Article

Dissociated theta phase synchronization in amygdalo- hippocampal circuits during various stages of fear memory.

Institut für Physiologie I, Westfälische Wilhelms-Universität Münster, Robert-Koch-Str 27a, Münster, Germany.
European Journal of Neuroscience (Impact Factor: 3.67). 04/2007; 25(6):1823-31. DOI: 10.1111/j.1460-9568.2007.05437.x
Source: PubMed

ABSTRACT The amygdala and the hippocampus are critically involved in the formation and retention of fear memories. However, their precise contribution to, and their interplay during, fear memory formation are not fully understood. In the present study we investigated network activities in the amygdalo-hippocampal system of freely behaving mice at different stages of fear memory consolidation and retention. Our data show enhanced theta phase synchronization in this pathway during the retrieval of fear memory at long-term (24 h post-training), but not short-term (2 min, 30 min and 2 h post-training) stages, following both contextual and auditory cued conditioning. However, retrieval of remotely conditioned fear (30 days post-training) failed to induce an increase in synchronization despite there still being memory retention. Thus, our data indicate that the amygdalo-hippocampal interaction reflects a dynamic interaction of ensemble activities related to various stages of fear memory consolidation and/or retention, and support the notion that recent and remote memories are organized through different network principles.

0 Bookmarks
 · 
88 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We review recent work on the role of intrinsic amygdala networks in the regulation of classically conditioned defensive behaviors, commonly known as conditioned fear. These new developments highlight how conditioned fear depends on far more complex networks than initially envisioned. Indeed, multiple parallel inhibitory and excitatory circuits are differentially recruited during the expression versus extinction of conditioned fear. Moreover, shifts between expression and extinction circuits involve coordinated interactions with different regions of the medial prefrontal cortex. However, key areas of uncertainty remain, particularly with respect to the connectivity of the different cell types. Filling these gaps in our knowledge is important because much evidence indicates that human anxiety disorders results from an abnormal regulation of the networks supporting fear learning.
    Neuron 06/2014; 82(5):966-980. · 15.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Numerous studies have found evidence for corticolimbic theta band electroencephalographic (EEG) oscillations in the neural processing of visual stimuli perceived as threatening. However, varying temporal and topographical patterns have emerged, possibly due to varying arousal levels of the stimuli. In addition, recent studies suggest neural oscillations in delta, theta, alpha, and beta-band frequencies play a functional role in information processing in the brain. This study implemented a data-driven PCA based analysis investigating the spatiotemporal dynamics of electroencephalographic delta, theta, alpha, and beta-band frequencies during an implicit visual threat processing task. While controlling for the arousal dimension (the intensity of emotional activation), we found several spatial and temporal differences for threatening compared to nonthreatening visual images. We detected an early posterior increase in theta power followed by a later frontal increase in theta power, greatest for the threatening condition. There was also a consistent left lateralized beta desynchronization for the threatening condition. Our results provide support for a dynamic corticolimbic network, with theta and beta band activity indexing processes pivotal in visual threat processing.
    Brain and Cognition 09/2014; 91C:54-61. · 2.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Prediction error signals are fundamental to learning. Here, in mice, we show that aversive prediction signals are found in the hemodynamic responses and theta oscillations recorded from the basolateral amygdala. During fear conditioning, amygdala responses evoked by footshock progressively decreased, whereas responses evoked by the auditory cue that predicted footshock concomitantly increased. Unexpected footshock evoked larger amygdala responses than expected footshock. The magnitude of the amygdala response to the footshock predicted behavioral responses the following day. The omission of expected footshock led to a decrease below baseline in the amygdala response suggesting a negative aversive prediction error signal. Thus, in mice, amygdala activity conforms to temporal difference models of aversive learning.
    Journal of Neuroscience 07/2014; 34(27):9024-33. · 6.75 Impact Factor