SEARCH · PubMed Health

Results for “Dorsolateral Prefrontal Cortex”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources

PubMed2005

Comparison perception of singular transcranial magnetic stimuli by subjectively electrosensitive subjects and general population controls.

Transcranial magnetic stimulation of the dorsolateral prefrontal cortex by single pulses of varying field intensities was used to measure thresholds of individual perception and motor response in three groups of subjects: subjectively electrosensitive people, general population controls with a high burden of complaints related to electromagnetic field (EMF) exposure in the literature (highest decile in complaint burden), and general population controls with a low burden of complaints (lowest decile in complaint burden). The major study endpoint was the ability of the subjects to differentiate between real magnetic stimulation and a sham condition. There were no significant differences between groups in the thresholds, neither of detecting the real magnetic stimulus nor in motor response. But the three groups differed significantly in differentiating between stimulation and sham condition, with the subjectively electrosensitive people having the lowest ability to differentiate and the control group with high level of EMF-related complaints having the best ability to differentiate. Differences between groups were mostly due to false alarm reactions in the sham condition reported by subjectively electrosensitives (SES). We found no objective correlate of the self perception of being "electrosensitive." Overall, our experiment does not support the hypothesis that subjectively electrosensitive patients suffer from a physiological hypersensitivity to EMFs or stimuli. Further research should focus on disposing factors explaining the unspecific sensory hyperresponsiveness of subjectively electrosensitive subjects.

Adolescent↗

PubMed1988

Distribution and some projections of cholinergic neurons in the brain of the common marmoset, Callithrix jacchus.

The distribution of choline acetyltransferase-immunoreactive (ChAT-IR) neurons was studied in the brain of the common marmoset by using immunohistochemistry. ChAT-IR neurons were found in the medial septal nucleus, vertical and horizontal limb nuclei of the diagonal band, the nucleus basalis of Meynert, pedunculopontine nucleus and laterodorsal tegmental nucleus, and also in the striatum, habenula, and brainstem cranial nerve motor nuclei. The organization of ChAT-IR neurons in the basal forebrain, midbrain, and pons is consistent with the Ch1-Ch6 nomenclature introduced by Mesulam et al. ('83). The combination of the retrograde transport of HRP-WGA with ChAT immunohistochemistry revealed the distribution of neurons in the Ch4 cell group projecting to the dorsolateral prefrontal cortex. The activity of ChAT was highest in limbic cortical structures, such as the hippocampus, and lowest in association areas of the neocortex. Lesions at various loci in the basal forebrain resulted in differential patterns of ChAT loss in the cortex, which suggests some degree of topographical organization of Ch4 projections to the cortical mantle.

Animals↗

PubMed2026

Dual Transcranial Direct Current Stimulation Modulates Hierarchical Functional Network Organization in Post-Stroke Cognitive Impairment: A Randomized Controlled Trial.

OBJECTIVE: To evaluate the clinical efficacy of dual transcranial direct current stimulation (tDCS) in patients with post-stroke cognitive impairment (PSCI) and to explore the effects on the hierarchical organization of functional brain networks, ranging from regional synchronization to inter-regional connectivity and global network topology. METHODS: In this randomized, double-blind, sham-controlled trial, 74 PSCI patients received conventional therapy alongside either active dual-tDCS (n = 38) or sham stimulation (n = 36). Active tDCS targeted the dorsolateral prefrontal cortex (DLPFC) via anodal-left/cathodal-right nodes (2.0 mA, 20 min/day, 20 sessions). The primary outcome was the Montreal Cognitive Assessment (MoCA). Secondary outcomes included the Mini-Mental Status Examination (MMSE), Stroop Test (ST), Trail Making Test (TMT), Wechsler Memory Scale (WMS), and Barthel Index (BI). A subgroup of 36 participants (18 per group) underwent resting-state functional magnetic resonance imaging (rs-fMRI) to analyze regional homogeneity (ReHo), functional connectivity (FC), and network topology. Partial correlations assessed the association between neuroimaging alterations and clinical improvements. RESULTS: The tDCS group showed significantly greater improvements in MoCA scores (tDCS: 5.74 ± 2.76 vs. sham: 2.69 ± 2.69; t = 4.799, p < 0.001) as well as in attention and memory domains compared to the sham group. The rs-fMRI changes included increased ReHo in the right middle temporal gyrus (MTG) and the left inferior frontal gyrus (IFG), and reduced FC between the right MTG-left superior frontal gyrus and left IFG-cerebellum (p < 0.05, FWE-corrected). Additionally, small-worldness and global efficiency increased (p < 0.05) with these alterations correlating with clinical recovery. Adverse events were rare and self-limiting. CONCLUSION: Dual-tDCS over bilateral DLPFC safely improves cognitive recovery in PSCI. These clinical gains are associated with rs-fMRI alterations, specifically in regional synchronization, inter-regional connectivity, and global topology, which suggest a potential biomarker for monitoring tDCS efficacy, offering a rationale for precision neuromodulation in stroke rehabilitation.

