Difference between revisions of "Previous weeks"

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== Previous Semesters ==
 
== Previous Semesters ==
 
+
<h3>[[Spring 2010]]</h3>
 
<h3>[[Fall 2009]]</h3>
 
<h3>[[Fall 2009]]</h3>

Revision as of 17:15, 11 August 2010

Contents

Spring 2010:

January


Jan 15th

Speaker : John Guzowski of UC Irvine.

"Immediate-Early Gene Expression in Hippocampus: A Window into the Cellular Mechanisms & Neural Circuit Dynamics of Memory"

Summary of Talk:

The ability of neurons to change gene expression patterns in response to synaptic input is critical for cellular mechanisms underlying learning and memory. Following behavioral experience, expression of specific "immediate-early genes (IEGs)" is dramatically increased in discrete populations of neurons in hippocampus, neocortex, and subcortical brain regions. IEGs such as /Arc/ and /Homer 1a/ encode proteins capable of modifying synaptic function and are required for converting experience into lasting memory (i.e., memory consolidation). I will discuss past and ongoing research using sophisticated IEG imaging methods to study neural ensemble dynamics during learning and memory retrieval. In combining these imaging approaches with lesion, neuropharmacological, and vector-mediated gene knockdown/mutation methods, we are address long-standing and fundamental questions about the role of the hippocampus and associated neocortical regions in memory encoding, consolidation, and retrieval.


Jan 29th

Speaker : Dean Buonomano

"What is the Neural Basis of Priming "

Papers Covered:

Grill-Spector K, Henson R, Martin A (2006) Repetition and the brain: neural models of stimulus-specific effects. Trends in Cognitive Sciences 10:14-23.

Li L, Miller EK, Desimone R (1993) The representation of stimulus familiarity in anterior inferior temporal cortex. J Neurophysiol 69:1918-1929.

McMahon DBT, Olson CR (2007) Repetition Suppression in Monkey Inferotemporal Cortex: Relation to Behavioral Priming. J Neurophysiol 97:3532-3543.


February


Feb 05th

Speaker: Thomas W. Abrams, from Dept of Pharmacology, University of Maryland School of Medicine, Baltimore, MD.

"Molecular Mechanisms of Sensory Gating in Aplysia as a Model of Attention"

Summary of the Talk:

Sensory gating enables nervous systems to select which environmental stimuli receive attention. The sensory neuron-to-motor neuron synapse in the defensive withdrawal reflexes of the marine snail /Aplysia/ undergoes rapid and dramatic synaptic depression with low frequency activity. Although this phenomenon has been known for four decades, the underlying molecular mechanism has remained obscure. Our recent analysis suggests that synaptic depression in this system mediates a form of synaptic gating related to stimulus salience, rather than mediating a type of learning, habituation, based on familiarity with a stimulus. In my talk, I will discuss two opposing, calcium-dependent processes that flip these synapses between bistable states during sensory gating. The molecular elements in this switch include protein kinase C and the small G protein Arf. The ubiquitous presence of these highly conserved proteins among metazoans suggest that a similar sensory gating mechanism may operate in mammalian sensory systems, where it could contribute to attention.



Feb 19th

Speaker: Tom O'Dell

"The Death of the Subunit-Specific Rules Hypothesis of AMPA Receptor Trafficking?"

Summary of the Talk:

For many years the prevailing view regarding the mechanisms of AMPA receptor trafficking at excitatory synapses has held that the subunit composition of AMPA receptors has a crucial role. Via mechanisms dependent on the intracellular c-termini of the subunits, GluR2/GluR3 subunit containing receptors were thought to form a stable, continuously recycling pool of AMPA receptors at the synapse while GluR1/GluR2 subunit containing receptors were only trafficking into synapses in an activity-dependent manner. Once inserted into synapses, GluR1/GluR2 containing receptors were then thought to be gradually replaced by GluR2/GluR3 containing receptors. Along with other studies, recent work from the Nicoll laboratory using a single-cell “knockout” approach shows that there is very little role for GluR2/GluR3 containing receptors. Instead, 80% of all synaptic receptors (and 95% of all extrasynaptic receptors) are GluR1/GluR2 heteromers.

Relevant Papers:

Paper_1


Feb 26th

Speaker: Shlomo Dellal

"Heterogeneity in presynaptic bouton sensitivity to neuromodulators in parallel fibers of the cerebellar cortex."

