Amygdaloid-Hippocampal Convergence

Cross references:   Nucleus Accumbens Septi    Accumbens Input     
Hippocampus     Subiculum   

Note:  The references on this page were obtained through more than one search. 
I have combined the list of references in chronological order without removing the indication of where they ranked in the search.   Thus "xx<yy" indicates the xx reference out of the yy references obtained in that search.  Duplicates  have not been repeated.   

Searching PubMed for "amygdala hippocampus convergence " revealed 43 references:    

Searching PubMed for "amygdala hippcoampus connectivity" revealed 341 references which rose to 354 while I was reviewing them.   

Searching PubMed for "mulder ab" revealed 72 references:  

Searching PubMed for the articles that were similar to: 1998  60<Mulder AB 
revealed 131 references which subsequently rose to 133:   
    Note:  These articles are sorted by Publication Date rather than by Link, which is the default. 

    Comparing the two searches  
Searching PubMed for "amygdala hippocampus convergence " revealed 43 references:    
Searching PubMed for "amygdala hippcoampus connectivity" revealed 341 references which rose to 354 while I was reviewing them.   

    illuminates an important difference between "connectivity" and "convergence". 

    "connectivity" = all connections in all directions 
    "convergence" = two outputs, both providing input to the same recipient; 
            in particular,  AMG+HIP>NAC 

1980    126<131 
Convergence of excitatory amygdaloid and hippocampal input in the nucleus accumbens septi.   
No Abstract but:   
    305 Related citations   
    and 2 Cited by's. 
(Titles of refs 201-305 sorted by publication date scanned.) 
    My comment
The title specifies that both the amygdaloid and the hippocampal inputs are excitatory.  There is no mention of an inhibitory input.  This could be either very important or just the limitation of the early report date. 

1980    125<131 
Hippocampal influence on amygdala unit activity in awake squirrel monkeys.   
    "The basomedial nucleus appears to receive the most potent hippocampal influence. Response characteristics are consistent with a hypothesized relay of nonfornix hippocampal influences on basal forebrain and hypothalamus via the basomedial nucleus."  
    My comment
Judging from the title, the focus is on
HIP>AMG rather than HIP+AMG>NAC. 

1988    36<43   
A comparison of the efferents of the amygdala and the hippocampal formation in the rhesus monkey: I. Convergence in the entorhinal, prorhinal, and ...   
    "The present report focuses on the complementary and convergent projections of the amygdala and hippocampal formation to the entorhinal and perirhinal cortices."  
    "This pattern of hippocampal and amygdaloid projections to the entorhinal and perirhinal cortices indicates that these cortices constitute a region of potentially extensive interaction between the amygdala and the hippocampus."  
    My comment

Distribution of amygdala input to the nucleus accumbens septi: An electrophysiological investigation | SpringerLink 
    Only Abstract available online for free.     
    "The nucleus accumbens septi (NAS) receives afferent input from the amygdala via the stria terminalis and from the hippocampus via the fimbria.  
    Extracellular recordings from 196 NAS neurons in halothane-anesthetized rats revealed heterogeneous response patterns following stimulation of the amygdala. The observation that 30% of anterior NAS units but only 16% of posterior NAS units were responsive to amygdala stimulation suggested a topographical arrangement of amygdala efferents.  
    Comparing the effects of amygdala and fimbria stimulation revealed that the two afferent pathways converge onto individual NAS neurons, but that the two sites of stimulation can differentially influence other neurons. The present results clarify the topographical distribution of amygdala input to the NAS, confirm that inputs from two limbic structures are integrated within the NAS, and further illustrate the electrophysiological heterogeneity of NAS neurons."  
    Very important
"Comparing the effects of amygdala and fimbria stimulation revealed that the two afferent pathways converge onto individual NAS neurons"   

