Search

Objective: A Mediterranean style diet (i.e., high in fruit, vegetables, fish, pulses, and wholegrains) is said to benefit psychological health. Many low-level interoceptive processes, such as those involved in the 'gut-brain' axis, are suggested to play a mechanistic role in in this relationship. However, interoceptive sensations in other domains, and at higher hierarchical levels of abstraction, have hitherto been overlooked. One domain often studied in relation to psychological health is cardioception. Therefore, we examined whether the Mediterranean diet was associated with first-order perceptual and second-order metacognitive cardioception., Methods: Participants completed the Heartbeat Detection Task, the Heartbeat Counting Task, and the EPIC-Norfolk Food Frequency Questionnaire from which diet was quantified., Results: Adherence to a Mediterranean style diet was associated with higher cardioceptive accuracy (i.e., perceptual performance) across both tasks. In addition, those consuming a Mediterranean diet had a better ability to detect errors in first order perceptual performance, and a lower prediction error (the magnitude of the difference between accuracy and confidence)., Discussion: These findings indicated that deepening our understanding of how interoceptive processes beyond the 'gut-brain' axis are shaped by diet could deepen our understanding of the link between diet and mental health and wellbeing., Competing Interests: Declaration of Competing Interest All authors declare no conflict of interest., (Copyright © 2022. Published by Elsevier Inc.)

The impact of breakfasts of different glycaemic loads on the performance of nineteen children, aged six to seven years, was explored. Over a four week period, children attended a school breakfast club each day and ate one of three meals. Each meal offered a similar amount of energy but differed in their glycaemic load. When working individually, the behaviour of a child was rated in the classroom every ten seconds for 30 min to produce a measure of time spent on task. Memory was assessed by asking for the recall of a series of objects. The ability to sustain attention was measured by asking for a response after various delays. The incidence of negative behaviour was recorded when playing a video game that was too difficult to allow success. Two to three hours after a low glycaemic load breakfast had been consumed, performance on the tests of memory and the ability to sustain attention were better, fewer signs of frustration were displayed and initially more time was spent on task when working individually in class. The importance of the results was discussed in the context of the wide range of factors that influence behaviour in school.

The effect on the ability of children to attend to their school work, of the size of breakfast and whether a mid-morning snack had been consumed, was considered. Nine year old children were studied for four days. They reported what they had eaten for breakfast and days when they either had or had not eaten a mid-morning snack were contrasted. For an hour in the late morning, while performing individual work, activity sampling was used to establish the time spent on task. Those who had eaten a small breakfast, on average 61 kcal, spent significantly less time attending to their work than those who had eaten larger meals. The adverse effect of a small breakfast was reversed by the consumption of a mid-morning snack.

Previously it has been found that both missing breakfast and having poorer glucose tolerance were associated with better memory. The present study therefore examined the impact of eight breakfasts, in a factorial design, that contained either high or low levels of carbohydrate, fat or protein. The meals were designed to vary the rate of release of glucose into the blood stream. Memory, reaction times and vigilance were assessed 30, 75 and 120 min following breakfast. Using fasting blood glucose levels as a measure of glucose tolerance, better memory was found to be associated with better glucose tolerance and the consumption of meals that more slowly release glucose into the blood. The effects of the meals on reaction times and vigilance were opposite to those with memory in that higher levels of blood glucose tended to be associated with better performance. It was concluded that individual differences in glucose tolerance interact with the glycaemic load of a meal to influence cognitive functioning.

Although there are reports that breakfast influences both mood and memory, there has been no attempt to consider whether a subsequent snack is beneficial. One hundred and fifty young female adults either fasted or consumed breakfasts of either 10 or 50 g of carbohydrate (corn flakes). Half received a further 25 g of carbohydrate in the form of corn flakes after 1 1/2 h (snack). Predictably, those who ate breakfast, and/or a snack, reported feeling less hungry. The larger the caloric intake, the less subjects reported hunger. Those who consumed a snack reported a better mood. Eating a larger breakfast was associated with poorer mood later in the morning, an effect reversed by eating a snack. Memory for the word lists was not influenced by eating breakfast, however, 20 but not 60 min after a midmorning snack, more words were recalled. Those who had eaten breakfast, as opposed to fasting, did, however, spend longer trying to recall the words. This finding was interpreted as evidence that eating breakfast was associated with better motivation. On a number of occasions, better memory was associated with lower blood glucose levels. These findings support previous observations that better glucose tolerance was associated with better memory.

