Maternal cortisol slope at 6 months predicts infant cortisol slope and EEG power at 12 months.

Physiological stress systems and the brain rapidly develop through infancy. While the roles of caregiving and environmental factors have been studied, implications of maternal physiological stress are unclear. We assessed maternal and infant diurnal cortisol when infants were 6 and 12 months. We measured 12-month infant electroencephalography (EEG) 6-9 Hz power during a social interaction. Steeper 6-month maternal slope predicted steeper 12-month infant slope controlling for 6-month infant slope and breastfeeding. Steeper 6-month maternal slope predicted lower 6-9 Hz power. Six-month maternal area under the cuve (AUCg) was unrelated to 12-month infant AUCg and 6-9 Hz power. Psychosocial, caregiving, and breastfeeding variables did not explain results. At 6 months, maternal and infant slopes correlated, as did maternal and infant AUCg. Twelve-month maternal and infant cortisol were unrelated. Results indicate maternal slope is an informative predictor of infant physiology and suggest the importance of maternal physiological stress in this developmental period.

A Within-subjects Experimental Protocol to Assess the Effects of Social Input on Infant EEG.

Despite the importance of social interactions for infant brain development, little research has assessed functional neural activation while infants socially interact. Electroencephalography (EEG) power is an advantageous technique to assess infant functional neural activation. However, many studies record infant EEG only during one baseline condition. This protocol describes a paradigm that is designed to comprehensively assess infant EEG activity in both social and nonsocial contexts as well as tease apart how different types of social inputs differentially relate to infant EEG. The within-subjects paradigm includes four controlled conditions. In the nonsocial condition, infants view objects on computer screens. The joint attention condition involves an experimenter directing the infant's attention to pictures. The joint attention condition includes three types of social input: language, face-to-face interaction, and the presence of joint attention. Differences in infant EEG between the nonsocial and joint attention conditions could be due to any of these three types of input. Therefore, two additional conditions (one with language input while the experimenter is hidden behind a screen and one with face-to-face interaction) were included to assess the driving contextual factors in patterns of infant neural activation. Representative results demonstrate that infant EEG power varied by condition, both overall and differentially by brain region, supporting the functional nature of infant EEG power. This technique is advantageous in that it includes conditions that are clearly social or nonsocial and allows for examination of how specific types of social input relate to EEG power. This paradigm can be used to assess how individual differences in age, affect, socioeconomic status, and parent-infant interaction quality relate to the development of the social brain. Based on the demonstrated functional nature of infant EEG power, future studies should consider the role of EEG recording context and design conditions that are clearly social or nonsocial.

Variation in infant EEG power across social and nonsocial contexts.

To understand the infant social brain, it is critical to observe functional neural activation during social interaction. Yet many infant electroencephalography (EEG) studies on socioemotional development have recorded neural activity only during a baseline state. This study investigated how infant EEG power (4-6Hz and 6-9Hz) varies across social and nonsocial contexts. EEG was recorded in 12-month-olds across controlled conditions to disentangle the neural bases of social interactions. Four conditions-nonsocial, joint attention, language-only, and social engagement-were designed to tease apart how different environmental inputs relate to infant EEG power. We analyzed EEG power in frontal, central, temporal, and parietal regions. During the joint attention condition compared with the other conditions, 4-6Hz frontal, central, and parietal power was lowest, indexing greater neural activation. There was lower 4-6Hz and 6-9Hz power in the temporal region in both the joint attention and social engagement conditions compared with the nonsocial condition. In 6-9Hz, the pattern was consistent with 4-6Hz findings for the frontal region such that 6-9Hz frontal power was lower, indexing greater neural activation, in the joint attention condition compared with the nonsocial condition. There were no differences between conditions in central and parietal regions in 6-9Hz. Findings highlight the methodological importance of recording functional brain activity in multiple controlled contexts to explicate the neural bases of the infant social brain.

Cortical organization of language pathways in children with non-localized cryptogenic epilepsy.

