Neuronal migration and positioning in the developing mammalian cortex depends on molecules of the Reelin signaling system, including the downstream adapter protein Dab1. This week, Olson et al. suppressed expression of Dab1 in migrating cortical neurons in vivo using RNAi. Normally, cells migrated through the cell-dense cortical plate (CP) and entered the marginal zone (MZ), where the leading process typically became branched. At embryonic day 20 in lateral neocortex and cingulate cortex, Dab1-deficient neuronal cell bodies were displaced away from the CP/MZ border compared to controls. The leading processes and postnatal dendrite of Dab1- deficient cells failed to contact the MZ and were less branched compared to controls.
2. The Flight Plan of the
Kaushik Ghose and Cynthia F. Moss
A bat has the advantage of navigating and hunting in the dark, but the complication that echoes of the emitted ultrasonic pulses must be decoded as the animal "gazes" and grazes. This involves continuous conversion of the binaural frequency and times of the echoes into spatial location, thus directing a flight plan. Ghose and Moss examined such sensorimotor integration in the big brown bat, Eptesicus fuscus. Infrared cameras and microphones tracked a bat in a dark, empty room as it located and retrieved a suspended mealworm. The sonar pulses vary from 4 Hz in search mode to 150–200 Hz during prey detection. The authors describe a gain factor that links acoustic gaze (sonar direction) to locomotion (flight turn rate) that changed with behavioral state. Much like a visually guided animal, the bat can operate in scan mode without altering its movement direction, but in attack mode, the gain is high, and movement is determined by prey location.
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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