Diana Peterson | Iowa State University (original) (raw)

Papers by Diana Peterson

Peterson DC, Nataraj K, Wenstrup J. Glycinergic inhibition creates a form of auditory spectral in... more Peterson DC, Nataraj K, Wenstrup J. Glycinergic inhibition creates a form of auditory spectral integration in nuclei of the lateral lemniscus. For analyses of complex sounds, many neurons integrate information across different spectral elements via suppressive effects that are distant from the neurons' excitatory tuning. In the mustached bat, suppression evoked by sounds within the first sonar harmonic (23-30 kHz) or in the subsonar band (Ͻ23 kHz) alters responsiveness to the higher best frequencies of many neurons. This study examined features and mechanisms associated with low-frequency (LF) suppression among neurons of the lateral lemniscal nuclei (NLL). We obtained extracellular recordings from neurons in the intermediate and ventral nuclei of the lateral lemniscus, observing different forms of LF suppression related to the two above-cited frequency bands. To understand the mechanisms underlying this suppression in NLL neurons, we examined the roles of glycinergic and GABAergic input through local microiontophoretic application of strychnine, an antagonist to glycine receptors (GlyRs), or bicuculline, an antagonist to ␥-aminobutyric acid type A receptors (GABA A Rs). With blockade of GABA A Rs, neurons showed an increase in firing rate to best frequency (BF) and/or LF tones but retained LF suppression of BF sounds. For neurons that displayed LF suppression tuned to 23-30 kHz, the suppression was eliminated or nearly eliminated by GlyR blockade. In contrast, GABA A R blockade did not eliminate nor had any consistent effect on suppression tuned to these frequencies. We conclude that LF suppression tuned in the 23-to 30-kHz range results from neuronal inhibition within the NLL via glycinergic inputs. For neurons displaying suppression tuned Ͻ23 kHz, neither GlyR nor GABAR blockade altered LF suppression. We conclude that such suppression originates at a lower auditory level, perhaps a result of cochlear mechanisms. These findings demonstrate that neuronal interactions within NLL create a particular form of LF suppression that contributes to the analysis of complex acoustic signals.

This study examined responsiveness to acoustic stimuli among neurons of the basolateral amygdala.... more This study examined responsiveness to acoustic stimuli among neurons of the basolateral amygdala. While recording from single neurons in awake mustached bats (Pteronotus parnellii), we presented a wide range of acoustic stimuli including tonal, noise, and vocal signals. While many neurons displayed phasic or sustained responses locked to effective auditory stimuli, the majority of neurons (n = 58) displayed a persistent excitatory discharge that lasted well beyond stimulus duration and filled the interval between successive stimuli. Persistent firing usually began seconds (median value, 5.4 s) after the initiation of a train of repeated stimuli and lasted, in the majority of neurons, for at least 2 min after the end of the stimulus train. Auditory-responsive amygdalar neurons were generally excited by one stimulus or very few stimuli. Most neurons did not respond well to synthetic stimuli including tones, noise bursts or frequency-modulated sweeps, but instead responded only to vocal stimuli (82 of 87 neurons). Furthermore, most neurons were highly selective among vocal stimuli. On average, neurons responded to 1.7 of 15 different syllables or syllable sequences. The largest percentage of neurons responded to a hiss-like rectangular broadband noise burst (rBNB) call associated with aggressive interactions. Responsiveness to effective vocal stimuli was reduced or eliminated when the spectrotemporal features of the stimuli were altered in a subset of neurons. Chemical activation of the medial geniculate body (MG) increased both background and evoked firing. Among 39 histologically localized recording sites, we saw no evidence of topographic organization in terms of temporal response pattern, habituation, or the affect of calls to which neurons responded. Overall, these studies demonstrate that amygdalar neurons in the mustached bat show high selectivity to vocal stimuli, and suggest that persistent firing may be an important feature of amygdalar responses to social vocalizations. Ó

Fluorescent retrograde tracers were used to identify the cells in auditory cortex that project di... more Fluorescent retrograde tracers were used to identify the cells in auditory cortex that project directly to the cochlear nucleus (CN). Following injection of a tracer into the CN, cells were labeled bilaterally in primary auditory cortex and the dorsocaudal auditory field as well as several surrounding fields. On both sides, the cells were limited to layer V. The size of labeled cell bodies varied considerably, suggesting that different cell types may project to the CN. Cells ranging from small to medium in size were present bilaterally, whereas the largest cells were labeled only ipsilaterally. In optimal cases, the extent of dendritic labeling was sufficient to identify the morphologic class. Many cells had an apical dendrite that could be traced to a terminal tuft in layer I. Such Btuftedp yramidal cells were identified both ipsilateral and contralateral to the injected CN. The results suggest that the direct pathway from auditory cortex to the cochlear nucleus is substantial and is likely to play a role in modulating the way the cochlear nucleus processes acoustic stimuli.

