Cortical and ventral tegmental systems exert opposing influences on self-stimulation from the prefrontal cortex

Intracranial self-stimulation (ICSS) was obtained from 3 areas of anteromedial cortex: the prelimbic area (Brodman's area 32), the anterior cingulate area and the posterior cingulate area. Electrical stimulation in the prelimbic and anterior cingulate areas also produces a behavioral inhibition which is most pronounced at anterior sites (i.e. prelimbic) and declines at increasingly more posterior sites. It was found that the acquisition of responding for ICSS and the magnitude of amphetamine's facilitation of ICSS were inversely related to the degree of behavioral inhibition. These data and the ability of amphetamine to reverse prefrontal stimulation-induced inhibition suggest an important interaction between the prefrontal cortex and the mesolimbic dopamine systems in the control of goal-directed behavior. A model involving cortical suppression of mesolimbic dopamine function is discussed.     

Topography of projections from the medial prefrontal cortex to the amygdala in the rat

The projections from the rat medial prefrontal cortex to the amygdaloid complex were investigated using retrograde transport of fluorescent dyes and anterograde transport of horseradish peroxidase-WGA. The ventral anterior cingulate, prelimbic, infralimbic and medial orbital areas and the taenia tecta were found to project to the amygdaloid complex. The projections from the prelimbic area arose bilaterally. The medial orbital, prelimbic and anterior cingulate areas send convergent projections to the basolateral nucleus. The prelimbic area has additional projections to the posterolateral cortical nucleus and amygdalo-hippocampal area. The infralimbic area does not project to the basolateral nucleus and cortico-amygdaloid projections from this area are focussed on the anterior cortical nucleus and the anterior amygdaloid area. Both prelimbic and infralimbic areas project to an area situated between the central, medial and basomedial nuclei. Based on similar projections, this area appears to be a caudal continuation of the anterior amygdaloid area. The results indicate that the medial prefrontal component of the "basolateral limbic circuit" is restricted to the anterior cingulate and prelimbic areas. No evidence was obtained to support the existence of a medial prefronto-amygdaloid component of the "visceral forebrain".     

C-fos Expression During Vocal Mobbing in the New World Monkey Saguinus fuscicollis

In order to find brain areas involved in the vocal expression of emotion, we compared c-fos expression in three groups of saddle-back tamarins (Saguinus fuscicollis). One group, consisting of three animals, was made to utter more than 800 mobbing calls by electrical stimulation of the periaqueductal grey of the midbrain (PAG). A second group, consisting of two animals, was stimulated in the PAG with the same intensity and for the same duration as the first group but at sites that did not produce vocalization. These sites lay somewhat medial to the vocalization-eliciting sites. A third group, consisting of two animals, was stimulated at vocalization-eliciting sites in the PAG but with an intensity below vocalization threshold. Fos-like immunoreactivity that was found in the vocalizing but not in the non-vocalizing animals was located in the dorsomedial and ventrolateral prefrontal cortex, anterior cingulate cortex, ventrolateral premotor cortex, sensorimotor face cortex, insula, inferior parietal cortex, superior temporal cortex, claustrum, entorhinal and parahippocampal cortex, basal amygdaloid nucleus, anterior and dorsomedial hypothalamus, nucleus reuniens, lateral habenula, Edinger-Westphal nucleus, ventral and dorsolateral midbrain tegmentum, nucleus cuneiformis, sagulum, pedunculopontine and laterodorsal tegmental nuclei, ventral raphe, periambigual reticular formation and solitary tract nucleus. For some of these structures (e.g. anterior cingulate cortex and periambigual reticular formation), there is evidence also from electrical stimulation, lesioning and single-unit recording studies that they are involved in vocal control. For other structures (e.g. lateral habenula, Edinger-Westphal nucleus), the available evidence speaks against such a role. Fos activation in these cases is probably related to non-vocal reactions accompanying the electrically elicited vocalizations. A third group of structures consists of areas for which a role in vocal control cannot be excluded but for which the present study presents the first evidence for such a role (e.g. claustrum and sagulum). These structures deserve further studies using more specific methods.     

