Dave Saint-Amour

• PhD
• Professor (Full) at University of Quebec in Montreal

Chronic manganese (Mn) exposure is associated with neuromotor and neurocognitive deficits, but the exact mechanism of Mn neurotoxicity is still unclear. With the advent of magnetic resonance imaging (MRI), in-vivo analysis of brain structures has become possible. Among different sub-cortical structures, the basal ganglia (BG) has been investigated...

The aim of this study was to develop a fast and efficient electrophysiological protocol to examine the visual field's integrity, which would be useful in pediatric testing. Steady-state visual-evoked potentials (ssVEPs) to field-specific radial checkerboards flickering at two cycle frequencies (7.5 and 6 Hz for central and peripheral stimulations,...

To establish an electrophysiological marker of binocular vision, visual evoked potentials were recorded in normal observers for whom interocular refraction differences were induced with converging lenses under five dioptre conditions. Patterns of binocular interaction were categorized (facilitation, averaging or suppression) by comparing monocular...

To assess the long-term effect on visual development of omega-3 polyunsaturated fatty acid (n-3 PUFA) intake during gestation. Using visual evoked potentials (VEPs), the long-term effects on visual development were evaluated in 136 school-age Inuit children exposed to high levels of n-3 PUFAs during gestation. VEP protocols using color and motion s...

Seeing a speaker's facial articulatory gestures powerfully affects speech perception, helping us overcome noisy acoustical environments. One particularly dramatic illustration of visual influences on speech perception is the "McGurk illusion", where dubbing an auditory phoneme onto video of an incongruent articulatory movement can often lead to ill...

Background Organic solvents are used in formulating an extensive range of products for professional use. Animal and human studies suggest that in utero solvent exposure may affect neurodevelopment. Our objective was to assess the association between occupational exposure to solvents during pregnancy and child behavior aged 2–12 years. Methods The...

Background: Per- and polyfluoroalkyl substances (PFAS) are chemical substances spread throughout the environment worldwide. Exposure during pregnancy represents a specific window of vulnerability for child health. Objective: Our objective was to assess the impact of prenatal exposure to multiple PFAS on emotional and behavioral functions in 12-y...

Background Prenatal fluoride exposure can have adverse effects on children’s development; however, associations with visual and cardiac autonomic nervous system functioning are unknown. We examined associations between prenatal fluoride exposure and visual acuity and heart rate variability (HRV) in 6-month-old infants. Methods We used data from Ca...

Despite extensive evidence from cohort studies linking exposure to lead (Pb), mercury (Hg) and polychlorinated biphenyls (PCBs) to numerous cognitive outcomes in children and adolescents, very few studies addressed reward sensitivity, a key dimension of emotional regulation. The present study aimed to examine associations between pre- and postnatal...

Excessive screen time has been linked to adverse health outcomes in children, including vision-related problems such as myopia. However, very few studies have evaluated the effect of moderate screen exposure on the development of visual functions. This study aimed to examine the association between screen time during middle childhood and color disc...

Background: Prenatal and childhood mercury (Hg) exposures have been associated with negative impacts on child neurodevelopment. It is unclear if associations persist at the low Hg exposures typical in Western countries. Objective: To examine associations between prenatal/childhood blood Hg concentrations and child IQ in Canadian male and female...

Introduction Polychlorobiphenyls (PCBs), organochlorine pesticides (OCPs) and per- and polyfluoroalkyl substances (PFASs) are persistent organic pollutants (POPs) having numerous toxicological properties, including thyroid endocrine disruption. Our aim was to assess the impact of POPs on thyroid hormones among 12-years children, while taking pubert...

Inuit communities in Northern Quebec (Canada) are exposed to environmental contaminants, particularly to mercury, lead and polychlorinated biphenyls (PCBs). Previous studies reported adverse associations between these neurotoxicants and memory performance. Here we aimed to determine the associations of pre- and postnatal exposures to mercury, lead...

The modulation of early sensory event-related potentials such as the P1, N1, and N170 by emotion and emotional ambiguity is still controversial. Some studies have found a modulation of one or all of these components by one or both of these factors, whereas others have failed to show such results. The objective of this study was to investigate the e...

