Biomedical subjects
Publications and source records attributed to P Mandava.
Cavernous sinus thrombosis is a serious condition, which, if not recognized early, can lead to a fulminant course. Knowledge of risk factors along with early recognition of signs and symptoms may alter the course of this condition. We present a case of a patient with cavernous sinus thrombosis with characteristic findings on MRI. Biopsy of the sinuses revealed mucromycosis as the offending agent.
Seventy-one inferior colliculus neurons, with best frequencies below 1.5 kHz, were studied in a binaural, forward-masking paradigm in chinchilla. Masker and signal frequencies were presented at neuronal best frequency. Masker level was set 10-15 dB above neuronal threshold and varied to include a range of signal-to-masker ratios and overall intensities. Without the masker, 33 of the neurons preferred an in-phase signal (SO), 29 an out-of-phase (S pi) signal, and the remaining 9 had 'no-preference' (NP), responding equally well to SO and S pi. Complete protocols from 53 of the 71 neurons were obtained with and without maskers over a range of levels. With an in-phase masker (NO), some neurons responded better to dichotic (NOS pi) than to diotic (NOSO) sounds. Generally, they maintained a particular phase preference with and without masker. Some neurons, however, altered phase preference and responsivity when binaural maskers were added to signal. Signal-to-noise ratios between 0 and 30 dB were sufficient to differentiate neuronal responsiveness to NOSO and NOS pi. The results suggest that identical neural mechanisms are not involved in processing unmasked (SO or S pi) and masked binaural sounds (NOSO, NOS pi). Furthermore, changes in neuronal sensitivity favor the NOS pi condition upon addition of noise (NO) to the signal (SO or S pi). We conclude that greater neural activity is generated with stimuli which produce masking-level difference than stimuli that do not.
This study examined neuronal discharge rates and temporal patterns to vowels and vowel sequences in chinchilla. The properties of primary-like, chopper, and onset neurons were studied using vowels /i/, /a/, and /u/ individually and paired with separations (0-100 ms), at sound levels above and below thresholds. The interspike interval, period, and post-stimulus-time histograms of all neuronal types to a vowel were modified when in a sequence. Primary-like and chopper discharges were reduced and enhanced depending on vowel sequence parameters; onset neurons exhibited discharge rate reductions only and not enhancements. In addition to rate changes, novel discharge intervals appeared with vowel pairs. An unexpected finding on choppers was that subthreshold levels of the preceding vowel in a paired sequence enhanced discharges to the succeeding one. Reducing levels of preceding or increasing levels of following vowels evoked changes not predictable from single vowel data. Thus the responses to paired vowels in a sequence are interactive. Patterns of discharges and rate functions to vowel sounds from neurons of the same type varied greatly. The cochlear nuclei harbor anatomically and functionally diverse neurons. Because of this heterogeneity, the neural transformations of vowel segments by all cochlear nucleus neuronal types can not be predicted from sinusoidal data.
A zinc-specific retrograde transport method has been employed to map the zinc-containing neuronal projections to the septal nuclei. Sodium selenite was infused iontophoretically into the lateral or medial septal nuclei to precipitate vesicular zinc as ZnSe in situ, and the neurons that were subsequently labeled by the retrograde transport of ZnSe to their perikarya were mapped. Zinc-containing cells of origin were found only in the hippocampal formation and predominantly in two regions thereof: (i) in s. oriens and deep s. pyramidale of fields CA3a and CA2 and (ii) in s. pyramidale of distal CA1 and adjacent prosubiculum.