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An uncrossed tectopontine pathway mediates ipsiversive circling
1University of Toronto, Department of Psychology, Ont., Canada.
Behavioural Brain Research
|March 31, 1993
Summary
Continuous tectopontine axons from the superior colliculus (SC) to the ventrolateral pons (VLP) mediate ipsiversive circling. This study used the collision method to confirm the role of these continuous pathways in rodent circling behavior.
Area of Science:
- Neuroscience
- Motor Control
- Animal Behavior
Background:
- Stimulating the superior colliculus (SC) in rodents causes ipsiversive circling and avoidance.
- The uncrossed tectopontine pathway from the SC to the ventrolateral pons (VLP) also elicits circling, but smoother and faster.
Purpose of the Study:
- To determine if continuous tectopontine axons mediate ipsiversive circling evoked by stimulation at both the SC and VLP.
- Investigate the properties of axonal conduction along the tectopontine pathway.
Main Methods:
- Utilized the collision method with paired stimulating pulses (conditioning and testing) at the SC and VLP.
- Measured collision percentages, refractory periods, and conduction velocities of neural signals.
Main Results:
- Collision varied significantly (25-64%) between the SC and VLP, indicating continuous axonal pathways.
- Refractory periods ranged from 0.4 to 3 ms, with conduction velocities between 1.2-19 m/s, often in two distinct ranges.
- Slower conducting axons contributed more significantly in trials with higher collision percentages.
Conclusions:
- Continuous axons from the superior colliculus to the ventrolateral pons are the primary mediators of ipsiversive circling.
- Observed asymmetries suggest potential transsynaptic involvement in some SC stimulation responses.