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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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Correlations between correct response rate (ordinate) and a spectral amplitude measure reflecting the strength of differentiation between the 2 sample stimuli (abscissa) for the entire subject sample across both groups (N = 28). The differentiation measure was computed as the difference between the stimulus-specific GBA spectral amplitude changes at the 2 sensors where these effects were localized during the final 100 ms of the delay phase.
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fig6: Correlations between correct response rate (ordinate) and a spectral amplitude measure reflecting the strength of differentiation between the 2 sample stimuli (abscissa) for the entire subject sample across both groups (N = 28). The differentiation measure was computed as the difference between the stimulus-specific GBA spectral amplitude changes at the 2 sensors where these effects were localized during the final 100 ms of the delay phase.

Mentions: To explore a possible relationship between the stimulus-specific GBA components and task performance, we calculated an index of strength of representation of the 2 S1 stimuli across groups. First, for each subject the spectral amplitude differences in response to the 15° minus the 45° sample stimulus were calculated at the more medial and the more lateral parieto-occipital sensors, respectively. Second, the difference was computed between these amplitude difference values at the medial minus the lateral sensor. The resulting score thus reflected the degree to which oscillatory signals differentiated between the 2 stimuli. Positive values indicated a “consistent” differentiation with larger amplitudes to the preferred stimulus (in the sense of the initial statistical parametric mapping), whereas negative values stood for an “inconsistent” differentiation with larger amplitudes to the nonpreferred sound. This score was then correlated with correct response rate, that is, the combined proportion of hits and correct rejections. As subjects had to respond to 1 type of S1–S2 comparison only (either to matches or nonmatches), a distinction between both types of responses was not possible. Across groups, a significant positive correlation of r = 0.47 (P = 0.012) was observed between correct response rate and the averaged differentiation score for the final 100 ms of the delay phase only (Fig. 6), that is, a more pronounced differentiation was associated with better performance. In contrast, there was no significant correlation between GBA amplitude and reaction time during this time window (r = 0.07).


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)

Correlations between correct response rate (ordinate) and a spectral amplitude measure reflecting the strength of differentiation between the 2 sample stimuli (abscissa) for the entire subject sample across both groups (N = 28). The differentiation measure was computed as the difference between the stimulus-specific GBA spectral amplitude changes at the 2 sensors where these effects were localized during the final 100 ms of the delay phase.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig6: Correlations between correct response rate (ordinate) and a spectral amplitude measure reflecting the strength of differentiation between the 2 sample stimuli (abscissa) for the entire subject sample across both groups (N = 28). The differentiation measure was computed as the difference between the stimulus-specific GBA spectral amplitude changes at the 2 sensors where these effects were localized during the final 100 ms of the delay phase.
Mentions: To explore a possible relationship between the stimulus-specific GBA components and task performance, we calculated an index of strength of representation of the 2 S1 stimuli across groups. First, for each subject the spectral amplitude differences in response to the 15° minus the 45° sample stimulus were calculated at the more medial and the more lateral parieto-occipital sensors, respectively. Second, the difference was computed between these amplitude difference values at the medial minus the lateral sensor. The resulting score thus reflected the degree to which oscillatory signals differentiated between the 2 stimuli. Positive values indicated a “consistent” differentiation with larger amplitudes to the preferred stimulus (in the sense of the initial statistical parametric mapping), whereas negative values stood for an “inconsistent” differentiation with larger amplitudes to the nonpreferred sound. This score was then correlated with correct response rate, that is, the combined proportion of hits and correct rejections. As subjects had to respond to 1 type of S1–S2 comparison only (either to matches or nonmatches), a distinction between both types of responses was not possible. Across groups, a significant positive correlation of r = 0.47 (P = 0.012) was observed between correct response rate and the averaged differentiation score for the final 100 ms of the delay phase only (Fig. 6), that is, a more pronounced differentiation was associated with better performance. In contrast, there was no significant correlation between GBA amplitude and reaction time during this time window (r = 0.07).

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