Biology subjects

Corneil, B. D.

Publications and source records attributed to Corneil, B. D..

4 recordsLinked to original sources

bioRxiv2018

A rapid visuomotor response on the human upper limb is selectively influenced by implicit, but not explicit, motor learning

How do humans learn to adapt their motor actions to achieve task success? Recent behavioral and patient studies have challenged the classic notion that motor learning arises solely from the errors produced during a task, suggesting instead that explicit cognitive strategies can act in concert with the implicit, error\"based, motor learning component. Here, we show that the earliest wave of directionally-tuned neuromuscular activity that occurs within ~100 ms of peripheral visual stimulus onset is selectively influenced by the implicit component of motor learning. In contrast, the voluntary neuromuscular activity associated with reach initiation, which evolves ~100 to 200 ms later is influenced by both the implicit and explicit components of motor learning. The selective influence of the implicit, but not explicit, component of motor learning on the earliest cascade of neuromuscular activity supports the notion that these components of motor learning can differentially influence descending motor pathways.

neuroscience↗

bioRxiv2017

Frontal eye field inactivation reduces saccade preparation in the superior colliculus, but does not alter how preparatory activity relates to saccade latency

A neural correlate for saccadic reaction times (SRTs) in the gap saccade task is the level of preparatory activity in the intermediate layers of the superior colliculus (iSC) just before visual target onset: greater levels of iSC preparatory activity precede shorter SRTs. The frontal eye fields (FEF) are one likely source of such iSC preparatory activity, since FEF preparatory activity is also inversely related to SRT. To better understand the FEFs role in saccade preparation, and the way in which such preparation relates to SRT, in two male rhesus monkeys we examined iSC preparatory activity during unilateral reversible cryogenic inactivation of the FEF. FEF inactivation increased contralesional SRTs, and lowered ipsilesional iSC preparatory activity. FEF inactivation also reduced fixation-related activity in the rostral iSC. Importantly, the distributions of SRTs generated with or without FEF inactivation overlapped, enabling us to conduct a novel population-level analyses examining iSC preparatory activity just before generation of SRT-matched saccades. These analyses revealed no change during FEF inactivation in the relationship between iSC preparatory activity and SRT-matched saccades across a range of SRTs, even for the occasional express saccade. Thus, while our results emphasize that the FEF has an overall excitatory influence on preparatory activity in the iSC, the communication between the iSC and downstream oculomotor brainstem is unaltered for SRT-matched saccades, suggesting that the integration of preparatory and visual signals in the SC just before saccade initiation is largely independent of the FEF for saccades generated in this task.\n\nSignificance statementHow does the brain decide when to move? Here, we investigate the role of two oculomotor structures, the superior colliculus (SC) and frontal eye fields (FEF), in dictating visually-guided saccadic reaction times (SRTs). In both structures, higher levels of preparatory activity precede shorter SRTs. Here, we show that FEF inactivation increases SRTs and decreases SC preparatory activity. Surprisingly, a population-level analysis of SC preparatory activity showed a negligible impact of FEF inactivation, providing one examines SRT-matched saccades. Thus, while the FEF is one source of preparatory input to the SC, it is not a critical source, and it is not involved in the integration of preparatory activity and visual signals that precedes saccade initiation in simple visually-guided saccade tasks.

neuroscience↗

bioRxiv2017

Done in 100 ms: Path-dependent visuomotor transformation in the human upper limb

A core assumption underlying mental chronometry is that more complex tasks increase cortical processing, prolonging reaction times. Here we show that increases in task complexity alter the magnitude, rather than the latency, of the output for a circuit that rapidly transforms visual information into motor actions. We quantified visual stimulus-locked responses (SLRs), which are changes in upper limb muscle recruitment that evolve at a fixed latency [~]100 ms after novel visual stimulus onset. First, we studied the underlying reference frame of the SLR, by dissociating initial eye and hand position. Despite its quick latency, we found that the SLR was expressed in a hand-centric reference frame, suggesting that the circuit mediating the SLR integrated retinotopic visual information with body configuration. Next, we studied the influence of planned movement trajectory, requiring participants to prepare and generate curved or straight reaches in the presence of obstacles to attain the same visual stimulus. We found that SLR magnitude reflected the initial planned movement trajectory, regardless of the ensuing movement curvature. Based on these results, we suggest that the circuit mediating the SLR lies in parallel to other well-studied corticospinal pathways. Although the fixed latency of the SLR precludes extensive cortical processing, inputs conveying information relating to task complexity, such as body configuration and planned movement trajectory, can pre-set nodes within the circuit underlying to the SLR to modulate its magnitude.\n\nSIGNIFICANCE STATEMENTA core assumption underlying mental chronometry is that more complex tasks increase cortical processing, prolonging reaction times. Here, we showed that increases in task complexity altered the magnitude, rather than the latency, of a circuit that rapidly transforms visual information into motor actions. We focus on stimulus-locked responses (SLRs), which are changes in upper limb muscle recruitment that evolve at a fixed latency [~]100 ms after novel visual stimulus onset. We showed that despite is quick latency, the circuitry mediating the SLR transformed a retinotopic visual signal into a hand-centric motor command suitable to contribute to the initial movement trajectory. We suggest that this circuit lies in parallel to other well-studied corticospinal pathways.

neuroscience↗

bioRxiv2017

Frontal Eye Field inactivation diminishes Superior Colliculus activity, but delayed saccadic accumulation governs reaction time increases

Stochastic accumulator models provide a comprehensive framework for how neural activity could produce behavior. Neural activity within the frontal eye fields (FEF) and intermediate layers of the superior colliculus (iSC) support such models for saccade initiation, by relating variations in saccade reaction time (SRT) to variations in parameters such as baseline, rate of accumulation of activity, or threshold. Here, by recording iSC activity during reversible cryogenic inactivation of the FEF in non-human primates, we causally test which parameter(s) best explains concomitant increases in SRT. While FEF inactivation decreased all aspects of ipsilesional iSC activity, decreases in accumulation rate and threshold poorly predicted accompanying increases in SRT. Instead, SRT increases best correlated with delays in the onset of saccade-related accumulation. We conclude that FEF signals govern the onset of saccade-related accumulation within the iSC, and that the onset of accumulation is a relevant parameter for stochastic accumulation models of saccade initiation.\n\nSignificance StatementThe superior colliculus (SC) and frontal eye fields (FEF) are two of the best-studied areas in the primate brain. Surprisingly, little is known about what happens in the SC when the FEF is temporarily inactivated. Here, we show that temporary FEF inactivation decreases all aspects of functionally-related activity in the SC. This combination of techniques also allowed us to relate changes in SC activity to concomitant increases in saccadic reaction time (SRT). Although stochastic accumulator models relate SRT increases to reduced rates of accumulation or increases in threshold, such changes were not observed in the SC. Instead, FEF inactivation delayed the onset of saccade-related accumulation, emphasizing the importance of this parameter in biologically-plausible models of saccade initiation.

neuroscience↗