1
|
Spilka MJ, Raugh IM, Berglund AM, Visser KF, Strauss GP. Reinforcement learning profiles and negative symptoms across chronic and clinical high-risk phases of psychotic illness. Eur Arch Psychiatry Clin Neurosci 2023; 273:1747-1760. [PMID: 36477406 DOI: 10.1007/s00406-022-01528-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 11/21/2022] [Indexed: 12/12/2022]
Abstract
Negative symptoms are prominent in individuals with schizophrenia (SZ) and youth at clinical high-risk for psychosis (CHR). In SZ, negative symptoms are linked to reinforcement learning (RL) dysfunction; however, previous research suggests implicit RL remains intact. It is unknown whether implicit RL is preserved in the CHR phase where negative symptom mechanisms are unclear, knowledge of which may assist in developing early identification and prevention methods. Participants from two studies completed an implicit RL task: Study 1 included 53 SZ individuals and 54 healthy controls (HC); Study 2 included 26 CHR youth and 23 HCs. Bias trajectories reflecting implicit RL were compared between groups and correlations with negative symptoms were examined. Cluster analysis investigated RL profiles across the combined samples. Implicit RL was comparable between HC and their corresponding SZ and CHR groups. However, cluster analysis was able to parse performance heterogeneity across diagnostic boundaries into two distinct RL profiles: a Positive/Early Learning cluster (65% of participants) with positive bias scores increasing from the first to second task block, and a Negative/Late Learning cluster (35% of participants) with negative bias scores increasing from the second to third block. Clusters did not differ in the proportion of CHR vs. SZ cases; however, the Negative/Late Learning cluster had more severe negative symptoms. Although implicit RL is intact in CHR similar to SZ, distinct implicit RL phenotypic profiles with elevated negative symptoms were identified trans-phasically, suggesting distinct reward-processing mechanisms can contribute to negative symptoms independent of phases of illness.
Collapse
Affiliation(s)
- Michael J Spilka
- Department of Psychology, University of Georgia, Athens, GA, 30602, USA
| | - Ian M Raugh
- Department of Psychology, University of Georgia, Athens, GA, 30602, USA
| | - Alysia M Berglund
- Department of Psychology, University of Georgia, Athens, GA, 30602, USA
| | - Katherine F Visser
- Department of Psychiatry and Human Behavior, Brown University, Providence, RI, USA
| | - Gregory P Strauss
- Department of Psychology, University of Georgia, Athens, GA, 30602, USA.
| |
Collapse
|
2
|
Ayawvi G, Berglund AM, James SH, Luther L, Walker EF, Mittal VA, Strauss GP. The association between early traumatic experiences and the five domains of negative symptoms in participants at clinical high risk for psychosis. Early Interv Psychiatry 2023; 17:1131-1135. [PMID: 37041742 PMCID: PMC10564962 DOI: 10.1111/eip.13418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 02/02/2023] [Accepted: 03/28/2023] [Indexed: 04/13/2023]
Abstract
AIM Youth at clinical high risk (CHR) for psychosis have high rates of early life trauma, but it is unclear how trauma exposure impacts later negative symptom severity in CHR. The current study examined the association between early childhood trauma and the five domains of negative symptoms (anhedonia, avolition, asociality, blunted affect, alogia). METHOD Eighty nine participants completed interviewer-rated measures of childhood trauma and abuse experienced before age 16, psychosis risk, and negative symptoms. RESULTS Higher global negative symptom severity was associated with greater exposure to childhood psychological bullying, physical bullying, emotional neglect, psychological abuse, and physical abuse. Greater severity of avolition and asociality was associated with physical bullying. Greater severity of avolition was associated with emotional neglect. CONCLUSION Early adversity and childhood trauma is associated with negative symptoms during adolescence and early adulthood among participants at CHR for psychosis.
