Improved Visual Recognition Memory Model Based on Grid Cells for Face Recognition

Traditional facial recognition methods depend on a large number of training samples due to the massive turning of synaptic weights for low-level feature extractions. In prior work, a brain-inspired model of visual recognition memory suggested that grid cells encode translation saccadic eye movement vectors between salient stimulus features. With a small training set for each recognition type, the relative positions among the selected features for each image were represented using grid and feature label cells in Hebbian learning. However, this model is suitable only for the recognition of familiar faces, objects, and scenes. The model's performance for a given face with unfamiliar facial expressions was unsatisfactory. In this study, an improved computational model via grid cells for facial recognition was proposed. Here, the initial hypothesis about stimulus identity was obtained using the histograms of oriented gradients (HOG) algorithm. The HOG descriptors effectively captured the sample edge or gradient structure features. Thus, most test samples were successfully recognized within three saccades. Moreover, the probability of a false hypothesis and the average fixations for successful recognition were reduced. Compared with other neural network models, such as convolutional neural networks and deep belief networks, the proposed method shows the best performance with only one training sample for each face. Moreover, it is robust against image occlusion and size variance or scaling. Our results may give insight for efficient recognition with small training samples based on neural networks.

Object memory is multisensory: Task-irrelevant sounds improve recollection-based recognition memory

Hearing a task-irrelevant sound during object encoding can improve visual recognition memory when the sound is object-congruent (e.g., a dog and a bark). However, previous studies have only used binary old/new memory tests, which do not distinguish between recognition based on the recollection of details about the studied event or stimulus familiarity. In the present research, we hypothesized that hearing a task-irrelevant, but semantically congruent natural sound at encoding would facilitate the formation of richer memory representations, resulting in increased recollection of details of the encoded event. Experiment 1 replicated previous studies showing that participants were more confident about their memory for items that were initially encoded with a congruent sound compared to an incongruent or meaningless sound. Experiment 2 suggests that multisensory presentations specifically facilitate recollection and not familiarity-based recognition memory, and Experiment 3 demonstrates that this effect was coupled with more accurate memory for audiovisual congruency of the item and sound from encoding. These results suggest that even when congruent sounds are task-irrelevant, they produce a qualitative change in memory formation that supports recollection-based recognition memory. Given the ubiquity of encounters with multisensory objects in our everyday lives, considering their impact on episodic memory is integral to building models of memory that apply to naturalistic settings.

Ultra-short periods of wakeful rest promote the viewpoint-invariance of entities mnemonic representations

Humans can recognize thousands of visual objects after a single exposure, even against highly confusable objects, and despite viewpoint changes between learning and recognition. Memory consolidation processes like those taking place during wakeful rest contribute to such a feat, possibly by protecting the fine details of objects’ representations. However, whether rest-related consolidation promotes the viewpoint invariance of mnemonic representations for individual objects remains unexplored.Fifteen participants underwent a speeded visual recognition memory task tapping on familiarity-based recognition of individual objects, across four conditions manipulating post- encoding rest. Viewpoints of target items were modified between study and test while controlling study-test perceptual distance, and targets and lures shared the same subordinate category, making recognition independent from perceptual and conceptual fluency. Performance was very accurate, even without post-encoding rest, which did not enhance memory. However, rest uniquely made target detection immune to study-test perceptual distance.These findings suggest that very short periods of wakeful rest (down to 2-sec post-stimulus) suffice to achieve complete mnemonic viewpoint-invariance, pushing forward the strength of post-encoding rest in learning and memory. They also strongly argue for a holistic, viewpoint- invariant, mnemonic representation of visual objects.

Pinpointing the neural signatures of single-exposure visual recognition memory

Memories of the images that we have seen are thought to be reflected in the reduction of neural responses in high-level visual areas such as inferotemporal (IT) cortex, a phenomenon known as repetition suppression (RS). We challenged this hypothesis with a task that required rhesus monkeys to report whether images were novel or repeated while ignoring variations in contrast, a stimulus attribute that is also known to modulate the overall IT response. The monkeys’ behavior was largely contrast invariant, contrary to the predictions of an RS-inspired decoder, which could not distinguish responses to images that are repeated from those that are of lower contrast. However, the monkeys’ behavioral patterns were well predicted by a linearly decodable variant in which the total spike count was corrected for contrast modulation. These results suggest that the IT neural activity pattern that best aligns with single-exposure visual recognition memory behavior is not RS but rather sensory referenced suppression: reductions in IT population response magnitude, corrected for sensory modulation.

Acute Effects of Aerobic Exercise on Cognitive Attention and Memory Performance: An Investigation on Duration-Based Dose-Response Relations and the Impact of Increased Arousal Levels

Current evidence indicates that acute aerobic exercise might increase domain-specific cognitive performance. However, only a small number of studies deduced the impact on lower and higher cognitive functions systematically or analyzed dose–response relationships and the underlying mechanisms. This study aimed to expose the dose–response relationships by investigating the influence of exercise duration on subjective and objective arousal, cognitive attention and visual recognition memory tasks. Nineteen participants (eight female; 25.69 ± 3.11 years) were included in a randomized, three-armed intervention study in a cross-over design. The participants completed three different interventions consisting of either 15, 30 or 45 min of cycling at 60–70% VO2max. Arousal and cognitive measurements were taken before and immediately after (<2 min) exercise. All three interventions led to significant but comparable effects on self-perceived arousal, heart rate (HR) and rating of perceived exertion (RPE) (p < 0.05). Analysis of variance (ANOVA) indicated significant effects of exercise duration on visual recognition memory accuracy. Reaction times for higher and lower cognitive tasks did not change after exercise. Fifteen minutes of aerobic exercise was feasible to induce beneficial changes in self-perceived arousal. Processing speed of visual recognition memory and attention remained unaltered. Exercise exceeding fifteen minutes seemed to negatively impact visual recognition memory accuracy.