Humans↗

PubMed2004

Shorter duration of depressive episode may predict response to repetitive transcranial magnetic stimulation.

We investigated repetitive transcranial magnetic stimulation (rTMS) as a treatment for major depression. The experimental design comprised 15 medication-free subjects with major depressive disorder who were randomly assigned to receive 10 sessions of active or sham 10-Hz rTMS to the left dorsolateral prefrontal cortex at 110% motor threshold. Depression severity was measured by the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). Nonresponders to sham were allowed to receive active rTMS with the same parameters. Response to treatment was analyzed using a random regression model including episode duration and number of prior antidepressant treatments as covariates. Treatment (rTMS vs. sham) did not significantly predict changes in depression severity. Shorter duration of episode and more lifetime treatment trials significantly predicted improvements in BDI but not HDRS scores. Data from all subjects who received active rTMS (n = 14) showed that those with a depressive episode duration of shorter than 4 years had a mean HDRS decrease of 52% compared to 6% in those with an episode duration longer than 10 years. Active rTMS was well tolerated and was not associated with neuropsychological decrements when compared to sham. No significant antidepressant effects were found for 2 weeks of rTMS compared to sham. Among all subjects receiving rTMS those with a shorter duration of the current episode showed a greater response. Patients may need more than 10 treatments to obtain full benefit from rTMS. The design of future rTMS studies should consider these issues.

Adult↗

PubMed2001

Functional neuroanatomy of visuo-spatial working memory in Turner syndrome.

Turner syndrome (TS), a genetic disorder characterized by the absence of an X chromosome in females, has been associated with cognitive and visuo-spatial processing impairments. We utilized functional MRI (fMRI) to investigate the neural substrates that underlie observed deficits in executive functioning and visuo-spatial processing. Eleven females with TS and 14 typically developing females (ages 7-20) underwent fMRI scanning while performing 1-back and 2-back versions of a standard visuo-spatial working memory (WM) task. On both tasks, TS subjects performed worse than control subjects. Compared with controls, TS subjects showed increased activation in the left and right supramarginal gyrus (SMG) during the 1-back task and decreased activation in these regions during the 2-back task. In addition, decreased activation in the left and right dorsolateral prefrontal cortex (DLPFC) and caudate nucleus was observed during the 2-back task in TS subjects. Activation differences localized to the SMG, in the inferior parietal lobe, may reflect deficits in visuo-spatial encoding and WM storage mechanisms in TS. In addition, deficits in the DLPFC and caudate may be related to deficits in executive function during WM performance. Together these findings point to deficits in frontal-striatal and frontal-parietal circuits subserving multiple WM functions in TS.

Adolescent↗

PubMed2005

Prioritizing new over old: an fMRI study of the preview search task.

In visual search, observers can successfully ignore temporally separated distractors that are presented as a preview before onset of the search display. Previous behavioral studies have demonstrated the involvement of top-down selection mechanisms in preview search, biasing attention against the old set in favor of the more relevant new set. Using functional magnetic resonance imaging, we replicate and extend findings showing the involvement of superior and inferior parietal areas in the preview task when compared to both a relatively easy single-set search task and a more effortful full-set search task. In contrast, the effortful full-set search showed activation in the dorsolateral prefrontal cortex when compared to the single-set search, suggesting that this area is involved in rejecting additional distractors that could not be separated in time.