1995    104<131         
Synaptic interactions among excitatory afferents to nucleus accumbens neurons: hippocampal gating of prefrontal cortical input. 
    "The interactions among excitatory inputs arising from the prefrontal cortex, amygdala, and hippocampus, and innervating nucleus accumbens neurons were studied using in vivo intracellular recording techniques.  
    Neurons recorded in the accumbens displayed one of three activity states: (1) silent, (2) spontaneously firing at low, constant rates, or (3) a bistable membrane potential, characterized by alternating periods of activity and silence occurring in concert with spontaneous transitions between two steady-state membrane potentials (average, -77.3 +/- 7.1 mV base, -63.0 +/- 7.4 mV plateau). These neurons also exhibited a high degree of convergence of responses elicited by stimulation of each of the three excitatory inputs tested.  
    Activation of hippocampal afferents, but not cortical, amygdaloid, or thalamic afferents, induced bistable cells to switch to the depolarized (active) state.  
    In contrast, no bistable cells were encountered in the nucleus accumbens following an acute transection of the fornix. Furthermore, microinjection of lidocaine in the vicinity of the hippocampal afferents at the level of the fornix caused a reversible elimination of the plateau phase in bistable cells.  
    These data suggest that hippocampal input is necessary for accumbens neurons to enter a depolarized, active state. Furthermore, activation of prefrontal cortical inputs fail to evoke spike firing in accumbens neurons unless they are in this active state.  Consequently, the hippocampus appears to be capable of gating prefrontal corticoaccumbens throughput."  
    Free Full Text:   
    My comment
The focus is on excitatory inputs.  No mention of inhibitory inputs. 

1995   103<131
Patterns of convergence and segregation in the medial nucleus accumbens of the rat: relationships of prefrontal cortical, midline thalamic, and basal amygdaloid afferents.     
    See:  Accumbens Input

1996 101<131  
Neurophysiology of converging synaptic inputs from the rat prefrontal cortex, amygdala, midline thalamus, and hippocampal formation onto single neurons of the caudate/putaman  and nucleus accumbens.   
    "Neurophysiological responses mediated by projections from five telencephalic and diencephalic regions
        (the infra- and prelimbic portions of the prefrontal cortex,
        midline and intralaminar thalamic nuclei,
        entorhinal cortex and
to the caudate/putamen (CPu) and nucleus accumbens (Acb) of the dorsal and ventral striatum were studied
in chloral-hydrate-anesthetized rats."  
Both extra- and intracellular in vivo recording techniques were used. A retrograde tracer (wheatgerm agglutinin-apo-horseradish peroxidase-5 nm colloidal Gold) was deposited in some animals in the vicinity of recording sites to confirm that stimulating electrodes were located near cells that projected to the striatum.  
    Electrical stimulation of these five regions, respectively, evoked excitatory responses in 60%, 22%, 51%, 25%, and 17% of striatal neurons.  
    Some responses, particularly with thalamic stimulation, showed short-term frequency potentiation in which 5/s stimulation increased the probability of spike firing. About half of responsive cells showed convergent excitation to more than one stimulating site.  
    It was possible with convergent excitatory responses to show synaptic interactions: simultaneous activation of more than one site produced spatial and temporal summation to increase the probability of spike firing.  
    Up to 5-way convergence onto single striatal neurons and up to 3-way interactions could be shown. These results indicate that functional influences from the hippocampal formation can converge with other excitatory input onto single striatal neurons to effect synaptic integration. 

    My comment
Again excititory but not inhibitory responses. 
     To striatum not NAC.   

1996    98<131
[Topographic organization of the ventral striatum afferent projection from amygdaloid complex and hippocampal formation].   
    "Retrograde tracers were injected into the different regions of the ventral (limbic) striatum and dorsolateral (sensorimotor) striatum."  
    "In contrast to the ventral striatum, the dorsolateral striatum received no projection from the amygdala or the hippocampus."  

