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Biomedical subjects

L M Kitzes

Publications and source records attributed to L M Kitzes.

29 records · Page 2Linked to original sources
PubMed1983

Ascending projections to the inferior colliculus following unilateral cochlear ablation in the neonatal gerbil, Meriones unguiculatus.

We evaluated the consequences of neonatal cochlear destruction upon ascending projections to the inferior colliculi. Unilateral cochlear ablations were performed in both neonatal and adult gerbils. Four to 12 months later, the inferior colliculus (IC) was examined physiologically and injected unilaterally with horseradish peroxidase (HRP). The number of labeled cells was determined bilaterally in all three divisions of cochlear nucleus (CN) and in the medial superior olive (MSO). In both experimental groups, transneuronal changes within the deafferented CN were greater in the ventral divisions than in the dorsal division. On the unoperated side the magnitude of projections from CN to the inferior colliculi was altered in animals lesioned as neonates. Following HRP injections into the IC on the unoperated side, the number of ipsilaterally labeled cells in CN (unoperated side) was significantly greater in the neonatal experimental group than in adult experimental and control animals. These anatomical changes were accompanied by increased ipsilaterally evoked excitatory activity recorded in the IC on the unoperated side. Following HRP injections into the IC on the ablated side, the number of contralaterally labeled cells in CN (unoperated side) was significantly reduced in animals lesioned as neonates as compared with control animals. The number of labeled cells in ipsilateral MSO was not significantly different across groups. Our interpretation is that unilateral cochlear ablation in neonatal gerbils results in an increase in the magnitude of ipsilateral projections and a decrease in the magnitude of contralateral projections from CN on the unoperated side to the inferior colliculi. These data suggest that the normal pattern of innervation of the IC results, in part, from interactions among afferent projections.

Animals↗
PubMed1981

Postnatal development of frequency and intensity sensitivity of neurons in the anteroventral cochlear nucleus of kittens.

Tuning curves and spike count-vs.-intensity functions were derived form tone-burst responses of single neurons of the anteroventral cochlear nucleus of kittens 4-45 days of age. During the first postnatal week tuning curves are relatively shallow and thresholds are high. With advancing age there is a progressive reduction in threshold and sharpness of tuning. Sharpening of tuning during the first several weeks postpartum seems to be due to a differential reduction in threshold between CF and frequencies below CF. Spike count-vs.-intensity functions are steep in young kittens as compared to adults. During the first few postnatal weeks the dynamic range and shapes of the functions take on the characteristics of adult AVCN neurons.

Action Potentials↗
PubMed1980

Patterns of responses of cortical cells to binaural stimulation.

The relationship between stimulus intensity and response latency implies that the relative time of arrival of input to binaurally sensitive loci can vary over a range significantly longer than the interaural delays resulting from the travel time of sound between the ears. To investigate the effect of such potentially long inter-arrival time intervals, responses of binaurally sensitive neurons in auditory cortex of cats were examined over relatively long interaural delays. Two kinds of interaural delay functions were observed. One kind involved a sharp transition to a reduced response rate over a narrow range of interaural delays, while the other involved a gradual reduction of response rate over a relatively prolonged range of interaural delays. The amount of suppression was found to be a sensitive function of both interaural delay and the relative intensity of the stimuli delivered to the two ears. The pattern of suppression across a binaural response was stationary with respect to the excitatory contralateral stimulus over wide ranges of interaural delay. In addition, certain characteristics of a group of cells generally responsive only to binaural stimulation are described. A model is proposed which accounts for the observed stationarity of the response suppression.

Animals↗
PubMed1978

Signs of functional maturation of peripheral auditory system in discharge patterns of neurons in anteroventral cochlear nucleus of kitten.

1. Responses to pure tones were recorded from single neurons in the anteroventral cochlear nucleus (AVCN) in kittens ranging in age from 4 to 45 days. Different response properties mature at different times after birth. 2. The shapes of response areas of AVCN neurons after the 1st postnatal week resemble those recorded in the AVCN and auditory nerve of the adult. During the 1st wk after birth the high-frequency portion of the response area is extended. Phase-locked responses to stimulus frequencies below about 600 Hz occur at this time. Phase vs. frequency measurements and shapes of response areas indicate that by the end of the 1st postnatal week the cochlear partition may be capable of supporting a traveling wave along most of its length. 3. Functional development proceeds through a second phase which lasts until the end of the 2nd or the beginning of the 3rd wk of life. During that time threshold, maximal discharge rate, and average first-spike latency achieve adult values. 4. Phase-locking to low-frequency tones, to the extent displayed by phase-sensitive neurons in the adult AVCN or auditory nerve, is achieved last, after the 3rd or 4th wk postpartum.

Age Factors↗
PubMed1977

Organization of auditory cortex in the owl monkey (Aotus trivirgatus).

The region of cerebral cortex in the owl monkey that is responsive to acoustic stimulation is located on the dorsal and lateral surfaces of the rostral half of the superior temporal gyrus. Systematic microelectrode mapping of this area has revealed multiple frequency representations. The boundaries of these fields determined electrophysiologically correlate with the architectural boundaries apparent in Nissl stained material. On the basis of combined cytoarchitectonic and electrophysiological maps we have divided auditory cortex into five fields. Two of them, the primary field (AI) and the field rostral to it (R) are somewhat similar architectonically and constitute the central core of auditory cortex. Each of these two fields has a complete and orderly representation of the audible frequency spectrum within it. Surrounding these fields is a belt of cortex in which units are generally less responsive to acoustic stimulation and the frequency organization is more complex than in AI or R. Electrophysiological and cytoarchitectonic evidence suggest that this belt is composed of at least three and possibly four separate auditory fields.

Acoustic Stimulation↗