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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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Location of FEF and examples of unit testing during SP. (A) Recoding sites of SP neurons in right FEF verified by structural magnetic resonance imaging (MRI) (T1-weighted, fast spin echo; Siemens, 3-T magnet). Line drawing indicating representative recording tracks run on a 15° angle tilted lateral with respect to pure vertical. Penetrations and unit depths reconstructed by MRI and measurements taken from microdrive readings during recording SP neurons in FEF. (B) SP-related FEF neuron antidromically activated (*) following biphasic single-pulse electrical stimulation (50 μA, 200-μs duration) of the rNRTP at the depth of SP neurons. Top panel: 5 successive antidromic trials in “search mode” aligned on the electrical stimulation artifact. Middle panel: antidromic spikes (*) continue to be elicited when inappropriate timing was used between a naturally occurring FEF spike and the stimulus pulse. Bottom panel: when appropriate timing is used between the naturally occurring spike and the stimulus pulse collision occurs (i.e., no evoked FEF at expected time (*). (C) Histogram of latencies between onset of electrical stimulation pulse in rNRTP and evoked FEF spikes. Median latency between stimulation in the rNRTP and evoked FEF spikes was 1.69 ms. Mean action potential duration of antidromically activated FEF neurons was 331 μs (standard deviation = 103 μs). (D) Representative well-isolated FEF neuron during 2 successive step-ramp trials.
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fig1: Location of FEF and examples of unit testing during SP. (A) Recoding sites of SP neurons in right FEF verified by structural magnetic resonance imaging (MRI) (T1-weighted, fast spin echo; Siemens, 3-T magnet). Line drawing indicating representative recording tracks run on a 15° angle tilted lateral with respect to pure vertical. Penetrations and unit depths reconstructed by MRI and measurements taken from microdrive readings during recording SP neurons in FEF. (B) SP-related FEF neuron antidromically activated (*) following biphasic single-pulse electrical stimulation (50 μA, 200-μs duration) of the rNRTP at the depth of SP neurons. Top panel: 5 successive antidromic trials in “search mode” aligned on the electrical stimulation artifact. Middle panel: antidromic spikes (*) continue to be elicited when inappropriate timing was used between a naturally occurring FEF spike and the stimulus pulse. Bottom panel: when appropriate timing is used between the naturally occurring spike and the stimulus pulse collision occurs (i.e., no evoked FEF at expected time (*). (C) Histogram of latencies between onset of electrical stimulation pulse in rNRTP and evoked FEF spikes. Median latency between stimulation in the rNRTP and evoked FEF spikes was 1.69 ms. Mean action potential duration of antidromically activated FEF neurons was 331 μs (standard deviation = 103 μs). (D) Representative well-isolated FEF neuron during 2 successive step-ramp trials.

Mentions: We first located the FEF by its stereotaxic location (anterior = 22 mm, lateral = 20 mm) and by finding neurons that were modulated during SP of a small diameter (0.2°) target spot moving (±10°, 0.1–0.75 Hz) over a dark background. We further verified that our recording locations were in the FEF using magnetic resonance imaging (T1-weighted, fast spin echo; Siemens, 3-T magnet [Siemens, Princeton, NJ]) and electrode track depth measurements taken from microdrive readings while recording SP neurons in FEF (Fig. 1A). The location of our SP neurons in the fundus of the arcuate sulcus was similar to that reported by other investigators (e.g., Tanaka and Fukushima 1998).


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

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

Location of FEF and examples of unit testing during SP. (A) Recoding sites of SP neurons in right FEF verified by structural magnetic resonance imaging (MRI) (T1-weighted, fast spin echo; Siemens, 3-T magnet). Line drawing indicating representative recording tracks run on a 15° angle tilted lateral with respect to pure vertical. Penetrations and unit depths reconstructed by MRI and measurements taken from microdrive readings during recording SP neurons in FEF. (B) SP-related FEF neuron antidromically activated (*) following biphasic single-pulse electrical stimulation (50 μA, 200-μs duration) of the rNRTP at the depth of SP neurons. Top panel: 5 successive antidromic trials in “search mode” aligned on the electrical stimulation artifact. Middle panel: antidromic spikes (*) continue to be elicited when inappropriate timing was used between a naturally occurring FEF spike and the stimulus pulse. Bottom panel: when appropriate timing is used between the naturally occurring spike and the stimulus pulse collision occurs (i.e., no evoked FEF at expected time (*). (C) Histogram of latencies between onset of electrical stimulation pulse in rNRTP and evoked FEF spikes. Median latency between stimulation in the rNRTP and evoked FEF spikes was 1.69 ms. Mean action potential duration of antidromically activated FEF neurons was 331 μs (standard deviation = 103 μs). (D) Representative well-isolated FEF neuron during 2 successive step-ramp trials.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig1: Location of FEF and examples of unit testing during SP. (A) Recoding sites of SP neurons in right FEF verified by structural magnetic resonance imaging (MRI) (T1-weighted, fast spin echo; Siemens, 3-T magnet). Line drawing indicating representative recording tracks run on a 15° angle tilted lateral with respect to pure vertical. Penetrations and unit depths reconstructed by MRI and measurements taken from microdrive readings during recording SP neurons in FEF. (B) SP-related FEF neuron antidromically activated (*) following biphasic single-pulse electrical stimulation (50 μA, 200-μs duration) of the rNRTP at the depth of SP neurons. Top panel: 5 successive antidromic trials in “search mode” aligned on the electrical stimulation artifact. Middle panel: antidromic spikes (*) continue to be elicited when inappropriate timing was used between a naturally occurring FEF spike and the stimulus pulse. Bottom panel: when appropriate timing is used between the naturally occurring spike and the stimulus pulse collision occurs (i.e., no evoked FEF at expected time (*). (C) Histogram of latencies between onset of electrical stimulation pulse in rNRTP and evoked FEF spikes. Median latency between stimulation in the rNRTP and evoked FEF spikes was 1.69 ms. Mean action potential duration of antidromically activated FEF neurons was 331 μs (standard deviation = 103 μs). (D) Representative well-isolated FEF neuron during 2 successive step-ramp trials.
Mentions: We first located the FEF by its stereotaxic location (anterior = 22 mm, lateral = 20 mm) and by finding neurons that were modulated during SP of a small diameter (0.2°) target spot moving (±10°, 0.1–0.75 Hz) over a dark background. We further verified that our recording locations were in the FEF using magnetic resonance imaging (T1-weighted, fast spin echo; Siemens, 3-T magnet [Siemens, Princeton, NJ]) and electrode track depth measurements taken from microdrive readings while recording SP neurons in FEF (Fig. 1A). The location of our SP neurons in the fundus of the arcuate sulcus was similar to that reported by other investigators (e.g., Tanaka and Fukushima 1998).

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