Operant Conditioning of H-Reflex Can Correct a Locomotor Abnormality after Spinal Cord Injury in Rats — TEI-tagged view

Yi Chen, Xiang Yang Chen, Lyn B. Jakeman, Lu Chen, Bradford T. Stokes, Jonathan R. Wolpaw · 2006 · neuroscience · doi:10.1523/jneurosci.2198-06.2006 · full text at the source · TEI xml · tagged edition · index · concepts · authors
Where this record's text came from. faceted 2026-08 by reading the locally held text (html); every evidence string verified as an exact substring of that text before merging. method tagged 'electrophysiology' because the measurements are nerve-cuff-evoked H-reflexes and chronic EMG; the design is equally an animal behavioural/operant-conditioning experiment with a lesion manipulation, which the single-value facet cannot express. n is small (8 HRup, 5 control rats), and the paper reports this openly but does not frame it as a limitation, so it is not in limitations. Source is a PMC HTML dump: inline citations carry extra spaces inside the parentheses (e.g. '( Chen et al., 2005 )') and quotes preserve that spacing verbatim. Boilerplate .gov/PMC navigation text at the top of the file was ignored. 2026-08-13 and 2026-08-15 schema-0.3 passes: every quote verified as an exact substring of the staged text and anchored at merge time; concept terms verified present; every edge endpoint an existing node.
Other fields define these differently the same word, defined another way in another discipline
coefficient of variation 4 fields · standard deviation 3 fields
Tags on this paper every tag the record carries, whether or not the words occur in the text below — a number is how many papers in the corpus carry that tag; a tag with no number is unique to this paper
H-reflex3 operant conditioning4 spinal cord plasticity2 lateral column corticospinal tract2 locomotor asymmetry step-cycle symmetry2 soleus2 BBB score M-response background EMG3 stance phase electrophysiology110

Our tag layer for this paper

Cross-disciplinary analysis
content-tags & facets: phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text
phenomenonH-reflex operant conditioning after spinal cord injury— “This study asked whether operant conditioning of the H-reflex can modify locomotion in spinal cord-injured rats.”
claim-typeexistence— “In a first test of this possibility, the present study demonstrates that H-reflex conditioning can correct a physiologically defined locomotor abnormality caused by an anatomically defined spinal cord lesion in rats.”
method — evidence— “During locomotion, EMG was continuously recorded (0.1–1.0 kHz bandpass) from right and left soleus muscles, digitized (4.0 kHz), and stored.”
object of study — evidence— “This study asked whether operant conditioning of the H-reflex can modify locomotion in spinal cord-injured rats.”
research question — evidence— “The present study explores the possibility that appropriate descending input can also be used to improve the function of the injured spinal cord.”
contribution — evidence— “H-reflex up-conditioning increased the right soleus burst and corrected the locomotor asymmetry. In contrast, the locomotor asymmetry persisted in the control rats.”
