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 1,333 records · Page 74Linked to original sources

PubMed2005

Functional imaging of working memory in obstructive sleep-disordered breathing.

Functional magnetic resonance imaging was used to map cerebral activation in 16 patients with obstructive sleep-disordered breathing (OSDB) and 16 healthy subjects, during the performance of a 2-back verbal working memory task. Six patients with OSDB were reimaged after a minimum period of 8 wk of treatment with positive airway pressure. Working memory speed in OSDB was significantly slower than in healthy subjects, and a group average map showed absence of dorsolateral prefrontal activation, regardless of nocturnal hypoxia. After treatment, resolution of subjective sleepiness contrasted with no significant change in behavioral performance, persistent lack of prefrontal activation, and partial recovery of posterior parietal activation. These findings suggest that working memory may be impaired in OSDB and that this impairment is associated with disproportionate impairment of function in the dorsolateral prefrontal cortex. Nocturnal hypoxia may not be a necessary determinant of cognitive dysfunction, and sleep fragmentation may be sufficient. There may be dissociations between respiratory vs. cortical recovery and objective vs. subjective recovery. Hypofrontality may provide a plausible biological mechanism for a clinical overlap with disorders of mood and attention.

Adult↗

PubMed2004

Functional stability of dorsolateral prefrontal neurons.

Stable multiday recordings from the dorsolateral prefrontal cortex of 2 monkeys performing 2 Go/NoGo visual-discrimination tasks (one requiring well-learned responses, the other requiring learning) demonstrate that the majority of prefrontal neurons were "functionally stable". Recordings were made using a series of removable microdrives, each implanted for 3-6 mo, housing independently mobile electrodes. Action potential waveforms of 94 neurons were stable over 2-9 days; 66/94 (70%) of these cells responded each day, 22/94 (23%) never responded significantly, and 6/94 (6%) responded one day but not the next. Of 66 responsive neurons, 55 were selective for either Go or NoGo trials, individual stimuli, or eye movements. This selectivity was functionally stable (i.e., maintained) for 46/55 neurons across all recording days. Functional stability was also noted in terms of response strength (baseline firing rates compared with poststimulation firing rates) and event-related response timing. Two neurons with consistent responses in familiar testing conditions responded flexibly when the monkeys learned to make correct responses to novel stimuli. We conclude that the majority of prefrontal neurons were functionally stable during the performance of well-learned tasks. Such stability may be a general property of prefrontal neurons, given that neurons with 4 different types of task selectivity were found to be functionally stable. Conceptually similar studies based on long-term recordings in other cortical regions reached similar conclusions, suggesting that neurons throughout the brain are functionally stable.

Animals↗

PubMed2005

Neural processes associated with antisaccade task performance investigated with event-related FMRI.

One of the hallmarks of cognitive control is the suppression of prepotent but inappropriate responses. Here we used event-related functional MRI to measure functional brain activation during a stimulus-response incompatibility task. Subjects were instructed before a stimulus appeared either to look at the stimulus (prosaccade) or to look away from the stimulus (antisaccade). Eye movements were recorded so that functional brain activation could be grouped into prosaccades, correct antisaccades, and errors (saccades toward the stimulus on antisaccade trials). Correct antisaccade trials were associated with significantly more activation in frontal and parietal cortical areas compared with prosaccade trials during the late preparatory period before stimulus appearance. Correct antisaccades evoked more activation than errors in the right dorsolateral prefrontal cortex, anterior cingulate cortex (ACC), and presupplementary eye fields during this period. No significant differences were found for any comparisons early in the preparatory period. Our data suggest that the preparation of an antisaccade activates a large frontal and parietal network that may be involved in presetting the oculomotor system for the antisaccade task. These findings indicate that a large network of frontal and posterior areas is modulated during the latter component of the preparatory period on antisaccade compared with prosaccade trials. The results further suggest that the activation level of frontal cortical areas before stimulus presentation is associated with subjects' performance in the antisaccade task. In contrast, we found no areas that were more active for correct antisaccades than prosaccades or for correct antisaccades than error antisaccades during the stimulus-response period. In fact, a number of posterior cortical areas and a few areas in the superior frontal lobe were more active during the stimulus-response period on prosaccade trials than on antisaccade trials. Error antisaccades showed a larger activation in the ACC during the stimulus-response period compared with correct antisaccades.