Exposure to environmental contaminants is an important public health concern for the Inuit population of northern Québec, who have been exposed to mercury (Hg), polychlorinated biphenyls (PCBs) and lead (Pb). During the last 25 years, the Nunavik Child Development Study (NCDS) birth cohort has reported adverse associations between these exposures a...

Processing and recognizing facial expressions are key factors in human social interaction. Past research suggests that individuals with autism spectrum disorder (ASD) present difficulties to decode facial expressions. Those difficulties are notably attributed to altered strategies in the visual scanning of expressive faces. Numerous studies have de...

(1) Background: Lutein and zeaxanthin (L&Z) are essential dietary nutrients that are a crucial component of the human macula, contributing to visual functioning. They easily cross the placental barrier, so that retinal deposition commences during foetal development. This study aims to assess associations between maternal L&Z intake during pregnancy...

Application of transcranial alternating current stimulation (tACS) is thought to modulate ongoing brain oscillations in a frequency-dependent manner. However, recent studies report various and sometimes inconsistent results regarding its capacity to induce changes in cortical activity beyond the stimulation period. Here, thirty healthy volunteers p...

Orthorexia Nervosa (ON), a condition characterized by a fixation on healthy eating, still does not conform to any consensus concerning diagnostic criteria, notably in regard to a possible body image component. This study investigated the relationship between ON symptomatology, measured with the Eating Habit Questionnaire, and body image attitudes a...

Grapheme-colour synesthesia occurs when letters or numbers elicit an abnormal colour sensation (e.g., printed black letters are perceived as coloured). This phenomenon is typically reported following explicit presentation of graphemes. Very few studies have investigated colour sensations in synesthesia in the absence of visual awareness. We took ad...

Exposure to mercury, lead and polychlorinated biphenyls (PCBs) have been associated with emotional dysregulation, but their neuronal correlates have yet to be examined. Inuit from Nunavik (Northern Quebec, Canada) face internalizing problems and are among the most exposed individuals to these environmental contaminants in the world. The aim of this...

Significance: Enchroma glasses were designed to improve color vision among color-blind individuals. The putative aid of such optic filters in alleviating color blindness remains to be demonstrated. Our study shows that the beneficial impacts on color discrimination are quite small in comparison to the undesirable effects. Purpose: Congenital color...

Background Maternal occupational exposure to organic solvents during pregnancy has been associated with decreased visual function in offspring. Glycol ethers (GEs) belong to oxygenated solvents and are widely used both in occupational and domestic contexts. Objectives We aimed to assess associations between prenatal GEs exposure and contrast sensi...

Background Organophosphate pesticides (OP) are widely used for both agricultural and domestic purposes. Epidemiological studies suggest neurotoxicity in children after exposure to organophosphates pesticides (OP) at low levels but possible mechanism is still unclear. Objectives We aimed at investigating the effects of prenatal exposure to OPs on i...

Recent evidence suggests that prenatal exposure to chlordecone, a persistent organochlorine pesticide that was used intensively in the French West Indies, affects infant neurodevelopment. The aim of the present study was to evaluate the association between prenatal and postnatal chlordecone exposures on visual contrast sensitivity in 285 children a...

Abstract Background Prenatal exposure to environmental contaminants can have deleterious effects on child development. While psychomotor, cognitive and behavioural outcomes have been investigated in relation to chronic exposure, the associations with visual functions remains unclear. The present study’s aim was to assess the associations of prenata...

Exposure to environmental toxicants can have deleterious effects on the development of physical, cognitive, and mental health. Extensive laboratory and clinical studies have demonstrated how the developing brain is uniquely sensitive to toxic agents. This chapter focuses on the main neurologic impairments linked to prenatal and postnatal exposure t...

Grapheme-color synesthesia is a perceptual phenomenon that occurs when letters or numbers elicit an abnormal color sensation (e.g., printed black letters are perceived as colored graphemes). Grapheme-color synesthesia is typically reported following explicit presentation of graphemes. Very few studies have investigated color sensations in synesthes...