transferfrom operant conditioning / behavioural psychology: reward-contingent shaping, applied to a spinal reflex rather than to a voluntary action— “The present study explores the possibility that appropriate descending input can also be used to improve the function of the injured spinal cord.”transfers[0]
transferfrom human rehabilitation studies: evidence that far fewer trials suffice in people, used to argue the rat protocol's intensity is not a barrier— “Furthermore, human data suggest that the thousands of trials per day obtained from rats are not essential and that conditioning can be achieved with three to five sessions per week of several hundred trials each”transfers[1]
mechanismUp-conditioning strengthens the motoneuron response to primary afferent input, recruiting more motoneurons into the locomotor burst (and making each fire more), which enlarges and broadens the soleus burst and thereby lengthens right stance until symmetry is restored— “The increases in burst amplitude and width are likely to reflect an increase in the number of motoneurons responding to this input.”mechanisms[0]
mechanismThe enlarged locomotor burst produced by up-conditioning is the proposed origin of the restored right/left symmetry— “The probable origin is the marked increase in locomotor burst amplitude that results from H-reflex up-conditioning (i.e., Fig. 2 ).”mechanisms[1]
mechanismIn normal animals compensatory adjustments by other muscles cancel the conditioning-induced change; in lesioned animals those compensatory adjustments are impaired or absent, so the conditioning effect is allowed to alter locomotion— “In contrast, when a locomotor asymmetry is already present before H-reflex conditioning, as it is in the LC rats of this study, the same automatic adjustments and the same impetus for adaptation to eliminate the impact of conditioning on locomotion are likely to be impaired or entirely absent.”mechanisms[2]
mechanismup-conditioning raises the locomotor burst, probably by recruiting more motoneurons to primary afferent input, and the burst also broadens— “On average, an increase in the stance H-reflex was accompanied by an increase 0.32 times as large in soleus burst amplitude ( r = 0.60; p = 0.04).”mechanisms[3]
mechanismthe lesion spares the corticospinal tract, which is the only descending path known to be essential for H-reflex conditioning - so the protocol can still work— “A one-vertebra dorsal laminectomy was performed at T8–T9, the cord was visualized with a dissection microscope, and the entire right LC (i.e., the lateral half of the right side of the cord) was transected by electrocautery. This procedure destroyed the rubrospinal, vestibulospinal, and reticulospinal tracts ( Tracey, 2004 ), but it left…mechanisms[4]
mechanismin intact animals other muscles compensate and symmetry is preserved; after injury that compensation is impaired, so the same conditioning changes locomotion— “In contrast, when a locomotor asymmetry is already present before H-reflex conditioning, as it is in the LC rats of this study, the same automatic adjustments and the same impetus for adaptation to eliminate the impact of conditioning on locomotion are likely to be impaired or entirely absent. Indeed, in LC rats, H-reflex up-conditioning is…mechanisms[5]
mechanismconditioning is delivered continuously in the home cage, 3000-9000 stimulus trials per day over 50 days— “As in the past, successful conditioning was defined as a change of ≥20% in the correct direction”mechanisms[6]
mechanismH-reflex size is expressed in units of background EMG rather than peak-to-peak, because the rat H-reflex form is too variable for a peak measure— “We measure H-reflex size in this manner because the typically high variability in the form of the rat H-reflex makes a simple peak-to-peak measure inappropriate.”mechanisms[7]
extends Chen et al., 2005 (H-reflex conditioning in normal rats)— “HRup conditioning increases locomotor H-reflexes and the ipsilateral soleus locomotor burst in normal rats ( Chen et al., 2005 ) just as it does in the LC rats of the present study.”claim_relations[0]
builds-on Chen et al., 2001a and Chen et al., 2005— “That these H-reflex and locomotor burst increases in the HRup rats were specific effects of the HRup protocol is indicated by a previous study ( Chen et al., 2001a ) showing the long-term stability of H-reflex size in unconditioned LC rats and a recent study ( Chen et al., 2005 ) showing that H-reflex up- and down-conditioning each has its…claim_relations[1]
extends work showing that patterned sensory input from locomotor training induces spinal plasticity, by adding a descending-input route— “The two sources of activity-dependent spinal cord plasticity are sensory inputs from the periphery and descending inputs from the brain.”claim_relations[2]
supports the feasibility of reflex conditioning in people with partial spinal cord injuries who retain a functioning CSTclaim_relations[3]
qualifies its own translational claim, by stating the rat-to-human locomotion question is undetermined
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claim_relations[4]
distinguishes-from the same conditioning in normal rats, where it does not change locomotor symmetry at all
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claim_relations[5]
senselocomotor abnormality here means an EMG burst-onset asymmetry, not an observed gait defect - the paper says whether there is a limp at all is unknown
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senses[0]
sensesuccessful conditioning is stipulated as a change of at least 20% in the intended direction, a criterion carried over from earlier papers
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senses[1]
sensethe abnormality is PHYSIOLOGICALLY defined and the lesion ANATOMICALLY defined - the paper states the two bases separately
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senses[2]
sensesymmetry is an index constructed so that 0.5 means symmetric, built from burst-onset times rather than from limb kinematics
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senses[3]
controlfive rats that were never exposed to up-conditioning, run through the same two sessions as the conditioned animals — held
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— rules out the passage of time and repeated testing as the explanation of the change - if the unconditioned rats changed too, the effect would not be the conditioning
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controls[0]
evidential statusits own translational claim, by stating the rat-to-human locomotion question is undetermined — the paper's own words: remains to be determined
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claim_relations[4]
differs inthe same conditioning in normal rats, where it does not change locomotor symmetry at all — THE AXIS IS WHETHER THE ANIMAL IS INJURED. 'In normal rats, however, neither HRup nor HRdown conditioning affects right/left symmetry: the time from RBO to LBO remains equal to the time from LBO to RBO, and it is not longer in normal HRup rats or shorter in normal HRdown rats.' The same conditioning does nothing in an intact animal and changes locomotion in an injured one - so the effect is a property of the DAMAGED system, and a therapy claim depends entirely on that.