The hypothesis that the ability to control blood glucose levels influence memory and other aspects of cognition was considered. Individual differences in the ability to control blood glucose were measured by giving a glucose tolerance test (GTT) to 46 young adult females. A factor analysis of a series of measures of glucose tolerance produced four dimensions. A week later, having eaten their normal breakfast, they took tests of memory, reaction times and vigilance. The speed with which blood glucose increased, having its lowest point in the GTT, was associated with memory measured a week later. While performing the tests those with higher levels of blood glucose on arrival in the laboratory had quicker reaction times when monitoring eight but not four, two or one lamps. The finding was interpreted as demonstrating that higher levels of blood glucose specially influence tasks placing higher demands on the brain.

A group of young adult females, who had or had not eaten breakfast, drank either a glucose drink or a placebo. Fasting was associated with poorer performance on the Brown-Petersen task, a test of memory. A glucose drink improved the memory of those who had fasted, although it did not influence those who had eaten breakfast. In those who had fasted, the glucose drink resulted in memory comparable to those who had consumed breakfast. Those with higher levels of blood glucose upon arrival in the laboratory had better memories. In those taking a glucose drink, after an initial rise, rapidly falling levels of blood glucose were associated with better memory.

Previous studies have found a small association between the level of blood glucose and subjective reports of energy in those sitting quietly. Given reports that both memory and attention are influenced by the level of blood glucose it was hypothesised that under conditions of cognitive demand there would be a stronger association between mood and blood glucose levels. In three studies, with three cognitive tasks, the Stroop Task, Rapid Information Processing Task, and a difficult test of hand-eye coordination, falling blood glucose was associated with feeling less energetic.

Small unisexed groups (triads) of either male of female Swiss strain mice attack lactating intruders introduced into their home-cages. Female residents are, however, generally much more aggressive towards such intruders than are males. Ovariectomy of female residents (on day 15 or day 50 of life) has little effect on such responses, but castration of male residents significantly increases their attack on lactating intruders to a level resembling that of females. The introduction of the lactating female into the home-cage of sham-operated or gonadectomized male or female residents also enhances intragroup fighting with males (irrespective of their endocrine status) being the more aggressive. Finally, the social status of the male alters the response towards lactating females. Dominants generally show higher levels of attack, an effect that can be augmented by castration.

Previous reports of the impact of ethanol on murine aggression have produced inconsistent findings; some workers have found that low doses of ethanol increase aggression whereas others have reported either no effect or a suppression. The present study examined one variable that may help to account for these inconsistencies, namely the level of blood alcohol at various times after administration. Acute doses of 0.5, 1, 2 g/kg ethanol all potently suppressed fighting in mice. However, there was no simple relationship between blood alcohol levels and fighting. It appeared that the level of blood alcohol, whether these levels were falling and the time since alcohol was cleared from the blood were all factors that influenced the drugs anti-aggressive influence.

The influences of morphine sulphate, morphine-3-glucuronide and tifluadom on social encounters were compared in male and female mice that were allowed to interact with an anosmic male partner. The drugs were compared, as morphine sulphate is thought to act via mu, and tifluadom via kappa opiate receptors; morphine-3-glucuronide is the breakdown product of morphine. Neither morphine sulphate nor morphine-3-glucuronide significantly influenced inter-male social encounters. However, tifluadom increased non-social and decreased social behaviour, while increasing timid/defensive activities. Tifluadom did not significantly influence the behaviour of female mice in this social encounter: in contrast both morphine sulphate and morphine-3-glucuronide decreased timid/defensive behaviour and stimulated non-social behaviour. It was concluded that the results could be explained by suggesting that morphine sulphate decreases whereas tifluadom increases timidity.