Adult↗

PubMed2003

Preparatory set associated with pro-saccades and anti-saccades in humans investigated with event-related FMRI.

Previous studies have shown that the BOLD functional MRI (fMRI) signal is increased in several cortical areas when subjects perform anti-saccades compared with pro-saccades. It remains unknown, however, whether this increase is due to an increased cortical motor signal for anti-saccades or due to differences in preparatory set between pro- and anti-saccade trials. To address this question, we measured event-related fMRI in a paradigm that allowed us to separate instruction-related brain activity from saccade-related brain activity. In this paradigm, the instruction to either generate a pro-saccade or an anti-saccade was conveyed by a switch in the color of the central fixation stimulus and preceded the presentation of a peripheral stimulus by either 6, 10, or 14 s. Cortical areas were functionally mapped using the general linear model comparing standard pro- and anti-saccade blocks with fixation blocks. When the trials were aligned on the onset of the instruction stimulus, bilateral frontal eye fields and right hemisphere dorsolateral prefrontal cortex showed an increased signal during the instruction period on anti-saccade trials as compared with pro-saccade trials. When the trials were aligned on the movement stimulus and the instruction period activity was subtracted, there were no differences between pro- and anti-saccades. This finding suggests that the increased cortical activation found in previous blocked designs originates predominately from differences in preparatory set and not from differences in the motor signal between pro- and anti-saccades.

Adult↗

PubMed2004

Neuronal activity throughout the primate mediodorsal nucleus of the thalamus during oculomotor delayed-responses. I. Cue-, delay-, and response-period activity.

The thalamic mediodorsal nucleus (MD) has strong reciprocal connections with the dorsolateral prefrontal cortex (DLPFC), suggesting that the MD, like the DLPFC, participates in higher cognitive functions. To examine MD's participation in cognitive functions, we analyzed the characteristics of task-related activities sampled homogeneously from the MD while two monkeys performed a spatial working memory task using oculomotor responses. Of 141 task-related MD neurons, 26, 53, and 84% exhibited cue-, delay-, and response-period activity, respectively. Most of cue- and response-period activities showed phasic excitation, and most of delay-period activity showed tonic sustained activation. Among neurons with response-period activity, 74% exhibited presaccadic activity. Most cue-period, delay-period, and presaccadic activities were directional, whereas most postsaccadic activity was omni-directional. A significant contralateral bias in the best directions was present in cue-period and presaccadic activity. However, such bias was not present in delay-period activity, although most neurons had a best direction toward the contralateral visual field. We compared these characteristics with those observed in DLPFC neurons. Response-period activity was more frequently observed in the MD (84%) than in the DLPFC (56%). The directional selectivity and bias of task-related activities and the ratios of pre- and postsaccadic activities were different between MD and DLPFC. These results indicate that the MD participates in higher cognitive functions such as spatial working memory. However, the manner in which these two structures participate in these processes differs, in that the MD participates more in motor control aspects compared with the DLPFC.

Animals↗

PubMed2004

Neuronal activity throughout the primate mediodorsal nucleus of the thalamus during oculomotor delayed-responses. II. Activity encoding visual versus motor signal.

We collected single-neuron activity from the mediodorsal (MD) nucleus of the thalamus, examined the information that was represented by task-related activity during performance of a spatial working memory task, and compared the present results with those obtained in the dorsolateral prefrontal cortex (DLPFC). We used two oculomotor delayed-response (ODR) tasks. In the ordinary ODR task, monkeys were required to make a memory-guided saccade to the location where a visual cue had been presented 3 s previously, whereas in the rotatory ODR task, they were required to make a memory-guided saccade 90 degrees clockwise from the cue direction. By comparing the best directions of the same task-related activity between the two tasks, we could determine whether this activity represented the cue location or the saccade direction. All cue-period activity represented the cue location. In contrast, 56% of delay-period activity represented the cue location and 41% represented the saccade direction. Almost all response-period activity represented the saccade direction. These results indicate that task-related MD activity represents either visual or motor information, suggesting that the MD participates in sensory-to-motor information processing. However, a greater proportion of delay- and response-period activities represented the saccade direction in the MD than in the DLPFC, indicating that more MD neurons participate in prospective information processing than DLPFC neurons. These results suggest that although functional interactions between the MD and DLPFC are crucial to cognitive functions such as working memory, there is a difference in how the MD and DLPFC participate in these functions.