Collapse
Affiliation(s)
- Gifty Ayawvi
- Department of Psychology, University of Georgia, Athens, GA, USA
| | | | - Sydney H. James
- Department of Psychology, University of Georgia, Athens, GA, USA
| | - Lauren Luther
- Department of Psychology, University of Georgia, Athens, GA, USA
| | | | | | | |
Collapse
|
3
|
Strauss GP, Walker EF, Pelletier-Baldelli A, Carter NT, Ellman LM, Schiffman J, Luther L, James SH, Berglund AM, Gupta T, Ristanovic I, Mittal VA. Development and Validation of the Negative Symptom Inventory-Psychosis Risk. Schizophr Bull 2023; 49:1205-1216. [PMID: 37186040 PMCID: PMC10483448 DOI: 10.1093/schbul/sbad038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
BACKGROUND AND HYPOTHESES Early identification and prevention of psychosis is limited by the availability of tools designed to assess negative symptoms in those at clinical high-risk for psychosis (CHR). To address this critical need, a multi-site study was established to develop and validate a clinical rating scale designed specifically for individuals at CHR: The Negative Symptom Inventory-Psychosis Risk (NSI-PR). STUDY DESIGN The measure was developed according to guidelines recommended by the NIMH Consensus Conference on Negative Symptoms using a transparent, iterative, and data-driven process. A 16-item version of the NSI-PR was designed to have an overly inclusive set of items and lengthier interview to support the ultimate intention of creating a new briefer measure. Psychometric properties of the 16-item NSI-PR were evaluated in a sample of 218 CHR participants. STUDY RESULTS Item-level analyses indicated that men had higher scores than women. Reliability analyses supported internal consistency, inter-rater agreement, and temporal stability. Associations with measures of negative symptoms and functioning supported convergent validity. Small correlations with positive, disorganized, and general symptoms supported discriminant validity. Structural analyses indicated a 5-factor structure (anhedonia, avolition, asociality, alogia, and blunted affect). Item response theory identified items for removal and indicated that the anchor range could be reduced. Factor loadings, item-level correlations, item-total correlations, and skew further supported removal of certain items. CONCLUSIONS These findings support the psychometric properties of the NSI-PR and guided the creation of a new 11-item NSI-PR that will be validated in the next phase of this multi-site scale development project.
Collapse
Affiliation(s)
| | - Elaine F Walker
- Department of Psychology, Emory University, Atlanta, GA, USA
| | | | - Nathan T Carter
- Department of Psychology, Michigan State University, East Lansing, MI, USA
| | - Lauren M Ellman
- Department of Psychology and Neuroscience, Temple University, Philadelphia, PA, USA
| | - Jason Schiffman
- Department of Psychological Science, University of California- Irvine, Irvine, CA, USA
| | - Lauren Luther
- Department of Psychology, University of Georgia, Athens, GA, USA
| | - Sydney H James
- Department of Psychology, University of Georgia, Athens, GA, USA
| | | | - Tina Gupta
- Department of Psychology, Northwestern University, Evanston, IL, USA
| | - Ivanka Ristanovic
- Department of Psychology, Northwestern University, Evanston, IL, USA
| | - Vijay A Mittal
- Department of Psychology, Northwestern University, Evanston, IL, USA
| |
Collapse
|
4
|
Berglund AM, Raugh IM, Macdonald KI, James SH, Bartolomeo LA, Knippenberg AR, Strauss GP. The effects of the COVID-19 pandemic on hallucinations and delusions in youth at clinical high-risk for psychosis and outpatients with schizophrenia. Eur Arch Psychiatry Clin Neurosci 2023; 273:1329-1338. [PMID: 36680609 PMCID: PMC9862234 DOI: 10.1007/s00406-023-01551-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 01/09/2023] [Indexed: 01/22/2023]
Abstract
Although the COVID-19 pandemic has had detrimental effects on mental health in the general population, the impact on those with schizophrenia-spectrum disorders has received relatively little attention. Assessing pandemic-related changes in positive symptoms is particularly critical to inform treatment protocols and determine whether fluctuations in hallucinations and delusions are related to telehealth utilization and treatment adherence. In the current longitudinal study, we evaluated changes in the frequency of hallucinations and delusions and distress resulting from them across three-time points. Participants included: (1) outpatients with chronic schizophrenia (SZ: n = 32) and healthy controls (CN: n = 31); (2) individuals at clinically high risk for psychosis (CHR: n = 25) and CN (n = 30). A series of questionnaires were administered to assess hallucination and delusion severity, medication adherence, telehealth utilization, and protective factors during the pandemic. While there were no significant increases in the frequency of hallucinations and delusions in SZ and CHR, distress increased from pre-pandemic to early pandemic in both groups and then decreased at the third time point. Additionally, changes in positive symptom severity in SZ were related to psychiatric medication adherence. Findings suggest that positive symptoms are a critical treatment target during the pandemic and that ongoing medication services will be beneficial.
