Single motor unit activity in extraocular muscles in man during fixation and saccades

Sindermann, F; B, Geiselmann; Fischler, M.

doi:10.1016/0013-4694(78)90342-5

Cited by 29 publications

(16 citation statements)

References 11 publications

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“…Although there are no studies detailing jaw muscle SMU activity during standardized isotonic tasks, there have been in other motor systems. For example, a linear change in SMU firing rates has been observed in the human medial or lateral rectus muscles during stepwise horizontal eye movements (Sindermann et al 1978). Also, motoneurons in the inferior rectus muscle in monkeys exhibited progressive increases in firing rates during stepwise saccades in one direction (Henn and Cohen 1972).…”

Section: Discussionmentioning

confidence: 99%

Functional Properties of Single Motor Units in the Inferior Head of Human Lateral Pterygoid Muscle: Task Firing Rates

Phanachet

Whittle

Wanigaratne

et al. 2002

Journal of Neurophysiology

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The precise function of the inferior head of the human lateral pterygoid muscle (IHLP) is unclear. The aim of this study was to clarify the normal function of the IHLP. The hypothesis was that an important function of the IHLP is the generation and fine control of horizontal (i.e., anteroposterior and mediolateral) jaw movements. The activities of 50 single motor units (SMUs) were recorded from IHLP (14 subjects) during two- or three-step contralateral movement (n = 36) and/or protrusion (n = 33). Most recording sites were identified by computer tomography. There was a statistically significant overall increase in firing rate as the magnitude of jaw displacement increased between the holding phases (range of increments: 0.3-1.6 mm). The firing rates during the dynamic phases for each unit were significantly greater than those during the previous holding phases but less than those during the subsequent holding phases. For the contralateral step task at the intermediate rate, the cross-correlation coefficients between jaw displacement in the mediolateral axis and the mean firing rate of each unit ranged from r = 0.29 to 0.77; mean +/- SD; r = 0.49 +/- 0.13 (protrusive step task: r = 0.12-0.74, r = 0.44 +/- 0.14 for correlation with anterior-posterior axis). The correlation coefficients at the fast rate during the contralateral step task and the protrusive step task were significantly higher than those at the slow rate. The firing rate change of the SMUs per unit displacement between holding phases was significantly greater for the lower-threshold than for the higher-threshold units during contralateral movement and protrusion. After dividing IHLP into four regions, the SMUs recorded in the superior part exhibited significantly greater mean firing rate changes per unit displacement during protrusion than for the SMUs recorded in the inferior part. Significantly fewer units were related to the protrusive task in the superior-medial part. These data support previously proposed notions of functional heterogeneity within IHLP. The present findings provide further evidence for an involvement of the IHLP in the generation and fine control of horizontal jaw movements.

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Section: Discussionmentioning

confidence: 99%

Functional Properties of Single Motor Units in the Inferior Head of Human Lateral Pterygoid Muscle: Task Firing Rates

Phanachet

Whittle

Wanigaratne

et al. 2002

Journal of Neurophysiology

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“…According to this model, the power spectrum of ocular drift and tremor can be approximated by two processes: a Poisson process filtered by a second-order eye plant transfer f unction over the frequency range 0 -40 Hz where the power declines as 1/f 2 , and a cyclo-stationary process that produces a broad spectral peak in the range of 40 -100 Hz. The two terms represent the irregular discharge rate of motor units for frequency Ͻ40 Hz and their more regular firing pattern for higher frequencies, respectively (Kuboki, 1957;Sindermann et al, 1978). For simplicity, given its predominant contribution, only the first term with power spectrum proportional to 1/f 2 was considered.…”

Section: Modeling Eye Movementsmentioning

confidence: 99%

Modeling LGN Responses during Free-Viewing: A Possible Role of Microscopic Eye Movements in the Refinement of Cortical Orientation Selectivity

2000

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Neural activity appears to be essential for the normal development of the orientation-selective responses of cortical cells. It has been proposed that the correlated activity of LGN cells is a crucial component for shaping the receptive fields of cortical simple cells into adjacent, oriented subregions alternately receiving ON- and OFF-center excitatory geniculate inputs. After eye opening, the spatiotemporal structure of neural activity in the early stages of the visual pathway depends not only on the characteristics of the environment, but also on the way the environment is scanned. In this study, we use computational modeling to investigate how eye movements might affect the refinement of orientation tuning in the presence of a Hebbian scheme of synaptic plasticity. Visual input consisting of natural scenes scanned by varying types of eye movements was used to activate a spatiotemporal model of LGN cells. In the presence of different types of movement, significantly different patterns of activity were found in the LGN. Specific patterns of correlation required for the development of segregated cortical receptive field subregions were observed in the case of micromovements, but were not seen in the case of saccades or static presentation of natural visual input. These results suggest an important role for the eye movements occurring during fixation in the refinement of orientation selectivity.

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“…After a rectangular driving pulse (no switches), the next simplest bang-bang control signal has one switch, where the driving signal is switched from its maximum agonist value to its maximum antagonist value at some optimal switching time to brake the movement. Small "braking pulses" at the end of saccades have been observed in abducens motoneuron discharges (Van Gisbergen et al, 1981) and in muscle fibers (Sindermann et al, 1978), but the magnitude of these braking pulses are far less than the peak antagonist activity. There is no evidence of two or more switches during saccades, so we conclude that saccades are not driven by any kind of bang-bang control.…”

Section: Explanatory Models Of the Neural Pulsementioning

confidence: 99%

The Spectral Main Sequence of Human Saccades

1999

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Despite the many models of saccadic eye movements, little attention has been paid to the shape of saccade trajectories. Some investigators have argued that saccades are driven by a rectangular "bang-bang" neural control signal, whereas others have emphasized the similarity to fast arm movement trajectories, such as the "minimum jerk" profile. However, models have not been tested rigorously against empirical trajectories. We examined the Fourier transforms of saccades and compared them with theoretical models. Horizontal saccades were recorded from 10 healthy subjects. The Fourier transform of each saccade was accurately computed using a padded fast Fourier transform (FFT), and the frequencies of the first three minima (M1, M2, M3) in each energy spectrum were measured to a precision of 0.12 Hz. Each subject showed near-linear trends in the relationships among M1, M2, and M3 and the reciprocal of duration (1/T), which we call the "spectral main sequence." Extrapolation of plots did not pass through the origin, indicating a subtle departure from self-similarity. Bivariate confidence regions were established to allow for slope-intercept variability. The nonharmonic relationships seen cannot arise from a rectangular saccadic pulse driving a linear ocular plant. The relationships are also incompatible with minimum acceleration, minimum jerk, or higher-order minimum square derivative trajectories. The best fits were made by trajectories that minimize postmovement variance with signal-dependent noise (). It is concluded that the spectral main sequence is exquisitely sensitive to the saccade trajectory and should be used to test objectively all present and future models of saccades.

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Single motor unit activity in extraocular muscles in man during fixation and saccades

Cited by 29 publications

References 11 publications

Functional Properties of Single Motor Units in the Inferior Head of Human Lateral Pterygoid Muscle: Task Firing Rates

Functional Properties of Single Motor Units in the Inferior Head of Human Lateral Pterygoid Muscle: Task Firing Rates

Modeling LGN Responses during Free-Viewing: A Possible Role of Microscopic Eye Movements in the Refinement of Cortical Orientation Selectivity

The Spectral Main Sequence of Human Saccades

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