Representation of stimulus azimuth by low-frequency neurons in inferior colliculus of the cat

1985 ◽  
Vol 53 (1) ◽  
pp. 43-59 ◽  
Author(s):  
L. M. Aitkin ◽  
J. D. Pettigrew ◽  
M. B. Calford ◽  
S. C. Phillips ◽  
L. Z. Wise
Keyword(s):  
Inferior Colliculus ◽  
Sound Source ◽  
Low Frequency ◽  
Stimulus Location ◽  
Small Sample ◽  
Half Width ◽  
Medial Side ◽  
Unit Classes ◽  
Contralateral Ear ◽  
The Relationship

The responses to changes in stimulus azimuth of 204 neurons in the inferior colliculus of the cat with best frequencies of less than 3 kHz were studied. Three main unit classes were identified: omnidirectional units uninfluenced by speaker azimuth (39%); multipeaked units with several azimuthal regions at which peak firing occurred (9%); and azimuth-selective units that showed clear preferences for a discrete range of sound-source azimuths (52%). Alterations in stimulus intensity produced little change in the shapes of profiles relating firing rate to stimulus azimuth (azimuth functions), but the peaks of these functions could shift by up to 20 degrees. Similar observations were made for a small sample of units, each of which was examined with a variety of stimulus frequencies. The pinnae were removed bilaterally in 11 cats, and azimuth functions for 35 units were measured both binaurally and with the ipsilateral or contralateral ear occluded. Evidence was found for facilitative or suppressive interactions, as a function of stimulus azimuth, between monaural inputs. The sharpness of an azimuth function was expressed by the half-width of the function, i.e., the number of degrees of azimuth between the peak of the function and the point at which 50% of maximum firing occurred on the medial side of the peak. When half-widths were plotted as a function of best frequency, it was found that the sharpest azimuth functions occurred for units with best frequencies between 1.1 and 1.5 kHz. Most units in the lowest two octaves (0.1-0.4 kHz) or having best frequencies between 2 and 3 kHz were omnidirectional. The relationship between half-width and the azimuth at which peak firing occurred (best azimuth) revealed that a range of best azimuths between 10 and 40 degrees contralateral contained the sharpest azimuth functions. When best frequency was plotted against best azimuth, it was observed that the majority of units (93%) had best azimuths in the contralateral hemifield. For frequencies between 0.7 and 1.7 kHz, best azimuths occurred relatively evenly between 10 and 60 degrees contralateral. These data suggested that for frequencies between 1.2 and 1.4 kHz, at least, the best azimuths of different units with the same best frequency collectively provide information about stimulus location across much of the contralateral hemifield.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Sound Source Localization by Hearing Preservation Patients with and without Symmetrical Low-Frequency Acoustic Hearing

2015 ◽  
Vol 20 (3) ◽  
pp. 166-171 ◽  
Author(s):  
Louise H. Loiselle ◽  
Michael F. Dorman ◽  
William A. Yost ◽  
René H. Gifford
Keyword(s):  
Source Localization ◽  
Sound Source ◽  
Low Frequency ◽  
Hearing Preservation ◽  
Sound Source Localization ◽  
Localization Accuracy ◽  
Acoustic Hearing ◽  
Low Pass ◽  
Contralateral Ear ◽  
High Pass

The aim of this article was to study sound source localization by cochlear implant (CI) listeners with low-frequency (LF) acoustic hearing in both the operated ear and in the contralateral ear. Eight CI listeners had symmetrical LF acoustic hearing and 4 had asymmetrical LF acoustic hearing. The effects of two variables were assessed: (i) the symmetry of the LF thresholds in the two ears and (ii) the presence/absence of bilateral acoustic amplification. Stimuli consisted of low-pass, high-pass, and wideband noise bursts presented in the frontal horizontal plane. Localization accuracy was 23° of error for the symmetrical listeners and 76° of error for the asymmetrical listeners. The presence of a unilateral CI used in conjunction with bilateral LF acoustic hearing does not impair sound source localization accuracy, but amplification for acoustic hearing can be detrimental to sound source localization accuracy.

scholarly journals Spatial tuning to sound-source azimuth in the inferior colliculus of unanesthetized rabbit

2011 ◽  
Vol 106 (5) ◽  
pp. 2698-2708 ◽  
Author(s):  
Shigeyuki Kuwada ◽  
Brian Bishop ◽  
Caitlin Alex ◽  
Daniel W. Condit ◽  
Duck O. Kim
Keyword(s):  
Inferior Colliculus ◽  
Sound Source ◽  
Neural Coding ◽  
Full Range ◽  
Sound Field ◽  
Stimulus Level ◽  
Unanesthetized Rabbit ◽  
Binaural Stimulation ◽  
Wide Range ◽  
Contralateral Ear