Adult↗

PubMed2005

Beyond hypofrontality: a quantitative meta-analysis of functional neuroimaging studies of working memory in schizophrenia.

Although there is considerable evidence that patients with schizophrenia fail to activate the dorsolateral prefrontal cortex (DLPFC) to the degree seen in normal comparison subjects when performing working memory or executive tasks, hypofrontality may be coupled with relatively increased activity in other brain regions. However, most imaging studies of working memory in schizophrenia have focused on DLPFC activity. The goal of this work is to review functional neuroimaging studies that contrasted patients with schizophrenia and healthy comparison subjects during a prototypical working memory task, the n-back paradigm, to highlight areas of hyper- and hypoactivation in schizophrenia. We utilize a quantitative meta-analysis method to review 12 imaging studies where patients with schizophrenia were contrasted with healthy comparison subjects while performing the n-back paradigm. Although we find clear support for hypofrontality, we also document consistently increased activation in anterior cingulate and left frontal pole regions in patients with schizophrenia compared to that in controls. These data suggest that whereas reduced DLPFC activation is reported consistently in patients with schizophrenia relative to healthy subjects, abnormal activation patterns are not restricted to this region, raising questions as to whether the pathophysiological dysfunction in schizophrenia is specific to the DLPFC and about the relationship between impaired performance and aberrant activation patterns. The complex pattern of hyper- and hypoactivation consistently found across studies implies that rather than focusing on DLPFC dysregulation, researchers should consider the entire network of regions involved in a given task when making inferences about the biological mechanisms of schizophrenia.

Brain↗

PubMed2005

Spatial interference during bimanual coordination: differential brain networks associated with control of movement amplitude and direction.

Bimanual interference emerges when spatial features, such as movement direction or amplitude, differ between limbs, as indicated by a mutual bias of limb trajectories. Although first insights into the neural basis of directional interference have been revealed recently, little is known about the neural network associated with amplitude interference. We investigated whether amplitude versus directional interference activates differential networks. Functional magnetic resonance imaging (fMRI) was applied while subjects performed cyclical, bimanual joystick movements with either the same vs. different amplitudes, directions, or both. The kinematic analysis confirmed that subjects experienced amplitude interference when they moved with different as compared to the same amplitude, and directional interference when they moved along different as compared to the same direction. On the brain level, amplitude and directional interference both resulted in activation of a bilateral superior parietal-premotor network, which is known to contribute to sensorimotor transformations during goal-directed movements. Interestingly, amplitude but not directional interference exclusively activated a bilateral network containing the dorsolateral prefrontal cortex, anterior cingulate, and supramarginal gyrus, which was shown previously to contribute to executive functions. Even though the encoding of amplitude and directional information converged and activated the same neural substrate, our data thus show that additional and partly independent mechanisms are involved in bimanual amplitude as compared to that in directional control.

Adult↗

PubMed2006

Mapping the functional anatomy of task preparation: priming task-appropriate brain networks.

The present study used functional magnetic resonance imaging (fMRI) and a cued version of a flanker paradigm to elucidate the effects of task preparation on subsequent brain activation patterns. A mixed block and event-related design was employed to examine activations associated with the cue periods themselves and the cued and un-cued correct responses to incongruent flankers. A number of areas were active during the cues, most notably left dorsolateral prefrontal cortex (DLPFC), which was interpreted as subserving a role in task-set maintenance. Widespread activity was noted for correct responses to incongruent flankers, including bilateral parietal and frontal regions, consistent with previous studies. Activation was increased in these regions for correct responses after cue periods. An overlapping network of regions was also noted for cues and correct responses, suggesting preparation of task-appropriate anatomical regions during the cue period. These results suggest that cue periods allow participants to prime task-relevant areas within the brain and highlight the importance of left DLPFC in top-down control.

