02150nas a2200193   4500008004100000022001400041245007100055210006900126260001200195300001400207490000700221520158500228653001601813100002101829700002001850700001901870700002001889856004701909       1986                        eng d  a0022-307700aAdaptive plasticity in primate spinal stretch reflex: persistence.0 aAdaptive plasticity in primate spinal stretch reflex persistence  c02/1986  a272–2790 v553 aMonkeys can gradually change the amplitude of the wholly segmental, largely monosynaptic, spinal stretch reflex (SSR) when confronted by a task requiring such change (15-19). Change develops over months and may reverse and redevelop at similarly slow rates. We investigated the persistence of SSR amplitude change over nonperformance periods of up to 38 days. Eight animals with chronic EMG electrodes learned to maintain elbow angle and a given level of biceps background EMG against constant extension torque. At random times, a brief additional extension torque pulse elicited the biceps SSR. In the control mode, reward always followed. Under the SSR increase or SSR decrease mode, reward occurred only if the absolute value of biceps EMG in the SSR interval was above or below a set value. Animals completed 3,000-6,000 trials/day over data-collection periods of 2-17 mo. Animals worked first under the control mode for up to 60 days and then under the SSR increase or SSR decrease mode for up to 274 days. Mode was switched once or twice more (SSR increase to SSR decrease or vice versa) over subsequent months. Animals responded to each SSR increase or SSR decrease mode exposure with gradual mode-appropriate change in SSR amplitude. Mode exposures were interrupted by gaps in performance of 10-38 days. Gaps produced transient 10- to 15% decreases in SSR amplitude under the control mode. This nonspecific decrease disappeared over the first week of postgap performance. Under the control mode, gaps had no other effects on SSR amplitude.(ABSTRACT TRUNCATED AT 250 WORDS)10aSpinal Cord1 aWolpaw, Jonathan1 aO'Keefe, J., A.1 aNoonan, P., A.1 aSanders, M., G.  uhttp://www.ncbi.nlm.nih.gov/pubmed/395069101682nas a2200181   4500008004100000022001400041245010400055210006900159260001200228300001600240490000700256520111400263653001601377100002101393700001901414700002001433856004701453       1983                        eng d  a0022-307700aAdaptive plasticity in primate spinal stretch reflex: behavior of synergist and antagonist muscles.0 aAdaptive plasticity in primate spinal stretch reflex behavior of  c12/1983  a1312–13190 v503 aMonkeys can gradually change the amplitude of the biceps spinal stretch reflex (SSR) without change in initial muscle length or biceps background electromyographic activity (EMG) (17). We investigated the concurrent behavior of synergist (brachialis and brachioradialis) and antagonist (triceps) muscles. Synergist background EMG remained stable while marked change occurred in biceps SSR amplitude. Triceps background EMG was minimal under all conditions. Thus biceps SSR amplitude change was not due to change in the background activity of closely related muscles. When biceps SSR amplitude changed, synergist SSR amplitude changed similarly but to a lesser extent. Brachialis change averaged 72% of biceps change, while brachioradialis change averaged 33%. By indicating that SSR amplitude change is relatively specific to the agonist muscle, this finding eliminates a number of nonspecific mechanisms as possible origins of SSR amplitude change. Thus it supports the potential value of the SSR as a system for studying the neuronal and synaptic bases of memory in the primate central nervous system (CNS).10aSpinal Cord1 aWolpaw, Jonathan1 aSeegal, R., F.1 aO'Keefe, J., A.  uhttp://www.ncbi.nlm.nih.gov/pubmed/6663328