If x isa variable in a probabilistic model that takes on values in a set Ω, the prior distribution over x is simply P(x), or the (unconditional) probability thatit takes on any value in Ω. See Bayesian learning, Likelihood function, Poisson distribution, Posterior distribution
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Probabilistic epigenesis
The current idea that development is a consequence of bidirectional horizontal and vertical influences among genetic activity, neural activity, behavior, and the environment. Developmental outcomes are probable rather than predetermined because of the necessarily somewhat uncertain operation of a variety of endogenous and exogenous stimulative events. The term is accredited to Gilbert Gottlieb (1929-2006). See Causality (in …
Prion (proteinaceous infectious particle)
Abnormal or malformed (or misfolded) version of normal cellular proteins that is believed to play a role in various neurological disorders in humans (e.g., Creutzfeldt-Jacob disease) and in animals such as sheep (scrapie) and cattle (bovine spongiform encephalopathy). A hundred times smaller than a virus, it is neither a virus nor a bacterium and does not …
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Principle
A fundamental doctrine, maxim or truth that is accepted as such by a particular scientific community (e.g., Archimedes principle, principle of least effort in psychology). Certainly, the orthogenetic principle of Heinz Werner (1890-1964) would not comply with a principle under this definition. While there are distinctions to be drawn between principles, canons, rules and laws, a principle is different …
Principle of the integration and individuation of behavior
The theory of development proposed by George Ellett Coghill (1872-1941) stems from this principle, which states that development begins as a coordinated pattern of behaviors from which individual behaviors emerge due to inhibitory influences imposing themselves on the original integrated pattern. Sometimes descriptively referred to as the mass-to-specific trend in development, which ignores Coghill’s efforts to explain …
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Primary visual cortex (V1)
The part of cortex that receives direct visual input from the lateral geniculate nucleus of the thalamus, which in turn gets direct retinal input. Also called the striate cortex (due to bands or stripes of myelinated axons) and as area V1 in non-human primates and Brodmann area 17 in humans. It is located in and …
Primary sensory cortices
A general term referring to those parts of the cortex that get the most direct input from the retina (eye), cochlea (ear) or skin surface. For many years, it was held that the primary sensory cortices were not functional multimodal. More recent studies in both humans and animals has revealed that while isolated stimuli can …
Primary motor cortex
Structurally, it encompasses the precentral gyrus in the cortical area frontal to the central sulcus in each hemisphere and extends in an anterior direction across the frontal lobes. A distinctive anatomical feature of the primary motor cortex is the presence of giant pyramidal cells in the fifth layer of the cerebral cortex [the largest neurons …
Primacy effect
In contrast to the recency effect, the elevated recall for words at the beginning of a list; due presumably to items being stored in and retrieved from long-term memory. See Recall memory, Recency effect, Sensory, short-term (STM) and long-term memory (LTM)
Preyer-Tracy hypothesis of autogeneous motility
The idea that movements of the embryo begin before it is capable of responding to external stimulation as there are as yet no connections between motor and sensory neurons. Thus, the first movements of the embryo result solely from the autonomous discharge of motoneurons. The hypothesis gave rise to the notion of fixed action patterns …
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