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Distinct gamma-band components reflect the short-term memory maintenance of different sound lateralization angles.

Kaiser J, Heidegger T, Wibral M, Altmann CF, Lutzenberger W - Cereb. Cortex (2008)

Bottom Line: Distinct GBA components were found for each sample stimulus in different sensors over parieto-occipital cortex contralateral to the side of stimulation peaking during the middle 200-300 ms of the delay phase.The differentiation between "preferred" and "nonpreferred" stimuli during the final 100 ms of the delay phase correlated with task performance.These findings suggest that the observed GBA components reflect the activity of distinct networks tuned to spatial sound features which contribute to the maintenance of task-relevant information in short-term memory.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Psychology, Johann Wolfgang Goethe-University, 60528 Frankfurt am Main, Germany. j.kaiser@med.uni-frankfurt.de

ABSTRACT
Oscillatory activity in human electro- or magnetoencephalogram has been related to cortical stimulus representations and their modulation by cognitive processes. Whereas previous work has focused on gamma-band activity (GBA) during attention or maintenance of representations, there is little evidence for GBA reflecting individual stimulus representations. The present study aimed at identifying stimulus-specific GBA components during auditory spatial short-term memory. A total of 28 adults were assigned to 1 of 2 groups who were presented with only right- or left-lateralized sounds, respectively. In each group, 2 sample stimuli were used which differed in their lateralization angles (15 degrees or 45 degrees) with respect to the midsagittal plane. Statistical probability mapping served to identify spectral amplitude differences between 15 degrees versus 45 degrees stimuli. Distinct GBA components were found for each sample stimulus in different sensors over parieto-occipital cortex contralateral to the side of stimulation peaking during the middle 200-300 ms of the delay phase. The differentiation between "preferred" and "nonpreferred" stimuli during the final 100 ms of the delay phase correlated with task performance. These findings suggest that the observed GBA components reflect the activity of distinct networks tuned to spatial sound features which contribute to the maintenance of task-relevant information in short-term memory.

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Trial structure of the task. Low-pass filtered noise (pre-S1) and the 200-ms presentation of the sample stimulus (S1) were followed by a delay phase of 800 ms midline noise. Then a probe stimulus (S2) appeared for 200 ms. Subjects had to compare the sound lateralization angle of S1 and S2. Arrows symbolize the lateralization angles of S1 and S2. The light gray horizontal bar above the symbol for the delay phase shows the latency window for spectral analysis (600–1200 ms after trial onset).
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fig1: Trial structure of the task. Low-pass filtered noise (pre-S1) and the 200-ms presentation of the sample stimulus (S1) were followed by a delay phase of 800 ms midline noise. Then a probe stimulus (S2) appeared for 200 ms. Subjects had to compare the sound lateralization angle of S1 and S2. Arrows symbolize the lateralization angles of S1 and S2. The light gray horizontal bar above the symbol for the delay phase shows the latency window for spectral analysis (600–1200 ms after trial onset).

Mentions: The trial structure of the task is depicted in Figure 1. The onset of the trial was signaled by a soft low-pass filtered midline background noise (at 6 kHz: −24 dB/octave) presented for 300 ms. Then a lateralized noise S1 (sample stimulus) was presented for 200 ms. The intensity of the background sound and the sample stimuli measured with a Reed 120-0014 sound level meter (TechniCal Systems Inc., Hamilton, Canada) amounted to 85 dB(A) and 98 dB(A), respectively. The intensity of the sample sounds was thus in the range that has been shown to elicit pronounced evoked gamma responses to sinusoidal tones in EEG (Schadow et al. 2007). Lateralized sounds were generated by convolution with head-related transfer functions (Gardner and Martin 1995; http://sound.media.mit.edu/KEMAR.html) yielding the impression of lateralized sounds in extrapersonal space. This is achieved by introducing both intrapersonal amplitude and time differences and by simulating the localization-dependent filtering properties of head and outer ears. During the following delay phase the background noise was presented again for 800 ms. This was followed by a second task-relevant lateralized noise S2 (probe stimulus).


Distinct gamma-band components reflect the short-term memory maintenance of different sound lateralization angles.