Associational projections of the anterior midline cortex in the rat: intracingulate and retrosplenial connections

Past studies indicate that distinct areas of anterior midline cortex in the rat contribute to diverse functions, such as autonomic nervous system regulation and learning, but the anatomical substrate for these functions has not been fully elucidated. The present study characterizes the associational connections within the midline cortex of the rat by using the anterograde transport of Phaseolus vulgaris leucoagglutinin and Fluororuby. The prelimbic area and the rostral part of the anterior cingulate area (both dorsal and ventral subdivisions) are extensively interconnected with each other. In addition, the caudal half of anterior cingulate cortex has extensive projections to precentral medial cortex and caudally directed projections to retrosplenial cortex. Other cortical areas within anterior midline cortex have relatively limited cortical–cortical projections. The infralimbic, dorsal peduncular, and medial precentral cortices have dense intrinsic projections, but have either very limited or no projections to other areas in the anterior midline cortex. Although it has been suggested that cortical–cortical projections from anterior cingulate cortex and prelimbic cortex to infralimbic cortex may be important for linking learning processes with an autonomic nervous system response, the paucity of direct projections between these areas calls this hypothesis into question. Conversely, the results suggest that the anterior midline cortex contains two regions that are functionally and connectionally distinct.     

Orbitomedial prefrontal cortical projections to distinct longitudinal columns of the periaqueductal gray in the rat

We utilised retrograde and anterograde tracing procedures to study the origin and termination of prefrontal cortical (PFC) projections to the periaqueductal gray (PAG) in the rat. A previous study, in the primate, had demonstrated that distinct subgroups of PFC areas project to specific PAG columns. Retrograde tracing experiments revealed that projections to dorsolateral (dlPAG) and ventrolateral (vlPAG) periaqueductal gray columns arose from medial PFC, specifically prelimbic, infralimbic, and anterior cingulate cortices. Injections made in the vlPAG also labeled cells in medial, ventral, and dorsolateral orbital cortex and dorsal and posterior agranular insular cortex. Other orbital and insular regions, including lateral and ventrolateral orbital, ventral agranular insular, and dysgranular and granular insular cortex did not give rise to appreciable projections to the PAG. Anterograde tracing experiments revealed that the projections to different PAG columns arose from specific PFC areas. Projections from the caudodorsal medial PFC (caudal prelimbic and anterior cingulate cortices) terminated predominantly in dlPAG, whereas projections from the rostroventral medial PFC (rostral prelimbic cortex) innervated predominantly the vlPAG. As well, consistent with the retrograde data, projections arising from select orbital and agranular insular cortical areas terminated selectively in the vlPAG. The results indicate: (1) that rat orbital and medial PFC possesses an organisation broadly similar to that of the primate; and (2) that subdivisions within the rat orbital and medial PFC can be recognised on the basis of projections to distinct PAG columns.     

Effects of catecholamine uptake blockers in the caudate-putamen and subregions of the medial prefrontal cortex of the rat

Altered dopamine regulation in the medial prefrontal cortex has been linked to drug abuse and disorders such as schizophrenia. Heterogeneous expression of the dopamine transporter, as well as the ability of the norepinephrine transporter to clear dopamine in the prefrontal cortex, delineates two potential sites for the regulation of synaptic dopamine within the cortex. The present study used in vivo microdialysis to compare the effects of local infusions of dopamine and norepinephrine uptake blockers in the caudate putamen and two subregions of the prefrontal cortex, the anterior cingulate and prelimbic/infralimbic cortices. Results revealed that all dopamine uptake blockers produced greater increases in dopamine efflux in the caudate-putamen relative to the prefrontal cortex. In addition, amphetamine administration increased dopamine efflux to a greater degree in the prelimbic, relative to the anterior cingulate, cortex. In contrast, the increase in dopamine efflux was similar in both subregions in the presence of nomifensine and desmethylimipramine. Infusions of the selective dopamine uptake blocker GBR 12909 failed to alter dopamine efflux in any prefrontocortical subregion. These data indicate a more prominent role for the dopamine transporter in the clearance of extracellular dopamine in the caudate-putamen relative to the prefrontal cortex and an important role for NET in the clearance of dopamine in both the prelimbic and anterior cingulate subregions of the rat medial prefrontal cortex.     