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claim_relations[5]
noteH-reflex —causes→ locomotor asymmetry — SCOPE: this holds in lesioned rats and explicitly does NOT hold in normal rats, where the same conditioning leaves symmetry unchanged
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concept_edges[1]
weightH-reflex —causes→ locomotor asymmetry — 0.85
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concept_edges[1]
auditlateral column —distinct-from→ corticospinal tract — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the procedure transected the LC and left the CST intact; distinct-from is loose.
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concept_edges[2]
notelateral column —distinct-from→ corticospinal tract — the whole design rests on this separation - the lesion removes one and spares the other
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concept_edges[2]
auditlocomotor asymmetry —operationalised-as→ step-cycle symmetry — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span defines step-cycle symmetry; 'locomotor asymmetry' is not named.
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concept_edges[3]
auditEVIDENCE CORRECTED (RE-GROUNDED) · H-reflex —operationalised-as→ background EMG — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but endpoint by anaphora: 'in this manner' = measured relative to average background EMG amplitude (previous sentence).
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concept_edges[4]
noteEVIDENCE CORRECTED (RE-GROUNDED) · H-reflex —operationalised-as→ background EMG — the measurement unit was chosen because the animal's reflex form is too variable for the obvious measure
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concept_edges[4]
retractedEVIDENCE CORRECTED (RE-GROUNDED) · H-reflex —operationalised-as→ background EMG — RE-GROUNDED. The old span explained why the measure is used. This sentence IS THE OPERATIONALISATION, as a formula: '…and was expressed in units of average background EMG…'. The second endpoint appears twice - as the subtrahend and as the unit.
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concept_edges[4]
weightEVIDENCE CORRECTED (RE-GROUNDED) · H-reflex —operationalised-as→ background EMG — 0.9
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concept_edges[4]
auditH-reflex —operationalised-as→ background EMG — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but H-reflex size is expressed IN UNITS of background EMG; operationalised-as is loose.
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concept_edges[5]
noteH-reflex —operationalised-as→ background EMG — RE-GROUNDS another row of this record: the old span named ONE endpoint.
