Posterior Amygdala Research Articles

Enhanced Cue Reactivity to Cocaine Cues in Non-treatment Seeking Cocaine Smokers

Introduction: Cue reactivity is defined as an observable, classically conditioned response to drugs. Chronic cocaine use is associated with enhanced cue reactivity. Our aims were: (1) to evaluate reactivity to cocaine and neutral picture cues in non-treatment seeking chronic cocaine smokers who were abstinent from cocaine use for 72 hours and control participants using functional magnetic resonance imaging (fMRI), and (2) to assess whether cue reactivity related brain areas were correlated with subjective craving ratings. Method: fMRI data were collected from non-treatment seeking cocaine-smokers (29-53 yrs.; 15M; 5F) who were abstinent from cocaine smoking for 72 hours, and control participants (25-53 yrs.; 13M; 4F) using a Siemens 3T magnet while they took part in a cue viewing task that included cocaine and neutral cues. Participants also provided craving ratings while they viewed the cues. Results: Contrasting activation of cocaine smokers to that of controls revealed significantly greater activation in response to cocaine cues in the following brain areas: anterior cingulate gyrus, posterior cingulate gyrus, left insula, right amygdala, left precuneous, and bilateral orbitofrontal cortex, caudate, Para hippocampal gyrus, thalamus, frontal pole, and lingual gyrus. In contrast, when comparing cocaine smokers to controls no significant difference in activation to neutral cues was observed. Increased cue reactivity was not positively correlated with cocaine users’ subjective craving ratings. Conclusion: Enhanced cue reactivity reflects cocaine users’ increased salience to cocaine cues, and this enhancement may not indicate increased craving for the drug. Results have implications for treatment development. Future studies will examine how these cue reactivity related brain areas are causally related during viewing cocaine cues in cocaine users.

Oculographic analysis of nystagmus in orthostatic vertigo

Oculographic analysis of nystagmus in orthostatic vertigo

Different amygdala subregions mediate valence-related and attentional effects of oxytocin in humans

The neuropeptide oxytocin enhances the processing of positive social stimuli and improves the capacity to effectively attend the eye region of conspecifics. To investigate the neural basis of these effects, we combined intranasal oxytocin administration with high-resolution functional magnetic resonance imaging in a unique emotion classification task. Emotional faces were briefly presented while controlling for the initial fixation, and measuring subsequent eye movements. Oxytocin had differential effects on the activity of specific amygdala subregions. On the one hand, it attenuated activation in lateral and dorsal regions of the anterior amygdala for fearful faces but enhanced activity for happy expressions, thus indicating a shift of the processing focus toward positive social stimuli. On the other hand, oxytocin increased the likelihood of reflexive gaze shifts toward the eye region irrespective of the depicted emotional expression. This gazing pattern was related to an increase of activity in the posterior amygdala and an enhanced functional coupling of this region to the superior colliculi. Thus, different behavioral effects of oxytocin seem to be closely related its specific modulatory influence on subregions within the human amygdala.

Injection of Urocortin 3 into the ventromedial hypothalamus modulates feeding, blood glucose levels, and hypothalamic POMC gene expression but not the HPA axis

Urocortin 3 (Ucn 3) is a corticotropin-releasing factor (CRF)-related peptide with high affinity for the type 2 CRF receptor (CRFR2). Central administration of Ucn 3 stimulates the hypothalamic-pituitary-adrenal axis, suppresses feeding, and elevates blood glucose levels, suggesting that activation of brain CRFR2 promotes stress-like responses. Several CRFR2-expressing brain areas, including the ventromedial hypothalamus (VMH) and the posterior amygdala (PA), may be potential sites mediating the effects of Ucn 3. In the present study, Ucn 3 or vehicle was bilaterally injected into the VMH or PA, and food intake and plasma levels of ACTH, corticosterone, glucose, and insulin were determined. Food intake was greatly reduced in rats following Ucn 3 injection into the VMH. Ucn 3 injection into the VMH rapidly elevated plasma levels of glucose and insulin but did not affect ACTH and corticosterone secretion. Injection of Ucn 3 into the PA did not alter any of the parameters measured. We determined that the majority of CRFR2-positive neurons in the VMH were excitatory glutamatergic, and a subset of these neurons project to the arcuate nucleus of the hypothalamus (ARH). Importantly, stimulation of CRFR2 in the VMH increased proopiomelanocortin mRNA expression in the ARH. In conclusion, the present study demonstrates that CRFR2 in the VMH mediates some of the central effects of Ucn 3, and the ARH melanocortin system may be a downstream target of VMH CRFR2 neurons.