Animals↗

PubMed1998

Monkey prefrontal neuronal activity coding the forthcoming saccade in an oculomotor delayed matching-to-sample task.

To determine the role of the dorsolateral prefrontal cortex (PFC) in the selection of memory-guided saccadic eye movements, we recorded the activities of PFC neurons while macaque monkeys performed an oculomotor delayed matching-to-sample task. The task was designed to dissociate motor factors from visual factors in the selection and retention of the direction of the forthcoming saccade during delay periods after the visual cue but before the GO signal was presented. While the monkey fixated on a central fixation spot (FX period, 1 s), a sample cue (1 of 4 geometric figures) and a matching cue composed of two geometric figures were presented in succession (SC and MC periods, respectively, 0.5 s) with a brief delay (D1 period, 1 or 1.5 s). After another delay (D2 period, 1.5 s), the monkey made a saccade (GO period, <0.5 s) toward one of four locations (the goal) that had been indicated by the combination of the sample and matching cues in the MC period. We recorded the activities of 224 neurons in the periprincipal sulcal area of 3 hemispheres of 2 monkeys. Sixty-five neurons (29%) showed a significant increase in activity during the D2 period. Some of these also responded during other phases of the task (SC period, n = 32; D1, 22; MC, 53; GO, 47). Some of the activity during the D2(52/65, 80%) and GO (40/47, 85%) periods was associated with the direction of the forthcoming saccade ("direction selective"). Although most MC-period activities of D2 neurons were direction selective (38/53, 73%), a fraction of them (14/38) was also affected by both saccade direction and matching cue pattern. To compare quantitatively the contribution of motor (saccade direction) and visual (matching-cue pattern) factors to the activity of D2 neurons, we calculated directional and visual dependency indices (DDI and VDI) for each of the three periods (MC, D2, and GO). In both the D2 and GO periods, D2 neurons with high DDI values and low VDI values predominated. In the MC period, however, there was no significant difference between the distributions of DDI and VDI values. These findings suggest that PFC neurons store the direction of memory-guided saccades during a delay period before eye movement and that the same neurons may be involved in the decision-making process that underlies the selection of the saccade direction during the MC period.

Animals↗

PubMed1998

Matching patterns of activity in primate prefrontal area 8a and parietal area 7ip neurons during a spatial working memory task.

Single-unit recording studies of posterior parietal neurons have indicated a similarity of neuronal activation to that observed in the dorsolateral prefrontal cortex in relation to performance of delayed saccade tasks. A key issue addressed in the present study is whether the different classes of neuronal activity observed in these tasks are encountered more frequently in one or the other area or otherwise exhibit region-specific properties. The present study is the first to directly compare these patterns of neuronal activity by alternately recording from parietal area 7ip and prefrontal area 8a, under the identical behavioral conditions, within the same hemisphere of two monkeys performing an oculomotor delayed response task. The firing rate of 222 posterior parietal and 235 prefrontal neurons significantly changed during the cue, delay, and/or saccade periods of the task. Neuronal responses in the two areas could be distinguished only by subtle differences in their incidence and timing. Thus neurons responding to the cue appeared earliest and were more frequent among the task-related neurons within parietal cortex, whereas neurons exhibiting delay-period activity accounted for a larger proportion of task-related neurons in prefrontal cortex. Otherwise, the task-related neuronal activities were remarkably similar. Cue period activity in prefrontal and parietal cortex exhibited comparable spatial tuning and temporal duration characteristics, taking the form of phasic, tonic, or combined phasic/tonic excitation in both cortical populations. Neurons in both cortical areas exhibited sustained activity during the delay period with nearly identical spatial tuning. The various patterns of delay-period activity-tonic, increasing or decreasing, alone or in combination with greater activation during cue and/or saccade periods-likewise were distributed to both cortical areas. Finally, similarities in the two populations extended to the proportion and spatial tuning of presaccadic and postsaccadic neuronal activity occurring in relation to the memory-guided saccade. The present findings support and extend evidence for a faithful duplication of receptive field properties and virtually every other dimension of task-related activity observed when parietal and prefrontal cortex are recruited to a common task. This striking similarity attests to the principal that information shared by a prefrontal region and a sensory association area with which it is connected is domain specific and not subject to hierarchical elaboration, as is evident at earlier stages of visuospatial processing.