The inferior colliculus (IC) and superior olivary complex (SOC) are important sources of descendi... more The inferior colliculus (IC) and superior olivary complex (SOC) are important sources of descending pathways to the cochlear nucleus. The IC and SOC are also targets of direct projections from the auditory cortex but it is not known if cortical axons contact the cells that project to the cochlear nucleus. Multi-labeling techniques were used to address this question in guinea pigs. A fluorescent anterograde tracer was injected into temporal cortex to label corticofugal axons. Different fluorescent tracers were injected into one or both cochlear nuclei to label olivary and collicular cells. The brain was subsequently processed for fluorescence microscopy and the IC and SOC were examined for apparent contacts between cortical axons and retrogradely labeled cells. The results suggest that cortical axons contact cochlear nucleus-projecting cells in both IC and SOC. In both regions, contacts were more numerous on the side ipsilateral to the injected cortex. In the IC, the contacted cells projected ipsilaterally or contralaterally to the CN. In the SOC, the contacted cells projected ipsilaterally, contralaterally or bilaterally to the CN. We conclude that auditory cortex is in a position to modulate descending pathways from both the IC and SOC to the cochlear nucleus.

We used anterograde tracing techniques to examine projections from auditory cortex to the cochlea... more We used anterograde tracing techniques to examine projections from auditory cortex to the cochlear nucleus in guinea pigs. Following injection of dextrans into the temporal cortex, labeled axons were present bilaterally in the cochlear nucleus. The distribution of boutons within the cochlear nucleus was similar on the two sides. The majority of boutons was usually located on the ipsilateral side. Most of the boutons were located in the granule cell areas, where many small boutons and a few larger, mossy-type endings were labeled. Additional small, labeled boutons were found in all layers of the dorsal cochlear nucleus, with the majority located in the fusiform cell layer. Labeled boutons were also present in the ventral cochlear nucleus, where they were located in the small cell cap as well as magnocellular parts of both posteroventral and anteroventral cochlear nucleus. Similar results were obtained with injections restricted to primary auditory cortex or to the dorsocaudal auditory field. The results illustrate direct cortical projections to the cochlear nucleus that are likely to modulate the activity in a number of ascending auditory pathways.

Anterograde and retrograde tracing techniques were combined to determine whether auditory cortica... more Anterograde and retrograde tracing techniques were combined to determine whether auditory cortical axons contact cells in the cochlear nucleus that project to the inferior colliculus. FluoroRuby or Xuorescein dextran was injected into auditory cortex to label cortical axons by anterograde transport. DiVerent Xuorescent tracers (Fast Blue, FluoroGold, FluoroRuby or Xuorescein dextran) were injected into one or both inferior colliculi to label cells in the cochlear nucleus. After 12-15 days, the brain was processed for Xuorescence microscopy and the cochlear nuclei were examined for apparent contacts between cortical axons and retrogradely labeled cochlear nucleus cells. The results suggest that axons from the ipsilateral or contralateral cortex contact fusiform and giant cells in the dorsal cochlear nucleus and multipolar cells in the ventral cochlear nucleus that project directly to the inferior colliculus. The contacts occur on cell bodies and dendrites. The target cells in the cochlear nucleus include cells that project ipsilaterally, contralaterally or bilaterally to the inferior colliculus. The results suggest that auditory cortex is in a position to exert direct eVects on the monaural pathways that ascend from the cochlear nucleus.

Peterson DC, Voytenko S, Gans D, Galazyuk A, Wenstrup J. Intracellular recordings from combinatio... more Peterson DC, Voytenko S, Gans D, Galazyuk A, Wenstrup J. Intracellular recordings from combination-sensitive neurons in the inferior colliculus. . In vertebrate auditory systems, specialized combination-sensitive neurons analyze complex vocal signals by integrating information across multiple frequency bands. We studied combinationsensitive interactions in neurons of the inferior colliculus (IC) of awake mustached bats, using intracellular somatic recording with sharp electrodes. Facilitated combinatorial neurons are coincidence detectors, showing maximum facilitation when excitation from low-and high-frequency stimuli coincide. Previous work showed that facilitatory interactions originate in the IC, require both low and high frequency-tuned glycinergic inputs, and are independent of glutamatergic inputs. These results suggest that glycinergic inputs evoke facilitation through either postinhibitory rebound or direct depolarizing mechanisms. However, in 35 of 36 facilitated neurons, we observed no evidence of low frequency-evoked transient hyperpolarization or depolarization that was closely related to response facilitation. Furthermore, we observed no evidence of shunting inhibition that might conceal inhibitory inputs. Since these facilitatory interactions originate in IC neurons, the results suggest that inputs underlying facilitation are electrically segregated from the soma. We also recorded inhibitory combinatorial interactions, in which low frequency sounds suppress responses to higher frequency signals. In 43% of 118 neurons, we observed low frequency-evoked hyperpolarizations associated with combinatorial inhibition. For these neurons, we conclude that low frequency-tuned inhibitory inputs terminate on neurons primarily excited by high-frequency signals; these inhibitory inputs may create or enhance inhibitory combinatorial interactions. In the remainder of inhibited combinatorial neurons (57%), we observed no evidence of low frequency-evoked hyperpolarizations, consistent with observations that inhibitory combinatorial responses may originate in lateral lemniscal nuclei.

