Psychometric Curve and Behavioral Strategies for Whisker-Based Texture Discrimination in Rats

The rodent whisker system is a major model for understanding neural mechanisms for tactile sensation of surface texture (roughness). Rats discriminate surface texture using the whiskers, and several theories exist for how texture information is physically sensed by the long, moveable macrovibrissae and encoded in spiking of neurons in somatosensory cortex. However, evaluating these theories requires a psychometric curve for texture discrimination, which is lacking. Here we trained rats to discriminate rough vs. fine sandpapers and grooved vs. smooth surfaces. Rats intermixed trials at macrovibrissa contact distance (nose >2 mm from surface) with trials at shorter distance (nose <2 mm from surface). Macrovibrissae were required for distant contact trials, while microvibrissae and non-whisker tactile cues were used for short distance trials. A psychometric curve was measured for macrovibrissa-based sandpaper texture discrimination. Rats discriminated rough P150 from smoother P180, P280, and P400 sandpaper (100, 82, 52, and 35 µm mean grit size, respectively). Use of olfactory, visual, and auditory cues was ruled out. This is the highest reported resolution for rodent texture discrimination, and constrains models of neural coding of texture information

NEUTRON TIME-OF-FLIGHT FACILITY AT THE UNIVERSITY-OF-SAO-PAULO 8UD PELLETRON TANDEM ACCELERATOR

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THE C-12(D,N)N-13 REACTION BETWEEN ED=7.0 AND 13.0 MEV

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Co-58: Structure of an odd-odd nucleus in the pf shell

High-spin states in the odd-odd 58 Co nucleus have been studied with the fusion-evaporation reaction 51 V( 10 B ,p 2 n ) using the γ -spectrometer Saci-Perere. Thirty-six new excited states up to spin 11 + and an excitation energy of 8.0 MeV have been observed, which are connected by 46 γ -ray transitions. Transition probabilities for 14 excited states were measured through the Doppler-shift attenuation method. The results are compared with shell-model calculations using the GXPF1 effective interaction, developed for use in the pf shell. These results were interpreted by considering particle-hole excitations with respect to the doubly magic N = Z = 28 core.status: publishe

Nuclear structure of the odd-odd nucleus Co-58

The odd–odd 58 Co nucleus has been studied with the 51 V( 10 B, p2 n ) reaction at 33 MeV and 36 MeV incident energy using the γ -spectrometer Saci-Perer ˆ e. Excited states up to 8.0 MeV and spin up to 11 + have been observed. DSAM lifetimes for 13 excited states were measured. The results are compared to shell model calculations using the GXPF1 effective interaction, developed for use in the fp shell.status: publishe

High-K band in Gd-140

High-spin states in the neutron-deficient140Gd nucleus have been studied with the 92Mo(54Fe,alpha2p) reaction at a beam energy of 240 MeV. The level scheme of 140Gd was considerably extended from what was previously known. In this work we concentrate on one of the 9 bands observed, which presents relatively strong M1 transitions and negligible signature splitting, and has an isomeric band-head, indicating a strongly coupled or high-K configuration. We compare this band to the Kpi = 8- bands observed in N=74 isotones and propose a similar configuration assignment, but with a somewhat larger deformation