Dataset Information

The effect of parametric stimulus size variation on individual face discrimination indexed by fast periodic visual stimulation.

ABSTRACT:

Background

The human brain is frequently exposed to individual faces across a wide range of different apparent sizes, often seen simultaneously (e.g., when facing a crowd). Here we used a sensitive and objective fast periodic visual stimulation approach while recording scalp electroencephalogram (EEG) to test the effect of size variation on neural responses reflecting individual face discrimination.

Methods

EEG was recorded in ten observers presented with the same face identity at a fixed rate (5.88 Hz, frequency F) and different oddball face identities appearing every five faces (F/5, i.e., 1.18 Hz). Stimulus size was either constant (6.5 × 4 degrees of visual angle) or changed randomly at each stimulation cycle, by 2:1 ratio increasing values from 10% to 80% size variation in four conditions. Absolute stimulus size remained constant across conditions.

Results

The base rate 5.88 Hz EEG response increased with image size variation, particularly over the right occipito-temporal cortex. In contrast, size variation decreased the oddball response marking individual face discrimination over the right occipito-temporal cortex. At constant stimulus size, the F/5 change of identity generated an early (about 100 ms) oddball response reflecting individual face discrimination based on image-based cues. This early component disappeared with a relatively small size variation (i.e., 20%), leaving a robust high-level index of individual face discrimination.

Conclusions

Stimulus size variation is an important manipulation to isolate the contribution of high-level visual processes to individual face discrimination. Nevertheless, even for relatively small stimuli, high-level individual face discrimination processes in the right occipito-temporal cortex remain sensitive to stimulus size variation.

SUBMITTER: Dzhelyova M

PROVIDER: S-EPMC4112211 | biostudies-literature | 2014 Jul

REPOSITORIES: biostudies-literature

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Publications

The effect of parametric stimulus size variation on individual face discrimination indexed by fast periodic visual stimulation.

Dzhelyova Milena M Rossion Bruno B

BMC neuroscience 20140719

<h4>Background</h4>The human brain is frequently exposed to individual faces across a wide range of different apparent sizes, often seen simultaneously (e.g., when facing a crowd). Here we used a sensitive and objective fast periodic visual stimulation approach while recording scalp electroencephalogram (EEG) to test the effect of size variation on neural responses reflecting individual face discrimination.<h4>Methods</h4>EEG was recorded in ten observers presented with the same face identity at ...[more]

PMID: 25038784

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Project description:The present study combined magnetoencephalography (MEG) recordings with fast periodic visual stimulation (FPVS) to investigate automatic neural responses to morphemes in developing and skilled readers. Native English-speaking children (N = 17, grade 5-6) and adults (N = 28) were presented with rapid streams of base stimuli (6 Hz) interleaved periodically with oddballs (i.e., every fifth item, oddball stimulation frequency: 1.2 Hz). In a manipulation-check condition, tapping into word recognition, oddballs featured familiar words (e.g., roll) embedded in a stream of consonant strings (e.g., ktlq). In the experimental conditions, the contrast between oddball and base stimuli was manipulated in order to probe selective stem and suffix identification in morphologically structured pseudowords (e.g., stem + suffix pseudowords such as softity embedded in nonstem + suffix pseudowords such as trumess). Neural responses at the oddball frequency and harmonics were analyzed at the sensor level using non-parametric cluster-based permutation tests. As expected, results in the manipulation-check condition revealed a word-selective response reflected by a predominantly left-lateralized cluster that emerged over temporal, parietal, and occipital sensors in both children and adults. However, across the experimental conditions, results yielded a differential pattern of oddball responses in developing and skilled readers. Children displayed a significant response that emerged in a mostly central occipital cluster for the condition tracking stem identification in the presence of suffixes (e.g., softity vs. trumess). In contrast, adult participants showed a significant response that emerged in a cluster located in central and left occipital sensors for the condition tracking suffix identification in the presence of stems (e.g., softity vs. stopust). The present results suggest that while the morpheme identification system in Grade 5-6 children is not yet adult-like, it is sufficiently mature to automatically analyze the morphemic structure of novel letter strings. These findings are discussed in the context of theoretical accounts of morphological processing across reading development.

Dataset Information

The effect of parametric stimulus size variation on individual face discrimination indexed by fast periodic visual stimulation.

Background

Methods

Results

Conclusions

Publications

The effect of parametric stimulus size variation on individual face discrimination indexed by fast periodic visual stimulation.

Similar Datasets

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