Adolescent↗

PubMed2005

Quantitative proton magnetic resonance spectroscopic imaging: regional variations in the corpus callosum and cortical gray matter.

PURPOSE: To evaluate regional variations of metabolite concentrations in normal adult brain cortical gray matter regions, and the genu and splenium of the corpus callosum, using proton magnetic resonance spectroscopic imaging (MRSI). MATERIALS AND METHODS: Quantitative, multislice proton MRSI (TR/TE = 2000/280 msec) was performed in 12 normal human volunteers (age = 39 +/- 6 years, 7 male). Metabolite concentrations in selected cortical gray matter regions and the corpus callosum were estimated using the phantom replacement methodology. RESULTS: Frontal and parietal gray matter (PGM) showed strong differences in choline-containing compound (Cho) concentrations; in particular, Cho was higher in mesial frontal gray matter than in both dorsolateral prefrontal cortex (P < 0.0005) and PGM (P < 0.004). In contrast, both N-acetylaspartate (NAA) and creatine (Cr) were relatively uniformly distributed in the cortical gray matter regions evaluated. Significant metabolic differences were found between the genu and splenium of the corpus callosum. Cho concentrations were significantly higher in genu than splenium (P < 0.005), while Cr was lower (P < 0.004). NAA showed a trend to be higher in the splenium than the genu (P = 0.05). CONCLUSION: Metabolite concentrations, particularly Cho, showed strong regional variations both within cortical gray matter regions and between the genu and splenium of the corpus callosum. Mesial frontal regions showed the highest Cho signals. Differences in spectra presumably reflect underlying changes in structure and cellular composition. Normal spectral variations should always be considered when evaluating pathology within those brain regions.

Adult↗

PubMed2004

GAD67 and GAD65 mRNA and protein expression in cerebrocortical regions of elderly patients with schizophrenia.

Gamma-Aminobutyric acid (GABA), the principal inhibitory neurotransmitter of CNS, has been consistently implicated in the pathophysiology of schizophrenia. GABA is synthesized from glutamate by the enzyme glutamic acid decarboxylase (GAD). Two isoforms of GAD have been identified and have been named GAD65 and GAD67 based on their apparent molecular weights. In this study, GAD65 and GAD67 mRNA and protein levels were measured by using real-time RT-PCR and immunoblotting, respectively, in post-mortem brain tissue from the dorsolateral prefrontal cortex (DLPFC) and the occipital cortex of the elderly persons with schizophrenia and matched normal controls. In addition, the mRNA expression of GAT-1, one of the principal transporters of GABA, was also studied in the same subjects. Expression of GAD65 and GAD67 mRNA in the DLPFC and in the occipital cortex was significantly elevated in patients with schizophrenia, whereas the expression of the corresponding proteins and GAT-1 mRNA was unchanged. Although the levels of GAD65 and GAD67 messages were increased in schizophrenia subjects, the proportion of the two GAD isoforms remained constant in controls and schizophrenics. In the human DLPFC, GAD65 mRNA was found to be expressed significantly less than the message for GAD67, approximately 16% of that observed for GAD67. On the contrary, the abundance of GAD65 protein in the DLPFC was about 350% of that observed for GAD67. The results suggest a substantial dysregulation of GAD mRNA expression in schizophrenia and, taken together with the results of protein expression studies, raise the possibility that both cortical and subcortical GABA function may be compromised in the disease.

Aged↗

PubMed2005

Effect of repetitive TMS and fluoxetine on cognitive function in patients with Parkinson's disease and concurrent depression.