Animals↗

PubMed1999

Isodirectional tuning of adjacent interneurons and pyramidal cells during working memory: evidence for microcolumnar organization in PFC.

Studies on the cellular mechanisms of working memory demonstrated that neurons in dorsolateral prefrontal cortex (dPFC) exhibit directionally tuned activity during an oculomotor delayed response. To determine the particular contributions of pyramidal cells and interneurons to spatial tuning in dPFC, we examined both individually and in pairs the tuning properties of regular-spiking (RS) and fast-spiking (FS) units that represent putative pyramidal cells and interneurons, respectively. Our main finding is that FS units possess spatially tuned sensory, motor, and delay activity (i. e., "memory fields") similar to those found in RS units. Furthermore, when recorded simultaneously at the same site, the majority of neighboring neurons, whether FS or RS, displayed isodirectional tuning, i.e., they shared very similar tuning angles for the sensory and delay phases of the task. As the trial entered the response phase of the task, many FS units shifted their direction of tuning and became cross-directional to adjacent RS units by the end of the trial. These results establish that a large part of inhibition in prefrontal cortex is spatially oriented rather than being untuned and simply regulating the threshold response of pyramidal cell output. Moreover, the isodirectional tuning between adjacent neurons supports a functional microcolumnar organization in dPFC for spatial memory fields similar to that found in other areas of cortex for sensory receptive fields.

Action Potentials↗

PubMed2005

Bi-hemispheric engagement in the retrieval of autobiographical episodes.

Functional magnetic resonance imaging (fMRI) was used to study the neural correlates of neutral, stressful, negative and positive autobiographical memories. The brain activity produced by these different kinds of episodic memory did not differ significantly, but a common pattern of activation for different kinds of autobiographical memory was revealed that included (1) largely bilateral portions of the medial and superior temporal lobes, hippocampus and parahippocampus, (2) portions of the ventral, medial, superior and dorsolateral prefrontal cortex, (3) the anterior and posterior cingulate, including the retrosplenial, cortex, (4) the parietal cortex, and (5) portions of the cerebellum. The brain regions that were mainly activated constituted an interactive network of temporal and prefrontal areas associated with structures of the extended limbic system. The main bilateral activations with left-sided preponderance probably reflected reactivation of complex semantic and episodic self-related information representations that included previously experienced contexts. In conclusion, the earlier view of a strict left versus right prefrontal laterality in the retrieval of semantic as opposed to episodic autobiographical memory, may have to be modified by considering contextual variables such as task demands and subject variables. Consequently, autobiographical memory integration should be viewed as based on distributed bi-hemispheric neural networks supporting multi-modal, emotionally coloured components of personal episodes.

Adult↗

PubMedDate not supplied

Intracortical mechanisms of mismatch negativity dysfunction in schizophrenia.

Event-related potentials provide an objective index of neurocognitive dysfunction in schizophrenia. Schizophrenia subjects show a decreased mismatch negativity (MMN) amplitude relative to age- and sex-matched controls, along with a characteristic pattern of MMN dysfunction across conditions. Deficits in MMN generation are accompanied by (1) impaired precision of auditory sensory memory performance and (2) an interstimulus-interval-dependent deficit in auditory N(1) generation. Similar deficits are observed following systemic or local infusion of N-methyl-D-aspartate (NMDA) antagonists, supporting glutamatergic and phencyclidine/NMDA models of the disorder. Deficits in MMN generation may also be seen following focal cortical damage, especially to the dorsolateral prefrontal cortex. MMN thus provides a useful tool for investigating mechanisms underlying brain dysfunction in schizophrenia.

