Test Tone Research Articles

Extinction reveals that primary sensory cortex predicts reinforcement outcome

Primary sensory cortices are traditionally regarded as stimulus analysers. However, studies of associative learning-induced plasticity in the primary auditory cortex (A1) indicate involvement in learning, memory and other cognitive processes. For example, the area of representation of a tone becomes larger for stronger auditory memories and the magnitude of area gain is proportional to the degree that a tone becomes behaviorally important. Here, we used extinction to investigate whether 'behavioral importance' specifically reflects a sound's ability to predict reinforcement (reward or punishment) vs. to predict any significant change in the meaning of a sound. If the former, then extinction should reverse area gains as the signal no longer predicts reinforcement. Rats (n = 11) were trained to bar-press to a signal tone (5.0 kHz) for water-rewards, to induce signal-specific area gains in A1. After subsequent withdrawal of reward, A1 was mapped to determine representational areas. Signal-specific area gains, estimated from a previously established brain-behavior quantitative function, were reversed, supporting the 'reinforcement prediction' hypothesis. Area loss was specific to the signal tone vs. test tones, further indicating that withdrawal of reinforcement, rather than unreinforced tone presentation per se, was responsible for area loss. Importantly, the amount of area loss was correlated with the amount of extinction (r = 0.82, P < 0.01). These findings show that primary sensory cortical representation can encode behavioral importance as a signal's value to predict reinforcement, and that the number of cells tuned to a stimulus can dictate its ability to command behavior.

Development of a computer-based automated pure tone hearing screening device: a preliminary clinical trial.

Hearing screening is important for the early detection of hearing loss. The requirements of specialized equipment, skilled personnel, and quiet environments for valid screening results limit its application in schools and health clinics. This study aimed to develop an automated hearing screening kit (auto-kit) with the capability of realtime noise level monitoring to ensure that the screening is performed in an environment that conforms to the standard. The auto-kit consists of a laptop, a 24-bit resolution sound card, headphones, a microphone, and a graphical user interface, which is calibrated according to the American National Standards Institute S3.6-2004 standard. The auto-kit can present four test tones (500, 1000, 2000, and 4000 Hz) at 25 or 40 dB HL screening cut-off level. The clinical results at 40 dB HL screening cut-off level showed that the auto-kit has a sensitivity of 92.5% and a specificity of 75.0%. Because the 500 Hz test tone is not included in the standard hearing screening procedure, it can be excluded from the auto-kit test procedure. The exclusion of 500 Hz test tone improved the specificity of the auto-kit from 75.0% to 92.3%, which suggests that the auto-kit could be a valid hearing screening device. In conclusion, the auto-kit may be a valuable hearing screening tool, especially in countries where resources are limited.

The influence of the type of breastfeeding on middle ear conditions in infants

Infants should be submitted to hearing screening upon birth, and for the results to be complete, it is necessary to assess middle ear conditions. ObjectiveTo check whether the type of breastfeeding in infants between zero and four months can impact middle ear conditions my means an ENT assessment and acoustic immittance comparing neonates who were submitted to hearing screening with those who failed it. Materials and MethodsOtoacoustic emissions (OAE) was carried out in 60 infants between zero and four months. They were distributed in two groups; group I had the infants with OAE and those infants in group II did not have OAE. They were submitted to tympanometry with a 1000 Hz test tone and ENT assessment. ResultsBottle fed infants or those who were fed in a mixed way had more changes to their audiometry and ENT assessment, with a statistically significant difference. The breastfed infants had a higher occasion of normal tympanometries and normal otorhinolaryngological assessment, with statistically significant difference. ConclusionWe then concluded that those breastfed implants had less ENT changes and as well as less acoustic immittance change, thus enabling OAEs. Breastfeeding alone can be considered a protection factor against middle ear changes.

Estimation of Intermodulation Rejection Value as a Function of Frequency in Power Amplifier Using AM-AM and AM-PM Diagrams Based on Power Series Analysis

A method to predict intermodulation (IM) products of two tone test based on Amplitude to amplitude (AM-AM) and amplitude to phase (AM-PM) diagrams of power amplifier is proposed in this paper. An RF power amplifier is mathe-matically modeled by a power series in order of 13. Coefficients of the transfer function are obtained by odd-order polynomial fitting of the transfer function of the power amplifier that is modeled by power series, with AM-AM and AM-PM diagrams. Because of considering AM-PM distortion, coefficients have become complex. By using this transfer function, analytical expressions of IM products are derived. Frequency effect of IM products are modeled in suggested method to estimate the effects of changing in input frequency on output. With the mean of this factor the model is able to predict IM products of wideband frequency input. Simulated results agree well with the predicted method in comparisons.