Collapse
Affiliation(s)
- Alysia M Berglund
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Ian M Raugh
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Kelsey I Macdonald
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Sydney H James
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Lisa A Bartolomeo
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Anna R Knippenberg
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA
| | - Gregory P Strauss
- Department of Psychology, University of Georgia, 125 Baldwin St., Athens, GA, 30602, USA.
| |
Collapse
|
5
|
Berglund AM, James SH, Raugh IM, Strauss GP. Beliefs About the Uncontrollability and Usefulness of Emotion in the Schizophrenia-Spectrum: Links to Emotion Regulation and Negative Symptoms. Cognit Ther Res 2023; 47:282-294. [PMID: 36779179 PMCID: PMC9894745 DOI: 10.1007/s10608-023-10357-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2023] [Indexed: 02/05/2023]
Abstract
Background Beliefs about the usefulness and controllability of emotions are associated with emotion regulation and psychological distress in the general population. Although individuals with schizophrenia-spectrum disorders evidence emotion regulation abnormalities, it is unclear whether emotional beliefs contribute to these difficulties and their associated poor clinical outcomes. Methods Participants included 72 individuals with schizophrenia-spectrum diagnoses (outpatients with schizophrenia n = 38; youth at clinical high-risk for psychosis, n = 34) and healthy controls (CN: n = 61) who completed the Emotional Beliefs Questionnaire, Emotion Regulation Questionnaire, and measures of clinical symptom severity. Results Those with schizophrenia-spectrum diagnoses reported believing that emotions were less controllable than CN; however, groups did not differ regarding beliefs about the usefulness of emotion. Greater beliefs of the uncontrollability of emotion were associated with greater use of suppression, less use of reappraisal, and increased negative symptoms. Emotion regulation partially mediated the association between emotional beliefs and negative symptoms. Conclusions Individuals in the schizophrenia-spectrum display superordinate beliefs that emotions are uncontrollable. These beliefs may influence emotion regulation strategy selection and success, which contributes to negative symptoms. Findings suggest that beliefs of emotional uncontrollability reflect a novel process related to both emotion regulation and negative symptoms that could be targeted in psychosocial treatments. Supplementary Information The online version contains supplementary material available at 10.1007/s10608-023-10357-w.
Collapse
Affiliation(s)
- Alysia M. Berglund
- Department of Psychology, University of Georgia, 125 Baldwin St, Athens, GA USA
| | - Sydney H. James
- Department of Psychology, University of Georgia, 125 Baldwin St, Athens, GA USA
| | - Ian M. Raugh
- Department of Psychology, University of Georgia, 125 Baldwin St, Athens, GA USA
| | - Gregory P. Strauss
- Department of Psychology, University of Georgia, 125 Baldwin St, Athens, GA USA
| |
Collapse
|
6
|
Macdonald KI, Spilka MJ, Bartolomeo LA, Raugh IM, Berglund AM, Strauss GP. Adherence to recommended health and social distancing precautions during the COVID-19 pandemic in individuals with schizophrenia and youth at clinical high-risk for psychosis. Schizophr Res 2022; 243:446-448. [PMID: 34334286 PMCID: PMC8321773 DOI: 10.1016/j.schres.2021.07.030] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 11/23/2022]
Affiliation(s)
| | | | | | | | | | - Gregory P. Strauss
- Corresponding author at: University of Georgia, Department of Psychology, 125 Baldwin St., Athens, GA 30602, USA
| |
Collapse
|
7
|
Klaunig MJ, Trask CL, Neis AM, Cohn JR, Chen X, Berglund AM, Cicero DC. Associations among domains of self-disturbance in schizophrenia. Psychiatry Res 2018; 267:187-194. [PMID: 29913377 DOI: 10.1016/j.psychres.2018.05.082] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 05/09/2018] [Accepted: 05/29/2018] [Indexed: 11/19/2022]
Abstract
Self-disturbances are increasingly recognized as important, possibly even central, features of schizophrenia. However, little is known about the associations among different manifestations of self-disturbances. The aims of the current study were threefold. We aimed to (1) replicate previous findings of increased self-disturbances in schizophrenia, (2) correlate manifestations of self-disturbances in schizophrenia across three domains, and (3) correlate self-disturbances with five symptoms domains of schizophrenia, including positive, negative, disorganized symptoms, excitement, and emotional distress. We examined three domains of self-experience, including somatosensation, anomalous self-experiences, and self-concept clarity. Participants included 48 individuals with schizophrenia and 36 non-psychiatric controls. The results of this study replicate previous findings of significantly higher levels of self-disturbances in people with schizophrenia. The results also indicate positive correlations between the domains of anomalous self-experiences and self-concept clarity, but not somatosensation, in individuals with schizophrenia. As well, anomalous self-experiences were positively correlated with positive symptoms, disorganized symptoms, and emotional distress and self-concept clarity was negatively correlated with disorganized symptoms and emotional distress.
