Frontoparietal representations of task context support the flexible control of goal-directed cognition.

Cognitive control allows stimulus-response processing to be aligned with internal goals and is thus central to intelligent, purposeful behavior. Control is thought to depend in part on the active representation of task information in prefrontal cortex (PFC), which provides a source of contextual bias on perception, decision making, and action. In the present study, we investigated the organization, influences, and consequences of context representation as human subjects performed a cued sorting task that required them to flexibly judge the relationship between pairs of multivalent stimuli. Using a connectivity-based parcellation of PFC and multivariate decoding analyses, we determined that context is specifically and transiently represented in a region spanning the inferior frontal sulcus during context-dependent decision making. We also found strong evidence that decision context is represented within the intraparietal sulcus, an area previously shown to be functionally networked with the inferior frontal sulcus at rest and during task performance. Rule-guided allocation of attention to different stimulus dimensions produced discriminable patterns of activation in visual cortex, providing a signature of top-down bias over perception. Furthermore, demands on cognitive control arising from the task structure modulated context representation, which was found to be strongest after a shift in task rules. When context representation in frontoparietal areas increased in strength, as measured by the discriminability of high-dimensional activation patterns, the bias on attended stimulus features was enhanced. These results provide novel evidence that illuminates the mechanisms by which humans flexibly guide behavior in complex environments

Outcome Analysis of Open Fractures of the Ankle Joint

INTRODUCTION: Fractures of the ankle joint are the second most common lower limb fractures after the hip fractures and they represent 10% of all fractures with an incidence of around 137 per 1,00,000 persons per year. Around 2% of ankle fractures are open fractures. Open injuries around the ankle joint cause destruction of not only the bony architecture but also often the ligamentous and soft tissue components including skin. AIM OF THE STUDY: To study the functional and radiological outcome of open ankle fractures treated by various treatment modalities. MATERIALS AND METHODS: This is a prospective and retrospective study of open ankle fractures conducted at Institute of Orthopedics and Traumatology, RGGGH, Madras Medical College, Chennai -3 between March 2016 to August 2016. Outcome of 23 open ankle fractures analysed functionally and radiologically. RESULTS: The most common cause in our study is road traffic accidents (69%), Majority of the patients presents as Gr III A open fractures (gustilo – Anderson) 43.5 % followed by Gr III B open fractures (30.4%) and bi malleolar fractures are common (60.9%) Based on the observations of the Lauge – Hansen and AO/OTA classifications, supination external rotation type 4 (SER 4) and type 44B2 (AO) are more prevalent. CONCLUSION: Open reduction and internal fixation in Gr I and Gr II open ankle fractures results in excellent patient outcome. Post traumatic osteoarthritis of the ankle (PTOA), the most common indication for ankle arthrodesis occurs in significant number in our study (around 39.1%), contribute significantly to the poor outcome

Transitivity performance, relational hierarchy knowledge and awareness: Results of an instructional framing manipulation.

The transitive inference (TI) paradigm has been widely used to examine the role of the hippocampus in generalization. Here we consider a surprising feature of experimental findings in this task: the relatively poor transitivity performance and levels of hierarchy knowledge achieved by adult human subjects. We focussed on the influence of the task instructions on participants' subsequent performance - through a single-word framing manipulation which either specified the relation between items as transitive (i.e

Damage to the Ventromedial Prefrontal Cortex Impairs Learning from Observed Outcomes

Individuals learn both from the outcomes of their own internally generated actions ("experiential learning") and from the observation of the consequences of externally generated actions ("observational learning"). While neuroscience research has focused principally on the neural mechanisms by which brain structures such as the ventromedial prefrontal cortex (vmPFC) support experiential learning, relatively less is known regarding how learning proceeds through passive observation. We explored the necessity of the vmPFC for observational learning by testing a group of patients with damage to the vmPFC as well as demographically matched normal comparison and brain-damaged comparison groups-and a single patient with bilateral dorsal prefrontal damage-using several value-learning tasks that required learning from direct experience, observational learning, or both. We found a specific impairment in observational learning in patients with vmPFC damage manifest in the reduced influence of previously observed rewards on current choices, despite a relatively intact capacity for experiential learning. The current study provides evidence that the vmPFC plays a critical role in observational learning, suggests that there are dissociable neural circuits for experiential and observational learning, and offers an important new extension of how the vmPFC contributes to learning and memory

A genetic locus targeted to the nuclear periphery in living cells maintains its transcriptional competence

The peripheral nuclear lamina, which is largely but not entirely associated with inactive chromatin, is considered to be an important determinant of nuclear structure and gene expression. We present here an inducible system to target a genetic locus to the nuclear lamina in living mammalian cells. Using three-dimensional time-lapse microscopy, we determined that targeting of the locus requires passage through mitosis. Once targeted, the locus remains anchored to the nuclear periphery in interphase as well as in daughter cells after passage through a subsequent mitosis. Upon transcriptional induction, components of the gene expression machinery are recruited to the targeted locus, and we visualized nascent transcripts at the nuclear periphery. The kinetics of transcriptional induction at the nuclear lamina is similar to that observed at an internal nuclear region. This new cell system provides a powerful approach to study the dynamics of gene function at the nuclear periphery in living cells

