Short-latency evoked potentials recorded from the vertex of adult cats in response to click stimulation (the far-field acoustic response) were analyzed in a series of lesion experiments to determine the origins of each component. The resultant data indicate that the primary generator of potential is the acoustic nerve; of potential 2, the cochlear nucleus; of potential 3, neurons of the superior olivary complex activated by projections crossing the midline; of potential 4, neurons of the ventral nucleus of the lateral lemniscus and preolivary region activated equally by crossed and uncrossed projections; and of potential 5, neurons of the inferior colliculus activated primarily by crossed projections.

No abstract

No abstract

No abstract

No abstract

No abstract

Variations in streamflow at falls and cascades can create transitory barriers to upstream passage of adult anadromous salmonids. In this study, we evaluated the ability of six anadromous salmonids (coho salmon Oncorhynchus kisutch, pink salmon O. gorbuscha, chum salmon O. keta, sockeye salmon O. nerka, Chinook salmon O. tshawytscha, and steelhead O. mykiss) to pass five sets of falls or cascades within Ward Creek, Alaska, a stream regulated by Connell Dam. The study focused on determining suitable instream flow releases to afford passage. Each set of falls was surveyed under three flow conditions (about 0.91, 1.34, and 3.0 m 3 /s), and access portals were identified. Using computed stageÀdischarge relationships and published swimming and jumping criteria, we evaluated the falls barrier potential over a range (0.23-11.33 m 3 /s) of flows. Analysis indicated pink salmon and chum salmon would be relegated to the area below the lower two falls. Flows affording passage over all five falls for the other species (excluding Chinook salmon) were defined as ''flow windows'' and ranged from 0.66 to 3.01 m 3 /s. Flow windows varied by species; the narrowest range of acceptable passage flows was found for sockeye salmon, the widest was found for steelhead, and the range for coho salmon was intermediate. Escapement surveys generally confirmed our analysis; pink salmon and chum salmon were only found below the lowermost falls. The flow windows for passage were compatible with a set of instream flow recommendations derived via a PHABSIM-based study but were incompatible with the highest flow recommendation based on the method of Tennant (1976). Care must be taken when evaluating instream flow needs to ensure that all flow-sensitive factors are considered.

Morphometric data have indicated that most (> 95%) of the granule cell axonal synapses are located along the parallel fibers. The ascending axons of granule cells, however, exert powerful excitatory effects on the activities of Purkinje cells. To resolve this apparent conflict, we propose that some of the parallel fiber synapses overlying a functionally homogeneous granule cell patch can discharge in close synchrony with the ascending axon synapses from that same granule cell patch, thereby augmenting the excitatory action from ascending axons. Moreover, we also propose that age may be an important factor in the ascending axon synapses. We examined the synaptic varicosities along the ascending axons and parallel fibers in the anterior lobe of the male NIA C57BL/6j mouse. Between 2.5 and 10 months, the fraction of synaptic varicosities anatomically associated with the ascending axons increased from 2.6% to 6.6% whereas the fraction of synaptic varicosities that can discharge in synchrony with ascending axon synapses (including some parallel fiber synapses) increased from 17.3% to 39% (assuming a granule cell patch of 300 x 300 microm). The results of the present study may be relevant to understanding the role of the ascending axon vs. the parallel fibers. Differential age-related synaptic changes in these two portions of the granule cell axons may constitute an important age-dependent synaptic remodeling in the granule cell-Purkinje cell synaptic system.