ERD induced by an auditory stimulus can index processes of stimulus feature analysis and registration, as well as subsequent cognitive processes in both children and adults.…”

“…More relevant to the present results, it has been shown that even with the same auditory task design, the type of sound stimulus is an important factor in dissociating these two alpha bands. Using an auditory memory search task for tones and vowels separately, alpha ERD to a probe stimulus was larger for the vowel condition than for the tone condition, especially in the upper alpha frequency band (Krause et al, 1995).…”

Modulation of late alpha band oscillations by feedback in a hypothesis testing paradigm

“…However, task-dependent synchronization of alpha oscillations in association with the regulation of motor behaviour, attention, memory, and lexical processes (e.g. Pfurtscheller et al, 1997;Krause et al, 1995;Hari and Salmelin, 1997;Karrasch et al, 1998) has since been proposed to reflect specific operations of higher brain functioning rather than cortical idling (Kolev et al, 1999.…”

Effects of pulsed and continuous wave 902 MHz mobile phone exposure on brain oscillatory activity during cognitive processing

“…It is now acknowledged that human scalp recorded EEG oscillatory responses at different frequencies can be associated with several distinct aspects of cognitive functioning ranging from stimulus processing, attention, working memory, encoding and recognition to long-term memory [Krause et al, 1995[Krause et al, , 1996Basar et al, 1999Basar et al, , 2001aKlimesch, 1999;Ward, 2003]. For example, responses in the theta frequency band (typically defined as $4-7 Hz) have been related to encoding and recognition of information [for a review see Klimesch, 1999], memory-load demands [Krause et al, 2000c] and lexico-semantic processing [Bastiaansen et al, 2005].…”