Cognitive Information Processing

Contains reports on six research projects.National Institutes of Health (Grant 5 PO1 GM14940-03)National Institutes of Health (Grant 5 PO1 GM15006-03)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U.S. Air Force) under Contract DA 28-043-AMC-02536(E)National Institutes of Health (Grant 5 TO1 GM01555-03

Communications Biophysics

Contains research objectives, summary of research and reports on three research projects.National Institutes of Health (Grant 5 PO1 GM14940-04)National Institutes of Health (Grant 5 TOl GM01555-04)National Aeronautics and Space Administration (Grant NGL 22-009-304

Morphological characterization of bushy cells and their inputs in the laboratory mouse (Mus musculus) anteroventral cochlear nucleus.

PMC3753269Spherical and globular bushy cells of the AVCN receive huge auditory nerve endings specialized for high fidelity neural transmission in response to acoustic events. Recent studies in mice and other rodent species suggest that the distinction between bushy cell subtypes is not always straightforward. We conducted a systematic investigation of mouse bushy cells along the rostral-caudal axis in an effort to understand the morphological variation that gives rise to reported response properties in mice. We combined quantitative light and electron microscopy to investigate variations in cell morphology, immunostaining, and the distribution of primary and non-primary synaptic inputs along the rostral-caudal axis. Overall, large regional differences in bushy cell characteristics were not found; however, rostral bushy cells received a different complement of axosomatic input compared to caudal bushy cells. The percentage of primary auditory nerve terminals was larger in caudal AVCN, whereas non-primary excitatory and inhibitory inputs were more common in rostral AVCN. Other ultrastructural characteristics of primary auditory nerve inputs were similar across the rostral and caudal AVCN. Cross sectional area, postsynaptic density length and curvature, and mitochondrial volume fraction were similar for axosomatic auditory nerve terminals, although rostral auditory nerve terminals contained a greater concentration of synaptic vesicles near the postsynaptic densities. These data demonstrate regional differences in synaptic organization of inputs to mouse bushy cells rather than the morphological characteristic of the cells themselves.JH Libraries Open Access Fun

The temporal representation of the delay of iterated rippled noise in the ventral cochlear nucleus of the guinea-pig

We have examined the temporal discharge patterns of single units from the ventral cochlear nucleus (VCN) of anaesthetized guinea-pigs in response to iterated rippled noise (IRN). The pitch range evoked by the stimuli was from 32 to 1000 Hz.Single units were classified into four groups using existing classification schemes: primary-like (PL), onset (O), sustained chopper (CS) and transient chopper (CT). For all unit types the delay of the IRN stimuli was well represented in the all-order interspike interval histograms (ISIHs).A subset of the onset units (onset-chopper, OC) showed a clear preference for some delays of the IRN in their first-order interval statistics. We describe this delay preference as ‘periodicity tuning’. The delay at which the pitch estimate was at its maximum was designated its best periodicity. The range of best periodicities for OC units was 3.75-13 ms (between 77 and 267 Hz).The other unit types also showed enhancement of the first-order interval statistics at the delay of the IRN. The range of best periodicities was 1.4-8.8 ms (113-714 Hz) for the CT group, 2.25-10.8 ms (93-444 Hz) for the CS group and 0.5-4.6 ms (217-2000 Hz) for the PL group.The correlation between the maximum interval enhancement observed in response to the IRN stimuli and the peak in the first-order ISIH in response to white noise was 0.81 for OC units, 0.72 for CS units, 0.44 for CT units and -0.15 for PL units.These results demonstrate that all unit types in the VCN can enhance the representation of the delay of IRN using first-order interspike intervals (ISIs) over a range of periodicities. CS and OC units show the greatest range of best periodicities and they are well-suited to encode the delay of IRN in their first-order ISIs for a wide range of pitches