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 775 records · Page 43Linked to original sources

PubMed1991

Willed action and the prefrontal cortex in man: a study with PET.

We used positron emission tomography to contrast changes in cerebral blood flow associated with willed and routine acts. In the six tasks used, volunteers had to make a series of responses to a sequence of stimuli. For the routine acts, each response was completely specified by the stimulus. For the willed acts, the response was open-ended and therefore volunteers had to make a deliberate choice. Willed acts in the two response modalities studied (speaking a word, or lifting a finger) were associated with increased blood flow in the dorsolateral prefrontal cortex (Brodmann area 46). Willed acts were also associated with decreases in blood flow, but the location of these decreases was modality dependent.

Acoustic Stimulation↗

PubMed2004

Prefrontal activation due to Stroop interference increases during development--an event-related fNIRS study.

Although it is well known that executive processes supported by the frontal lobe develop during childhood and adolescence, only one functional imaging study has used the Stroop task to investigate the relationship between frontal lobe function and cognition from a developmental point of view. Hence, we measured brain activation in the lateral prefrontal cortex of children with functional near-infrared imaging during an event-related, color-word matching Stroop task and compared results with a previous study, conducted with the same paradigm in adults. In children, the Stroop task elicited significant brain activation in the left lateral prefrontal cortex comparable to adults. However, the hemodynamic response occurred later in children than adults. Individual brain activation due to Stroop interference varied much more in children than adults, which was paralleled by a higher behavioral variance in children. Data suggest that children differed in their individual cognitive development independent of their chronological age more than adults. Brain activation due to Stroop interference increased with age in the dorsolateral prefrontal cortex in correlation with an improvement of behavioral performance. In conclusion, our results indicate that neuromaturational processes regarding resolution of Stroop interference may depend on increased ability to recruit frontal neural resources.

Adolescent↗

PubMed2006

Organization of mnemonic and response operations within prefrontal cortex.

There is mounting evidence that prefrontal cortex (PFC) is activated during mnemonic operations such as working memory maintenance and also during response-related operations. In the current study, we examine the neural organization of mnemonic and response operations with respect to each other within PFC. Stimulus-evoked and sustained functional MRI activity was recorded during performance of a mental calculation task. The presence or absence of mnemonic and response demands was manipulated in a 2 x 2 factorial design with conditions requiring: (1) memory encoding and maintenance (M+); (2) response selection and execution (R+); (3) encoding, maintenance, and response execution (M+R+); (4) neither mnemonic nor response-related processes (M-R-). The first step of the analyses identified PFC voxels exhibiting differential activity during (M+) vs. (R+) trials. Within these voxels, we then examined activity during multiple phases of (M+R+) trials. Greater stimulus-evoked and sustained activity was observed within the anterior extent of dorsolateral prefrontal cortex (BA 46) during R+ vs. M+ trials. In contrast, greater activity was observed in the posterior extent of dorsolateral PFC during M+ vs. R+ trials. Importantly, both regions were activated during (M+R+) trials. Activity levels during all of these conditions exceeded levels observed during (M-R-) control trials. These results suggest that integrative functions of PFC that allow past information to guide future actions may emerge from communication between discrete subregions supporting mnemonic and response operations.

Adolescent↗

PubMed1996

Cortical activation in confrontation naming.

Functional magnetic resonance imaging was used to detect cortical activation in the right and left perisylvian cortex of seven young adult right-handed volunteers in response to a letter fluency task and to a visual naming task using standardized line drawings. Both letter fluency and visual naming activated left dorsolateral prefrontal cortex (Brodmann's areas 6, 9, 44 and 45). Only visual naming activated area 37 (a cortical region with strong connections to visual association areas), visual association area 19, and areas 39 and 21 previously shown to activate with auditory semantic tasks. This study supports a role for area 37 as participant in a visual lexicosemantic processing network which may otherwise overlap the auditorysemantic network.

Adult↗

PubMed1998

Functional hypofrontality and working memory dysfunction in schizophrenia.

