Maurice Ptito

Maurice Ptito
Université de Montréal and University of Copenhagen · School of Optometry; Neuropsychiatry Laboratory, Psychiatric Centre Copenhagen

Ph.D., Dr. Med., FRSC

About

305
Publications
45,180
Reads
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8,177
Citations
Education
January 1998 - January 2002
Aarhus University
Field of study
  • PET imaging
February 1994 - October 1996
Stanford University
Field of study
  • Neurophysiology
June 1971 - February 1974
Université de Montréal
Field of study
  • Neuropsychology

Publications

Publications (305)
Article
Full-text available
Rationale Glucagon-like peptide-1 (GLP-1) receptor agonists reduce alcohol consumption in rodents and non-human primates. Semaglutide is a new long-acting GLP-1 receptor agonist, widely used in the clinic against type 2 diabetes and obesity. It is also reported to reduce alcohol intake in rodents. Objectives This study investigates the possible in...
Preprint
We used diffusion MRI and x-ray synchrotron imaging on monkey and mice brains to examine the organisation of fibre pathways in white matter across anatomical scales. We compared the structure in the corpus callosum and crossing fibre regions and investigated the differences in cuprizone-induced experimental demyelination mouse brains versus healthy...
Preprint
We used diffusion MRI and x-ray synchrotron imaging on monkey and mice brains to examine the organisation of fibre pathways in white matter across anatomical scales. We compared the structure in the corpus callosum and crossing fibre regions and investigated the differences in cuprizone-induced experimental demyelination mouse brains versus healthy...
Preprint
Full-text available
We used diffusion MRI and x-ray synchrotron imaging on monkey and mice brains to examine the organisation of fibre pathways in white matter across anatomical scales. We compared the structure in the corpus callosum and crossing fibre regions and investigated the differences in cuprizone-induced experimental demyelination mouse brains versus healthy...
Article
Full-text available
For blind individuals, tactile maps are useful tools to form cognitive maps through touch. However, they still experience challenges in cognitive map formation and independent navigation. Three-dimensional (3D) tactile information is thus increasingly being considered to convey enriched spatial information, but it remains unclear if it can facilita...
Article
Full-text available
In recent decades, numerous structural brain imaging studies investigated purported morphometric changes in early (EB) and late onset blindness (LB). The results of these studies have not yielded very consistent results, neither with respect to the type, nor to the anatomical locations of the brain morphometric alterations. To better characterize t...
Research Proposal
Full-text available
n congenital blindness (CB), tactile and auditory information can be reinterpreted by the brain to compensate for visual information through mechanisms of brain plasticity triggered by training. Visual deprivation does not cause a cognitive spatial deficit since blind people are able to acquire spatial knowledge about the environment. However, this...
Article
Purpose: Oxygen plays a central role in multiple physiological and pathophysiological processes, and retinal oxygen supply has been found to be an important factor in many ocular diseases. Animal models are often used to study the pathophysiological mechanisms of diseases, especially non-human primates (NHP) due to their great similarities with hum...
Preprint
Full-text available
For blind individuals, tactile maps are useful tools to form cognitive maps through touch. However, they still experience challenges in cognitive map formation and independent navigation. Three-dimensional (3D) tactile information is thus increasingly being considered to convey enriched spatial information, but it remains unclear if it can facilita...
Preprint
Full-text available
For blind individuals, tactile maps are useful tools to form cognitive maps through touch. However, they still experience challenges in cognitive map formation and independent navigation. Three-dimensional (3D) tactile information is thus increasingly being considered to convey enriched spatial information, but it remains unclear if it can facilita...
Article
Full-text available
Even though vision is considered the best suited sensory modality to acquire spatial information, blind individuals can form spatial representations to navigate and orient themselves efficiently in space. Consequently, many studies support the amodality hypothesis of spatial representations since sensory modalities other than vision contribute to t...
Article
Full-text available
Among the deficits in visual processing that accompany healthy aging, the earliest originate in the retina. Moreover, sex-related differences in retinal function have been increasingly recognized. To better understand the dynamics of the retinal aging trajectory, we used the light-adapted flicker electroretinogram (ERG) to functionally assess the s...
Article
Full-text available
Fetal alcohol spectrum disorder (FASD) is a chronic debilitating condition resulting in behavioral and intellectual impairments and is considered the most prevalent form of preventable mental retardation in the industrialized world. We previously reported that 2-year-old offspring of vervet monkey (Chlorocebus sabeus) dams drinking, on average, 2.3...
