Hippocampal Theta Activity During Stimulus Discrimination Task

The configural association theory and conflict resolution model both propose that hippocampal function plays role in the solving a negative patterning task but not simple discrimination task. Some hippocampal lesion study showed that inactivity of rats’ hippocampal CA1 area induced impairment of performance of a negative patterning task. Other previous studies, however, showed that the lesion did not affect the performance of the task. Thus, it did not reveal whether hippocampal function was important for solving the negative patterning task. Our recent research using an electrophysiological approach showed that the hippocampal theta power decreased with a compound stimulus of a negative patterning task, and that the hippocampal theta power was decreased by a compound stimulus of a feature negative task. These results indicate that a decrease in hippocampal theta activity is elicited by behavioral inhibition for conflict stimuli with overlapping elements. This finding strongly supports the conflict resolution model and suggests a hippocampal role in learning behavioral inhibition for conflict stimuli during nonspatial stimulus discrimination tasks

Recognition of Brain Wave Related to the Episode Memory by Deep Learning Methods

Hippocampus makes an important role of memory in the brain. In this chapter, a study of brain wave recognition using deep learning methods is introduced. The purpose of the study is to match the ripple-firings of the hippocampal activity to the episodic memories. In fact, brain spike signals of rats (300–10 kHz) were recorded and machine learning methods such as Convolutional Neural Networks (CNN), Support Vector Machine (SVM), a deep learning model VGG16, and combination models composed by CNN with SVM and VGG16 with SVM were adopted to be classifiers of the brain wave signals. Four kinds of episodic memories, that is, a male rat contacted with a female/male rat, contacted with a novel object, and an experience of restrain stress, were detected corresponding to the ripple waves of Multiple-Unit Activities (MUAs) of hippocampal CA1 neurons in male rats in the experiments. The experiment results showed the possibility of matching of ripple-like firing patterns of hippocampus to episodic memory activities of rats, and it suggests disorders of memory function may be found by the analysis of brain waves

The Caenorhabditis elegans Elongator Complex Regulates Neuronal α-tubulin Acetylation

Although acetylated α-tubulin is known to be a marker of stable microtubules in neurons, precise factors that regulate α-tubulin acetylation are, to date, largely unknown. Therefore, a genetic screen was employed in the nematode Caenorhabditis elegans that identified the Elongator complex as a possible regulator of α-tubulin acetylation. Detailed characterization of mutant animals revealed that the acetyltransferase activity of the Elongator is indeed required for correct acetylation of microtubules and for neuronal development. Moreover, the velocity of vesicles on microtubules was affected by mutations in Elongator. Elongator mutants also displayed defects in neurotransmitter levels. Furthermore, acetylation of α-tubulin was shown to act as a novel signal for the fine-tuning of microtubules dynamics by modulating α-tubulin turnover, which in turn affected neuronal shape. Given that mutations in the acetyltransferase subunit of the Elongator (Elp3) and in a scaffold subunit (Elp1) have previously been linked to human neurodegenerative diseases, namely Amyotrophic Lateral Sclerosis and Familial Dysautonomia respectively highlights the importance of this work and offers new insights to understand their etiology

Contextual Learning Requires Functional Diversity at Excitatory and Inhibitory Synapses onto CA1 Pyramidal Neurons

Although the hippocampus is processing temporal and spatial information in particular context, the encoding rule creating memory is completely unknown. To examine the mechanism, we trained rats on an inhibitory avoidance (IA) task, a hippocampus-dependent rapid one-trial contextual learning paradigm. By combining Herpes virus-mediated in vivo gene delivery with in vitro patch-clamp recordings, I reported contextual learning drives GluR1-containing AMPA receptors into CA3-CA1 synapses. The molecular event is required for contextual memory, since bilateral expression of delivery blocker in CA1 successfully blocked IA learning. Moreover, I found a logarithmic correlation between the number of delivery blocking cells and learning performance. Considering that one all-or-none device can process 1-bit of data per clock (Nobert Wiener 1961), the logarithmic correlation may provides evidence that CA1 neurons transmit essential data of contextual information. Further, I recently reported critical role of acetylcholine as an intrinsic trigger of learning-dependent synaptic plasticity. IA training induced ACh release in CA1 that strengthened not only AMPA receptor-mediated excitatory synapses, but also GABAA receptor-mediated inhibitory synapses on each CA1 neuron. More importantly, IA-trained rats showed individually different excitatory and inhibitory synaptic inputs with wide variation on each CA1 neuron. Here I propose a new hypothesis that the diversity of synaptic inputs on CA1 neurons may depict cell-specific outputs processing experienced episodes after training

Classification of Hippocampal Ripples: Convolutional Neural Network Learns Episode-Specific Changes

The hippocampus is known to play an important role in memory by processing spatiotemporal information of episodic experiences. By recording synchronized multiple-unit firing events (ripple firings with 300 Hz–10 kHz) of hippocampal CA1 neurons in freely moving rats, we previously found an episode-dependent diversity in the waveform of ripple firings. In the present study, we hypothesized that changes in the diversity would depend on the type of episode experienced. If this hypothesis holds, we can identify the ripple waveforms associated with each episode. Thus, we first attempted to classify the ripple firings measured from rats into five categories: those experiencing any of the four episodes and those before experiencing any of the four episodes. In this paper, we construct a convolutional neural network (CNN) to classify the current stocks of ripple firings into these five categories and demonstrate that the CNN can successfully classify the ripple firings. We subsequently indicate partial ripple waveforms that the CNN focuses on for classification by applying gradient-weighted class activation mapping (Grad-CAM) to the CNN. The method of t-distributed stochastic neighbor embedding (t-SNE) maps ripple waveforms into a two-dimensional feature space. Analyzing the distribution of partial waveforms extracted by Grad-CAM in a t-SNE feature space suggests that the partial waveforms may be representative of each category

Contextual learning requires synaptic AMPA receptor delivery in the hippocampus

The hippocampus plays a central role in learning and memory. Although synaptic delivery of AMPA-type glutamate receptors (AMPARs) contributes to experience-dependent synaptic strengthening, its role in hippocampus-dependent learning remains elusive. By combining viral-mediated in vivo gene delivery with in vitro patch-clamp recordings, we found that the inhibitory avoidance task, a hippocampus-dependent contextual fear-learning paradigm, delivered GluR1-containing AMPARs into CA3-CA1 synapses of the dorsal hippocampus. To block the synaptic delivery of endogenous AMPARs, we expressed a fragment of the GluR1-cytoplasmic tail (the 14-aa GluR1 membrane-proximal region with two serines mutated to phospho-mimicking aspartates: MPR-DD). MPR-DD prevented learning-driven synaptic AMPAR delivery in CA1 neurons. Bilateral expression of MPR-DD in the CA1 region of the rat impaired inhibitory avoidance learning, indicating that synaptic GluR1 trafficking in the CA1 region of the hippocampus is required for encoding contextual fear memories. The fraction of CA1 neurons that underwent synaptic strengthening positively correlated with the performance in the inhibitory avoidance fear memory task. These data suggest that the robustness of a contextual memory depends on the number of hippocampal neurons that participate in the encoding of a memory trac

Effects of rearing condition on male copulatory behavior in 3 consecutive weekly sessions.

<p>Male rats reared in an enriched environment (EE, blue dots) showed a decreased number of ejaculations (A) and intromissions (C) and prolonged ejaculation latencies (B) compared with rats reared in a standard environment (SE, green dots). On the other hand, there were no group differences in intromission latencies (D). *<i>P</i><0.001 compared with SE, ANOVA for repeated measures.</p