Purpose Treatment of optic pathway gliomas is prompted by neuroradiological evidence of tumor growth, usually associated with progressive visual loss. Despite therapy, approximately 40% will show visual deterioration. Treatment outcome is largely based on the preservation of vision. However, current visual function assessment is often unreliable in...

Background: Pregnant women are ubiquitously exposed to organic solvents, such as glycol ethers. Several studies suggest potential developmental neurotoxicity following exposure to glycol ethers with a lack of clarity of possible brain mechanisms. Objectives: We investigated the association between urinary levels of glycol ethers of women during...

Background: Pregnant women are ubiquitously exposed to organic solvents, such as glycol ethers. Several studies suggest potential developmental neurotoxicity following exposure to glycol ethers with a lack of clarity of possible brain mechanisms. Objectives: We investigated the association between urinary levels of glycol ethers of women during ear...

Dysfunctions in fronto-amygdala circuitry have been linked to anxiety. Questions remain regarding the impact of familial-risk and ongoing anxiety on such circuitry function, especially in youth. Using fMRI fear conditioning and extinction paradigms, we examined these relationships in 10-17 year-olds: 22 youth with an anxiety disorder, 22 healthy yo...

In grapheme-color synesthesia, letters and numbers evoke abnormal colored perceptions. Although the underlying mechanisms are not known, it is largely thought that the synesthetic brain is characterized by atypical connectivity throughout various brain regions, including the visual areas. To study the putative impact of synesthesia on the visual br...

Sex differences in inner-ear function are detectable in infants, notably through the measurement of otoacoustic emissions (OAEs). Prevailing theories posit that prenatal exposure to high levels of androgens in boys may weaken OAEs, and that this phenomenon may predominantly affect the right ear/left hemisphere (Geschwind-Galaburda (GG) hypothesis)....

Healthy aging is associated with decline of motor function that can generate serious consequences on the quality of life and safety. Our studies aim to explore the 3-month effects of a 5-day multisession anodal transcranial direct current stimulation (a-tDCS) protocol applied over the primary motor cortex (M1) during motor sequence learning in elde...

Human exposure to organophosphate pesticides (OP) is widespread. Several studies suggest that OP prenatal exposure alters the development of cognitive and behavioural functions in children, but the effects of OP prenatal exposure on child sensory functions are largely unknown. The aim of the study was to evaluate the association between OP prenatal...

The unisensory nature of the primary visual cortex is questioned by an increasing number of studies. Here we explore the time course of the response of several “visual areas” following spatial auditory stimulations and we investigate the presence of lateralization effects.

Objectives: The present aging study investigated the impact of a multisession anodal-tDCS protocol applied over the primary motor cortex (M1) during motor sequence learning on generalization of motor learning and plasticity-dependent measures of cortical excitability. Methods: A total of 32 cognitively-intact aging participants performed five co...

Purpose: Previous research suggests that exposure to pesticides might be associated with human myopia, although data were obtained only from highly exposed individuals. The present study aimed to assess whether exposure to organophosphates and pyrethroids in the United States general population was associated with the prevalence of myopia. Method...

Background: Manganese is commonly found in water but potential neurotoxic effects from exposure through drinking water are poorly understood. We previously reported a cross-sectional study showing that drinking water Mn concentration was associated with lower IQ in children aged 6 to 13 years. Objective: For this follow-up study, we aimed to re-...

Background: Optic pathway gliomas (OPG) represent 5% of pediatric brain tumours. Visual acuity measures are used to evaluate treatment response. Current clinical tests to assess visual field integrity are subjective and require verbal cooperation. Thus, the objective of this study was to evaluate the clinical effectiveness of Steady State Visual Ev...

Purpose: Behavioral and electrophysiological methods for visual acuity estimation typically correlate well in children and adult populations, but this relationship remains unclear in infants, particularly during the second half of the first year of life. It has been suggested that the agreement between both methods mostly relies on age and/or subj...

There is debate whether social impairments in autism spectrum disorder (ASD) are truly domain-specific, or if they reflect generalized deficits in lower-level cognitive processes. To solve this issue, we used auditory-evoked EEG responses to assess novelty detection (MMN component) and involuntary attentional orientation (P3 component) induced by s...

