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Prefrontal Areas (prefrontal + area)
Selected AbstractsInitial, habitual and compulsive alcohol use is characterized by a shift of cue processing from ventral to dorsal striatumADDICTION, Issue 10 2010Sabine Vollstädt-Klein ABSTRACT Aims During the development of drug addiction, initial hedonic effects decrease when substance use becomes habitual and ultimately compulsive. Animal research suggests that these changes are represented by a transition from prefrontal cortical control to subcortical striatal control and within the striatum from ventral to dorsal domains of the striatum, but only limited evidence exists in humans. In this study we address this hypothesis in the context of alcohol dependence. Design, setting and participants Non-abstinent heavy social drinkers (n = 21, 5.0 ± 1.5 drinks/day, 13 of them were alcohol-dependent according to DSM-IV) and light social drinkers (n = 10, 0.4 ± 0.4 drinks/day) were examined. Measurements We used a cue-reactivity functional magnetic resonance imaging (fMRI) design during which pictures of alcoholic beverages and neutral control stimuli were presented. Findings In the dorsal striatum heavy drinkers showed significant higher activations compared to light drinkers, whereas light social drinkers showed higher cue-induced fMRI activations in the ventral striatum and in prefrontal areas compared to heavy social drinkers [region of interest analyses, P < 0.05 false discovery rate (FDR)-corrected]. Correspondingly, ventral striatal activation in heavy drinkers correlated negatively with obsessive-compulsive craving, and furthermore we found a positive association between cue-induced activation in the dorsal striatum and obsessive-compulsive craving in all participants. Conclusions In line with our hypothesis we found higher cue-induced activation of the ventral striatum in social compared to heavy drinkers, and higher dorsal striatal activation in heavy drinkers. Increased prefrontal activation may indicate that social drinkers activate cortical control when viewing alcohol cues, which may prevent the development of heavy drinking or alcohol dependence. Our results suggest differentiating treatment research depending on whether alcohol use is hedonic or compulsive. [source] Reliving lifelong episodic autobiographical memories via the hippocampus: A correlative resting PET study in healthy middle-aged subjectsHIPPOCAMPUS, Issue 5 2008Pascale Piolino Abstract We aimed at identifying the cerebral structures whose synaptic function subserves the recollection of lifetime's episodic autobiographical memory (AM) via autonoetic consciousness. Twelve healthy middle-aged subjects (mean age: 59 years ± 2.5) underwent a specially designed cognitive test to assess the ability to relive richly detailed episodic autobiographical memories from five time periods using the Remember/Know procedure. We computed an index of episodicity (number of Remember responses justified by the recall of specific events and details) and an index of retrieval spontaneity, and additionally an index of semanticized memories (number of Know responses). The regional cerebral blood flow (rCBF) was measured in the resting state, with H2O15 as part of an activation PET study. The indexes were correlated with blood flow using volumes of interest in frontotemporal regions, including hippocampus and voxel-wise analyses in SPM. With both analyses, significant correlations were mainly found between the index of episodicity and rCBF in the medial temporal lobe, including hippocampus, across the five time periods (unlike the index of semanticized memories) and between the spontaneity index and rCBF in the prefrontal areas. These results highlight, in healthy subjects, the distinct role of these two structures in AM retrieval and support the view that the hippocampus is needed for reexperiencing detailed episodic memories no matter how old they are. © 2008 Wiley-Liss, Inc. [source] Neural correlates of consolidation in working memoryHUMAN BRAIN MAPPING, Issue 3 2007Nelly Mainy Abstract Many of our daily activities rely on a brain system called working memory, which implements our ability to encode information for short-term maintenance, possible manipulation, and retrieval. A recent intracranial study of patients performing a paradigmatic working memory task revealed that the maintenance of information involves a distributed network of oscillations in the gamma band (>40 Hz). Using a similar task, we focused on the encoding stage and targeted a process referred to as short-term consolidation, which corresponds to the encoding of novel items in working memory. The paradigm was designed to manipulate the subjects' intention to encode: series of 10 letters were presented, among which only five had to be remembered, as indicated by visual cues preceding or following each letter. During this task we recorded the intracerebral EEG of nine epileptic patients implanted in mesiotemporal structures, perisylvian regions, and prefrontal areas and used time,frequency analysis to search for neural activities simultaneous with the encoding of the letters into working memory. We found such activities in the form of increases of gamma band activity in a set of regions associated with the phonological loop, including the Broca area and the auditory cortex, and in the prefrontal cortex, the pre- and postcentral gyri, the hippocampus, and the fusiform gyrus. Hum Brain Mapp, 2007. © 2006 Wiley-Liss, Inc. [source] Neural substrates of tactile object recognition: An fMRI studyHUMAN BRAIN MAPPING, Issue 4 2004Catherine L. Reed Abstract A functional magnetic resonance imaging (fMRI) study was conducted during which seven subjects carried out naturalistic tactile object recognition (TOR) of real objects. Activation maps, conjunctions across subjects, were compared between tasks involving TOR of common real objects, palpation of "nonsense" objects, and rest. The tactile tasks involved similar motor and sensory stimulation, allowing higher tactile recognition processes to be isolated. Compared to nonsense object palpation, the most prominent activation evoked by TOR was in secondary