Anterior Medial Cortex Research Articles

Structural and functional map for forelimb movement phases between cortex and medulla

The cortex influences movement by widespread top-down projections to many nervous system regions. Skilled forelimb movements require brainstem circuitry in the medulla; however, the logic of cortical interactions with these neurons remains unexplored. Here, we reveal a fine-grained anatomical and functional map between anterior cortex (AC) and medulla in mice. Distinct cortical regions generate three-dimensional synaptic columns tiling the lateral medulla, topographically matching the dorso-ventral positions of postsynaptic neurons tuned to distinct forelimb action phases. Although medial AC (MAC) terminates ventrally and connects to forelimb-reaching-tuned neurons and its silencing impairs reaching, lateral AC (LAC) influences dorsally positioned neurons tuned to food handling, and its silencing impairs handling. Cortico-medullary neurons also extend collaterals to other subcortical structures through a segregated channel interaction logic. Our findings reveal a precise alignment between cortical location, its function, and specific forelimb-action-tuned medulla neurons, thereby clarifying interaction principles between these two key structures and beyond.

Structural neuroimaging in patients with anorexia nervosa

The paper analyzes domestic and foreign literature on aspects of diagnosis, pathogenesis, neuroimaging data in patients with anorexia nervosa. The results of the examination of the brain of patients with anorexia nervosa using magnetic resonance imaging 43 patients with anorexia nervosa aged 14 to 19 years were examined. The control group consisted of 31 healthy volunteers. Post-processing was carried out using MR voxel-based morphometry. The total volumes of the brain, as well as the volumes of various structures were analyzed in patients with anorexia nervosa in comparison with healthy volunteers. In general, patients with AN showed an increase in the total amount of CSF, a decrease in the volume of gray matter, mainly due to the cortex of the left hemisphere, and white matter, and there was no statistically significant ventriculodilatation, i. e. there is an expansion of external liquor spaces. As a result of the study, MR-morphometric analysis revealed significant differences in the thickness of the left hemisphere cortex, in absence of differences in the thickness of the right hemisphere cortex. At the same time, in patients with anorexia was detected a decrease in the thickness of precuneus cortex, superior frontal and anterior medial cortex, precentral, inferior temporal, inferior parietal and lateral occipital cortex. And the insula cortex in patients with anorexia was significantly thicker than in the control group.

Resting-state functional connectivity of the default mode network associated with happiness.

Happiness refers to people's cognitive and affective evaluation of their life. Why are some people happier than others? One reason might be that unhappy people are prone to ruminate more than happy people. The default mode network (DMN) is normally active during rest and is implicated in rumination. We hypothesized that unhappiness may be associated with increased default-mode functional connectivity during rest, including the medial prefrontal cortex (MPFC), posterior cingulate cortex (PCC) and inferior parietal lobule (IPL). The hyperconnectivity of these areas may be associated with higher levels of rumination. One hundred forty-eight healthy participants underwent a resting-state fMRI scan. A group-independent component analysis identified the DMNs. Results indicated increased functional connectivity in the DMN was associated with lower levels of happiness. Specifically, relative to happy people, unhappy people exhibited greater functional connectivity in the anterior medial cortex (bilateral MPFC), posterior medial cortex regions (bilateral PCC) and posterior parietal cortex (left IPL). Moreover, the increased functional connectivity of the MPFC, PCC and IPL, correlated positively with the inclination to ruminate. These results highlight the important role of the DMN in the neural correlates of happiness, and suggest that rumination may play an important role in people's perceived happiness.

Evidence of a Dissociation Pattern in Resting-State Default Mode Network Connectivity in First-Episode, Treatment-Naive Major Depression Patients

Imaging studies have shown that major depressive disorder (MDD) is associated with altered activity patterns of the default mode network (DMN). However, the neural correlates of the resting-state DMN and MDD-related pathopsychological characteristics, such as depressive rumination and overgeneral autobiographical memory (OGM) phenomena, still remain unclear. Using independent component analysis, we analyzed resting-state functional magnetic resonance imaging data obtained from 35 first-episode, treatment-naive young adults with MDD and from 35 matched healthy control subjects. Patients with MDD exhibited higher levels of rumination and OGM than did the control subjects. We observed increased functional connectivity in the anterior medial cortex regions (especially the medial prefrontal cortex and anterior cingulate cortex) and decreased functional connectivity in the posterior medial cortex regions (especially the posterior cingulate cortex/precuneus) in MDD patients compared with control subjects. In the depressed group, the increased functional connectivity in the anterior medial cortex correlated positively with rumination score, while the decreased functional connectivity in the posterior medial cortex correlated negatively with OGM score. We report dissociation between anterior and posterior functional connectivity in resting-state DMNs of first-episode, treatment-naive young adults with MDD. Increased functional connectivity in anterior medial regions of the resting-state DMN was associated with rumination, whereas decreased functional connectivity in posterior medial regions was associated with OGM. These results provide new evidence for the importance of the DMN in the pathophysiology of MDD and suggest that abnormal DMN activity may be an MDD trait.