Article
Full-text available
Deductive reasoning and working memory are integral parts of executive functioning and are important skills for blind people in everyday life. Despite the importance of these skills, the influence of visual experience on reasoning and working memory skills, as well as on the relationship between these, is unknown. In this study, fifteen participant...
Article
Full-text available
In the course of evolution, animals have obtained the capacity to perceive and encode their environment via the development of sensory systems such as touch, olfaction, audition, and vision [...]
Article
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The endocannabinoid (eCB) system has been found in all visual parts of the central nervous system and plays a role in the processing of visual information in many species, including monkeys and humans. Using anatomical methods, cannabinoid receptors are present in the monkey retina, particularly in the vertical glutamatergic pathway, and also in th...
Article
The brain operates through the synaptic interaction of distant neurons within flexible, often heterogeneous, distributed systems. Histological studies have detailed the connections between distant neurons, but their functional characterization deserves further exploration. Studies performed on the corpus callosum in animals and humans are unique in...
Article
Full-text available
Recent studies using full-field electroretinography (ffERG) that triggers a non-specific mass response generated by several retinal sources have attributed an important role for cannabinoid receptors in mediating vision in primates. Specific cone-mediated responses evoked through the photopic flicker ERG appear to be a better way to validate the as...
Article
Full-text available
Vision loss early in life has dramatic consequences on the organization of the visual system and hence on structural plasticity of its remnant components. Most of the studies on the anatomical changes in the brain following visual deprivation have focused on the re-organization of the visual cortex and its afferent and efferent projections. In this...
Article
Full-text available
The expression of the endocannabinoid (eCB) system, including cannabinoid receptor type 1 (CB1R) and the cannabinoid synthesizing (NAPE-PLD) and degrading (FAAH) enzymes, has been well-characterized in the retina of rodents and monkeys. More recently, the presence of CB1R was localized throughout the dorsal lateral geniculate nucleus of the thalamu...
Poster
Objective: In this study, we investigate the potential of 3D printed tactile maps to assist blind individuals in generating a cognitive map of their environment. The aim of the study is to determine if 3D printing can have a real advantage over traditional methods to promote its implementation in rehabilitation services and to improve navigation fo...
Article
Full-text available
Vision loss has dramatic repercussions on the quality of life of affected people, particularly with respect to their orientation and mobility. Many devices are available to help blind people to navigate in their environment. The EyeCane is a recently developed electronic travel aid (ETA) that is inexpensive and easy to use, allowing for the detecti...
Article
Full-text available
Blind individuals often report difficulties to navigate and to detect objects placed outside their peri-personal space. Although classical sensory substitution devices could be helpful in this respect, these devices often give a complex signal which requires intensive training to analyze. New devices that provide a less complex output signal are th...
Article
Full-text available
The loss or absence of vision is probably one of the most incapacitating events that can befall a human being. The importance of vision for humans is also reflected in brain anatomy as approximately one third of the human brain is devoted to vision. It is therefore unsurprising that throughout history many attempts have been undertaken to develop d...
Article
Neuroimaging with functional MRI (fMRI) identifies activated and deactivated brain regions in task-based paradigms. These patterns of (de)activation are altered in diseases, motivating research to understand their underlying biochemical/biophysical mechanisms. Essentially, it remains unknown how aerobic metabolism of glucose to lactate (aerobic gly...
Article
Full-text available
Significance Axons, the brain’s communication cables, have been described as cylinders since their discovery in 1860. Their structure is linked to how fast they conduct signals and is thus indicative of brain health and function. Here, we demonstrate an interplay between the micromorphology of axons and other extra-axonal structures, showing that a...
Article
Full-text available
In congenital blindness (CB), tactile, and auditory information can be reinterpreted by the brain to compensate for visual information through mechanisms of brain plasticity triggered by training. Visual deprivation does not cause a cognitive spatial deficit since blind people are able to acquire spatial knowledge about the environment. However, th...
Article
Full-text available
The ubiquitous distribution of the classic endocannabinoid system (cannabinoid receptors CB1 and CB2) has been demonstrated within the monkey nervous system, including the retina. Transient receptor potential vanilloid type 1 (TRPV1) is a cannabinoid-like non-selective cation channel receptor that is present in the retina and binds to endovannilloi...
