What is a contour interval?
a. a loop formed by contour lines that indicates a peak or depression
b. the elevation difference between two adjacent contour lines
c. an imaginary line that joins points of equal elevation
d. the degree of a slope's steepness

The  grandmother cell  is a hypothetical  neuronthat represents a complex but specific concept or object.[1]  it activates when a person "sees, hears, or otherwise sensibly discriminates"[2]  a specific entity, such as his or her grandmother. the term was in use at least as early as 1966 amongst staff and students in the department of experimental psychology, university of cambridge, england. a similar concept, that of the  gnostic neuron, was proposed two years later