Cortical lesion effects and vocalization in the squirrel monkey

The effects of bilateral destruction of the cortical face area, anterior and posterior supplementary motor area and anterior cingular cortex on spontaneous vocalization were studied in 16 squirrel monkeys (Saimiri sciureus). Each type of lesion was made in two groups of two animals each. Both animals of a group received the same type of lesion at the same day. Each group was recorded for 10 sessions of one hour before operation and 10 sessions after operation. Pre- and post-operative vocalizations were compared in respect to total number and acoustic structure. It was found that none of the lesions affected acoustic structure as judged by a sonagraphic analysis. However, lesions in the anterior supplementary motor area (at the level of the callosal genu) reduced the total vocalization number significantly. This decrease was essentially due to a drastic reduction of the so-called isolation peep, a long-distance contact call. The results suggest: (i) that the cortical face area is only involved in the control of learnt vocal utterances (such as human speech and song) but not in the production of genetically preprogrammed utterances (such as monkey calls and human pain groans); (ii) that the anterior cingulate cortex is necessary for the volitional initiation of vocalization but not for the initiation of calls in an emotional situation; (iii) that the posterior supplementary motor area does not play any role in vocal behaviour of monkeys; and (iv) that the anterior supplementary motor area is involved in the production of vocalizations which are not triggered directly by external events.     

Organization of rat vibrissa motor cortex and adjacent areas according to cytoarchitectonics, microstimulation, and intracellular stimulation of identified cells

The relationship between motor maps and cytoarchitectonic subdivisions in rat frontal cortex is not well understood. We use cytoarchitectonic analysis of microstimulation sites and intracellular stimulation of identified cells to develop a cell-based partitioning scheme of rat vibrissa motor cortex and adjacent areas. The results suggest that rat primary motor cortex (M1) is composed of three cytoarchitectonic areas, the agranular medial field (AGm), the agranular lateral field (AG1), and the cingulate area 1 (Cg1), each of which represents movements of different body parts. Vibrissa motor cortex corresponds entirely and for the most part exclusively to AGm. In area AG1 body/head movements can be evoked. In posterior area Cg1 periocular/eye movements and in anterior area Cg1 nose movements can be evoked. In all of these areas stimulation thresholds are very low, and together they form a complete representation of the rat's body surface. A strong myelinization and an expanded layer 5 characterize area AGm. We suggest that both the strong myelinization and the expanded layer 5 of area AGm may represent cytoarchitectonic specializations related to control of high-speed whisking behavior.     

The anterior cingulate cortex and the phonatory control in monkey and man

Electrical stimulation of the anterior cingulate cortex yields vocalization in the monkey. The elicited vocalizations seem to represent primary stimulus responses. Monkeys are not able to perform a vocal conditioning task after ablation of the anterior cingulate cortex. However, they can carry out a lever-pressing conditioning task following destruction of this area. It is hypothesized that the anterior cingulate cortex exerts the volitional control of species-specific vocalizations in monkey. The non-verbal emotional vocal utterances are considered to be the human homologue of monkey's vocalizations. Therefore, bilateral lesion of the anterior cingulate cortex in man should hamper the volitional control of emotional vocal utterances in man as it does in monkeys. One personal observation is reported where after a bilateral infarction of the anterior cingulate cortex the patient's voice showed a permanent lack of emotional expression. The anterior cingulate cortex seems to play the decisive role in the volitional verbalization of emotions.     

