Relatively little is known about the structural development of the basal ganglia, and what is known is largely restricted to the embryonic period. Cell migration in the sub-ventricular zone and lateral migrations to and from the diencephalon beginning in the fifth week starts the process of forming the basal ganglia. Two weeks later (i.e., by …
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Basal ganglia (disorders)
Apart from animal work, disorders of the basal ganglia in humans have revealed much about their structure-function relationships. Such disorders can be classified as hyperkinetic or hypokinetic (and hyperkinetic). Hyperkinetic disorders include ballismus (uncontrolled contractions of the proximal muscles leading to violent movements of the limbs and arising from damage to the sub-thalamic nuclei) and …
Basal ganglia (anatomy)
First clearly identified by Thomas Willis (1621-1675) in 1664, along with a number of other sub-cortical structures, it is a complex of five bilateral nuclei consisting of the caudate nucleus, putamen, globus pallidus, sub-thalamic nucleus of Luys (ventral thalamus), and the substantial nigra (pars reticula or the reticulate zone) that also include the compact zone …
Baldwin effect
A complex web of arguments, this effect in essence is based on the claim that the ability of individual organisms to learn can influence the process of evolution. Such an influence is achieved by organisms having the genetic pre-disposition for the ability to experiment with potential adaptations, select those that are beneficial for survival, continue …
Balanced (or orthogonal) design
ANOVA design in which the cells contain equal numbers of cases. See Analyses of variance (ANOVA), Orthogonality
Backpropagation
The best-known algorithm for training neural network models with more than two layers of units. The principle of the backpropagation algorithm is to change the weights in the neural network so that the discrepancy between the network’s output and the desired output (supplied by a ‘teacher’) is minimised. In general, bakcpropagation aids in the prediction …
Balance scale task
A task in which children have to predict the movement of a balance scale that has weights attached on either side of the fulcrum, and where the weights and their distance to the fulcrum vary. Always predicting the correct movement (which side goes down and which goes up) requires sophisticated knowledge of physics (torque), and …
Back-translation
The process of exporting a language-based measure (e.g., a rating scale or interview) into a culture using a different language. After translation by a bilingual expert, the result is critiqued by people from the ‘new’ country, and then translated back into the original language by an independent linguist, often a professional translator. The result is …
Babbling drift
The theory that the sounds in infant babbling begin to approximate those of the target language well before the onset of the first words. The process of approximation begins about 9-14 months. In the past, there were problems in finding data in support of this theory. More recent cross-language studies, however, have suggested relatively early …
Babinski response
Extension of the big toe upward and the spreading out of the other toes when the external portion of the newborn’s foot is stroked from the back of the heel to base of the toes (see figure below). Absent when there is damage to the lower spinal cord. First reported by François F. Babinski (1857-1932) …