Processus Supracondylaris Humeri

A 24-year-old man presented with a 6-month history of paresthesia and numbness of the right hand. On clinical examination, paresthesia in the region of the right median nerve was elicited on elbow extension. Radiography of the right elbow revealed a supracondylar process of the humerus (processus supracondylaris humeri) (arrow). A supracondylar process of the humerus is an outgrowth of bone originating from the anterior–medial cortex of the distal humerus. It occurs in approximately 0.4 to 2.0% of whites and less frequently in blacks. It can measure up to 20 mm in length and is a congenital human anatomical variation that . . .

Medial cortex activity, self-reflection and depression

Using functional magnetic resonance imaging, we investigated neural activity associated with self-reflection in depressed [current major depressive episode (MDE)] and healthy control participants, focusing on medial cortex areas previously shown to be associated with self-reflection. Both the MDE and healthy control groups showed greater activity in anterior medial cortex (medial frontal gyrus, anterior cingulate gyrus) when cued to think about hopes and aspirations compared with duties and obligations, and greater activity in posterior medial cortex (precuneus, posterior cingulate) when cued to think about duties and obligations (Experiment 1). However, the MDE group showed less activity than controls in the same area of medial frontal cortex when self-referential cues were more ambiguous with respect to valence (Experiment 2), and less deactivation in a non-self-referential condition in both experiments. Furthermore, individual differences in rumination were positively correlated with activity in both anterior and posterior medial cortex during non-self-referential conditions. These results provide converging evidence for a dissociation of anterior and posterior medial cortex depending on the focus of self-relevant thought. They also provide neural evidence consistent with behavioral findings that depression is associated with disruption of positively valenced thoughts in response to ambiguous cues, and difficulty disengaging from self-reflection when it is appropriate to do so.

Assessment of cognitive function following magnesium therapy in the traumatically injured brain.

Many studies have examined the preclinical efficacy of Mg2+ therapy in models of traumatic brain injury. However, more of these studies have examined sensorimotor and motor performance than cognitive performance following injury. The present paper reviews the use of Mg2+ therapy to facilitate cognitive recovery in several models of cortical injury in the rodent. The first study examined the ability of daily injections of MgCl2 (1 or 2 mmol) to impair acquisition of a reference memory task in the Morris Water Maze. Additional studies examined the ability of MgCl2 to improve cognitive function following bilateral anterior medial cortex ablations, bilateral frontal cortex contusions, and unilateral frontal contusions. The results from these studies indicate that MgCl2 therapy is biologically active and readily crosses the blood-brain barrier because daily injections of MgCl2 impaired learning of a reference memory task in intact rats. Mg2+ therapy for brain injury revealed that administration of post-injury MgCl2 effectively improved recovery of cognitive deficits following injury. These results suggest that Mg2+ therapy is effective in facilitating cognitive recovery of function following brain injury; however, there are task and dose-dependent aspects to this recovery.

The behavioral effects of magnesium therapy on recovery of function following bilateral anterior medial cortex lesions in the rat

Magnesium (Mg ++) therapy has been shown to be neuroprotective and to facilitate recovery of motor and sensorimotor function in a variety of animal models of traumatic brain injury. However, few studies have investigated the efficacy of Mg ++ therapy on cognitive impairments following injury. The present study evaluated the ability of magnesium chloride (MgCl 2) to facilitate recovery of function following bilateral anterior medial cortex lesions (bAMC). Rats received electrolytic bAMC lesions or sham surgery and were then treated with 1 mmol/kg, i.p. MgCl 2, 2 mmol/kg, i.p. MgCl 2, or 1.0 ml/kg, i.p. 0.9% saline. Drug treatment was administered 15 min following injury with subsequent injections administered at 24 and 72 h. Rats were tested on a battery of behavioral tests that measured both cognitive (reference and working memory in the Morris Water Maze (MWM) and spatial delayed matching-to-sample (DMTS)) and sensorimotor performance (bilateral tactile adhesive removal). The results indicated that bAMC lesions produced significant cognitive impairments in reference memory and working memory in the MWM, DMTS and sensorimotor impairments compared to shams. Mg ++ therapy exhibited a dose-dependent effect in facilitating recovery of function. Administration of 2 mmol of MgCl 2 significantly improved performance on the bilateral adhesive tactile removal test, DMTS and working memory tests. The 1 mmol dose of MgCl 2 reduced the initial deficit on the tactile adhesive removal test and reduced the working memory impairment on the second day of testing. These results suggest Mg ++ therapy improves cognitive performance following injury in a dose-dependent manner.

An in-vivo model for the rapid assessment of skeletal effects of anabolic agents.