The effects of antipsychotic drugs administration on 5-HT1A receptor expression in the limbic system of the rat brain

Increasing evidence suggests that 5-HT1A receptors are involved in the pathophysiology and treatment of schizophrenia. This paper investigated 5-HT1A receptor mRNA expression and binding density in female rats treated with aripiprazole (2.25 mg/kg/day), olanzapine (1.5 mg/kg/day), haloperidol (0.3 mg/kg/day) or vehicle (control) orally three times/day for 1 or 12 weeks. Animals were sacrificed 48 h after the last administration. Aripiprazole significantly increased 5-HT1A receptor binding density by 33% in the CA1 region of the hippocampus and by 21% in the medial posterodorsal nuclei of posterior amygdala (MeP) compared to the control group after 1 week of treatment. Olanzapine significantly decreased 5-HT1A receptor binding density by 17–22% in Layers I–IV of the cingulate cortex after 1 week of treatment. Neither of these antipsychotic drugs affected 5-HT1A receptor binding density after 12 weeks drug treatment. As expected, haloperidol treatment did not have any significant effect on 5-HT1A binding density after 1 or 12 weeks of treatment. 5-HT1A receptor mRNA expression was not altered by antipsychotic treatment in any brain region. The results indicate that aripiprazole and olanzapine have differential effects on 5-HT1A receptor expression, which may contribute to their distinct profiles in improving negative symptoms and cognitive deficits in schizophrenia. Aripiprazole and olanzapine may produce adaptation and desensitization of 5-HT1A receptor expression after long term treatment.

Memory for friends or foes: The social context of past encounters with faces modulates their subsequent neural traces in the brain

Every day we encounter new people, interact with them, and form person impressions based on quick and automatic inferences from minimal contextual information. Previous studies have identified an extensive network of brain areas involved in familiar face recognition, but there is little evidence to date concerning the neural bases of negative vs. positive person impressions. In the present study, participants were repeatedly exposed to 16 unfamiliar face identities within a pseudo-interactive game context to generate a perception of either “friends” or “foes”. Functional magnetic resonance imaging (fMRI) was then performed during an old/new memory task to assess any difference in brain responses to these now familiar face identities, relative to unfamiliar faces. Importantly, whereas facial expressions were always emotional (either smiling or angry) during the encoding phase, they were always neutral during the memory task. Our results reveal that several brain regions involved in familiar face recognition, including fusiform cortex, posterior cingulate gyrus, and amygdala, plus additional areas involved in motivational control such as caudate and anterior cingulate cortex, were differentially modulated as a function of a previous encounter, and generally more activated when faces were perceived as “foes” rather than “friends”. These findings underscore that a key dimension of social judgments, based on past impressions of who may be supportive or hostile, may lead to long-lasting effects on memory for faces and thus influence affective reactions to people during a subsequent encounter even in a different (neutral) context.

Apamin increases 5-HT cell firing in raphe dorsalis and extracellular 5-HT levels in amygdala: A concomitant in vivo study in anesthetized rats

The family of calcium-activated slow-potassium (SK) channels comprises 3 members, the SK1, SK2 and SK3 channels, all expressed in neurons, known to mediate the slow-afterhyperpolarization occurring after action potentials. In rats, the SK2 and SK3 channels are expressed in the ascending monoaminergic systems, in particular in the serotonin (5-HT) neurons of the raphe dorsalis nucleus (RDN). In mammals the amygdala, a limbic structure involved in the control of emotion and mood, receives 5-HT-containing projections originating in the RDN. The aim of the present study was to investigate the role of SK channels in mediating the release of 5-HT in the amygdala. Apamin, a polypeptiditic compound with SK2–SK3 channel selectivity, was used to block the channels. A dual probing methodology with Nafion coated carbon-fiber micro-electrode (Nafion-mCFE) was implemented to measure concomitantly the extracellular levels of 5-HT in the amygdala and the firing rate of 5-HT neurons in the RDN of anesthetized rats. Subcutaneous administration of apamin increased both the extracellular 5-HT levels in the amygdala and the firing rate of RDN neurons at doses as low as 12.5 μg. The recorded RDN neurons were of 5-HT phenotype, according to electrophysiologic signature and to the effects observed with peripheral administration of 8-hydroxy-2-(d-n-propyl-amino) tetralin (8-OH-DPAT) a 5-HT 1A agonist known to selectively reduce the firing of 5-HT neurons in RDN. Increases of extracellular 5-HT levels in the amygdala were also seen when apamin was microinjected into the RDN, suggesting a role for 5-HT neurons of the RDN as target for subcutaneously administered apamin. The confirmation of the involvement of 5-HT neurons projecting from RDN to the amygdala in mediating the effects of apamin was obtained by micro-infusion of tetradotoxine into the bundle of 5-HT ascending fibers located in the region of the posterior amygdala. Attenuation of 5-HT release in the amygdala was observed in presence of increased firing of 5-HT neurons of the RDN. In conclusion, the dual CFE micro-sensor probing approach was used to show that apamin increases 5-HT release in the amygdala by increasing the firing rate of 5-HT neurons in RDN.