Attention↗

PubMed2000

Functional imaging of conditioned aversive emotional responses in antisocial personality disorder.

Individuals with antisocial personality disorder (n = 12) and healthy controls (n = 12) were examined for cerebral regional activation involved in the processing of negative affect. A differential aversive classical conditioning paradigm was applied with odors as unconditioned stimuli and faces as conditioned stimuli. Functional magnetic resonance imaging (fMRI) based on echo-planar imaging was used while cerebral activity was studied during habituation, acquisition, and extinction. Individually defined cerebral regions were analyzed. Both groups indicated behavioral conditioning following subjective ratings of emotional valence to conditioned stimuli. Differential effects were found during acquisition in the amygdala and dorsolateral prefrontal cortex. Controls showed signal decreases, patients signal increases. These preliminary results revealed unexpected signal increases in cortical/subcortical areas of patients. The increases may result from an additional effort put in by these individuals to form negative emotional associations, a pattern of processing that may correspond to their characteristic deviant emotional behavior.

Adolescent↗

PubMedDate not supplied

Functional imaging of the frontal lobes in organic dementia. Regional cerebral blood flow findings in normals, in patients with frontotemporal dementia and in patients with Alzheimer's disease, performing a word fluency test.

Patterns of functional cortical activation were studied by means of regional cerebral blood flow measurements, performed during rest and during a word fluency task in normal subjects (n = 22), in patients with Alzheimer's disease (n = 17), and in patients with frontotemporal dementia (n = 15). Although all groups showed a significant activation of the Broca's area during word production, the activation of the dorsolateral prefrontal cortex was clearly subnormal in both dementia groups. The frontal dysfunction was not explained by number of words produced, illness duration, or age. Thus, the results demonstrate that the word fluency task is a sensitive measure of frontal lobe function, and its incorporation in imaging studies may facilitate the detection of subtle functional impairment of the frontal lobes in organic dementia.

Adult↗

PubMed1987

Conditional associative learning in drug-free schizophrenic patients.

The performance on spatial and nonspatial associative learning tasks was tested in a sample of male drug-free DSM III-diagnosed schizophrenic patients and in a closely matched normal control group. Schizophrenics showed a worse performance on both versions of the task, but especially on the nonspatial one. A significant correlation was observed between some indices of the nonspatial task and the scores on two subscales (affective flattening and anhedonia) of the scale for the assessment of negative symptoms by Andreasen. These results are consistent with the hypothesis of a dysfunction of dorsolateral prefrontal cortex in schizophrenia and with the postulated linkage between such dysfunction and negative schizophrenic symptomatology.

Adult↗

PubMed2000

The emotional modulation of cognitive processing: an fMRI study.

The functional neuroanatomy of visual processing of surface features of emotionally valenced pictorial stimuli was examined in normal human subjects using functional magnetic resonance imaging (fMRI). Pictorial stimuli were of two types: emotionally negative and neutral pictures. Task performance was slower for the negatively valenced than for the neutral pictures. Significant blood oxygen level dependent (BOLD) increases occurred in the medial and dorsolateral prefrontal cortex, midbrain, substantia innominata, and/or amygdala, and in the posterior cortical visual areas for both stimulus types. Increases were greater for the negatively valenced stimuli. While there was a small but significant BOLD decrease in the subgenual prefrontal cortex, which was larger in response to the negatively valenced pictures, there was an almost complete absence of other decreases prominently seen during the performance of demanding cognitive tasks [Shulman, G. L., Fiez, J. A., Corbetta, M., Buckner, R. L., Miezin, F. M., Raichle, M. E., & Petersen, S. E. (1997). Common blood flow changes across visual tasks: II. Decreases in cerebral cortex. Journal of Cognitive Neuroscience, 9, 648--663]. These results provide evidence that the emotional valence and arousing nature of stimuli used during the performance of an attention-demanding cognitive task are reflected in discernable, quantitative changes in the functional anatomy associated with task performance.

