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D Yaniv

Publications and source records attributed to D Yaniv.

7 recordsLinked to original sources
PubMed2003

Simultaneous induction of long-term potentiation in the hippocampus and the amygdala by entorhinal cortex activation: mechanistic and temporal profiles.

The medial temporal lobe, including the entorhinal cortex, the amygdala and the hippocampus, has an important role in learning and memory, and its circuits exhibit synaptic plasticity (long-term potentiation [LTP]). The entorhinal cortex is positioned to exert a potent influence on the amygdala and the hippocampus given its extensive monosynaptic projections to both areas. We therefore studied the effects of activation of the entorhinal cortex with simultaneous recording of LTP in the hippocampus and amygdala in the anesthetized rat. theta Burst stimulation of the lateral entorhinal cortex induced LTP simultaneously in the basal amygdaloid nucleus and in the dentate gyrus. However, the mechanisms involved in the induction of LTP in the two areas differed. The N-methyl-D-aspartate receptor antagonist 3-[(+/-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid delivered 1 h before LTP induction (10 mg/kg, i.p.), blocked LTP in the dentate gyrus but not in the amygdala. In addition we found that the basal amygdala as well as the dentate gyrus sustained late-phase LTP (10 h) which may participate in memory encoding and/or modulation processes. Overall, the results suggest a coordinating role for the entorhinal cortex by simultaneously modulating activity and plasticity in these structures, albeit through different mechanisms. Interactive encoding of this sort is believed to endow memories with a different, more integrative, quality than when either pathway is activated alone.

Amygdala↗
PubMed2001

A gradient of plasticity in the amygdala revealed by cortical and subcortical stimulation, in vivo.

Projections to the amygdala from various cortical and subcortical areas terminate in different nuclei. In the present study we examined long-term potentiation of synaptic transmission in the lateral or the basal amygdaloid nuclei by theta burst stimulation of thalamic vs. cortical sensory projections in the anesthetized rat. Although both the medial geniculate nucleus and the dorsal perirhinal cortex have direct projections to lateral nucleus, only the thalamic stimulation induced long-term potentiation of field potentials recorded in the lateral nucleus. In contrast, cortical (ventral perirhinal cortex) but not thalamic stimulation induced long-term potentiation in the basal nucleus. Since the thalamic pathway is believed to process simple/unimodal stimulus features, and the perirhinal cortex complex/polymodal sensory representations, the dissociation of long-term potentiation in lateral and basal nuclei suggests that the basal nucleus may serve as an amygdaloid sensory interface for complex stimulus information similar to the role of the lateral nucleus in relation to relatively simple representations. Thus plasticity of simple and complex representations may involve different amygdala inputs and circuits.

Amygdala↗
PubMed2001

Is LTP in the hippocampus a useful model for learning-related alterations in gene expression?

It is well established that the formation of long-term memory requires de novo protein synthesis. Altered gene expression is therefore critical in the signal transduction cascade activated by the learning experience. Long-term potentiation (LTP) is a mnemonic model in which particular patterns of activation of incoming excitatory fibers (representing the learning experience) may induce long-lasting enhancement of the communication between the involved pre- and post-synapses (representing the memory). Therefore, cellular and molecular mechanisms of LTP have been extensively studied under the assumption that their understanding will contribute to our comprehension of the mechanisms underlying memory formation. In recent years, however, this analogy has been challenged by reports of inconsistency between LTP and memory. Here we assess LTP in the hippocampus as a model system to study spatial memory-related alterations in gene expression. We focus on three molecular families that are likely to play a role in synaptic plasticity: (1) synaptic communication related proteins; (2) signal transduction machinery; and (3) growth factors. Reviewing first the literature on LTP and then behavioral research we found both consistent and inconsistent findings regarding the LTP/memory linkage. The importance of restricting the discussion to both a learning phase and a brain (sub)structure, as well as of incorporating more physiological LTP stimulation protocols, is discussed. We conclude that while LTP is indeed limited as a model of memory, a careful use of it as a model system of synaptic plasticity is fruitful and productive in screening out candidate memory-related genes.

Animals↗
PubMed2000

LTP in the rat basal amygdala induced by perirhinal cortex stimulation in vivo.

The present study examined the effects of ventral perirhinal cortex (vPRC) stimulation on evoked field potentials (EPs) in the basal amygdala (BN), using extracellular recording techniques. Single pulse stimulation of the vPRC reliably evoked a negative field potential in the BN that was missing in the lateral nucleus. Paired-pulses delivered to the vPRC induced a short-lasting facilitation at intervals between 15 and 120 ms. Application of brief theta burst stimulation to the vPRC produced an enduring long-term potentiation (LTP) that reached 150% of control values. The induction of LTP was not accompanied by a decrease in paired-pulse facilitation. These results suggest that emotional learning involving complex stimulus representations may be mediated by cortico-amygdalar projections amenable to LTP.

Amygdala↗
PubMed1998

Gamma probe-guided sentinel node biopsy--optimal timing for injection.

AIMS: We initiated a Phase I feasibility study using a gamma-detecting probe (GDP) and radiolabelled colloid to localize the sentinel lymph node (SLN) in breast cancer. The aim of the study was to establish the ideal timing for injection and examine any possible exclusion criteria for this method. METHODS: Thirty breast cancer patients diagnosed by fine needle aspiration (FNA) were included in this study. All were injected with 60 MBq rhenium colloid labelled with 99mTc (Tck-17). Scintigraphy was done 20 min, 2, 6 and 25 hours post-injection. Patients were then taken to surgery where they were injected with patent blue dye. During surgery, the SLN was located with a GDP (Neoprobe Model 1000). In 28 patients, the SLN was identified by scintigraphy 2 hours after injection, identical to the images seen after 24 hours. RESULTS: In all 28 patients, the SLN was found by the GDP during surgery. In 26 patients the SLN was dyed blue. The two patients with no SLN localization had received prior radiation. Pathology disclosed SLNs with metastases in seven patients. Two patients had a negative SLN but had an axillary lymph node replaced by tumour. CONCLUSIONS: Two to 24 hours prior to surgery is suitable timing for injection. Previous radiotherapy predicts failure for this procedure. Further studies are needed to find the exact false-negative rate of this method for breast cancer.

Adult↗