The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projectio... more The superior olivary complex (SOC) and inferior colliculus (IC) are targets of cortical projections as well as sources of major ascending auditory pathways. This study examines whether the cortical projections contact cells in the SOC or IC that project to higher levels. First, we placed an anterograde tracer into the auditory cortex to label cortico-olivary axons and a retrograde tracer into the IC to label olivocollicular cells in guinea pigs. Cortical axons contacted many labeled cells in the ipsilateral SOC and fewer labeled cells in the contralateral SOC. Contacted cells projected to the ipsilateral or contralateral IC.

This report examines temporal features of facilitation and suppression that underlie spectrally i... more This report examines temporal features of facilitation and suppression that underlie spectrally integrative responses to complex vocal signals. Auditory responses were recorded from 160 neurons in the inferior colliculus (IC) of awake mustached bats. Sixty-two neurons showed combination-sensitive facilitation: responses to best frequency (BF) signals were facilitated by well-timed signals at least an octave lower in frequency, in the range 16 -31 kHz. Temporal features and strength of facilitation were generally unaffected by changes in duration of facilitating signals from 4 to 31 ms. Changes in stimulus rise time from 0.5 to 5.0 ms had little effect on facilitatory strength. These results suggest that low frequency facilitating inputs to high BF neurons have phasic-on temporal patterns and are responsive to stimulus rise times over the tested range. We also recorded from 98 neurons showing low-frequency (11-32 kHz) suppression of higher BF responses. Effects of changing duration were related to the frequency of suppressive signals. Signals Ͻ23 kHz usually evoked suppression sustained throughout signal duration. This and other features of such suppression are consistent with a cochlear origin that results in masking of responses to higher, near-BF signal frequencies.

Rheumatic fever is an auto-immune disease caused by exposure to Streptococcus pyogenes. Over the ... more Rheumatic fever is an auto-immune disease caused by exposure to Streptococcus pyogenes. Over the last 50 years, reports of rheumatic fever within the United States have diminished. The decrease was attributed to the advent of penicillin in the treatment of streptococcus infections. We propose that current diagnostic and treatment methodologies may adversely increase the morbidity rate of rheumatic fever within the United States. Publication rates and interest in rheumatic fever has diminished over the last 30 years. Because of this decline, many physicians are only vaguely aware of the disorder. Additionally, the fear of antibiotic resistance has influenced the Center of Disease Control to suggest a significant decrease in the use of antibiotics by physicians. Although extremely valid for the future health and well-being of the population, such policies must be examined for each individual case carefully. The American Heart Association prescribes long-term antibiotic prophylaxis as the only current treatment; however literature reviews indicate that such therapy is rarely used. Therefore individuals diagnosed with rheumatic fever are not being treated. Additionally, because many physicians are not routinely testing for streptococcus or early signs of endocarditis, it is likely that cases of rheumatic fever will increase in the future, and many individuals may not be diagnosed until sever damage or morbidity occurs. Physician education and clear revised guide-lines are necessary to ensure adequate treatment of individuals with rheumatic fever. Mis-understandings of the disease and how it should be treated by first responders (i.e. primary care providers and pediatricians) are discussed.

Auditory cortex projects directly and bilaterally to the inferior colliculus (IC). We used multip... more Auditory cortex projects directly and bilaterally to the inferior colliculus (IC). We used multiple fluorescent retrograde tracers to determine whether individual cortical cells project to both the left and right IC. Injection of different tracers into each IC labeled many cells in a sheet that extended throughout much of temporal cortex in both hemispheres. Most cells contained a single tracer, with the majority of these labeled from the ipsilateral IC. Numerous double-labeled cells were observed throughout the same areas of temporal cortex. The doublelabeled cells form a small percentage of the cortical cells that project to the ipsilateral IC (6.1% on average) and a much larger percentage of the cells that project to the contralateral IC (46.4% on average). Unilaterally projecting cells are well positioned to have effects limited to one IC, whereas bilaterally projecting cells are likely to have a broader influence and may coordinate activity on the two sides of the midbrain. D

We used multiple-labeling techniques with retrograde fluorescent tracers to determine whether ind... more We used multiple-labeling techniques with retrograde fluorescent tracers to determine whether individual cells in the inferior colliculus project to the medial geniculate body (MG) and the cochlear nucleus (CN) in guinea pigs. Four possible projection patterns were examined: (1) to ipsilateral MG and ipsilateral CN; (2) to ipsilateral MG and contralateral CN; (3) to contralateral MG and ipsilateral CN; and, (4) to contralateral MG and contralateral CN. Following injections of different tracers into two or more sites, no inferior collicular cells were double-labeled from the two contralateral targets and only a few cells were double-labeled from each of the other pairs of targets. The double-labeled cells always totaled <1% of the single-labeled populations. We conclude that collateral projections from the inferior colliculus to the MG and CN are virtually non-existent. Therefore, the ascending and descending projections to these targets arise from different cells. These cells could potentially receive different inputs and send different information to higher or lower centers of the auditory pathway. (B.R. Schofield).