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The question of how the mind works is at the heart of cognitive science. It aims to understand and explain the complex processes underlying perception, decision-making and learning, three fundamental areas of cognition. Bayesian Brain Theory, a computational approach derived from the principles of Predictive Processing (PP), offers a mechanistic and mathematical formulation of these cognitive processes. This theory assumes that the brain encodes beliefs (probabilistic states) to generate predictions about sensory input, then uses prediction errors to update its beliefs. In this paper, we present an introduction to the fundamentals of Bayesian Brain Theory. We show how this innovative theory hybridizes concepts inherited from the philosophy of mind and experimental data from neuroscience, and how it translates complex cognitive processes such as perception, action, emotion, or belief, or even the psychiatric symptomatology., (Copyright © 2021 L'Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.)

An appraisal mission regarding the repair of physical injury is based on the classification of the effects of injury and scales. These scales are surprisingly incomplete concerning the symptoms due to a right hemisphere injury. However, these symptoms can cause an important handicap in numerous activities, social, affective and professional. This paper reviews the recent functional anatomic knowledge of the right hemisphere functions, visuo-spatial cognition, intentional process and social cognition. The impacts of this appraisal data, as well as suggestions for new scales, are outlined., (Copyright © 2017. Published by Elsevier Masson SAS.)

The first part of this paper describes the long history of the concept of Mindfulness. Contrary to the belief that Mindfulness only has Buddhist and Hindu origins, it is also rooted in Jewish, Islamic and Christian religions. Furthermore, western philosophers have described a mindful path to become more aware of thoughts, feelings, and bodily sensations. Mindfulness can be considered as a universal human ability embodied to foster clear thinking and open-heartedness. As such, this form of being requires no particular religious or cultural belief system. The current acceptance of what a mindful path is, refers to a psychological quality that involves bringing one's complete attention to present experience on a moment-to-moment basis, in a particular way: in the present moment, and nonjudgmentally. Although such a definition is well accepted in France, the French translation for Mindfulness is not easy to use: being conscious and being aware are translated with the same French word. The French language fails to clearly separate the dimensional attributes of a mindful subject from the ways for developing mindfulness through formal meditation practice. In line with this conception, stability and assessments of Mindfulness mainly were examined. How this disposition allows the development of concentration, attention and acceptance moment by moment in a nonjudgmental way is described in the second part. Particular attention is paid to its positive effects in several aspects of mental and physical health. In particular, positive effects on the ability to cope with stress are described from a physiological point of view. Third, this article intends to present neurobiological aspects currently proposed to explain the benefits of Mindfulness meditation. Modifications of cerebral networks and neurobiological functioning are described in relation to expertise in meditation practice. The hypothesis of the role of meditation on neuroplasticity is also discussed. Furthermore, the specific impact of Mindfulness meditation practice on these mechanisms will be considered in comparison with relaxation techniques. With the increasing growth of well-designed and well-controlled meditation research, however, future studies will be needed to compare between different meditation techniques. This will enable researchers to outline the effects of the technique-specific differences on behavior, cognitive function, underlying physiology and neurobiology and clinical effectiveness. Finally, the most recent data on the changes in functioning of a resting brain (Brain Default Mode) induced by a Mindfulness practice, demonstrate differences in the default-mode network that are consistent with decreased mind-wandering. That is a way to better understand possible neural mechanisms of meditation for health benefits of Mindfulness., (Copyright © 2014 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.)