Adult↗

PubMed2001

Identifying rate-limiting nodes in large-scale cortical networks for visuospatial processing: an illustration using fMRI.

With the advent of functional neuroimaging techniques, in particular functional magnetic resonance imaging (fMRI), we have gained greater insight into the neural correlates of visuospatial function. However, it may not always be easy to identify the cerebral regions most specifically associated with performance on a given task. One approach is to examine the quantitative relationships between regional activation and behavioral performance measures. In the present study, we investigated the functional neuroanatomy of two different visuospatial processing tasks, judgement of line orientation and mental rotation. Twenty-four normal participants were scanned with fMRI using blocked periodic designs for experimental task presentation. Accuracy and reaction time (RT) to each trial of both activation and baseline conditions in each experiment was recorded. Both experiments activated dorsal and ventral visual cortical areas as well as dorsolateral prefrontal cortex. More regionally specific associations with task performance were identified by estimating the association between (sinusoidal) power of functional response and mean RT to the activation condition; a permutation test based on spatial statistics was used for inference. There was significant behavioral-physiological association in right ventral extrastriate cortex for the line orientation task and in bilateral (predominantly right) superior parietal lobule for the mental rotation task. Comparable associations were not found between power of response and RT to the baseline conditions of the tasks. These data suggest that one region in a neurocognitive network may be most strongly associated with behavioral performance and this may be regarded as the computationally least efficient or rate-limiting node of the network.

Adolescent↗

PubMed2001

Functional anatomical correlates of controlled and automatic processing.

Behavioral studies have shown that consistent practice of a cognitive task can increase the speed of performance and reduce variability of responses and error rate, reflecting a shift from controlled to automatic processing. This study examines how the shift from controlled to automatic processing changes brain activity. A verbal Sternberg task was used with continuously changing targets (novel task, NT) and with constant, practiced targets (practiced task, PT). NT and PT were presented in a blocked design and contrasted to a choice reaction time (RT) control task (CT) to isolate working memory (WM)-related activity. The three-dimensional (3-D) PRESTO functional magnetic resonance imaging (fMRI) sequence was used to measure hemodynamic responses. Behavioral data revealed that task processing became automated after practice, as responses were faster, less variable, and more accurate. This was accompanied specifically by a decrease in activation in regions related to WM (bilateral but predominantly left dorsolateral prefrontal cortex (DLPFC), right superior frontal cortex (SFC), and right frontopolar area) and the supplementary motor area. Results showed no evidence for a shift of foci of activity within or across regions of the brain. The findings have theoretical implications for understanding the functional anatomical substrates of automatic and controlled processing, indicating that these types of information processing have the same functional anatomical substrate, but differ in efficiency. In addition, there are practical implications for interpreting activity as a measure for task performance, such as in patient studies. Whereas reduced activity can reflect poor performance if a task is not sensitive to practice effects, it can reflect good performance if a task is sensitive to practice effects.

Adult↗

PubMed2001

Ipsilesional biases in saccades but not perception after lesions of the human inferior parietal lobule.

We examined the effects of chronic unilateral lesions to either the inferior parietal lobe, or to the dorsolateral prefrontal cortex including the frontal eye fields (FEFs), upon human visual perception and saccades in temporal-order-judgment (TOJ) tasks. Two visual events were presented on each trial, one in each hemifield at various stimulus onset asynchronies (SOAs). In the saccade task, patients moved their eyes to whichever stimulus attracted gaze first. In the perceptual-manual task, they pressed a button to indicate which stimulus was perceived first. Frontal patients showed appropriate TOJs for visual targets in both tasks. Parietal patients showed appropriate TOJs in the perceptual-manual but not the saccade task; their saccades tended to be ipsilesional unless the contralesional target led substantially. This reveals a bias in saccade choice after parietal damage that cannot be attributed to deficient visual perception. These results challenge previous claims that only anterior lesions produce motoric spatial biases in humans. However, they are in accord with recent neurophysiological evidence for parietal involvement in saccade generation, and also with suggestions that visuomotor transformations in the parietal lobe serving direct spatial motor responses can dissociate from conscious perception as indicated by indirect arbitrary responses.

Adult↗