OBJECTIVE: Hypofrontality is a common but not invariable finding in schizophrenia. Inconsistencies in the literature may reflect, in part, the fact that abnormal physiological responses in the prefrontal cortex are best identified under conditions that place well-specified functional demands on this region. METHOD: The authors studied eight patients with schizophrenia and eight matched comparison subjects using [(15)O]H2O positron emission tomography and the "N-back" task, which activates the prefrontal cortex as a function of working memory load in normal subjects. RESULTS: Under low-working-memory-load conditions, the accuracy of both groups in the N-back task was equal, but when the memory load increased, the patients' performance deteriorated more than did that of the comparison subjects. The regional cerebral blood flow response to increased working memory load was significantly reduced in the patients' right dorsolateral prefrontal cortex. CONCLUSIONS: These results confirm the importance of using tasks that tap specific cognitive functions, linked to specific neural systems, in studies of brain-behavior relationships in schizophrenia. Hypofrontality is reliably demonstrated in schizophrenia during tasks that engage working memory functions of the prefrontal cortex.

Functional Laterality↗

PubMedDate not supplied

The distribution and morphology of prefrontal cortex pyramidal neurons identified using anti-neurofilament antibodies SMI32, N200 and FNP7. Normative data and a comparison in subjects with schizophrenia, bipolar disorder or major depression.

Alterations in the density and size of pyramidal neurons in the prefrontal cortex have been described in schizophrenia and mood disorder. However, the changes are generally modest and have not always been replicated. We investigated the possibility that specific pyramidal neuron sub-populations, defined by their immunoreactivity with the anti-neurofilament antibodies SMI32, N200, and FNP7, are differentially affected in these disorders. First, we assessed the distribution and characteristics of pyramidal neurons labelled by the antibodies in the human dorsolateral prefrontal cortex (Brodmann areas 9, 32, 46), using single and double label immunocytochemistry and immunofluorescence. Three largely separate sub-populations of pyramidal neurons were identified, although with more substantial overlap between SMI32- and FNP7-positive neurons in lamina V. We then determined the density, size and shape of the three pyramidal neuron sub-populations in area 9 in patients with schizophrenia, bipolar disorder, or major depressive disorder, compared to controls (n=15 in each group). We found a lower density of lamina III N200-positive neurons in major depressive disorder than in schizophrenia or bipolar disorder. There were no other overall differences in neuronal density, or in neuronal size or shape, although a planned secondary analysis supported the previously reported decrease of neuronal size in lamina V in bipolar disorder. In summary, our study illustrates a conceptual and methodological approach which may be of value for investigating the differential neuropathological involvement of pyramidal neuron sub-populations. However, we found no clear evidence that the prefrontal neuropathology of schizophrenia or mood disorders preferentially affects SMI32-, N200- or FNP7-immunoreactive pyramidal neurons.

Adult↗

PubMed2000

Impaired planning but intact decision making in early Huntington's disease: implications for specific fronto-striatal pathology.

Previous neuropsychological data have suggested that deficits in early Huntington's disease (HD) include executive impairments, which often are linked with frontal-lobe dysfunction. This study sought to investigate the profile of cognitive deficits using two computerised tasks whose performance is known to rely on intact functions of separate areas of the prefrontal cortex. Twenty patients with early HD and 20 matched controls were given the one-touch Tower of London, a stringent measure of visuo-spatial planning, and a decision making task, which involved selecting and gambling on outcomes on the basis of their differing probabilities. Patients were significantly less accurate than controls on the planning test, which is sensitive to frontal lobe lesions and is strongly associated with the dorsolateral prefrontal cortex in functional imaging studies. On the decision making task, patients were unimpaired on the quality of their decision making, in contrast to previous reports of impairment on this task in patients with ventromedial prefrontal cortex lesions. This dissociation of performance is discussed in terms of the usual path of progression of HD through the striatum and the resultant pattern of disruption of the functioning of the different cortico-striatal functional loops.

Adult↗

PubMed2000

fMri studies of Stroop tasks reveal unique roles of anterior and posterior brain systems in attentional selection.