Introduction: Executive function impairments and high level of impulsivity may constitute heritable endophenotypes that confer predisposition for alcohol dependence. Brain volume abnormalities have also been reported in young, alcohol-naïve subjects at high risk (HR) for alcohol dependence, and linked to cognitive dysfunction., Methods: This paper presents a literature review of magnetic resonance imaging (MRI) studies that examined brain volumes in adolescent/young adult HR offspring from families with multiple cases of alcohol dependence compared to low risk controls with no family history of alcohol or drug misuse. In some of these studies, executive functioning and externalizing symptoms were also assessed., Results: In HR subjects, local white matter volume deficits were found in the corpus callosum and in the right orbito-frontal cortex, and lower fractional anisotropy in the left inferior longitudinal fasciculus and in the right optic radiation. Altered fronto-cerebellar connectivity has also been reported. Diminished gray matter volume of the cerebellar cortex was found in HR subjects, in the frontal, cyngulate and para-hippocampal gyri, and also in the amygdala, the thalamus and the cerebellum. These structural abnormalities have been associated with higher impulsivity level and executive function impairments, themselves markers of vulnerability to alcoholism. These premorbid cerebral abnormalities may increase the risk for developing an alcohol use disorder in HR subjects through atypical control processing., Conclusion: Brain abnormalities may potentially constitute an abnormal neural network that might underlie the risk towards alcohol dependence. These circuitry abnormalities might contribute to the reward deficiency, as well as impaired response inhibition that predict impulsive spectrum behavior, which are thought to represent the inherited vulnerability to alcohol dependence in HR individuals., (Copyright © 2013 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.)

Until recent years, brain applications of (31)P magnetic resonance spectroscopy were poor. Arising of clinical high field strength magnets (three Tesla) as well as dedicated brain coils (eg: bird cage), using specific and useful sequences providing appropriate spatial localisation and signal to noise ratio brought highlights on multinuclear spectroscopy. Better understanding of brain metabolism emphasizes the role of phosphoenergetic compounds and its potential issues in tumoral, metabolic and degenerative diseases. In the present paper, we report 1 year of experience and preliminary results for 40 patients as well as review of the literature. By successive in vivo determination and quantitation of numerous metabolites it allows, multinuclear spectroscopy may provide additional information to biomathematical models of brain metabolism., (Copyright 2009. Published by Elsevier Masson SAS.)

The number of structural neuroimaging studies of bipolar disorder have increased during recent years, expanding the literature on the nature of cerebral abnormalities underlying this disorder. The purpose of this paper is to provide a selective review on the main issues concerning this literature. Consistent findings are higher rate of periventricular and deep subcortical white matter hyperintensites seen on MRI. Although there is strong evidence for links between hyper-intense lesions and age or cardio-vascular risk factors, some authors have observed the presence of these abnormalities early in the course of the illness. There are also frequent reports on ventricular enlargement, which has been described as mild and predominant in the right lateral ventricle. Total cerebral volume appears to be preserved. Whereas changes in total grey matter volume are uncertain, evidence suggests that reduced white matter volume reflects genetic factors predisposing to the disorder. Recent studies have reported volume changes in several cortical areas including the subgenual cingular, frontal and temporal cortices. Additionally, a number of reports described morphometric abnormalities in various subcortical structures, such as amygdala, basal ganglia and thalamus. Part of the variability in the morphometric abnormalities might be attributable to differences in clinical status and demographic characteristics of patient groups. Despite some inconsistencies across the studies, it emerges that abnormalities are asymmetrically distributed throughout the two cerebral hemispheres. When increase in volume is reported, it is preferentially localised in the left cerebral hemi-sphere and more specifically in prefrontal and temporal cortices and in amygdala. By contrast, when structural abnormalities concern the right cerebral hemisphere, they are identified as deficits. These latter results are in direct line with those of studies of mania following brain injuries, which report that these secondary mania result mainly from right cerebral lesions. It is also important to notice that most of the abnormalities concern both the cortical and subcortical level, ie frontal, striatal, thalamic and limbic regions. These abnormalities highlight the role in the pathophysiology of bipolar disorder of the loops involved in emotional information processing. The particular role of fronto-limbic loops in the phenomenology of bipolar disorder have been emphasised by recent data from functional neuroimaging studies.