1998  60<Mulder AB   
Electrophysiology of the hippocampal and amygdaloid projections to the nucleus accumbens of the rat: convergence, segregation, and interaction of inputs. 
    "The nucleus accumbens (Nacb) receives inputs from hippocampus and amygdala but it is still unclear how these inputs are functionally organized and may interact. The interplay between these input pathways was examined using electrophysiological tools in the rat, in vivo, under halothane anesthesia.  
    After fornix/fimbria stimulation (Fo/Fi, subicular projection fibers to the Nacb), mono- and polysynaptically driven single units were recorded in the medial shell/core regions of the Nacb and in the ventromedial caudate putamen.  
    Monosynaptically driven neurons by basolateral amygdala (BLA) stimulation were found in the medial shell/core and in the ventrolateral shell/core regions.  
    In the areas of convergence (medial shell/core), paired activation of BLA followed by that of Fo/Fi resulted in an enhancement of the Fo/Fi response, whereas stimulation in the reverse order, Fo/Fi followed by BLA, led to a depression of the BLA response.  
    In addition to these patterns of interactions, the tetanization of the Fo/Fi to Nacb pathway caused a homosynaptic decremental (long-term) potentiation in the Nacb, accompanied by a heterosynaptic (long-term) depression of the nontetanized BLA to Nacb pathway.  
    We postulate that the hippocampal inputs may close a "gate" for the amygdala inputs, whereas the gate is opened for the hippocampus inputs by previous amygdalar activity. These opposite effects on the Nacb neuronal populations should be taken into account when interpreting behavioral phenomena, particularly with respect to the contrasting effects of the amygdala and the hippocampus in locomotion and place learning."  
    My comment:  
    "In the areas of convergence (medial shell/core), paired activation of BLA followed by that of Fo/Fi resulted in an enhancement of the Fo/Fi response, whereas stimulation in the reverse order, Fo/Fi followed by BLA, led to a depression of the BLA response."      
    If BLA = need for behavior and Fo/Fi = memory then BLA>Fo/Fi = need>fulfillment.  I don't have a ready interpretation of Fo/Fi>BLA. 
    131 Similar articles   
    41 Cited by's  

    Free Full Text:  
    Note:  This reference is from a photocopy I made almost 10 years ago.  I've been carrying the idea around with me ever since.    

2001    70<131     Free Article   
Modulation of hippocampal and amygdalar-evoked activity of nucleus accumbens neurons by dopamine: cellular mechanisms of input selection. 
    "Inputs from multiple sites in the telencephalon, including the hippocampus and basolateral amygdala (BLA), converge on neurons in the nucleus accumbens (NAc), and dopamine (DA) is believed to play an essential role in the amplification and gating of these different limbic inputs.
    The present study used extracellular single-unit recordings of NAc neurons in combination with chronoamperometric sampling of mesoaccumbens DA efflux to assess the importance of DA in the integration of different limbic inputs to the NAc.    
    Tetanic stimulation of the fimbria potentiated hippocampal-evoked firing activity of NAc neurons and increased DA extracellular levels. Systemic administration of the D(1) receptor antagonist SCH23390 or the NMDA receptor antagonist CPP abolished the potentiation of hippocampal-evoked activity and produced a D(2) receptor-mediated suppression of evoked firing.    
    In neurons that received converging input from the hippocampus and BLA, fimbria tetanus potentiated hippocampal-evoked firing activity and suppressed BLA-evoked activity in the same neurons. Both D(1) and NMDA receptors participated in the potentiation of fimbria-evoked activity, whereas the suppression of BLA-evoked activity was blocked by either D(1) receptor antagonism with SCH23390 or the adenosine A(1) antagonist 8-cyclopentyl-1,2-dimethylxanthine.   
    Coincidental tetanus of both the fimbria and BLA resulted in potentiation of both inputs, indicating that DA and adenosine-mediated suppression of BLA-evoked firing was activity-dependent.  
    These data suggest that increases in mesoaccumbens DA efflux by hippocampal afferents to the NAc play a critical role in an input selection mechanism, which can ensure preferential responding to the information conveyed from the hippocampus to the ventral striatum."   
Free full text:   

2001    69<131      Free Article   
Modulation of hippocampal long-term potentiation by the amygdala: a synaptic mechanism linking emotion and memory.     
    "The activity-dependent facilitation of hippocampal LTP by the basomedial and basolateral amygdala may be a synaptic mechanism underlying memory enhancement associated with emotions."  

