The ability to extract deep structures from auditory sequences is a fundamental prerequisite of language acquisition. Using fMRI in untrained macaques and humans, we investigated the brain areas involved in representing two abstract properties of a series of tones: total number of items and tone-repetition pattern. Both species represented the number of tones in intraparietal and dorsal premotor areas and the tone-repetition pattern in ventral prefrontal cortex and basal ganglia. However, we observed a joint sensitivity to both parameters only in humans, within bilateral inferior frontal and superior temporal regions. In the left hemisphere, those sites coincided with areas involved in language processing. Thus, while some abstract properties of auditory sequences are available to non-human primates, a recently evolved circuit may endow humans with a unique ability for representing linguistic and non-linguistic sequences in a unified manner.

Previous studies have shown that neurons of monkey dorsolateral prefrontal cortex (DLPFC) integrate information across modalities and maintain it throughout the delay period of working-memory (WM) tasks. However, the mechanisms of this temporal integration in the DLPFC are still poorly understood. In the present study, to further elucidate the role of the DLPFC in crossmodal WM, we trained monkeys to perform visuo-haptic (VH) crossmodal and haptic-haptic (HH) unimodal WM tasks. The neuronal activity recorded in the DLPFC in the delay period of both tasks indicates that the early-delay differential activity probably is related to the encoding of sample information with different strengths depending on task modality, that the late-delay differential activity reflects the associated (modality-independent) action component of haptic choice in both tasks (that is, the anticipation of the behavioral choice and/or active recall and maintenance of sample information for subsequent action), and that the sustained whole-delay differential activity likely bridges and integrates the sensory and action components. In addition, the VH late-delay differential activity was significantly diminished when the haptic choice was not required. Taken together, the results show that, in addition to the whole-delay differential activity, DLPFC neurons also show early-and late-delay differential activities. These previously unidentified findings indicate that DLPFC is capable of (i) holding the coded sample information (e.g., visual or tactile information) in the early-delay activity, (ii) retrieving the abstract information (orientations) of the sample (whether the sample has been haptic or visual) and holding it in the late-delay activity, and (iii) preparing for behavioral choice acting on that abstract information.prefrontal | cross-modal working memory | monkey | delay activity | single unit W orking memory (WM) is a central concept in cognitive sciences. The prefrontal cortex constitutes the highest stage in the cortical hierarchy of executive memories (1-5), and it seems to be essential for integrating sensory information of different modalities with subsequent action in goal-directed behavior (6-9).Cells involved in WM ("memory cells") were first recorded in the dorsolateral prefrontal cortex (DLPFC) of monkeys performing delayed-response tasks (10-12) and have also been reported by other subsequent primate studies (13-19). The persistent delay activity recorded in those studies reflects the maintenance of a working-memory representation and therefore underlies the representation of retrospective, current, and prospective information (20). From the results of those studies, it seems that, in addition to persistent delay activity that is sustained throughout the whole delay period in WM tasks, task/set cells, eye movement-related responses, and phasic sensory responses, etc. (14-18, 21), two other general types of prefrontal neurons have also been studied (22, 23). One is the so-called sensory-coupled cue cell, the discharge of wh...

New embeddings of weighted Sobolev spaces are established. Using such embeddings, we obtain the existence and regularity of positive solutions with Navier boundary value problems for a weighted fourth order elliptic equation. We also obtain Liouville type results for the related equation. Some problems are still open.

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Microelectrode recordings of cortical activity in primates performing working memory tasks reveal some cortical neurons exhibiting sustained or graded persistent elevations in firing rate during the period in which sensory information is actively maintained in short-term memory. These neurons are called “memory cells”. Imaging and transcranial magnetic stimulation studies indicate that memory cells may arise from distributed cortical networks. Depending on the sensory modality of the memorandum in working memory tasks, neurons exhibiting memory-correlated patterns of firing have been detected in different association cortices including prefrontal cortex, and primary sensory cortices as well. Here we elaborate on neurophysiological experiments that lead to our understanding of the neuromechanisms of working memory, and mainly discuss findings on widely distributed cortical networks involved in tactile working memory.

The detection method for direct machining the standard test pieces, which is commonly employed to exhibit the machining precision of five-axis machine tools, can truly reflect the dynamic accuracy of five-axis machine tools in the actual machining process. Existing theories on explaining the phenomenon that the ability of S-shaped test pieces to detect dynamic accuracy for five-axis machine tools are stronger than those of NAS979 test pieces mostly used the qualitative research methods, and they cannot be quantitatively used to reveal the mathematical relationship between machine tools and test pieces. Therefore, this article makes the first attempt to investigate the quantitative evaluation method for the validity of dynamic accuracy test pieces. The dynamic error function of the servo feed system in the frequency domain was derived first by establishing the mechanical system model and control system model. The method of dipole cancellation was used to acquire a simplified transfer function for the dynamic error affected by the input. Based on the zero-order hold property of the discrete input signals, the expression of dynamic error affected by input in the time domain, which intuitively shows the mathematical relationship among the machine tool performances, the test piece characteristics and the dynamic error of the servo feed system, was obtained. Then, the novel evaluation methods of the linear combinatorial value and the combinatorial linear combinatorial value were proposed. A series of comparative analyses between an S-shaped test piece and an NAS979 test piece were carried out based on the proposed new evaluation methods. A machining experiment conducted on a five-axis machine tool is used to verify the evaluation results.

This article studies point concentration phenomena of nonlinear Schrödinger equations with magnetic potentials and constant electric potentials. The existing results show that a common magnetic field has no effect on the locations of point concentrations, as long as the electric potential is not a constant. This article finds out the role of the magnetic fields in the locations of point concentrations when the electric potential is a constant.