Children with a history of epilepsy are almost six times more likely than their unaffected siblings to be referred for speech or language therapy. However, the abnormalities in neural pathway that cause these delays are poorly understood. We recorded evoked fields using whole-head magnetoencephalography during real and non-word visual and auditory rhyme tasks in 15 children with non-localized cryptogenic epilepsy. Basic phonological and orthographic language skills were assessed using Woodcock-Johnson Test of Achievement subtests. Dynamic statistical parameter mapping was used with individual participant magnetic resonance images. Significant cortical activity was visualized on average and performance weighted maps. For the auditory rhyme tasks, bilateral primary and secondary auditory cortices, the superior temporal sulcus, and insular cortex were activated early with later increases in left hemisphere activity. Visual rhyme tasks evoked early bilateral primary and secondary occipital cortical and angular gyri activity followed by later activation of the planum temporale and supramarginal gyri and the left ventral occipitotemporal area. For the auditory rhyme tasks, performance weighted maps demonstrated that early right hemisphere activation was associated with poorer reading skills while later activity was associated with better reading skills; for the left hemisphere, greater early activation of the secondary auditory cortex, including the planum temporale, was related to better reading skills while relatively later activation of these areas was associated with poorer reading skills. For the visual rhyme tasks, greater activity in the bilateral ventral occipitotemporal and insular areas and angular and supramarginal gyri were associated with better performance. These data suggest that spatiotemporal cortical activation patterns are associated with variations in language performance in non-localized cryptogenic epilepsy.

Is the ability to integrate parts into wholes affected in autism spectrum disorder?

There is considerable debate about whether people with autism spectrum disorder (ASD) are biased toward local information and whether this disrupts their ability to integrate two complex shapes elements into a single figure. Moreover, few have examined the relationship between integration ability and ASD symptom severity. Adolescent/adult males with ASD and age and IQ-matched controls were compared on their performance of a simple silhouette-to-shape matching task and a higher-order shape-integration task. Relative to basic silhouette-to-shape matching, ASD participants were disproportionately slower than controls on shape-integration. Moreover, this relative slowing correlated with increased symptom severity in ASD participants. These findings support the notion that integrating local information is disproportionately more challenging in ASD; this weakness may play a role in ASD symptomatology.

Beyond decoding: adults with dyslexia have trouble forming unified lexical representations across pseudoword learning episodes.

PURPOSE: To examine how adults with dyslexia versus adults with typical reading form lexical representations during pseudoword learning. METHOD: Twenty adults with dyslexia and 20 adults with typical reading learned meanings, spellings, and pronunciations of 16 pictured pseudowords, (half with regular and half with irregular grapheme-phoneme correspondences) presented first in 1 modality (spoken or written) and then the 2nd modality. Dependent measures included picture naming and identification, episodic recognition, a rhyme task, and a categorization task. RESULTS: Adults with dyslexia learned pseudowords more slowly than those with typical reading and were disproportionately poor in learning irregularly spelled pseudowords after changing from written to spoken modality. Adults with dyslexia recognized fewer pseudoword forms than adults with typical reading and verified fewer pseudoword rhymes. Adults with typical reading were more accurate with categorizing regular versus irregular pseudowords. Adults with dyslexia did not show this regularity advantage. CONCLUSIONS: Adults with dyslexia, compared with adults with typical reading, failed to (a) encode and retrieve detailed information about pseudoword forms, (b) efficiently form cross-modal associations between written and spoken encounters with pseudowords, and (c) effectively modify their representations following the change in modality. The authors discuss implications relative to common theories of dyslexia.

Sex differences in the use of delayed semantic context when listening to disrupted speech.

Female as opposed to male listeners were better able to use a delayed informative cue at the end of a long sentence to report an earlier word which was disrupted by noise. Informative (semantically related) or uninformative (semantically unrelated) word cues were presented 2, 6, or 10 words after a target word whose initial phoneme had been replaced with noise. A total of 84 young adults (45 males) listened to each sentence and then repeated it after its offset. The semantic benefit effect (SBE) was the difference in the accuracy of report of the disrupted target word during informative vs. uninformative sentences. Women had significantly higher SBEs than men even though there were no significant sex differences in terms of number of non-target words reported, the effect of distance between the disrupted target word and the informative cue, or kinds of errors generated. We suggest that the superior ability of women to use delayed semantic information to decode an earlier ambiguous speech signal may be linked to women's tendency to engage the hemispheres more bilaterally than men during word processing. Since the maintenance of semantic context under ambiguous conditions demands more right than left hemispheric resources, this may give women an advantage.

A demonstration that task difficulty can confound the interpretation of lateral differences in brain activation between typical and dyslexic readers.

