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Results for “Prefrontal Cortex”

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PubMed1996

The role of the dorsolateral prefrontal cortex in implicit procedural learning.

We studied the role of the dorsolateral prefrontal cortex in procedural learning. Normal subjects completed several blocks of a serial reaction time task using only one hand without or with concurrent non-invasive repetitive transcranial magnetic stimulation. To disrupt their function transiently, stimulation was applied at low intensity over the supplementary motor area or over the dorsolateral prefrontal cortex contralateral or ipsilateral to the hand used for the test. Stimulation to the contralateral dorsolateral prefrontal cortex markedly impaired procedural implicit learning, as documented by the lack of significant change in response times during the task. Stimulation over the other areas did not interfere with learning. These results support the notion of a critical role of contralateral dorsolateral prefrontal structures in learning of motor sequences.

Adult↗

PubMed1985

Extent and organization of opossum prefrontal cortex defined by anterograde and retrograde transport methods.

Prefrontal cortex is commonly defined as cortex which receives afferents from the thalamic mediodorsal nucleus (MD). The extent of opossum prefrontal cortex was mapped with anterograde and retrograde axonal transport methods. The prefrontal field was found to include not only cortex on the lateral convexity of the frontal lobe as reported in earlier studies, but, in addition, cortex within the rhinal fissure and cortex on the rostral medial wall of the hemisphere. The organization of the thalamic input to the medial wall was analyzed in some detail and compared with that of the rat. The reason for this emphasis stemmed from earlier observations which suggested that a lateral, nonolfactory segment of MD, prominent in the rat and other species, may not be present in opossum MD. In the rat, the lateral segment, which constitutes approximately one-third of MD, projects to a relatively large expanse of rostral medial cortex which is also projected upon by the anteromedial nucleus. The main projection field of the lateral one-third of opossum MD is to cortex on the lateral convexity of the frontal lobe which has no input from the anteromedial nucleus and has no counterpart in the rat. Only the most lateral edge of opossum MD projects to medial cortex, to a very small field, which is also projected upon by the anteromedial nucleus. In other respects, the organization of the rostral medial cortex is similar in rat and opossum. These results suggest that, rather than being absent, an equivalent of a nonolfactory segment may be present in opossum MD but is markedly reduced in size, compared to that in rat and other species.

Animals↗

PubMed1978

Information about movements in monkeys (Macaca mulatta) with lesions of dorsal prefrontal cortex.

It is not known on what information prefrontal cortex acts. Since it has been suggested that it might operate on information about movements, rhesus monkeys were trained on a counting task testing memory for movements. They had to tap a key until a light went out and then repeat, either immediately or after a delay, the number of presses they had made. Monkeys with lesions of dorsal prefrontal cortex were impaired on this task, unlike monkeys with lesions of sulcus principalis alone. Cortex on the dorsal prefrontal convexity appears to act on information about movements.

Animals↗

PubMed1995

Effects of lesions of prefrontal cortex, amygdala, or fornix on behavioral sensitization to amphetamine: comparison with N-methyl-D-aspartate antagonists.