Kaiser J, Heidegger T, Wibral M, Altmann CF, Lutzenberger W - Cereb. Cortex (2008)

Trial structure of the task. Low-pass filtered noise (pre-S1) and the 200-ms presentation of the sample stimulus (S1) were followed by a delay phase of 800 ms midline noise. Then a probe stimulus (S2) appeared for 200 ms. Subjects had to compare the sound lateralization angle of S1 and S2. Arrows symbolize the lateralization angles of S1 and S2. The light gray horizontal bar above the symbol for the delay phase shows the latency window for spectral analysis (600–1200 ms after trial onset).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2536701&req=5

fig1: Trial structure of the task. Low-pass filtered noise (pre-S1) and the 200-ms presentation of the sample stimulus (S1) were followed by a delay phase of 800 ms midline noise. Then a probe stimulus (S2) appeared for 200 ms. Subjects had to compare the sound lateralization angle of S1 and S2. Arrows symbolize the lateralization angles of S1 and S2. The light gray horizontal bar above the symbol for the delay phase shows the latency window for spectral analysis (600–1200 ms after trial onset).
Mentions: The trial structure of the task is depicted in Figure 1. The onset of the trial was signaled by a soft low-pass filtered midline background noise (at 6 kHz: −24 dB/octave) presented for 300 ms. Then a lateralized noise S1 (sample stimulus) was presented for 200 ms. The intensity of the background sound and the sample stimuli measured with a Reed 120-0014 sound level meter (TechniCal Systems Inc., Hamilton, Canada) amounted to 85 dB(A) and 98 dB(A), respectively. The intensity of the sample sounds was thus in the range that has been shown to elicit pronounced evoked gamma responses to sinusoidal tones in EEG (Schadow et al. 2007). Lateralized sounds were generated by convolution with head-related transfer functions (Gardner and Martin 1995; http://sound.media.mit.edu/KEMAR.html) yielding the impression of lateralized sounds in extrapersonal space. This is achieved by introducing both intrapersonal amplitude and time differences and by simulating the localization-dependent filtering properties of head and outer ears. During the following delay phase the background noise was presented again for 800 ms. This was followed by a second task-relevant lateralized noise S2 (probe stimulus).

Bottom Line: Distinct GBA components were found for each sample stimulus in different sensors over parieto-occipital cortex contralateral to the side of stimulation peaking during the middle 200-300 ms of the delay phase.The differentiation between "preferred" and "nonpreferred" stimuli during the final 100 ms of the delay phase correlated with task performance.These findings suggest that the observed GBA components reflect the activity of distinct networks tuned to spatial sound features which contribute to the maintenance of task-relevant information in short-term memory.

View Article: PubMed Central - PubMed

Affiliation: Institute of Medical Psychology, Johann Wolfgang Goethe-University, 60528 Frankfurt am Main, Germany. j.kaiser@med.uni-frankfurt.de

ABSTRACT
Oscillatory activity in human electro- or magnetoencephalogram has been related to cortical stimulus representations and their modulation by cognitive processes. Whereas previous work has focused on gamma-band activity (GBA) during attention or maintenance of representations, there is little evidence for GBA reflecting individual stimulus representations. The present study aimed at identifying stimulus-specific GBA components during auditory spatial short-term memory. A total of 28 adults were assigned to 1 of 2 groups who were presented with only right- or left-lateralized sounds, respectively. In each group, 2 sample stimuli were used which differed in their lateralization angles (15 degrees or 45 degrees) with respect to the midsagittal plane. Statistical probability mapping served to identify spectral amplitude differences between 15 degrees versus 45 degrees stimuli. Distinct GBA components were found for each sample stimulus in different sensors over parieto-occipital cortex contralateral to the side of stimulation peaking during the middle 200-300 ms of the delay phase. The differentiation between "preferred" and "nonpreferred" stimuli during the final 100 ms of the delay phase correlated with task performance. These findings suggest that the observed GBA components reflect the activity of distinct networks tuned to spatial sound features which contribute to the maintenance of task-relevant information in short-term memory.

Show MeSH