The brain's attentional system identifies and selects information that is task-relevant while ignoring information that is task-irrelevant. In two experiments using functional magnetic resonance imaging, we examined the effects of varying task-relevant information compared to task-irrelevant information. In the first experiment, we compared patterns of activation as attentional demands were increased for two Stroop tasks that differed in the task-relevant information, but not the task-irrelevant information: a color-word task and a spatial-word task. Distinct subdivisions of dorsolateral prefrontal cortex and the precuneus became activated for each task, indicating differential sensitivity of these regions to task-relevant information (e.g., spatial information vs. color). In the second experiment, we compared patterns of activation with increased attentional demands for two Stroop tasks that differed in task-irrelevant information, but not task-relevant information: a color-word task and color-object task. Little differentiation in activation for dorsolateral prefrontal and precuneus regions was observed, indicating a relative insensitivity of these regions to task-irrelevant information. However, we observed a differentiation in the pattern of activity for posterior regions. There were unique areas of activation in parietal regions for the color-word task and in occipitotemporal regions for the color-object task. No increase in activation was observed in regions responsible for processing the perceptual attribute of color. The results of this second experiment indicate that attentional selection in tasks such as the Stroop task, which contain multiple potential sources of relevant information (e.g., the word vs. its ink color), acts more by modulating the processing of task-irrelevant information than by modulating processing of task-relevant information.

Adult↗

PubMed1998

Dissociation of mnemonic and perceptual processes during spatial and nonspatial working memory using fMRI.

Neuroimaging studies in humans have consistently found robust activation of frontal, parietal, and temporal regions during working memory tasks. Whether these activations represent functional networks segregated by perceptual domain is still at issue. Two functional magnetic resonance imaging experiments were conducted, both of which used multiple-cycle, alternating task designs. Experiment 1 compared spatial and object working memory tasks to identify cortical regions differentially activated by these perceptual domains. Experiment 2 compared working memory and perceptual control tasks within each of the spatial and object domains to determine whether the regions identified in experiment 1 were driven primarily by the perceptual or mnemonic demands of the tasks, and to identify common brain regions activated by working memory in both perceptual domains. Domain-specific activation occurred in the inferior parietal cortex for spatial tasks, and in the inferior occipitotemporal cortex for object tasks, particularly in the left hemisphere. However, neither area was strongly influenced by task demands, being nearly equally activated by the working memory and perceptual control tasks. In contrast, activation of the dorsolateral prefrontal cortex and the intraparietal sulcus (IPS) was strongly task-related. Spatial working memory primarily activated the right middle frontal gyrus (MFG) and the IPS. Object working memory activated the MFG bilaterally, the left inferior frontal gyrus, and the IPS, particularly in the left hemisphere. Finally, activation of midline posterior regions, including the cingulate gyrus, occurred at the offset of the working memory tasks, particularly the shape task. These results support a prominent role of the prefrontal and parietal cortices in working memory, and indicate that spatial and object working memory tasks recruit differential hemispheric networks. The results also affirm the distinction between spatial and object perceptual processing in dorsal and ventral visual pathways.

Adult↗

PubMed2003

High (15 Hz) and low (1 Hz) frequency transcranial magnetic stimulation have different acute effects on regional cerebral blood flow in depressed patients.

BACKGROUND: High and low frequency repetititve transcranial magnetic stimulation (rTMS) are both effective in treating depression but have contrary effects on motor cortical activity. This study aimed to understand further the mechanisms of action of high and low frequency rTMS by examining their acute effects on regional cerebral blood flow (rCBF) in depressed patients. METHOD: Eighteen depressed subjects underwent brain single photon emission computerized tomography (SPECT) scanning using split-dose 99mTc-HMPAO, and were examined during sham and active rTMS to the left prefrontal cortex, at 15 Hz or 1 Hz (N=9 each). Relative rCBF changes were examined by statistical parametric mapping and by regions of interest analysis. RESULTS: High (15 Hz) frequency rTMS resulted in relative rCBF increases in the inferior frontal cortices, right dorsomedial frontal cortex, posterior cingulate and parahippocampus. Decreases occurred in the right orbital cortex and subcallosal gyrus, and left uncus. Low (1 Hz) frequency rTMS led to increased relative rCBF in the right anterior cingulate, bilateral parietal cortices and insula and left cerebellum. High frequency rTMS led to an overall increase, whereas low frequency rTMS produced a slight decrease, in the mean relative rCBF in the left dorsolateral prefrontal cortex. CONCLUSIONS: High (15 Hz) and low (1 Hz) frequency rTMS led to different frontal and remote relative rCBF changes, which suggests different neurophysiological and possibly neuropsychiatric consequences of a change in frequency of rTMS.

Adult↗

PubMed1998

Response channel activation and the temporoparietal junction.