Neural systems mediating field and observer memories

Autobiographical memories are more imbued with affect when one adopts a first-person or field perspective during event retrieval, rather than a third-person or observer perspective. We combined fMRI, event narratives, and subjective ratings to identify the neural networks engaged with field versus observer memories for real-world events. Our results revealed significant decreases in bilateral insula and left somato-motor activity during the recall of observer memories, paired with a small relative increase in right posterior amygdala activity coincident with the recall of field memories. Notably, these regions showed no overlap with those areas mediating the narrative content and subjective emotionality of the remembered events. Our findings suggest that the emotionality of field relative to observer memories is not simply driven by increased limbic activation when one adopts a first-person retrieval perspective. Rather, there is also a significant reduction in one's cortical representations of the physical, embodied self when a third-person--or disembodied--perspective is taken at retrieval.

Gastric distention activates satiety circuitry in the human brain

Gastric distention during meal ingestion activates vagal afferents, which send signals from the stomach to the brain and result in the perception of fullness and satiety. Distention is one of the mechanisms that modulates food intake. We measured regional brain activation during dynamic gastric balloon distention in 18 health subjects using functional magnetic resonance imaging and the blood oxygenation level-dependent (BOLD) responses. The BOLD signal was significantly changed by both inflow and outflow changes in the balloon's volume. For lower balloon volumes, water inflow was associated with activation of sensorimotor cortices and right insula. The larger volume condition additionally activated left posterior amygdala, left posterior insula and the left precuneus. The response in the left amygdala and insula was negatively associated with changes in self-reports of fullness and positively with changes in plasma ghrelin concentration, whereas those in the right amygdala and insula were negatively associated with the subject's body mass index. The widespread activation induced by gastric distention corroborates the influence of vagal afferents on cortical and subcortical brain activity. These findings provide evidence that the left amygdala and insula process interoceptive signals of fullness produced by gastric distention involved in the controls of food intake.

Localized volume reduction in prefrontal, temporolimbic, and paralimbic regions in schizophrenia: an MRI parcellation study

Functional and structural abnormalities of the anterior cingulate gyrus (ACG) in patients with schizophrenia have been repeatedly reported. However, one remaining issue is whether gray matter volume reduction in ACG exists to an extent comparable with, or even in excess of, that in other prefrontal and temporolimbic regions. High-spatial-resolution magnetic resonance imaging was performed on patients with schizophrenia ( n=27) and on age-, gender-, and parental socioeconomic-status-matched healthy control subjects ( n=27). After the gray and white matter were semiautomatically segmented, whole prefrontal and temporal lobes were manually parceled into 15 subregions-by-two hemispheres (30 regions of interest) constituting seven prefrontal gray matter regions, six temporal gray matter regions, the prefrontal white matter, and the temporal white matter. Compared with healthy subjects, schizophrenic patients showed significant gray matter volume reduction in the bilateral ACG, this being the largest effect size (left, 0.84; right, 0.56) among all the regions examined. There were also significant gray matter volume reductions in the bilateral posterior STG, bilateral inferior frontal gyrus, left posterior amygdala–hippocampal complex (mostly hippocampus), and the left insula. These results suggest that gray matter volume reductions in the ACG are prominent among prefrontal and temporolimbic regions in patients with schizophrenia. These findings indicate the importance of ACG abnormalities in the pathophysiology of schizophrenia.

