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Electronic nematic materials are characterized by a lowered symmetry of the electronic system compared to the underlying lattice, in analogy to the directional alignment without translational order in nematic liquid crystals. Such nematic phases appear in the copper- and iron-based high-temperature superconductors, and their role in establishing superconductivity remains an open question. Nematicity may take an active part, cooperating or competing with superconductivity, or may appear accidentally in such systems. Here we present experimental evidence for a phase of fluctuating nematic character in a heavy-fermion superconductor, CeRhIn5(ref. 5). We observe a magnetic-field-induced state in the vicinity of a field-tuned antiferromagnetic quantum critical point at Hc≈ 50 tesla. This phase appears above an out-of-plane critical field H* ≈ 28 tesla and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component. The in-plane symmetry breaking has little apparent connection to the underlying lattice, as evidenced by the small magnitude of the magnetostriction anomaly at H*. Furthermore, no anomalies appear in the magnetic torque, suggesting the absence of metamagnetism in this field range. The appearance of nematic behaviour in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be common among correlated materials.

Following extensive lesion of the neural structures adjacent to the third ventricle, eight thirst-motivated albino rats were trained on an alternative black-white brightness discrimination in a 3-choice-point straightaway. Acquisition performance (number of errors) of these animals was comparable to that of an equal number of operated controls. These and other data reported support the position that nuclei surrounding the third ventricle play no essential role in mediating the acquisition of a thirst-motivated brightness discrimination.

NEURAL direct current (d.c.) potentials have recently received much attention1. A steady d.c. potential across amphibian cortex in a fronto-occipital plane has been observed2. These measurable exterior surface potentials are correlated with anaesthesia and sleep3,4. High correlations have been reported between transcephalic d.c. potential (measured between mid-forehead to low union), level of anaesthesia and electro-encephalograph (EEG)5. In the awake state the surface-recorded steady potentials are frontally negative, while in anaesthesia the frontal negativity decreases, that is, the forehead becomes more positive with respect to the occiput. The general relationship between EEG activity and behaviour (sleep–wakefulness) of humans and animals is, of course, well known6,7. This correlation of behaviour and EEG breaks down following the administration of anticholinergics such as atropine8. The EEG activity is slowed, whereas the animal appears excited. Such dissociation of EEG and behaviour under atropine has been observed in cat9, dog10and rabbit11.