Collapse
Affiliation(s)
- Mallory J Klaunig
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Christi L Trask
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Aaron M Neis
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Jonathan R Cohn
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Xuefang Chen
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - Alysia M Berglund
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA
| | - David C Cicero
- Department of Psychology, University of Hawaii at Manoa, Honolulu, HI, USA.
| |
Collapse
|
8
|
Abstract
This study investigates the ultrastructure and central targets in the cochlear nucleus of axonal swellings of type II primary afferent neurons. Type II axons comprise only 5-10% of the axons of the auditory nerve of mammals, but they alone provide the afferent innervation of the outer hair cells. In this study, type II axons were labeled with horseradish peroxidase, and serial-section electron microscopy was used to examine their swellings in: (1) the granule-cell lamina at its boundary with posteroventral cochlear nucleus, (2) the rostral anteroventral cochlear nucleus, and (3) the auditory nerve root. Only some (18%) of the type II terminal and en-passant swellings formed synapses. The synapses were asymmetric and contained clear round synaptic vesicles, suggesting that they are excitatory. Type II synapses were compared to those from type I fibers providing the afferent innervation of the inner hair cells. Type II synapses tended to have slightly smaller and fewer synaptic vesicles, had a greater proportion of the membrane apposition accompanied by a postsynaptic density, and often had densities that were discontinuous or 'perforated'. In all cochlear nucleus regions examined, the postsynaptic targets of type II synapses had characteristics of dendrites; in most cases these dendrites could not be traced to their cell bodies of origin. Some evidence suggests, however, that targets may include granule cells, spherical cells, and other cells in the nerve root. These results suggest afferent information from outer hair cells reaches diverse regions and targets within the cochlear nucleus.
Collapse
MESH Headings
- Animals
- Axons
- Cochlea/innervation
- Cochlear Nucleus/cytology
- Cochlear Nucleus/physiology
- Cochlear Nucleus/ultrastructure
- Hair Cells, Auditory, Outer/cytology
- Hair Cells, Auditory, Outer/physiology
- Hair Cells, Auditory, Outer/ultrastructure
- Horseradish Peroxidase/chemistry
- Mice
- Microscopy, Electron
- Nerve Fibers/physiology
- Nerve Fibers/ultrastructure
- Neurons, Afferent/cytology
- Neurons, Afferent/physiology
- Neurons, Afferent/ultrastructure
- Synapses/physiology
- Vestibulocochlear Nerve/physiology
Collapse
Affiliation(s)
- A M Berglund
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston 02114, USA
| | | | | |
Collapse
|
9
|
Abstract
Axons of olivocochlear neurons originate in the superior olivary complex and project to the cochlea. Along their course, medial olivocochlear axons give off branches to the cochlear nucleus. We labeled these branches with horseradish peroxidase and used electron microscopy to determine their target dendrites. Target dendrites were of two classes: "large" dendrites and "varicose" dendrites. Using serial sections, we reconstructed the dendrites and, in addition to the labeled olivocochlear input, we determined the synaptic profile of unlabeled inputs onto the dendrites. We classified the terminals on the basis of the shape and size of their synaptic vesicles. On large dendrites, the predominant type of unlabeled terminal had small round (SmRnd) vesicles. These terminals are likely to be excitatory, and some of them may originate from unlabeled medial olivocochlear branches. On varicose dendrites, the predominant type of terminal had pleomorphic vesicles. These terminals are likely to be inhibitory. They may be from descending inputs that arise in higher centers. A final type of terminal onto large dendrites exhibited signs of neuronal degeneration, possibly because the cell body of origin was damaged during the injection procedure. These terminals often had long, perforated synaptic densities and may originate from type II primary afferents. Thus, medial olivocochlear efferents and type II afferents, which both contact outer hair cells in the periphery, appear to synapse onto the same targets in the cochlear nucleus. In contrast, where examined, the target dendrites did not receive terminals with large vesicles from afferents that contact inner hair cells. Thus, target neurons appear to function in a neural circuit associated more closely with outer than with inner hair cells.
