The Experts below are selected from a list of 6417 Experts worldwide ranked by ideXlab platform

Joseph E. Ledoux - One of the best experts on this subject based on the ideXlab platform.

  • The selectivity of aversive memory reconsolidation and extinction processes depends on the initial encoding of the Pavlovian association.
    Learning and Memory, 2013
    Co-Authors: Jacek Debiec, David E A Bush, Valerie Doyere, Lorenzo Diaz-mataix, Joseph E. Ledoux
    Abstract:

    In reconsolidation studies, memories are typically retrieved by an exposure to a single conditioned Stimulus (CS). We have previously demonstrated that reconsolidation processes are CS-selective, suggesting that memories retrieved by the CS exposure are discrete and reconsolidate separately. Here, using a compound Stimulus in which two distinct CSs are concomitantly paired with the same aversive Unconditioned Stimulus (US), we show in rats that reexposure to one of the components of the compound CS triggers extinction or reconsolidation of the other component. This suggests that the original training conditions play a critical role in memory retrieval and reconsolidation.

  • neural substrates for expectation modulated fear learning in the amygdala and periaqueductal gray
    Nature Neuroscience, 2010
    Co-Authors: Joshua P Johansen, Joseph E. Ledoux, Jason W Tarpley, Hugh T Blair
    Abstract:

    A form of aversively motivated learning called fear conditioning occurs when a neutral conditioned Stimulus is paired with an aversive Unconditioned Stimulus (UCS). UCS-evoked depolarization of amygdala neurons may instruct Hebbian plasticity that stores memories of the conditioned Stimulus-Unconditioned Stimulus association, but the origin of UCS inputs to the amygdala is unknown. Theory and evidence suggest that instructive UCS inputs to the amygdala will be inhibited when the UCS is expected, but this has not been found during fear conditioning. We investigated neural pathways that relay information about the UCS to the amygdala by recording neurons in the amygdala and periaqueductal gray (PAG) of rats during fear conditioning. UCS-evoked responses in both amygdala and PAG were inhibited by expectation. Pharmacological inactivation of the PAG attenuated UCS-evoked responses in the amygdala and impaired acquisition of fear conditioning, indicating that PAG may be an important part of the pathway that relays instructive signals to the amygdala.

  • the amygdala encodes specific sensory features of an aversive reinforcer
    Nature Neuroscience, 2010
    Co-Authors: Joseph E. Ledoux, Jacek Debiec, Llorenc Diazmataix, David E A Bush, Valerie Doyere
    Abstract:

    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.

  • Unconditioned Stimulus pathways to the amygdala effects of lesions of the posterior intralaminar thalamus on foot shock induced c fos expression in the subdivisions of the lateral amygdala
    Neuroscience, 2008
    Co-Authors: Enrique Lanuza, Jose Monchobogani, Joseph E. Ledoux
    Abstract:

    The lateral nucleus of the amygdala (LA) is a site of convergence for auditory (conditioned Stimulus) and foot-shock (Unconditioned Stimulus) inputs during fear conditioning. The auditory pathways to LA are well characterized, but less is known about the pathways through which foot shock is transmitted. Anatomical tracing and physiological recording studies suggest that the posterior intralaminar thalamic nucleus, which projects to LA, receives both auditory and somatosensory inputs. In the present study we examined the expression of the immediate-early gene c-fos in the LA in rats in response to foot-shock stimulation. We then determined the effects of posterior intralaminar thalamic lesions on foot-shock-induced c-Fos expression in the LA. Foot-shock stimulation led to an increase in the density of c-Fos-positive cells in all LA subnuclei in comparison to controls exposed to the conditioning box but not shocked. However, some differences among the dorsolateral, ventrolateral and ventromedial subnuclei were observed. The ventrolateral subnucleus showed a homogeneous activation throughout its antero-posterior extension. In contrast, only the rostral aspect of the ventromedial subnucleus and the central aspect of the dorsolateral subnucleus showed a significant increment in c-Fos expression. The density of c-Fos-labeled cells in all LA subnuclei was also increased in animals placed in the box in comparison to untreated animals. Unilateral electrolytic lesions of the posterior intralaminar thalamic nucleus and the medial division of the medial geniculate body reduced foot-shock-induced c-Fos activation in the LA ipsilateral to the lesion. The number of c-Fos labeled cells on the lesioned side was reduced to the levels observed in the animals exposed only to the box. These results indicate that the LA is involved in processing information about the foot-shock Unconditioned Stimulus and receives this kind of somatosensory information from the posterior intralaminar thalamic nucleus and the medial division of the medial geniculate body.

