Relating Visual Production and Recognition of Objects in Human Visual Cortex.

Drawing is a powerful tool that can be used to convey rich perceptual information about objects in the world. What are the neural mechanisms that enable us to produce a recognizable drawing of an object, and how does this visual production experience influence how this object is represented in the brain? Here we evaluate the hypothesis that producing and recognizing an object recruit a shared neural representation, such that repeatedly drawing the object can enhance its perceptual discriminability in the brain. We scanned human participants (N = 31; 11 male) using fMRI across three phases of a training study: during training, participants repeatedly drew two objects in an alternating sequence on an MR-compatible tablet; before and after training, they viewed these and two other control objects, allowing us to measure the neural representation of each object in visual cortex. We found that: (1) stimulus-evoked representations of objects in visual cortex are recruited during visually cued production of drawings of these objects, even throughout the period when the object cue is no longer present; (2) the object currently being drawn is prioritized in visual cortex during drawing production, while other repeatedly drawn objects are suppressed; and (3) patterns of connectivity between regions in occipital and parietal cortex supported enhanced decoding of the currently drawn object across the training phase, suggesting a potential neural substrate for learning how to transform perceptual representations into representational actions. Together, our study provides novel insight into the functional relationship between visual production and recognition in the brain.SIGNIFICANCE STATEMENT Humans can produce simple line drawings that capture rich information about their perceptual experiences. However, the mechanisms that support this behavior are not well understood. Here we investigate how regions in visual cortex participate in the recognition of an object and the production of a drawing of it. We find that these regions carry diagnostic information about an object in a similar format both during recognition and production, and that practice drawing an object enhances transmission of information about it to downstream regions. Together, our study provides novel insight into the functional relationship between visual production and recognition in the brain.

α-Glucosidase Inhibitory Prenylated Anthranols from Harungana madagascariensis.

Four new prenylated anthranols, harunganols C-F (1-4), along with kenganthranol A (5), harunganin (6), and ferruginin A (7), were identified from the leaves of Harungana madagascariensis. The structures of compounds 2, 5, and 7 were confirmed by single-crystal X-ray diffraction analysis. Compound 1 is a unique symmetrical anthranol dimer connected via a CH2 group. Compound 4 possesses a unique C-10 hemiketal group. All anthranols were evaluated for their α-glucosidase inhibitory activities. They displayed a higher potency compared to acarbose except for 3 and 4. In particular, harunganol C (1) showed an IC50 value of 1.2 µM.

Protostane and fusidane triterpenes: a mini-review.

Protostane triterpenes belong to a group of tetracyclic triterpene that exhibit unique structural characteristics. Their natural distribution is primarily limited to the genus Alisma of the Alismataceae family, but they have also been occasionally found in other plant genera such as Lobelia, Garcinia, and Leucas. To date, there are 59 known protostane structures. Many of them have been reported to possess biological properties such as improving lipotropism, hepatoprotection, anti-viral activity against hepatitis B and HIV-I virus, anti-cancer activity, as well as reversal of multidrug resistance in cancer cells. On the other hand, fusidanes are fungal products characterized by 29-nor protostane structures. They possess antibiotic properties against staphylococci, including the methicillin-resistant Staphylococcus aureus (MRSA). Fusidic acid is a representative member which has found clinical applications. This review covers plant sources of the protostanes, their structure elucidation, characteristic structural and spectral properties, as well as biological activities. The fungal sources, structural features, biological activities of fusidanes are also covered in this review. Additionally, the biogenesis of these two types of triterpenes is discussed and a refined pathway is proposed.

The modulation and elimination of temporal organization in free recall.

Experiences occur in a continual succession, and the temporal structure of those experiences is often preserved in memory. The temporal contiguity effect of free recall reveals the temporal structure of memory: when a particular item is remembered, the next response is likely to come from a nearby list position. This effect is remarkably robust, appearing across a wide variety of methodological variations of the task. The temporal contiguity effect is also central to retrieved-context models, which propose temporal organization arises from the interaction of a temporal context representation with the contents of memory. Across six experiments, we demonstrate methodological manipulations that dramatically modulate and even eliminate temporal organization in free recall. We find that temporal organization is strongly modulated and in some cases potentially eliminated by strong semantic structure, the presence of retrieval practice, and a long list length. Other factors such as orienting task, paired-associate item structure, and retention interval duration have more subtle effects on temporal organization. In an accompanying set of simulations, we show that the modulation and elimination of the temporal organization follows lawful patterns predicted by the context maintenance and retrieval (CMR) retrieved-context model. We also find cases where CMR does not specifically predict the modulation of temporal organization, and in these cases our analysis suggests how the theory might be developed to account for these effects. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

The consistency of the subjective concept of randomness.

A pervasive bias in the subjective concept of randomness is that people often expect random sequences to exhibit more alternations than produced by genuine random processes. What is less known is the stability of this bias. Here, we examine two important aspects of the over-alternation bias: first, whether this bias is present in stimuli that vary across feature dimensions, sensory modalities, presentation modes and probing methods, and, second, how consistent the bias is across these stimulus variations. In Experiment 1, participants adjusted sequences until they looked maximally random. The sequences were presented as temporal streams of colors, shapes, auditory tones or tiled as spatial matrices. In Experiment 2, participants produced random matrices by adjusting the color of each cell. We replicated the findings using a within-subjects design in Experiment 3. We found that participants judged and produced over-alternating stimuli as the most random. Importantly, this bias was consistent across presentation modes (temporal vs spatial), feature dimensions (color vs shape), sensory modalities (visual vs auditory), speed (fast vs slow), stimulus size (small vs large matrices) and probing methods (adjusting the generating process vs individual bits). Overall, the results suggest that the subjective concept of randomness is highly stable across stimulus variations.