Collapse
Affiliation(s)
- T E Benson
- Department of Biomedical Engineering, Boston University, Massachusetts 02215, USA
| | | | | |
Collapse
|
10
|
Abstract
Type II spiral ganglion cells provide the afferent pathway from outer hair cells in the mammalian cochlea to neurons in the cochlear nucleus. The present study compares the projection patterns of type II fibers originating from spiral ganglion cells of apical, middle and basal cochlear regions in mice. Fibers were labeled by extracellular injections of horseradish peroxidase into the spiral ganglion. Type II fibers from all regions displayed many 'en passant' swellings (mean = 95) and had very few terminal swellings (mean = 6); fibers from the base had significantly more swellings than those from the apex. Type II fibers traveled into the cochlear nucleus together with type I fibers labeled by the same injection, and both types bifurcated in a cochleotopic manner. The bifurcations formed ascending and descending branches that traveled initially with type I branches in the magnocellular regions of the cochlear nucleus. Type II fibers differed from type I branches in that many fibers subsequently distributed collaterals and terminals to granule cell regions and to the boundaries of these regions that typically do not receive type I input. This projection into the granule cell regions depended on cochlear origin: ascending branches of type II fibers from the cochlea apex did not usually terminate in granule cell regions, whereas those from the base often ended in these regions. Descending branches of type II fibers from all regions, however, projected to the granule cell regions, particularly the granule cell lamina between ventral and dorsal cochlear nucleus. These observations suggest that afferent information from outer hair cells reaches a wide area of the magnocellular parts of the cochlear nucleus in a cochleotopic fashion, and reaches granule cell regions with a less distinct cochleotopic mapping.
Collapse
Affiliation(s)
- A M Berglund
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston 02114
| | | |
Collapse
|
11
|
Abstract
The spiral ganglia of the cat, gerbil, mouse, rat, and human were immunohistochemically stained with various monoclonal neurofilament antibodies. Three antibodies to the 200-kD neurofilament protein (R-3, Dräger et al., '84; ICN anti-200, clone NE14, Debus et al., '83; RT-97, Wood and Anderton, '81) labeled the somata of type II spiral ganglion neurons but not those of type I ganglion neurons. In the extreme base of the cochlea of cats, mice and rats, there was intense labeling of a few (less than 0.5% of the total ganglion population) large neurons resembling type I ganglion neurons. Several other neurofilament antibodies (Amersham anti-68, Amersham and ICN anti-160, and SMI-32) did not specifically label type II ganglion neurons but instead labeled all neurons of the spiral ganglion. These two patterns of labeling prompted us to investigate the cause for this difference. Because antibodies against the 200-kD neurofilament protein preferentially labeled type II neurons and because 200-kD neurofilament is highly phosphorylated, we treated cochlear tissue with alkaline phosphatase in order to remove phosphate groups. This treatment eliminated the intense labeling of type II neurons with R-3, ICN anti-200, and RT-97, but had no effect on the intense labeling of ganglion cell bodies observed with the other neurofilament antibodies tested. This evidence suggests that labeling occurs because of the cytoplasmic presence of phosphorylated 200-kD neurofilament protein in type II ganglion neurons. Populations of neurons may thus differ in their neurofilament epitopes and monoclonal antibodies can be used to mark such differences.
