The entorhinal-DG/CA3 pathway in the medial temporal lobe retains visual working memory of a simple surface feature.

Classic models consider working memory (WM) and long-term memory as distinct mental faculties that are supported by different neural mechanisms. Yet, there are significant parallels in the computation that both types of memory require. For instance, the representation of precise item-specific memory requires the separation of overlapping neural representations of similar information. This computation has been referred to as pattern separation, which can be mediated by the entorhinal-DG/CA3 pathway of the medial temporal lobe (MTL) in service of long-term episodic memory. However, although recent evidence has suggested that the MTL is involved in WM, the extent to which the entorhinal-DG/CA3 pathway supports precise item-specific WM has remained elusive. Here, we combine an established orientation WM task with high-resolution fMRI to test the hypothesis that the entorhinal-DG/CA3 pathway retains visual WM of a simple surface feature. Participants were retrospectively cued to retain one of the two studied orientation gratings during a brief delay period and then tried to reproduce the cued orientation as precisely as possible. By modeling the delay-period activity to reconstruct the retained WM content, we found that the anterior-lateral entorhinal cortex (aLEC) and the hippocampal DG/CA3 subfield both contain item-specific WM information that is associated with subsequent recall fidelity. Together, these results highlight the contribution of MTL circuitry to item-specific WM representation.

ADRA2B deletion variant and enhanced cognitive processing of emotional information: A meta-analytical review.

This meta-analytical review examines whether a deletion variant in ADRA2B, a gene that encodes α2B adrenoceptor in the regulation of norepinephrine availability, influences cognitive processing of emotional information in human observers. Using a multilevel modeling approach, this meta-analysis of 16 published studies with a total of 2752 participants showed that ADRA2B deletion variant was significantly associated with enhanced perceptual and cognitive task performance for emotional stimuli. In contrast, this genetic effect did not manifest in overall task performance when non-emotional content was used. Furthermore, various study-level factors, such as targeted cognitive processes (memory vs. attention/perception) and task procedures (recall vs. recognition), could moderate the size of this genetic effect. Overall, with increased statistical power and standardized analytical procedures, this meta-analysis has established the contributions of ADRA2B to the interactions between emotion and cognition, adding to the growing literature on individual differences in attention, perception, and memory for emotional information in the general population.

Schizotypy is associated with reduced mnemonic precision in visual working memory.

BACKGROUND: Working memory (WM) maintains a limited amount of information over a short period of time at the service of other ongoing mental activities. Deficits in this function are often observed in schizophrenia spectrum disorders. The present study examined whether self-report schizotypy was associated with the qualitative, quantitative, or both aspects of visual WM and whether these impairments could be accounted for by sensory memory deficits and/or depressed mood in a group of non-clinical, medication-naïve participants. METHOD: Visual WM and sensory memory were assessed in 164 medication-naïve college students using delayed and immediate color estimation tasks, respectively. Self-report measures of schizotypy and depressed mood were also collected. RESULTS: Individuals with more schizotypal features retained less precise representations in visual WM, without a significant reduction in the number of retained WM representations (i.e., capacity). In contrast, there was no significant correlation between sensory memory precision and schizotypy, suggesting that schizotypy-related imprecision in visual WM was unlikely a result of imprecise sensory memory. Furthermore, opposite patterns of WM deficits were observed for depressed mood in that it was negatively associated with WM capacity, but not with WM precision. CONCLUSION: Together, the present findings demonstrated dissociable WM deficits in schizotypy and depressed mood, providing strong evidence for unstable mental representations in schizotypy and reduced cognitive resource in depressed mood.

A dual-trace model for visual sensory memory.

Visual sensory memory refers to a transient memory lingering briefly after the stimulus offset. Although previous literature suggests that visual sensory memory is supported by a fine-grained trace for continuous representation and a coarse-grained trace of categorical information, simultaneous separation and assessment of these traces can be difficult without a quantitative model. The present study used a continuous estimation procedure to test a novel mathematical model of the dual-trace hypothesis of visual sensory memory according to which visual sensory memory could be modeled as a mixture of 2 von Mises (2VM) distributions differing in standard deviation. When visual sensory memory and working memory (WM) for colors were distinguished using different experimental manipulations in the first 3 experiments, the 2VM model outperformed Zhang and Luck (2008) standard mixture model (SM) representing a mixture of a single memory trace and random guesses, even though SM outperformed 2VM for WM. Experiment 4 generalized 2VM's advantages of fitting visual sensory memory data over SM from color to orientation. Furthermore, a single trace model and 4 other alternative models were ruled out, suggesting the necessity and sufficiency of dual traces for visual sensory memory. Together these results support the dual-trace model of visual sensory memory and provide a preliminary inquiry into the nature of information loss from visual sensory memory to WM. (PsycINFO Database Record

Transcranial direct current stimulation modulates pattern separation.

Maintaining similar memories in a distinct and nonoverlapping manner, known as pattern separation, is an important mnemonic process. The medial temporal lobe, especially the hippocampus, has been implicated in this crucial memory function. The present study thus examines whether it is possible to modulate pattern separation using bilateral transcranial direct current stimulation (tDCS) over the temporal lobes. Specifically, in this study, pattern separation was assessed using the Mnemonic Similarity Task following 15-min offline bilateral temporal lobe tDCS (left cathode and right anode or left anode and right cathode) or sham stimulation. In the Mnemonic Similarity Task, participants studied a series of sequentially presented visual objects. In the subsequent recognition memory test, participants viewed a series of sequentially presented objects that could be old images from study, novel foils, or lures that were visually similar to the studied images. Participants reported whether these images were exactly the same as, similar to, or different from the studied images. Following both active tDCS conditions, participants were less likely to identify lures as 'similar' compared with the sham condition, indicating a reduction in pattern separation resulting from temporal lobe tDCS. In contrast, no significant difference in overall accuracy was found for participants' discrimination of old and new images. Together, these results suggest that temporal lobe tDCS can selectively modulate the pattern separation function without changing participants' baseline recognition memory performance.

Distinct effects of contrast and color on subjective rating of fearfulness.

Natural scenes provide important affective cues for observers to avoid danger. From an adaptationist perspective, such cues affect the behavior of the observer and shape the evolution of the observer's response. It is evolutionarily significant for individuals to extract affective information from the environment as quickly and as efficiently as possible. However, the nearly endless variations in physical appearance of natural scenes present a fundamental challenge for perceiving significant visual information. How image-level properties, such as contrast and color, influence the extraction of affective information leading to subjective emotional perception is unclear. On the one hand, studies have shown that visual perception and emotional perception seem to interact with each other at the earliest stages in cortical processing. On the other hand, it is important for high-level subjective ratings to be invariant to low-level visual properties. Using a psychophysical approach and signal detection theory (SDT), we tested how contrast and color influenced fearfulness ratings of a set of natural scene pictures that varied in contents and in levels of fearfulness. Image contrast influenced perceptual sensitivity but not the decision criterion of fearfulness rating, whereas color affected the decision criterion but not perceptual sensitivity. These results show that different low-level visual features contribute independently to sensitivity or decision criterion in affective perception, suggesting distinct interactions between visual cognition and affective processing. Specifically, our naturalistic approach using a novel stimulus set, combined with SDT, has demonstrated two dissociable types of cognitive mechanisms underlying how image-level properties leverage the extraction of affective information in natural vision.