Speech sounds formed with a constriction between the dorsum (back) of the tongue and the soft palate or velum such that they vibrate loosely together. In English, there are two lingua-velar plosives: voiceless (e.g., ask, cock) and voiced (e.g., dog, good). See Consonants, Fricative, Glottal, Labio-dental, Lateral sound, Lingua-alveolar (or alveolar), Lingua-dental (or dental), Lingua-palatal …
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Lingua-dental (or dental)
Speech sounds formed with a constriction between the tongue tip and the upper central incisors, or rather the part of the gum just above these teeth. Lingua-dental fricatives are voiceless as think and maths, and voiced as in this and father. The acquisition of first teeth facilitates the production of this sound. …
Linear growth model
The representation of a longitudinal process for many individuals where there are equal changes over equal intervals of time. The resultant group and individual trajectories (or integral) can be plotted (in Cartesian coordinates) as a set of straight lines over time. See Developmental function, Longitudinal studies, Structural equation modeling (SEM)
Lingua-alveolar (or alveolar)
Consonant speech sounds formed with a constriction between the tongue tip and the alveolar ridge (a ridge located just behind the upper central incisors). There are two main forms that this sound can take: fricatives (airstream directed through a narrow constriction in the vocal tract resulting in turbulent airflow and a noisy sound), and plosives …
Linear dynamical systems
Systems in which their behavior is fully prescribed by their initial conditions. In such systems, there is a one-to-one relationship between input and output (or a proportionality between the intensity of input and the intensity of output). Such systems demonstrate only quantitative change. See Cybernetics, Determinism, Dynamical system, Dynamics, Equifinality, Isomorphism, Newtonian (or classical) mechanics, …
Limkinase 1 gene
LIM domain kinase 1 is a enzyme that in humans is encoded by the LIMK1 gene. It is a gene located in a region on the seventh chromosome and plays an important role in making protein for building the brain, and is possibly also involved in the development of nerve cells. The protein manufactured is …
Lineage
An historical sequence of ancestors and descendants (taxa, species, individuals) indicating a direct line of descent to or from a common ancestor. Evolutionary lineages are delineated through the identification of large-scale synapomorphies (i.e., shared derived features). See Convergent evolution, Founder effect (or principle), Phylogeny
Limbic system
The brain region, sometimes referred to as the rhinencephalon, consisting of highly interconnected cortical and sub-cortical areas folded into the inner surface of the temporal lobe surrounding the brain stem and bordering on the corpus callosum that are centrally involved in the generation and expression of arousal, emotion and hunger as well as memory. The …
Limb bud
The initial mesenchymal outgrowth of tissue from the flank of an embryo covered in ectoderm, which will go on to form fore and hind limbs. Becomes evident by about four weeks after conception as a result of complex interactions between the ectoderm and the underlying mesoderm (see figure below). Hox genes determine at which point …
Limbic cortices
A collective term for a number of different cortices on the edge of the cortical sheet, which has an approximately constant thickness, abuts white matter on its inner boundary, while its outer boundary adjoins cerebrospinal fluid in gyral regions and another cortical sheet in the sucal regions. See Cerebral cortex (or pallium), Cerebrospinal fluid, …