The Journal of Neuroscience, September 15, 1998, 18(18):7599-7611
Parallel Projection of Amplitude and Phase Information from the
Hindbrain to the Midbrain of the African Electric Fish
Gymnarchus niloticus
Masashi
Kawasaki and
Yuan-Xing
Guo
Department of Biology, University of Virginia, Charlottesville,
Virginia 22903
Two distinct sensory cues in electrosensory signals, amplitude
modulation and differential phase modulation, are essential for an
African wave-type electric fish, Gymnarchus, to perform the jamming avoidance responses. Individual neurons in the first brain
station for central processing, the electrosensory lateral line lobe
(ELL), were investigated by the in vivo whole-cell
recording and labeling technique for their physiological responses,
location, morphology, and projection areas.
Neurons in the dorsal zone of the ELL responded selectively to
amplitude modulation. Neurons in the outer cell layer of the medial
zone were categorized physiologically into two groups: amplitude-sensitive and differential phase-sensitive. All but one
neuron in the inner cell layer of the medial zone responded exclusively
to differential phase modulation. All neurons recorded and labeled in
the ELL had pyramidal morphology with large and extensive apical
dendrites and less extensive basal dendrites. They were found to
project to two midbrain nuclei: the nucleus praeeminentialis and the
torus semicircularis. Amplitude-sensitive neurons in the dorsal zone
projected exclusively to the lateral posterior subdivision, the torus
semicircularis. Neurons in the medial zone projected to the medial
dorsal and lateral anterior subdivisions of the torus
semicircularis.
Although some neurons in the ELL responded to both amplitude and
differential phase modulation, they did not differentiate between
temporal patterns of the two cues that encode necessary information for
the jamming avoidance response. Overlapping projection of amplitude and
differential phase-sensitive neurons to the torus semicircularis
suggests integration of the two sensory cues in this nucleus.
Key words:
electric fish; jamming avoidance response; phase
comparison; binaural comparison; whole-cell recording; parallel
projection
Copyright © 1998 Society for Neuroscience 0270-6474/98/18187599-13$05.00/0