A comparison of the effectiveness of predictors of caudal block in children-swoosh test, anal sphincter tone, and heart rate response

Objective:To study the effectiveness of three predictors of successful caudal block in children, viz. swoosh test, heart rate response to injection, and laxity of anal sphincter tone.Aim:To improve the success rates of caudal block in children by identifying the best predictor.Background:Caudal blocks in children are placed after induction of anesthesia. Although simple to learn and perform, the success rate of the blocks may be variable especially in teaching hospitals where trainee anesthetists perform these blocks.Materials and Methods:223 patients, aged 2–12 years, undergoing lower abdominal and urologic surgery were studied. 0.25% Bupivacaine was administered after induction of general anesthesia according to the Armitage regimen.Results:The sensitivity and specificity were highest with the sphincter tone test (sensitivity 95.22%, specificity 92.86%), followed by the heart rate response (sensitivity 92.82%, specificity 78.57%) and the swoosh test (sensitivity 66.51%, specificity 35.71%). The anal sphincter tone test had the highest positive predictive value (99.5%) and positive likelihood ratio (13.33). The heart rate response had a positive predictive value of 98.48% and a positive likelihood ratio of 4.33. The swoosh test, in our study, had a positive predictive value of 93.92% and a positive likelihood ratio of 1.035.Conclusion:The anal sphincter tone test was the best predictor of successful caudal block. We recommend the use of these additional simple predictors of accurate needle placement to increase the success rate of caudal block especially in teaching hospitals.

Comparison of noninvasive evaluation of endolymphatic hydrops in Meniere's disease and endolymphatic space in healthy volunteers using magnetic resonance imaging

Conclusions: The comparison of noninvasive standard evaluation of endolymphatic hydrops in Meniere's disease and the endolymphatic space in healthy volunteers using magnetic resonance imaging (MRI) evaluation should be carried out first. Objective: To compare the standard evaluation of endolymphatic hydrops in Meniere's disease and the endolymphatic space in healthy volunteers in the cochlea and the vestibule in the same age group by applying noninvasive intratympanic gadolinium (Gd) perfusion through the eustachian tube and three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). Methods: This was a prospective study. 3D-FLAIR MRI was performed with a 3 Tesla (3 T) unit 24 h after intratympanic administration of Gd through the eustachian tube in 6 patients with medically active and intractable Meniere's disease and 20 healthy volunteers. Pure tone test and tympanometry were performed 24 h before Gd was administered, and 24 h and 1 month after Gd administration. Results: Gd was present in the perilymph of the inner ear, which clearly displayed the endolymphatic space on 3D-FLAIR MRI with a visible borderline between the perilymph and the endolymph. In 45–55-year-old healthy volunteers, the normal value for the endolymphatic space in the cochlea ranged between 8% and 26%, and that in the vestibule was between 20% and 41%. According to the normal value for the endolymphatic space, four of six patients had a ratio of more than 26% in the cochlea; moreover, four of six patients had a ratio of more than 41% in the vestibule. All the patients had a ratio of more than the normal value in the cochlea and/or the vestibule. No significant changes in pure tone test and tympanometry were noted.

Circulating angiogenic cell populations, vascular function, and arterial stiffness