Activation likelihood estimation meta‐analysis of brain correlates of placebo analgesia in human experimental pain

Placebo analgesia (PA) is one of the most studied placebo effects. Brain imaging studies published over the last decade, using either positron emission tomography (PET) or functional magnetic resonance imaging (fMRI), suggest that multiple brain regions may play a pivotal role in this process. However, there continues to be much debate as to which areas consistently contribute to placebo analgesia‐related networks. In the present study, we used activation likelihood estimation (ALE) meta‐analysis, a state‐of‐the‐art approach, to search for the cortical areas involved in PA in human experimental pain models. Nine fMRI studies and two PET studies investigating cerebral hemodynamic changes were included in the analysis. During expectation of analgesia, activated foci were found in the left anterior cingulate, right precentral, and lateral prefrontal cortex and in the left periaqueductal gray (PAG). During noxious stimulation, placebo‐related activations were detected in the anterior cingulate and medial and lateral prefrontal cortices, in the left inferior parietal lobule and postcentral gyrus, anterior insula, thalamus, hypothalamus, PAG, and pons; deactivations were found in the left mid‐ and posterior cingulate cortex, superior temporal and precentral gyri, in the left anterior and right posterior insula, in the claustrum and putamen, and in the right thalamus and caudate body. Our results suggest on one hand that the modulatory cortical networks involved in PA largely overlap those involved in the regulation of emotional processes, on the other that brain nociceptive networks are downregulated in parallel with behavioral analgesia. Hum Brain Mapp, 2013. © 2011 Wiley Periodicals, Inc.     

Afferent connections of the medial frontal cortex of the rat. A study using retrograde transport of fluorescent dyes. I. Thalamic afferents

The present study of the medial frontal cortex of the rat was undertaken with two objectives. First, to compare the pattern of afferent thalamic neurons for each of the three subdivisions of the medial frontal cortex: the medial precentral (PrCm), dorsal anterior cingulate (ACd) and prelimbic (PL) areas. Second, to provide a firmer basis for anatomical comparisons of cortical regions between rat and monkey. Focal injections of retrogradely transported fluorescent tracers, true blue and diamidino yellow, were placed in different regions of the medial frontal cortex, to reveal the organization of afferent thalamic neurons. The PL area can be readily distinguished from PrCm and ACd areas because it receives afferents from a large number of neurons from both the medial and the lateral parts of the mediodorsal nucleus (MD) whereas only a few neurons, from the lateral MD exclusively, project to PrCm and ACd areas. Moreover, the paratenial and the paraventricular thalamic nuclei project only to the PL area, and the central medial nucleus projects mostly to the PL area. The ventrolateral nucleus projects only to the dorsal part of the medial frontal cortex. The rhomboid, reuniens, ventromedial, intralaminar, posterior and laterodorsal nuclei project to the whole medial frontal cortex. On the basis of these findings, the pattern of thalamic afferents to the PL area was compared to the pattern of thalamic afferents to cingulate and retrosplenial cortices in rat. The conclusion is that the PL area has a pattern of thalamic afferents which is different not only from those of PrCm and ACd areas but also from those of cingulate and retrosplenial cortices. On the basis of its rich innervation from the mediodorsal nucleus, the prelimbic area could very likely be a part of the prefrontal cortex of rat.     

Neuroanatomical correlates of therapeutic efficacy of low-frequency right prefrontal transcranial magnetic stimulation in treatment-resistant depression

Aims: Low‐frequency transcranial magnetic stimulation (TMS) to the right prefrontal cortex has been shown to be effective in treatment‐resistant depression. The aim of the present study was to investigate changes in regional cerebral blood flow (rCBF) after low‐frequency right prefrontal stimulation (LFRS), and neuroanatomical correlates of therapeutic efficacy of LFRS in treatment‐resistant depression. Methods: Twenty‐six patients with treatment‐resistant depression received five 60‐s 1‐Hz trains over the right prefrontal cortex, and 12 treatment sessions were administered during 3 weeks. Brain scans were acquired before and after LFRS using single photon emission computed tomography with ^99mTc‐ethyl cysteinate dimer. Severity of depression was assessed on the Hamilton Depression Rating Scale (HDRS). Results: Significant decreases in rCBF after LFRS were seen in the prefrontal cortex, orbitofrontal cortex, subgenual cingulate cortex, globus pallidus, thalamus, anterior and posterior insula, and midbrain in the right hemisphere. Therapeutic efficacy of LFRS was correlated with decreases in rCBF in the right prefrontal cortex, bilateral orbitofrontal cortex, right subgenual cingulate cortex, right putamen, and right anterior insula. Conclusion: The antidepressant effects of LFRS in treatment‐resistant depression may be associated with decreases in rCBF in the orbitofrontal cortex and the subgenual cingulate cortex via the right prefrontal cortex.     

