Training rodents in a particularly difficult olfactory-discrimination (OD) task results in the acquisition of the ability to perform the task well, termed 'rule learning'. In addition to enhanced intrinsic excitability and synaptic excitation in piriform cortex pyramidal neurons, rule learning results in increased synaptic inhibition across the whole cortical network to the point where it precisely maintains the balance between inhibition and excitation. The mechanism underlying such precise inhibitory enhancement remains to be explored.
View Article and Find Full Text PDFThe acquisition of complex rules requires modifications in intrinsic plasticity of excitatory neurons within relevant brain areas. Olfactory discrimination (OD) rule learning occludes slow calcium-dependent potassium current (sI ) in piriform cortex (PC) pyramidal neurons, which increases their intrinsic neuronal excitability. Similar learning-induced sI changes are demonstrated in hippocampal CA1.
View Article and Find Full Text PDFSocial interactions involve both approach and avoidance toward specific individuals. Currently, the brain regions subserving these behaviors are not fully recognized. The anterior hypothalamic nucleus (AHN) is a poorly defined brain area, and recent studies have yielded contradicting conclusions regarding its behavioral role.
View Article and Find Full Text PDFTransl Psychiatry
November 2022
Fear conditioning leads to long-term fear memory formation and is a model for studying fear-related psychopathological conditions such as phobias and post-traumatic stress disorder. Long-term fear memory formation is believed to involve alterations of synaptic efficacy mediated by changes in synaptic transmission and morphology in lateral amygdala (LA). Nck1 is a key neuronal adaptor protein involved in the regulation of the actin cytoskeleton and the neuronal processes believed to be involved in memory formation.
View Article and Find Full Text PDFTraining rats in a particularly difficult olfactory discrimination task initiates a period of accelerated learning, manifested as a dramatic increase in the rats' capacity to discriminate between pairs of odors once they have learned the discrimination task, implying that rule learning has taken place. At the cellular biophysical level, rule learning is maintained by reduction in the conductance of the slow current (sI) simultaneously in most piriform cortex layer II pyramidal neurons. Such sI reduction is expressed in attenuation of the post-burst afterhyperpolarization (AHP) potential and thus in enhanced repetitive action potential firing.
View Article and Find Full Text PDFThe piriform cortex (PCx) is essential for learning of odor information. The current view postulates that odor learning in the PCx is mainly due to plasticity in intracortical (IC) synapses, while odor information from the olfactory bulb carried via the lateral olfactory tract (LOT) is 'hardwired.' Here, we revisit this notion by studying location- and pathway-dependent plasticity rules.
View Article and Find Full Text PDFWe study the relations between different learning paradigms and enduring changes in excitatory synaptic transmission. Here we show that auditory fear conditioning (AFC), but not olfactory fear conditioning (OFC) training, led to enduring enhancement in AMPA-mediated miniature EPSCs (mEPSCs). Moreover, olfactory unpaired training led to a stable significant reduction in excitatory synaptic transmission.
View Article and Find Full Text PDFThe septo-hippocampal cholinergic system is critical for hippocampal learning and memory. However, a quantitative description of the firing patterns and physiological function of medial septal (MS) cholinergic neurons is still missing. In this study, we combined optogenetics with multichannel recording and recorded MS cholinergic neuron firings in freely behaving male mice for 5.
View Article and Find Full Text PDFLong-term memory of complex olfactory learning is expressed by wide spread enhancement in excitatory and inhibitory synaptic transmission onto piriform cortex pyramidal neurons. A particularly interesting modification in synaptic inhibition is the hyperpolarization of the reversal potential of the fast post synaptic inhibitory potential (fIPSP). Here we study the mechanism underlying the maintenance of such a shift in the fIPSP.
View Article and Find Full Text PDFIn this study we explored whether learning leads to enduring changes in inhibitory synaptic transmission in lateral amygdala (LA). We revealed that olfactory discrimination (OD) learning in rats led to a long-lasting increase in postsynaptic GABA channel-mediated miniature inhibitory postsynaptic currents (mIPSCs) in LA. Olfactory fear conditioning, but not auditory fear conditioning, also led to enduring enhancement in GABA-mediated mIPSCs.
View Article and Find Full Text PDFThe biological mechanisms underlying complex forms of learning requiring the understanding of rules based on previous experience are not yet known. Previous studies have raised the intriguing possibility that improvement in complex learning tasks requires the long-term modulation of intrinsic neuronal excitability, induced by reducing the conductance of the slow calcium-dependent potassium current (sI) simultaneously in most neurons in the relevant neuronal networks in several key brain areas. Such sI reduction is expressed in attenuation of the postburst afterhyperpolarization (AHP) potential, and thus in enhanced repetitive action potential firing.
View Article and Find Full Text PDFThe piriform cortex (PCx) receives direct input from the olfactory bulb (OB) and is the brain's main station for odor recognition and memory. The transformation of the odor code from OB to PCx is profound: mitral and tufted cells in olfactory glomeruli respond to individual odorant molecules, whereas pyramidal neurons (PNs) in the PCx responds to multiple, apparently random combinations of activated glomeruli. How these 'discontinuous' receptive fields are formed from OB inputs remains unknown.