It's In My Eyes, but It Doesn't Look that Way to Me

In this issue of Neuron, Hannula and Ranganath provide striking evidence that hippocampal activity predicts eye movements that reveal memory for the past even when participants' overt memory decisions are in error. Their findings bear on an ongoing debate about the relationship between mnemonic awareness and hippocampal function

Schema-driven facilitation of new hierarchy learning in the transitive inference paradigm

Prior knowledge, in the form of a mental schema or framework, is viewed to facilitate the learning of new information in a range of experimental and everyday scenarios. Despite rising interest in the cognitive and neural mechanisms underlying schema-driven facilitation of new learning, few paradigms have been developed to examine this issue in humans. Here we develop a multiphase experimental scenario aimed at characterizing schema-based effects in the context of a paradigm that has been very widely used across species, the transitive inference task. We show that an associative schema, comprised of prior knowledge of the rank positions of familiar items in the hierarchy, has a marked effect on transitivity performance and the development of relational knowledge of the hierarchy that cannot be accounted for by more general changes in task strategy. Further, we show that participants are capable of deploying prior knowledge to successful effect under surprising conditions (i.e., when corrective feedback is totally absent), but only when the associative schema is robust. Finally, our results provide insights into the cognitive mechanisms underlying such schema-driven effects, and suggest that new hierarchy learning in the transitive inference task can occur through a contextual transfer mechanism that exploits the structure of associative experiences

Semantic representations in the temporal pole predict false memories

Recent advances in neuroscience have given us unprecedented insight into the neural mechanisms of false memory, showing that artificial memories can be inserted into the memory cells of the hippocampus in a way that is indistinguishable from true memories. However, this alone is not enough to explain how false memories can arise naturally in the course of our daily lives. Cognitive psychology has demonstrated that many instances of false memory, both in the laboratory and the real world, can be attributed to semantic interference. Whereas previous studies have found that a diverse set of regions show some involvement in semantic false memory, none have revealed the nature of the semantic representations underpinning the phenomenon. Here we use fMRI with representational similarity analysis to search for a neural code consistent with semantic false memory. We find clear evidence that false memories emerge from a similarity-based neural code in the temporal pole, a region that has been called the "semantic hub" of the brain. We further show that each individual has a partially unique semantic code within the temporal pole, and this unique code can predict idiosyncratic patterns of memory errors. Finally, we show that the same neural code can also predict variation in true-memory performance, consistent with an adaptive perspective on false memory. Taken together, our findings reveal the underlying structure of neural representations of semantic knowledge, and how this semantic structure can both enhance and distort our memories

Context-specific activation of hippocampus and SN/VTA by reward is related to enhanced long-term memory for embedded objects

Animal studies indicate that hippocampal representations of environmental context modulate reward-related processing in the substantia nigra and ventral tegmental area (SN/VTA), a major origin of dopamine in the brain. Using functional magnetic resonance imaging (fMRI) in humans, we investigated the neural specificity of context-reward associations under conditions where the presence of perceptually similar neutral contexts imposed high demands on a putative hippocampal function, pattern separation. The design also allowed us to investigate how contextual reward enhances long-term memory for embedded neutral objects. SN/VTA activity underpinned specific context-reward associations in the face of perceptual similarity. A reward-related enhancement of long-term memory was restricted to the condition where the rewarding and the neutral contexts were perceptually similar, and in turn was linked to co-activation of the hippocampus (subfield DG/CA3) and SN/VTA. Thus, an ability of contextual reward to enhance memory for focal objects is closely linked to context-related engagement of hippocampal-SN/VTA circuitry

Shrimp Seed - A Critical Problem Faced by Shrimp Farmers - A Cross Sectional Analysis

Seed is a major input in shrimp farming and all the farmers and entrepreneurs depend on hatchery seeds. For expansion of brackishwater shrimp farming, a regular and steady supply of quality shrimp seeds in large quantities at a given time for stocking Is essential. Hatcheries are the source for the supply of quality hatchery seeds and stocking wild seeds Is banned. Presently, in Tamll Nadu there ore 68 shrimp hatcheries with a production capacity of 3000 million post-larvae. The survey was carried out In Nagapattinam and Thanjavur In two districts of Tamil Nadu. A sample of 300 shrimp farmers was Interviewed randomly for the study. This paper presents the prbblems pertaining to shrlmp seed encountered by the farmers and suggestions to overcome the same. The problems encountered by the farmers in both districts were lack of assurance on quality seeds, non-existence of government agency for regulating the price of seeds, high cost of seeds, non-availability of seeds from research institutes, inadequate supply of hatchery seeds, mortality of seeds during transportation, mixed seeds and deceptive method of counting the seeds. Suggestions given by them to overcome the problems were that the government research institutes should set up some mare hatcheries and virus free Nauplius shoutd be supplied to the farmers, assurance about seed quality from research institute and production of improved broodstock from government research laboratories. Since wjthout a heaithy broodstock shrimp farmers cannot hope to get quality seed, PCR was suggested as a sensitive diagnostic tool for detecting viral infection but due to various gaps in training this tool has not been used with consistent results