2002    61<131
Aging impairs amygdala-hippocampus interactions involved in hippocampal LTP.   
    "These results suggest that deficient synaptic plasticity and memory functions in aged animals might be caused, in part by impaired mechanisms of heterosynaptic reinforcement."  

2002    58<131 
Comparison of hippocampal, amygdala, and perirhinal projections to the nucleus accumbens: combined anterograde and retrograde tracing study in the Macaque brain.   
    "Amygdala and subicular (hippocampal) projections overlapped most completely in the medial division of nucleus accumbens."  

2003   13<43      Free full text   
Convergence and interaction of hippocampal and amygdalar projections within the prefrontal cortex in the rat.   
    "The orbital and medial prefrontal cortex (OMPFC) receives inputs from the CA1/subicular (CA1/S) region of the ventral hippocampus and the basolateral nucleus of the amygdala (BLA). ... OMPFC neurons driven by CA1/S or BLA stimulation were more frequently encountered in the ventral portion of the prelimbic (v-PrL) and infralimbic cortex (IL)."    
    "From these studies, we concluded that excitatory and inhibitory inputs from the hippocampus and amygdala converge and interact in the v-PrL and IL. Furthermore, the results indicate that simultaneous activation of hippocampal and amygdalar neurons may be important for amplification of OMPFC neuronal activity."  
    My comments
1.  As far as I can remember, this is the first and only reference which mentions inhibitory, as opposed to excitatory, inputs from the hippocampus and amygdala.  Although the referenced inputs were to the cortex rather than the accumbens, this is still noteworthy. 
2.  BLA+HIP>Ctx. 

2003    50<77  or   52<131 
Individual nucleus accumbens-projection neurons receive both basolateral amygdala and ventral subicular afferents in rats.  
    "The nucleus accumbens is regarded as the limbic-motor interface, in view of its limbic afferent and somatomotor and autonomic efferent connections.  
    Within the accumbens, there appear to be specific areas in which limbic afferent fibres, derived from the hippocampus and the amygdala, overlap. These afferent inputs have been suggested to converge monosynaptically on cells within the accumbens and are hypothesized to play a role in paradigms such as conditioned place preference.  
    Convergence between inputs from basolateral amygdala and hippocampus can be demonstrated with electrophysiological recording methods, but these do not conclusively preclude polysynaptic mechanisms. We examined the synaptic input to the projection neurons of the accumbens, the medium-sized densely spiny neurons.  
    We labelled the projection neurons with a small injection of biotinylated dextran amine into the accumbens, and the afferents from the basolateral amygdala and ventral subiculum of the hippocampus with injections of biotinylated dextran amine and Phaseolus vulgaris-leucoagglutinin respectively, and revealed the anterogradely labelled fibres with different chromogens. The labelled accumbens-projection neurons were studied with correlated light and electron microscopy for identified monosynaptic inputs.  
    With this technique we have demonstrated anatomically that monosynaptic convergence between the ventral subicular region of the hippocampus and the basolateral region of the amygdala occurs at the level of the proximal as well as distal dendrites. Finally, we suggest that these anatomical arrangements may represent the framework for the integrative role that has been assigned to the accumbens."        

    269 Related citations:   
    47 Cited by's: 
    "Within the accumbens, there appear to be specific areas in which limbic afferent fibres, derived from the hippocampus and the amygdala, overlap"  
    My comment:   
    This supports my hypothesis that the accumbens facilitates behavior when the needs influencing the amygdala match the memories, provided by the hippocampus, of how similar needs were met.       

