Leibniz Institute for Neurobiology

Magdeburg, Germany

Leibniz Institute for Neurobiology

Magdeburg, Germany
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News Article | May 3, 2017
Site: phys.org

No two cakes smell identical, yet we are still able to recognise the general aroma that promises pleasure. Ayse Yarali from the Leibniz Institute for Neurobiology, Germany, explains that this ability to generalise a previously learned link between a cue - such as an odour - and an experience - such as a pleasant taste or the attack of a predator - to a range of similar cues can help us to ensure that we repeatedly encounter pleasant situations while avoiding risky ones. As the ability to generalise what is learned about a scent to a wide range of similar scents is an essential life skill for many species - including fruit flies - Yarali wondered whether the humble insect's ability to generalise changes over time. Teaming up with Christian König, Yarali decided to investigate how flies that had learned to associate an electric shock with a specific fruity odour reacted later when they experienced other fruity scents. Together they have discovered that fruit flies, which generalise memories across similar scents, do so more strongly after a period of time in much the same way as PTSD sufferers over generalise memories, and they publish their study in Journal of Experimental Biology. König and his colleagues Emmanuel Antwi-Adjei and Mathangi Ganesan identified three odours (3-octanol, n-amylacetate and 1-octen-3-ol) that could be distinguished by the fruit flies and used a Teflon tube lined with a pair of tightly wrapped copper coils attached to a power supply to shock the insects. 'If a fly happens to touch both of the coils with its legs - six legs give many possibilities - it gets an electric shock', explains Yarali. König then wafted one of the odours through the tube while the flies received a series of shocks in the hope that they would learn to avoid the odour in future. Twenty minutes later, König tested the insects' responses to the odour by placing them in a T-shaped maze where one arm was scented. Sure enough, the majority of flies avoided that region of the maze; they also recalled the memory 24 h later. But would the flies generalise the shocking experience and recall it when they encountered a similar, but different, odour? König replaced the odour in the T-maze with a new scent and, although some of the shocked flies avoided the novel scent 20 min later, it was a different matter after 24 h. This time, the flies' aversion to the new odour was as strong as their desire to avoid the odour that was directly associated with the shock. They had generalised their memory of the shock so that they recalled the memory even when the scent that they encountered was only vaguely familiar. So, flies can generalise a troubling memory across odours that smell similar. However, Yarali explains that even though the ability to generalise a memory can be beneficial, it can also become an impediment if it is exaggerated. 'Overly generalised memories of a traumatic experience in humans are one of the key behavioural hallmarks of post-traumatic stress disorder [PTSD]', explains Yarali; and the effects of human PTSD are often delayed, in much the same way that flies did not develop their general aversion to similar odours until several hours later. 'We cannot say that we have a fully fledged fly model of human PTSD', says Yarali, as the flies are unlikely to be suffering the same horrifying experiences that victims of PTSD endure, but they do appear to have at least one of the behavioural hallmarks of the human condition. And she is eager to discover whether the shocked flies exhibit some of the other behaviours that are indicative of a 'disturbed state of mind' with the hope that this research may one day help us to develop new therapeutic strategies for human sufferers of PTSD. Explore further: The precision of associative memories More information: König, C., Antwi-Adjei, E., Ganesan, M., Kilonzo, K., Viswanathan, V., Durairaja, A., Voigt, A. and Yarali, A. (2017). Aversive olfactory associative memory loses odor specificity over time. J. Exp. Biol. 220, 1548-1553., DOI: 10.1242/jeb.155317

Aggelopoulos N.C.,Leibniz Institute for Neurobiology
Neuroscience and Biobehavioral Reviews | Year: 2015

Perceptual inference refers to the ability to infer sensory stimuli from predictions that result from internal neural representations built through prior experience. Methods of Bayesian statistical inference and decision theory model cognition adequately by using error sensing either in guiding action or in "generative" models that predict the sensory information. In this framework, perception can be seen as a process qualitatively distinct from sensation, a process of information evaluation using previously acquired and stored representations (memories) that is guided by sensory feedback. The stored representations can be utilised as internal models of sensory stimuli enabling long term associations, for example in operant conditioning. Evidence for perceptual inference is contributed by such phenomena as the cortical co-localisation of object perception with object memory, the response invariance in the responses of some neurons to variations in the stimulus, as well as from situations in which perception can be dissociated from sensation. In the context of perceptual inference, sensory areas of the cerebral cortex that have been facilitated by a priming signal may be regarded as comparators in a closed feedback loop, similar to the better known motor reflexes in the sensorimotor system. The adult cerebral cortex can be regarded as similar to a servomechanism, in using sensory feedback to correct internal models, producing predictions of the outside world on the basis of past experience. © 2015 Elsevier Ltd.