Dyslexic readers (DRs) manifest atypical patterns of brain activity, which may be attributed to aberrant neural connectivity and/or an attempt to activate compensatory pathways. This paper evaluates whether differences in brain activation patterns between DRs and typical readers (TRs) are confounded by task difficulty. Eight DRs and eight TRs matched for age, sex, and nonverbal IQ performed pseudoword rhyming tasks at two levels of difficulty during magnetoencephalography. Task difficulty varied with the number of successive target pseudowords presented before the test pseudoword. Regions of interest were: the temporoparietal area (TPA), the ventral occipital temporal area (VOT), and the inferior frontal gyrus (IFG). Activity was analysed for the 660-ms period after test pseudoword onset. During the discrepant performance condition left hemispheric TPA activation increased across time for TRs, but not DRs, and IFG bihemispheric activation was greater in TRs by the end of the trial. During the equivalent performance condition no group differences in TPA or IFG activation were found. We argue that these results indicate that direct comparison of DR versus TR brain activity is confounded when DRs are more challenged than TRs. This highlights the importance of equating reading group performance during neuroimaging of reading-related tasks.

Laterality of temporoparietal causal connectivity during the prestimulus period correlates with phonological decoding task performance in dyslexic and typical readers.

We examined how effective connectivity into and out of the left and right temporoparietal areas (TPAs) to/from other key cortical areas affected phonological decoding in 7 dyslexic readers (DRs) and 10 typical readers (TRs) who were young adults. Granger causality was used to compute the effective connectivity of the preparatory network 500 ms prior to presentation of nonwords that required phonological decoding. Neuromagnetic activity was analyzed within the low, medium, and high beta and gamma subbands. A mixed-model analysis determined whether connectivity to or from the left and right TPAs differed across connectivity direction (in vs. out), brain areas (right and left inferior frontal and ventral occipital-temporal and the contralateral TPA), reading group (DR vs. TR), and/or task performance. Within the low beta subband, better performance was associated with increased influence of the left TPA on other brain areas across both reading groups and poorer performance was associated with increased influence of the right TPA on other brain areas for DRs only. DRs were also found to have an increase in high gamma connectivity between the left TPA and other brain areas. This study suggests that hierarchal network structure rather than connectivity per se is important in determining phonological decoding performance.

Rapid reacquisition of native phoneme contrasts after disuse: you do not always lose what you do not use.

Infants attune to their birth language during the second half of infancy. However, internationally adopted children are often uniquely required to attune to their birth language, and then reattune to their adoptive language. Children who were adopted from India into America at ages 6-60 months (N = 8) and had minimal further exposure to their birth languages were compared to age-matched American non-adopted controls. Without training, neither group could discriminate a phonemic contrast that occurs in their birth language but not in English. However, after training on the contrast, the adopted group (N = 8) improved significantly and discriminated the contrast more accurately than their non-adopted peers. While English had explicitly replaced the birth language of the adopted sample, traces of early exposure conferred privileges on subsequent learning. These findings are consistent with behavioral and neurophysiological data from animals that have identified some of the mechanisms underlying such a 'retention without further use' phenomenon.

Are women more influenced than men by top-down semantic information when listening to disrupted speech?

Perception is a product of the interaction between bottom-up sensory processing and top-down higher order cognitive activity. For example, when the initial phoneme of a word is obliterated and replaced with noise, listeners hear it as intact provided there is semantic context. We modified this phonemic restoration paradigm by masking (not obliterating) the initial phoneme of a target word and presenting it within a carrier phrase which was informative (I), uninformative (U), or misinformative (M). Bias in favor of top-down context was measured as the extent to which M trials mislead listeners into reporting a target word other than that which was presented (relative to U trials that have irrelevant top-down semantic context). Forty-one participants (20 men) completed 600 test trials (300 delayed report of the phrase, 300 forced choice). Relative to the U condition, women were more affected by both the I and M cues than men, at certain levels of audibility during the forced choice condition. Moreover, the semantic strength of the I carrier phrases was correlated with the rate of correct reports of the target words in women but not in men.This suggests that women can be more affected by top-down semantic context than men.

Diffusion tensor quantification of the relations between microstructural and macrostructural indices of white matter and reading.

Few researchers agree about the relationship between fronto-temporo-parietal white matter microstructure and reading skills. Unlike many previous reports, which only measured fractional anisotropy, we have also measured macroscopic volume (regional white matter tract volume) and three microstructural indices (axial, radial, and mean diffusivity) to increase interpretability of our findings. We examined the reading-related skills and white matter structure in 10 adolescents and adults with a history of poor reading and 20 age-matched typical readers. We applied a diffusion tensor imaging atlas-based algorithm to major white matter pathways. The relation of white matter structural indices to reading group, hemisphere, and reading-related skill was analyzed using linear models. White matter microstructural indices were related to performance on a sublexical decoding task, but the relations between particular microstructural indices and sublexical decoding ability and reading group were different for association (i.e., cortical-cortical) and projection (i.e., subcortical-cortical) white matter pathways. Changes in projection pathways were consistent with alterations in white matter organization and axonal size, whereas changes in association pathways were consistent with alternations in pathway complexity. Changes in macrostructure paralleled changes in microstructure. We conclude that the relations between several microstructural indices and factors related to reading ability are different for association and projection pathways.