Following a previous paper describing how memory appeared in the nervous system in mammalians, during evolution, and how its significant growth led to hominization, the present paper intends to show the prevailing place it occupies in human brain. Memory, an attribute of cortex, is an engraving of neuronal circuits created during information analysis of data input in the cortex. It is created either by repetition of information or by increase in brain activity, under the influence of a central brain system. In the brain of human newborns, immature and unprogrammed, but endowed with a great capacity for learning, the whole organization and programming will be possible through learning and remembering. Communication pathways between functions are memory pathways. Brain becomes a memory machine and every cortical area is a memory territory. Its lesion results in a disturbance corresponding exactly to forgetting what has been stored in that territory.

Over the last years, technical advances in neuroimaging have allowed drastic improvements in the assessment of acute ischemic cerebral events. Beyond conventional morphological analysis, diffusion-weighted and perfusion-weighted MRI now enable routine functional assessment of brain tissue; spectroscopy and diffusion tensor imaging still remains in the domain of clinical research. During acute ischemia events, diffusion-weighted MRI can detect the movements of water molecules and cytotoxic edema related to cell injury enabling rapid diagnosis and early assessment of cerebral ischemia. In conjunction with perfusion imaging, which detects hypoperfusion areas, diffusion-weighted MRI provides a means to identify areas of penumbra ischemia. More recent multislice computed tomographic (CT) scans with multimodal analysis are also very competitive for assessment of cerebral ischemia (non-enhanced CT, CT angiography and perfusion CT). The purpose of this paper is to describe the CT and MRI patterns during the different stages of cerebral infarcts.

The clinical value of MR spectroscopy is now well established and this technique has been added to the current French classification of medical acts (CCAM). This paper presents a set of normal control values for 3 metabolite ratios obtained using a PRESS sequence with a TE of 135 ms at 1.5T: NAA/Cho, NAA/Cr and Cho/CR. Spectroscopy data acquisition were obtained from the following 12 anatomical regions: parieto-occipital white matter, centrum semiovale, frontal white matter, thalamus, basal ganglia, cerebellum (hemisphere, including dentate nucleus), brain stem (including pons, medulla and midbrain), anterior and posterior temporal lobe, parietal, occipital and pre-frontal cortices. The presented data allow radiologists equipped with a similar MR system to implement a clinical spectroscopy program without undergoing research protocols in order to obtain control values.

Since the last thirty Years, scientific study of the cerebral substrate of consciousness has been marked by significant achievements, resulting in part from a rich interaction between the exploration of cognition in both brain-damaged patients and healthy subjects. Several neuropsychological syndromes contain spectacular dissociations which permit to identify principles related to the neurophysiology of consciousness. The generality of those principles can then be evaluated in the healthy subject using the combination of experimental psychology paradigms, and functional brain-imaging tools. In this paper, we review some of the recent results relevant to visual phenomenal consciousness, which is the most scientifically investigated aspect of consciousness. We isolate several of those general principles through the exploration of neuropsychological syndromes such as "blindsight", visual agnosias and neglect, and expose how their generality has been demonstrated in the healthy subject using conditions such as visual illusions or subliminal perception. Finally, we describe the bases of a scientific model of consciousness, based on the concept of a "global workspace", which takes into account the data reviewed.

In systemic diseases, brain biopsy is an exceptional diagnostic procedure which must be restricted to those rare forms involving only the central nervous system, at least clinically, and when a treatable disease is suspected the treatment of which requires a precise histological diagnosis. According to the clinical presentation and radiological appearance, an open biopsy or a stereotactic biopsy under radiological control will be proposed. In this paper, will be reviewed the indications and neuropathological findings in systemic amyloidoses extending to the central nervous system, cerebral angiitis, sarcoidosis, Whipple's disease, Langerhans'cell as well as non-Langerhans'cell systemic histiocytoses and paraneoplastic encephalomyelitis.