Collapse
Affiliation(s)
- A M Berglund
- Department of Anatomy and Cellular Biology, Harvard Medical School, Boston 02115
| | | |
Collapse
|
12
|
Abstract
Olivocochlear neurons have somata in the superior olivary complex and provide an efferent innervation to the cochlea. One subgroup of olivocochlear neurons, medial olivocochlear neurons, sends fibers to innervate the cochlear outer hair cells. En route to the cochlea, medial olivocochlear fibers give off branches to the ventral cochlear nucleus, the first auditory center of the brain. This study examines the cochlear-nucleus branches of medial olivocochlear fibers, comparing those from fibers that innervate the cochlear base with those from fibers that innervate the cochlear apex. Basal fibers give off dorsal branches to the granule cell lamina and ventral branches to the auditory nerve root. Apical fibers give off few dorsal branches but many ventral branches that terminate rostrally to the nerve root. This cochleotopic mapping of medial olivocochlear branches corresponds in a general way to that of afferent fibers. Unlike afferent fibers, however, the branches terminate primarily along the edges of the cochlear nucleus. In the mouse, the particular edges of termination are (1) the medial border of the ventral cochlear nucleus where it meets the underlying vestibular nerve root, and (2) the border between the ventral cochlear nucleus and the granule cell lamina. Neurons and dendrites of these border regions may thus integrate efferent and afferent information in a frequency-specific manner.
Collapse
Affiliation(s)
- M C Brown
- Department of Physiology, Harvard Medical School, Boston 02115
| | | | | |
Collapse
|
13
|
Abstract
Previous attempts to trace the central pathways of the thin axons from type II spiral ganglion neurons have been hampered by technical difficulties such as fading of the reaction product as distance increases from the injection site (Ryugo et al.: Soc. Neurosci. Abstr. 12:779, '86; Brown: J. Comp. Neurol. 260:591-604, '87). By using small rodents (gerbils and mice), which have short auditory nerves, we have succeeded in filling the entire central axon and terminals of type II neurons after peripheral injections of horseradish peroxidase. The general course of the type II fibers within the auditory nerve and cochlear nucleus is similar to that of type I fibers except that terminals from type II neurons are often found in regions of the cochlear nucleus that have high densities of granule cells.
Collapse
Affiliation(s)
- M C Brown
- Department of Physiology, Harvard Medical School, Boston, Massachusetts 02115
| | | | | | | |
Collapse
|
14
|
Abstract
Horseradish peroxidase (HRP) was injected extracellularly into the auditory nerve of adult mice so that the enzyme could infuse individual spiral ganglion neurons. Forty-two well-stained neurons were reconstructed through serial sections from their cell bodies to peripheral terminations in the organ of Corti with the aid of a light microscope and drawing tube. No neuron was observed to innervate both inner and outer hair cells (IHCs and OHCs). Previous observations from neonatal mammals that reported that IHCs and OHCs were innervated by the same neuron are thus presumed to describe a transient developmental phenomenon. Two populations of spiral ganglion neurons were determined on the basis of the differences in receptor innervation. The type I neurons innervated exclusively IHCs by way of thick (1-2 microns) radial fibers, whereas the type II neurons innervated only OHCs by way of thin (approximately 0.5 micron) outer spiral fibers. Certain features of the peripheral process in the vicinity of the cell body were highly correlated with fiber type. This pattern of separate innervation of IHCs and OHCs by type I and type II neurons, respectively, may represent the general plan of afferent organization for the adult mammalian cochlea.
Collapse
|
15
|
Abstract
Tissue from mature rat and cat cochleas was stained with basic dyes in order to distinguish between the cell bodies of type I and II spiral ganglion neurons. This same tissue was then stained with protargol, or processed immunocytochemically using a monoclonal neurofilament antibody, RT-97. Type II neurons were intensely stained, whereas type I neurons were not. We conclude that type II neurons can be clearly distinguished by their abundant neurofilament content.
Collapse
|