Aversive stimulus differentially triggers subsecond dopamine release in reward regions.

Aversive stimuli have a powerful impact on behavior and are considered to be the opposite valence of pleasure. Recent studies have determined some populations of ventral tegmental area (VTA) dopaminergic neurons are activated by several types of aversive stimuli, whereas other distinct populations are either inhibited or unresponsive. However, it is not clear where these aversion-responsive neurons project, and whether alterations in their activity translate into dopamine release in the terminal field. Here we show unequivocally that the neurochemical and anatomical substrates responsible for the perception and processing of pleasurable stimuli within the striatum are also activated by tail pinch, a classical painful and aversive stimulus. Dopamine release is triggered in the dorsal striatum and nucleus accumbens (NAc) core by tail pinch and is time locked to the duration of the stimulus, indicating that the dorsal striatum and NAc core are neural substrates, which are involved in the perception of aversive stimuli. However, dopamine is released in the NAc shell only when tail pinch is removed, indicating that the alleviation of aversive condition could be perceived as a rewarding event.

Absolute two-photon cross section of Rb measured by differential absorption.

We applied a simple, sensitive differential absorption technique to measure the two-photon cross section for the 5(2)S((1/2))(F(g) = 2) ? 5(2)D(5/2)(F(e) = 4) hyperfine transition in (85)Rb [sigma((2)) = (1.2 +/- 0.5) x 10(-18) cm(4)/W]. The detection circuit permitted straightforward measurements close to the shot-noise limit. Detailed quantitative analysis of the measurements shows excellent agreement with theory.

Simple diffuser for production of laser speckle.

A passive optical element that is a simple, inexpensive, and effective way for producing laser speckle is described. The optical element, a random phase plate, was developed in our laboratory. The statistics of the speckle pattern it produces were measured and are discussed in this paper. The phase plate was used to produce a speckled beam using a 5-mW cw He-Ne laser with a Gaussian beam profile and using a pulsed Nd:YAG laser with a nonuniform intensity profile for which the mean intensity was 10(9) W/cm(2).

Two-photon resonant upconversion in xenon.

Coherent radiation at various VUV wavelengths, e.g., 125.9, 126.1, and 125.4 nm, has been generated through fourwave mixing processes enhanced by two-photon resonances in xenon. Maximum efficiencies of the order of 10(-4) were achieved. Maximum output intensities of difference generation (2omega(1) - omega(2)) for 7p[0 (1/2)](0), 7p[1 (1/2)](2), and 6p' [1 (1/2)](2) resonant states occurred at xenon pressures of 24, 12.5, and 4 Torr, corresponding to values of phase mismatch per atom of 1.2 x 10(-18), 2.3 x 10(-18), and 7.1 x 10(-18) esu, respectively. Parametric generation at 117.0 nm through the 7s[1(1/2)](0)(1) state was also observed.