Along with the aging of the population, various comorbidities may arise, such as arthritis, hypertension, and erectile dysfunction. These medical conditions are treated and controlled with various types of medications. In fact, nearly 83% of older adults in Canada take prescription medications by age 65 years. Several of these medications can induc...

Optic Pathway Gliomas (OPG) represent 4-6% of brain tumors in children. Magnetic resonance imaging (MRI) and visual acuity are usually used to evaluate clinical evolution and treatment response. Since the goal of treatment is to preserve vision, it is important to develop new rapid, reliable, and non-invasive techniques to objectively measure the i...

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L’objet de cet article est de présenter une revue des divers facteurs de risques et des corrélats neuronaux associés au développement des troubles intériorisés, soit les troubles anxieux et dépressifs. Un accent est mis sur la contribution de l’exposition aux contaminants environnementaux dans le développement de troubles intériorisés, en particuli...

We used magnetoencephalography to investigate the nature of the underlying plastic mechanisms related to the onset of blindness. We show here the temporal course, strength, and extent of occipital activation at scalp level of congenital (n=11), late blind (n=7) and sighted(n=12) individuals; and we report the event-related spectral perturbations al...

Background: Manganese (Mn) can have neurotoxic effects upon overexposure. We previously reported poorer cognitive and motor development in children exposed to Mn through drinking water, suggesting possible neurotoxic effects from Mn in water. Hyperintensity in the globus pallidus (GP) on T1-weighted magnetic resonance imaging (MRI) indicates exces...

Background: Several studies suggest that exposure to organophosphate insecticides (OP) during pregnancy impairs neurodevelopment in children. Objectives: We evaluated associations between biomarkers of prenatal and postnatal OP exposure and cognitive function of 6-year-olds in a French longitudinal birth cohort. Methods: In 2002-2006, the PELA...

Human EEG studies have shown that development of visual processing is associated with changes in entropy, i.e., signal variability. In the present study we asked whether abnormal development associated with amblyopia alters brain signal entropy at adulthood. Brain's electrical resting state activity was recorded from occipital (Oz), central (Cz) an...

Purpose: Several recent studies have demonstrated that following short-term monocular deprivation in normal adults, the patched eye, rather than the unpatched eye, becomes stronger in subsequent binocular viewing. However, little is known about the site and nature of the underlying processes. In this study, we examine the underlying mechanisms by...

Purpose. Although children with microstrabismus demonstrate stereoscopic abilities when assessed with clinical tests containing visible contours (local stereopsis), severe stereoscopic impairments are reported when using random-dot stereogram (RDS). This differential performance may be associated with the decreasing interocular correlation resultin...

Purpose: Visual deficits in amblyopia are neural in origin, yet are difficult to characterise using fMRI. Our aim was to develop an objective EEG paradigm that can be used to provide a clinically useful index of amblyopic deficits. Methods: We used steady-state visual evoked potentials (SSVEPs) to measure full contrast response functions in both am...

Omega-3 (n-3) fatty acids are highly concentrated in neuronal membranes and retina photoreceptors, where they accumulate from midpregnancy until the first years of life. A growing body of evidence links n-3 fatty acids with visual and cognitive functions. Because the fetus and breastfed infants depend on their mother's dietary intake for n-3 fatty...

Background: Manganese neurotoxicity is well documented in individuals occupationally exposed to airborne particulates, but few data are available on risks from drinking-water exposure. Objective: We examined associations of exposure from concentrations of manganese in water and hair with memory, attention, motor function, and parent- and teacher...

Introduction: Synesthesia is a perceptual phenomenon when a stimulus in one sensory modality elicits an additional percept in the same or in another modality (e.g., when black letters and numbers are perceived as color graphemes or when sounds inducing color percepts). Although the underlying mechanisms of synesthesia are not known, it is largely t...

Stimulus rivalry refers to the sustained periods of perceptual dominance that occur when different visual stimuli are swapped at a regular rate between eyes. This phenomenon is thought to involve mainly eye-independent mechanisms. Although several studies have reported that attention can increase image predominance in conventional binocular rivalry...

