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Smooth pursuit-related information processing in frontal eye field neurons that project to the NRTP.

Ono S, Mustari MJ - Cereb. Cortex (2008)

Bottom Line: In contrast, FEF neurons not activated following ES of rNRTP were often most sensitive to eye velocity.In similar modeling studies, we found that rNRTP neurons were also biased toward eye acceleration.Therefore, our results suggest that neurons in the FEF-rNRTP pathway carry signals that could play a primary role in initiation of SP.

View Article: PubMed Central - PubMed

Affiliation: Division of Sensory-Motor Systems, Yerkes National Primate Research Center, and Department of Neurology, Emory University, 954 Gatewood Road Northeast, Atlanta, GA 30329, USA.

ABSTRACT
The cortical pursuit system begins the process of transforming visual signals into commands for smooth pursuit (SP) eye movements. The frontal eye field (FEF), located in the fundus of arcuate sulcus, is known to play a role in SP and gaze pursuit movements. This role is supported, at least in part, by FEF projections to the rostral nucleus reticularis tegmenti pontis (rNRTP), which in turn projects heavily to the cerebellar vermis. However, the functional characteristics of SP-related FEF neurons that project to rNRTP have never been described. Therefore, we used microelectrical stimulation (ES) to deliver single pulses (50-200 microA, 200-micros duration) in rNRTP to antidromically activate FEF neurons. We estimated the eye or retinal error motion sensitivity (position, velocity, and acceleration) of FEF neurons during SP using multiple linear regression modeling. FEF neurons that projected to rNRTP were most sensitive to eye acceleration. In contrast, FEF neurons not activated following ES of rNRTP were often most sensitive to eye velocity. In similar modeling studies, we found that rNRTP neurons were also biased toward eye acceleration. Therefore, our results suggest that neurons in the FEF-rNRTP pathway carry signals that could play a primary role in initiation of SP.

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SP and visual sensitivity of FEF neurons. (A) Example of FEF neuron tested during step-ramp pursuit with target blink. Response continues during the blink, indicating extraretinal sensitivity. (B) Representative neuronal response of FEF neuron during sinusoidal SP tracking at 0.5 Hz ± 10° and visual stimulation with a large-field, constant speed random dot pattern (0.5 Hz ± 10°). This SP-related neuron also showed a visual response at short latency (∼65 ms) following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in activated and nonactivated FEF neurons. Isolation was lost on some SP neurons before visual testing during fixation (SP+?).
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fig3: SP and visual sensitivity of FEF neurons. (A) Example of FEF neuron tested during step-ramp pursuit with target blink. Response continues during the blink, indicating extraretinal sensitivity. (B) Representative neuronal response of FEF neuron during sinusoidal SP tracking at 0.5 Hz ± 10° and visual stimulation with a large-field, constant speed random dot pattern (0.5 Hz ± 10°). This SP-related neuron also showed a visual response at short latency (∼65 ms) following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in activated and nonactivated FEF neurons. Isolation was lost on some SP neurons before visual testing during fixation (SP+?).

Mentions: FEF neurons evince sensitivity to eye and visual motion per se (Fig. 3). Figure 3A shows an example of a FEF neuron tested during SP where the target was briefly extinguished to reveal extraretinal sensitivity, as reported by other investigators (Tanaka and Fukushima 1998). Figure 3B shows a representative FEF neuron tested during sinusoidal SP and during fixation with visual stimulation. In this testing, either a small target spot (Fig. 3B, left) or a large-field visual stimulus (Fig. 3B, right) was moved in a direction and speed like that used during SP eye movements. These types of visual stimuli produced direction-selective modulation of neuronal firing (see Discussion). In Figure 3C, we show the distribution of FEF neurons in our sample with sensitivity to both eye motion and large-field visual motion. At least 60% of our antidromically activated FEF neurons had explicit visual and eye motion sensitivity. These results argue for inclusion of eye and retinal image motion parameters in our modeling studies (see Discussion).