Despite decades of research devoted to the study of inferior colliculus (IC) neurons' tuning to sound-source azimuth, there remain many unanswered questions because no previous study has examined azimuth tuning over a full range of 360° azimuths at a wide range of stimulus levels in an unanesthetized preparation. Furthermore, a comparison of azimuth tuning to binaural and contralateral ear stimulation over ranges of full azimuths and widely varying stimulus levels has not previously been reported. To fill this void, we have conducted a study of azimuth tuning in the IC of the unanesthetized rabbit over a 300° range of azimuths at stimulus levels of 10–50 dB above neural threshold to both binaural and contralateral ear stimulation using virtual auditory space stimuli. This study provides systematic evidence for neural coding of azimuth. We found the following: 1) level-tolerant azimuth tuning was observed in the top 35% regarding vector strength and in the top 15% regarding vector angle of IC neurons; 2) preserved azimuth tuning to binaural stimulation at high stimulus levels was created as a consequence of binaural facilitation in the contralateral sound field and binaural suppression in the ipsilateral sound field; 3) the direction of azimuth tuning to binaural stimulation was primarily in the contralateral sound field, and its center shifted laterally toward −90° with increasing stimulus level; 4) at 10 dB, azimuth tuning to binaural and contralateral stimulation was similar, indicating that it was mediated by monaural mechanisms; and 5) at higher stimulus levels, azimuth tuning to contralateral ear stimulation was severely degraded. These findings form a foundation for understanding neural mechanisms of localizing sound-source azimuth.

Practical High Resolution Microscopy

1968 ◽  
Vol 26 ◽  
pp. 302-303
Author(s):  
P. A. Marsh ◽  
T. Mullens ◽  
D. Price
Keyword(s):  
High Resolution ◽  
Magnetic Fields ◽  
Low Frequency ◽  
Resolving Power ◽  
Careful Attention ◽  
Electron Microscopes ◽  
The Relationship ◽  
High Resolution Microscopy ◽  
New Facilities

It is possible to exceed the guaranteed resolution on most electron microscopes by careful attention to microscope parameters essential for high resolution work. While our experience is related to a Philips EM-200, we hope that some of these comments will apply to all electron microscopes.The first considerations are vibration and magnetic fields. These are usually measured at the pre-installation survey and must be within specifications. It has been our experience, however, that these factors can be greatly influenced by the new facilities and therefore must be rechecked after the installation is completed. The relationship between the resolving power of an EM-200 and the maximum tolerable low frequency interference fields in milli-Oerstedt is 10 Å - 1.9, 8 Å - 1.4, 6 Å - 0.8.

scholarly journals Slithering CSF: Cerebrospinal Fluid Dynamics in the Stationary and Moving Viper Boa, Candoia aspera

Biology ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 672
Author(s):  
Bruce A. Young ◽  
Skye Greer ◽  
Michael Cramberg
Keyword(s):  
Cerebrospinal Fluid ◽  
Cardiac Cycle ◽  
Low Frequency ◽  
Mean Amplitude ◽  
The Body ◽  
Body Waves ◽  
Lower Amplitude ◽  
Lateral Undulation ◽  
Recovery From Anesthesia ◽  
The Relationship

In the viper boa (Candoia aspera), the cerebrospinal fluid (CSF) shows two stable overlapping patterns of pulsations: low-frequency (0.08 Hz) pulses with a mean amplitude of 4.1 mmHg that correspond to the ventilatory cycle, and higher-frequency (0.66 Hz) pulses with a mean amplitude of 1.2 mmHg that correspond to the cardiac cycle. Manual oscillations of anesthetized C. aspera induced propagating sinusoidal body waves. These waves resulted in a different pattern of CSF pulsations with frequencies corresponding to the displacement frequency of the body and with amplitudes greater than those of the cardiac or ventilatory cycles. After recovery from anesthesia, the snakes moved independently using lateral undulation and concertina locomotion. The episodes of lateral undulation produced similar influences on the CSF pressure as were observed during the manual oscillations, though the induced CSF pulsations were of lower amplitude during lateral undulation. No impact on the CSF was found while C. aspera was performing concertina locomotion. The relationship between the propagation of the body and the CSF pulsations suggests that the body movements produce an impulse on the spinal CSF.

When do job insecure employees adapt to change?