ObjectiveSeveral bone marrow-derived cell populations have been identified that may possess angiogenic activity and contribute to vascular homeostasis in experimental studies. We examined the extent to which lower quantities of these circulating angiogenic cell phenotypes may be related to impaired vascular function and greater arterial stiffness. MethodsWe studied 1948 Framingham Heart Study participants (mean age, 66±9 years; 54% women) who were phenotyped for circulating angiogenic cells: CD34+, CD34+/KDR+, and early outgrowth colony forming units (CFU). Participants underwent non-invasive assessments of vascular function including peripheral arterial tone (PAT), arterial tonometry, and brachial reactivity testing. ResultsIn unadjusted analyses, higher CD34+ and CD34+/KDR+ concentrations were modestly associated with lower PAT ratio (β=−0.052±0.011, P<0.001 and β=−0.030±0.011, P=0.008, respectively) and with higher carotid-brachial pulse wave velocity (β=0.144±0.043, P=0.001 and β=0.112±0.043, P=0.009), but not with flow-mediated dilation; higher CD34+ was also associated with lower carotid-femoral pulse wave velocity (β=−0.229±0.094, P=0.015). However, only the association of lower CD34+ concentration with higher PAT ratio persisted in multivariable analyses that adjusted for standard cardiovascular risk factors. In all analyses, CFU was not associated with measures of vascular function or arterial stiffness. ConclusionsIn our large, community-based sample of men and women, circulating angiogenic cell phenotypes largely were not associated with measures of vascular function or arterial stiffness in analyses adjusting for traditional risk factors.

Clinical feature analysis on 217 patients with subjective tinnitus

Objective To analysis the clinical feature and audiology feature of patients with subjective tinnitus,compare masking,screening effectiveness of various kinds tinnitus,and search for the individual treatment ways for subjective tinnitus.Methods 217 patients in our hospistor were performed pure tone test,DPOAE,tinnitus determination,and tinnitus masking including pitch matching,intensity matching,Feldmann masking curve,and residual inhibition test with TinniTestTM.Results The prevalence rate is higher in female (52％).Tinnitts occur to the left side more common (42％),followed by bilateral ears (30％) and the right side (28％).The urban population ( 77％ ) and mental worker ( 68％ ) were primary in patients.The patients with chronic tinnitus (duration＞ 1 year) counts for most proportion (46％).The most effective treatment was masking treatment for cases with high frequency tinnitus and low frequency tinnitus; the effective power is 71.6％ and 73.6％.The lowest effective treatment was masking treatment for cases with middle frequency tinnitus; the effective power is only 52.2％.The positive ratio of masking test for cases with type Ⅰ to type Ⅴ (Feldman Curve Type) decreased from 90％ to 10％ gradually.Conclusions The feature of cases with tinnitus had much more dependence on masking test and tinnitus frequency; it could be predictive factor for curative effect of tinnitus.Feldman curve type has large utilization value and directed significance on diagnosis and treatment for tinnitus.It is much more valuable for the selection of masking therapy; and is an important predicted factor for the effectiveness of masking therapy;and it is an important evidence for the selection of personal treatment. Key words: Subjective tinnitus; Tinnitus feature; Feldman curve; Tinnitus masking

Is There Audio-Tactile Interaction in Perceptual Organization?

Sounds often accompany tactile stimulation. The present study investigated if the temporal coherent auditory and tactile stimuli can be grouped together to form a perceptual stream. The experiments measured listeners' sensitivity to detect synchrony between a pair of auditory or tactile stimuli (in a 2I-2AFC task), either in isolation or embedded in a sequence of stimuli in the same modality (ie, ‘captors’) that was designed to perceptually ‘capture’ the target stimulus into a sequential stream. In some conditions, the captors were presented together with stimuli from the same or different modality. Results show that these accompanying tones did improve auditory synchrony detection when the captors were presented, but the accompanying taps did not, no matter whether the test tone pairs were separated by 6 or 11 semitones. On the other hand, the accompanying tones did not improve tactile synchrony detection when the captors were presented, no matter whether the test tap pairs were on the same hand or different hands. The observations did not find significant audio-tactile interactions in streaming at or below the level of synchrony detection across auditory filters and across hands. Nevertheless, the interactions may occur at higher-level processing of perceptual organization.

Performance enhancement of 10 Gb/s direct modulation optical OFDM by external optical injection

We show experimentally and by simulation a performance enhancement of a directly modulated 10 Gb/s optical Orthogonal Frequency Division Multiplexing (OFDM) system due to external optical injection. The experiment is performed back to back and over 12 km of single mode fiber. The injection extends the range of linear operation of the laser and therefore extends the usable bandwidth for direct modulation formats which are susceptible to nonlinearity, such as OFDM. Nonlinearity in the system and its reduction due to injection are estimated by means of a two tone test. Additionally the performance enhancement on OFDM systems was verified in both simulation and experimentally by the comparisons of the average Bit Error Rate (BER) and Error Vector Magnitude (EVM).