View Article and Find Full Text PDFJ Neurophysiol
October 2018
The activity of a neural network is a result of synaptic signals that convey the communication between neurons and neuron-based intrinsic currents that determine the neuron's input-output transfer function. Ample studies have demonstrated that cell-based excitability, and in particular intrinsic excitability, is modulated by learning and that these modifications play a key role in learning-related behavioral changes. The field of cell-based plasticity is largely growing, and it entails numerous experimental findings that demonstrate a large diversity of currents that are affected by learning.
View Article and Find Full Text PDFFollowing training in a difficult olfactory-discrimination (OD) task rats acquire the capability to perform the task easily, with little effort. This new acquired skill, of 'learning how to learn' is termed 'rule learning'. At the single-cell level, rule learning is manifested in long-term enhancement of intrinsic neuronal excitability of piriform cortex (PC) pyramidal neurons, and in excitatory synaptic connections between these neurons to maintain cortical stability, such long-lasting increase in excitability must be accompanied by paralleled increase in inhibitory processes that would prevent hyper-excitable activation.
View Article and Find Full Text PDFTraining rats in a complex olfactory discrimination task results in acquisition of "rule learning" (learning how to learn), a term describing the capability to perform the task superbly. Such rule learning results in strengthening of both excitatory and inhibitory synaptic connections between neurons in the piriform cortex. Moreover, intrinsic excitability is also enhanced throughout the pyramidal neuron population.
View Article and Find Full Text PDFNeurobiol Learn Mem
October 2018
Training rats in a particularly difficult olfactory discrimination task initiates a period of accelerated learning of other odors, manifested as a dramatic increase in the rats' capacity to acquire memories for new odors once they have learned the first discrimination task, implying that rule learning has taken place. At the cellular level, pyramidal neurons in the piriform cortex, hippocampus and bsolateral amygdala of olfactory-discrimination trained rats show enhanced intrinsic neuronal excitability that lasts for several days after rule learning. Such enhanced intrinsic excitability is mediated by long-term reduction in the post-burst after-hyperpolarization (AHP) which is generated by repetitive spike firing, and is maintained by persistent activation of key second messenger systems.
View Article and Find Full Text PDFare key modulators that regulate central brain functions and behaviors, including learning and memory. At the cellular and molecular levels, endocannabinoids are potent modulators of excitatory and inhibitory synaptic function. Most effects of cannabinoids are thought to be mediated via G protein-coupled cannabinoid receptors.
View Article and Find Full Text PDFIntense spiking response of a memory-pattern is believed to play a crucial role both in normal learning and pathology, where it can create biased behavior. We recently proposed a novel model for memory amplification where the simultaneous two-fold increase of all excitatory (AMPAR-mediated) and inhibitory (GABAAR-mediated) synapses in a sub-group of cells that constitutes a memory-pattern selectively amplifies this memory. Here we confirm the cellular basis of this model by validating its major predictions in four sets of experiments, and demonstrate its induction via a whole-cell transduction mechanism.
View Article and Find Full Text PDFOnce trained, rats are able to execute particularly difficult olfactory discrimination tasks with exceptional accuracy. Such skill acquisition, termed "rule learning", is accompanied by a series of long-lasting modifications to three cellular properties which modulate pyramidal neuron activity in piriform cortex; intrinsic excitability, synaptic excitation, and synaptic inhibition. Here, we explore how these changes, which are seemingly contradictory at the single-cell level in terms of their effect on neuronal excitation, are manifested within the piriform cortical neuronal network to store the memory of the rule, while maintaining network stability.
View Article and Find Full Text PDFUnlabelled: Theta rhythmic clock-like activity was observed in a small group of hippocampal CA1 neurons in freely behaving mice. These neurons were only persistently activated during theta states of waking exploration and rapid eye movement sleep, but were almost silent during the non-theta state of slow-wave sleep. Interestingly, these cells displayed a theta clock-like simple-spike firing pattern, and were capable of firing one spike per theta cycle during theta states.
View Article and Find Full Text PDFLearning leads to changes in α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated synaptic excitation. The mechanisms for maintaining such alterations needed for memory persistence remain to be clarified. Here, we report a novel molecular mechanism for maintaining learning-induced AMPAR-mediated enhancement of synaptic excitation.
View Article and Find Full Text PDFTraining rats in a particularly difficult olfactory-discrimination task results in acquisition of high skill to perform the task superbly, termed "rule learning" or "learning set." Such complex learning results in enhanced intrinsic neuronal excitability of piriform cortex pyramidal neurons, and in their excitatory synaptic interconnections. These changes, while subserving memory maintenance, must be counterbalanced by modifications that prevent overspreading of activity and uncontrolled synaptic strengthening.
View Article and Find Full Text PDFRats that are trained in a particularly difficult olfactory discrimination task demonstrate a dramatic increase in their capability to acquire memories of new odors once they have learned the first discrimination task. Such high-skill learning, termed "rule learning" or "learning set" (see Saar et al., 1998, 2001) is accompanied by a series postsynaptic cellular modifications which have three major traits: a.
View Article and Find Full Text PDFComplex olfactory-discrimination (OD) learning results in a series of intrinsic and excitatory synaptic modifications in piriform cortex pyramidal neurons that enhance the circuit excitability. Such overexcitation must be balanced to prevent runway activity while maintaining the efficient ability to store memories. We showed previously that OD learning is accompanied by enhancement of the GABAA-mediated inhibition.
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