Summary of the Talk:

In his presentation last Friday, Tom O’Dell brought up the possibility that there is heterogeneity in AMPAR subunit expression in different synapses in the same hippocampal pyramidal neuron. This may not be all that surprising for synapses formed by different presynaptic neuronal types and/or synapses in different regions of the neuron. The paper I’m presenting this week takes this a step further and shows that even neighboring synapses from the same neuron onto the same neuronal type, can exhibit significant heterogeneity. In this paper, the authors use calcium imaging to look at calcium transients in presynaptic boutons on cerebellar parallel fibers, which make excitatory synapses onto the sole output neuron for the cerebellum, the Purkinje cell. As with Schaffer collateral fibers and CA1 pyramidal cells in the hippocampus, these synapses are en passant. The authors look at the effects of activating various neuromodulator receptors on the presynaptic terminals, on stimulus-evoked calcium transients. They find that the sensitivity of neighboring boutons on the same axon to these drugs correlated with either the size of the bouton or the amplitude of the basal calcium transient. While the implications for cerebellar plasticity are unclear, these findings demonstrate that even neighboring synapses from the same neuron, possibly onto the same neuron, can exhibit remarkable differences in their molecular makeup that may influence their ability to undergo plasticity.

Relevant Papers:

1. Paper_1

2. Supplemental Information


March


Mar 05th


Speaker : Kelsey Martin

"Stable structural changes in cortical dendritic spines accompanies learning and memory."

Summary of the talk:

Not Provided

Relevant Papers:

1. Paper_1

2. Paper_2



Mar 12th

Speaker : Justin Shobe

Not all neurons are connected equally; a look at Hub neurons in the hippocampus

Summary of the talk:

In an exciting study in the December 4th issue of Science, Bonifazi and colleagues demonstrated the existence and importance of exceedingly rare but unusually richly connected cells in the developing hippocampus.Manipulating the activity of single GABAergic hub cells modulated network activity patterns, demonstrating their importance for coordinating synchronous activity. (Taken from preview by Case & Soltesz).

Relevant Papers:

1. Paper_1

2. Paper_2

3. Paper_3


Mar 19th

Speaker : Franklin B. Krasne

"Designing Fraidy Rat, a neurally plausible fear-learning automation"

Summary of the talk

Fraidy Rat is a computer program that incorporates a simulation of amygdala-centered fear learning and provides virtual tools (for behavioral analysis, stereotaxic surgery, single unit extracellular recording, electrical stimulation, targeted and systemic drug infusions) which students can use to try to discover how the automaton works, much in the same way as does a neuroscientist trying to understand real fear learning.The simulation at the center of the program is also intended as a model of fear-conditioning that I believe can contribute to the understanding of fear learning mechanisms. Both the program and the model will be discussed



April


Apr 02nd

Speaker: Peyman Golshani

Human memory strength is predicted by theta-frequency phase-locking of single neurons

Summary of the talk :

Little is known about how neuronal populations encode memories in the human medial temporal lobe. In this exciting paper Erin Schuman and colleagues perform simultaneous local field potential and single unit recordings in the hippocampus and amygdala of humans while they encode and retrieve visual memories. They show that they can predict which memories are successfuly encoded by determining how tightly spikes are coordinated to theta oscillations of the field potential. Spike timing accuracy was more critical than the absolute firing rate or the power of theta oscillations. These experiments highlight the importance of spike-timing plasticity mechanisms in memory formation.


Apr 09th

Speaker: Paul Mathews

Feed-forward inhibition keeps the eye on the prize

Summary of the talk :

Circuits in which interneurons and their target cells receive common excitatory inputs have been described in multiple brain regions. In the hippocampus plasticity at synapses of these so called feed-forward circuits have been shown to be important in both the precision of timing and the fidelity of information processing. In this weeks paper by Wulff et al. the authors argue that molecular layer interneurons which synapse onto Purkinje cells and receive common excitatory input in the cerebellum play an essential role in regulating signal coding and the consolidation of vestibulo-ocular motor learning.

Relevant Paper:

Paper

Supplement



Apr 16th

Aplysia CPEB Can Form Prion-like Multimers in Sensory Neurons that Contribute to Long-Term Facilitation


Speaker: David Glanzman

Summary of the talk:

Not Provided

Relevant Paper: Paper



Apr 23rd

Enhancement of learning and memory by elevating brain magnesium


Speaker: Felix Schewizer


Summary of the talk :

Not Provided


Relevant paper:

Paper



Apr 30th

Using reconsolidation as a tool to tell us what the lateral amygdala encodes during fear conditioning?

Speaker: Micheal Fanselow


Summary of the talk  :

A traditional way of inducing reconsolidation of associative fear memory is to present the conditioning stimulus (CS), which reactivates the memory trace. The current study shows that an unconditioned stimulus (US)—often stronger in perceptual intensity than CS—on its own can trigger memory reconsolidation that is specific for the sensory properties of the US.


