Theta oscillations support active exploration in human spatial navigation.

Active navigation seems to yield better spatial knowledge than passive navigation, but it is unclear how active decision-making influences learning and memory. Here, we examined the contributions of theta oscillations to memory-related exploration while testing theories about how they contribute to active learning. Using electroencephalography (EEG), we tested individuals on a maze-learning task in which they made discrete decisions about where to explore at each choice point in the maze. Half the participants were free to make active decisions at each choice point, and the other half passively explored by selecting a marked choice (matched to active exploration) at each intersection. Critically, all decisions were made when stationary, decoupling the active decision-making process from movement and speed factors, which is another prominent potential role for theta oscillations. Participants were then tested on their knowledge of the maze by traveling from object A to object B within the maze. Results show an advantage for active decision-making during learning and indicate that the active group had greater theta power during choice points in exploration, particularly in midfrontal channels. These findings demonstrate that active exploration is associated with theta oscillations during human spatial navigation, and that these oscillations are not exclusively related to movement or speed. Results demonstrating increased theta oscillations in prefrontal regions suggest communication with the hippocampus and integration of new information into memory. We also found evidence for alpha oscillations during active navigation, suggesting a role for attention as well. This study finds support for a general mnemonic role for theta oscillations during navigational learning.

Serum concentrations of vitamins and trace elements in clinically healthy greater flamingos (Phoeniconaias phoenicopterus rubeus) and lesser flamingos (Phoeniconaias minor).

Analysis of vitamins and trace elements has gained importance in avian medicine in recent years. It has become evident that interpretation should be based on species-specific reference intervals due to differences in intervals between species. This study was performed to evaluate the blood concentrations of vitamins A (retinol), B1 (thiamine), C (ascorbic acid), and E (alpha-tocopherol) and trace elements copper, selenium, and zinc for greater flamingos (Phoeniconaias (Phoenicopterus) rubeus) and lesser flamingos (Phoeniconaias minor). Reference intervals of vitamins and trace elements are presented for clinically healthy flamingos. Thirty-six clinically healthy greater flamingos, divided into male and female groups, and 14 healthy lesser flamingos were evaluated. There was no significant difference in the vitamin and trace element concentrations between male and female greater flamingos, but there was a statistically significant difference between greater flamingos and lesser flamingos for ascorbic acid, copper, and selenium. Blood concentration of ascorbic acid was greater (P < 0.001) in lesser flamingos (122.66 +/- 31.53 microM) than in male and female greater flamingos (40.53 +/- 13.83 and 30.44 +/- 11.43 microM, respectively). Blood concentrations of copper and selenium were greater (P < 0.001) in greater flamingos (copper: 5.57 +/- 1.3 microM for males, 5.65 +/- 1.53 microM for females; selenium: 2.74 +/- 0.43 microM for males, 2.54 +/- 0.7 microM for females) than lesser flamingos (copper: 2.45 +/- 1.96 microM; selenium: 0.45 +/- 0.29 microM). The mean +/- SD of vitamins A, B1, and E and zinc are reported as entire group (male and female greater flamingos and lesser flamingos): vitamin A, 1.54 +/- 0.45 micromM; thiamine, 0.49 +/- 0.07 jM; vitamin E, 31 +/- 9.8 micromol/L; and zinc, 29.52 +/- 6.49 microM.

[Phantom sensations and peripheral induced neglect following implantation of total hip prosthesis]. / Phantomsensationen und peripher induzierter Neglect nach Hüfttotalendoprothese.

OBJECTIVES: O. Sacks describes in his book "A leg to stand on" the inability to move his leg for along period after rupture of the tendon of m. quadriceps. He refers the history of similar cases, especially of a woman with a hip fracture. He discusses this as a result of disruption of proprioception (peripheral induced neglect). The aim of this investigation is to answer the question how frequently this symptom may be found in patients with hip fracture and/or arthrosis perioperativly after implantation of a total prosthesis. METHODS: we examined 106 patients aged 70.35 +/- 10.01 years (36-male 67.54 +/- 9.74 years and 69 female 71.9 +/- 9.9 years) who underwent an implantation of a hip prosthesis - antero-lateral access Watson-Jones - (right side n = 61, left n = 44) because of arthrosis (n = 81) or a hip fracture (n = 18) on postoperative day 1./2. and 10. - 14. Besides exact neurologic examination, we particularly asked for changed perception of the operated leg. RESULTS: by neurological examination we found only rarely signs of peripheral nerve lesion as a complication of implantation of hip prosthesis (1 femoral nerve lesion, 1 ischiadicus nerve lesion). 14 patients reported a changed perception at the first examination: 5 patients felt their operated leg shorter or longer, 4 patients described their leg changed in a strange manner (like a block of wood or lead), 2 patients felt their leg changed, but could not tell how. At follow-up examination there was no patient with a changed perception of the operated leg. CONCLUSIONS: at first examination only a small number of patients report a changed perception of the operated leg. Early mobilization of the operated leg may be the cause of quick normalization of perception. The peripherally induced neglect, described by O. Sacks, was possibly caused by decrease of cortical representation because of immobilization, but not by disrupted proprioception.