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Long Term Memory for Noise: Evidence of Robust Encoding of Very Short Temporal Acoustic Patterns

View Article: PubMed Central - PubMed

ABSTRACT

Recent research has demonstrated that humans are able to implicitly encode and retain repeating patterns in meaningless auditory noise. Our study aimed at testing the robustness of long-term implicit recognition memory for these learned patterns. Participants performed a cyclic/non-cyclic discrimination task, during which they were presented with either 1-s cyclic noises (CNs) (the two halves of the noise were identical) or 1-s plain random noises (Ns). Among CNs and Ns presented once, target CNs were implicitly presented multiple times within a block, and implicit recognition of these target CNs was tested 4 weeks later using a similar cyclic/non-cyclic discrimination task. Furthermore, robustness of implicit recognition memory was tested by presenting participants with looped (shifting the origin) and scrambled (chopping sounds into 10− and 20-ms bits before shuffling) versions of the target CNs. We found that participants had robust implicit recognition memory for learned noise patterns after 4 weeks, right from the first presentation. Additionally, this memory was remarkably resistant to acoustic transformations, such as looping and scrambling of the sounds. Finally, implicit recognition of sounds was dependent on participant's discrimination performance during learning. Our findings suggest that meaningless temporal features as short as 10 ms can be implicitly stored in long-term auditory memory. Moreover, successful encoding and storage of such fine features may vary between participants, possibly depending on individual attention and auditory discrimination abilities.

Meaningless auditory patterns could be implicitly encoded and stored in long-term memory.

Acoustic transformations of learned meaningless patterns could be implicitly recognized after 4 weeks.

Implicit long-term memories can be formed for meaningless auditory features as short as 10 ms.

Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

No MeSH data available.


Related in: MedlinePlus

Changes in frequency features—in low, mid and high frequency bands—of a CN due to looping and scrambling with increasing bin sizes. The maximal frequency on the X axis corresponds to the Nyquist frequency (22,050 Hz) and the spectrum amplitude difference between original and looped/scrambled versions of a CN is plotted on the Y axis. With decreasing bin size, the difference between the resulting scrambled sound and the original sound increases, leading to greater difference in amplitude spectrum from the original, across all the frequency bands.
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Figure 2: Changes in frequency features—in low, mid and high frequency bands—of a CN due to looping and scrambling with increasing bin sizes. The maximal frequency on the X axis corresponds to the Nyquist frequency (22,050 Hz) and the spectrum amplitude difference between original and looped/scrambled versions of a CN is plotted on the Y axis. With decreasing bin size, the difference between the resulting scrambled sound and the original sound increases, leading to greater difference in amplitude spectrum from the original, across all the frequency bands.

Mentions: To further understand how scrambling and looping affect the acoustic properties of a CN, we calculated Fourier transforms of an exemplar CN and its variants. Variants were created similar to the looped and scrambled sounds. Bin sizes of 250, 100, 50, 20, and 10 ms were used to create 5 distinct scrambled versions of the exemplar CN. The difference in amplitude between spectra of these variants and spectrum of the original CN is plotted in Figure 2, with frequency bins (10 samples/bin) ranging from lower bands to higher bands on the X axis. While looping and 250-ms scrambling does not change the amplitude spectrum at any frequency, scrambling using 100-ms or smaller bins affects the amplitude spectrum at all frequencies.


Long Term Memory for Noise: Evidence of Robust Encoding of Very Short Temporal Acoustic Patterns
Changes in frequency features—in low, mid and high frequency bands—of a CN due to looping and scrambling with increasing bin sizes. The maximal frequency on the X axis corresponds to the Nyquist frequency (22,050 Hz) and the spectrum amplitude difference between original and looped/scrambled versions of a CN is plotted on the Y axis. With decreasing bin size, the difference between the resulting scrambled sound and the original sound increases, leading to greater difference in amplitude spectrum from the original, across all the frequency bands.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121232&req=5

Figure 2: Changes in frequency features—in low, mid and high frequency bands—of a CN due to looping and scrambling with increasing bin sizes. The maximal frequency on the X axis corresponds to the Nyquist frequency (22,050 Hz) and the spectrum amplitude difference between original and looped/scrambled versions of a CN is plotted on the Y axis. With decreasing bin size, the difference between the resulting scrambled sound and the original sound increases, leading to greater difference in amplitude spectrum from the original, across all the frequency bands.
Mentions: To further understand how scrambling and looping affect the acoustic properties of a CN, we calculated Fourier transforms of an exemplar CN and its variants. Variants were created similar to the looped and scrambled sounds. Bin sizes of 250, 100, 50, 20, and 10 ms were used to create 5 distinct scrambled versions of the exemplar CN. The difference in amplitude between spectra of these variants and spectrum of the original CN is plotted in Figure 2, with frequency bins (10 samples/bin) ranging from lower bands to higher bands on the X axis. While looping and 250-ms scrambling does not change the amplitude spectrum at any frequency, scrambling using 100-ms or smaller bins affects the amplitude spectrum at all frequencies.

View Article: PubMed Central - PubMed

ABSTRACT

Recent research has demonstrated that humans are able to implicitly encode and retain repeating patterns in meaningless auditory noise. Our study aimed at testing the robustness of long-term implicit recognition memory for these learned patterns. Participants performed a cyclic/non-cyclic discrimination task, during which they were presented with either 1-s cyclic noises (CNs) (the two halves of the noise were identical) or 1-s plain random noises (Ns). Among CNs and Ns presented once, target CNs were implicitly presented multiple times within a block, and implicit recognition of these target CNs was tested 4 weeks later using a similar cyclic/non-cyclic discrimination task. Furthermore, robustness of implicit recognition memory was tested by presenting participants with looped (shifting the origin) and scrambled (chopping sounds into 10− and 20-ms bits before shuffling) versions of the target CNs. We found that participants had robust implicit recognition memory for learned noise patterns after 4 weeks, right from the first presentation. Additionally, this memory was remarkably resistant to acoustic transformations, such as looping and scrambling of the sounds. Finally, implicit recognition of sounds was dependent on participant's discrimination performance during learning. Our findings suggest that meaningless temporal features as short as 10 ms can be implicitly stored in long-term auditory memory. Moreover, successful encoding and storage of such fine features may vary between participants, possibly depending on individual attention and auditory discrimination abilities.

Meaningless auditory patterns could be implicitly encoded and stored in long-term memory.

Acoustic transformations of learned meaningless patterns could be implicitly recognized after 4 weeks.

Implicit long-term memories can be formed for meaningless auditory features as short as 10 ms.

Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

No MeSH data available.


Related in: MedlinePlus