Monitoring the Breath-Hold Training Load during an Ecological Session: A Pilot Study.

This study aimed to create a training load index to measure physiological stress during breath-hold (BH) training and examine its relationship with memory performance. Eighteen well-trained BH divers (Age: 35.8±6.6 years, BH training practice: 5.3±4.5 years) participated in this study. During a standard 1.5-hour BH training in the pool, perceived exertion, heart rate, distance, and duration were measured. The training load index was modelled on the basis of a TRIMP (TRaining IMPulse) with four different equations and was used to measure the stress induced by this BH training. A reference value, based on the ratio between the average heart rate during all BHs and the lowest heart rate during BH training, was used for comparing training load index. Memory assessment was conducted both before and after this training. Of the four equations proposed, equation no. 4, named aTRIMP for "apnoea," showed the strongest correlation with our reference value (r=0.652, p<0.01). No difference was found between any of the memory tests before and after the BH training. The aTRIMP was a new representative index for monitoring habitual training of well-trained BH divers. Furthermore, this training had no negative impact on memory performance.

Risk profiles of elite breath-hold divers.

This study aimed to determine a typical profile of elite breath-hold divers (BHDs), in relation to loss of consciousness (LOC) and episodic memory. Forty-four BHDs were evaluated during a world championship with anthropometric and physiological measurements, psychosociological factors and memory assessment. Seventy-five percent of the BHDs had at least one LOC with the predominance being men (p < 0.05). Thirty six percent of BHDs presented a low-risk profile and 64% a high-risk profile with no particular psychological pattern. Stepwise multiple linear regression showed that body fat, years of BH practice, age and forced vital capacity explained a significant amount of the variance of LOC for all BHDs (F(4,39) = 16.03, p < 0.001, R2 = 0.622, R2Adjusted = 0.583). No correlation was found between resting physiological parameters and their training or depth performances. In conclusion, anthropometric data, pulmonary factors and breath-holding experience were predictive of LOC in elite BHDs, with men taking more risks. BHDs episodic memory was not impaired.

Hippocampal subfield volumes and memory discrimination in the developing brain.

The ability to keep distinct memories of similar events is underpinned by a type of neural computation called pattern separation (PS). Children typically report coarse-grained memories narratives lacking specificity and detail. This lack of memory specificity is illustrative of an immature or impaired PS. Despite its importance for the ontogeny of memory, data regarding the maturation of PS during childhood is still scarce. PS is known to rely on the hippocampus, particularly on hippocampal subfields DG and CA3. In this study, we used a memory discrimination task, a behavioral proxy for PS, and manually segmented hippocampal subfields volumes in the hippocampal body in a cohort of 26 children aged from 5 to 12 years. We examined the association between subfields volumes and memory discrimination performance. The main results were: (1) we showed age-related differences of memory discrimination suggesting a continuous increase of memory performance during early to late childhood. (2) We evidenced distinct associations between age and the volumes of hippocampal subfield, suggesting distinct developmental trajectories. (3) We showed a relationship between memory discrimination performance and the volumes of CA3 and subiculum. Our results further confirm the role of CA3 in memory discrimination, and suggest to scrutinize more closely the role of the subiculum. Overall, we showed that hippocampal subfields contribute distinctively to PS during development.

Genetic Influence on the Sulcal Pits: On the Origin of the First Cortical Folds.

The influence of genes on cortical structures has been assessed through various phenotypes. The sulcal pits, which are the putative first cortical folds, have for long been assumed to be under tight genetic control, but this was never quantified. We estimated the pit depth heritability in various brain regions using the high quality and large sample size of the Human Connectome Project pedigree cohort. Analysis of additive genetic variance indicated that their heritability ranges between 0.2 and 0.5 and displays a regional genetic control with an overall symmetric pattern between hemispheres. However, a noticeable asymmetry of heritability estimates is observed in the superior temporal sulcus and could thus be related to language lateralization. The heritability range estimated in this study reinforces the idea that cortical shape is determined primarily by nongenetic factors, which is consistent with the important increase of cortical folding from birth to adult life and thus predominantly constrained by environmental factors. Nevertheless, the genetic cues, implicated with various local levels of heritability in the formation of sulcal pits, play a fundamental role in the normal gyral pattern development. Quantifying their influence and identifying the underlying genetic variants would provide insight into neurodevelopmental disorders.

Language plasticity after hemispherotomy of the dominant hemisphere in 3 patients: Implication of non-linguistic networks.