The hippocampal long-term potentiation (LTP) at Schaffer collateral synapses onto CA1 pyramidal neurons has been widely studied as a cellular model of activity-dependent enhancement of synaptic transmission. The apical (stratum radiatum) and basal dendrites (stratum oriens) of hippocampal CA1 pyramidal neurons differ in LTP induction and maintenance. Here, the role of mGlu receptors in the induction and maintenance of late-LTP was investigated, in comparison of these two compartments. My results show that mGlu1 receptor modulates late-LTP in apical dendrites and basal dendrites, whereas mGlu5 receptor modulates late-LTP only in apical dendrites. © 2013 Elsevier Ireland Ltd.

Moncada D.,Leibniz Institute for Neurobiology
Neurobiology of Learning and Memory | Year: 2017

Several works have shown that the formation of different long-term memories relies on a behavioral tagging process. In other words, to establish a lasting memory, at least two parallel processes must occur: the setting of a learning tag (triggered during learning) that defines where a memory could be stored, and the synthesis of proteins, that once captured at tagged sites will effectively allow the consolidation process to occur. This work focused in studying which brain structures are responsible of controlling the synthesis of those proteins at the brain areas where memory is being stored. It combines electrical activation of the ventral tegmental area (VTA) and/or the locus coeruleus (LC), with local pharmacological interventions and weak and strong behavioral trainings in the inhibitory avoidance and spatial object recognition tasks in rats. The results presented here strongly support the idea that the VTA is a brain structure responsible for regulating the consolidation of memories acting through the D1/D5 dopaminergic receptors of the hippocampus to control the synthesis of new proteins required for this process. Moreover, they provide evidence that the LC may be a second structure with a similar role, acting independently and complementary to the VTA, through the β-adrenergic receptors of the hippocampus. © 2016 Elsevier Inc.

Quiroga R.Q.,University of Leicester | Quiroga R.Q.,Leibniz Institute for Neurobiology
Nature Reviews Neuroscience | Year: 2012

Intracranial recordings in subjects suffering from intractable epilepsy-made during their evaluation for an eventual surgical removal of the epileptic focus-have allowed the extraordinary opportunity to study the firing of multiple single neurons in awake and behaving human subjects. These studies have shown that neurons in the human medial temporal lobe respond in a remarkably selective and abstract manner to particular persons or objects, such as Jennifer Aniston, Luke Skywalker or the Tower of Pisa. These neurons have been named 'Jennifer Aniston neurons' or, more recently, 'concept cells'. I argue that the sparse, explicit and abstract representation of these neurons is crucial for memory functions, such as the creation of associations and the transition between related concepts that leads to episodic memories and the flow of consciousness. © 2012 Macmillan Publishers Limited. All rights reserved.

Angenstein F.,Leibniz Institute for Neurobiology
Journal of Neuroscience | Year: 2014

Paired-pulse stimulation of the perforant pathway was used to study the relation between granular cell activity and the resultant fMRI response in the rat dentate gyrus. By varying the interpulse interval (IPI), paired-pulse stimulations caused: A depression (20 ms IPI), a facilitation (100 ms IPI), a mixture of depression and facilitation (30 ms IPI), or no change (500 ms IPS) in the second response. Eight identical paired pulses were applied during one stimulation train and the evoked field potentials and generated fMRI responses were measured simultaneously. Application of consecutive stimulation trains caused time-dependent variations in electrophysiological and fMRI responses, which were characteristic for each stimulus protocol. Depending on the IPI, the magnitude of the fMRI response either correlated strongly with or was apparently unrelated to the spiking or postsynaptic activity of the granular cells.Astrong relation between spiking activity and resultant fMRI response was only found when the stimulation protocol caused an increase in the recorded population spike latency. If the latency was decreased, the fMRI response was more closely related to the applied input activity. Perforant pathway fibers monosynaptically activate granular cells, so variations in population spike latencies reflect changes in their intrinsic excitability. Therefore, during increased intrinsic excitability, signaling cascades upstream of the granular cells determine the fMRI response, whereas granular cell activity-related mechanisms control the fMRI response during decreased intrinsic excitability. © 2014 the authors.

