Limits...
Averaging, not internal noise, limits the development of coherent motion processing.

Manning C, Dakin SC, Tibber MS, Pellicano E - Dev Cogn Neurosci (2014)

Bottom Line: To this end, we presented equivalent noise direction discrimination tasks and motion coherence tasks at both slow (1.5°/s) and fast (6°/s) speeds to children aged 5, 7, 9 and 11 years, and adults.We show that, as children get older, their levels of internal noise reduce, and they are able to average across more local motion estimates.Our results suggest that the development of coherent motion sensitivity is primarily limited by developmental changes within brain regions involved in integrating motion signals (e.g., MT/V5).

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Autism and Education (CRAE), Institute of Education, University of London, 55-59 Gordon Square, Institute of Education, London WC1H 0NU, UK. Electronic address: c.manning@ioe.ac.uk.

Show MeSH

Related in: MedlinePlus

(A) Equivalent noise functions relating direction discrimination thresholds to the standard deviation of dot directions (i.e., external noise). Lower sampling is represented by an equivalent noise function that is shifted vertically upwards, whilst higher levels of internal noise require more external noise to be added before thresholds increase. (B) The black circles and curve represent the standard equivalent noise paradigm where direction discrimination thresholds are measured at multiple levels of external noise. Large standard deviations of dot directions reflect high external noise in the stimulus. The grey circles and curve are derived using a rapid version of the equivalent noise paradigm, which measures performance at two maximally informative noise levels. In the ‘no noise’ condition, there is no external noise (i.e., the standard deviation of dot directions is 0°) and the threshold is taken as the finest direction discrimination possible. In the ‘high noise’ condition, we measure the maximum noise that can be tolerated when the observer is judging if the pattern is moving either +45° or −45° of vertical. (C) Example of a stimulus in the ‘low noise’ condition, where the mean direction of dots is +4°, and the standard deviation of directions is 0°. (D) Example of a stimulus in the ‘high noise’ condition, where the mean direction of dots is +45°, and the standard deviation of dot directions is 45°. Arrows are provided for illustrative purposes only, to represent the direction of motion.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4256063&req=5

fig0005: (A) Equivalent noise functions relating direction discrimination thresholds to the standard deviation of dot directions (i.e., external noise). Lower sampling is represented by an equivalent noise function that is shifted vertically upwards, whilst higher levels of internal noise require more external noise to be added before thresholds increase. (B) The black circles and curve represent the standard equivalent noise paradigm where direction discrimination thresholds are measured at multiple levels of external noise. Large standard deviations of dot directions reflect high external noise in the stimulus. The grey circles and curve are derived using a rapid version of the equivalent noise paradigm, which measures performance at two maximally informative noise levels. In the ‘no noise’ condition, there is no external noise (i.e., the standard deviation of dot directions is 0°) and the threshold is taken as the finest direction discrimination possible. In the ‘high noise’ condition, we measure the maximum noise that can be tolerated when the observer is judging if the pattern is moving either +45° or −45° of vertical. (C) Example of a stimulus in the ‘low noise’ condition, where the mean direction of dots is +4°, and the standard deviation of directions is 0°. (D) Example of a stimulus in the ‘high noise’ condition, where the mean direction of dots is +45°, and the standard deviation of dot directions is 45°. Arrows are provided for illustrative purposes only, to represent the direction of motion.

Mentions: The traditional motion coherence paradigm cannot distinguish between local and global limits to motion perception and has hence obscured our understanding of what limits global motion processing during development (and in a variety of neurodevelopmental disorders; Dakin and Frith, 2005). To address this issue, the current study used the equivalent noise paradigm (Barlow, 1956; Pelli, 1990) to determine whether local or global processing limits motion coherence sensitivity in development. The equivalent noise paradigm is based on comparing human performance to that of an ideal observer that is limited both by additive internal noise and by how completely it samples the information available from the stimulus (Pelli, 1990). When equivalent noise analysis is applied to direction discrimination (Dakin et al., 2005), internal noise maps onto the precision with which individual motion directions are estimated and sampling represents an estimate of the effective number of local motion directions that are globally pooled (or averaged). Whereas motion coherence stimuli contain both signal dots and randomly moving noise dots, equivalent noise stimuli contain dots whose directions (on any one trial) are sampled from a single Gaussian distribution (Dakin et al., 2005). The standard deviation of this distribution is varied across conditions, in order to manipulate the level of stimulus variability (or ‘external noise’; see Fig. 1A).


