Interpreting wide-band neural activity using convolutional neural networks.

Rapid progress in technologies such as calcium imaging and electrophysiology has seen a dramatic increase in the size and extent of neural recordings. Even so, interpretation of this data requires considerable knowledge about the nature of the representation and often depends on manual operations. Decoding provides a means to infer the information content of such recordings but typically requires highly processed data and prior knowledge of the encoding scheme. Here, we developed a deep-learning framework able to decode sensory and behavioral variables directly from wide-band neural data. The network requires little user input and generalizes across stimuli, behaviors, brain regions, and recording techniques. Once trained, it can be analyzed to determine elements of the neural code that are informative about a given variable. We validated this approach using electrophysiological and calcium-imaging data from rodent auditory cortex and hippocampus as well as human electrocorticography (ECoG) data. We show successful decoding of finger movement, auditory stimuli, and spatial behaviors - including a novel representation of head direction - from raw neural activity.

Spatial learning by mice in three dimensions.

We tested whether mice can represent locations distributed throughout three-dimensional space, by developing a novel three-dimensional radial arm maze. The three-dimensional radial maze, or "radiolarian" maze, consists of a central spherical core from which arms project in all directions. Mice learn to retrieve food from the ends of the arms without omitting any arms or re-visiting depleted ones. We show here that mice can learn both a standard working memory task, in which all arms are initially baited, and also a reference memory version in which only a subset are ever baited. Comparison with a two-dimensional analogue of the radiolarian maze, the hexagon maze, revealed equally good working-memory performance in both mazes if all the arms were initially baited, but reduced working and reference memory in the partially baited radiolarian maze. This suggests intact three-dimensional spatial representation in mice over short timescales but impairment of the formation and/or use of long-term spatial memory of the maze. We discuss potential mechanisms for how mice solve the three-dimensional task, and reasons for the impairment relative to its two-dimensional counterpart, concluding with some speculations about how mammals may represent three-dimensional space.

Weekly measurements accurately represent trends in resting energy expenditure in children undergoing hematopoietic stem cell transplantation.

BACKGROUND: Resting energy expenditure (REE) measurements are optimal for accurate assessment of energy requirements and precise provision of parenteral nutrients. We previously observed significant reduction in REE during a 4-week period in children undergoing hematopoietic stem cell transplantation (HSCT). The goal of this study was to determine if weekly REE measurements could accurately represent changes in REE in the peritransplant period compared with a more frequent standard of daily measurements. METHODS: Data are presented from a previously described cohort of 37 children undergoing HSCT. We performed weekly indirect calorimetry on 25 patients; of those 25, we performed daily measurements on a convenience sample of 5 children. The time course of REE was analyzed in each sample by repeated measures regression. RESULTS: The REE trend of the 20 weekly participants was similar to that of the 5 daily participants, reaching about 80% of predicted REE at 4 weeks posttransplant, with an average decline of 3.4% per week during 4 weeks. CONCLUSION: The results suggest that weekly REE measurements accurately characterize REE changes 4 weeks after HSCT compared with daily measurements. Characterization of these trends using weekly measurements may help guide clinical and nutrition care of these patients.

Changes in resting energy expenditure among children undergoing allogeneic stem cell transplantation.

BACKGROUND: Because of the effects of chemotherapy and radiotherapy, patients undergoing stem cell transplantation (SCT) are commonly provided nutritional support with parenteral nutrition. The energy and nutrient needs of these patients have not been well studied. OBJECTIVE: The objective was to measure resting energy expenditure (REE), dietary intake, and biochemical and anthropometric changes in children before and after allogeneic SCT. DESIGN: This was a prospective cohort study of 37 children aged 9.1 +/- 6.4 y ( +/- SD) undergoing SCT who were enrolled in an open-label trial of a unique supportive care intervention that included the routine use of oral leucovorin, vitamin E, and ursodeoxycholic acid. Parenteral nutrition was provided to match 100% of measured or estimated REE. REE was measured weekly via indirect calorimetry. RESULTS: Baseline REE was 95% of the predicted age- and sex-matched norms and was significantly correlated with midarm muscle area (r = 0.82, P < 0.001). REE fell to a nadir of approximately 80% of the predicted levels by week 3 after SCT, with a gradual increase in weeks 4 and 5. Arm anthropometric measurements showed no change in triceps skinfold thickness but significant declines in midarm muscle area after SCT. Serum vitamin E remained in the normal range. CONCLUSIONS: Children undergoing SCT show significant declines in REE after transplantation. These changes may be due to alterations in lean body mass. Standard nutritional regimens may lead to overfeeding.