Appetitive and Aversive Olfactory Learning in Humans Studied Using Event-Related Functional Magnetic Resonance Imaging

We combined event-related functional magnetic resonance imaging (fMRI) with olfactory classical conditioning to differentiate the neural responses evoked during appetitive and aversive olfactory learning. Three neutral faces [the conditioned stimuli (CS+)] were repetitively paired with pleasant, neutral, or unpleasant odors [the unconditioned stimuli (UCS)] in a partial reinforcement schedule. A fourth face was never paired to odor [the nonconditioned stimulus (CS-)]. Learning-related neural activity, comparing unpaired (face only) CS+ stimuli with CS-, showed valence-independent activations in rostral and caudal orbitofrontal cortex (OFC). Medial OFC responded to the appetitive (app) CS+, whereas lateral OFC responded to the aversive (av) CS+. Within nucleus accumbens, neural responses showed divergent activation profiles that increased with time in response to the appCS+ but decreased in response to the avCS+. In posterior amygdala, responses were elicited by the appCS+, which habituated over time. In temporal piriform cortex, neural responses were evoked by the avCS+, which progressively increased with time. These results highlight regional and temporal dissociations during olfactory learning and imply that emotionally salient odors can engender cross-modal associative learning. Moreover, the findings suggest that the role of human primary (piriform) and secondary olfactory cortices transcends their function as mere intermediaries of chemosensory information processing.

Human Amygdala Responses to Fearful Eyes

Fearfulfacial expressions evoke increased neural responses in human amygdala. We used event-related fMRI to investigate whether eye or mouth components of a fearful face are critical in evoking this increased amygdala activity. In addition to prototypical fearful (FF) and neutral (NN) faces, subjects viewed two types of chimerical face: fearful eyes combined with a neutral mouth (FN), and neutral eyes combined with a fearful mouth (NF). FF faces evoked specific responses in left anterior amygdala. FN faces evoked responses in bilateral posterior amygdala and superior colliculus. Responses in right amygdala, superior colliculus, and pulvinar exhibited significant time × condition interactions with respect to faces with fearful eyes (FF, FN) vs neutral eyes (NF, NN). These data indicate that fearful eyes alone are sufficient to evoke increased amygdala activity. In addition, however, left amygdala displayed discriminatory responses to fearful eyes in different configural contexts (i.e., in FF and FN faces). These results suggest, therefore, that human amygdala responds to both feature-specific and configural aspects of fearful facial expressions.

Decreased left amygdala and hippocampal volumes in young offspring at risk for schizophrenia

Abnormalities in the structural integrity and connectivity of the medial temporal and the prefrontal cortex are well documented in schizophrenia, but it is unclear if they represent premorbid indicators of neuropathology. Studies of young relatives at high-risk for schizophrenia (HR) provide an opportunity to clarify this question. We herein provide data from a magnetic resonance imaging (MRI) study of these structures in young offspring of schizophrenia patients. A series of 17 young HR offspring of schizophrenic patients were compared with 22 healthy comparison subjects (HC). Morphometric comparisons of the right and left dorsolateral prefrontal cortex (DLPFC), and the anterior and posterior amygdala–hippocampal (A–H) complex were conducted using high-resolution whole brain T 1 weighted brain images. Compared with the HC group, HR subjects had significant decreases in intracranial volume. The volumes of the left anterior and posterior A–H complex were reduced in the HR subjects after adjusting for intracranial volume. HR subjects also showed a significant leftward (Right>Left) asymmetry of the anterior A–H complex compared to the HC subjects. No significant changes were seen in the DLPFC. Thus, lateralized alterations in the volume of the left A–H complex are evident in unaffected young offspring of schizophrenia patients and may be of neurodevelopmental origin. Follow-up studies are needed to examine the predictive value of these measures for future emergence of schizophrenia in at-risk individuals.