Previous studies show that cognitive functions are more impaired in patients with Parkinson's disease (PD) and depression than in nondepressed PD patients. We compared the cognitive effects of two types of antidepressant treatments in PD patients: fluoxetine (20 mg/day) versus repetitive transcranial magnetic stimulation (rTMS, 15 Hz, 110% above motor threshold, 10 daily sessions) of the left dorsolateral prefrontal cortex. Twenty-five patients with PD and depression were randomly assigned either to Group 1 (active rTMS and placebo medication) or to Group 2 (sham rTMS and fluoxetine). A neuropsychological battery was assessed by a rater blind to treatment arm at baseline and 2 and 8 weeks after treatment. Patients in both groups had a significant improvement of Stroop (colored words and interference card) and Hooper and Wisconsin (perseverative errors) test performances after both treatments. Furthermore, there were no adverse effects after either rTMS or fluoxetine in any neuropsychological test of the cognitive test battery. The results show that rTMS could improve some aspects of cognition in PD patients similar to that of fluoxetine. The mechanisms for this cognitive improvement are unclear, but it is in the context of mood improvement.

Aged↗

PubMed2006

Placebo-controlled study of rTMS for the treatment of Parkinson's disease.

The objective of this study is to assess the safety and efficacy of repetitive transcranial magnetic stimulation (rTMS) for gait and bradykinesia in patients with Parkinson's disease (PD). In a double-blind placebo-controlled study, we evaluated the effects of 25 Hz rTMS in 18 PD patients. Eight rTMS sessions were performed over a 4-week period. Four cortical targets (left and right motor and dorsolateral prefrontal cortex) were stimulated in each session, with 300 pulses each, 100% of motor threshold intensity. Left motor cortex (MC) excitability was assessed using motor evoked potentials (MEPs) from the abductor pollicis brevis. During the 4 weeks, times for executing walking and complex hand movements tests gradually decreased. The therapeutic rTMS effect lasted for at least 1 month after treatment ended. Right-hand bradykinesia improvement correlated with increased MEP amplitude evoked by left MC rTMS after individual sessions, but improvement overall did not correlate with MC excitability. rTMS sessions appear to have a cumulative benefit for improving gait, as well as reducing upper limb bradykinesia in PD patients. Although short-term benefit may be due to MC excitability enhancement, the mechanism of cumulative benefit must have another explanation.

Evoked Potentials, Motor↗

PubMed2006

Effects of levodopa and subthalamic nucleus stimulation on cognitive and affective functioning in Parkinson's disease.

In Parkinson's disease (PD), levodopa and subthalamic nucleus (STN) stimulation lead to major improvement in motor symptoms. Effects of both treatments on cognition and affective status are less well understood. Motor, cognitive, and affective symptoms may relate to the dysfunctioning of parallel cortico-striatal loops. The aim of this study was to assess cognition, behavior, and mood, with and without both treatments in the same group of PD patients. A group of 22 nondemented PD patients was included in this study. Patients were tested twice before surgery (off and on levodopa) and twice 3 months after surgery (OFF and ON STN stimulation, off levodopa). Cognitive and affective effects of STN stimulation and levodopa had some common, but also different, effects. STN stimulation improved performance on the planning test, associated with the dorsolateral prefrontal cortex. However, the treatments had opposite effects on tests associated with the orbitofrontal cortex; specifically, levodopa impaired while STN stimulation improved performance on the extinction phase of a reversal/extinction task. Acutely, both treatments improved motivation and decreased fatigue and anxiety. On chronic treatment (3 months after surgery), depression improved, whereas apathy worsened 3 months after surgery. To conclude, there were significant but contrasting effects of levodopa and STN stimulation on cognition and affective functions.

Affect↗

PubMed1995

Ball experiments in 32 acute akinetic catatonic patients: deficits of internal initiation and generation of movements.

We undertook ball experiments in 32 akinetic catatonic patients in order to determine specific functional deficits in the motor system in akinetic catatonia. Standardized ball experiments (catching, throwing, stopping, kicking) were conducted in 32 acute akinetic catatonic patients (23 without neuroleptics on admission), diagnosed according to Lohr, Rosebush, and the Diagnostic and Statistical Manual of Mental Disorders (3rd ed, revised) on days 0 and 21. Additionally, associated psychopathology was evaluated using different scales on days 0 and 21: the Global Assessment Scale, the Brief Psychiatric Rating Scale, the Hamilton-Anxiety Scale, the scale for the assessment of negative symptoms (SANS), and the Simpson scale for extrapyramidal side effects (SEPS). Significantly more patients were able to perform more externally guided tasks (catching, stopping) than internally guided tasks (throwing, kicking). Patients showed significantly more posturing and awkward movements on day 0 than on day 21. There was a significantly positive correlation between hypokinetic extrapyramidal features (SEPS) and negative symptoms with their cognitive alterations (SANS) on day 0. The findings suggest a deficit of internal initiation, as in parkinsonism, as well as a dysfunction in the generation of voluntary movements in akinetic catatonia. We assume an underactivity in the dorsolateral prefrontal cortex and the supplementary motor area with consecutive down-regulation of the cortical-striatal-thalamic circuit, the "motor loop," in catatonia.