  • systematic constellations of neurons are activated in lateral amygdala following pavlovian fear conditioning
    2006
    Co-Authors: Joseph E. Ledoux, Lara W Massie, Justin P Little, Neil Haranhalli, Luke R. Johnson
    Abstract:

    How memory is organized within neural networks is a fundamental question in neuroscience. We used Pavlovian fear conditioning to study the discrete organization patterns of neurons activated in an associative memory paradigm. In Pavlovian fear conditioning a neutral Stimulus, such as an auditory tone, is temporally paired with an aversive Unconditioned Stimulus (US), such as a foot shock...

John F. Disterhoft - One of the best experts on this subject based on the ideXlab platform.

  • the effects of aging in delay and trace human eyeblink conditioning
    Psychology and Aging, 2010
    Co-Authors: Dominic T Cheng, John F. Disterhoft, Monica L Faulkner, John E Desmond
    Abstract:

    Normal aging has been shown to impact performance during human eyeblink classical conditioning, with older adults showing lower conditioning levels than younger adults. Previous findings showed younger adults can acquire both delay and trace conditioning concurrently, but it is not known whether older adults can learn under the same conditions. Present results indicated older adults did not produce a significantly greater number of conditioned responses during acquisition, but their ability to time eyeblink responses prior to the Unconditioned Stimulus was preserved. The decline in eyeblink conditioning that typically accompanies aging has been extended to concurrent presentations of delay and trace conditioning trials.

  • aging and learning specific changes in single neuron activity in ca1 hippocampus during rabbit trace eyeblink conditioning
    Journal of Neurophysiology, 2001
    Co-Authors: Matthew D Mcechron, Aldis P Weible, John F. Disterhoft
    Abstract:

    Rabbit trace eyeblink conditioning is a hippocampus-dependent task in which the auditory conditioned Stimulus (CS) is separated from the corneal airpuff Unconditioned Stimulus (US) by a 500-ms empt...

  • intact delay eyeblink classical conditioning in amnesia
    Behavioral Neuroscience, 1995
    Co-Authors: John D. E. Gabrieli, Regina Mcglincheyberroth, Maria C Carrillo, Mark A Gluck, Laird S Cermak, John F. Disterhoft
    Abstract:

    The status of classical conditioning in human amnesia was examined by comparing conditioning of the eyeblink response (the unconditional response) to a tone conditioned Stimulus (CS) paired with an airpuff Unconditioned Stimulus (US) in the delay paradigm between 7 amnesic and 7 age- and education-matched normal control participants. Amnesic patients exhibited normal baseline performance in pseudoconditioning and normal acquisition and extinction of conditioned responses in terms of the number, latency, and magnitude of eyeblinks. These results indicate that in humans, as in rabbits, brain structures critical for declarative memory are not essential for the acquisition of elementary CS-US associations.

Bernard G Schreurs - One of the best experts on this subject based on the ideXlab platform.

  • conditioning specific reflex modification of the rabbit oryctolagus cuniculus nictitating membrane response is sensitive to context
    Learning & Behavior, 2006
    Co-Authors: Bernard G Schreurs, Jimena Gonzalezjoekes, Carrie A Smithbell
    Abstract:

    Conditioning-specific reflex modification occurs when an Unconditioned response is modified in theabsence of the conditioned Stimulus as a result of pairings of the conditioned Stimulus and an Unconditioned Stimulus. In two experiments, we assessed conditioning-specific reflex modification in either a novel context (Experiment 1) or a context different from, but equally familiar in relation to, the training context (Experiment 2). Conditioning-specific reflex modification did not demonstrate sensitivity to a novel context but did demonstrate sensitivity to a change in familiar context. The data cannot be explained by Unconditioned Stimulus preexposure, overtraining, or context insensitivity. The results suggest that conditioning-specific reflex modification models normal stress and may be used to evaluate theories of and treatments for posttraumatic stress disorder.