The neural networks involved in language recovery following hemispherotomy of the dominant hemisphere after language acquisition in children remain poorly known. Twelve hemispherotomized children (mean age at surgery: 11.3years) with comparable post-operative neuropsychological patterns underwent multi-task language functional MRI. Three of them had recovered from an initial postoperative aphasia i.e., hemispherotomy was performed on the language-dominant hemisphere. Our main results revealed (1) perisylvian activations in all patients after either left or right hemispherotomy; (2) no differences in activations between groups regarding the side of hemispherotomy; (3) additional activations in pre-frontal (3/3) and hippocampal/parahippocampal and occipito-parietal (2/3) areas, when comparing language activation in each of the three subjects with hemispherotomy of the language-dominant hemisphere to the group of 9 non-dominant hemispherotomized patients. These neural networks support the stronger engagement of learning and memory during language recovery in a hemisphere that was not initially actively subserving language.

Attention-gated 3D CapsNet for robust hippocampal segmentation.

Purpose: The hippocampus is organized in subfields (HSF) involved in learning and memory processes and widely implicated in pathologies at different ages of life, from neonatal hypoxia to temporal lobe epilepsy or Alzheimer's disease. Getting a highly accurate and robust delineation of sub-millimetric regions such as HSF to investigate anatomo-functional hypotheses is a challenge. One of the main difficulties encountered by those methodologies is related to the small size and anatomical variability of HSF, resulting in the scarcity of manual data labeling. Recently introduced, capsule networks solve analogous problems in medical imaging, providing deep learning architectures with rotational equivariance. Nonetheless, capsule networks are still two-dimensional and unassessed for the segmentation of HSF. Approach: We released a public 3D Capsule Network (3D-AGSCaps, https://github.com/clementpoiret/3D-AGSCaps) and compared it to equivalent architectures using classical convolutions on the automatic segmentation of HSF on small and atypical datasets (incomplete hippocampal inversion, IHI). We tested 3D-AGSCaps on three datasets with manually labeled hippocampi. Results: Our main results were: (1) 3D-AGSCaps produced segmentations with a better Dice Coefficient compared to CNNs on rotated hippocampi (p=0.004, cohen's d=0.179); (2) on typical subjects, 3D-AGSCaps produced segmentations with a Dice coefficient similar to CNNs while having 15 times fewer parameters (2.285M versus 35.069M). This may greatly facilitate the study of atypical subjects, including healthy and pathological cases like those presenting an IHI. Conclusion: We expect our newly introduced 3D-AGSCaps to allow a more accurate and fully automated segmentation on atypical populations, small datasets, as well as on and large cohorts where manual segmentations are nearly intractable.

A fast and robust hippocampal subfields segmentation: HSF revealing lifespan volumetric dynamics.

The hippocampal subfields, pivotal to episodic memory, are distinct both in terms of cyto- and myeloarchitectony. Studying the structure of hippocampal subfields in vivo is crucial to understand volumetric trajectories across the lifespan, from the emergence of episodic memory during early childhood to memory impairments found in older adults. However, segmenting hippocampal subfields on conventional MRI sequences is challenging because of their small size. Furthermore, there is to date no unified segmentation protocol for the hippocampal subfields, which limits comparisons between studies. Therefore, we introduced a novel segmentation tool called HSF short for hippocampal segmentation factory, which leverages an end-to-end deep learning pipeline. First, we validated HSF against currently used tools (ASHS, HIPS, and HippUnfold). Then, we used HSF on 3,750 subjects from the HCP development, young adults, and aging datasets to study the effect of age and sex on hippocampal subfields volumes. Firstly, we showed HSF to be closer to manual segmentation than other currently used tools (p < 0.001), regarding the Dice Coefficient, Hausdorff Distance, and Volumetric Similarity. Then, we showed differential maturation and aging across subfields, with the dentate gyrus being the most affected by age. We also found faster growth and decay in men than in women for most hippocampal subfields. Thus, while we introduced a new, fast and robust end-to-end segmentation tool, our neuroanatomical results concerning the lifespan trajectories of the hippocampal subfields reconcile previous conflicting results.

Questioning cognitive heterogeneity and intellectual functioning in fetal alcohol spectrum disorders from the Wechsler intelligence scale for children.