Greater Pre-Stimulus Effective Connectivity from the Left Inferior Frontal Area to other Areas is Associated with Better Phonological Decoding in Dyslexic Readers.

Functional neuroimaging studies suggest that neural networks that subserve reading are organized differently in dyslexic readers (DRs) and typical readers (TRs), yet the hierarchical structure of these networks has not been well studied. We used Granger causality to examine the effective connectivity of the preparatory network that occurs prior to viewing a non-word stimulus that requires phonological decoding in 7 DRs and 10 TRs who were young adults. The neuromagnetic activity that occurred 500 ms prior to each rhyme trial was analyzed from sensors overlying the left and right inferior frontal areas (IFA), temporoparietal areas, and ventral occipital-temporal areas within the low, medium, and high beta and gamma sub-bands. A mixed-model analysis determined whether connectivity to or from the left and right IFAs differed across connectivity direction (into vs. out of the IFAs), brain areas, reading group, and/or performance. Results indicated that greater connectivity in the low beta sub-band from the left IFA to other cortical areas was significantly related to better non-word rhyme discrimination in DRs but not TRs. This suggests that the left IFA is an important cortical area involved in compensating for poor phonological function in DRs. We suggest that the left IFA activates a wider-than usual network prior to each trial in the service of supporting otherwise effortful phonological decoding in DRs. The fact that the left IFA provides top-down activation to both posterior left hemispheres areas used by TRs for phonological decoding and homologous right hemisphere areas is discussed. In contrast, within the high gamma sub-band, better performance was associated with decreased connectivity between the left IFA and other brain areas, in both reading groups. Overly strong gamma connectivity during the pre-stimulus period may interfere with subsequent transient activation and deactivation of sub-networks once the non-word appears.

Surface area accounts for the relation of gray matter volume to reading-related skills and history of dyslexia.

It is unknown whether the abnormalities in brain structure and function observed in dyslexic readers are congenital or arise later in development. Analyzing the 2 components of gray matter volume separately may help in differentiating these possibilities. Gray matter volume is the product of cortical surface area, determined during prenatal brain development, and cortical thickness, determined during postnatal development. For this study, 16 adults with a history of phonological dyslexia and 16 age- and gender-matched controls underwent magnetic resonance imaging and an extensive battery of tests of reading-related skills. Cortical surface area and gray matter volume measures of the whole brain, the inferior frontal gyrus, and the fusiform gyrus were similarly related to phonological skills and a history of dyslexia. There was no relationship between cortical thickness and phonological skills or history of dyslexia. Because cortical surface area reflects cortical folding patterns determined prenatally, this suggests that brain differences in dyslexia are rooted in early cortical development and are not due to compensatory changes that occur during postnatal development and would be expected to influence cortical thickness. This study demonstrates the importance of examining the separate components of gray matter volume when studying developmental abnormalities.

Splenium microstructure is related to two dimensions of reading skill.

Inconsistent differences in the corpus callosum (CC) structure between dyslexic readers (DRs) and typical readers (TRs) have been reported. We examine differences in CC splenium microstructure and the association of splenium microstructure with reading-related skills. Nine DRs and 18 TRs completed a reading skills battery and diffusion tensor imaging. DRs had higher splenium fractional anisotropy (FA) and axial diffusivity (LA) as compared with TRs. Retrieval of orthographic information from the language lexicon was negatively associated with FA and LA within both reading groups. Phonological awareness was positively associated with splenium FA and LA in TRs but not DRs. This study suggests two white matter pathways that may be differentially associated with reading skills in the CC splenium.

Objective phonological and subjective perceptual characteristics of syllables modulate spatiotemporal patterns of superior temporal gyrus activity.

