Evidence for the role of dendritic spines in the temporal filtering properties of neurons: the decoding problem and beyond.
The question of relations between structure and function acutely applies to the search for the functional role of dendritic spines. While dendritic spines are a prominent and widespread structural feature of neurons in the central nervous system, their function is poorly understood. Because the conducting core of a spine stem can be of extremely small dimensions, a large axial resistance to current flow and "low-pass" filtering of inputs have been hypothesized. Here we show that neurons in the dorsal torus semicircularis of the electric fish Eigenmannia show real-time fluctuations in their transmembrane potential that reflect modulations in the amplitude of a high-frequency sinusoidal carrier signal. In 18 neurons recorded intracellularly and labeled with Lucifer yellow, the decrease in the magnitude of these potentials with increasing rate of amplitude modulation (i.e., low-pass temporal filtering) was positively correlated (r = 0.79, P < 0.001, over a range of one to two octaves in modulation rate) with the mean dendritic spine density (range, 0-0.38 spine per micron of dendritic length) of the cell. The acquisition of synaptic input through dendritic spines may be a general mechanism for achieving the temporal filtering that underlies real-time signal processing in the central nervous system.
Rose
G J
GJ
Department of Biology, University of Utah, Salt Lake City 84112.
Call
S J
SJ
D000200:Action Potentials; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D003712:Dendrites / Q000502:physiology* / Q000648:ultrastructure; D004555:Electric Fish / Q000502:physiology*; D008564:Membrane Potentials; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission; D013997:Time Factors