Abstract

Involvement of the dorsal hippocampus (DHPC) in conditioned-response timing and maintaining temporal information across time gaps was examined in an appetitive Pavlovian conditioning task, in which rats with sham and DHPC lesions were first conditioned to a 15-s visual cue. After acquisition, the subjects received a series of non-reinforced test trials, on which the visual cue was extended (45 s) and gaps of different duration, 0.5, 2.5, and 7.5 s, interrupted the early portion of the cue. Dorsal hippocampal-lesioned subjects underestimated the target duration of 15 s and showed broader response distributions than the control subjects on the no-gap trials in the first few blocks of test, but the accuracy and precision of their timing reached the level of that of the control subjects by the last block. On the gap trials, the DHPC-lesioned subjects showed greater rightward shifts in response distributions than the control subjects. We discussed these lesion effects in terms of temporal versus non-temporal processing (response inhibition, generalisation decrement, and inhibitory conditioning).

Highlights

  • The global prevalence of type 2 diabetes mellitus (T2DM) has been increasing steadily for the past 3 decades [1], with 80–85 percent of this burden resulting from obesity and overweight [2]

  • In the non-White ethnic groups, the prevalence of overweight and obesity increased with increasing levels of deprivation, with the steepest gradient observed in the Black ethnic population

  • Previous studies have explored the risks of T2DM incidence among different ethnic populations [3, 4, 24], this study uniquely explored the risk of T2DM associated with ethnicity in a population of individuals who were overweight or obesity

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Summary

Introduction

The global prevalence of type 2 diabetes mellitus (T2DM) has been increasing steadily for the past 3 decades [1], with 80–85 percent of this burden resulting from obesity and overweight [2]. While it is known that T2DM increases the risk of death [5, 6], there is conflicting evidence on how increased mortality risk associated with T2DM varies among ethnic populations [7, 8]. Recent work suggests previously observed excess mortality in South Asians with T2DM, may have been reversed [9]. It is not known whether the risk of mortality in overweight or obese individuals with T2DM differs by ethnicity

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