1,721,124 research outputs found
Right hemisphere developmental learning disability: A case study
No full textWe report a case study of a 22-year-old man with a developmental learning disorder consisting of arithmetic difficulties, visuo-spatial deficits and emotional difficulties. Language abilities and verbal learning were remarkably spared. The clinical picture was consistent with the diagnosis of 'Right Hemisphere Developmental Learning Disability' (RHDLD) as described by Weintraub and Mesulam (Archives of Neurology 1983; 40: 463-8). Computed tomography and magnetic resonance imaging scans were normal, but a positron emission tomography scan revealed a marked hypometabolism of the right hemisphere, supporting the claim that RHDLD is indeed associated with functional abnormalities of the right hemisphere
Reduced grey matter in the posterior insula as a structural vulnerability or diathesis to addiction.
No full textA number of neuroimaging studies have shown that drug addiction is associated with morphological differences in several brain areas, including orbito-frontal and limbic structures. Most of these studies have investigated patients with addiction to cocaine. The neurobiological mechanisms which play a role in drug addiction are not fully understood, however, and the causal factors remain under investigation. The present study investigated morphological differences between patients with history of cocaine (N=14) and heroin (N=24) abuse and healthy matched controls (N=24). A 3D T1W MRI scan was acquired for all participants and the grey matter images of each patient group compared with those of controls. A direct comparison of the two addiction groups was also carried out. When compared with controls cocaine dependent patients had lower grey matter values in the left middle occipital gyrus, right putamen and insula, whereas heroin abusers had lower grey matter values in the right insula. The direct comparison between the two addiction groups showed that cocaine abusers had less grey matter in the right posterior cingulate, medio-temporal and cerebellar regions, whereas heroin abusers showed less grey matter in parietal regions on both sides, including postcentral gyrus and inferior parietal lobule. Reduced right posterior insular cortex was commonly found in both cocaine and heroin dependent patients. This morphological difference might represent a structural marker of addiction, which is independent of the discrete regional effects of each psychotropic substance of abuse, and might constitute a possible neurobiological vulnerability or diathesis to addiction. Equally, the discrete structural differences emerging from the direct comparison of cocaine and heroin abusers might reflect the effects of differential drug binding in the brain and/or express a form of neurobiological vulnerability which might explain individual drug choice
Accidental choke cherry poisoning: Early symptoms and neurological sequelae of an unusual case of cyanide intoxication
No full textWe report the case of a 56-year-old woman who was accidentally poisoned when size ingested choke cherries whose pulp contained cyanide, and describe the acute clinical picture, the neurological sequelae and the neuroradiological findings. After recovery from coma the patient showed signs of a parkinsonian syndrome, retrobulbar neuritis and sensory-motor neuropathy. MRI showed abnormal signal intensities involving the basal ganglia. Since no memory deficits were observed, we argue that the parkinsonian syndrome was caused by cyanide intoxication rather than by subcortical damage due to hypoxia
Structural and functional correlates of hypnotic depth and suggestibility
Full text linkThis study explores whether self-reported depth of hypnosis and hypnotic suggestibility are associated with individual differences in neuroanatomy and/or levels of functional connectivity. Twenty-nine people varying in suggestibility were recruited and underwent structural, and after a hypnotic induction, functional magnetic resonance imaging at rest. We used voxel-based morphometry to assess the correlation of grey matter (GM) and white matter (WM) against the independent variables: depth of hypnosis, level of relaxation and hypnotic suggestibility. Functional networks identified with independent components analysis were regressed with the independent variables. Hypnotic depth ratings were positively correlated with GM volume in the frontal cortex and the anterior cingulate cortex (ACC). Hypnotic suggestibility was positively correlated with GM volume in the left temporal-occipital cortex. Relaxation ratings did not correlate significantly with GM volume and none of the independent variables correlated with regional WM volume measures. Self-reported deeper levels of hypnosis were associated with less connectivity within the anterior default mode network. Taken together, the results suggest that the greater GM volume in the medial frontal cortex and ACC, and lower connectivity in the DMN during hypnosis facilitate experiences of greater hypnotic depth. The patterns of results suggest that hypnotic depth and hypnotic suggestibility should not be considered synonyms
Neuroimaging resolution of the altered state hypothesis
Full text linkA controversy in the field of hypnosis has centered on the question of whether there is a uniquely hypnotic state of consciousness and, if so, whether it is causally related to responsiveness to suggestion. Evidence from brain imaging studies has been used to support claims for various altered state hypotheses, without resolving the debate. The designs of many neuroimaging studies confound the induction of hypnosis with the suggestions that can be given in or out of hypnosis, thus rendering them incapable of resolving the controversy. Brain imaging studies that do not have this confound support the hypothesis that hypnotic inductions produce changes in brain activity, but also indicate that these changes are not required for the experience of hypnotic suggestions or their neural correlates. The data remain equivocal as to whether there is a causal relation between the changes in brain activity produced by hypnotic inductions and those produced by other suggestions. It also remains uncertain whether the changes in activation produced by hypnotic inductions reflect a uniquely hypnotic state as opposed to more mundane processes
Left mediotemporal structures mediate the retrieval of episodic autobiographical mental images.
