Clinical studies of cingulotomy patients and imaging studies predict that the human cingulate gyrus might display pain-related activity. We now report potentials evoked by painful cutaneous stimulation with a CO2 laser (LEP) and recorded from subdural electrodes over the medial wall of the hemisphere. In response to facial laser stimulation on both sides, a negative (latency 211-242 ms) and then a positive wave (325-352 ms) were recorded from the cortex of right medial wall and from the falcine dura overlying the left medial wall. Medial wall LEPs were similar to scalp LEPs and were largest over the anterior cingulate and superior frontal gyri just anterior to motor cortex contralateral to the side of stimulation. These results demonstrate that there is significant direct nociceptive input to the human anterior cingulate gyrus (Brodmann's area 24).

Cutaneous stimulation of the face and hand with a CO2 laser in three awake patients evoked potentials (LEPs) recorded from the dominant left parasylvian cortex. These were recorded by means of a subdural grid of electrodes implanted for evaluation of epilepsy. Stimulation of the contralateral face resulted in waveforms consisting of a negative potential (N2, 162 +/- 5 ms; mean +/- SE) followed by a positive potential (P2, 340 +/- 18 ms). Both waves occurred at longer latency after hand than after facial stimulation. N2 and P2 potentials recorded from the grid correspond well in morphology to those recorded from the scalp in four additional patients tested with the same stimulation paradigm. The N2 waves recorded from the subdural grid occurred at significantly shorter latencies than did those recorded from the scalp (184 +/- 6 ms), but the P2 waves at the grid occurred at significantly longer latencies than did those recorded at the scalp (281 +/- 13 ms). The amplitudes of the potentials recorded from the grid were maximal over the parietal operculum both for contralateral stimulation of the face or hand and for ipsilateral stimulation of the face. Potentials also were recorded in this area after stimulation of the ipsilateral hand. The cortical distributions of these potentials suggest that their generators are located in the parietal operculum or in the insula, or in both, consistent with previous PET, magnetoencephalographic, and scalp LEP source analyses. These previous analyses provide indirect evidence of nociceptive input to parasylvian cortex because the interpretation of each analysis incorporates multiple assumptions. The present results are the first direct evidence of nociceptive input to the human parasylvian cortex.

The colors of copper-containing pigments, copper (II) oxide and malachite, and their origins in ceramic glazes were systematically examined over a wide firing temperature range using a suite of analytical and spectroscopy techniques including SEM, UV-Vis FORS, XRD, FTIR, and EPR to gain new insight into the structural and chemical transformations of the glaze during firing. The two colorants investigated were black copper (II) oxide (CuO) nanopowder and blue-green basic copper carbonate, or malachite (Cu2CO3(OH)2), both of which produce a final light blue color following firing. Additionally, silicon carbide (SiC) was used to locally reduce CuO to simulate firing glazes in a reductive environment and produce a final red color. At lower temperatures, malachite was found to decompose to form CuO at 550 °C, elucidating the reason that two different copper colorants could be used interchangeably to form the same “Robin’s Egg Blue” color. At 850 °C, a glaze sintering process occurred, resulting in the distribution of Cu2+ in a square planar geometry and an observed blue color. This structural change occurred at temperatures lower than the glaze’s melting point, indicating that complete vitrification of the glaze is not required for glaze coloration. Conversely, the reduction in Cu2+ to Cu+ through the addition of SiC did not occur until the glaze was fired above the melting temperature (1000 °C), signifying that high temperatures are required for the redox reaction to occur. This study sheds light on intermediate colorant-glaze interactions that are beneficial for understanding and predicting glaze coloring upon exposure to varying temperatures, and the results from this study can be applied to better-controlled glaze production for artists and a deeper appreciation of ceramic glaze chemistry and aesthetics.

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A number of recent studies have documented rapid changes in behavioural sensory acuity induced by aversive learning in the olfactory and auditory modalities. The effect of aversive learning on the discrimination of low-level features in the visual system of humans remains unclear. Here, we used a psychophysical staircase procedure to estimate discrimination thresholds for oriented grating stimuli, before and after differential aversive learning. We discovered that when a target grating orientation was conditioned with an aversive loud noise, it subsequently led to an improvement of discrimination acuity in nearly all subjects. However, no such change was observed in a control group conditioned to an orientation shifted by ±90° from the target. Our findings cannot be explained by contextual learning or sensitisation factors. The results converge with those reported in the olfactory modality and provide further evidence that early sensory systems can be rapidly modified by recently experienced reinforcement histories.

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Many lines of evidence implicate the anterior cingulate cortex (ACC, Brodmann's area 24) and parasylvian cortex in pain perception. Clinical studies demonstrate alterations in pain and temperature sensation after lesions of these structures. Imaging studies reveal increased blood flow in ACC and parasylvian cortex, both ipsilateral and contralateral to painful stimuli. Additionally, painful stimuli evoke potentials that seem to arise from these cortical structures. Short-duration cutaneous stimulation with a CO(2) laser evokes pain-related potentials (LEPs) with a vertex maximum and an initial negative peak followed by a positive wave. The cutaneous laser stimulus evokes a pure pain sensation due to selective activation of cutaneous nociceptors. Electrical source modeling has suggested that the vertex maximum of the scalp LEP arises, in part, from generators in the cingulate gyrus and parasylvian cortex. Thus, imaging and electrophysiologic studies suggest that these cortical structures are activated by painful stimuli. However, these studies incorporate multiple assumptions and therefore do not establish the presence of nociceptive inputs to ACC and parasylvian cortex. We review our recent reports of intracranial potentials evoked by painful stimuli. These studies provide direct evidence of nociceptive inputs to the human ACC and parasylvian cortex.