Acute Disease↗

PubMed2001

Changes in neuronal activation with increasing attention demand in healthy volunteers: an fMRI study.

Several lines of evidence suggest that structures involved in mediating attention differentially respond to increasing processing demand. Investigation of differences in neuronal activation, however, has been complicated by methodological inconsistencies and concomitant discrepancies in degree of difficulty and subject effort between disparate tasks. In this study, we utilized fMRI to compare neural activation patterns associated with two related attention tasks associated with different degrees of processing load while controlling for degree of performance difficulty. Healthy volunteers performed two continuous performance tasks, utilizing an identical pairs paradigm (CPT-IP) and a matched simple number recognition paradigm with degraded stimuli (CPT-DS) during a single fMRI scan. Degree of stimulus resolution degradation in the latter CPT was designed to equalize degree of performance difficulty between the two tasks. CPT-IP and CPT-DS were both associated with activation of frontal, limbic, subcortical, and sensory integratory structures. CPT-IP administration was associated with significantly greater activation of left dorsolateral prefrontal cortex, bilateral posterior temporal cortex, bilateral putamen, and thalamus. This study demonstrates both that differing attention tasks are associated with a high degree of functional overlap and that increasing processing demand is associated with increased activation of specific portions of attentional networks.

Adult↗

PubMed2000

The behavioral complications of pallidal stimulation: a case report.

We report a case of recurrent manic episodes associated with chronic deep brain stimulation (DBS) targeting globus pallidus (GP) in the treatment of Parkinson's disease (PD). Cardinal PD symptoms and dyskinesia improved with DBS, and neuropsychological testing found improvements in visuospatial measures associated with left DBS and in verbal memory with right DBS when compared to the patient's preoperative baseline. Under conditions of right, left, and bilateral DBS, the patient experienced bouts of mania and hypomania lasting several days at a time. Positron emission tomography (PET) with (15)O-labeled water was performed after his first manic episode under four conditions: no stimulation, right DBS, left DBS, and bilateral DBS. Although no manic switch occurred during the course of the PET study, all three DBS conditions were associated with decreases in regional flow in the left parahippocampus and hippocampus and right mid-cingulate gyrus. Increases in flow in left inferior frontal area, bilateral insula, dorsolateral prefrontal cortex, and cuneus were common to all DBS conditions. GP stimulation in PD may be associated with behavioral and cognitive effects. Distributed blood flow changes observed with pallidal DBS support a role for the pallidum in cognition and affective regulation.

Adult↗

PubMed2000

In search of the language switch: An fMRI study of picture naming in Spanish-English bilinguals.

For many years, researchers investigating the brain bases of bilingualism have concentrated on two basic questions. The first concerns the nature of language representation. That is, are a bilinguals' two languages represented in distinct or overlapping areas of the brain. The second basic question in the neuropsychology of bilingualism concerns the neural correlates of language switching, that is, the areas that are active when bilinguals switch from one language to the other. Performance between single-language and dual-language picture naming was compared in a group of six Spanish-English bilinguals using behavioral measures and functional magnetic resonance imaging. Participants showed slower reaction times and increased activation in the dorsolateral prefrontal cortex in the mixed language condition relative to single language condition. There was no evidence that each language was represented in different areas of the brain. Results are consistent with the view that language switching is a part of a general executive attentional system and that languages are represented in overlapping areas of the brain in early bilinguals.

Adult↗