Introduction: Fetal Alcohol Spectrum Disorders (FASD) are characterized by a variety of multiple cognitive and behavioral impairments, with intellectual, attentional, and executive impairments being the most commonly reported. In populations with multiple neurodevelopmental disorders, the Full Scale Intelligence Quotient (FSIQ) may not be a proper measure of intellectual abilities, rarely interpreted in FASD clinical practice because the heterogeneity of the cognitive profile is deemed too strong. We propose a quantitative characterization of this heterogeneity, of the strengths and weaknesses profile, and a differential analysis between global cognitive (FSIQ) and elementary reasoning abilities in a large retrospective monocentric FASD sample. Methods: Using clinical and cognitive data (Wechsler Intelligence Scale for Children) from 107 children with FASD, we characterized subject heterogeneity (variance and scatter of scaled/composite scores), searched for strengths and weaknesses, and specified intellectual functioning in terms of FSIQ and elementary reasoning (General Abilities Index, Highest Reasoning Scaled Score), in comparison with standardization norms and a Monte-Carlo-simulated sample from normalization data. Results: Performance of children with FASD was lower on all subtests, with a significant weakness in working memory and processing speed. We found no increase in the variance and scatter of the scores, but a discordance between the assessment of global cognitive functioning (28% borderline, 23% deficient) and that of global and elementary reasoning abilities (23-9% borderline, 15-14% deficient). Conclusion: Our results question the notion of WISC profile heterogeneity in FASD and point to working memory and processing speed over-impairment, with global repercussions but most often preserved elementary reasoning abilities.

Maturity of white matter tracts is associated with episodic memory recall during development.

The structure-function relationship between white matter microstructure and episodic memory (EM) has been poorly studied in the developing brain, particularly in early childhood. Previous studies in adolescents and adults have shown that episodic memory recall is associated with prefrontal-limbic white matter microstructure. It is unknown whether this association is also observed during early ontogeny. Here, we investigated the association between prefrontal-limbic tract microstructure and EM performance in a cross-sectional sample of children aged 4 to 12 years. We used a multivariate partial least squares correlation approach to extract tract-specific latent variables representing shared information between age and diffusion parameters describing tract microstructure. Individual projections onto these latent variables describe patterns of interindividual differences in tract maturation that can be interpreted as scores of white matter tract microstructural maturity. Using these estimates of microstructural maturity, we showed that maturity scores of the uncinate fasciculus and dorsal cingulum bundle correlated with distinct measures of EM recall. Furthermore, the association between tract maturity scores and EM recall was comparable between younger and older children. Our results provide new evidence on the relation between white matter maturity and EM performance during development.

Modulation of encoding and retrieval by recollection and familiarity: mapping the medial temporal lobe networks.

Medial temporal lobe (MTL) structures are crucial for episodic memory. However, it remains unclear how these structures are involved in encoding and retrieval processes as a function of recollection and familiarity. To better elucidate MTL organization of these two processes, we implemented an fMRI protocol in which both encoding and retrieval of words were scanned in 21 healthy adults. During encoding, subjects were requested to bind each word to an emotional context (pleasant or unpleasant). Retrieval consisted of a Remember/Know procedure in two stages: first, subjects had to recognize the word, followed by the retrieval of the associated emotional context. fMRI data were reported in eight manually delineated MTL regions of interest (in the head, body and tail of the hippocampus, the entorhinal, perirhinal and parahippocampal cortices, the amygdala and the temporopolar cortex). Results obtained in 19 subjects showed four MTL patterns of activity consisting in activations of parahippocampal cortex and hippocampus in episodic encoding and retrieval and perirhinal cortex involvement in familiarity. These results are in line with the Binding of Item and Context (BIC) model predictions. Additionally, some new findings specified the familiarity MTL neural substrate by showing precise entorhinal activations during retrieval of familiar words, as well as hippocampal and amygdala deactivations in encoding of these words. Finally, we emphasize that among all four memory processes, episodic retrieval (recollection effect) was the only one eliciting strong bilateral activations in all MTL structures. These results should be considered for future studies on MTL dysfunction in patients with temporal lobe damage.

Memory: Normative development of memory systems.

During the past decades, abundant behavioral, clinical, and neuroimaging data have shown several memory systems in the brain. A memory system is a type of memory that processes a particular type of information, using specific mechanisms, with distinct neural correlates. What we call memory is therefore not a unitary capacity but a collection of distinct systems. From a developmental perspective, each memory system has its own developmental course. This explains the heterogeneity of children's mnemonic competencies: for example, 3-year-olds learn many new words and concepts every day but have trouble recalling in detail an event that happened the week before. In this chapter, we sum up major findings regarding the development from infancy to early adulthood of the main memory systems. Specifically, we report recent data regarding the development of declarative memory (i.e., episodic and semantic memory), and the relationship between the maturation of their neural correlates and the phenomena of infantile and childhood amnesia. We conclude by indicating some of the possible avenues for future research.