When we learn to make one motor response to one visual stimulus and a different motor response to another, representations of these stimulus-response associations must be maintained to efficiently transduce perception into action. When an irrelevant distractor is presented adjacent to a target stimulus, interference is observed when the two stimuli are associated with conflicting responses, presumably due to response channel activation by the incompatible information. We have explored the neural bases of these interference effects. In a previous study, patients with hemispatial neglect showed normal interference from contralesional flankers. In another study, patients with lesions of the lateral prefrontal cortex were found not to show interference from distractors presented in the contralesional hemifield. The current study provided a more anatomically detailed investigation of the effects of posterior association cortex lesions on flanker interference. Patients with chronic, unilateral lesions involving the temporoparietal junction (TPJ), two of whom had hemispatial neglect, were compared with patients with lesions of the posterior association cortex not involving the TPJ. All patients performed a color discrimination task at fixation while a congruent or incongruent colored flanker was briefly presented (16.7 ms) in the adjacent contralesional or ipsilesional hemifield. Patients with TPJ lesions showed no interference effects from the contralesional flankers. These results suggest that the TPJ, in combination with the dorsolateral prefrontal cortex, is involved in transducing perception into action.

Aged↗

PubMed1993

Comparisons of hemi-inattention produced by unilateral lesions of the posterior parietal cortex or medial agranular prefrontal cortex in rats: neglect, extinction, and the role of stimulus distance.

Neglect in human and non-human primates has been demonstrated following unilateral lesions of both posterior parietal and prefrontal areas. While it has now been well established that a unilateral lesion of the rodent analog of dorsolateral prefrontal cortex, medial agranular cortex (AGm), results in neglect, the effects of unilateral damage restricted to rodent posterior parietal cortex (PPC) have not been examined in detail. The current study assessed rats with unilateral lesions of PPC or AGm on their ability to orient to unilateral and bilateral stimulation. Since it has been proposed in both the primate and rodent literatures that frontal areas may be responsible for the perception of near space while parietal areas may be responsible for far space, stimuli were presented at two different distances. Lesions of PPC and AGm resulted in severe neglect relative to control operates, with both PPC and AGm operates manifesting severe hemi-inattention and allesthesia relative to control operates. After behavioral recovery from neglect there was no evidence of extinction to bilateral simultaneous stimulation. While neglect to visual stimuli predominated in unilateral PPC operates, unilateral AGm operates had severe neglect in all modalities. In addition, while both left and right PPC operates showed contralesional neglect, AGm operates demonstrated the lateralized differences in neglect reported in previous studies. All groups demonstrated an approximately equivalent level of neglect to stimuli presented at the two different distances, and thus failed to support the suggestion of a peripersonal-extrapersonal dichotomy between frontal and parietal areas in rodents.

Animals↗

PubMed2005

Neural mechanisms of imitation.

Recent advances in our knowledge of the neural mechanisms of imitation suggest that there is a core circuitry of imitation comprising the superior temporal sulcus and the 'mirror neuron system', which consists of the posterior inferior frontal gyrus and adjacent ventral premotor cortex, as well as the rostral inferior parietal lobule. This core circuitry communicates with other neural systems according to the type of imitation performed. Imitative learning is supported by interaction of the core circuitry of imitation with the dorsolateral prefrontal cortex and perhaps motor preparation areas--namely, the mesial frontal, dorsal premotor and superior parietal areas. By contrast, imitation as a form of social mirroring is supported by interaction of the core circuitry of imitation with the limbic system.

Animals↗

PubMed2000

Prefrontal neurons in networks of executive memory.

The neuronal networks of the frontal lobe that represent motor or executive memories are probably the same networks that cooperate with other cerebral structures in the temporal organization of behavior. The prefrontal cortex, at the top of the perception-action cycle, plays a critical role in the mediation of contingencies of action across time, an essential aspect of temporal organization. That role of cross-temporal mediation is based on the interplay of two short-term cognitive functions: one retrospective, of short-term active perceptual memory, and the other prospective, of attentive set (or active motor memory). Both appear represented in the neuronal populations of dorsolateral prefrontal cortex. At least one of the mechanisms for the retention of active memory of either kind seems to be the reentry of excitability through recurrent cortical circuits. With those two complementary and temporally symmetrical cognitive functions of active memory for the sensory past and for the motor future, the prefrontal cortex seems to secure the temporal closure at the top of the perception-action cycle.

Animals↗

PubMed2004

Neurons expressing calcium-binding proteins in the prefrontal cortex in schizophrenia.

