scholarly journals INPUT-OUTPUT RELATION IN A FLEXOR REFLEX

1957 ◽  
Vol 41 (2) ◽  
pp. 297-306 ◽  
Author(s):  
David P. C. Lloyd
Keyword(s):  
Spinal Cord ◽  
Afferent Input ◽  
Surprising Result ◽  
Input Output ◽  
Flexor Reflex ◽  
Afferent Fibers ◽  
Closed Chain ◽  
Central Paths ◽  
Reflex Threshold ◽  
Reflex Discharge

Observations have been made upon a typical flexor reflex with the aim of disclosing the changes in amount, latency, and temporal configuration of reflex discharge that take place as afferent input is varied from zero to maximal for the band of cutaneous myelinated afferent fibers that extends upward from approximately 6 µ in diameter (group II fibers). Reflex threshold is reached at 6 to 12 per cent maximal afferent input. From threshold to maximal input the relation between input and amount of output is essentially linear, latency on the average decreases, the shorter central paths in general gain preference, but the known minimum pathway, one of three neurons, does not transmit unless aided by convergent activity. Flexor reflex discharge may occur in several bursts suggesting the existence of closed chain connections in the internuncial pools of the spinal cord. At any given input there is, in successively elicited reflexes, little correlation between latency and amount of discharge, at first sight a surprising result for each variable can be taken as a measure of excitability status of the motoneuron population. However, latency of discharge indicates excitability at the beginning of the reflex event whereas amount of discharge is an expression of excitability over the entire period of discharge. Given a constantly and rapidly fluctuating excitability absence of correlation between these variables would be an anticipated result.

Segmental organization of visceral and somatic input onto C3-T6 spinothalamic tract cells of the monkey

1992 ◽  
Vol 68 (5) ◽  
pp. 1575-1588 ◽  
Author(s):  
S. F. Hobbs ◽  
M. J. Chandler ◽  
D. C. Bolser ◽  
R. D. Foreman
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Urinary Bladder ◽  
Visceral Pain ◽  
Cell Activity ◽  
Afferent Input ◽  
Spinothalamic Tract ◽  
Afferent Fibers ◽  
Increased Activity ◽  
Stimulation Of

1. Referred pain of visceral origin has three major characteristics: visceral pain is referred to somatic areas that are innervated from the same spinal segments as the diseased organ; visceral pain is referred to proximal body regions and not to distal body areas; and visceral pain is felt as deep pain and not as cutaneous pain. The neurophysiological basis for these phenomena is poorly understood. The purpose of this study was to examine the organization of viscerosomatic response characteristics of spinothalamic tract (STT) neurons in the rostral spinal cord. Interactions were determined among the following: 1) segmental location, 2) effects of input by cardiopulmonary sympathetic, greater splanchnic, lumbar sympathetic, and urinary bladder afferent fibers, 3) location of excitatory somatic field, e.g., hand, forearm, proximal arm, or chest, 4) magnitude of response to hair, skin, and deep mechanoreceptor afferent input, and 5) regional specificity of thalamic projection sites. 2. A total of 89 STT neurons in segments C3-T6 were characterized for responses to visceral and somatic stimuli. Neurons were activated antidromically from the contralateral ventroposterolateral oralis or caudalis nuclei of the thalamus. Cell responses to visceral and somatic stimuli were not different on the basis of the thalamic site of antidromic activation. Recording sites for 61 neurons were located histologically; 87% of lesion sites were located in laminae IV-VII or X. There was no relationship between response properties of the neurons and spinal laminar location. 3. Different responses to visceral stimuli were observed in three zones of the rostral spinal cord: C3-C6, C7-C8, and T1-T6. In C3-C6, urinary bladder distension (UBD) and electrical stimulation of greater splanchnic and lumbar sympathetic afferent fibers inhibited STT cells. Electrical stimulation of cardiopulmonary sympathetic afferents increased cell activity in C5 and C6 and either excited or inhibited STT cells in C3 and C4. In the cervical enlargement (C7-C8), STT cells generally were either inhibited or showed little response to stimulation of visceral afferent fibers. In T1-T6, input from greater splanchnic and cardiopulmonary sympathetic afferent nerves increased activity of STT cells. Lumbar sympathetic afferent input inhibited cells in T1-T2 and had little effect on cells in T3-T6, whereas UBD decreased cell activity in all segments studied. 4. In general, stimulation of somatic structures increased activity of STT neurons in segments that received primary afferent innervation from the excitatory somatic receptive field or in the segments immediately adjacent to these segments. Only input from the forelimb, especially the hand, markedly excited cells in C7 and C8.+

Role of Aδ afferent fibers in modulation of primary afferent input to the adult rat spinal cord

1995 ◽  
Vol 691 (1-2) ◽  
pp. 92-98 ◽  
Author(s):  
T. Shimizu ◽  
M. Yoshimura ◽  
H. Baba ◽  
K. Shimoji ◽  
H. Higashi
Keyword(s):  
Spinal Cord ◽  
Afferent Input ◽  
Rat Spinal Cord ◽  
Primary Afferent ◽  
Adult Rat ◽  
Afferent Fibers ◽  
Adult Rat Spinal Cord

Operant conditioning to increase ankle control or decrease reflex excitability improves reflex modulation and walking function in chronic spinal cord injury

