Response Dynamics of Entorhinal Cortex in Awake, Anesthetized, and Bulbotomized Rats. <i>Brain Research</i> <b>911</b>(2)

The generation of oscillatory activity may be crucial to brain function. The coordination of individual neurons into rhythmic and coherently active populations is thought to result from interactions between excitatory and inhibitory cells mediated by local feedback connections. By using extracellular recording wires and silicon microprobes to measure electrically evoked damped oscillatory responses at the level of neural populations in the entorhinal cortex, and by using current-source density analysis to determine the spatial pattern of evoked responses, we show that the propagation of activity through the cortical circuit and consequent oscillations in the local field potential are dependent upon background neural activity. Pharmacological manipulations as well as surgical disconnection of the olfactory bulb serve to quell the background excitatory input incident to entorhinal cortex, resulting in evoked responses without characteristic oscillations and showing no signs of polysynaptic feedback. Electrical stimulation at 200 Hz applied to the lateral olfactory tract provides a substitute for the normal background activity emanating from the bulb and enables the generation of oscillatory responses once again. We conclude that a nonzero background level of activity is necessary and sufficient to sustain normal oscillatory responses and polysynaptic transmission through the entorhinal cortex

FARM-AGRIBUSINESS LINKAGES IN SOUTH AFRICA: EMPOWERING DISADVANTAGED COMMUNITIES THROUGH LINKS WITH AGRIBUSINESS

Agribusiness, Community/Rural/Urban Development,

LINKING AGRIBUSINESS AND SMALL-SCALE FARMERS IN DEVELOPING COUNTRIES: IS THERE A NEW ROLE FOR CONTRACT FARMING?

This article examines a new role for contract farming in developing countries in the light of the industrialization of agriculture and the globalization of world markets. A theoretical rationale for contracting in developing countries is developed on the basis of adopting new institutional economic theory for the purpose of matching governance forms to market failure problems and transaction characteristics. The history of contract farming is reviewed, together with the advantages and disadvantages to the various players, for the purpose of developing a list of key success factors, problems and some possible solutions.Agribusiness, Farm Management,

A Trip to the Moon: Personalized Animated Movies for Self-reflection

Self-tracking physiological and psychological data poses the challenge of presentation and interpretation. Insightful narratives for self-tracking data can motivate the user towards constructive self-reflection. One powerful form of narrative that engages audience across various culture and age groups is animated movies. We collected a week of self-reported mood and behavior data from each user and created in Unity a personalized animation based on their data. We evaluated the impact of their video in a randomized control trial with a non-personalized animated video as control. We found that personalized videos tend to be more emotionally engaging, encouraging greater and lengthier writing that indicated self-reflection about moods and behaviors, compared to non-personalized control videos

Contracting arrangements in agribusiness procurement practices in South Africa

Contracting arrangements in agribusiness procurement practices in South AfricaProcurement, contracting, agro-processing,

Competitive Advantage for Multiple-Memory Strategies in an Artificial Market

We consider a simple binary market model containing $N$ competitive agents. The novel feature of our model is that it incorporates the tendency shown by traders to look for patterns in past price movements over multiple time scales, i.e. {\em multiple memory-lengths}. In the regime where these memory-lengths are all small, the average winnings per agent exceed those obtained for either (1) a pure population where all agents have equal memory-length, or (2) a mixed population comprising sub-populations of equal-memory agents with each sub-population having a different memory-length. Agents who consistently play strategies of a given memory-length, are found to win more on average -- switching between strategies with different memory lengths incurs an effective penalty, while switching between strategies of equal memory does not. Agents employing short-memory strategies can outperform agents using long-memory strategies, even in the regime where an equal-memory system would have favored the use of long-memory strategies. Using the many-body `Crowd-Anticrowd' theory, we obtain analytic expressions which are in good agreement with the observed numerical results. In the context of financial markets, our results suggest that multiple-memory agents have a better chance of identifying price patterns of unknown length and hence will typically have higher winnings.Comment: Talk to be given at the SPIE conference on Econophysics and Finance, in the International Symposium 'Fluctuations and Noise', 23-26 May 2005 in Austin, Texa