Where does block collide?

A deliberate interruption of nerve conduction by placing a local anesthetic drug around a nerve or plexus, so that feeling and pain signals from the region it serves are stopped for a time. William Halsted's 1885 report on the use of cocaine described injecting the drug near a nerve trunk to abolish feeling downstream, the first regional nerve block in surgery. Ruetsch, Boni, and Borgeat's 2001 From cocaine to ropivacaine traced how safer local anesthetic drugs later refined the technique. The referent here is a medical procedure that silences a living nerve, not a grouping of plots in an experiment, a barrier to new learning, or a record in a digital chain.[1][2]

Unit

One anesthetic injection around a nerve or plexus, by drug, dose, and site

Recovery means

Feeling returns as the drug is cleared and the nerve resumes conduction

Measured by

Assessed by onset, spread, and duration of loss of feeling and by pain scores

The practice of sorting experimental units into groups that are alike within each group, called blocks, so that treatments are compared within a block and known differences between blocks do not muddy the comparison. Ronald Fisher's 1926 The arrangement of field experiments set out randomized blocks for agricultural trials, and his 1935 book The Design of Experiments made the randomized block design a standard tool. The referent is a way of arranging a study to control nuisance variation, not an anesthetic procedure, a limit on learning, or a unit of stored data.[3][4]

Unit

One block, a set of similar units within which treatments are compared

Recovery means

Not applicable

Measured by

Its worth shows in the reduced error variance and tighter treatment estimates it yields

A finding in associative learning that if an animal has already learned that one cue predicts an outcome, it then fails to learn that a second cue added alongside it also predicts the outcome, because the earlier learning blocks the new learning. Leon Kamin's 1969 chapter Predictability, surprise, attention, and conditioning first reported and named this effect, and it became a central test for theories of learning. Waelti, Dickinson, and Schultz's 2001 study showed that dopamine signals in the brain track the effect as those theories predict. The referent is a limit on what a learner acquires, not an injection that stops a nerve, a grouping in an experiment, or a record in a ledger.[5][6]

Unit

One conditioning outcome, the learned response to the added cue

Recovery means

Not applicable

Measured by

Measured by weaker conditioned responding to the blocked cue in later tests