Perineuronal nets affect memory and learning after synapse withdrawal

Perineuronal nets (PNNs) enwrap mature neurons, playing a role in the control of plasticity and synapse dynamics. PNNs have been shown to have effects on memory formation, retention and extinction in a variety of animal models. It has been proposed that the cavities in PNNs which contain synapses can act as a memory store, which remains stable after events that cause synaptic withdrawal such as anoxia or hibernation. We examine this idea by monitoring positional memory before and after synaptic withdrawal caused by acute hibernation-like state (HLS). Animals lacking hippocampal PNNs due to enzymatic digestion by chondroitinase ABC or knockout of the PNN component aggrecan were compared with wild type controls. HLS-induced synapse withdrawal caused a memory deficit, but not to the level of naïve animals and not worsened by PNN attenuation. After HLS, animals lacking PNNs showed faster relearning. Absence of PNNs affected the restoration of inhibitory and excitatory synapses on PNN-bearing neurons. The results support a role for hippocampal PNNs in learning, but not in long-term memory storage.

The development of retro-cue benefits with extensive practice: Implications for capacity estimation and attentional states in visual working memory

Accessing the contents of visual short-term memory (VSTM) is compromised by information bottlenecks and visual interference between memorization and recall. Retro-cues, displayed after the offset of a memory stimulus and prior to the onset of a probe stimulus, indicate the test item and improve performance in VSTM tasks. It has been proposed that retro-cues aid recall by transferring information from a high-capacity memory store into visual working memory (multiple-store hypothesis). Alternatively, retro-cues could aid recall by redistributing memory resources within the same (low-capacity) working memory store (single-store hypothesis). If retro-cues provide access to a memory store with a capacity exceeding the set size, then, given sufficient training in the use of the retro-cue, near-ceiling performance should be observed. To test this prediction, 10 observers each performed 12 hours across 8 sessions in a retro-cue change-detection task (40,000+ trials total). The results provided clear support for the single-store hypothesis: retro-cue benefits (difference between a condition with and without retro-cues) emerged after a few hundred trials and then remained constant throughout the testing sessions, consistently improving performance by two items, rather than reaching ceiling performance. Surprisingly, we also observed a general increase in performance throughout the experiment in conditions with and without retro-cues, calling into question the generalizability of change-detection tasks in assessing working memory capacity as a stable trait of an observer (data and materials are available at osf.io/9xr82 and github.com/paulzerr/retrocues). In summary, the present findings suggest that retro-cues increase capacity estimates by redistributing memory resources across memoranda within a low-capacity working memory store.

Enhanced aversive memory retrieval by chemogenetic activation of locus coeruleus norepinephrine neurons

The ability to retrieve memory store in response to the environment is essential for animal behavioral adaptation. Norepinephrine (NE)-containing neurons in the brain play a key role in the modulation of synaptic plasticity underlying various processes of memory formation. However, the role of the central NE system in memory retrieval remains unclear. In this study, we developed a neural chemogenetic activation strategy using insect olfactory Ionotropic Receptors (IRs), and used it for selective stimulation of NE neurons in the locus coeruleus (LC) in transgenic mice. Ligand-induced activation of LC NE neurons resulted in enhancement of the retrieval process of conditioned taste aversion, which was mediated through at least partly adrenergic receptors in the amygdala. Pharmacological blockade of LC activity confirmed the facilitative role of these neurons in memory retrieval. Our findings indicate that the LC-amygdalar pathway is required and sufficient for enhancing the recall of taste associative memory.

Framework for Visualization of GeoSpatial Query Processing by Integrating Redis With Spark

Nowadays we are moving towards digitization and making all our devices produce a variety of data, this has paved the way to the emergence of NoSQL databases like Cassandra, MongoDB, and Redis. Big data such as geospatial data allows for geospatial analytics in applications such as tourism, marketing, and rural development. Spark frameworks provide operators storage and processing of distributed data. This article proposes “GeoRediSpark” to integrate Redis with Spark. Redis is a key-value store that uses an in-memory store, hence integrating Redis with Spark can extend the real-time processing of geospatial data. The article investigates storage and retrieval of the Redis built-in geospatial queries and has added two new geospatial operators, GeoWithin and GeoIntersect, to enhance the capabilities of Redis. Hashed indexing is used to improve the processing performance. A comparison on Redis metrics with three benchmark datasets is made. Hashset is used to display geographic data. The output of geospatial queries is visualized to the type of place and the nature of the query using Tableau.

Information recovery following a retrospective cue decreases with time

Working memory (WM) performance can be enhanced by an informative cue presented during storage. This effect, termed a retrocue benefit, can be used to explore how observers prioritize information stored in WM to guide behavior. Recent studies have demonstrated that neural representations of task-relevant memoranda are strengthened following the appearance of a retrocue, suggesting that participants can consult alternative information stores to supplement active memory traces. Here, we sought to better understand the nature of these memory store(s) by asking whether they are subject to the same temporal degradation seen in active memory representations. We reconstructed and quantified representations of remembered positions from alpha-band EEG activity recorded while participants performed a retrospectively cued spatial WM task, and varied the temporal interval separating the encoding display and retrocue. Although we observed a partial recovery of location information in all cue conditions, the magnitude of recovery was linearly and inversely related to the timing of the retrocue. This suggests that participants’ ability to supplement active memory representations with information from additional memory stores is not static: the information maintained in these stores may be subject to temporal degredation, or the stores themselves may become more difficult to access with time.

States in working memory store items with different memory quality

Working memory enables the storage of few items for a short period of time. Previous research has shown that items in working memory cannot be accessed equally well, indicating that they are held in at least two different states with different capacity limitations. However, it is unclear whether differences between states are due to limitations of the number of items that can be stored, or the quality with which items are stored. We employed a sequential whole-report proce-dure where participants reported the remembered orientation of each of 2 or 4 encoded Gabor patches. In addition, they rated their memory confidence prior to each report. Participants performed 600 trials per condition to obtain reliable subjective ratings and estimates of precision, guessing, and misreport using a mixture model, separately for each sequential report. Different measures of memory quality showed discontinuous trajectories consistently across reports with a steep drop from the first to the second remembered item but only slight decreases thereafter. In contrast, both reported and modeled guessing changed continuously across reports. Our results support the notion of two states in working memory and show that they are distinguished by memory quality rather than quantity. The first state stores high-quality representations that are highly susceptible to interference, whereas the second state contains lower-quality representa-tions that are more robust against interference.