Breath-hold diving strategies to avoid loss of consciousness: speed is the key factor.

The aim of this study was to investigate the impact of breath-hold diving strategies regarding loss of consciousness (LOC). Three international competitions were examined through video in constant weight diving with (CWT) or without (CNF) fins. We analysed three breath-hold parameters (time, speed, and movements count) for the following phases: active descent, passive descent, turning, and ascent. Divers who had LOC during CNF were slower in the active descent phase, faster in the passive descent phase with a longer turn, and slower in the ascent phase than divers who did not have LOC. They also had lower amplitude and higher frequency. Men were deeper (72.9 m vs. 56.3 m) for a longer dive time (181.1 s vs. 154.6 s), faster, with a greater amplitude than women. In CWT, divers with an LOC had longer dive times (197 s vs. 167 s) with a faster active descent phase. Men had lower amplitude and greater frequency than women. This is the first study showing that breath-hold divers undergoing an LOC event shown differences in efficiency during CWT and CNF regarding velocities, amplitudes, and frequencies. In conclusion, our results suggest that the speed parameter during active descent phase influence the LOC.

Where are your body parts? A pure case of heterotopagnosia following left parietal stroke.

We studied the involvement of the parietal cortex in interpersonal body representation in a left parietal stroke patient. We used tasks assessing different types of body representations and localization of object parts. The patient performed normally on all tasks of body knowledge. However, she was unable to locate body parts on another person or on body representations. In contrast, she pointed correctly to the same body parts on herself or object representations. The data support the important role of the left parietal cortex in the transformation of intrinsic spatial coding of body parts localization in extrinsic body part coordinates.

Extension to one week of verbal memory consolidation assessment.

OBJECTIVE: Although impairments of long-term recall affect everyday life, they may be missed by standard delayed recall tests, which typically assess the ability to retain new information within a few minutes, without encompassing the consolidation process. We adapted a verbal memory test to evaluate long-term memory consolidation in healthy volunteers. METHOD: A sample of 238 participants (M = 42.23 years old, SD = 16.45) was administered an adapted version of the French RL/RI-16 (Van der Linden & the members of GREMEM, 2004), the One-Week Free and Cued Selective Reminding Test-word version, in which special feature relies on a 30-min and a 1-week-delayed recall after encoding. We proposed normative data on 4 indicators, depending on participants' own performance during the test, to measure their encoding, storage and consolidation abilities, with a method using an ascendant step-by-step linear regression model and a percentile procedure. RESULTS: Results showed a better performance in women than in men for encoding and cueing scores (p < .01 and p < .05, respectively). We also highlighted an increase of the forgetting score according to the recall delay after encoding (30 min vs. 7 days; Z = 12.49, p < .001), the forgetting percentage 7 days after encoding being largely influenced by participants' age and gender (F[2, 236] = 248.1, p < .001; adjusted R2 = 67%). CONCLUSIONS: This study emphasized the role of demographic factors on long-term memory consolidation. The demographically adjusted normative data we provide for the One-Week Free and Cued Selective Reminding Test-word version make it a sensitive tool for long-term memory consolidation assessment in clinical and forensic practice. (PsycINFO Database Record

Three-Dimensional Probabilistic Maps of Mesial Temporal Lobe Structures in Children and Adolescents' Brains.

The hippocampus and the adjacent perirhinal, entorhinal, temporopolar, and parahippocampal cortices are interconnected in a hierarchical MTL system crucial for memory processes. A probabilistic description of the anatomical location and spatial variability of MTL cortices in the child and adolescent brain would help to assess structure-function relationships. The rhinal sulcus (RS) and the collateral sulcus (CS) that border MTL cortices and influence their morphology have never been described in these populations. In this study, we identified the aforementioned structures on magnetic resonance images of 38 healthy subjects aged 7-17 years old. Relative to sulcal morphometry in the MTL, we showed RS-CS conformation is an additional factor of variability in the MTL that is not explained by other variables such as age, sex and brain volume; with an innovative method using permutation testing of the extrema of structures of interest, we showed that RS-SC conformation was not associated with differences of location of MTL sulci. Relative to probabilistic maps, we offered for the first time a systematic mapping of MTL structures in children and adolescent, mapping all the structures of the MTL system while taking sulcal morphology into account. Our results, with the probabilistic maps described here being freely available for download, will help to understand the anatomy of this region and help functional and clinical studies to accurately test structure-function hypotheses in the MTL during development. Free access to MTL pediatric atlas: http://neurovault.org/collections/2381/.