Behavioral sensitization to amphetamine involves the mesoaccumbens dopamine system and is accompanied by cellular changes in this system. Excitatory amino acid antagonists, when co-administered with amphetamine, prevent both behavioral sensitization and associated changes in the mesoaccumbens dopamine system. This suggests that excitatory amino acid-dependent events are critical to the initiation of sensitization. This study sought to identify excitatory amino acid projections required for sensitization, focusing on projections to the nucleus accumbens or ventral tegmental area. The major excitatory projections to the nucleus accumbens originate in the prefrontal cortex, amygdala and hippocampus. The prefrontal cortex and amygdala also send excitatory projections to the ventral tegmental area. Ibotenic acid lesions of the prefrontal cortex or amygdala and electrolytic lesions of the fornix were performed in rats. After one week of recovery, rats were treated with water or 2.5 mg/kg amphetamine for six days and challenged with amphetamine on day 8. Activity was tested in photobeam cages on days 1 and 8. On day 1, control and sham-lesioned rats exhibited stereotyped behaviors followed by a period of post-stereotypy locomotion. On day 8, sensitization was evident as an enhancement of both stereotypy and post-stereotypy locomotion. Co-administration of N-methyl-D-aspartate antagonists [MK-801 (dizocilpine maleate) or CGS 19755] with amphetamine prevented the development of sensitization of both stereotypy and post-stereotypy locomotion. Neither antagonist, however, prevented the expression of sensitization. None of the lesions completely mimicked these effects of N-methyl-D-aspartate antagonists. Lesions of hippocampal projections traveling in the fornix produced a general disinhibition of locomotor activity, but did not prevent sensitization of either stereotypy or post-stereotypy locomotion. Lesions of the prefrontal cortex failed to prevent sensitization of stereotypy was obtained following repeated amphetamine administration. However, like prefrontal cortical lesions, amygdala lesions prevented sensitization of post-stereotypy locomotion. When interpreted in the light of previous studies demonstrating the importance of the ventral tegmental area in the initiation of sensitization, the present results suggest a likely role for neuronal circuits involving the prefrontal cortex, amygdala and ventral tegmental area in the development of sensitization of post-stereotypy locomotion following repeated amphetamine administration. Such circuits may initiate sensitization through a mechanism involving excitatory amino acid regulation of the activity of mesoaccumbens dopamine neurons. Parallel circuits, involving other brain regions, may similarly contribute to sensitization of stereotyped behaviors.

Amphetamine↗

PubMed2003

Localized functional neurochemical marker abnormalities in dorsolateral prefrontal cortex in pediatric obsessive-compulsive disorder.

BACKGROUND: Neurobiological abnormalities in the prefrontal cortex have been implicated in the pathogenesis of obsessive-compulsive disorder (OCD). Although OCD commonly arises during childhood and adolescence, to our knowledge, no prior study has examined prefrontal cortex neurochemistry in pediatric patients with OCD. METHODS: A multislice spectroscopic imaging sequence with validated phantom replacement methodology was used to measure N-acetyl-aspartate (NAA), a putative neuronal marker; choline compounds (Cho); and creatine/phosphocreatine (Cr) in right and left dorsolateral prefrontal cortex (DLPFC) of 15 treatment-naïve OCD patients, 8-15 years of age, and 15 case-matched healthy comparison subjects. RESULTS: A significant increase (21% higher) in NAA was observed in left but not right DLPFC in OCD patients versus control subjects. No significant differences in Cho or Cr were observed between groups in left or right DLPFC. CONCLUSIONS: These results provide new evidence of localized functional neurochemical marker alterations in left DLPFC in pediatric OCD. Increased left DLPFC NAA may represent neuronal hypertrophy or hyperplasia, glial hypoplasia, and/or abnormal pruning of neural brain elements in DLPFC.

Adolescent↗

PubMed2003

Manipulation of dopamine d1-like receptor activation in the rat medial prefrontal cortex alters stress- and cocaine-induced reinstatement of conditioned place preference behavior.

These studies examined the ability of the dopamine D1-like agonist SKF 81297 and D1-like antagonist SCH 23390 in the medial prefrontal cortex to alter the reinstatement of cocaine-induced conditioned place preference behavior. Male Sprague-Dawley rats were fitted with bilateral cannulae over the medial prefrontal cortex and subsequently trained in a conditioned place preference task. Animals were trained in this task using four pairings of cocaine (12 mg/kg, i.p.). Conditioned place preference was demonstrated in all animals, and this behavior was then extinguished over a 5-10-day period before testing for reinstatement. Just prior to reinstatement by immobilization stress or a cocaine priming injection (5 mg/kg, i.p.), a microinjection of the D1-like receptor antagonist SCH 23390 (0.01, 0.1 or 1.0 microg/side), or the D1-like receptor agonist SKF 81297 (0.1, 0.3 or 1.0 microg/side) was given into the medial prefrontal cortex. SCH 23390 blocked both stress- and cocaine-induced reinstatement of conditioned place preference after the two higher doses were administered into the medial prefrontal cortex. The highest dose of SKF 81297 (1.0 microg/side) prevented immobilization stress- but not cocaine-induced reinstatement. The highest dose of these drugs given in the absence of stress or cocaine did not produce reinstatement. The results indicate that immobilization stress given within the place-preference chamber is capable of producing reinstatement of cocaine-seeking behavior. The microinjection studies suggest that D1-like receptor antagonism within the prefrontal cortex is sufficient to block reinstatement by stress and cocaine. Furthermore, the results from D1-like receptor activation in the medial prefrontal cortex point to utilization of different neural pathways for stress- and cocaine-induced reinstatement.