Averaging, not internal noise, limits the development of coherent motion processing.

Manning C, Dakin SC, Tibber MS, Pellicano E - Dev Cogn Neurosci (2014)

(A) Equivalent noise functions relating direction discrimination thresholds to the standard deviation of dot directions (i.e., external noise). Lower sampling is represented by an equivalent noise function that is shifted vertically upwards, whilst higher levels of internal noise require more external noise to be added before thresholds increase. (B) The black circles and curve represent the standard equivalent noise paradigm where direction discrimination thresholds are measured at multiple levels of external noise. Large standard deviations of dot directions reflect high external noise in the stimulus. The grey circles and curve are derived using a rapid version of the equivalent noise paradigm, which measures performance at two maximally informative noise levels. In the ‘no noise’ condition, there is no external noise (i.e., the standard deviation of dot directions is 0°) and the threshold is taken as the finest direction discrimination possible. In the ‘high noise’ condition, we measure the maximum noise that can be tolerated when the observer is judging if the pattern is moving either +45° or −45° of vertical. (C) Example of a stimulus in the ‘low noise’ condition, where the mean direction of dots is +4°, and the standard deviation of directions is 0°. (D) Example of a stimulus in the ‘high noise’ condition, where the mean direction of dots is +45°, and the standard deviation of dot directions is 45°. Arrows are provided for illustrative purposes only, to represent the direction of motion.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4256063&req=5

fig0005: (A) Equivalent noise functions relating direction discrimination thresholds to the standard deviation of dot directions (i.e., external noise). Lower sampling is represented by an equivalent noise function that is shifted vertically upwards, whilst higher levels of internal noise require more external noise to be added before thresholds increase. (B) The black circles and curve represent the standard equivalent noise paradigm where direction discrimination thresholds are measured at multiple levels of external noise. Large standard deviations of dot directions reflect high external noise in the stimulus. The grey circles and curve are derived using a rapid version of the equivalent noise paradigm, which measures performance at two maximally informative noise levels. In the ‘no noise’ condition, there is no external noise (i.e., the standard deviation of dot directions is 0°) and the threshold is taken as the finest direction discrimination possible. In the ‘high noise’ condition, we measure the maximum noise that can be tolerated when the observer is judging if the pattern is moving either +45° or −45° of vertical. (C) Example of a stimulus in the ‘low noise’ condition, where the mean direction of dots is +4°, and the standard deviation of directions is 0°. (D) Example of a stimulus in the ‘high noise’ condition, where the mean direction of dots is +45°, and the standard deviation of dot directions is 45°. Arrows are provided for illustrative purposes only, to represent the direction of motion.
Mentions: The traditional motion coherence paradigm cannot distinguish between local and global limits to motion perception and has hence obscured our understanding of what limits global motion processing during development (and in a variety of neurodevelopmental disorders; Dakin and Frith, 2005). To address this issue, the current study used the equivalent noise paradigm (Barlow, 1956; Pelli, 1990) to determine whether local or global processing limits motion coherence sensitivity in development. The equivalent noise paradigm is based on comparing human performance to that of an ideal observer that is limited both by additive internal noise and by how completely it samples the information available from the stimulus (Pelli, 1990). When equivalent noise analysis is applied to direction discrimination (Dakin et al., 2005), internal noise maps onto the precision with which individual motion directions are estimated and sampling represents an estimate of the effective number of local motion directions that are globally pooled (or averaged). Whereas motion coherence stimuli contain both signal dots and randomly moving noise dots, equivalent noise stimuli contain dots whose directions (on any one trial) are sampled from a single Gaussian distribution (Dakin et al., 2005). The standard deviation of this distribution is varied across conditions, in order to manipulate the level of stimulus variability (or ‘external noise’; see Fig. 1A).

Bottom Line: To this end, we presented equivalent noise direction discrimination tasks and motion coherence tasks at both slow (1.5°/s) and fast (6°/s) speeds to children aged 5, 7, 9 and 11 years, and adults.We show that, as children get older, their levels of internal noise reduce, and they are able to average across more local motion estimates.Our results suggest that the development of coherent motion sensitivity is primarily limited by developmental changes within brain regions involved in integrating motion signals (e.g., MT/V5).

View Article: PubMed Central - PubMed

Affiliation: Centre for Research in Autism and Education (CRAE), Institute of Education, University of London, 55-59 Gordon Square, Institute of Education, London WC1H 0NU, UK. Electronic address: c.manning@ioe.ac.uk.

Show MeSH
Related in: MedlinePlus