Preprint
Full-text available
Axonal conduction velocity, which ensures efficient function of the brain network, is related to axon diameter. Non-invasive, in vivo axon diameter estimates can be made with diffusion magnetic resonance imaging, but the technique requires 3D validation. Here, high resolution, 3D synchrotron X-ray Nano-Holotomography images of white matter samples...
Article
Full-text available
Despite the fact that complete visual deprivation leads to volumetric reductions in brain structures associated with spatial learning, blind individuals are still able to navigate. The neural structures involved in this function are not fully understood. Our study aims to correlate the performance of congenitally blind individuals (CB) and blindfol...
Article
Full-text available
After publication of this paper, the authors determined an error in Fig. 4. Below is the correct Fig. 4.
Article
Full-text available
We investigated the effects of blindness on the structural and functional integrity of the corpus callosum and the anterior commissure (AC), which together form the two major components of the commissural pathways. Twelve congenitally blind (CB), 15 late blind (LB; mean onset of blindness of 16.6 ± 8.9 years), and 15 matched normally sighted contro...
Article
Full-text available
The frontal lobe is central to distinctive aspects of human cognition and behavior. Some comparative studies link this to a larger frontal cortex and even larger frontal white matter in humans compared with other primates, yet others dispute these findings. The discrepancies between studies could be explained by limitations of the methods used to q...
Article
Full-text available
In congenitally blind individuals, the occipital cortex responds to various nonvisual inputs. Some animal studies raise the possibility that a subcortical pathway allows fast re-routing of tactile information to the occipital cortex, but this has not been shown in humans. Here we show using magnetoencephalography (MEG) that tactile stimulation prod...
Article
Full-text available
The dorsal hippocampal commissure (DHC) is a white matter tract that provides interhemispheric connections between temporal lobe brain regions. Despite the importance of these regions for learning and memory, there is scant evidence of a role for the DHC in successful memory performance. We used diffusion-weighted magnetic resonance imaging (DW-MRI...
Article
Full-text available
Whether brain networks underlying the multimodal processing of language in humans are present in non-human primates is an unresolved question in primate evolution. Conceptual awareness in humans, which is the backbone of verbal and non-verbal semantic elaboration, involves intracerebral connectivity via the inferior fronto-occipital fascicle (IFOF)...
Article
There is ongoing controversy regarding the role of rapid eye movements (EMs) during rapid eye movement (REM) sleep. One prevailing hypothesis is that EMs during REM sleep are indicative of the presence of visual imagery in dreams. We tested the validity of this hypothesis by measuring EMs in blind subjects and correlating these with visual dream co...
Article
Full-text available
Two main types of cortical terminals have been identified in the cat thalamus. Large (type II) have been proposed to drive the response properties of thalamic cells while smaller (type I) are believed to modulate those properties. Among the cat’s visual cortical areas, the anterior ectosylvian visual area (AEV) is considered as one of the highest a...
Article
Full-text available
Background Preclinical studies in rodents have demonstrated inhibitory effects of glucagon-like peptide-1 (GLP-1) receptor stimulation on alcohol consumption. The effects of GLP-1 receptor stimulation on alcohol intake in primates have not been investigated. Methods We performed placebo-controlled studies on the effects of the GLP-1 receptor agoni...
Chapter
The tongue display unit (TDU) is a sensory substitution device that translates visual images into electrotactile stimulation that is transmitted to the tongue and leads to new perceptual skills following training. Trained users, including blind individuals, become capable of orientation discrimination, motion detection, shape recognition and they c...
Article
Sensory substitution and augmentation devices are built to try to replace or enhance one sense by using another sense. For example, in tactile–vision, stimulation of the skin driven by input to a camera is used to replace the ordinary sense of vision that uses our eyes. The feelSpace belt aims to give people a magnetic sense of direction using vibr...
Preprint
Full-text available
The dorsal hippocampal commissure (DHC) provides inter-hemispheric connections between temporal lobe brain regions but there is scant evidence of a role for the DHC in successful memory performance. We used diffusion-weighted MRI (DW-MRI) and white matter tractography to reconstruct the DHC across both humans and nonhuman primates, and show close c...
