Frontiers in evolutionary neuroscience最新文献

Because the first neurons evolved in an environment high in the n-3 (omega-3) fatty acid docosahexaenoic acid (DHA), this fatty acid became a major component of neural structure and function and makes up 10% of the dry weight of the human brain. Since n-3 fatty acids must come from the diet, this suggests a possible positive role for dietary n-3 fatty acids in cognition and a possible negative role for n-6 fatty acids, which compete with n-3 for access to critical enzymes. Because human females must provide DHA for the growth of the unusually large brains of their offspring from maternal fat stored during childhood, their need for DHA is especially great. We used stepwise regression to determine whether particular dietary fatty acids and other nutrients were related to cognitive performance in over 4000 American children aged 6-16 from the Third National Health and Nutrition Examination Survey; a variety of possible biological, social, and environmental risk factors were statistically controlled. In this context the only dietary factors related to cognitive performance were n-3 and n-6 fatty acids. Dietary n-3 fatty acids were positively related to cognitive test scores in male and female children, while n-6 showed the reverse relationship, significantly so in females. In female children the positive effects of n-3 intake were twice as strong as in males and exceeded the negative effects of lead exposure. This suggests that increasing dietary intake of n-3 and decreasing n-6 fatty acids may have cognitive benefits in children, especially in females.

Recent evidence suggests that yawning is a thermoregulatory behavior. To explore this possibility further, the frequency of contagious yawning in humans was measured while outdoors in a desert climate in the United States during two distinct temperature ranges and seasons (winter: 22°C; early summer: 37°C). As predicted, the proportion of pedestrians who yawned in response to seeing pictures of people yawning differed significantly between the two conditions (winter: 45%; summer: 24%). Across conditions yawning occurred at lower ambient temperatures, and the tendency to yawn during each season was associated with the length of time spent outside prior to being tested. Participants were more likely to yawn in the milder climate after spending long periods of time outside, while prolonged exposure to ambient temperatures at or above body temperature was associated with reduced yawning. This is the first report to show that the incidence of yawning in humans is associated with seasonal climate variation, further demonstrating that yawn-induced contagion effects can be mediated by factors unrelated to individual social characteristics or cognitive development.

Brains are the centers of the nervous system of animals, controlling the organ systems of the body and coordinating responses to changes in the ecological and social environment. The evolution of traits that correlate with cognitive ability, such as relative brain size is thus of broad interest. Brain mass relative to body mass (BM) varies among mammals, and diverse factors have been proposed to explain this variation. A recent study provided evidence that energetics play an important role in brain evolution (Isler and van Schaik, 2006). Using composite phylogenies and data drawn from multiple sources, these authors showed that basal metabolic rate (BMR) correlates with brain mass across mammals. However, no such relationship was found within rodents. Here we re-examined the relationship between BMR and brain mass within Rodentia using a novel species-level phylogeny. Our results are sensitive to parameter evaluation; in particular how species mass is estimated. We detect no pattern when applying an approach used by previous studies, where each species BM is represented by two different numbers, one being the individual that happened to be used for BMR estimates of that species. However, this approach may compromise the analysis. When using a single value of BM for each species, whether representing a single individual, or available species mean, our findings provide evidence that brain mass (independent of BM) and BMR are correlated. These findings are thus consistent with the hypothesis that large brains evolve when the payoff for increased brain mass is greater than the energetic cost they incur.

Memes are the fundamental unit of cultural evolution and have been left upon the periphery of cognitive neuroscience due to their inexact definition and the consequent presumption that they are impossible to measure. Here it is argued that although a precise definition of memes is rather difficult it does not preclude highly controlled experiments studying the neural substrates of their initiation and replication. In this paper, memes are termed as either internally or externally represented (i-memes/e-memes) in relation to whether they are represented as a neural substrate within the central nervous system or in some other form within our environment. It is argued that neuroimaging technology is now sufficiently advanced to image the connectivity profiles of i-memes and critically, to measure changes to i-memes over time, i.e., as they evolve. It is argued that it is wrong to simply pass off memes as an alternative term for "stimulus" and "learnt associations" as it does not accurately account for the way in which natural stimuli may dynamically "evolve" as clearly observed in our cultural lives.

