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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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Related in: MedlinePlus

Time-frequency plots depicting the spectral amplitude values and statistical strength (top and bottom panels, respectively) of differences between 15° and 45° sample stimuli (warm colors: relative increases for S1 at 15°, cold colors: relative increases for S1 at 45°) for both groups. Data are shown for the interval from the onset of S1 to the offset of S2 and for frequencies between 40 and 90 Hz. The top left graphs in each panel depict activity differences at the more medial posterior sensor for group R (med., symbolized by the largest circle in the top left map of Fig. 3), the bottom left graphs show activity differences for the more lateral parieto-occipital sensor for group R (lat., symbolized by the largest circle in the bottom left map of Fig. 3). The plots in the left half of the figure show the corresponding sensors for group L. Effects that met the statistical significance criteria described in the Materials and Methods are marked with white rectangles.
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fig4: Time-frequency plots depicting the spectral amplitude values and statistical strength (top and bottom panels, respectively) of differences between 15° and 45° sample stimuli (warm colors: relative increases for S1 at 15°, cold colors: relative increases for S1 at 45°) for both groups. Data are shown for the interval from the onset of S1 to the offset of S2 and for frequencies between 40 and 90 Hz. The top left graphs in each panel depict activity differences at the more medial posterior sensor for group R (med., symbolized by the largest circle in the top left map of Fig. 3), the bottom left graphs show activity differences for the more lateral parieto-occipital sensor for group R (lat., symbolized by the largest circle in the bottom left map of Fig. 3). The plots in the left half of the figure show the corresponding sensors for group L. Effects that met the statistical significance criteria described in the Materials and Methods are marked with white rectangles.

Mentions: The results of frequency analysis for the comparison of the 2 S1 stimuli during the time window of 0.6–1.2 s after trial onset in each group are depicted in Figure 3. In group R, right-lateralized sample stimuli at 15° deviation from the midsagittal plane were associated with a relative enhancement of GBA at ∼68 Hz at a left parieto-occipital sensor (MLP52). For right-lateralized sample sounds at 45°, higher spectral amplitude was observed at ∼72 Hz at a slightly more lateral parieto-occipital sensor (MLP53). These effects met the criterion of tcorr = 3.41 for 2 consecutive frequency bins in the frequency range of 55–80 Hz. In group L, left-lateralized S1 stimuli at 15° were accompanied by a relative enhancement of GBA at ∼59 Hz at a right parieto-occipital sensor (MRP53). Left-lateralized sample sounds at 45° gave rise to higher spectral amplitude at ∼62 Hz at a more lateral parieto-occipital sensor (MRO13). These effects met the criterion of tcorr = 3.0 for 2 consecutive frequency bins in the frequency range of 58–65 Hz. To explore the time course and topography of these spectral amplitude differences, the data records were Gabor filtered (filter width: ±1.5 Hz around center frequency) in frequency ranges with center frequencies of 68 and 72 Hz for group R, and 59 and 62 Hz for group L, respectively. The time courses of the GBA differences between sample sounds at 15° and 45° in these frequency ranges are depicted as statistical time-frequency plots in Figure 4 and as spectral amplitude and statistical time curves for the filtered signals in Figure 5.


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)

Time-frequency plots depicting the spectral amplitude values and statistical strength (top and bottom panels, respectively) of differences between 15° and 45° sample stimuli (warm colors: relative increases for S1 at 15°, cold colors: relative increases for S1 at 45°) for both groups. Data are shown for the interval from the onset of S1 to the offset of S2 and for frequencies between 40 and 90 Hz. The top left graphs in each panel depict activity differences at the more medial posterior sensor for group R (med., symbolized by the largest circle in the top left map of Fig. 3), the bottom left graphs show activity differences for the more lateral parieto-occipital sensor for group R (lat., symbolized by the largest circle in the bottom left map of Fig. 3). The plots in the left half of the figure show the corresponding sensors for group L. Effects that met the statistical significance criteria described in the Materials and Methods are marked with white rectangles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig4: Time-frequency plots depicting the spectral amplitude values and statistical strength (top and bottom panels, respectively) of differences between 15° and 45° sample stimuli (warm colors: relative increases for S1 at 15°, cold colors: relative increases for S1 at 45°) for both groups. Data are shown for the interval from the onset of S1 to the offset of S2 and for frequencies between 40 and 90 Hz. The top left graphs in each panel depict activity differences at the more medial posterior sensor for group R (med., symbolized by the largest circle in the top left map of Fig. 3), the bottom left graphs show activity differences for the more lateral parieto-occipital sensor for group R (lat., symbolized by the largest circle in the bottom left map of Fig. 3). The plots in the left half of the figure show the corresponding sensors for group L. Effects that met the statistical significance criteria described in the Materials and Methods are marked with white rectangles.
Mentions: The results of frequency analysis for the comparison of the 2 S1 stimuli during the time window of 0.6–1.2 s after trial onset in each group are depicted in Figure 3. In group R, right-lateralized sample stimuli at 15° deviation from the midsagittal plane were associated with a relative enhancement of GBA at ∼68 Hz at a left parieto-occipital sensor (MLP52). For right-lateralized sample sounds at 45°, higher spectral amplitude was observed at ∼72 Hz at a slightly more lateral parieto-occipital sensor (MLP53). These effects met the criterion of tcorr = 3.41 for 2 consecutive frequency bins in the frequency range of 55–80 Hz. In group L, left-lateralized S1 stimuli at 15° were accompanied by a relative enhancement of GBA at ∼59 Hz at a right parieto-occipital sensor (MRP53). Left-lateralized sample sounds at 45° gave rise to higher spectral amplitude at ∼62 Hz at a more lateral parieto-occipital sensor (MRO13). These effects met the criterion of tcorr = 3.0 for 2 consecutive frequency bins in the frequency range of 58–65 Hz. To explore the time course and topography of these spectral amplitude differences, the data records were Gabor filtered (filter width: ±1.5 Hz around center frequency) in frequency ranges with center frequencies of 68 and 72 Hz for group R, and 59 and 62 Hz for group L, respectively. The time courses of the GBA differences between sample sounds at 15° and 45° in these frequency ranges are depicted as statistical time-frequency plots in Figure 4 and as spectral amplitude and statistical time curves for the filtered signals in Figure 5.

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
Related in: MedlinePlus