A generic term for minute structures in a cell that have a particular function. Examples include: flagella, the nucleus, mitochondria, ribsomes and lysosomes (an enzyme in a membrane-bound sac in the cytoplasm required for the digestion of material in food, the destruction of foreign particles entering the cell, and the breakdown of all cell structures when …
Category Archives: Uncategorized
Ordinal variables
Variables in which higher numbers indicate higher levels of that which is measured, but the differences between adjacent numbers are not necessarily equal. Thus, what matters is the order, but not the values between variables. On ordinal measurement scales. they imply ordering of categories while the quantitative distance between levels is unknown, and the meaning …
Order
Outside the context of mathematics where it is the number of times a given function has to be differentiated to obtain a given derivative, it a qualitative statistical concept applicable to the law of entropy that refers to the regularity of arrangements or sequences of objects, numbers or events. In this respect, it is different from …
Order parameter
A low-dimensional descriptor that expresses co-operative relationships between the many degrees of freedom found in complex systems, and which serves to simplify this description for an external observer. Order parameters are determined by and created from the cooperation of microscopical quantities, while at the same time they govern the qualitative behavior of the whole system …
Orbitofrontal cortex
A key region of the frontal cortex, located on the ventral surface and lying superior to the orbit of the eyes, which appears to play a role in social judgment and emotional behavior more generally. It receives direct inputs from the dorsomedial thalamus, the temporal cortex, the ventral segmental area, the olfactory system, and the …
Optical tomography
This fNIRS method involves acquiringmultiple measurements of light at differing source-detector separationspositioned over a large area of tissue simultaneously or in rapid succession. Consequently, as the different separations penetrate tissue at differentdepths, optical tomography can measure cortical activation in 3-D space. Tomeasure the whole brain, this method is inherently restricted by thepenetration depth and reflectance …
Optical topography
A fNIRS method that involves acquiringmultiple measurements of light at differing source-detector separationspositioned over a large area of tissue simultaneously or in rapid succession.Consequently, as the different separations penetrate tissue at differentdepths, optical tomography can measure cortical activation in 3-D space. Tomeasure the whole brain, this method is inherently restricted by thepenetration depth and reflectance …
Optic nerve
The second pair of 12 cranial nerves, sometimes treated as being part of the central nervous system. Containing 1.2 million ganglion axons, it has far fewer than the number of receptors in the retina, which number above 125 million. This arrangement suggests that quite of large deal of pre-processing takes place in the retina before …
Optical imaging
Broadly speaking, a technique for studying brain activity that involves measuring tiny changes in the scattering or bending and absorption of infrared light. The simplest and most widely used type of optical imaging is endoscopy. As for brain imaging, diffuse optical imaging (DOI) is the most widely used of its type, and is also referred …
Oppositional defiant disorder (ODD)
Common childhood onset symptom constellation dominated by negativism, temper tantrums, labile mood, aggression and quarrelsome attitude. Children with ODD may also manifest learned helplessness and a lack of self-esteeem. Signs of ODD usually show before 8 years-of-age, perhaps somewhat later, but always before the teenage period. The signs appear gradually and then get worse over …