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concept_edges[5]
weightH-reflex —operationalised-as→ background EMG — 0.9
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concept_edges[5]
outcomecontrol — held
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controls[0]
for which uselimitation — what the study establishes, stated by the authors as principle only: THE PRESENT RESULTS MERELY VALIDATE THE PRINCIPLE THAT SPINAL REFLEX CONDITIONING CAN AFFECT A COMPLEX MOTOR FUNCTION AFTER SPINAL CORD INJURY
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limitations[0]
for which uselimitation — transfer to human walking: THE EXTENT TO WHICH THE EFFECTS OF CONDITIONING ON TREADMILL LOCOMOTION IN THE QUADRIPEDAL RAT PREDICT ITS EFFECTS ON OVER-GROUND LOCOMOTION IN THE BIPEDAL HUMAN REMAINS TO BE DETERMINED
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limitations[1]
for which uselimitation — any claim about how long the effect lasts: THE LONG-TERM PERSISTENCE OF THE EFFECTS OF H-REFLEX CONDITIONING IS NOT YET WELL DEFINED
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limitations[2]
for which uselimitation — between-group comparisons on absolute measures: THIS WIDE INTER-RAT VARIABILITY MEANS THAT VERY LARGE GROUPS OF LC AND NORMAL RATS WOULD BE NEEDED FOR INTERGROUP DIFFERENCES TO BECOME SIGNIFICANT
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limitations[3]
for which uselimitation — the step from the EMG measure to the behaviour: IT IS NOT AS YET CLEAR WHETHER THE SOLEUS EMG ASYMMETRY CREATED BY THE LC LESION IS ASSOCIATED WITH AN ACTUAL LIMP IN WALKING
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limitations[4]
for which uselimitation — the same scope as limitations[0] - the principle, not the clinical application: MUCH REMAINS TO BE LEARNED BEFORE THE POTENTIAL of the method is known
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limitations[5]
for which uselimitation — the soleus-burst proxy for stance and swing: THE DATA PRESENTED HERE RELY ON THE RIGHT AND LEFT SOLEUS LOCOMOTOR BURSTS TO ASSESS SPECIFIC ASPECTS OF LOCOMOTION, and these measures only APPEAR TO PARALLEL THE RIGHT AND LEFT STANCE PHASES OF LOCOMOTION
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limitations[6]
duplicate oflimitation — limitations[1]
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limitations[7]
for which uselimitation — the same scope as limitations[1] - prediction from quadrupedal treadmill work to BIPEDAL HUMAN over-ground locomotion
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limitations[7]
for which uselimitation — the same scope as limitations[2] - persistence, where the human comparison is that THE EFFECTS OF DOWN-CONDITIONING ARE STILL EVIDENT 4 MONTHS LATER
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limitations[8]
for which uselimitation — absolute measures specifically: ABSOLUTE MEASURES SUCH AS SOLEUS BURST AMPLITUDE DIFFER WIDELY ACROSS NORMAL RATS AND EVEN BETWEEN THE RIGHT AND LEFT LEGS OF INDIVIDUAL RATS
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limitations[9]
for which uselimitation — the up-conditioning locomotion analysis, which used only the animals in which conditioning worked: THE SEVEN SUCCESSFUL RATS CONSTITUTED THE EXPERIMENTAL GROUP OF HRup RATS FOR EVALUATION OF THE EFFECTS OF UP-CONDITIONING ON TREADMILL LOCOMOTION
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limitations[10]
for which uselimitation — any sex-general reading: SUBJECTS WERE 13 FEMALE SPRAGUE DAWLEY RATS
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limitations[11]
replicationuntested
limitationThe study only establishes the principle; the functional and clinical significance of the effect is not yet assessed.
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limitations[0]
limitationWhether treadmill results in quadrupedal rats transfer to over-ground walking in bipedal humans is unknown.
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limitations[1]
limitationHow long the conditioning effects last is not established.
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limitations[2]
limitationLarge between-rat variability in absolute EMG measures limits the power to detect group differences.
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limitations[3]
limitationthe measured asymmetry is an EMG proxy, and whether it corresponds to an actual limp is stated to be unknown
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limitations[4]
limitationthe results are said to merely validate a principle, with clinical significance unassessed
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limitations[5]
limitationonly soleus bursts were measured; stance and swing need direct measurement and other muscles are untested
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limitations[6]
limitationwhether quadrupedal treadmill results predict bipedal over-ground human locomotion is undetermined
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limitations[7]
limitationthe long-term persistence of the effect is not well defined, and up-conditioning decays faster than down-conditioning in monkeys
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limitations[8]
limitationinter-rat variability in absolute EMG measures is so wide that very large groups would be needed for group differences to reach significance
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limitations[9]
limitationthe locomotor analysis uses only the seven rats in which conditioning succeeded
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limitations[10]
limitation13 female rats only
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limitations[11]
Content tags
content-observations: finding · quantity · variable · definition · key-term — grounded in the full text
findingUp-conditioning the soleus H-reflex enlarged the right soleus burst and corrected the locomotor asymmetry.