Afferent fibers to the cingular vocalization region in the squirrel monkey

Three squirrel monkeys (Saimiri sciureus) received horseradish peroxidase injections in the anterior cingulate cortex at the level of the genu of the corpus callosum, a region yielding vocalization when electrically stimulated. Retrogradely labeled neurons were found at the cortical level within the dorsomedial and lateral prefrontal cortex (areas 9 and 10), orbital cortex (area 11), premotor cortex (areas 44, 6b, and 8), frontoparietal operculum, insula, cortex of the superior temporal sulcus, piriform cortex, subiculum, posterior cingulate, and retrosplenial cortex. Subcortical telencephalic projections came from the the claustrum, diagonal band of Broca, nucleus basalis Meynert, nuclei basalis lateralis and accessorius amygdalae, and cells at the periphery of globus pallidus. Diencephalic structures projecting to the anterior cingulate cortex were the thalamic nuclei anterior medialis, anterior ventralis, ventralis anterior, ventralis lateralis pars medialis, medialis dorsalis, pulvinaris medialis, centralis superior lateralis and limitans; the intralaminar nuclei paracentralis, centralis lateralis and parafascicularis; and the midline nuclei periventricularis, parataenialis, centralis superior, centralis inferior, centralis medialis, and reuniens. In the hypothalamus, projections came from the periventricular, lateral and posterior part, as well as the supramamillary nucleus. Midbrain afferent fibers came from the ventral tegmental area of Tsai, medial substantia nigra, reticular formation, area praerubralis, nucleus peripeduncularis, and periaqueductal gray. The most posterior labeled neurons were found in the locus ceruleus, dorsal tegmental nucleus of Gudden, nucleus annularis, nucleus centralis superior Bechterew, nucleus dorsalis raphae and the most dorsomedial part of the nucleus reticularis tegmenti pontis. Some of those projections have functional significance in the light of the hypothesis that the cingular cortex is involved in the volitional control of emotional reactions on the one hand and the influence of primary emotional reactions on intentional behavior on the other.     

Blockade of ovulation and release of LH in the rat by electrochemical stimulation of the frontal lobe cortex

The effect of stimulation of the frontal lobe cortex on the release of luteinizing hormone (LH) and ovulation was studied in female rats. Electrochemical stimulation (anodic DC) was applied through monopolar stainless-steel electrodes chronically implanted in the non-anesthetized freeely-behaving animals bearing plastic cannula inserted into the jugular vein for blood sampling.In rats, on the day of proestrus, stimulation (100 uA/30 sec) of the medical cortical surface in the superficial and deep layers of the medial precentral area and of the anterior cingulate area blocked ovulation in about 80% of the animals. A similar effect was seen when the stimulus was applied in the deep layers of the prelimbic and infralimbic areas. On the contrary, stimulation in the superficial layers of these latter two areas, as well as in the superficial and deep layers of the restrospenial cortex, did not affect normal ovulation. The preovulatory discharge of LH was blocked in the animals which failed to ovulate. The degree of inhibition exerted by the anterior cingulate area and the prelimbic area on ovulation and LH surge was proportional to the amount of current applied.Stimulation of the anterior cingulate area also blocked the release of LH induced by the injection of progesterone into ovariectomized estrogen-primed rats. Furthermore, electrochemical stimulation of the anterior cingulate area inhibited the rise of LH in the serum induced by electrical stimulation of the medial preoptic area of ovariectomized estrogen-injected rats, but it failed to affect that resulting from electrical stimulation of the medial basal hypothalamus.On the other hand, stimulation of the lateral cortical surface and the ventral cortex of the frontal lobe on the day of proestrus affected normal ovulation and LH surge only when the stimulus was applied in the agranular insular area which also exhibited an inhibitory action.It is concluded that certain areas of the frontal lobe cortex related to limbic structures exert an inhibitory influence on ovulation and LH secretion.     

