Percutaneous screw-reinforced cement osteoplasty for palliation of postremission pain in larger lytic sacro-acetabular iliac cavities.

We present 2 cases of palliative percutaneous screw fixation for refractory pain from periacetabular residual cavities, after clinical remission, from osteolytic iliac masses involving the cortices of the sacroiliac joint (SIJ). Two patients-1 with a treated 8 cm breast metastasis and another with a treated 14 cm plasmacytoma-were selected for osseous stabilization based on imaging criteria and physical signs of iliac deformability and SIJ dysfunction. Neither lesion exhibited active malignancy following systemic therapy or discrete fracture. Following computed tomography-guided screw fixation across the mass and SIJ, with surrounding cement osteoplasty, to reduce mechanical stress on abnormal bone, both patients reported pain resolution beyond 1-year. This technique may be a suitable palliation even for large treated pelvic metastastic cavities and in the absence of fracture.

Modulation of Frontoparietal Neurovascular Dynamics in Working Memory.

Our perception of the world is represented in widespread, overlapping, and interactive neuronal networks of the cerebral cortex. A majority of physiological studies on the subject have focused on oscillatory synchrony as the binding mechanism for representation and transmission of neural information. Little is known, however, about the stability of that synchrony during prolonged cognitive operations that span more than just a few seconds. The present research, in primates, investigated the dynamic patterns of oscillatory synchrony by two complementary recording methods, surface field potentials (SFPs) and near-infrared spectroscopy (NIRS). The signals were first recorded during the resting state to examine intrinsic functional connectivity. The temporal modulation of coactivation was then examined on both signals during performance of working memory (WM) tasks with long delays (memory retention epochs). In both signals, the peristimulus period exhibited characteristic features in frontal and parietal regions. Examination of SFP signals over delays lasting tens of seconds, however, revealed alternations of synchronization and desynchronization. These alternations occurred within the same frequency bands observed in the peristimulus epoch, without a specific correspondence between any definite cognitive process (e.g., WM) and synchrony within a given frequency band. What emerged instead was a correlation between the degree of SFP signal fragmentation (in time, frequency, and brain space) and the complexity and efficiency of the task being performed. In other words, the incidence and extent of SFP transitions between synchronization and desynchronization-rather than the absolute degree of synchrony-augmented in correct task performance compared with incorrect performance or in a control task without WM demand. An opposite relationship was found in NIRS: increasing task complexity induced more uniform, rather than fragmented, NIRS coactivations. These findings indicate that the particular features of neural oscillations cannot be linearly mapped to cognitive functions. Rather, information and the cognitive operations performed on it are primarily reflected in their modulations over time. The increased complexity and fragmentation of electrical frequencies in WM may reflect the activation of hierarchically diverse cognits (cognitive networks) in that condition. Conversely, the homogeneity in coherence of NIRS responses may reflect the cumulative vascular reactions that accompany that neuroelectrical proliferation of frequencies and the longer time constant of the NIRS signal. These findings are directly relevant to the mechanisms mediating cognitive processes and to physiologically based interpretations of functional brain imaging.

Distributed and associative working memory.

This study explores the cortical cell dynamics of unimodal and cross-modal working memory (WM). Neuronal activity was recorded from parietal areas of monkeys performing delayed match-to-sample tasks with tactile or visual samples. Tactile memoranda (haptic samples) consisted of rods with differing surface features (texture or orientation of ridges) perceived by active touch. Visual memoranda (icons) consisted of striped patterns of differing orientation. In a haptic-haptic task, the animal had to retain through a period of delay the surface feature of the sample rod to select a rod that matched it. In a visual-haptic task, the animal had to retain the icon for the haptic choice of a rod with ridges of the same orientation as the icon's stripes. Units in all areas responded with firing change to one or more task events. Also in all areas, cells responded differently to different sample memoranda. Differential sample coherent firing was present in most areas during the memory period (delay). It is concluded that neurons in somatosensory and association areas of parietal cortex participate in broad networks that represent various task events and stimuli (auditory, motor, proprioceptive, tactile, and visual). Neurons in the same networks take part in retaining in WM the memorandum for each trial, whether it is encoded haptically or visually. The VH association by parietal cells in WM is analogous to the auditory-visual association previously observed in prefrontal cortex. Both illustrate the capacity of cortical neurons to associate sensory information across time and across modalities in accord with the rules of a behavioral task.

Near-infrared spectroscopy (NIRS) in cognitive neuroscience of the primate brain.

We describe the use of near-infrared spectroscopy (NIRS) as a suitable means of assessing hemodynamic changes in the cerebral cortex of awake and behaving monkeys. NIRS can be applied to animals performing cognitive tasks in conjunction with electrophysiological methods, thus offering the possibility of investigating cortical neurovascular coupling in cognition. Because it imposes fewer constraints on behavior than fMRI, NIRS appears more practical than fMRI for certain studies of cognitive neuroscience on the primate cortex. In the present study, NIRS and field potential signals were simultaneously recorded from the association cortex (posterior parietal and prefrontal) of monkeys performing two delay tasks, one spatial and the other non-spatial. Working memory was accompanied by an increase in oxygenated hemoglobin mirrored by a decrease in deoxygenated hemoglobin. Both the trends and the amplitudes of these changes differed by task and by area. Field potential records revealed slow negative potentials that preceded the task trials and persisted during their memory period. The negativity during that period was greater in prefrontal than in parietal cortex. Between tasks, the potential differences were less pronounced than the hemodynamic differences. The present feasibility study lays the groundwork for future correlative studies of cognitive function and neurovascular coupling in the primate.