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content_tags.findings[0]
findingRight lateral-column transection shortened the right stance phase: right-to-left burst-onset time was only 77% of left-to-right.
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content_tags.findings[1]
findingThe conditioning protocol roughly doubled the size of the conditioning H-reflex while leaving background EMG and the direct muscle (M) response unchanged, showing the change was reflex-specific rather than a general increase in muscle activation.
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content_tags.findings[2]
findingIn up-conditioned rats the locomotor H-reflexes and right soleus burst amplitude and width grew significantly between the first and second sessions.
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content_tags.findings[3]
findingStep-cycle duration did not change in either the up-conditioned or the control group.
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content_tags.findings[4]
findingIn normal rats neither up- nor down-conditioning affects right/left step symmetry.
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content_tags.findings[5]
findingUp-conditioning succeeded in 7 of 8 lesioned rats (87.5%).
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content_tags.findings[6]
findinglateral column transection left a persistent burst-onset asymmetry: right-to-left time was 0.43 of the cycle against 0.50 in normal rats
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content_tags.findings[7]
findingthe right stance phase was shortened to 77% of the opposite interval
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content_tags.findings[8]
findingup-conditioning succeeded in 7 of 8 rats
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content_tags.findings[9]
findinglocomotor H-reflexes and right soleus burst amplitude and width all increased in the conditioned group
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content_tags.findings[10]
findingthe asymmetry disappeared in the up-conditioned group
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content_tags.findings[11]
findinga stance H-reflex increase came with a burst amplitude increase 0.32 times as large
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content_tags.findings[12]
findingthe same conditioning does not change locomotor symmetry in normal rats
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content_tags.findings[13]
finding72% of the right lateral column was destroyed, with other structures mostly intact
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content_tags.findings[14]
quantity212 ± 49% — final size of the conditioning H-reflex in successfully up-conditioned rats, as a percentage of its pre-conditioning control size
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content_tags.quantities[0]
quantity87.5% — proportion of rats (7 of 8) in which up-conditioning met the success criterion
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content_tags.quantities[1]
quantity0.43 ± 0.02 — right-to-left burst-onset interval as a fraction of the whole step cycle in lesioned rats, versus the 0.50 of symmetrical locomotion
Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher.
content_tags.quantities[2]
quantity280 ± 38% — increase in the stance-phase locomotor H-reflex after up-conditioning, as a percentage of its first-session value
Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher.
content_tags.quantities[3]
quantity158 ± 22% — increase in right soleus locomotor burst amplitude after up-conditioning, as a percentage of its first-session value
Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher.
content_tags.quantities[4]
quantity72 ± 18% — proportion of the right lateral column destroyed by the transection, verified histologically
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content_tags.quantities[5]
quantityp = 0.008 — significance of the disappearance of the right/left step-cycle asymmetry in the up-conditioned group
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content_tags.quantities[6]
quantity13 — number of rats used in the study
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content_tags.quantities[7]
quantity13 female Sprague Dawley rats — the sample
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content_tags.quantities[8]
quantity10% of peak — the stipulated threshold defining burst onset and offset
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content_tags.quantities[9]
quantityat least 20% change — the stipulated criterion for successful conditioning
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content_tags.quantities[10]
quantity0.43 versus 0.50 of the step cycle, p = 0.009 — the lesion-induced asymmetry against normal
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content_tags.quantities[11]
quantity212% of control, 7 of 8 rats, 87.5% success — the conditioning effect and its success rate
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content_tags.quantities[12]
quantity0.32 times as large, r = 0.60, p = 0.04 — burst amplitude change per unit H-reflex change
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content_tags.quantities[13]
quantity72 plus or minus 18% of the right lateral column destroyed — verified lesion extent
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content_tags.quantities[14]
variableH-reflex up-conditioning (independent)
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content_tags.variables[0]
variablestep-cycle symmetry (dependent)
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content_tags.variables[1]
variabletreadmill speed (control)
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content_tags.variables[3]
variableM-response size (control)
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content_tags.variables[4]
variableH-reflex size
Quotation withheld — this paper is not ours to reproduce, and the page has already quoted as much of it as the rights layer allows. The tag, its field and its confidence stand; the sentence is at the publisher.