Social regulation of the internal milieu is a fundamental behavioral adaptation. Cephalic capability is reflected by anticipatory behaviors to serve systemic physiological regulation. Homeostatic regulation, a dominant perspective, reflects reactive responses; allostatic regulation, the physiology of change, emphasizes longer-term anticipatory, and feedforward systems. Steroids, such as cortisol, and peptides such as corticotrophin releasing hormone are but one example of such anticipatory regulatory systems. The concept of "allostasis" is in part to take account of anticipatory control amidst diverse forms of adaptation underlying this regulatory adaptation that supports social contact and the internal milieu.

Evolutionary approaches to dissecting our psychological architecture underscore the importance of both function and structure. Here we focus on both the function and structure of our neural circuitry and report a functional bilateral asymmetry associated with the processing of immoral stimuli. Many processes in the human brain are associated with functional specialization unique to one hemisphere. With respect to emotions, most research points to right-hemispheric lateralization. Here we provide evidence that not all emotional stimuli share right-hemispheric lateralization. Across three studies employing different paradigms, the processing of negative morally laden stimuli was found to be highly left-lateralized. Regions of engagement common to the three studies include the left medial prefrontal cortex, left temporoparietal junction, and left posterior cingulate. These data support the hypothesis that processing of immoral stimuli preferentially engages left hemispheric processes and sheds light on our evolved neural architecture.

Background: Whilst previous studies have examined comprehension of the emotional lexicon at different ages in typically developing children, no survey has been conducted looking at this across different ages from childhood to adolescence.

Purpose: To report how the emotion lexicon grows with age.

Method: Comprehension of 336 emotion words was tested in n = 377 children and adolescents, aged 4-16 years old, divided into 6 age-bands. Parents or teachers of children under 12, or adolescents themselves, were asked to indicate which words they knew the meaning of.

Results: Between 4 and 11 years old, the size of the emotional lexicon doubled every 2 years, but between 12 and 16 years old, developmental rate of growth of the emotional lexicon leveled off. This survey also allows emotion words to be ordered in terms of difficulty.

Conclusions: Studies using emotion terms in English need to be developmentally sensitive, since during childhood there is considerable change. The absence of change after adolescence may be an artifact of the words included in this study. This normative developmental data-set for emotion vocabulary comprehension may be useful when testing for delays in this ability, as might arise for environmental or neurodevelopmental reasons.

Recent research suggests that yawning is an adaptive behavior that functions to promote brain thermoregulation among homeotherms. To explore the relationship between brain temperature and yawning we implanted thermocoupled probes in the frontal cortex of rats to measure brain temperature before, during and after yawning. Temperature recordings indicate that yawns and stretches occurred during increases in brain temperature, with brain temperatures being restored to baseline following the execution of each of these behaviors. The circulatory changes that accompany yawning and stretching may explain some of the thermal similarities surrounding these events. These results suggest that yawning and stretching may serve to maintain brain thermal homeostasis.

Some numerical knowledge, such as the immediate recognition of small quantities, is observed in animals. The development of arithmetical abilities found in man's evolution as well as in child's development represents a long process following different stages. Arithmetical abilities are relatively recent in human history and are clearly related with counting, i.e., saying aloud a series of number words that correspond to a collection of objects. Counting probably began with finger sequencing, and that may explain the 10-base found in most numerical systems. From a neuropsychological perspective, there is a strong relationship between numerical knowledge and finger recognition, and both are impaired in cases of left posterior parietal damage (angular or Gerstmann's syndrome). Writing numbers appeared earlier in human history than written language. Positional digit value is clearly evident in Babylonians, and around 1,000 BC the zero was introduced. Contemporary neuroimaging techniques, specifically fMRI, have demonstrated that the left parietal lobe, particularly the intraparietal sulcus, is systematically activated during a diversity of tasks; other areas, particularly the frontal lobe, are also involved in processing numerical information and solving arithmetical problems. It can be conjectured that numerical abilities continue evolving due to advances in mathematical knowledge and the introduction of new technologies.