Organization of the posterior parietal cortex in galagos: II. Ipsilateral cortical connections of physiologically identified zones within anterior sensorimotor region

We studied cortical connections of functionally distinct movement zones of the posterior parietal cortex (PPC) in galagos identified by intracortical microstimulation with long stimulus trains (～500 msec). All these zones were in the anterior half of PPC, and each of them had a different pattern of connections with premotor (PM) and motor (M1) areas of the frontal lobe and with other areas of parietal and occipital cortex. The most rostral PPC zone has major connections with motor and visuomotor areas of frontal cortex as well as with somatosensory areas 3a and 1‐2 and higher order somatosensory areas in the lateral sulcus. The dorsal part of anterior PPC region representing hand‐to‐mouth movements is connected mostly to the forelimb representation in PM, M1, 3a, 1‐2, and somatosensory areas in the lateral sulcus and on the medial wall. The more posterior defensive and reaching zones have additional connections with nonprimary visual areas (V2, V3, DL, DM, MST). Ventral aggressive and defensive face zones have reciprocal connections with each other as well as connections with mostly face, but also forelimb representations of premotor areas and M1 as well as prefrontal cortex, FEF, and somatosensory areas in the lateral sulcus and areas on the medial surface of the hemisphere. Whereas the defensive face zone is additionally connected to nonprimary visual cortical areas, the aggressive face zone is not. These differences in connections are consistent with our functional parcellation of PPC based on intracortical long‐train microstimulation, and they identify parts of cortical networks that mediate different motor behaviors. J. Comp. Neurol. 517:783–807, 2009. © 2009 Wiley‐Liss, Inc.     

Heterotopic Cortical Afferents to the Medial Prefrontal Cortex in the Rat. A Combined Retrograde and Anterograde Tracer Study

Cortical afferent projections towards the medial prefrontal cortex (mPFC) were investigated with retrograde and anterograde tracer techniques. Heterotopical afferent projections to the medial prefrontal cortex arise in secondary, or higher order, sensory areas, motor areas and paralimbic cortices. On the basis of these projections three subfields can be discriminated within the mPFC. (1) The ventromedial part of mPFC, comprising the pre- and infralimbic areas, receives mainly projections from the perirhinal cortex. (2) The caudal two-thirds of the dorsomedial PFC, comprising frontal area 2 and the dorsal anterior cingulate area, receives projections from the secondary visual areas, the posterior agranular insular area and the retrosplenial areas. (3) The rostral one-third of the dorsomedial PFC is the main recipient of projections from the somatosensory and motor areas and the posterior agranular insular area. The laminar distribution of cells projecting to the mPFC varies considerably in the different cortical areas, just as the laminar distribution of termination of their fibres within the mPFC does. It is concluded that the corticocortical connections corroborate with subcortical connectivity in attributing to the mediodorsal projection cortex of the rat functions which are comparable to those of certain prefrontal, premotor and anterior cingulate areas in the monkey.     

Fos expression following self-stimulation of the medial prefrontal cortex

Self-stimulation of the medial prefrontal cortex and medial forebrain bundle appears to be mediated by different directly activated fibers. However, reward signals from the medial prefrontal cortex do summate with signals from the medial forebrain bundle, suggesting some overlap in the underlying neural circuitry. We have previously used Fos immunohistochemistry to visualize neurons activated by rewarding stimulation of the medial forebrain bundle. In this study, we assessed Fos immunolabeling after self-stimulation of the medial prefrontal cortex. Among the structures showing a greater density of labeled neurons in the stimulated hemisphere were the prelimbic and cingulate cortex, nucleus accumbens, lateral preoptic area, substantia innominata, lateral hypothalamus, anterior ventral tegmental area, and pontine nuclei. Surprisingly, little or no labeling was seen in the mediodorsal thalamic nucleus or the locus coeruleus. Double immunohistochemistry for tyrosine hydroxylase and Fos showed that within the ventral tegmental area, a substantial proportion of dopaminergic neurons did not express Fos. Despite previous suggestions to the contrary, comparison of the present findings with those of our previous Fos studies reveals a number of structures activated by rewarding stimulation of both the medial prefrontal cortex and the medial forebrain bundle. Some subset of activated cells in the common regions showing Fos-like immunoreactivity may contribute to the rewarding effect produced by stimulating either site.     

