3/24/2023 0 Comments Graphs about thebrain![]() ![]() These indices are called the "encephalization quotient", or EQ. These residuals can then be used to calculate an index of brain size relative to what would be predicted for an animal of that body size. This is often done by calculating how far each point is from the average line in the polygon. So, what we need to do now is completely factor out body size. Does this mean that elephants and blue whales are the smartest animals on earth? There doesn't seem to be a whole lot of evidence for that. What do we make of all this? The elephant and the blue whale seem to set the most outer limits of the high vertebrate polygon. Yet, generally the primates, which as a group are considered to be the "highest" (or most complex) vertebrates, have brains that, for the most part, are only somewhat above average for mammals (e.g., look for the gorilla and chimpanzee). What else do you see in this graph? The top surface, or outer limits, of the higher vertebrate polygon is set by animals that are usually thought to be most intelligent, i.e. These lines represent the average, or best fit line, of all the data within that polygon. Notice that there is a line running from the lower left to upper right through the two polygons. Within this plot are groups of convex polygons which represent the outer boundary of a data set. Here the average weight of a brain in grams is plotted against the average weight of a body in kilograms (look at chart of brain/body sizes). This shows data about relative brain size from a number of classes of vertebrates. In this case, we are comparing brain weight/body weight ratios. These graphs (based on data from Jerison, 1973) represent a method for studying relative or proportional features among members of a taxon called "allometry". It may be difficult to eye-ball, so here are two graphs that may help us out in this discussion: ![]() What do you think? When we "controlled for" body size by making all the animals' body sizes equal, what happened? It seems to me that the human and porpoise brains were slightly larger than the brains of the other animals. If brain size indicates what capacity an animal has for processing information and coordinating the body, then perhaps those with larger brains can process more information, and thus are more intelligent. Some may say that a larger brain means a more complex animal. We conclude that the partial coherency spectrum between a pair of human brain regional fMRI time-series depends on the anatomical distance between regions: long-distance (greater than 7 cm) edges represent conditional dependence between bilaterally symmetric neocortical regions, and between regions of prefrontal and parietal association cortex in the same hemisphere, are predominantly subtended by low-frequency components.Why are we looking at brain size and body size? What is the relationship? ![]() We also show that long-distance intrahemispheric connections between regions of prefrontal and parietal cortex were more salient at low frequencies than at frequencies greater than 0.3 Hz, whereas many local or short-distance connections, such as those comprising segregated dorsal and ventral paths in posterior cortex, were also represented in the graph of high-frequency connectivity. Using these tools, we replicate the prior observations that bilaterally homologous brain regions tend to be strongly connected and functional connectivity is generally greater at low frequencies. Estimators of partial coherency and normalized partial mutual information 0, an integrated measure of partial coherence over an arbitrary frequency band, are applied. We note that undirected graphs representing conditional independence between multivariate time-series can be more readily approached in the frequency domain than the time domain. We explored properties of whole brain networks based on multivariate spectral analysis of human functional magnetic resonance imaging (fMRI) time-series measured in 90 cortical and subcortical subregions in each of five healthy volunteers studied in the (no-task) resting state. ![]()
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