Although children with microstrabismus demonstrate stereoscopic abilities when assessed with clinical tests containing visible contours (local stereopsis), severe stereoscopic impairments are reported when using random-dot stereogram (RDS). This differential performance may be associated with the decreasing interocular correlation resulting from th...

Polychlorinated biphenyls (PCBs) are ubiquitously present in people because of their resistance to degradation and accumulation in fatty tissues. Data on neurotoxic effects in older adults are limited. To examine the cross-sectional association between serum PCB concentrations and cognitive function in older adults from the general U.S. population....

Under noisy listening conditions, visualizing a speaker's articulations substantially improves speech intelligibility. This multisensory speech integration ability is crucial to effective communication, and the appropriate development of this capacity greatly impacts a child's ability to successfully navigate educational and social settings. Resear...

Background. Although atypical performance on visuo-spatial tasks targeting early, non-social perception is a defining characteristic of autism, few biologically plausible hypotheses are available to explain them. Some authors have theorized that persons with autism may have atypical local connectivity resulting in altered response properties of ear...

A growing body of evidence suggests that binocular interactions are still present in amblyopes under certain viewing conditions, even in adults. Here we determined whether suppression was bidirectional (from dominant eye to the amblyopic eye but also from the amblyopic to the dominant eye) and explored the neural correlates. We tested the degree of...

The Maternal-Infant Research on Environmental Chemicals (MIREC) Study was established to obtain Canadian biomonitoring data for pregnant women and their infants, and to examine potential adverse health effects of prenatal exposure to priority environmental chemicals on pregnancy and infant health. Women were recruited during the first trimester fro...

To develop and function optimally, the brain requires a balanced environment of electrolytes, amino acids, neurotransmitters, and metabolic substrates. As a consequence, organ dysfunction has the potential to induce brain disorders and toxic-metabolic encephalopathies, particularly when occurring during early stages of cerebral maturation. Induced...

Stimulus rivalry refers to the sustained periods of perceptual dominance that occur when different visual stimuli are swapped at a regular rate between eyes. This phenomenon is thought to involve mainly eye-independent mechanisms. Although several studies have reported that attention can increase image predominance in conventional binocular rivalry...

The Inuit from Nunavik (Northern Québec) are one of the most highly exposed populations to environmental contaminants in North America mainly due to the bioaccumulation of contaminants in fish and marine mammals that constitute an important part of their diet. This follow-up study aimed to assess the impact of exposure to contaminants on visual bra...

The contribution of cognitive neuroscience towards studying the impact of environmental contaminants on brain function development Human studies on the neurotoxicity associated with chronic exposure to environmental contaminants have targeted cognitive functions such as IQ and memory. Cognitive neurosciences offer additional tools for understanding...

Lead (Pb) and polychlorinated biphenyls (PCBs) are neurotoxic contaminants that have been related to impairment in response inhibition. In this study we examined the neurophysiological correlates of the response inhibition deficits associated with these exposures, using event-related potentials (ERPs) in a sample of school-age Inuit children from A...

Introduction: It is generally accepted that stereopsis is present in patients with microstrabismus, although it is reduced. This concept relies primarily on the evaluation of local stereopsis, which contains visible monocular cues. However, microstrabismic patients seem to present much more impairment in identifying the global form in random dot s...

Observing a speaker's articulations substantially improves the intelligibility of spoken speech, especially under noisy listening conditions. This multisensory integration of speech inputs is crucial to effective communication. Appropriate development of this ability has major implications for children in classroom and social settings, and deficits...

It is generally accepted that stereopsis is present in patients with microstrabismus, although it is reduced. This concept relies primarily on the evaluation of local stereopsis, which contains visible monocular cues. However, microstrabismic patients seem to present much more impairment in identifying the global form in random dot stereograms (glo...

The beneficial effects of prenatal and early postnatal intakes of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) on cognitive development during infancy are well recognized. However, few studies have examined the extent to which these benefits continue to be evident in childhood. The aim of this study was to examine the relation of n-3 PUFAs and...