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Memory bias in the temporal bisection point.

Levy JM, Namboodiri VM, Hussain Shuler MG - Front Integr Neurosci (2015)

Bottom Line: The ability to time intervals confers organisms, including humans, with many remarkable capabilities.Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point.These results suggest that memory effects should be considered in temporal tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Johns Hopkins University Baltimore, MD, USA.

ABSTRACT
The ability to time intervals confers organisms, including humans, with many remarkable capabilities. A common method for studying interval timing is classification, in which a subject must indicate whether a given probe duration is nearer a previously learned short or long reference interval. This task is designed to reveal the probe duration that is equally likely to be labeled as short or long, known as the temporal bisection point. Studies have found that this bisection point is influenced by a variety of factors including the ratio of the target intervals, the spacing of the probe durations, the modalities of the stimuli, the attentional load, and the inter-trial duration. While several of these factors are thought to be mediated by memory effects, the prototypical classification task affords no opportunity to measure these memory effects directly. Here, we present a novel bisection task, termed the "Bisection by Classification and Production" (BiCaP) task, in which classification trials are interleaved with trials in which subjects must produce either the short or long referents or their midpoint. Using this method, we found a significant correlation between the means of the remembered referents and the bisection points for both classification and production trials. We then cross-validated the bisection points for production and classification trials by showing that they were not statistically differentiable. In addition to these population-level effects, we found within-subject evidence for co-variation across a session between the production bisection points and the means of the remembered referents. Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point. These results suggest that memory effects should be considered in temporal tasks.

No MeSH data available.


Related in: MedlinePlus

Within-subject analysis of memory bias in production. (A) Slope of regression in the 1/5 s referent group between the mean of the produced referents and the averaged midpoint production per block for each subject. Data from 8/10 subjects show positive slopes. The sampling distribution of slopes was calculated by bootstrapping (right). The average slope for the 1/5 s groups (red star) was significantly higher than the  distribution (p < 0.001). (B) This analysis was repeated for the 2/4 s referent group. Data from 9/10 subjects showed positive slopes and the average slope was significantly higher than that of the  distribution (p = 0.007).
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Figure 3: Within-subject analysis of memory bias in production. (A) Slope of regression in the 1/5 s referent group between the mean of the produced referents and the averaged midpoint production per block for each subject. Data from 8/10 subjects show positive slopes. The sampling distribution of slopes was calculated by bootstrapping (right). The average slope for the 1/5 s groups (red star) was significantly higher than the distribution (p < 0.001). (B) This analysis was repeated for the 2/4 s referent group. Data from 9/10 subjects showed positive slopes and the average slope was significantly higher than that of the distribution (p = 0.007).

Mentions: We next sought to determine whether there was evidence for memory bias within data from individual subjects. To do this, we divided each subject’s session into ten equal blocks and asked whether the average midpoint production in a given block correlated with the mean of the produced short and long referent in that block. We found that for the 1/5 s group, data from eight out of ten subjects showed positive slopes of regression (Figure 3A, left). We compared the average slope across subjects (Figure 3A, red star) to that of the distribution of slopes calculated by bootstrapping (see Materials and Methods) and found that it was significantly different (p < 0.001). We repeated this analysis for the 2/4 s group. We found that data from nine out of ten subjects in this group showed positive slopes (Figure 3B, left) and the average slope across subjects was, again, significantly higher that that expected by chance (Figure 3B, red star; p = 0.007). Therefore, we found evidence from individual subjects that memory bias in the production of the referents correlated with the produced bisection point across the session.


Memory bias in the temporal bisection point.

Levy JM, Namboodiri VM, Hussain Shuler MG - Front Integr Neurosci (2015)

Within-subject analysis of memory bias in production. (A) Slope of regression in the 1/5 s referent group between the mean of the produced referents and the averaged midpoint production per block for each subject. Data from 8/10 subjects show positive slopes. The sampling distribution of slopes was calculated by bootstrapping (right). The average slope for the 1/5 s groups (red star) was significantly higher than the  distribution (p < 0.001). (B) This analysis was repeated for the 2/4 s referent group. Data from 9/10 subjects showed positive slopes and the average slope was significantly higher than that of the  distribution (p = 0.007).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493391&req=5

Figure 3: Within-subject analysis of memory bias in production. (A) Slope of regression in the 1/5 s referent group between the mean of the produced referents and the averaged midpoint production per block for each subject. Data from 8/10 subjects show positive slopes. The sampling distribution of slopes was calculated by bootstrapping (right). The average slope for the 1/5 s groups (red star) was significantly higher than the distribution (p < 0.001). (B) This analysis was repeated for the 2/4 s referent group. Data from 9/10 subjects showed positive slopes and the average slope was significantly higher than that of the distribution (p = 0.007).
Mentions: We next sought to determine whether there was evidence for memory bias within data from individual subjects. To do this, we divided each subject’s session into ten equal blocks and asked whether the average midpoint production in a given block correlated with the mean of the produced short and long referent in that block. We found that for the 1/5 s group, data from eight out of ten subjects showed positive slopes of regression (Figure 3A, left). We compared the average slope across subjects (Figure 3A, red star) to that of the distribution of slopes calculated by bootstrapping (see Materials and Methods) and found that it was significantly different (p < 0.001). We repeated this analysis for the 2/4 s group. We found that data from nine out of ten subjects in this group showed positive slopes (Figure 3B, left) and the average slope across subjects was, again, significantly higher that that expected by chance (Figure 3B, red star; p = 0.007). Therefore, we found evidence from individual subjects that memory bias in the production of the referents correlated with the produced bisection point across the session.

Bottom Line: The ability to time intervals confers organisms, including humans, with many remarkable capabilities.Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point.These results suggest that memory effects should be considered in temporal tasks.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, Johns Hopkins University Baltimore, MD, USA.

ABSTRACT
The ability to time intervals confers organisms, including humans, with many remarkable capabilities. A common method for studying interval timing is classification, in which a subject must indicate whether a given probe duration is nearer a previously learned short or long reference interval. This task is designed to reveal the probe duration that is equally likely to be labeled as short or long, known as the temporal bisection point. Studies have found that this bisection point is influenced by a variety of factors including the ratio of the target intervals, the spacing of the probe durations, the modalities of the stimuli, the attentional load, and the inter-trial duration. While several of these factors are thought to be mediated by memory effects, the prototypical classification task affords no opportunity to measure these memory effects directly. Here, we present a novel bisection task, termed the "Bisection by Classification and Production" (BiCaP) task, in which classification trials are interleaved with trials in which subjects must produce either the short or long referents or their midpoint. Using this method, we found a significant correlation between the means of the remembered referents and the bisection points for both classification and production trials. We then cross-validated the bisection points for production and classification trials by showing that they were not statistically differentiable. In addition to these population-level effects, we found within-subject evidence for co-variation across a session between the production bisection points and the means of the remembered referents. Finally, by using two sets of referent durations, we showed that only memory bias-corrected measures were consistent with a previously reported effect in which the ratio of the referents affects the location of the bisection point. These results suggest that memory effects should be considered in temporal tasks.

No MeSH data available.


Related in: MedlinePlus