2003    44<131
Basolateral amygdala efferents to the ventral subiculum preferentially innervate pyramidal cell dendritic spines.   
    "The basolateral amygdala and the ventral subiculum of the hippocampal formation are two of the major limbic-related regions within the brain, both of which project heavily to the nucleus accumbens. ... These afferent inputs have been suggested to converge monosynaptically on cells within the accumbens and are hypothesised to play a role in functions such as affective motivational behaviour.  
    Convergence between inputs from the basolateral amygdala and the hippocampus at the level of the accumbens can be demonstrated with electrophysiological recording methods"  
    My comment

2003    43<131      Free Article   
The induction of long-term potentiation at amygdalo-hippocampal synapses in vivo.   
    "Electrical stimulation of the basolateral amygdala (BLA) evoked synaptic potentials in the dentate gyrus (DG) of the hippocampus in anesthetized rats." 
    "Application of two trains of 100-pulse, 100-Hz stimulation or theta-burst stimulation to the BLA reproducibly induced long-term potentiation (LTP) of BLA-DG synaptic potentials."  
    My comment

2004    38<131     Free PMC Article   
Amygdala stimulation modulates hippocampal synaptic plasticity.   
    "Experience-dependent synaptic plasticity is a fundamental feature of neural networks involved in the encoding of information, and the capability of synapses to express plasticity is itself activity-dependent."  
    "The range of this plastic modulation was also modified by past activity of the basolateral amygdala, suggesting that the amygdala can arrange its ability to regulate the dentate plastic responses. The effects of the BLA activation were replicated by stimulation of the lateral perforant path and, hence, BLA stimulation may recruit the lateral entorhinal cortex."  
    My comment

2006    23<131     Free Article   
Ventral hippocampal neurons project axons simultaneously to the medial prefrontal cortex and amygdala in the rat.   
    "Our anatomical and electrophysiological evidence for the presence of VH neurons projecting to both the mPFC and amygdala provides a previously unrecognized pathway from the hippocampus that simultaneously activates the mPFC and amygdala."  
    My comment

2006    312<354 
Task and content modulate amygdala-hippocampal connectivity in emotional retrieval.   
We show that retrieval of emotionally valenced contextual information is associated with enhanced connectivity from hippocampus to amygdala"   Free Article   
    My comment

2008    16<131 
Neonatal isolation stress alters bidirectional long-term synaptic plasticity in amygdalo-hippocampal synapses in freely behaving adult rats.   
    "The basolateral amygdala (BLA) is known to be involved in emotional and stress responses, while the dentate gyrus (DG), a subfield of the hippocampus, is implicated in learning and memory. "  
    "These results indicate that neonatal isolation stress alters bidirectional neural plasticity in BLA-DG synapses, which may help to clarify the development of neural mechanisms linking emotional and stress responses in the amygdala with memory consolidation and information processing in the hippocampus."  
    My comment
neonatal stress > BLA+HIP

Connectivity-based segregation of the human striatum predicts personality characteristics   
We found that personality characteristics are linked to dissociable connectivity streams in the human brain. Whereas fiber tracts between a subcortical network, including the hippocampus and amygdala, and the ventral striatum predicted individual differences in novelty seeking, tracts between prefrontal cortex and the striatum predicted individual differences in reward dependence. These findings suggest that the strength of limbic-striatal connectivity may, in part, underlie human personality traits."  

2011    8<131     Free PMC Article   
Heterogeneous processing of amygdala and hippocampal inputs in the rostral and caudal subregions of the nucleus accumbens.      

