G. Knop et al., A central pattern-generating network contributes to "reflex-reversal"-likeleg motoneuron activity in the locust, J NEUROPHYS, 86(6), 2001, pp. 3065-3068
We introduce a new rhythmic preparation of the locust mesothoracic segment
that exhibits long-lasting rhythmicity without pharmacological treatment. I
n most experiments, isolation of the locust mesothoracic ganglion from the
anterior and posterior ganglia causes episodes of patterned activity to be
generated in leg motoneurons that supply the femur-tibia (FT) joint. Flexor
and extensor tibiae motoneuron pools exhibit alternating bursts of activit
y mostly composed of doublets and triplets of bursts. Motor activity during
these episodes appears to be centrally generated because it persisted afte
r complete deafferentation in 37% of the preparations; however, propriocept
ive signals from the middle leg strongly influenced the patterning of moton
euron activity. Mimicking FT joint flexion by elongating the femoral chordo
tonal organ during an extensor burst terminates extensor activity and initi
ates flexor activity. The reverse is true for a mimicked extension during a
flexor burst. This motor activity represents a reflex reversal that is typ
ically observed in the locomotor state of the stick insect walking system.
Our results provide evidence that this "reversed" reflex is caused by the a
ction of central pattern-generating networks.