A neologism introduced by the zoologist Richard Dawkins in his book The selfish gene (1976), where it is portrayed as a unit of cultural inheritance analogous to a gene. Memes are cultural replicators, and as such are likened to viruses in that they ‘infect’ our brains by means of imitation rather than by genetic transmission. …
Category Archives: Uncategorized
Medulloblastoma
The most common malignant brain tumor in children, occurring most often in the cerebellum or posterior fossa in the vicinity of the fourth ventricle. It is ten times more likely to occur in children than adults, with the incidence being higher in boys (62%) than in girls (38%). The cells of origin of these tumors …
Meiosis (or reduction division)
A type of nuclear and cell division in which the number of chromosomes is reduced from diploid to haploid (i.e., they are halved). This means it gives rise to four reproductive cellar or gametes, each with half the number of chromosomes of the parent cell. It consists of two consecutive divisions: separation of homologous chromosomes and …
Medial (pre-) frontal cortex
Part of the brain situated at the front, right in the center of the head, which is involved in high-level processes such as thinking about oneself and other people, and especially taking the perspective of others and determining their goals (i.e., ‘mind reading’. It becomes more activated while the person is solving theory of mind …
Medulla oblongata
Part of the hindbrain positioned directly above the spinal cord and anterior to the cerebellum, it is connected to the midbrain by the pons (see figure below). Also known the spinal bulb, it forms the lowest portion of the brain stem, being pyramidal in shape and measuring about 3 cm in length, some 2 cm …
MECP2 gene
The protein MeCP2 protein is a product of the MECP2 gene. While its function has not properly understood, it appears to be involved in the genetic modification of chromatin. Although found throughout the body, the protein regulates genes related to brain function as it has been shown to be crucial in the functioning of neurons …
Measurement theory
The set of principles used to determine how attributes of an individual can be quantified from measured behaviors. One of the simplest versions of this theory is that any observed item is considered to be the sum of the true score and an independent error score. See Error score, Measurement error, Ordinal variables, True score
Mechanism
The agent or agents responsible for creating change in a process. Sometimes used interchangeable with ‘process’, the two terms are not synonymous. In dynamical systems terminology, these are referred to as control parameters, which when scaled up beyond some critical value can result in a change of state (i.e., change from one attractor to another). …
Measurement invariance
Refers to the stability of the properties of a measurementinstrument (i.e., equality of factor structure, factor loadings and factorvariances) across different populations (e.g., males versus females) or acrossmultiple testing occasions (e.g., in longitudinal research). The measurement invariance of a psychometricinstrument can be assessed directly using confirmatory factor analysis. See Factor analysis, Longitudinal studies, Latent factor/score/variable
Measurement efficacy
Any of several indices of agreement between ordinal measures. See Cohen’s kappa coefficent, Inter-rater reliability, Ordinal variables, Reliability