@article {3284,
	title = {Adaptive plasticity in primate spinal stretch reflex: persistence.},
	journal = {Journal of neurophysiology},
	volume = {55},
	year = {1986},
	month = {02/1986},
	pages = {272{\textendash}279},
	abstract = {Monkeys 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)},
	keywords = {Spinal Cord},
	issn = {0022-3077},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/3950691},
	author = {Jonathan Wolpaw and O{\textquoteright}Keefe, J. A. and Noonan, P. A. and Sanders, M. G.}
}
@article {3286,
	title = {Reduced day-to-day variation accompanies adaptive plasticity in the primate spinal stretch reflex.},
	journal = {Neuroscience letters},
	volume = {54},
	year = {1985},
	month = {03/1985},
	pages = {165{\textendash}171},
	abstract = {Monkeys can change the amplitude of the spinal stretch reflex (SSR), or M1, when reward is made contingent on amplitude. The present study demonstrates that reduced SSR day-to-day variation accompanies such adaptive SSR change. This finding supports the assumption that initial, phase I, SSR change results from contingency-appropriate stabilization of tonic activity in relevant descending spinal cord pathways.},
	keywords = {Learning, Memory, plasticity, primate, spinal reflex, stretch reflex},
	issn = {0304-3940},
	doi = {10.1016/S0304-3940(85)80073-2},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/3991057},
	author = {Jonathan Wolpaw and O{\textquoteright}Keefe, J. A. and Kieffer, V. A. and Sanders, M. G.}
}
@article {3288,
	title = {Adaptive plasticity and diurnal rhythm in the primate spinal stretch reflex are independent phenomena.},
	journal = {Brain research},
	volume = {300},
	year = {1984},
	month = {05/1984},
	pages = {385{\textendash}391},
	abstract = {Recent studies have revealed two phenomena producing considerable variation in amplitude of the initial, purely segmental, largely monosynaptic, response to sudden muscle stretch, the spinal stretch reflex (SSR), without change in background EMG activity or initial muscle length. The first is small and short-term, a modest diurnal rhythm in SSR amplitude. The second is large and long-term, marked adaptive change in SSR amplitude which occurs gradually over weeks and months when animals are rewarded for such change. This second phenomenon may involve persistent segmental alteration, and, if so, could constitute a technically accessible substrate of memory. The present study compared the two phenomena and sought evidence of interaction between them. The diurnal rhythm persisted, without change in phase and with only minimal change in amplitude, despite the occurrence of marked adaptive change. Animals did not utilize the rhythm to increase reward percentage by altering daily performance schedules. These results suggest that the mechanisms of the diurnal rhythm and of adaptive plasticity in SSR amplitude are separate and independent. The diurnal rhythm{\textquoteright}s effect on movement was not altered by adaptive change in SSR amplitude. This effect was comparable to adaptive change{\textquoteright}s effect on movement when both were expressed as change in movement/change in SSR amplitude.},
	keywords = {adaptive plasticity, diurnal rhythm, Learning, Memory, primate, stretch reflex},
	issn = {0006-8993},
	doi = {10.1016/0006-8993(84)90852-7},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/6539634},
	author = {Jonathan Wolpaw and Noonan, P. A. and O{\textquoteright}Keefe, J. A.}
}
@article {3287,
	title = {Adaptive plasticity in the primate spinal stretch reflex: evidence for a two-phase process.},
	journal = {The Journal of neuroscience : the official journal of the Society for Neuroscience},
	volume = {4},
	year = {1984},
	month = {11/1984},
	pages = {2718{\textendash}2724},
	abstract = {Monkeys can slowly increase or decrease the amplitude of the purely spinal, largely monosynaptic portion of the response to sudden muscle stretch, the spinal stretch reflex (SSR), when confronted by a task requiring such change (Wolpaw, J.R., V.A. Kieffer, R.F. Seegal, D.J. Braitman, and M.G. Sanders (1983) Brain Res. 267: 196-200; Wolpaw, J.R., D.J. Braitman, and R.F. Seegal (1983) J. Neurophysiol. 50: 1296-1311). Change occurs without alteration in initial muscle length or in background activity of agonist, antagonist, or synergist muscles. This study uses composite curves to describe in detail the development of SSR amplitude change. It reveals important, previously unexpected features of this development. SSR increase or decrease appears to occur in two distinct phases. Phase I, a nearly immediate 8\% change, occurs within the first 6 hr. Phase II, a 2\%/day change, continues for at least 2 months. Although phase II is much slower than phase I, its final magnitude is far greater. Phase I indicates a nearly immediate change in suprasegmental influence of the segmental arc of the SSR. Because stretch onset time is unpredictable and the SSR occurs before any other possible response, this change in descending activity must be tonic; it must be present continually, day after day, for the 5 to 7 hr/day the animal spends at the task. Phase I produces a rapid and significant increase in reward probability. Thus, it may be readily interpreted as an example of operant conditioning, provoked by the reward contingency.(ABSTRACT TRUNCATED AT 250 WORDS)},
	keywords = {Time Factors},
	issn = {0270-6474},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/6502200},
	author = {Jonathan Wolpaw and O{\textquoteright}Keefe, J. A.}
}
@article {3290,
	title = {Adaptive plasticity in primate spinal stretch reflex: behavior of synergist and antagonist muscles.},
	journal = {Journal of neurophysiology},
	volume = {50},
	year = {1983},
	month = {12/1983},
	pages = {1312{\textendash}1319},
	abstract = {Monkeys 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).},
	keywords = {Spinal Cord},
	issn = {0022-3077},
	url = {http://www.ncbi.nlm.nih.gov/pubmed/6663328},
	author = {Jonathan Wolpaw and Seegal, R. F. and O{\textquoteright}Keefe, J. A.}
}