Natural consonant-vowel syllables are reliably classified by most listeners as voiced or voiceless. However, our previous research [Liederman, J., Frye, R., Fisher, J.M., Greenwood, K., Alexander, R., 2005. A temporally dynamic context effect that disrupts voice onset time discrimination of rapidly successive stimuli. Psychon Bull Rev. 12, 380-386] suggests that among synthetic stimuli varying systematically in voice onset time (VOT), syllables that are classified reliably as voiceless are nonetheless perceived differently within and between listeners. This perceptual ambiguity was measured by variation in the accuracy of matching two identical stimuli presented in rapid succession. In the current experiment, we used magnetoencephalography (MEG) to examine the differential contribution of objective (i.e., VOT) and subjective (i.e., perceptual ambiguity) acoustic features on speech processing. Distributed source models estimated cortical activation within two regions of interest in the superior temporal gyrus (STG) and one in the inferior frontal gyrus. These regions were differentially modulated by VOT and perceptual ambiguity. Ambiguity strongly influenced lateralization of activation; however, the influence on lateralization was different in the anterior and middle/posterior portions of the STG. The influence of ambiguity on the relative amplitude of activity in the right and left anterior STG activity depended on VOT, whereas that of middle/posterior portions of the STG did not. These data support the idea that early cortical responses are bilaterally distributed whereas late processes are lateralized to the dominant hemisphere and support a "how/what" dual-stream auditory model. This study helps to clarify the role of the anterior STG, especially in the right hemisphere, in syllable perception. Moreover, our results demonstrate that both objective phonological and subjective perceptual characteristics of syllables independently modulate spatiotemporal patterns of cortical activation.

Linear coding of voice onset time.

Voice onset time (VOT) provides an important auditory cue for recognizing spoken consonant-vowel syllables. Although changes in the neuromagnetic response to consonant-vowel syllables with different VOT have been examined, such experiments have only manipulated VOT with respect to voicing. We utilized the characteristics of a previously developed asymmetric VOT continuum [Liederman, J., Frye, R. E., McGraw Fisher, J., Greenwood, K., & Alexander, R. A temporally dynamic contextual effect that disrupts voice onset time discrimination of rapidly successive stimuli. Psychonomic Bulletin and Review, 12, 380-386, 2005] to determine if changes in the prominent M100 neuromagnetic response were linearly modulated by VOT. Eight right-handed, English-speaking, normally developing participants performed a VOT discrimination task during a whole-head neuromagnetic recording. The M100 was identified in the gradiometers overlying the right and left temporal cortices and single dipoles were fit to each M100 waveform. A repeated measures analysis of variance with post hoc contrast test for linear trend was used to determine whether characteristics of the M100 were linearly modulated by VOT. The morphology of the M100 gradiometer waveform and the peak latency of the dipole waveform were linearly modulated by VOT. This modulation was much greater in the left, as compared to the right, hemisphere. The M100 dipole moved in a linear fashion as VOT increased in both hemispheres, but along different axes in each hemisphere. This study suggests that VOT may linearly modulate characteristics of the M100, predominately in the left hemisphere, and suggests that the VOT of consonant-vowel syllables, instead of, or in addition to, voicing, should be examined in future experiments.

A temporally dynamic context effect that disrupts voice onset time discrimination of rapidly successive stimuli.

Across three experiments, voice onset time discrimination along a/ba/-/pa/ continuum was found to be influenced by the order of presentation of rapidly successive stimuli. Specifically, discrimination was disrupted when a relatively unambiguous /pa/ syllable was presented before, rather than after, a more ambiguous /pa/ or/ba/ syllable. In Experiments 1 and 2, for between-category discrimination, this order effect was significant at interstimulus intervals (ISIs) below 250 msec, but not at 250 or 1,000 msec. In Experiments 2 and 3, the order effect was also significant for within-category discrimination at ISIs below 250 msec. In addition, in Experiment 3 this order effect was not diminished by provision of performance feedback across eight testing sessions. These findings reveal a particular vulnerability of phonological processing in response to rapidly successive stimuli and may have implications for mathematical and neural models of speech processing of normal and impaired populations.

Male vulnerability to reading disability is not likely to be a myth: a call for new data.

Whether boys are more vulnerable than girls to reading disabilities (RD) is controversial. We review studies that were designed to minimize ascertainment bias in the selection of individuals with RD. These include population-based studies that identified children with RD by objective, unbiased methods and studies that examined the gender ratios among the affected relatives of those diagnosed with RD. We conclude that even when ascertainment biases are minimized, there is still a significant preponderance of boys with RD, although the gender ratio of the affected relatives of those with RD manifests the weakest male bias. Furthermore, we demonstrate that potentially confounding factors such as attentional or neurological problems, race, IQ, and severity of RD cannot account for the observed gender bias. We end with a clarion call to future researchers to (a) consider analyzing gender differences by means of more than one definition of RD, (b) compare gender ratios when boys and girls are ranked against the performance of their own gender as opposed to an average across genders, and (c) report group differences in variability and effect sizes of obtained gender ratios.