Drs. De Bellis and Keshavan Reply

Back to table of contents Previous article Next article Letter to the EditorFull AccessDrs. De Bellis and Keshavan ReplyMICHAEL D. DE BELLIS, M.D., M.P.H., and MATCHERI S. KESHAVAN, M.D., MICHAEL D. DE BELLISSearch for more papers by this author, M.D., M.P.H., and MATCHERI S. KESHAVANSearch for more papers by this author, M.D., Pittsburgh, Pa.Published Online:1 May 2001https://doi.org/10.1176/appi.ajp.158.5.821AboutSectionsView EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail To the Editor: We appreciate the comments by Mr. Tae and Dr. Hong. The amygdala and hippocampus are often hard to differentiate from each other, even at a histologic level. On the basis of earlier work in studies of child and adolescent psychiatry (1–4), we utilized a landmark method to differentiate these structures. In this method, the slice showing the most anterior mammillary bodies is used as the amygdala-hippocampus boundary. The disadvantage of this landmark method is that measures of the anterior hippocampus may include some of the posterior amygdala on a small number of slices. As described in our article and outlined in Figure 2, our measurement of the anterior hippocampus can potentially include a small part of the posterior amygdala. Therefore, we explored whether this difference is related to the few slices that contain both the amygdala and hippocampus. Secondary analysis of our results revealed that the smaller hippocampal volumes seen in subjects with adolescent-onset alcohol use disorders was not due to our decision to use this landmark method (total hippocampal volume adjusted for intracranial volume: F=6.27, df=1, 33,p<0.02).As stated by Mr. Tae and Dr. Hong, recent studies in adult psychiatry show that visualizing the hippocampus perpendicular to its long axis, a modification of our landmark method, has the advantage of separating the posterior amygdala from the anterior hippocampus and the disadvantage of including the adjacent entorhinal cortex in the measurement of the anterior amygdala (5–7). We agree that MRI measurement methodology is an important issue to keep in mind when comparing data across different studies. Since standardizing hippocampal measures across development is an important issue, we have began utilizing both methods in our image analysis.

Androgen receptor-immunoreactivity in the forebrain of the Eastern Fence lizard ( Sceloporus undulatus)

Androgen receptor (AR) distribution in the lizard forebrain and optic tectum was examined using PG21 immunohistochemistry. In the male Eastern Fence lizard, AR-immunoreactive (-ir) nuclei were observed in the medial preoptic area, ventromedial and arcuate hypothalamic nuclei, periventricular hypothalamus, premammillary nucleus, bed nucleus of the stria terminalis, and ventral posterior amygdala. Punctate immunostaining of neuronal processes (axons and/or dendrites) was concentrated in the cortex, hypothalamus, and optic tectum. AR-ir nuclei in the female brain were confined to the ventral posterior amygdala and ventromedial hypothalamic nucleus. The AR distribution in the lizard brain is similar to that reported for other vertebrate classes. Sex differences in AR-immunoreactivity may contribute to sex-specific behaviors in the Eastern Fence lizard.

Amygdalo-hypothalamic projections in the lizard Podarcis hispanica: a combined anterograde and retrograde tracing study.

The cells of origin and terminal fields of the amygdalo-hypothalamic projections in the lizard Podarcis hispanica were determined by using the anterograde and retrograde transport of the tracers, biotinylated dextran amine and horseradish peroxidase. The resulting labeling indicated that there was a small projection to the preoptic hypothalamus, that arose from the vomeronasal amygdaloid nuclei (nucleus sphericus and nucleus of the accessory olfactory tract), and an important projection to the rest of the hypothalamus, that was formed by three components: medial, lateral, and ventral. The medial projection originated mainly in the dorsal amygdaloid division (posterior dorsal ventricular ridge and lateral amygdala) and also in the centromedial amygdaloid division (medial amygdala and bed nucleus of the stria terminalis). It coursed through the stria terminalis and reached mainly the retrochiasmatic area and the ventromedial hypothalamic nucleus. The lateral projection originated in the cortical amygdaloid division (ventral anterior and ventral posterior amygdala). It coursed via the lateral amygdalofugal tract and terminated in the lateral hypothalamic area and the lateral tuberomammillary area. The ventral projection originated in the centromedial amygdaloid division (in the striato-amygdaloid transition area), coursed through the ventral peduncle of the lateral forebrain bundle, and reached the lateral posterior hypothalamic nucleus, continuing caudally to the hindbrain. Such a pattern of the amygdalo-hypothalamic projections has not been described before, and its functional implications in the transfer of multisensory information to the hypothalamus are discussed. The possible homologies with the amygdalo-hypothalamic projections in mammals and other vertebrates are also considered.

Temporal lobe lesion-induced obesity in rats: An anatomical investigation of the posterior amygdala and hippocampal formation

Bilateral lesions centered in the posterodorsal amygdala of female rats resulted in hyperphagia and excessive weight gain (mean = 65.3 g in 20 days compared to 6.8 g for control animals). The brain damage always extended posteriorly into the ventral hippocampal formation. However, lesions that were confined to the ventral hippocampus or amygdalohippocampal area had no effect on daily food intake or body weight, nor did lesions at any other hippocampal site. In a previous study, lesions of the basolateral, corticomedial, and anterior groups of amygdaloid nuclei failed to affect food intake or body weight. It is concluded that the posterodorsal aspect of the amygdala is the critical site for this experimentally induced obesity syndrome. New coordinates for the effective site are presented.