Animals↗

PubMed1993

SCH 23390 decreases self-stimulation of the medial prefrontal cortex in the rat.

We studied the effects of peripheral and central administration of SCH 23390, a selective antagonist of dopamine D1 receptors, on intracranial self-stimulation of the medial prefrontal cortex of the rat. Intraperitoneal injections of SCH 23390 produced a dose-related decrease in self-stimulation. Unilateral microinjections of SCH 23390 into the medial prefrontal cortex also produced a dose-related decrease in self-stimulation in the ipsilateral medial prefrontal cortex. However, self-stimulation of the contralateral, noninjected prefrontal cortex, used as control, was not affected. Together with previous data, the present results suggest that the dopamine neurotransmission involved in self-stimulation of the prefrontal cortex of the rat is mediated by dopamine D1 receptors.

Animals↗

PubMed2005

Chromatin alterations associated with down-regulated metabolic gene expression in the prefrontal cortex of subjects with schizophrenia.

BACKGROUND: Schizophrenia is frequently accompanied by hypometabolism and altered gene expression in the prefrontal cortex. Cellular metabolism regulates chromatin structure, including covalent histone modifications, which are epigenetic regulators of gene expression. OBJECTIVE: To test the hypothesis that down-regulated metabolic gene expression is associated with histone modification changes in the prefrontal cortex of subjects with schizophrenia. DESIGN AND SUBJECTS: Histones and gene transcripts were profiled in the postmortem prefrontal cortex of 41 subjects with schizophrenia and 41 matched controls. The phosphorylation, acetylation, and methylation of 6 lysine, serine, and arginine residues of histones H3 and H4 were examined together with 16 metabolic gene transcripts using serial immunoblotting, immunohistochemical analysis, custom-made complementary DNA arrays, and quantitative real-time reverse transcriptase-polymerase chain reaction. RESULTS: Subjects with schizophrenia, as a group, showed no significant alterations in histone profiles or gene expression. In a subgroup of 8 patients with schizophrenia, levels of H3-(methyl)arginine 17, H3meR17, exceeded control values by 30%, and this was associated with the decreased expression of 4 metabolic transcripts. CONCLUSIONS: High levels of H3-(methyl)arginine 17 are associated with down-regulated metabolic gene expression in the prefrontal cortex of a subset of subjects with schizophrenia. Histone modifications may contribute to the pathogenesis of prefrontal dysfunction in schizophrenia.

Chromatin↗

PubMed1994

The induction of serotonin3-like receptor supersensitivity and dopamine receptor subsensitivity in the rat medial prefrontal cortex after the intraventricular administration of the neurotoxin 5,7-dihydroxytryptamine: a microiontophoretic study.

This study examines the effect of intraventricular administration of the neurotoxin 5,7-dihydroxytryptamine on serotonin1A, serotonin2 and serotonin3 receptors in the rat medial prefrontal cortex using in vivo extracellular single cell recording and iontophoresis. Iontophoresis of the serotonin1A, serotonin1C,2 and serotonin3 receptor agonists (+-)-8-hydroxy-(di-n-propyl)aminotetralin, (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane and 2-methylserotonin, respectively, produces a current-dependent (5-80 nA) suppression of the basal firing rate of medial prefrontal cortical cells in sham- and 5,7-dihydroxytryptamine-lesioned rats. The suppression produced by 2-methylserotonin and serotonin was significantly greater in 5,7-dihydroxytryptamine-lesioned rats than in control rats. No significant difference in the spontaneous activity of medial prefrontal cortex cells was observed between experimental and control rats after iontophoresis of (+-)-8-hydroxy-(di-n-propyl)aminotetralin or (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane. There was no significant difference between the groups regarding the response of medial prefrontal cortex cells to the iontophoresis of GABA, whereas the response of medial prefrontal cortex cells to the iontophoresis of dopamine was significantly attenuated in animals pretreated with 5,7-dihydroxytryptamine compared to controls. Our results indicate that 5,7-dihydroxytryptamine-induced denervation selectively enhances the sensitivity of serotonin3-like receptors in the medial prefrontal cortex, which could, at least partially, account for the serotonin denervation supersensitivity. Moreover, the finding that the response of medial prefrontal cortical cells to the iontophoresis of dopamine is attenuated in 5,7-dihydroxytryptamine pretreated rats is consistent with the view that the inhibitory action of dopamine in the medial prefrontal cortex is dependent upon serotonin tone.