Relevant Paper:

Paper



May


May 07th

Nature of NMDAR-dependent plasticity induced by natural spike patterns

Speaker : Mayank Mehta

Summary of the talk:

Hippocampal NMDAR-dependent plasticity is thought to mediate spatial learning. The direction and magnitude of NMDAR-dependent plasticity is influenced by spike-rate and spike-timing; both vary simultaneously within hippocampal place field. I will discuss experimental and theoretical work to estimate the nature of NMDAR-dependent plasticity induced by natural spike patterns.

Relevant Paper: None


May 14th

CKAMP44: A brain-specific protein attenuating short-term synaptic plasticity in the dentate gyrus.

Speaker : Walter Babiec

Summary of the talk:

Engelhardt et al. report the discovery of cystine-knot AMPA receptor modulating proteins (CKAMPs), a new family of brain-specific transmembrane proteins that associate with AMPA receptors in synaptic spines. Like TARPs, they affect AMPA receptor kinetics. Specifically, CKAMPs enhance desensitization, which the authors show has effects on paired-pulse facilitation and thus short-term plasticity in the increasingly crowded excitatory synapse.


Relevant Paper:

Paper

Commentary

Supp


May 21st

Rapid spine stabilization and synaptic enhancement at the onset of behavioural learning.


Speaker : Michael Condro


Summary of the Talk: This paper uses two-photon imaging to monitor spine turnover in a zebra finch song control nucleus before and after exposure to a song tutor. In this system changes spine dynamics may contribute to the closure of critical periods for song learning.


Relevant Paper :

Paper


June


Jun 11th

Emotional arousal and its effects on AMPA receptor composition

Speaker : Paul Mathews

Summary of the Talk: Emotional arousal has been shown to enhance some forms of learning and memory. The mechanisms behind this enhancement have been proposed to result from the release of noradrenaline from the locus coeruleus and the subsequent activation of β-adrenergic receptors in neurons throughout the CNS. Previous studies have illustrated the capability of noradrenaline to alter synaptic transmission in multiple areas of the brain including synapses within the cerebellum. The paper for this week attempts to answer the question, do emotional experiences regulate synaptic transmission by modulating post synaptic ligand gated ion channels. Specifically, they attempt to show that noradrenaline’s release by a single fear-inducing stimulus induces a transcription-dependent switch in synaptic AMPAR phenotype from GluR2 lacking to GluR2 containing.

Relevant Paper:

Paper

Supplement


Jun 18th

The Role of Astrocytes in LTP Induction

Speaker : Tom O'Dell

Summary of the Talk:

Although glial cells have long been thought to primarily provide structural and metabolic support to neurons, recent findings from a number of labs suggest that astrocytes may play a much more active role in synaptic transmission. For example, astrocytes can release a number of different transmitters that directly affect synaptic function and neuronal excitability. While this suggests that "gliotransmitters" may also have a role in synaptic plasticity, the involvement of astrocytes in LTP induction at excitatory synapses in the hippocampus has become very controversial. In journal club I'll discuss a recent publication from the Rusakov lab showing that gliotransmission has an essential role in the induction of LTP and a paper from Ken McCarthy's lab showing that astrocytes have no role in LTP induction.


Relevant Paper :

Paper 1

Paper 2




Jun 25th

Cortical methylation maintains remote memory

Speaker: Justin Shobe

Summary of the talk:

Relevant Paper :

Paper 1



Jul 09th

Activity-dependent nuclear translocation from synapse to nucleus of the Transducer of Regulated CREB 1(TORC1)/CREB Regulated Transcriptional Co-activator 1 (CRTC1)

Speaker : Kelsey Martin

Summary of the talk :

Relevant Paper :

[Work from her lab]



Jul 30th

Metaplasticity at Single Synapses

Speaker: Adam Frank

Summary of the talk: Neuronal activity is known to modify NMDA receptor subunit composition; and, NMDAR subunit composition has significant effects on NMDAR synaptic currents. Given the importance of the NMDAR in the induction of LTP it is not surprising that altering NMDAR currents, by altering subunit composition, has demonstrated effects on the induction of LTP. Lee et al. now demonstrate these phenomena at the level of single synapses in cultured hippocampal neurons: altering spontaneous activity changes the ratio of NR2B to NR2A subunits and effects both NMDAR synaptic current as well as LTP induction threshold. These findings are presented in the context of metaplasticity, where prior activity at a synapse effects the subsequent ability of the synapse to undergo plasticity.

Relevant Paper :

Paper 1

Supplementary Info

Previous Semesters

Spring 2010

Fall 2009