Role of the medial temporal lobe in time estimation in the range of minutes.

This study examined the role of medial temporal lobe structures in verbal estimation and production of time intervals. Left medial temporal lobe lesions produced deficits in both tasks, whereas right medial temporal lobe lesions only disturbed time production. Although both tasks require adequate use of chronometric units, they seem to be subserved by distinct cognitive processing and to depend on different neural substrates. Verbal estimation of intervals in retrospect seems to depend mainly on contextual memory, and production of intervals depends more specifically on the mental load devoted to time. These findings, documenting for the first time the role of each temporal lobe in duration estimation within the range of minutes, are discussed in light of memory-based and attentional models of time.

Emotional responses to unpleasant music correlates with damage to the parahippocampal cortex.

Music is typically a pleasurable experience. But under certain circumstances, music can also be unpleasant, for example, when a young child randomly hits piano keys. Such unpleasant musical experiences have been shown to activate a network of brain structures involved in emotion, mostly located in the medial temporal lobe: the parahippocampal gyrus, amygdala, hippocampus and temporal pole. However, the differential roles of these regions remain largely unknown. In this study, pleasant and unpleasant music was presented to 17 patients with variable excisions of the medial temporal lobe, as well as to 19 matched controls. The pleasant music corresponded to happy and sad selections taken from the classical instrumental repertoire; the unpleasant music was the dissonant arrangement of the same selections. Only patients with substantial resections of the left or right parahippocampal cortex (PHC) gave highly abnormal judgements to dissonant music; they rated dissonant music as slightly pleasant while controls found it unpleasant. This indifference to dissonance was correlated with the remaining volume in the PHC, but was unrelated to the volume of the surrounding structures. The impairment was specific: the same patients judged consonant music to be pleasant, and were able to judge music as happy or sad. Furthermore, this lack of responsiveness to unpleasantness was not due to a perceptual disorder, because all patients were able to detect intentional errors in the musical excerpts. Moreover, the impairment differed from that induced by amygdala damage alone. These findings are consistent with a two-dimensional model of defensive responses to aversive stimuli, in which the PHC and the amygdala subserve different roles.

How emotional auditory stimuli modulate time perception.

Emotional and neutral sounds rated for valence and arousal were used to investigate the influence of emotions on timing in reproduction and verbal estimation tasks with durations from 2 s to 6 s. Results revealed an effect of emotion on temporal judgment, with emotional stimuli judged to be longer than neutral ones for a similar arousal level. Within scalar expectancy theory (J. Gibbon, R. Church, & W. Meck, 1984), this suggests that emotion-induced activation generates an increase in pacemaker rate, leading to a longer perceived duration. A further exploration of self-assessed emotional dimensions showed an effect of valence and arousal. Negative sounds were judged to be longer than positive ones, indicating that negative stimuli generate a greater increase of activation. High-arousing stimuli were perceived to be shorter than low-arousing ones. Consistent with attentional models of timing, this seems to reflect a decrease of attention devoted to time, leading to a shorter perceived duration. These effects, robust across the 2 tasks, are limited to short intervals and overall suggest that both activation and attentional processes modulate the timing of emotional events.

Relationships between Regional Radiation Doses and Cognitive Decline in Children Treated with Cranio-Spinal Irradiation for Posterior Fossa Tumors.

Pediatric posterior fossa tumor (PFT) survivors who have been treated with cranial radiation therapy often suffer from cognitive impairments that might relate to IQ decline. Radiotherapy (RT) distinctly affects brain regions involved in different cognitive functions. However, the relative contribution of regional irradiation to the different cognitive impairments still remains unclear. We investigated the relationships between the changes in different cognitive scores and radiation dose distribution in 30 children treated for a PFT. Our exploratory analysis was based on a principal component analysis (PCA) and an ordinary least square regression approach. The use of a PCA was an innovative way to cluster correlated irradiated regions due to similar radiation therapy protocols across patients. Our results suggest an association between working memory decline and a high dose (equivalent uniform dose, EUD) delivered to the orbitofrontal regions, whereas the decline of processing speed seemed more related to EUD in the temporal lobes and posterior fossa. To identify regional effects of RT on cognitive functions may help to propose a rehabilitation program adapted to the risk of cognitive impairment.