Article
Exposure to ethanol in utero leads to several brain development disorders including retinal abnormalities whose underlying cellular pathogenesis remains elusive. We recently reported that fetal alcohol exposure (FAE) in vervet monkeys induces anomalies of full-field electroretinogram (ERG) waveforms that suggest premature aging of the retina. The g...
Article
Full-text available
Because the human brain consumes a disproportionate fraction of the resting body’s energy, positron emission tomography (PET) measurements of absolute glucose metabolism (CMR glc ) can serve as disease biomarkers. Global mean normalization (GMN) of PET data reveals disease-based differences from healthy individuals as fractional changes across regi...
Data
Figure S1: voxel-to-voxel correlations of qCMRglc in gray matter of the human brain. Figure S2: voxel-to-voxel correlations of qCMRglc in white matter of the human brain. Figure S3: thresholded t-maps of metabolic variations in disorders of consciousness. Figure S4: thresholded t-maps of metabolic variations in anesthetic sedation. Figure S5: thres...
Article
Full-text available
Extensive rodent literature suggests that the endocannabinoid (eCB) system present in the nucleus accumbens (NAc) modulates dopamine (DA) release in this area. However, expression patterns of the cannabinoid receptor type 1 (CB1R), the synthesizing enzyme N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD), and the degradation enzyme fatty a...
Article
Background: Saccades are rapid and abrupt eye movements that allow us to change the point of fixation very quickly. Saccades are generally made to visual points of interest, but we can also saccade to non-visual objects that attract our attention. While there is a plethora of studies investigating saccadic eye movements to visual targets, there is...
Chapter
Classic neuroanatomy teaches that the brain can be divided into five lobes with distinct sensory functions, and a couple small areas of the brain that integrate the information from the different senses. Studies into the plasticity in the blind brain have revealed that the occipital cortex is not solely reserved for visual functions. Congenitally,...
Chapter
Full-text available
This chapter reviews the most recent advances in sensory substitution and the neural correlates of navigation in congenital blindness. Studies have established the superior ability of congenitally blind (CB) participants with the aid of Sensory Substitution Devices (SSDs) to navigate new environments and detect the size and shape of obstacles in or...
Article
Full-text available
Purpose: Fetal alcohol spectrum disorder (FASD) is a developmental disease characterized by behavioral problems and physical defects including malformations of the eye and associated optical defects. How these malformations affect retinal functioning is not well known, although animal models have suggested that scotopic vision is particularly defi...
Article
We have shown that congenitally blind individuals are more sensitive to painful heat compared to their sighted counterparts. This hypersensitivity might be at least partly mediated by psychological and cognitive factors, such as pain expectation and anxiety. Here we investigate whether uncertainty about the intensity of a pending painful stimulus a...
Article
The loss of vision, particularly when it occurs early in life, is associated with compensatory cortical plasticity not only in the visual cortical areas, but throughout the entire brain. The absence of visual input to the retina can also induce changes in entrainment of the circadian rhythm, as light is the primary zeitgeber of the master biologica...
Article
The parietal lobe has a unique place in the human brain. Anatomically, it is at the crossroad between the frontal, occipital, and temporal lobes, thus providing a middle ground for multimodal sensory integration. Functionally, it supports higher cognitive functions that are characteristic of the human species, such as mathematical cognition, semant...
Article
Full-text available
There is ample evidence that the occipital cortex of congenitally blind individuals processes nonvisual information. It remains a debate whether the cross-modal activation of the occipital cortex is mediated through the modulation of preexisting corticocortical projections or the reorganisation of thalamocortical connectivity. Current knowledge on...
Article
As light plays an important role in the synchronisation of the internal biological clock to the environmental day/night schedule, we compared the 24-h profiles of biological circadian markers in blind and normal sighted individuals. Salivary melatonin and cortisol concentrations were collected every two hours in eleven blind subjects, reporting no...
Article
Full-text available
Research in blind individuals has primarily focused for a long time on the brain plastic reorganization that occurs in early visual areas. Only more recently, scientists have developed innovative strategies to understand to what extent vision is truly a mandatory prerequisite for the brain’s fine morphological architecture to develop and function....
Article
Full-text available
Fetal alcohol exposure (FAE) alters hippocampal cell numbers in rodents and primates, and this may be due, in part, to a reduction in the number or migration of neuronal progenitor cells. The olfactory bulb exhibits substantial postnatal cellular proliferation and a rapid turnover of newly formed cells in the rostral migratory pathway, while produc...