midterm Flashcards
tinnitus
a phantom auditory perception ; the perception of a sound without corresponding acoustic or mechanical correlates in the cochlea
-involuntary
-the site of generation is anywhere on the pathways of sound
breakdown of tinnitus models
neurophysiological (jasterboff) and psychological/cognitive (hallam and cognitive behavior models)
neurophysiological models
biological basis of tinnitus in the auditory system
-the consensus that tinnitus results from the perception of abnormal activity
-main model is jasterboff’s model
what are the three proposed mechanisms for how tinnitus is coded in the cortex
increased spontaneous activity fed by increased or decreased activity, cross fibers correlation with normal or increased spontaneous activity and more fibers with similar best frequency following HL induced plasticity
how does maladaptive plasticity correlate to tinnitus
tinnitus is thought to result from the CNS in response to HL or other causes so what happens is that the CNS is trying to fix something but it ended up becoming worse
explain how HL can impact tinnitus
HL will cause a decreased input to the auditory system, the brain them tries to maintain homeostasis by compensating however the increased neural gain causes more spontaneous neural activity
-therefore it is believed that increased spontaneous activity is proposed as a key mechanisms for tinnitus perception
central gain
a compensatory increase in central auditory activity as a response to the loss of sensory input
-a limitation to believing that central gain plays a role in tinnitus is that it requires everyone to have HL, but not everyone that has tinnitus has a HL
jasterboff’s neurophysiological model
focuses on how the auditory and non-auditory systems interact as well as it is based on general neurophysiology and behavioral neuroscience
-hypothesis is that many systems in the brain are involved in tinnitus, with the auditory system playing a secondary role
the main idea of jasterboff’s model
tinnitus should not simply be categorized into peripheral and central, meaning all levels are involved but it varies between cases
what does jasterboff’s model suggest
tinnitus becomes problematic when negative associations are formed with the tinnitus perception
-remember the concept of the tiger in the room, by perceiving it as negative or dangerous it becomes worse
what is involved in jasterboff’s model
limbic system (emotional responses), sympathetic autonomic nervous system (fight or flight) and the reticular foramen (attention and awareness)
jasterboff’s model suggests that tinnitus is not just a ______________ but there is also a ____________
sensory experience ; emotional and cognitive components
what are limitations of the neurophysiological models
it is experimental evidence, the models can explain how HL could lead to tinnitus but not how everyone with HL gets tinnitus, it cannot explain observations of patients that tinnitus was resolved after the nerve was cut
psychological/cognitive models of tinnitus
revolves around looking at how tinnitus disrupts the quality of life as well as the characteristics of tinnitus
-main models include hallam’s and the cognitive behavioral model
what domains can tinnitus impact
function impairments (thoughts/emotions, hearing, sleep and concentration) and activity limitations (socialization, physical health, work, education and economic)
common symptoms that are associated with impacting the quality of life due to tinnitus
insomnia, loss of concentration, low mood/irritability, anxiety and clinical depression
explain the vicious cycle of tinnitus
tinnitus can trigger anxiety which reinforces the tinnitus perception, creating a feedback loop leading to an increased emotional distress
-it’s the loop of negative emotional distress and increasing tinnitus that continues to go around and around
tinnitus perception vs. tinnitus reaction
perception is the characteristics of the tinnitus sound itself whereas reaction is the impact of tinnitus on an individual
hallam’s model
the thought that tinnitus might occur without auditory dysfunction and is potentially triggered by psychological factors
-hypothesis is that tinnitus is influenced by the ability of the CNS to inhibit unnecessary sensory input
the main idea of hallam’s model
bothersome tinnitus is the result of the failure to habituate, which is the decrease in response to a stimulus when it is presented repeatedly
-remember, habituation is believed to be a learning process where the brain will begin to associate with the constant presence of tinnitus as a non-threatening stimulus
evidence that supports hallam’s model
majority of people who have tinnitus do not complain about it, distress from tinnitus tends to decrease over time, no relationship between tinnitus loudness and distress levels and individuals often grow more tolerant of tinnitus
what are some factors that could lead to the inability to habituate
high levels of arousal, sudden onset of tinnitus, emotional significance, neural pathway damage and dishabituation
what causes dishabituation
changes or shifts in a persons mental state that can lead to re-awareness of the tinnitus
-some sort of change