    "The nucleus accumbens (NAc) receives converging input from a number of structures proposed to play a role in affective disorders. In particular, the basolateral amygdala (BLA) provides an affective input that overlaps with context-related information derived from the ventral subiculum of the hippocampus (vSub). We examined how stimulation of the BLA is modulated by, and in turn affects, vSub inputs to this region. In-vivo extracellular recordings were performed in the NAc of anaesthetized rats. The effect of high-frequency (theta-burst) stimulation (HFS) of the BLA on both BLA and vSub-evoked responses was tested. In addition, the involvement of dopamine D2 receptors in BLA-induced plasticity in the NAc was examined by pre-treatment with sulpiride (5 mg/kg i.v.). Finally, tetrodotoxin (TTX) was used to inactivate the vSub and the effect on BLA-evoked responses was assessed.  
    We found that HFS of the BLA causes hetereogeneous patterns of plasticity, depression and potentiation, respectively, in the rostral and caudal subregions of the NAc that are disrupted following D2 receptor antagonist treatment. In addition, inactivating the vSub with TTX attenuates the ability of the BLA to drive spike firing in the NAc. Thus, the vSub is required for activation of the NAc by the BLA. These data support a model whereby the amygdala can coordinate reward-seeking and fear-related behaviours via its differential regulation of NAc output. In addition, the hippocampus inappropriately dominates information processing within this circuit, potentially contributing to the overwhelming focus on internal emotional states in disorders such as depression."  
    My comment

2013    5<131     Free PMC Article   
Differential effects of acute and repeated stress on hippocampus and amygdala inputs to the nucleus accumbens shell.   
    "The basolateral amygdala (BLA) and ventral subiculum (vSub) of the hippocampus convey emotion and context information, respectively, to the nucleus accumbens (NAc)."  
    "This work provides new insight into the impact of acute and repeated stress on the integration of context and emotion inputs in the NAc. These data support a model of stress whereby the hippocampus is inappropriately activated and dominates the information processing within this circuit via a dopaminergic mechanism after acute bouts of stress."  

    My comment

2014    3<131     Free PMC Article   
Amygdala inputs to the ventral hippocampus bidirectionally modulate social behavior.   
    "These results indicate that BLA inputs to the vHPC are capable of modulating social behaviors in a bidirectional manner."  
     My comment

2014    113<354 
Dynamic modulation of amygdala-hippocampal connectivity by emotional arousal.   
These findings indicate that, during encoding, emotionally arousing information leads to a robust increase in effective connectivity from the amygdala to the hippocampus, regardless of its valence. "  
    My comment

2015    2<43    Free PMC Article 
Complementary Patterns of Direct Amygdala and Hippocampal Projections to the Macaque Prefrontal Cortex.   
    " Almost all prefrontal areas were found to receive some amygdala inputs. ... The hippocampal projections to prefrontal areas were far more restricted"  
    " Only in medial prefrontal cortex do direct inputs from both structures terminate in common sites. But, even when convergence occurs within an area, the projections predominantly terminate in different lamina (hippocampal inputs to layer III and amygdala inputs to layers I, II, and VI)."  
    My comment

2015    100<354 
Temporal dynamics of stress-induced alternations of intrinsic amygdala connectivity and neuroendocrine levels.
Free PMC Article  
Acute stress responding and recovery are thus associated with changes in the functional connectivity of the amygdala network. Our findings show that these changes may be regulated via stress-induced neuroendocrine levels."  
    My comment

Convergence and Interaction of Hippocampal and Amygdalar Projections within the Prefrontal Cortex in the Rat | Journal of Neuroscience 

McDonald AJ (1996) Glutamate and aspartate immunoreactive neuron of the rat basolateral amygdala: colocalization of excitatory amino acids and projections to the limbic circuit.    
    J Comp Neurol 365: 367-379.    

CrossRef    PubMed   Google Scholar   

   Is there any relationship between   Amygdaloid-Hippocampal Convergence  and  Parazoa Hormones 

    GABA and glutamate specifically induce contractions in the sponge Tethya wilhelma.  in
   Parazoa Hormones  

     If I remember correctly, both the Amygdala  and the Hippocampus  use Glutamate  to project to
Nucleus Accumbens Septi which in turn uses   GABA  as its projection neurotransmitter.    

2003    Convergence and Interaction of Hippocampal and Amygdalar Projections within the Prefrontal Cortex in the Rat 

McDonald AJ (1996) Glutamate and aspartate immunoreactive neuron of the rat basolateral amygdala: colocalization of excitatory amino acids and projections to the limbic circuit.    
    J Comp Neurol 365: 367-379.    

CrossRef    PubMed   Google Scholar   

171213 - 2150