Increased neuronal density, cortical thinning, and alterations of GABAergic interneurons in the prefrontal cortex have been associated with the pathophysiology of schizophrenia. This study used antibodies directed against the calcium-binding proteins, calretinin (CR), parvalbumin (PV), and calbindin (CB) to compare the relative density of subpopulations of GABAergic interneurons in BA9 of the prefrontal cortex from six subjects with schizophrenia and six control subjects matched for age, gender, and postmortem interval. The relative density of interneurons expressing CR, PV, or CB did not differ significantly between subjects with schizophrenia and control subjects. In addition, no change in somal size of immunoreactive (IR) neurons or cortical thickness was observed between the two groups. This study supports previous reports consistently demonstrating no change in the relative density of interneurons expressing CR in the dorsolateral prefrontal cortex in schizophrenia but does not support previous inconsistent findings that the relative density of interneurons expressing PV and CB might be altered in this disorder.

Adult↗

PubMed2005

Abnormal object recall and anterior cingulate overactivation correlate with formal thought disorder in schizophrenia.

BACKGROUND: The neural basis of formal thought disorder (FTD) is unknown. An influential theory is that FTD results from impaired semantic memory processing. We explored the neural correlates of semantic memory retrieval in schizophrenia using an imaging task assessing semantic object recall. METHOD: Sixteen healthy control subjects and sixteen schizophrenia patients whose FTD symptoms were measured with the Thought Disorder Index completed a verbal object-recall task during functional magnetic resonance imaging. Participants viewed two words describing object features that either evoked (object recall) or did not evoke a semantic concept. RESULTS: Schizophrenia patients tended to overrecall objects for feature pairs that did not describe the same object. Functionally, rostral anterior cingulate cortex (ACC) activation in patients positively correlated with FTD severity during both correct recalled and overrecalled trials. Compared with control subjects, during object recalling, patients overactivated bilateral ACC, temporooccipital junctions, temporal poles and parahippocampi, right inferior frontal gyrus, and dorsolateral prefrontal cortex, but underactivated inferior parietal lobules. CONCLUSIONS: Our results support impaired semantic memory retrieval as underlying FTD pathophysiology. Schizophrenia patients showed abnormal activations of brain areas involved in semantic memory, verbal working memory, and initiation and suppression of conflicting responses, which were associated with semantic overrecall and FTD.

Adult↗

PubMed1999

Clozapine preferentially increases dopamine release in the rhesus monkey prefrontal cortex compared with the caudate nucleus.

Despite substantial differences between species in the organization and elaboration of the cortical dopamine innervation, little is known about the pharmacological response of cortical or striatal sites to antipsychotic medications in nonhuman primates. To examine this issue, rhesus monkeys were chronically implanted with guide cannulae directed at the principal sulcus, medial prefrontal cortex, premotor cortex, and caudate nucleus. Alterations in dopamine release in these discrete brain regions were measured in response to administration of clozapine or haloperidol. Clozapine produced significant and long-lasting increases in dopamine release in the principal sulcus, and to a lesser extent, in the caudate nucleus. Haloperidol did not produce a consistent effect on dopamine release in the principal sulcus, although it increased dopamine release in the caudate. Clozapine's preferential augmentation of dopamine release in the dorsolateral prefrontal cortex supports the idea that clozapine exerts its therapeutic effects in part by increasing cortical dopamine neurotransmission.

Animals↗

PubMed2005

Cerebral oxygenation changes in the prefrontal cortex: effects of age and gender.

Multi-channel near-infrared spectroscopy (NIRS) is an optical method, which allows non-invasive in vivo measurements of changes in the concentration of oxygenated (O(2)Hb) and deoxygenated (HHb) hemoglobin in living brain tissue, simultaneously from multiple measurement points. In the present study, 44 young and 42 elderly subjects were investigated by means of multi-channel NIRS (optical topography) during performance of the verbal fluency task (VFT). The aim of the study was to analyze the effects of the subjects' age and gender on functional brain activation during this cognitive task. In summary, the results clearly show that the VFT activated the left and right dorsolateral prefrontal cortex (increases in O(2)Hb and more localized decreases in HHb), with an obvious left-hemispheric dominance. The elderly subjects generally exhibited less activation and no left hemispheric lateralization effect. In contrast to a previous study, we did not find a clear influence of the subjects' gender on the brain activation pattern.

Adult↗