Propofol Modulates Early Memory Consolidation in Humans.

Maintenance of memory across time is crucial for adaptive behavior. Current theories posit that the underlying consolidation process depends on stabilization of synapses and reorganization of interactions between hippocampus and neocortex. However, the temporal properties of hippocampal-neocortical network reconfiguration during consolidation are still a matter of debate. Translational research on this issue is challenged by the paucity of techniques to transiently interfere with memory in the healthy human brain. Here, we report a neuro-pharmacological approach with the GABAAergic anesthetic propofol and a memory task sensitive to hippocampal dysfunction. Patients undergoing minor surgery learned word lists before injection of an anesthetic dose of propofol. Results show that administration of the drug shortly after learning (∼13 min) impairs recall after awakening but spares recognition. By contrast, later administration (∼105 min) has no effect. These findings suggest significant changes in memory networks very early after learning that are decisive for later recall. Propofol general anesthesia provides an experimental tool to modulate the first steps of hippocampus-mediated memory consolidation in humans.

Radiofrequency denervation for treatment of sacroiliac joint pain-comparison of two different ablation techniques.

The radiofrequency treatment (RFD) for sacroiliac joint pain (SIP) is well-established, but there is still scarce evidence on its clinical outcome. The classical monopolar RFD is limited by a high recurrence rate. This might be caused by an incomplete denervation of the dorsal rami. The Simplicity III probe was invented to optimise pain fibre recruitment by its multi-electrode design. However, the clinical superiority of this procedure was never proven. The aim of this study was to illustrate the effectiveness of RFD and to compare both denervation techniques. One hundred twenty-one patients were included, and their clinical course was analysed. Fifty-seven patients received conventional treatment with multiple percutaneous monopolar RFDs (monolesion probe group, MoLG) and 64 patients with the Simplicity III probe (multilesion probe group, MuLG). All patients were followed 1, 3, 6 and 12 s after RFD. Clinical outcome scores were analysed (numeric pain rating scale (NPRS), Roland-Morris Disability Questionnaire, Oswestry Disability Index (ODI), Odom's criteria, Short Form 36 score). The MuLG showed a clearly advanced improvement concerning the clinically relevant pain relief (≥ 50%) (1 month/3 months /6 months/12 months = 72%, 55%, 36%, 27% vs. 1 month/3 months/6 months/12 months = 39%, 28%, 16%, 11%) as well as an advanced improvement of pain-associated disability and a higher satisfaction rating compared to the MoLG (NPRSMuLG_preop = 8,3; NPRSMuLG_12months = 5.8; NPRSMoLG_preop = 7,7; NPRSMoLG_12months = 5.8; ODIMuLG_preop = 52; ODIMuLG_12months = 42; ODIMoLG_preop = 52; ODIMoLG_12months = 47; ODOMSMuLG_good/excellent = 54%; ODOMSMoLG_good/excellent = 28%). RFD of the SIP with the Simplicity III probe is effective and delivers a distinct pain reduction even after 1 year of treatment. This technique shows clear advantages compared to the conventional monolesion technique and is a useful treatment for patients with recurrent SIP.

Musical memory and hippocampus revisited: Evidence from a musical layperson with highly selective hippocampal damage.

The role of the human hippocampus for musical memory is still unclear. While imaging studies in healthy humans have repeatedly shown hippocampal activation in musical memory tasks, studies in musicians with chronic bilateral medial temporal lobe damage and in non-musicians suffering from neuro-degenerative diseases suggest that musical memory may at least partly be independent of hippocampal integrity. Here, we report on a musical layperson who acutely developed an amnesic syndrome in the context of autoimmune encephalitis. Structural and resting state functional MRI revealed exceptionally selective bilateral lesions of the hippocampi and altered functional connectivity with retrosplenial cortex and precuneus. Neuropsychological testing showed a severe global amnesic syndrome. Perception and processing of scales, melodic contours, intervals, rhythms and meter were unaffected. Most notably, the patient performed completely normally on tests of recognition memory for unfamiliar melodies and excerpts of complex musical material, while recognition memory for visual and verbal information was severely impaired. Likewise, emotional evaluation of musical excerpts did not differ from controls. We infer that integrity of musical processing and recognition memory in patients with hippocampal dysfunction does not result from training-induced or post-lesional brain plasticity, but rather reflects integrity of brain networks outside the hippocampi and presumably also outside retrosplenial cortex and precuneus. Our findings suggest major differences in the neural substrates of musical and non-musical recognition memory.

Visuo-spatial memory deficits following medial temporal lobe damage: A comparison of three patient groups.

The contributions of the hippocampal formation and adjacent regions of the medial temporal lobe (MTL) to memory are still a matter of debate. It is currently unclear, to what extent discrepancies between previous human lesion studies may have been caused by the choice of distinct patient models of MTL dysfunction, as disorders affecting this region differ in selectivity, laterality and mechanisms of post-lesional compensation. Here, we investigated the performance of three distinct patient groups with lesions to the MTL with a battery of visuo-spatial short-term memory tasks. Thirty-one subjects with either unilateral damage to the MTL (postsurgical lesions following resection of a benign brain tumor, 6 right-sided lesions, 5 left) or bilateral damage (10 post-encephalitic lesions, 10 post-anoxic lesions) performed a series of tasks requiring short-term memory of colors, locations or color-location associations. We have shown previously that performance in the association task critically depends on hippocampal integrity. Patients with postsurgical damage of the MTL showed deficient performance in the association task, but performed normally in color and location tasks. Patients with left-sided lesions were almost as impaired as patients with right-sided lesions. Patients with bilateral post-encephalitic lesions showed comparable damage to MTL sub-regions and performed similarly to patients with postsurgical lesions in the association task. However, post-encephalitic patients showed additional impairments in the non-associative color and location tasks. A strikingly similar pattern of deficits was observed in post-anoxic patients. These results suggest a distinct cerebral organization of associative and non-associative short-term memory that was differentially affected in the three patient groups. Thus, while all patient groups may provide appropriate models of medial temporal lobe dysfunction in associative visuo-spatial short-term memory, additional deficits in non-associative memory tasks likely reflect damage of regions outside the MTL. Importantly, the choice of a patient model in human lesion studies of the MTL significantly influences overall performance patterns in visuo-spatial memory tasks.