U-shaped learning

The learning curve that describes the unlearning of previously learned knowledge and its subsequent re-learning.  For example, in the acquisition of the English past tense, children often produce incorrect inflections of irregular verbs (e.g., ‘comed’) after previously having produced the correct ‘came’.  In the end, they learn to produce the correct form again.  See Qualitative …

Tyrosine kinase receptor/pathway

The proteins downstream of the active receptor that are involved in transducing the signal into a biologically relevant response.  See Developmental genetics, Boss (or bride of seven less, Boss (or bride of seven less), Developmental genetics, Fibroblast growth factor (FGF), Growth factors, Protein, Protein tyrosine kinase, Ras, R7 and R8 photoreceptors, Sevenless

Type 2 muscle fibers

Glycolytic fibers, with few mitochondria and rich in glycogen but low in myoglobin (the reason they are whitish in colour), that undergo fast, short-lived contractions.  Typical of muscles involved in sprinting etc. as they are activated by large diameter, and therefore fast, conduction, motoneurons.  There are two sorts of fast-twitch fibers: Type 2a muscle fibers that …

Type 1 muscle fibers

Oxidative fibers, loaded with mitochondria and rich in  myglobin (the reason why they are red in colour), that undergo slow, but long-lasting, contractions typical of tonically active postural muscles.  Thus, they are resistant to fatigue. The main reason these slow-twitch fibers are slow to fatigue is that they contain more mitochondria than fast-twitch fibers (Type …

Turing test

A proposal for a test of a machine’s capability to perform human-like conversation. Described by Alan Turing in the 1950 paper “Computing machinery and intelligence”, it proceeds as follows.  A human judge engages in a natural language conversation with two other parties, one a human and the other a machine, and both hidden by a …