Dieterich D.C.,Leibniz Institute for Neurobiology
Current Opinion in Neurobiology | Year: 2010

Fluorescent proteins have revolutionized cell biology and, therefore, our understanding of the complex molecular and cellular mechanisms that wire the brain together and enable its plasticity throughout life. The ability to visualize cell biological processes has inspired the development of alternative protein labeling strategies by both chemists and biologists. Among those approaches are the introduction of small bioorthogonal chemical reporters and new fluorescent probes by either genetic encoding or by utilizing the cell's own biosynthesis machinery in live cells. This review will highlight recent advances in approaches to track discrete proteins or whole subpopulations of a proteome including post-translational modifications with spatiotemporal resolution. © 2010 Elsevier Ltd.

Angenstein N.,Leibniz Institute for Neurobiology | Brechmann A.,Leibniz Institute for Neurobiology
NeuroImage | Year: 2013

Intensity and duration are important parameters for the processing of speech and music. Neuroimaging results on the processing of these parameters in tasks involving the discrimination of stimuli based on these parameters are controversial. Depending on the experimental approach, varying hypotheses on the involvement of the left and right auditory cortices (ACs) have been put forward. The aim of the present functional magnetic resonance imaging (fMRI) study was to find differences and commonalities in location and strength of brain activity during the processing of intensity and duration when the same stimuli have to be actively categorized according to these two parameters. For this we used a recently introduced method to determine lateralized processing in the AC with contralateral noise. Harmonic frequency modulated (FM) tone complexes were presented monaurally without and with contralateral noise. During categorization of the tones according to their intensity, contralateral noise increased activity mainly in the left AC, suggesting a special role for the left AC in this task. During categorization of tones according to their duration, contralateral noise increased activity in both the left and the right AC. This suggests that active categorization of FM tones according to their duration does not involve only the left AC as has been suggested, but also the right AC to a substantial degree. The area around Heschl's sulcus seems to be the most strongly involved during both intensity and duration categorization, albeit with different lateralization. Altogether the results of the present study support the view that the lateralized processing of the same stimuli in the human AC is strongly modulated by the given task (top-down effect). © 2013 Elsevier Inc.

Panayotis N.,Weizmann Institute of Science | Karpova A.,Leibniz Institute for Neurobiology | Kreutz M.R.,Leibniz Institute for Neurobiology | Fainzilber M.,Weizmann Institute of Science
Trends in Neurosciences | Year: 2015

Local signaling events at synapses or axon terminals must be communicated to the nucleus to elicit transcriptional responses. The lengths of neuronal processes pose a significant challenge for such intracellular communication. This challenge is met by mechanisms ranging from rapid signals encoded in calcium waves to slower macromolecular signaling complexes carried by molecular motors. Here we summarize recent findings on macromolecular signaling from the synapse to the nucleus, in comparison to those employed in injury signaling along axons. A number of common themes emerge, including combinatorial signal encoding by post-translational mechanisms such as differential phosphorylation and proteolysis, and conserved roles for importins in coordinating signaling complexes. Neurons may integrate ionic flux with motor-transported signals as a temporal code for synaptic plasticity signaling. © 2014 Elsevier Ltd.

Ohl F.W.,Leibniz Institute for Neurobiology
Current Opinion in Neurobiology | Year: 2014

Rhythmic activity appears in the auditory cortex in both microscopic and macroscopic observables and is modulated by both bottom-up and top-down processes. How this activity serves both types of processes is largely unknown. Here we review studies that have recently improved our understanding of potential functional roles of large-scale global dynamic activity patterns in auditory cortex. The experimental paradigm of auditory category learning allowed critical testing of the hypothesis that global auditory cortical activity states are associated with endogenous cognitive states mediating the meaning associated with an acoustic stimulus rather than with activity states that merely represent the stimulus for further processing. © 2014.

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