5,7-Dihydroxytryptamine↗

PubMed1993

Cocaine-sensitive and -insensitive dopamine uptake in prefrontal cortex, nucleus accumbens and striatum.

Behavioral studies have indicated that the reinforcing effects of cocaine are dependent on inhibition of dopamine uptake in nucleus accumbens and prefrontal cortex. As it has been suggested that dopamine uptake and cocaine-inhibition of dopamine uptake may differ in nucleus accumbens, prefrontal cortex and striatum, we have further characterized dopamine uptake and its susceptibility to inhibition in these three regions. Dopamine uptake was resolved into two processes, which accounts for some of the apparent reported regional differences in sensitivity of dopamine to inhibition by cocaine. One, which is probably associated with uptake into dopaminergic terminals, was sensitive to 6-hydroxydopamine lesions, cocaine, GBR 12909 or ouabain and was dependent on temperature and sodium ion concentration; this was responsible for most of the observed uptake in tissue from striatum and nucleus accumbens, but not from prefrontal cortex. There appeared to be no regional difference in susceptibility of this mode of dopamine uptake to either cocaine or GBR 12909. The other type of dopamine uptake, which represented a significant proportion of the total in prefrontal cortex, but not in striatum or nucleus accumbens, was relatively insensitive to cocaine, GBR 12909 and ouabain and was dependent on temperature, but not sodium ion concentration. In addition, the cocaine-insensitive dopamine uptake was more sensitive to inhibition by dopamine than serotonin, but did not distinguish between dopamine and norepinephrine. The occurrence of cocaine-sensitive dopamine uptake in all examined regions and its equal sensitivity to cocaine and GBR 12909 is consistent with the involvement of nucleus accumbens and/or prefrontal cortex in the reinforcing effects of cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed2005

Effects of the metabotropic glutamate receptor agonist, ACPD, on the extracellular concentrations of GABA and acetylcholine in the prefrontal cortex of the rat during the normal process of aging.

The aim of the present study was to investigate the effects of activation of metabotropic glutamate receptors (mGluR) on the extracellular concentrations of GABA and acetylcholine in the prefrontal cortex of freely moving rats of different groups of age. Perfusion, through the microdialysis probe, of the agonist of mGluR, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD; 100, 500 and 1000 microM), in the prefrontal cortex of young rats produced a dose-related increase of the dialysate concentrations of GABA. The effects of perfusion of ACPD on the concentrations of GABA were attenuated in middle-aged rats. In the prefrontal cortex of aged rats, perfusion of ACPD produced no changes in dialysate concentrations of GABA at any of the doses used. Conversely, perfusion of ACPD (100, 500 and 1000 microM) in the prefrontal cortex of young, middle-aged and aged rats did not modify the dialysate concentrations of acetylcholine. Basal concentrations of acetylcholine in the prefrontal cortex of middle-aged and aged rats were significantly lower than those in young rats. In contrast, basal dialysate concentrations of GABA were not significantly different in young, middle-aged and aged rats. These results suggest that the interaction GABA-glutamate in the prefrontal cortex, mediated by mGluRs, changes with age.

Acetylcholine↗

PubMed1982

Organization of cortical afferents to the prefrontal cortex in the bush baby (Galago senegalensis).