No temporal binding of action consequences to actions in a rhythmic context

Temporal binding (TB) refers to a subjective contraction of the time that elapses between an action and a delayed sensory consequence of it. The TB effect has been demonstrated primarily in tasks in which a key press triggers a tone after a short delay and in which participants judge the timing of one or both of these events relative to a visual reference (e.g., a rotating clock hand). In the present Experiments 1 and 2, musicians listened instead to an auditory "clock" (a metronome) and occasionally made a tap that triggered a delayed tone. The task was to judge whether that test tone fell before, on, or after the midpoint of the interval between two metronome tones. In a passive control condition, participants judged test tones but did not tap. The hypothesis was that the test tone would be perceived as occurring earlier in the active than in the passive condition. However, there was no difference in perceptual judgments. Experiment 3 used a visual metronome as the reference but again obtained negative results, despite greater uncertainty of judgments. It is suggested that TB of action consequences to actions does not occur when the reference signal is rhythmic because such a context enables participants (musicians, at least) to perceive and judge the actual time of occurrence of the action-triggered tone.

P2-281 Prevalence of hearing loss in HIV-infected Brazilian children and adolescents

IntroductionChildren and adolescents living with HIV/AIDS may suffer from a variety of hearing problems which are more frequent and sometimes more severe when compared to other children. The objective of...

The evaluation of Teucrium persicum methanolic extract and its fractions in Pavlovian Fear Conditioning

In this research, the effects of total methanolic extract and related fractions (chloroform, ethyl acetate, aqueous) of Teucrium persicum Boiss. on conditional memory were evaluated. The methanolic extract of T. persicum aerial parts and related fractions were administrated orally in doses of 100mg/kg, 300mg/kg, 400mg/kg every 24 hours for 10 days to male rats. 24 hours later animals were trained in Pavlovian Fear Conditioning. Training consists of 5 tone (30s, 2.3 k Hz, 80 Db)-shock(2s, 1 mA) pairings. Fear to the context and the tone were evaluated by measuring freezing in separate tests. The results showed that chloroform fraction of the methanolic extract had a positive effect on fear conditioning. According to positive effects of chloroform fraction on fear conditioning, possible cholinergic properties of the chloroform fraction (consisting of terpenes) was tested by inducing conditional memory via scopolamine (a non-selective cholinergic antagonist) before training. It was found that the chloroform fraction had a protective effect against cholinergic disruption. All the doses had more freezing duration(s) compared to control group and there was a significant difference between 400mg/kg and control group (P value<0.01 for contest test, P value<0.05 for tone test). It is concluded that chloroform fraction of T. persicum has a memory enhancing effect according to cholinergic properties of the component.

Efectos de la toxina botulínica tipo A y electroestimulación en la espasticidad flexora distal de la extremidad superior en el ictus. Ensayo clínico aleatorizado

Objective To evaluate the efficacy of the Neuromuscular Electrical Stimulation (NMES) associated to Botulinum Toxin (TB) type A in motor function, functional capacity and spasticity in chronic post-stroke upper limb (UL) spasticity. Patients and methods A randomized controlled clinical trial was performed in 25 ictus patients with more than 6 months evolution. After infiltration of 200 units of TB in the flexor muscle of the finger and wrist muscles, the patients were assigned to two groups: NMES in extensor muscles (group 1) and sham-stimulation (group 2). Patients were assessed at weeks 4/16 post-injection by standard motor function scales (Fugl-Meyer Motor Assessment (FMA), Medical Research Council Scale (MRC), Motricity Index for Motor Impairment after stroke and dynamometry), UL functional capacity (Chedoke Arm and Hand Activity Inventory (CAHAI), Box and Block Test (BBT) and muscular tone (Modified Ashworth Scale (MAS)). Results At week 4, significant improvement was observed in FMA 2.4 (SD 4.1) in UL component, MRC 0.2 (SD 0.4), CAHAI 4.2 and BBT 1.5 (SD 3.3), as well as a reduction in MAS 1.0 (SD 0.9) in the wrist and 1.2 (SD 1.4) in the fingers. At month 4, this effect was maintained in motor function but not in spasticity. No significant differences were observed in UL motor function, functional capacity between the groups. Conclusions TB type A injection in UL distal flexor spasticity enhances motor function, functional capacity and spasticity in chronic stroke patients. Adding a program of NMES for the extensor wrist/fingers muscles does not provide any additional benefits.