2019 ◽  
Vol 25 (3) ◽  
pp. 271-286 ◽  
Author(s):  
Kristi N. Lavigne ◽  
Victoria L. Whitaker ◽  
Dustin K. Jundt ◽  
Mindy K. Shoss
Keyword(s):  
Job Insecurity ◽  
Small Sample ◽  
Adaptive Performance ◽  
Work Behaviors ◽  
Content Type ◽  
Work Tasks ◽  
Main Effect ◽  
Low Levels ◽  
The Impact ◽  
The Relationship

Purpose The purpose of this paper is to examine the relationship between job insecurity and adaptive performance (AP), contingent on changes to core work tasks, which we position as a situational cue to employees regarding important work behaviors. Design/methodology/approach Employees and their supervisors were invited to participate in the study. Supervisors were asked to provide ratings of employees’ AP and changes to core tasks; employees reported on job insecurity. Findings As predicted, changes to core tasks moderated the relationship between job insecurity and AP. Job insecurity was negatively related to AP for those experiencing low levels of change, but was not related to AP for those experiencing high levels of change. Counter to expectations, no main effect of job insecurity was found. Research limitations/implications This study employed a fairly small sample of workers from two organizations, which could limit generalizability. Practical implications The study identifies changes to core tasks as a boundary condition for the job insecurity–AP relationship. Findings suggest that organizations may not observe deleterious consequences of job insecurity on AP when changes to core tasks are high. Originality/value Few researchers have examined boundary conditions of the impact of job insecurity on AP. Furthermore, inconsistent findings regarding the link between job insecurity and AP have emerged. This study fills the gap and expands upon previous research by examining changes to core tasks as a condition under which job insecurity does not pose an issue for AP.

Improving new product development performance by risk management

2016 ◽  
Vol 31 (3) ◽  
pp. 418-425 ◽  
Author(s):  
Mehran Salavati ◽  
Milad Tuyserkani ◽  
Seyyede Anahita Mousavi ◽  
Nafiseh Falahi ◽  
Farshid Abdi
Keyword(s):  
Risk Management ◽  
Product Development ◽  
New Product Development ◽  
Small Sample Size ◽  
New Product ◽  
Small Sample ◽  
Content Type ◽  
Total Performance ◽  
The Relationship ◽  
Npd Performance

Purpose The principal aim of this study is to investigate the relationship between technological, marketing, organizational and commercialization risk management on new product development (NPD) performance. Design/methodology/approach Based on questionnaire, the data were collected from a sample of general automotive industry in Iran. Based on theoretical considerations, a model was proposed and descriptive statistic and hierarchical regression were used to measure the relationship between risk management factors and NPD performance. Findings Data analysis revealed that if organization can amplify their knowledge and information about risk and main factors that affect NPD process, not only can they do their work better but can also increase their ability to predict future happenings that affect performance. Research limitations/implications First, due to the relatively small sample size, caution should be exercised when interpreting the results. Second, the data were collected from automotive producer in Iran, which may restrict to some extent generalizability of the findings. Practical implications The results suggest that managers should consider more attention to risk management. If managers spread the risk management in all aspects of the NPD project, total performance will be increased and it can develop the probability of NPD success. Also organizations should perform great market research due to best commercialization. Originality/value Past researches have presented complete information about NPD process. But identifying and considering the effect of the risk management parameters that are connected to the NPD process were the main thrusts to perform the study. In this paper, based on past research about risk management of NPD, the extra aspect of process that can improve total performance of NPD has been examined.

Overconfidence of vocational education students when entering higher education

2015 ◽  
Vol 57 (4) ◽  
pp. 429-447 ◽  
Author(s):  
Mark P. Bowden ◽  
Subhash Abhayawansa ◽  
John Bahtsevanoglou
Keyword(s):  
Higher Education ◽  
Self Efficacy ◽  
Further Education ◽  
Small Sample ◽  
First Year ◽  
Education Students ◽  
Content Type ◽  
The Relationship ◽  
Practical Implications

Purpose – There is evidence that students who attend Technical and Further Education (TAFE) prior to entering higher education underperform in their first year of study. The purpose of this paper is to examine the role of self-efficacy in understanding the performance of students who completed TAFE in the previous year in a first year subject of microeconomics in a dual sector university in Melbourne, Australia. Design/methodology/approach – The study utilises data collected by surveys of 151 students. Findings – A student’s self-efficacy is positively associated with their marks in a first year subject of microeconomics. However, the relationship between final marks and self-efficacy is negative for those students who attended TAFE in the previous year suggesting that they suffer from the problem of overconfidence. When holding self-efficacy constant, using econometric techniques, TAFE attendance is found to be positively related to final marks. Research limitations/implications – The findings are exploratory (based on a small sample) and lead to a need to conduct cross institutional studies. Practical implications – The research points to the need for early interventions so that TAFE students perform well in their first year of higher education. It also points to potential issues in the development of Victorian Certificate of Applied Learning (VCAL) programs. Originality/value – To the best of the authors’ knowledge, this is the first paper to examine the inter-related impact of attendance at TAFE in the previous year and self-efficacy on the subsequent academic performance of TAFE students.

Sign in / Sign up

Export Citation Format

Share Document