-once this has occurred, habituation will have to occur all over again
treatment for hallam’s model
relaxation therapy (aims to lower autonomic arousal and interrupt the feedback loop) and formal cognitive therapy (alters emotional responses to tinnitus, reducing perceived distress and aiding habituation)
cognitive behavioral model of tinnitus (McKenna et. al, 2014)
focuses on how the individual thinks about their tinnitus
-believes that the cognitive interpretations are the primary driver of the stress associated with tinnitus
explanation of the cognitive behavioral model
negative interpretations of tinnitus increase the selective attention which then leads to greater awareness of tinnitus
-due to the increased attention, the person notices the tinnitus more often which then creates a cycle that reinforces the negative interpretations
under the cognitive model, how do people try and help their tinnitus
safety seeking behaviors such as avoidance or suppression (may provide short term relief but prevents long term adaptation) and selective attention (can distort how the tinnitus is perceived)
how does the cognitive behavioral model differ from other models
-greater emphasis is placed on vigilance and orientation to tinnitus rather than a failure to habituate
-emphasizes the impact of negative thoughts and cognitive distortions on tinnitus distress
what model is the foundation for cognitive behavioral therapy (CBT)
McKenna et. al cognitive behavioral model
-aims at breaking the cycle of distress through therapeutic techniques
implications of management with the psychological and cognitive tinnitus models
correcting negative automatic thoughts, reducing sympathetic autonomic nervous activity, reducing selective attention/monitoring for tinnitus related cues, correcting distorted perceptions of tinnitus intensity and its impact on functioning and correcting inaccurate beliefs
the historically viewed origin of tinnitus and why it is being challenged
tinnitus has been thought to occur as a result of dysfunction of the peripheral auditory system however it has been challenged due to the main point that when the auditory nerve is severed, this does not eliminate the tinnitus in every case
-the thought behind the nerve being severed is that if the connection is broken then the tinnitus will not be heard
the favored site of origin for tinnitus
central origin, meaning that the tinnitus perception is a brain issue
-there is some underlying causes that begins tinnitus, but ultimately its the brains reaction to some change
peripheral mechanisms associated with tinnitus
tinnitus associated with the cochlea
-cellular mechanisms, edge theory, discordant damage of hair cells, tectorial membrane displacement, NTs and their receptors, transduction in the organ of corti and cochlear synaptopathy
peripheral cellular mechanisms
loss of OHC electromotility, loss of synapse between IHCs and spiral ganglion neurons, damage to stereocilia bundle, rupture of the basilar membrane and death of the hair cells
-remember if there is any damage it will lead to HL which eventually will cause tinnitus
edge theory (contrast theory)
tinnitus is induced by increased spontaneous activity in the edge areas
-the edge area is the area of transition from normal OHCs on the apical side of a lesion to OHCs toward the basal side that are missing or being altered
-there is spontaneous activity at this area
discordant damage of the IHCs and OHCs
noise and ototoxicity → imbalance of cilia damage (hair cell loss) → nerve fiber imbalance → altered higher brian centers → tinnitus
-with any damage there can be an imbalance between the OHCs and IHCs due to the IHCs resilience to damage, so the OHCs will continue to become more damaged
-this imbalance will then be carried into the brain causing an already messy signal to be perceived, which is the tinnitus
tectorial membrane displacement
this membrane should be above the hair cells however any changes in the position could potentially trigger tinnitus to occur
-the change in location could occur after intense noise exposure
how can the tectorial membrane be displaced
the membrane may dip down onto the IHCs causing depolarization and an increased cochlear activity, contributing to the tinnitus perception by sending it to the brain
what are the primary NTs within the auditory system
glutamate and GABA
what receptors mediate the NTs
AMPA and NMDA receptors
what should occur within the organ of corti for the transduction
sound wave moving in will move the endolymphatic fluid, hair cells tip, potassium flows into the cell, calcium flows outward and pushes the NTs into the receptors
-in order for NTs to be dumped, calcium channels open
-once it has been released and have become bonded, it then becomes recycled through reuptake and at the same time the Ca will then leave the cell
-the cell is then depolarized
AMPA receptor process with tinnitus (associated with damage)
noise exposure (or some sort of damage) →excessive glutamate release by the IHCs → AMPA receptor overactivation (because glutamate is binding, more work for the receptors) → excessive calcium influx → nerve cell damage → disrupted auditory signal transmission → tinnitus perception