Abnormal cervical vestibular-evoked myogenic potential in anterior inferior cerebellar artery territory infarction: Frequency, pattern, and a determinant

BackgroundThere has been no systematic study that carefully investigates the characteristic features of abnormal cervical vestibular-evoked myogenic potential (cVEMP) response associated with the AICA territory infarction. ObjectivesTo investigate the frequency, the characteristic patterns of abnormal cVEMP associated with AICA territory infarction, and the crucial site for producing abnormal cVEMP response in the AICA territory infarction. MethodsWe studied 16 consecutive cases of unilateral AICA territory infarction diagnosed by brain MRI. VEMP was induced by a short click sound and was recorded in contracting sternocleidomastoid muscle. Each patient underwent a quantitative audiovestibular evaluation, including bithermal caloric test and pure tone audiogram. ResultsEight patients (50%) exhibited abnormal cVEMP response on the side of the AICA territory infarction. All patients with abnormal cVEMP showed an absent or decreased response in amplitude but no difference in latency. Patients with abnormal VEMP were significantly more likely to have canal paresis (CP), sensorineural hearing loss, or both compared with patients who had normal cVEMP. Conversely, abnormal cVEMP was more frequently observed among patients with CP than among those without CP. There was no difference in lesion sites according to brain MRI among patients with or without abnormal cVEMP response. ConclusionsOur findings suggest that the peripheral vestibular structure with the inner ear probably plays a crucial role in producing abnormal cVEMP response associated with AICA territory infarction.

Die aktuell gefasste Leitlinie „Hörsturz” (Akuter idiopathischer sensorineuraler Hörverlust)

The new revised version (expires 2012) for sudden, unilateral, sensorineural hearing loss stresses the urgence but not the emergency of diagnostics and therapy in this inner ear disfunction with still increasing incidence. Minimum diagnostics should comprise ENT examination with earmicroscopy, pure tone and tuning fork hearing tests, tympano- and vestibulometry. Classification by frequency loss seems of interest in regard to different underlying pathology, which is still obscure. Therefore from experience glucocorticoids and rheological therapy are recommended in the light of some favoring recent studies. The intratympanic appliCation of glucokorticoids is considered as spare therapy.

Measuring spectral and temporal resolution simultaneously: A comparison between two tests

Objective: Spectral- and temporal-resolution tests are seldom used in clinical practice despite their proven relevance for patients' speech understanding in noise and expected importance for hearing-aid fitting. The aim here was to investigate and compare two clinically applicable tests (‘tone test’ and ‘sweep test’) that measure both spectral and temporal resolution simultaneously. Design: Experiments were conducted monaurally via headphones. After examining test-retest reliabilities and learning effects we compared results from tone and sweep tests to results from conventional spectral and temporal-resolution tests and to speech perception in noise scores. Study Sample: A group of five normal-hearing listeners (aged 18–42 years, median 19) and 15 (sensorineurally) hearing-impaired listeners (aged 20–68 years, median 56). Results: It was found that the tone test corresponded much better to the conventional methods than the sweep test. Relating spectral and temporal-resolution results to speech perception in noise scores showed that the tone test seems to be slightly more relevant for speech perception than the sweep test. Conclusions: It can be concluded that the tone test (after modifications we suggest, based on our findings) is a fast and reliable test that is suitable for measuring spectral and temporal resolution in a clinical setting.SumarioObjetivo: Pocas veces se utilizan las pruebas espectrales y de resolución temporal en la práctica clínica a pesar de su probada relevancia en el reconocimiento del lenguaje en ruido y la expectativa de su importancia en la adaptación de auxiliares auditivos. El objetivo aquí fue investigar y comparar dos pruebas aplicables en la clínica (“prueba de tono” y “prueba de barrido”) que mide la resolución espectral y la temporal simultáneamente. Diseño: Los experimentos realizados fueron monoaurales por medio de auriculares. Después de examinar la confiabilidad test-retest y el efecto aprendizaje, comparamos los resultados de las pruebas de tono y de barrido con los resultados de las pruebas convencionales de resolución temporal y espectral y con los resultados de la percepción del lenguaje en ruido. Muestra: Un grupo de cinco sujetos normoyentes (edad 18-42, media 19) y cinco sujetos con hipoacusia sensorineural (edad 20-68 años, media 56). Resultados: Encontramos que la prueba de tono corresponde mucho mejor con los métodos convencionales que con la prueba de barrido. Con respecto a los resultados de la resolución temporal y espectral de la percepción del lenguaje en ruido, los resultados mostraron que la prueba de tono parece ser un poco más relevante para la percepción del lenguaje que la prueba de barrido. Conclusiones: En conclusión se puede concluir que la prueba de tono (después de modificaciones que sugerimos basados en nuestros hallazgos) es una prueba rápida, confiable y es apropiada para medir la resolución espectral y temporal en la clínica.