  • classical conditioning and modification of the rabbit s oryctolagus cuniculus Unconditioned nictitating membrane response
    Behavioral and Cognitive Neuroscience Reviews, 2003
    Co-Authors: Bernard G Schreurs
    Abstract:

    A fundamental tenet of behavior is that a reflex is automatic, unconscious, involuntary, and relatively invariant. However, we have discovered that a reflex can change dramatically as a function of classical conditioning, and this change can be demonstrated independently of the conditioned Stimulus. We have termed this phenomenon conditioning-specific reflex modification (CRM). Although the behavioral laws and neural substrates of nonassociative reflex changes have been identified, the behavioral laws and neural substrates of CRM are only now being revealed. For example, CRM is similar to classical conditioning in that (a) it is a function of both the strength of conditioning and (b) the strength of the Unconditioned Stimulus, (c) it can be extinguished, and (d) it can be generalized from one Unconditioned Stimulus to another. Preliminary analysis suggests that CRM may have some features in common with post-traumatic stress disorder and may provide insights into treatment of the disorder.

  • single cue delay and trace classical conditioning in schizophrenia
    Biological Psychiatry, 2003
    Co-Authors: Stefano Marenco, Daniel R Weinberger, Bernard G Schreurs
    Abstract:

    Abstract Background Classical conditioning provides a means of addressing mechanisms of learning and can therefore help understand the pathophysiology of memory alteration in schizophrenia. Methods Single cue delay and trace eyeblink conditioning were used in patients with schizophrenia and matched normal control subjects to explore, respectively, cerebellar and hippocampal integrity during learning. We measured percent of conditioned (CRs) and Unconditioned responses (URs), their amplitude, and onset and peak latencies. We also accounted for spontaneous blink rates and Stimulus-induced responses before learning. Results During delay conditioning, patients showed CRs with longer onset and peak latencies and improved efficiency compared to normal volunteers without there being differences between patients and normal control subjects in the percentage of CRs. During trace conditioning, neither group showed an increase in CRs as a function of conditioned Stimulus–Unconditioned Stimulus pairings, in part because the level of spontaneous blink rates exceeded the level of CRs; however, patients with schizophrenia showed increased responding 150–400 msec after the conditioned Stimulus and in the last 100–150 msec before the Unconditioned Stimulus, whereas normal control subjects showed only the latter type of responses. The former type of response was more frequent in patients with schizophrenia even before either trace or delay conditioning. Conclusions These results suggest integrity of cerebellar mechanisms underlying conditioning, although the altered timing of CRs in patients may indicate differences in the modulation of such responses. Both the greater CR onset latency during delay and the presence of early nonadaptive responses during trace are compatible with the pattern of responding seen in animals with hippocampal damage.

Lin Lu - One of the best experts on this subject based on the ideXlab platform.

  • an Unconditioned Stimulus retrieval extinction procedure to prevent the return of fear memory
    Biological Psychiatry, 2014
    Co-Authors: Liyan Zhao, Baisheng Chai, Chang Yang, Qin Fang, Yan Zhang, Charles L Pickens, Lin Lu
    Abstract:

    Background Conditioned fear memories can be updated by extinction during reconsolidation, and this effect is specific to the reactivated conditioned Stimulus (CS). However, a traumatic event can be associated with several cues, and each cue can potentially trigger recollection of the event. We introduced a technique to target all diverse cues associated with an aversive event that causes fear. Methods In human experiments, 161 subjects underwent modified fear conditioning, in which they were exposed to an Unconditioned Stimulus (US) or unreinforced CS to reactivate the memory and then underwent extinction, spontaneous recovery, and reinstatement. In animal experiments, 343 rats underwent contextual fear conditioning under a similar protocol as that used in the human experiments. We also explored the molecular alterations after US reactivation in rats. Results Presentation of a lower intensity US before extinction disrupted the associations between the different CS and reactivated US in both humans and rats. This effect persisted for at least 6 months in humans and was selective to the reactivated US. This procedure was also effective for remote memories in both humans and rats. Compared with the CS, the US induced stronger endocytosis of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid glutamate receptors 1 and 2 and stronger activation of protein kinase A, p70S6 kinase, and cyclic adenosine monophosphate response element binding protein in the dorsal hippocampus in rats. Conclusions These findings demonstrate that a modified US retrieval extinction strategy may have a potential impact on therapeutic approaches to prevent the return of fear.

Marcus Lira Brandao - One of the best experts on this subject based on the ideXlab platform.