Cortical afferents to the prefrontal cortex were studied in 10 bush babies (Galago senegalensis) by means of somatopetal transport of horseradish peroxidase. The lateral injections invariably labeled neurons in the temporal cortex and in most cases also in the insular and parietal regions. In some of these brains the cingulate and retrosplenial areas contained labeled perikarya. Injections into the medial cortex, on the other hand, consistently labeled cell bodies in the cingulate cortex, but not in the insular, temporal and parietal regions. When both lateral and medial sites of the bush baby's prefrontal cortex are considered together, apparently fewer cortical areas (as defined by Brodmann's cytoarchitectonic maps) project to the prefrontal cortex in the bush baby than in the rhesus monkey. This statement holds for both ipsi- and contralateral projections.

Afferent Pathways↗

PubMed1997

Areal segregation of face-processing neurons in prefrontal cortex.

A central issue in cognitive neuroscience concerns the functional architecture of the prefrontal cortex and the degree to which it is organized by sensory domain. To examine this issue, multiple areas of the macaque monkey prefrontal cortex were mapped for selective responses to visual stimuli that are prototypical of the brain's object vision pathway-pictorial representations of faces. Prefrontal neurons not only selectively process information related to the identity of faces but, importantly, such neurons are localized to a remarkably restricted area. These findings suggest that the prefrontal cortex is functionally compartmentalized with respect to the nature of its inputs.

Action Potentials↗

PubMed2001

Prefrontal cortex lesions augment the location-related firing properties of area TE/perirhinal cortex neurons in a working memory task.

It has previously been proposed that prefrontal cortex may have some role in keeping temporal cortex-based representations "on-line" during a working memory task. To test this hypothesis, the effects of electrolytic prefrontal cortex lesions on the firing of area TE and perirhinal cortex (PRC) neurons were examined while rats performed a delayed non-match to position task in the T-maze. The behavioural performance of control (n = 4) and lesioned (n = 4) animals were similar during this task, and many neurons displayed a statistically significant location-related variation in firing rate during the sample (44/56 neurons) and test (39/56 neurons) phases. Units from prefrontal-lesioned animals (82%) were more likely to display a significant variation in firing across the maze compared to controls (50%; P < 0.01), and to have more discrete location-related properties (50% of neurons) compared to the control (5%) group (P < 0.0005). This finding suggests that prefrontal cortex normally modulates the transmission and/or processing of spatial information in area TE/PRC during a working memory task. Modulation could be mediated through direct connections between the structures or via prefrontal control of subcortical structures. This finding has implications for our understanding of prefrontal-temporal involvement in memory and cognitive disorders.

Action Potentials↗

PubMed2004

NMDA receptor function in the prefrontal cortex of a rat model for attention-deficit hyperactivity disorder.

The spontaneously hypertensive rat (SHR) is an accepted model for attention-deficit hyperactivity disorder (ADHD) since it displays the major symptoms of ADHD (hyperactivity, impulsivity, and poor performance in tasks that require sustained attention). We have previously shown that glutamate activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors released significantly more norepinephrine from SHR prefrontal cortex slices than control Wistar-Kyoto (WKY) rats. The aim of this study was to determine whether N-methyl-D-aspartate (NMDA) receptor function is disturbed in the prefrontal cortex of SHR. Prefrontal cortex slices were incubated with 45Ca2+ in the presence or absence of 100 microM NMDA for 2 min. Activation of NMDA receptors stimulated significantly less Ca2+ uptake into prefrontal cortex slices of SHR than control WKY (2.8 +/- 0.17 vs. 3.7 +/- 0.38 nmol/mg protein, respectively, P < 0.05). Basal Ca2+ uptake into SHR slices was not significantly different from WKY. These findings are consistent with suggestions that the intracellular concentration of calcium is elevated and therefore the concentration gradient that drives calcium into the cell is decreased in SHR compared to WKY. Impaired NMDA receptor function in the prefrontal cortex of SHR could give rise to impaired cognition and an inability to sustain attention.

Animals↗

PubMed2005

Lateral prefrontal cortex: architectonic and functional organization.