Loudness matching for enhanced sinusoids.

When a target sound is masked by a notched masker, thresholds can be lower when a preview of the masker precedes the detection interval. Two experiments were run to determine whether signals “enhanced” by such precursors are also louder. Trials included three intervals. On each trial a random, multi-tone masker was chosen, and presented in each interval. For the loudness matching task, a 1000-Hz target tone was added to the second and third intervals; the level of the test tone in the second interval was adjusted to match the loudness of the standard tone in the third interval. For a standard tone 3–8 dB above threshold, the test tone was adjusted to be approximately 5 dB less intense than the standard, indicating a difference in loudness. For more intense standard levels, this difference decreased. In the second experiment, thresholds for the detection of a tone added to the second or third interval were estimated. Thresholds were approximately 10 dB lower for the second than the third interval. These results indicate that stimuli that induce enhancement (i.e., threshold difference between intervals 2 and 3) also induce increases in loudness, suggesting a role of subjective amplification of the signal for enhancement.

Functional electrical stimulation combined with botulinum toxin type A to improve hand function in children with spastic hemiparesis – a pilot study

Children with spastic hemiparesis frequently present with impaired hand function due to paresis, spasticity, and disturbed motor control. The aim of this study was to examine the effectiveness of functional electrical stimulation in combination with botulinum toxin type A in these children. Randomized, controlled, observer-blinded pilot study. Children with impaired hand function. Either a combined treatment group (functional electrical stimulation and botulinum toxin type A) or a botulinum toxin type A group alone. Botulinum toxin type A was injected into arm muscles according to the patient's clinical requirements. Functional electrical stimulation of the wrist and finger extensor muscles was started after five to six days. Patients were given a stimulation device and asked to use it at home twice daily for 15 min, for a total period of three months. Active and passive range of motion, muscle tone, muscle strength, and functional tests for children. Six children aged between 7 and 17 years with spastic hemiparesis were enrolled. In both groups, active and passive range of motion, muscle tone, and muscle strength improved after three and six months compared to baseline data. The functional score was improved only in the group that received combined treatment. Combined treatment with functional electrical stimulation and botulinum toxin type A is a promising treatment option to improve upper limb function in children with spastic hemiparesis.

Sacral neurophysiologic study in patients with chronic spinal cord injury

Neurophysiologic testing of the sacral reflex has demonstrated utility in the diagnosis of sacral lower motor neuron lesions. The aim of the present study was to also apply this test to patients with upper motor neuron lesions. A group of 16 male patients with chronic suprasacral spinal cord lesions was prospectively recruited. In addition to history and clinical neurologic examination (including anal sphincter tone, saddle sensation, and penilo-cavernosus reflex testing), sacral neurophysiologic studies were performed. Neurophysiologic testing included quantitative electromyography of the external anal sphincter (motor unit potential (MUP) count during relaxation and MUP analysis), and neurophysiologic measurement of the penilo-cavernosus reflex (elicitation threshold and latency) on electrical stimulation. The findings were compared to data obtained in the control group of 26 men. Clinical elicitability of the penilo-cavernosus reflex was increased, and the neurophysiologically measured reflex threshold reduced in patients (<0.02). No significant differences were found in clinical assessment of anal sphincter tone, MUP count, reflex latency, and quantitative MUP analysis. The diagnostic sensitivity of individual parameters was low (≤25%). In patients with chronic spinal cord injury, increased elicitability of the penilo-cavernosus reflex was found. However, none of the assessed neurophysiologic parameters was found to assist in the diagnosis of the sacral upper motor neuron lesion in individual patients. The shortened sacral reflex latency found in individual patients is therefore not a consequence of a suprasegmental lesion, but rather of the low position of the conus medullaris (e.g., in tethered cord syndrome).