2013 ◽  
Vol 109 (11) ◽  
pp. 2666-2679 ◽  
Author(s):  
Kathleen J. Manella ◽  
Kathryn E. Roach ◽  
Edelle C. Field-Fote
Keyword(s):  
Spinal Cord ◽  
Operant Conditioning ◽  
Walking Ability ◽  
Ankle Clonus ◽  
Flexor Reflex ◽  
Reflex Pathways ◽  
Active Range Of Motion ◽  
Cord Injury ◽  
Reflex Threshold ◽  
Foot Clearance

Ankle clonus is common after spinal cord injury (SCI) and is attributed to loss of supraspinally mediated inhibition of soleus stretch reflexes and maladaptive reorganization of spinal reflex pathways. The maladaptive reorganization underlying ankle clonus is associated with other abnormalities, such as coactivation and reciprocal facilitation of tibialis anterior (TA) and soleus (SOL), which contribute to impaired walking ability in individuals with motor-incomplete SCI. Operant conditioning can increase muscle activation and decrease stretch reflexes in individuals with SCI. We compared two operant conditioning-based interventions in individuals with ankle clonus and impaired walking ability due to SCI. Training included either voluntary TA activation (TA↑) to enhance supraspinal drive or SOL H-reflex suppression (SOL↓) to modulate reflex pathways at the spinal cord level. We measured clonus duration, plantar flexor reflex threshold angle, timed toe tapping, dorsiflexion (DF) active range of motion, lower extremity motor scores (LEMS), walking foot clearance, speed and distance, SOL H-reflex amplitude modulation as an index of reciprocal inhibition, presynaptic inhibition, low-frequency depression, and SOL-to-TA clonus coactivation ratio. TA↑ decreased plantar flexor reflex threshold angle (−4.33°) and DF active range-of-motion angle (−4.32°) and increased LEMS of DF (+0.8 points), total LEMS of the training leg (+2.2 points), and nontraining leg (+0.8 points), and increased walking foot clearance (+ 4.8 mm) and distance (+12.09 m). SOL↓ decreased SOL-to-TA coactivation ratio (−0.21), increased nontraining leg LEMS (+1.8 points), walking speed (+0.02 m/s), and distance (+6.25 m). In sum, we found increased voluntary control associated with TA↑ outcomes and decreased reflex excitability associated with SOL↓ outcomes.

scholarly journals Galanin-receptor ligand M40 peptide distinguishes between putative galanin-receptor subtypes

1993 ◽  
Vol 90 (23) ◽  
pp. 11287-11291 ◽  
Author(s):  
T Bartfai ◽  
U Langel ◽  
K Bedecs ◽  
S Andell ◽  
T Land ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Binding Sites ◽  
Receptor Subtype ◽  
Receptor Subtypes ◽  
Galanin Receptor ◽  
Flexor Reflex ◽  
Receptor Ligand ◽  
Insulinoma Cells ◽  
Galanin Receptors

The galanin-receptor ligand M40 [galanin-(1-12)-Pro3-(Ala-Leu)2-Ala amide] binds with high affinity to [mono[125I]iodo-Tyr26]galanin-binding sites in hippocampal, hypothalamic, and spinal cord membranes and in membranes from Rin m5F rat insulinoma cells (IC50 = 3-15 nM). Receptor autoradiographic studies show that M40 (1 microM) displaces [mono[125I]iodo-Tyr26]galanin from binding sites in the hippocampus, hypothalamus, and spinal cord. In the brain, M40 acts as a potent galanin-receptor antagonist: M40, in doses comparable to that of galanin, antagonizes the stimulatory effects of galanin on feeding, and it blocks the galaninergic inhibition of the scopolamine-induced acetylcholine release in the ventral hippocampus in vivo. In contrast, M40 completely fails to antagonize both the galanin-mediated inhibition of the glucose-induced insulin release in isolated mouse pancreatic islets and the inhibitory effects of galanin on the forskolin-stimulated accumulation of 3',5'-cAMP in Rin m5F cells; instead M40 is a weak agonist at the galanin receptors in these two systems. M40 acts as a weak antagonist of galanin in the spinal flexor reflex model. These results suggest that at least two subtypes of the galanin receptor may exist. Hypothalamic and hippocampal galanin receptors represent a putative central galanin-receptor subtype (GL-1-receptor) that is blocked by M40. The pancreatic galanin receptor may represent another subtype (GL-2-receptor) that recognizes M40, but as a weak agonist. The galanin receptors in the spinal cord occupy an intermediate position between these two putative subtypes.

Gating of Afferent Input by a Central Pattern Generator

1999 ◽  
Vol 81 (2) ◽  
pp. 950-953 ◽  
Author(s):  
Ralph A. DiCaprio
Keyword(s):  
Central Pattern Generator ◽  
Sensory Input ◽  
Motor Pattern ◽  
Pattern Generator ◽  
Afferent Input ◽  
Inhibitory Input ◽  
Cycle Period ◽  
Intracellular Recordings ◽  
Afferent Fibers ◽  
Sufficient Magnitude

Gating of afferent input by a central pattern generator. Intracellular recordings from the sole proprioceptor (the oval organ) in the crab ventilatory system show that the nonspiking afferent fibers from this organ receive a cyclic hyperpolarizing inhibition in phase with the ventilatory motor pattern. Although depolarizing and hyperpolarizing current pulses injected into a single afferent will reset the ventilatory motor pattern, the inhibitory input is of sufficient magnitude to block afferent input to the ventilatory central pattern generator (CPG) for ∼50% of the cycle period. It is proposed that this inhibitory input serves to gate sensory input to the ventilatory CPG to provide an unambiguous input to the ventilatory CPG.

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