A comparison of the architecture of the human prefrontal cortex with that of the macaque monkey showed a very similar architectonic organization in these two primate species. There is no doubt that the prefrontal cortical areas of the human brain have undergone considerable development, but it is equally clear that the basic architectonic organization is the same in the two species. Thus, a comparative approach to the study of the functional organization of the primate prefrontal cortex is more likely to reveal the essential aspects of the various complex control processes that are the domain of frontal function. The lateral frontal cortex appears to be functionally organized along both a rostral-caudal axis and a dorsal-ventral axis. The most caudal frontal region, the motor region on the precentral gyrus, is involved in fine motor control and direct sensorimotor mappings, whereas the caudal lateral prefrontal region is involved in higher order control processes that regulate the selection among multiple competing responses and stimuli based on conditional operations. Further rostrally, the mid-lateral prefrontal region plays an even more abstract role in cognitive control. The mid-lateral prefrontal region is itself organized along a dorsal-ventral axis of organization, with the mid-dorsolateral prefrontal cortex being involved in the monitoring of information in working memory and the mid-ventrolateral prefrontal region being involved in active judgments on information held in posterior cortical association regions that are necessary for active retrieval and encoding of information.

Anatomy, Comparative↗

PubMed1997

Reversal of LTP in the hippocampal afferent fiber system to the prefrontal cortex in vivo with low-frequency patterns of stimulation that do not produce LTD.

We examined the efficacy of several patterns of low-frequency stimulation for producing long-term depression (LTD) or depotentiation in the hippocampal fiber pathway to the prefrontal cortex in the anesthetized rat. Field potentials elicited by stimulation of the CA1/subicular region of the ventral hippocampus were recorded in the prelimbic area of the prefrontal cortex. We found no evidence that low-frequency trains (0.5-1 Hz), consisting of either single pulses, paired pulses (35-ms interpulse interval), or two-pulse bursts (5-ms interval), produce LTD in the prefrontal cortex. In contrast, all three stimulus protocols were found to induce a small-amplitude, persistent potentiation of the amplitude of the negative wave of the field response recorded in the prefrontal cortex. We also examined the ability of patterns of low-frequency stimulation to produce depotentiation of previously established long-term potentiation (LTP). Although low-frequency stimulation with single pulses or paired pulses was ineffective, we found that the two-pulse burst protocol selectively produced a rapid reversal of LTP in the hippocampo-prefrontal cortex pathway. Depotentiation is reversible and can be induced >2 h after the induction of LTP. Repeated trains failed to decrease the prefrontal cortex response below the original, unpotentiated level. These findings demonstrate the existence of a depotentiation mechanism that is capable of exerting powerful control over ongoing or recently induced synaptic plasticity in hippocampocortical connections in vivo.

Afferent Pathways↗

PubMed2000

Increased glutamate-stimulated norepinephrine release from prefrontal cortex slices of spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) have behavioral characteristics (hyperactivity, impulsiveness, poorly sustained attention) similar to the behavioral disturbances of children with attention-deficit hyperactivity disorder (ADHD). We have previously shown that dopaminergic and noradrenergic systems are disturbed in the prefrontal cortex of SHR compared to their normotensive Wistar-Kyoto (WKY) control rats. It was of interest to determine whether the underlying neural circuits that use glutamate as a neurotransmitter function normally in the prefrontal cortex of SHR. An in vitro superfusion technique was used to demonstrate that glutamate caused a concentration-dependent stimulation of [3H]norepinephrine release from rat prefrontal cortex slices. Glutamate (100 microM and 1 mM) caused significantly greater release of norepinephrine from prefrontal cortex slices of SHR than from control slices. The effect of glutamate was not mediated by NMDA receptors, since NMDA (10 and 100 microM) did not exert any effect on norepinephrine release and MK-801 (10 microM) did not antagonize the effect of 100 microM glutamate. These results demonstrate that glutamate stimulates norepinephrine release from rat prefrontal cortex slices and that this increase is enhanced in SHR. The results are consistent with the suggestion that the noradrenergic system is overactive in prefrontal cortex of SHR, the animal model for ADHD.

Animals↗