Biology subjects

Ku, Y.

Publications and source records attributed to Ku, Y..

5 recordsLinked to original sources

bioRxiv2018

Atypically larger variability of resource allocation accounts for visual working memory deficits in schizophrenia

Schizophrenia patients are known to have profound deficits in visual working memory (VWM), and almost all previous studies attribute the deficits to decreased memory capacity. This account, however, ignores the potential contributions of other VWM components (e.g., memory precision). Here, we measure the VWM performance of schizophrenia patients and healthy control subjects on two classical delay-estimation tasks. Moreover, we thoroughly evaluate several established computational models of VWM to compare the performance of the two groups. We find that the model assuming variable precision across items and trials is the best model to explain the performance of both groups. According to the variable-precision model, schizophrenia subjects exhibit abnormally larger variability of allocating memory resources rather than resources per se. These results invite a rethink of the widely accepted decreased-capacity theory and propose a new perspective on the diagnosis and rehabilitation of schizophrenia.

neuroscience↗

bioRxiv2018

Root Colonization and Growth Promotion of Soybean, Wheat and Chinese Cabbage by Bacillus cereus YL6

Phosphate-solubilizing bacteria (PSB) have been isolated and used in agricultural production. However, comprehensive research on PSB colonizing the rhizosphere of different plants and promoting plant growth is lacking. This study was conducted to study the growth-promoting effects and colonizing capacity of the PSB strain YL6. The YL6 strain not only increased the biomass of pot-planted soybean and wheat but also increased the yield and growth of Chinese cabbage under field conditions. The promotion of growth in these crops by strain YL6 was related to its capacities to dissolve inorganic and organic phosphorus and to produce a certain amount of indole-3-acetic (IAA) and gibberellin (GA). After YL6 was applied to soybean, wheat and Chinese cabbage, the rhizosphere soil available phosphorus (available P) content increased by 120.16%, 62.47% and 7.21%, respectively, and the plant total phosphorus increased by 198.60%, 6.20% and 78.89%, respectively, compared with those of plants without the addition of YL6. To determine whether the phosphate solubilizing bacteria colonized these plants, YL6 labeled with green fluorescent protein (YL6-GFP) was inoculated into plant rhizospheres. YL6-GFP first colonized the root surface and hairs and then penetrated into intercellular spaces and vessels. Collectively, these results demonstrate that YL6 promoted the growth of three different crops and colonized them in a similar way and therefore provide a solid foundation for probing into mechanisms by which phosphate-solubilizing bacteria affect plant growth.

microbiology↗

bioRxiv2018

Neural mechanisms underlying the precision of visual working memory

The neural mechanisms associated with the limited capacity of working memory has long been studied, but it is still unclear how the brain maintains the fidelity of representations in working memory. Here, an orientation recall task for estimating the precision of visual working memory was performed both inside and outside an fMRI scanner. Results showed that the trial-by-trial recall error (in radians) was correlated with delay period activity in the lateral occipital complex (LOC) during working memory maintenance, regardless of the memory load. Moreover, delay activity in LOC also correlated with the individual participants precision of working memory from a separate behavioral experiment held two weeks prior. Furthermore, a region within the prefrontal cortex, the inferior frontal junction (IFJ), exhibited greater functional connectivity with LOC when the working memory load increased. Together, our findings provide unique evidence that the LOC supports visual working memory precision, while communication between the IFJ and LOC varys with visual working memory load.

neuroscience↗

bioRxiv2018

Time-dependent mnemonic vulnerability induced by new-learning

Reactivation renders consolidated memory labile again, and the ensuing temporary reconsolidation process is highly susceptible to mnemonic modification. Here, we show that memories in such an unstable state could be reprogrammed by sheer behavioral means, bypassing the need for pharmacological intervention. In two experiments using a \"face-location associationc\" paradigm in which participants experienced a \"Learning - New-learning - Final-test\" programme, we demonstrate that reactivated memory traces were robustly hampered when the new learning was strategically administered within a critical 20-minute time window. Using fMRI, we further advance our theoretical understanding that this lability can be mechanistically explained by the differential activation in the hippocampal-amygdala memory system implicated by the new-learning whereas the mnemonic intrusion caused by newly learned memories is efficaciously reconciled by the left inferior frontal gyrus. Our findings provide important implications for educational and clinical practices in devising effective strategies for memory integration.

neuroscience↗

bioRxiv2018

Locally distributed abstraction of temporal distance in human parietal cortex

An enduring puzzle in the neuroscience of memory is how the brain parsimoniously situates past events by their order in relation to time. By combining functional MRI, and representational similarity analysis, we reveal a multivoxel representation of time intervals separating pairs of episodic event-moments in the posterior medial memory system, especially when the events were experienced within a similar temporal context. We further show such multivoxel representations to be vulnerable to disruption through targeted repetitive transcranial magnetic stimulation and that perturbation to the mnemonic abstraction alters the neural--behavior relationship across the wider parietal memory network. Our findings establish a mnemonic \"pattern-based\" code of temporal distances in the human brain, a fundamental neural mechanism for supporting the temporal structure of past events, assigning the precuneus as a locus of flexibly effecting the manipulation of physical time during episodic memory retrieval.

neuroscience↗