No full textThe aim of this functional magnetic resonance imaging (fMRI) study was to investigate the neuroanatomical substrates associated with the process of mental generation of specific (i.e., exemplar) and episodic autobiographical (i.e., an image of a unique life episode connected with an object) images. The fMRI paradigm in this experiment included a non-image generation baseline and two activation conditions requiring the generation of either specific or episodic autobiographical images. Image generation times and brain activation were recorded. Behavioral results showed that generating specific mental images took significantly less than generating episodic autobiographical images. Individuals generated specific images that were well distinct from the episodic autobiographical ones, semantic in nature without an episodic reference. Episodic autobiographical images did not show a significant bias towards preferential retrieval from any particular life period but were retrieved from across the entire life span. Conjunction analysis of the fMRI data showed that the two image generation conditions significantly activated a common set of neural structures, including mediofrontal areas. This shared pattern of activation might be the result of an underlying similar format and characteristics (e.g., richness in details) between the two types of images and might reflect the involvement of similar cognitive processes. Distinct patterns of significant activation were also present. Activation in the right parietal regions, cuneus, precuneus and left temporal regions was associated solely with the generation of specific images. Regions more specifically devoted to episodic memory retrieval and imagery, such as the left parahippocampal gyrus and precuneus, and the posterior cingulate cortex bilaterally, were significantly activated exclusively by the generation of episodic autobiographical images
Impact of Lewy bodies disease on visual skills and memory abilities: from prodromal stages to dementia
Full text linkDementia with Lewy bodies (DLB) and its prodromal presentation with mild cognitive impairment is characterized by prominent deficits in attention/executive domains and in visual processing abilities with relative sparing of memory. Neuropsychological research is continuously refining the tools to define more in detail the patterns of relatively preserved and impaired cognitive abilities that help differential diagnosis between DLB and Alzheimer disease (AD). This review summarizes the main studies exploring specific cognitive tasks investigating different visual processing abilities and verbal memory that better differentiate DLB from AD. The findings provide evidence that substantial impairments in visual-spatial and visual-constructional abilities and relatively better performance on memory tasks that depend on hippocampal function characterize the prodromal stage of DLB. The ability to detect early indicators of prodromal DLB through clinical and cognitive assessments is the first step to guide instrumental diagnostic work-ups and provide the opportunity for early intervention
Hypnotic induction decreases anterior default mode activity
No full textThe 'default mode' network refers to cortical areas that are active in the absence of goal-directed activity. In previous studies, decreased activity in the 'default mode' has always been associated with increased activation in task-relevant areas. We show that the induction of hypnosis can reduce anterior default mode activity during rest without increasing activity in other cortical regions. We assessed brain activation patterns of high and low suggestible people while resting in the fMRI scanner and while engaged in visual tasks, in and out of hypnosis. High suggestible participants in hypnosis showed decreased brain activity in the anterior parts of the default mode circuit. In low suggestible people, hypnotic induction produced no detectable changes in these regions, but instead deactivated areas involved in alertness. The findings indicate that hypnotic induction creates a distinctive and unique pattern of brain activation in highly suggestible subjects
The ideation of movement is supported by fronto-temporal cortical regions involved in the retrieval of semantic knowledge.
No full textThe neurofunctional correlates of movement ideation, which should be distinguished from motor imagery, have not been fully investigated. This functional Magnetic Resonance Imaging (fMRI) experiment revealed the brain activation patterns associated with different motor processes, including ideation.Fifteen healthy participants underwent fMRI and performed three tasks using the right index finger: 1. execution of a simple prespecified movement; 2. execution of a simple voluntary movement; 3. ideation of a simple voluntary movement without execution. A number of t-test comparisons across conditions were carried out.The execution ofa simple prespecified finger movement activated the right inferior parietal cortex and substantia nigra, the left middle frontal gyrus, and thalamus, and bilaterally the post-central gyri, the superior parietal lobule and the cerebellum. Execution of a simple voluntary movement activated the left anterior cingulate cortex. The ideation of a voluntary simple movement activated the left inferior, middle and superior temporal gyri and the inferior frontal gyri bilaterally.The execution of a prespecified action involves structures within the somatosensory cortex, such as the post-central gyrus. The execution of a voluntary action is achieved with the support of the anterior cingulate cortex, a structure active when resolution of conflict is required. The ideation of a voluntary action requires the contribution of associative areas of the left frontal and temporal lobes, which support the retrieval of semantic knowledge necessary in the planning of a voluntary act
Individual differences in personality traits reflect structural variance in specific brain regions.
No full textPersonality dimensions such as novelty seeking (NS), harm avoidance (HA), reward dependence (RD) and persistence (PER) are said to be heritable, stable across time and dependent on genetic and neurobiological factors. Recently a better understanding of the relationship between personality traits and brain structures/systems has become possible due to advances in neuroimaging techniques. This Magnetic Resonance Imaging (MRI) study investigated if individual differences in these personality traits reflected structural variance in specific brain regions. A large sample of eighty five young adult participants completed the Three-dimensional Personality Questionnaire (TPQ) and had their brain imaged with MRI. A voxel-based correlation analysis was carried out between individuals' personality trait scores and grey matter volume values extracted from 3D brain scans. NS correlated positively with grey matter volume in frontal and posterior cingulate regions. HA showed a negative correlation with grey matter volume in orbito-frontal, occipital and parietal structures. RD was negatively correlated with grey matter volume in the caudate nucleus and in the rectal frontal gyrus. PER showed a positive correlation with grey matter volume in the precuneus, paracentral lobule and parahippocampal gyrus. These results indicate that individual differences in the main personality dimensions of NS, HA, RD and PER, may reflect structural variance in specific brain areas
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