We recently developed an in vivo model which can be used to rapidly assess the local skeletal effects of anabolic agents. In this model, 160 g Sprague-Dawley (SD) rats were used. A stainless steel cannula was inserted into the marrow cavity of the proximal tibia through the anterior-medial cortex 6 mm distal to the knee joint. The outer opening of the cannula was covered by skin. Agents with known anabolic skeletal effects or vehicle were injected daily for 10 days into the marrow region by a small needle passing through the cannula. Rats were also injected subcutaneously with a fluorescent bone marker to label the newly formed bone. Injection sites were fixed, embedded, and sectioned for histomorphometric analysis of trabecular bone. PTH and PGE2 stimulated a large amount of new trabecular bone formation in regions proximal and distal to the injection site as measured by histomorphometry. Control groups showed minimal bone formation, limited to formation of a thin layer of bony shell immediately surrounding the cannula. The profound anabolic skeletal effects of PTH and PGE2 seen in this Local Injection Model are similar to those seen in systemic injection (i.e. subcutaneous injection in intact or castrated male and female rats) previously reported. This Local Injection Model combines numerous advantages of in vivo models (systemic injection) and in vitro models when assessing agents with anabolic skeletal activities. Compared to conventional in vivo systemic injection models, this model enables detection of anabolic skeletal effects using very small quantities (in microgram) of test agents in a short treatment period (< 10 days).(ABSTRACT TRUNCATED AT 250 WORDS)

3H-2-deoxyglucose uptake after electrical stimulation of cardioactive sites in anterior medial cortex in rabbits

The anterior medial cortex is an important integrative area for cardiovascular adjustments occurring during learning and conditioning. The autoradiographic 3H-2-deoxyglucose ( 3H-2DG) method for regional cerebral metabolic activity was used to identify other forebrain regions associated with cardiovascular adjustments elicited by electrical stimulation of anterior medial cortex. Rabbits that received anterior midline stimulation that produced bradycardia and depressor responses showed increased metabolic activity in the ipsilateral mediodorsal (MD) nucleus of the thalamus and the dorsal aspect of the claustrum. Two additional animals with anterior cortical placements in the infralimbic and anterior limbic areas showed ipsilateral increased activity in perirhinal cortex, but more dorsolateral placements in the precentral agranular area did not produce increased perirhinal activity. Control animals did not show this pattern of activity. These data suggest that MD and claustrum participate in a neural circuit which mediates cardiovascular adjustments similar to those elicited by Pavlovian conditioning contingencies.

Biochemical evidence for glutamate as neurotransmitter in corticostriatal and corticothalamic fibres in rat brain

The effects of ablation of frontal, occipital or entire hemicortex on several neurotransmitter parameters in the rostral and caudal neostriatum, thalamus and the contralateral anterior medial cortex were investigated. In particular the effects on the high affinity uptake of d-aspartate and on the endogenous level of amino acids, especially glutamate and aspartate, were studied in order to identify glutamate- or aspartate-containing nerve terminals in these regions. The results show a specific decrease in high affinity uptake of d-aspartate in both rostral and caudal neostriatum ipsilateral to the lesion after frontal or entire hemidecortication. There was also a small but significant decrease in d-aspartate uptake on the contralateral side. Only the level of endogenous glutamate decreased in the neostriatum after hemidecortication. There was a specific decrease in d-aspartate uptake in the thalamus only ipsilateral to the cortical lesions. In thalamus there was a significant decrease both in the level of glutamate and to a smaller extent in that of aspartate after hemidecortication. Anterior medial cortex showed a very active high affinity uptake of d-aspartate, which was slightly reduced after removal of the contralateral hemicortex. The high affinity uptake of d-aspartate was in all cases mainly due to uptake in synaptosomes. The results show that the neostriatum receives glutamate-containing fibres from the neocortex, particularly the frontal part. This projection is mainly ipsilateral with a small element derived from the contralateral side. The thalamus, both the rostral and caudal parts, receives glutamate-containing fibres from the whole extent of the ipsilateral neocortex. Some of the corticothalamic fibres may also contain aspartate. The anterior medial cortex probably contains a high proportion of glutamate- and/or aspartate-containing nerve terminals but only a low proportion of these are derived from the contralateral cortex.

Convergent thalamic and mesencephalic projections to the anterior medial cortex in the rat.

Small microelectrophoretic deposits of horseradish-peroxidase (HRP) were placed at various loci within the gray matter of the rat's anterior medial cortex. A comparison of the patterns of retrograde cell-labeling charted in 26 such cases confirmed earlier findings in fiber-degeneration studies according to which the respective thalamocortical projections of the mediodorsal (MD) and anteromedial nucleus (AM) overlap each other over a wide region of the anterior medial cortex. This region of thalamocortical convergence, extending from pregenual levels caudalward as far as the anterior border of the retrosplenial cortex, corresponds almost exactly to the cortical region from which locally deposited HRP was found to be transported so as to label cells in one or both of two mesencephalic cell groups: the ventral tegmental area (AVT) dorsal and lateral to the interpeduncular nucleus, and the medial one-quarter of the pars compacta of the substantia nigra (SNC).