  • role of benzodiazepine and serotonergic mechanisms in conditioned freezing and antinociception using electrical stimulation of the dorsal periaqueductal gray as Unconditioned Stimulus in rats
    Psychopharmacology, 2002
    Co-Authors: V M Castilho, Carlos Eduardo Macedo, Marcus Lira Brandao
    Abstract:

    Abstract Rationale. The dorsal periaqueductal gray matter (dPAG) has been implicated in the modulation of defensive behavior. Electrical stimulation of this structure can be used as an Unconditioned Stimulus to produce a conditioned fear reaction expressed by freezing, antinociception, and autonomic responses. Objectives. This study investigated the influence of benzodiazepine, serotonergic, and opioid mechanisms on these conditioned responses. Methods. Animals implanted with an electrode and a guide cannula into the dPAG were submitted to two conditioning sessions. Each session consisted of ten pairings of the light in a distinctive chamber (CS) with the electrical stimulation of this structure at the escape threshold. On the next day, each animal was exposed only to the CS (testing) and the duration of freezing, number of rearing and grooming episodes were recorded for 5 min. Before and after the testing session, animals were submitted to the tail-flick test. Fifteen minutes before the exposure to the CS, animals received injections into the dPAG of midazolam (a positive modulator of benzodiazepine sites), α-methyl-5-hydroxytryptamine (α-Me-5-HT; an agonist of 5-HT2 receptors), naltrexone (an opioid antagonist), or vehicle. Results. Conditioning with dPAG electrical stimulation caused significant increases in the time of freezing and conditioned antinociception. Injections of midazolam into the dPAG significantly inhibited freezing behavior and antinociception due to conditioning. Injections of α-Me-5-HT inhibited the effects of conditioning on freezing without affecting conditioned antinociception. Injections of naltrexone (13 nmol/0.2 µl) did not change any of the conditioned responses studied. Conclusions. (1) Conditioned freezing and antinociception are modulated by benzodiazepine mechanisms into dPAG. (2) 5-HT2 receptors seem to regulate conditioned freezing behavior. However, conditioned antinociception was not affected by 13 nmol naltrexone. (3) Opioid mechanisms do not seem to be involved in the conditioned responses using electrical stimulation of the dPAG as Unconditioned Stimulus. Further studies with other opioid and 5-HT2 receptor antagonists are still needed to confirm the conclusions drawn from the present work.

  • conditioned antinociception and freezing using electrical stimulation of the dorsal periaqueductal gray or inferior colliculus as Unconditioned Stimulus are differentially regulated by 5 ht2a receptors in rats
    Psychopharmacology, 2001
    Co-Authors: V M Castilho, Marcus Lira Brandao
    Abstract:

    Rationale: Electrical stimulation of the dorsal periaqueductal gray matter (dPAG) and the inferior colliculus (IC) has been used as an aversive Unconditioned Stimulus. However, studies on the behavioral, sensorial and autonomic components of the conditioned fear elaborated in the midbrain tectum are lacking. Objectives: This study was undertaken to investigate the nature of the aversiveness of stimulation of the dPAG and IC as well as the modulation by 5-HT mechanisms of the fear conditioned responses to these stimulations. Methods: Animals chronically implanted with an electrode glued to a guide cannula into the dPAG or the IC were submitted to one, two or three sessions of conditioning. Each session consisted of ten pairings of the light in a distinctive chamber (CS) with the electrical stimulation of one of these regions at the escape threshold determined previously. Control groups were submitted to the same procedure, except for the conditioning sessions in which the conditioned stimuli were presented alone in one case and performed in a different context in the other. On the next day, each animal was exposed only to the CS (testing) and the duration of freezing, number of rearings, grooming, bouts of micturition and fecal boli were recorded for 5 min. Before and after the testing session, the animals were submitted to the tail-flick test. Results: The data showed that the conditioning with electrical stimulation of the dPAG and the IC caused significant increases in the time of freezing, defecation and micturition, and significant reductions in the number of rearings and grooming. On the other hand, only the conditioning with electrical stimulation of the dPAG produced significant conditioned antinociception. Microinjections of methysergide, a non-specific antagonist of 5-HT receptors, or ketanserin, an antagonist of 5-HT2A receptors, into the dPAG before testing significantly inhibited the antinociception without affecting any of the behavioral or autonomic conditioned responses. Conclusions: 1) Conditioned freezing may be produced using the electrical stimulation of the dPAG or IC as Unconditioned stimuli, 2) only the pairing of CS plus dPAG but not with IC stimulation, produces significant conditioned antinociception, 3) blockade of 5-HT2A receptors inhibits conditioned antinociception but not the conditioned defensive behavior using the electrical stimulation of the dPAG as Unconditioned Stimulus.