Functional reorganization of intra‐ and internetwork connectivity in major depressive disorder after electroconvulsive therapy

Electroconvulsive therapy (ECT) is an effective and rapid treatment for major depressive disorder (MDD). However, the neurobiological underpinnings of ECT are still largely unknown. Recent studies have identified dysregulated brain networks in MDD. Therefore, we hypothesized that ECT may improve MDD symptoms through reorganizing these networks. To test this hypothesis, we used resting‐state functional connectivity to investigate changes to the intra‐ and internetwork architecture of five reproducible resting‐state networks: the default mode network (DMN), dorsal attention network (DAN), executive control network (CON), salience network (SAL), and sensory‐motor network. Twenty‐three MDD patients were assessed before and after ECT, along with 25 sex‐, age‐, and education‐matched healthy controls. At the network level, enhanced intranetwork connectivities were found in the CON in MDD patients after ECT. Furthermore, enhanced internetwork connectivities between the DMN and SAL, and between the CON and DMN, DAN, and SAL were also identified. At the nodal level, the posterior cingulate cortex had increased connections with the left posterior cerebellum, right posterior intraparietal sulcus (rpIPS), and right anterior prefrontal cortex. The rpIPS had increased connections with the medial PFC (mPFC) and left anterior cingulate cortex. The left lateral parietal had increased connections with the dorsal mPFC (dmPFC), left anterior prefrontal cortex, and right anterior cingulate cortex. The dmPFC had increased connection with the left anterolateral prefrontal cortex. Our findings indicate that enhanced interactions in intra‐ and internetworks may contribute to the ECT response in MDD patients. These findings provide novel and important insights into the neurobiological mechanisms underlying ECT.     

Common cortical and subcortical targets of the dorsolateral prefrontal and posterior parietal cortices in the rhesus monkey: evidence for a distributed neural network subserving spatially guided behavior

Common efferent projections of the dorsolateral prefrontal cortex and posterior parietal cortex were examined in 3 rhesus monkeys by placing injections of tritiated amino acids and HRP in frontal and parietal cortices, respectively, of the same hemisphere. Terminal labeling originating from both frontal and parietal injection sites was found to be in apposition in 15 ipsilateral cortical areas: the supplementary motor cortex, the dorsal premotor cortex, the ventral premotor cortex, the anterior arcuate cortex (including the frontal eye fields), the orbitofrontal cortex, the anterior and posterior cingulate cortices, the frontoparietal operculum, the insular cortex, the medial parietal cortex, the superior temporal cortex, the parahippocampal gyrus, the presubiculum, the caudomedial lobule, and the medial prestriate cortex. Convergent terminal labeling was observed in the contralateral hemisphere as well, most prominently in the principal sulcal cortex, the superior arcuate cortex, and the superior temporal cortex. In certain common target areas, as for example the cingulate cortices, frontal and parietal efferents terminate in an array of interdigitating columns, an arrangement much like that observed for callosal and associational projections to the principal sulcus (Goldman-Rakic and Schwartz, 1982). In other areas, frontal and parietal terminals exhibit a laminar complementarity: in the depths of the superior temporal sulcus, prefrontal terminals are densely distributed within laminae I, III, and V, whereas parietal terminals occupy mainly laminae IV and VI directly below the prefrontal bands. Subcortical structures also receive apposing or overlapping projections from both prefrontal and parietal cortices. The dorsolateral prefrontal and posterior parietal cortices project to adjacent, longitudinal domains of the neostriatum, as has been described previously (Selemon and Goldman-Rakic, 1985); these projections are also found in close apposition in the claustrum, the amygdala, the caudomedial lobule, and throughout the anterior medial, medial dorsal, lateral dorsal, and medial pulvinar nuclei of the thalamus. In the brain stem, both areas of association cortex project to the intermediate layers of the superior colliculus and to the midline reticular formation of the pons.(ABSTRACT TRUNCATED AT 400 WORDS)