somatosensory areas in the parietal operculum (SII) and insula, confirming a modality-specific path for TOR. Prominent activation was also present in medial and lateral secondary motor cortices, but not in primary motor areas, supporting the high level of sensory and motor integration characteristic of object recognition in the tactile modality. Activation in a lateral occipitotemporal area associated previously with visual object recognition may support cross-modal collateral activation. Finally, activation in medial temporal and prefrontal areas may reflect a common final pathway of modality-independent object recognition. This study suggests that TOR involves a complex network including parietal and insular somatosensory association cortices, as well as occipitotemporal visual areas, prefrontal, and medial temporal supramodal areas, and medial and lateral secondary motor cortices. It confirms the involvement of somatosensory association areas in the recognition component of TOR, and the existence of a ventrolateral somatosensory pathway for TOR in intact subjects. It challenges the results of previous studies that emphasize the role of visual cortex rather than somatosensory association cortices in higher-level somatosensory cognition. Hum. Brain Mapping 21:236,246, 2004. © 2004 Wiley-Liss, Inc. [source] Functional magnetic resonance imaging of human cognitive processesJAPANESE PSYCHOLOGICAL RESEARCH, Issue 1 2000Tomohisa Okada Functional magnetic resonance imaging (fMRI) is now widely accepted as a tool for analyzing human brain function. Since the realization of fMRI in the early 1990s, numerous reports have been published. In this paper, we present three studies. The first examined syntactic processing of Japanese sentences and the results prove that Broca's area is involved in the use of grammar. The second study compared binocular with monocular stereopsis. There were significant activations in the right inferior parietal lobe. The third study concerned the encoding and retrieval processes underlying face recognition. It revealed activations mainly in the right prefrontal areas, which is contrary to the hemispheric encoding and retrieval asymmetry (HERA) theory. fMRI will continue to play an important role in the analysis of human brain function. [source] Effects of Alcohol on Performance on a Distraction Task During Simulated DrivingALCOHOLISM, Issue 4 2009Allyssa J. Allen Background:, Prior studies report that accidents involving intoxicated drivers are more likely to occur during performance of secondary tasks. We studied this phenomenon, using a dual-task paradigm, involving performance of a visual oddball (VO) task while driving in an alcohol challenge paradigm. Previous functional MRI (fMRI) studies of the VO task have shown activation in the anterior cingulate, hippocampus, and prefrontal cortex. Thus, we predicted dose-dependent decreases in activation of these areas during VO performance. Methods:, Forty healthy social drinkers were administered 3 different doses of alcohol, individually tailored to their gender and weight. Participants performed a VO task while operating a virtual reality driving simulator in a 3T fMRI scanner. Results:, Analysis showed a dose-dependent linear decrease in Blood Oxygen Level Dependent activation during task performance, primarily in hippocampus, anterior cingulate, and dorsolateral prefrontal areas, with the least activation occurring during the high dose. Behavioral analysis showed a dose-dependent linear increase in reaction time, with no effects associated with either correct hits or false alarms. In all dose conditions, driving speed decreased significantly after a VO stimulus. However, at the high dose this decrease was significantly less. Passenger-side line crossings significantly increased at the high dose. Conclusions:, These results suggest that driving impairment during secondary task performance may be associated with alcohol-related effects on the above brain regions, which are involved with attentional processing/decision-making. Drivers with high blood alcohol concentrations may be less able to orient or detect novel or sudden stimuli during driving. [source] Motor imagery after stroke: Relating outcome to motor network connectivity,ANNALS OF NEUROLOGY, Issue 5 2009Nikhil Sharma PhD Objective Neuroplasticity is essential for recovery after stroke and is the target for new stroke therapies. During recovery from subcortical motor stroke, brain activations associated with movement may appear normal despite residual functional impairment. This raises an important question: how far does recovery of motor performance depend on the processes that precede movement execution involving the premotor and prefrontal cortex, rather than recovery of the corticospinal system alone? Methods We examined stroke patients with functional magnetic resonance imaging while they either imagined or executed a finger-thumb opposition sequence. In addition to classical analyses of regional activations, we studied neuroplasticity in terms of differential network connectivity using structural equation modeling. The study included 8 right-handed patients who had suffered a left-hemisphere subcortical ischemic stroke with paresis, and 13 age-matched healthy controls. Results With good functional recovery, the regional activations had returned to normal in patients. However, connectivity within the extended motor network remained abnormal. These abnormalities were seen predominantly during motor imagery and correlated with motor performance. Interpretation Our results indicate that neuroplasticity can manifest itself as differences in connectivity among cortical areas remote from the infarct, rather than in the degree of regional activation. Connection strengths between nodes of the cortical motor network correlate with motor outcome. The altered organization of connectivity of the prefrontal areas may reflect the role of the prefrontal cortex in higher order planning of movement. Our results are relevant to the assessment and understanding of emerging physical and neurophysiological therapies for stroke rehabilitation. Ann Neurol 2009;66:604,616 [source] | |||||||||||||