This paper reports the clinico-pathological data in a French family with orthochromatic leukodystrophy. The parents were first cousins and had seven children. Among those, two sisters and one brother presented with neurological signs, with onset around the 5(th) decade, including a dementing syndrome of frontal type, a tetrapyramidal syndrome, seizures, and, in one sibling, a cerebellar syndrome. CT scan or MRI showed diffuse involvement of the white matter. The neurological signs worsened progressively leading to death within 11 and 22 months. Neuropathological examination was performed in two cases. It revealed characteristic orthochromatic leukodystrophy. In one case, the presence of pigmented macrophages and astrocytes was suggestive of Van Bogaert and Nyssen disease. However there were some atypical features including the absence of pigmented cells in the second case whose clinical course was shorter, and the cavitary appearance of the white matter changes with a relative increase in the number of oligodendrocytes raising the issue of a possible link between this condition and cavitary orthochromatic leukodystrophies.

In recent years research on the neuronal substrate for mental disorders has considerably developed thanks to new brain imaging methods. Functional brain imaging has attracted several workers in their investigations of psychiatric diseases. Some authors have addressed the position of imaging in the diagnosis and, above all, prognosis of acute psychotic disorders. In the following paper, the authors review the published results. Both structural and functional imaging confirm the hypothesis of a neurophysiological contribution to acute psychotic disorders, as shown by ventricular dilatation and functional abnormalities. Nonetheless, imaging does not seem to have a precise and absolute diagnostic and prognostic value, although of undeniable heuristic interest.

A good knowledge of the brain anatomy is necessary for all physicists interested in neurologic pathology, and especially for the radiologists. The aim of this paper is to summarize the important data in morphological but also in functional brain anatomy. The main neurologic pathways are represented on MR standard slices for practical application. The international anatomica nomenclatura (french terms) is used.

The concept of addiction is increasingly bound to a general model of heterogeneous and polymorphous dependences. In this paper we examine upstream what could found this universal addictive principle, asking the question of the neurobiological root of addictivity. In other words, is the root of our brain working in an addictive way? To answer affirmatively to this question we gather two sets of datas: firstly, the conditions of the brain addictivity and secondly, the brain mechanisms that suggest this kind of addictive working. These datas are common if we consider them one by one, but their synthesis in a bundle of heuristic clues could be interesting to examine and to submit to thought. The model we suggest proposes that the architecture of our brain and the type of functioning of our neurones, imply the presence of a natural addictive set of problems in all human beings, between a fight against cerebral background noise--a dysphoric source--and a stimulation need. Finally, considering some neurobiological data in the last five years, we propose a triangular model of the addict brain, that involves three associated systems: "arousal" system, "liking" system and "wanting" system. This model, supported by the sensation seeking one, will allow us to suggest an explanation of the processes that lead to pathological addictions, according to the principles of a natural and universal addictivity.

We describe in this paper how the STEAM sequence can be an efficient tool to obtain images free of flow artifacts in anatomical situation where the spin echo failed. The simplest way to eliminate flow artifacts is to exploit the dephasing induced by motion in magnetic field gradients and to reduce to zero the signal from moving tissues. This can be achieve by increasing the time elapsed between the spin excitation and the signal observed. Because of T2 relaxation, such an increase results in a signal decrease when the spin echo sequence is used. The STEAM sequence has the unique property that the time elapsed between observation and excitation can be increased without change in T2 value and so allows a good suppression of signals from the moving spins with short TE. Our results demonstrate that, although the stimulated echo intensity is only half that of a spin echo taken at the same read out time, the advantages of STEAM imaging can compensate for this partial loss in signal to noise in some particular clinical situations. The influence of mixing time on contrast has been evaluated using thoracic spine imaging and it has been shown that contrast between spine and CSF can be significantly improved (+ 60%) when TM is increased (from 17 ms to 50 ms). In the same time, the contrast between spine and fat issue decreases (40%). This last effect facilitates the adjustment of contrast window. Suppression of motion artifacts has first been evaluated with thoracic spine imaging, using a whole body coil. Suppression of artifacts was better than that obtained with a flow compensated spin echo sequence, especially in the case of kyphotic patients when a presaturation band was inefficient. In a second step suppression of motion artifacts has been evaluated from posterior fossa examination after injection of a paramagnetic contrast agent. The images obtained with the stimulated echo sequence show a dramatic reduction of signal from blood in the lateral sinus, and therefore an increase of quality by elimination of motion artifacts.

