Dimensions Of Activity Research Articles

Human thalamic and cortical activities assessed by dimension of activation and spectral edge frequency during sleep wake cycles.

Using spectral edge frequency (SEF95) and dimension of activation (DA), a new tool derived from the dimension of correlation, we assessed the activation of thalamus and cortex in the different vigilance states. Results were gathered from intracerebral recordings performed in 12 drug-resistant epileptic patients during video-stereoelectroencephalographic (SEEG) monitoring. In the cortex, we observed a progressive decrease of DA from wake to sleep, with minimal DA values characterizing the deep slow wave sleep (dSWS) stage. During paradoxical sleep (PS), cortical level of activity returned to DA values similar to those obtained during wakefulness. In the thalamus, DA values during wakefulness were higher than the values observed during light SWS (ISWS), deep SWS (dSWS) and PS; there were no significant differences between the 3 sleep stages. Similar variations were observed with SEF95. DA analysis proved reliable for quantification of cortical activity, in agreement with data issued from classical vigilance states scoring and spectral analysis. At the thalamic level, only 2 levels of activity within a sleep wake cycle were observed, pointing to dissociated levels of activation between the thalamus and the neocortex during ISWS and PS.

The Value of Exchange

Contemporary social exchange researchers have largely ignored how variations in the value of exchange affect power relations, concentrating instead on effects of the structure of exchange, particularly the size and shape of exchange networks. In this article, we show that value, when conceptualized and studied as a dimension of actors' alternative exchange relations, has strong and systematic effects on actors' use of power. Results of a laboratory experiment support our hypotheses, showing that an actor's power over another increases with the value of that actor's exchange with alternative partners. The effects of value on power use are comparable in strength to the effects of the availability of alternatives, and they are remarkably robust, holding for both negotiated and reciprocal forms of exchange and for networks in which the availability of alternative partners is both high and low.