Afferent projections to the ventromedial hypothalamic nucleus in a lizard, Gekko gecko.

Afferent projections to the ventromedial hypothalamic nucleus (VMH) of a lizard, Gekko gecko, were studied with wheat germ agglutinin conjugated to horseradish peroxidase. Results indicated that the shell and core areas of the VMH are largely innervated by different telencephalic nuclei but similar brain-stem nuclei. The common brainstem projections include the superior raphe, two isthmal populations (the ventral isthmal nucleus and parvocellular isthmal nucleus), and a dorsal thalamic projection from the posteroventral nucleus. Brainstem projections to the shell but not to the core of the VMH arise from the laterodorsal tegmental nucleus. Telencephalic projections to the VMH core originate from the ventrolateral septum, centromedial DVR, lateral amygdala, medial amygdala, interstitial amygdala, and ventral anterior amygdala. Telencephalic projections to the VMH shell come from the ventral pallidum, the anterior septal nucleus, the dorsal septal nucleus, the striatoamygdalar area, and the ventral posterior amygdala. These results, combined with connectional and topological information from other studies in amphibians, reptiles, and mammals, will be used to suggest homologies between a number of limbic areas, including several amygdalar nuclei.

The effect of kindling of different nuclei in the left and right amygdala on anxiety in the rat

The effects on rodent anxiety of kindling in the medial or basolateral amygdaloid nuclei in each hemisphere were examined. Anxiety was measured using the hole board and elevated plus maze tests. The animals were kindled in medial or basolateral amygdalas, of either the left or right hemisphere. Controls had electrodes implanted in comparable areas, but were not kindled. Analysis of electrode location showed that some animals were kindled in amygdaloid nuclei other than medial or basolateral amygdala. These animals were labelled outliers. Kindling of the medial/basolateral amygdala in the left hemisphere decreased anxiety for at least 1 week after the last kindled seizure. Right hemisphere medial/basolateral kindling tended to increase anxiety. Outlier-kindled rats were less anxious than their controls regardless of hemisphere 1 week after their last kindled seizure. Clear anxiogenic effects were not likely seen in the right hemisphere in this study because of the electrode locations. The degree of anxiety following kindling was correlated with electrode location in the anterior-posterior plane. More anterior foci in the amygdala were associated with more anxiety. More posterior amygdala foci were associated with less anxiety. These findings point to the importance of kindled focus in the amygdala for behavioral effect. Future research should carefully control the location of kindled foci when investigating effects of amygdala kindling on anxiety and other behaviors.

Projections of the nucleus accumbens in the cat.

Due to the recent advances in knowledge on the function of the limbic system it would be wise to consider this system as being widely distributed throughout the diencephalic and mesencephalic levels as well as the forebrain. Numerous regions have been discovered that are related to the limbic structures in anatomical and functional respects. According to Koikegami et al. (1967), it would be adequate to divide this system into two main categories--the major limbic rim or the structure proper and the paralimbic structures. The former defined phylogenetically and ontogenetically as those structures around the third ventricle such as: the hippocampus, septum, dentate gyrus, fimbria hippocampi, anterior and posterior cingulate gyri, area paraolfactoria, amygdala and Diagonal Band of Broca. The paralimbic structures may represent those brain regions, which have direct connections or functional correlations with the limbic formation proper. These areas include the posterior orbital gyrus, insula, nucleus accumbens, head of the caudate, nucleus habenula, nucleus interpendencularis, nucleus pulvinaris thalami, intralaminar and anterior thalamic nucleus, preoptic area, hypothalamic nuclei, mammillary body, subthalamus, limbic midbrain area of Nauta, temporal lobe pole, superior temporal gyrus, praecuneus, nucleus dorsalis et profundis tegmenti of Gudden and claustrum. In the present paper we will deal with the projections of the nucleus accumbens. This nucleus was described by Meynert (1872) as the anterior polar region of the caudate nucleus. Kappers describes the nucleus accumbens in 1908 as the nucleus accumbens septi and considers it as a part of the striatum. Later on, the histological studies of Brochaus (1942) relate a part of the nucleus with olfactory functions, and he describes another part, which is very well developed in microsmatic mammals and in anosmic mammals like the dolphin. Szteyn (1960) describes two main areas, the accumbens septi and the accumbens caudate. Nevertheless, the accumbens constitutes a very important region of the paralimbic system and seems to play an important role in some behavioral patterns.