This brief overview summarises the literature regarding the effects of lesions of the basal ganglia (BG) on brain metabolism-an index of integrated synaptic activity. Interest in this field is because to show such effects may reveal the implication of neuron networks, damaged at the level of the BG, in the neuropsychological and behavioural expression of BG lesions. As an illustration of this, a parallel is drawn between the loss of psychic self-activation (also named "psychic akinesia" or "athymhormia") that follows bilateral lesions at variable sites of the prefrontal-striatal-pallidal-thalamic loop on one hand, and the mild prefrontal hypometabolism consistently observed in such cases. This paper also reviews the changes in brain metabolism found in progressive supranuclear palsy, Huntington's disease, Parkinson's disease, Wilson's disease and striato-nigral degeneration.

The perivascular spaces of the central nervous system are involved in various pathological situations. The aim of this paper is to focus on the histopathological lesions of the perivascular spaces which commonly occur in the infectious (bacterial, viral, parasitic), tumoral (carcinoma, lymphoma, leukemia), demyelinating (multiple sclerosis, allergic encephalomyelitis) and vascular diseases of the brain. According to their apparent function in each of these situations an attempt was made to classify the main physiopathological processes involving the perivascular spaces into 3 distinct groups. The perivascular spaces may be considered as follows: (1) double way route between the parenchyma and the leptomeningeal space (extension to the brain of a meningeal pathological process, drainage of parenchymal wastes); (2) elective location of the inflammatory reaction partly as a result of the presence of connective tissue; (3) site of particular lesions such as dilatation, the pathogenesis of which remains unclear.

The term lacunae was first used by Dechambre (1838) referring to small cavities developed during the process of resorption within cerebral softenings. Some years later, lacunae was applied by Durand-Fardel (1843) to small cavities located in the basal ganglia and hypothetically attributed to old, healed cerebral softenings. Durand-Fardel (1842, 1854) described "l'état criblé" as many round small holes ("criblures") always containing a patient blood vessel and located in the hemispheric white matter. He believed that "état criblé" was caused by mechanical compression of cerebral tissue related to the dilatation of the blood cerebral vessels during repetitive cerebral congestion. Chronic dementia or delirium were considered as the clinical counterpart of "état criblé". In the second half of the XIXth century, the few reports about lacunae were confusing due to the imprecise use of the terms "lacunae" and "état criblé". Furthermore, some authors described lacunae as sequelae of haemorrhage, others as old softenings or both. In the beginning of the XXth century, the masterly work of P. Marie (1901) established a clear distinction between the "foyers lacunaires de désintégration" and "état criblé" de Durand-Fardel or single perivascular dilatation of one of the lenticulo-striate arteries at its entrance into the lenticular nucleus or post-mortem charges (cerebral porosity, "état de fromage de gruyère"). He described lacunae as small cerebral softenings caused by occlusion of the blood vessels by a "local arteriosclerotic process". However, he also stated that some lacunae containing a patent blood vessel were due to a perivascular space dilatation destroying the adjacent brain parenchyma by a process of "destructive vaginalitis". Marie observed that lacunae were frequently clinically asymptomatic, but "that the hemiplegia of the old people was more often due to cerebral lacunae than to cerebral haemorrhage or softening". During the first half of the XXth century, all the papers devoted to cerebral lacunae were in accordance with the work of P. Marie, developing his own's contradictions. Many authors emphasized the "destructive vaginalitis way" and claimed that lacunae were dilatations of the perivascular spaces. Many other authors developed the "softening way" masterfully illustrated by Fisher who considered lacunae as small deep infarcts caused by a specific pathological process of lipohyalinosis due to arteriolar wall modification by hypertensive disease.(ABSTRACT TRUNCATED AT 400 WORDS)