Smooth pursuit-related information processing in frontal eye field neurons that project to the NRTP.

Ono S, Mustari MJ - Cereb. Cortex (2008)

SP and visual sensitivity of FEF neurons. (A) Example of FEF neuron tested during step-ramp pursuit with target blink. Response continues during the blink, indicating extraretinal sensitivity. (B) Representative neuronal response of FEF neuron during sinusoidal SP tracking at 0.5 Hz ± 10° and visual stimulation with a large-field, constant speed random dot pattern (0.5 Hz ± 10°). This SP-related neuron also showed a visual response at short latency (∼65 ms) following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in activated and nonactivated FEF neurons. Isolation was lost on some SP neurons before visual testing during fixation (SP+?).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2665162&req=5

fig3: SP and visual sensitivity of FEF neurons. (A) Example of FEF neuron tested during step-ramp pursuit with target blink. Response continues during the blink, indicating extraretinal sensitivity. (B) Representative neuronal response of FEF neuron during sinusoidal SP tracking at 0.5 Hz ± 10° and visual stimulation with a large-field, constant speed random dot pattern (0.5 Hz ± 10°). This SP-related neuron also showed a visual response at short latency (∼65 ms) following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in activated and nonactivated FEF neurons. Isolation was lost on some SP neurons before visual testing during fixation (SP+?).
Mentions: FEF neurons evince sensitivity to eye and visual motion per se (Fig. 3). Figure 3A shows an example of a FEF neuron tested during SP where the target was briefly extinguished to reveal extraretinal sensitivity, as reported by other investigators (Tanaka and Fukushima 1998). Figure 3B shows a representative FEF neuron tested during sinusoidal SP and during fixation with visual stimulation. In this testing, either a small target spot (Fig. 3B, left) or a large-field visual stimulus (Fig. 3B, right) was moved in a direction and speed like that used during SP eye movements. These types of visual stimuli produced direction-selective modulation of neuronal firing (see Discussion). In Figure 3C, we show the distribution of FEF neurons in our sample with sensitivity to both eye motion and large-field visual motion. At least 60% of our antidromically activated FEF neurons had explicit visual and eye motion sensitivity. These results argue for inclusion of eye and retinal image motion parameters in our modeling studies (see Discussion).

Bottom Line: In contrast, FEF neurons not activated following ES of rNRTP were often most sensitive to eye velocity.In similar modeling studies, we found that rNRTP neurons were also biased toward eye acceleration.Therefore, our results suggest that neurons in the FEF-rNRTP pathway carry signals that could play a primary role in initiation of SP.

View Article: PubMed Central - PubMed

Affiliation: Division of Sensory-Motor Systems, Yerkes National Primate Research Center, and Department of Neurology, Emory University, 954 Gatewood Road Northeast, Atlanta, GA 30329, USA.

ABSTRACT
The cortical pursuit system begins the process of transforming visual signals into commands for smooth pursuit (SP) eye movements. The frontal eye field (FEF), located in the fundus of arcuate sulcus, is known to play a role in SP and gaze pursuit movements. This role is supported, at least in part, by FEF projections to the rostral nucleus reticularis tegmenti pontis (rNRTP), which in turn projects heavily to the cerebellar vermis. However, the functional characteristics of SP-related FEF neurons that project to rNRTP have never been described. Therefore, we used microelectrical stimulation (ES) to deliver single pulses (50-200 microA, 200-micros duration) in rNRTP to antidromically activate FEF neurons. We estimated the eye or retinal error motion sensitivity (position, velocity, and acceleration) of FEF neurons during SP using multiple linear regression modeling. FEF neurons that projected to rNRTP were most sensitive to eye acceleration. In contrast, FEF neurons not activated following ES of rNRTP were often most sensitive to eye velocity. In similar modeling studies, we found that rNRTP neurons were also biased toward eye acceleration. Therefore, our results suggest that neurons in the FEF-rNRTP pathway carry signals that could play a primary role in initiation of SP.

Show MeSH
Related in: MedlinePlus