content_tags.variables[5]
variableburst amplitude
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content_tags.variables[8]
variableburst width
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content_tags.variables[9]
definitionconditioning H-reflex
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content_tags.definitions[0]
definitionstep-cycle symmetry
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content_tags.definitions[1]
definitionsuccessful conditioning
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content_tags.definitions[2]
definitionstep-cycle symmetry
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content_tags.definitions[5]
definitionsuccessful conditioning
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content_tags.definitions[6]
definitionburst onset
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content_tags.definitions[7]
definitionburst offset
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content_tags.definitions[8]
key-termsH-reflex, operant conditioning, spinal cord plasticity, spinal cord injury, lateral column, corticospinal tract, soleus, locomotion, treadmill, step cycle, asymmetry, BBB score, EMG, motoneuron, stance, up-conditioning, down-conditioning, rehabilitation, M-response, nerve cuff
Statistics — cross-field join keys
field-invariant statistical terms, used in their statistical sense (gated on a number / symbol / test). A p-value or a standard deviation means the SAME thing in physics, biology, psychology and sociology — so these are the strongest cross-field join keys. Grounded verbatim.
ANOVA as written: one-way repeated-measures ANOVA
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content_tags.statistics[0]
post hoc multiple comparison (Tukey's test) as written: pairwise multiple comparison (Tukey's test)
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content_tags.statistics[1]
t-test p
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content_tags.statistics[2]
correlation r as written: r = 0.60
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content_tags.statistics[3]
standard deviation SD as written: mean ± SD
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content_tags.statistics[4]
coefficient of variation
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content_tags.statistics[5]
one-way repeated-measures ANOVA with Tukey's test
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content_tags.statistics[6]
coefficient of variation across step cycles
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content_tags.statistics[7]
Second readings
a facet read a second time, independently, from its own sentence — and whether the two readings agree
claim typemechanism — a second reading DIFFERING from the recorded value; recorded: existence
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alternatives.claim_type
methodright lateral column transection, then 50 days of H-reflex up-conditioning by nerve-cuff stimulation and food reward in the freely moving rat, with treadmill locomotion measured before and after — a second reading DIFFERING from the recorded value; recorded: electrophysiology
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alternatives.method
phenomenonactivity-dependent spinal cord plasticity — a second reading DIFFERING from the recorded value; recorded: H-reflex operant conditioning after spinal cord injury
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alternatives.phenomenon

When we have changed our mind. Some entries in the table begin with a word in capitals and the reason for it. EVIDENCE CORRECTED — the finding still stands, but we had quoted the wrong sentence from the paper, and the quotation has been replaced with the right one. RETRACTED — the entry itself was wrong; it stays on the page, marked, with the reason, rather than being deleted. WITHDRAWN AND REPLACED — the entry was wrong, and a corrected version of it appears in the entries below. Each mark carries its own reason, in brackets, because the reasons differ from one entry to the next. An entry we have WITHDRAWN is removed from this page and kept in the record, with its reason. A line reading Audit and a date is a later re-reading of the entry against its whole sentence: DOUBTFUL means it was kept, and the reason says what is loose about it. Quotation marks inside the tagger's sentence. Where a tag is the tagger's own sentence, a phrase in quotation marks inside it is borrowed from the paper — the tagger's wording around it is not. The paper's own sentence is the evidence quote for that row; on this page it is withheld with the article, and the article is at its publisher. Nothing inside quotation marks anywhere on this page is ours: if it is quoted, it is the paper's. Whose words a concept carries. A concept entry records a term the paper itself uses, so the term, the sense given for it, and its evidence are the paper's own words, quoted where the paper fixes them. This is the opposite of a sense entry in the tag table, which is the tagger's sentence about how the paper uses a term. Where a concept entry could not be grounded in the paper's words, the entry says so on its own row.

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